Change search
Refine search result
2345678 201 - 250 of 2233
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 201.
    Beaktas, Oguz
    et al.
    Warwick Manufacturing Group, University of Warwick, Coventry CV4 7AL, United Kingdom.
    Jones, Jeffrey A.
    Warwick Manufacturing Group, University of Warwick, Coventry CV4 7AL, United Kingdom.
    Sankararaman, Shankar
    PricewaterhouseCoopers, San Jose, CA 95110, United States.
    Roychoudhury, Indranil
    Stinger Ghaffarian Technologies, Inc., NASA Ames Research Center, Moffett Field, CA 94035, United States.
    Goebel, Kai
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics. NASA Ames Research Center, Moffett Field, CA 94035, United States.
    Reconstructing secondary test database from PHM08 challenge data set2018In: Article in journal (Refereed)
    Abstract [en]

    In this data article, a reconstructed database, which provides information from PHM08 challenge data set, is presented. The original turbofan engine data were from the Prognostic Center of Excellence (PCoE) of NASA Ames Research Center (Saxena and Goebel, 2008), and were simulated by the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS) (Saxena et al., 2008). The data set is further divided into "training", "test" and "final test" subsets. It is expected from collaborators to train their models using “training” data subset, evaluate the Remaining Useful Life (RUL) prediction performance on “test” subset and finally, apply the models to the “final test” subset for competition. However, the "final test" results can only be submitted once by email to PCoE. Before the results are sent for performance evaluation, in order to pre-validate the dataset with true RUL values, this data article introduces reconstructed secondary datasets derived from the noisy degradation patterns of original trajectories. Reconstructed database refers to data that were collected from the training trajectories. Fundamentally, it is formed of individual partial trajectories in which the RUL is known as a ground truth. Its use provides a robust validation of the model developed for the PHM08 data challenge that would otherwise be ambiguous due to the high-risk of one-time submission. These data and analyses support the research data article “A Neural Network Filtering Approach for Similarity-Based Remaining Useful Life Estimations” (Bektas et al., 2018).

  • 202.
    Bektas, Oguz
    et al.
    Warwick Manufacturing Group, University of Warwick, Coventry, UK.
    Jones, Jeffrey A.
    Warwick Manufacturing Group, University of Warwick, Coventry, UK.
    Sankararaman, Shankar
    Data Science and Analytics Manager,Pricewaterhouse Cooper, San Jose, USA.
    Roychoudhury, Indranil
    Stinger Ghaffarian Technologies, Inc.NASA Ames Research Center, Moffett Field, USA.
    Goebel, Kai
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics. NASA Ames Research Center, Moffett Field, USA.
    A neural network filtering approach for similarity-based remaining useful life estimation2018In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015Article in journal (Refereed)
    Abstract [en]

    The role of prognostics and health management is ever more prevalent with advanced techniques of estimation methods. However, data processing and remaining useful life prediction algorithms are often very different. Some difficulties in accurate prediction can be tackled by redefining raw data parameters into more meaningful and comprehensive health level indicators that will then provide performance information. Proper data processing has a significant importance on remaining useful life predictions, for example, to deal with data limitations or/and multi-regime operating conditions. The framework proposed in this paper considers a similarity-based prognostic algorithm that is fed by the use of data normalisation and filtering methods for operational trajectories of complex systems. This is combined with a data-driven prognostic technique based on feed-forward neural networks with multi-regime normalisation. In particular, the paper takes a close look at how pre-processing methods affect algorithm performance. The work presented herein shows a conceptual prognostic framework that overcomes challenges presented by short-term test datasets and that increases the prediction performance with regards to prognostic metrics.

  • 203. Benda, Sten
    EMC undersökning i Kiruna 2003-06-23--272004Report (Other academic)
    Abstract [sv]

    Många tågförseningar förorsakas av elektromagnetiska störningar t.ex. åsknedslag och signaler som slår om till rött av okänd anledning. Med detta som grund enades arbetsgrupp TURSAM (Tillämpat underhåll i samverkan) på rekommendation av Banverket Projektering Luleå kontoret, om att anlita EMCES Sten Benda att försöka identifiera bakomliggande orsak till dessa störningar. Sten Benda utförde tillsammans med Banverket Norra Banregionen, personal från EISLAB (LTU) underökningar och mätningar på anläggningar: Syfte var att hitta de bakomliggande orsakerna till elektromagnetiska störningar i järnvägsmiljö. Målsättning för den här undersökningen är att fastställa om elektromagnetiska störningar kan orsaka problem som kan påverka järnvägsdrift. Sten Bendas undersökning och rapport visar på ett antal allvarliga fel bl.a. Grundläggande fel i överordnade föreskrifter, missförstånd angående hur skärmning av elektromagnetiska fält skall utföras vilket medför att nya anläggningar byggs och monteras så att EMC-skyddet helt förstörs. Felaktig terminologi användes, bl a förväxlas begreppen låg-ohmig och låg-impediv. Stora dyra kurar (30 tkr/st) för skärmning perforeras med hål, med rätt installation kan billigare kurar (5 tkr/st) användas. Slutbesiktningen släpper igenom för många byggfel och dokumentationen i anläggningarna stämmer inte överens med verkligt montage. Elsäkerheten bevakas inte.

  • 204.
    Berg, Susanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Uppföljning efter PCB sanering: -En studie av kommuners uppföljande verksamhet efter PCB sanering i byggnad2017Independent thesis Basic level (university diploma), 5 credits / 7,5 HE creditsStudent thesis
  • 205.
    Berg, Sven
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jungmar, Ulf
    Bodycote Materials Testing AB, Linköping.
    Lundberg, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Vähäoja, Pekka
    Department of Mechanical Engineering, University of Oulu.
    Investigation of the measurement precision of oil analysis instruments, using fully formulated oils: Part 1: Spectroscopic instruments2011In: Industrial Lubrication and Tribology, ISSN 0036-8792, E-ISSN 1758-5775, Vol. 63, no 6, p. 404-411Article in journal (Refereed)
    Abstract [en]

    Purpose - The aim of this study is to determine the variation of the different oil analysis instruments in terms of standard deviation and CV-values, when measuring samples of fully formulated hydraulic and gear oils taken from working systems. Design/methodology/approach - In this investigation, two different spectrometric techniques, inductively coupled plasma-optical emission spectrometers (ICP-OES) and rotating disk electrode-optical emission spectrometers (RDE-OES), have been studied to determine the instruments' precision of measurement and ability to measure the absolute level of contamination. The study was based on a series of measurements using artificial contamination mixed with oil. Findings - The ICP has better precision of measurement of the two instruments, but cannot predict the absolute values of contamination when oil samples are only treated by organic solvent dilution if the samples include large or dense particles. It is therefore not too good, with the sample pre-treatment method used, at detecting wear processes that produce dense/large particles, such as pitting failure. For instance, microwave-assisted acid digestion could be used for sample pre-treating to obtain accurate results in that case. It should, however, be able to detect wear mechanisms that produce small particles such as abrasive wear in any case. The ICP has a repeatability value of r=3 percent and a reproducibility value of R=12 percent for contamination levels of between 50 and 400 ppm and r=0.6 and R=2 ppm, respectively, at values below 50 ppm. The RDE cannot predict the absolute value of contamination if this includes large or dense particles if proper sample pre-treatment is not used. It is therefore not good at detecting wear mechanisms that produces dense/large particles (if the oil samples are not pre-treated properly) such as pitting but should be able to detect abrasive wear and similar processes that produce small particles in any case. The RDE's precision of measurement is not as good as the ICP, with a reproducibility variation of R=r=25 percent for contamination levels between 20 and 500 ppm and R=r=6 ppm for contamination level below 20 ppm. Research limitations/implications - Only the effects from lubricating oils are studied. Practical implications - This study will significantly increase the industrial knowledge concerning measurement precision in particle contamination measurement systems. Originality/value - No similar study is found

  • 206.
    Berg, Sven
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jungmar, Ulf
    Bodycote Materials Testing AB, Linköping.
    Lundberg, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Vähäoja, Pekka
    Department of Mechanical Engineering, University of Oulu.
    Investigation of the measurement precision of oil analysis instruments, using fully formulated oils: Part 2: Contamination-measuring instruments2011In: Industrial Lubrication and Tribology, ISSN 0036-8792, E-ISSN 1758-5775, Vol. 63, no 6, p. 412-419Article in journal (Refereed)
    Abstract [en]

    Purpose - The aim of this study is to determine the variation of the different oil analysis instruments in terms of standard deviation and CV-values, when measuring samples of fully formulated hydraulic and gear oils taken from working systems. Design/methodology/approach - In this investigation two different spectrometric techniques, ICP-OES and RDE-OES, have been studied to determine the instruments' precision of measurement and ability to measure the absolute level of contamination. Findings - The ICP has better precision of measurement of the two instruments, but cannot predict the absolute values of contamination when oil samples are only treated by organic solvent dilution if the samples include large or dense particles. It is therefore not too good, with the sample pre-treatment method used, at detecting wear processes that produce dense/large particles, such as pitting failure. For instance, microwave-assisted acid digestion could be used for sample pre-treating to obtain accurate results in that case. It should, however, be able to detect wear mechanisms that produce small particles such as abrasive wear in any case: the ICP has a repeatability value of ITr/IT=3 per cent and a reproducibility value of ITR/IT=12 per cent for contamination levels of between 50-400 PPM and ITr/IT=0.6 PPM and ITR/IT=2 PPM, respectively, at values below 50 PPM; the RDE cannot predict the absolute value of contamination if this includes large or dense particles if proper sample pre-treatment is not used. It is therefore not good at detecting wear mechanisms that produce dense/large particles (if the oil samples are not pre-treated properly) such as pitting but should be able to detect abrasive wear and similar processes that produce small particles in any case; the RDE's precision of measurement is not as good as the ICP, with a reproducibility variation of ITR/IT=ITr/IT=25 per cent for contamination levels between 20-500 PPM and ITR/IT=ITr/IT=6 PPM for contamination level below 20 PPM. Research limitations/implications - Measuring only on fully formulated oils from hydraulic and gear systems. Practical implications - The study will be of significant support regarding industrial interpretation of measurement results from the most common oil particle measurement methods. Originality/value - No other similar studies are known

  • 207.
    Berg, Sven
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lundberg, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Rheological properties of contaminated oil2000In: Proceedings of the International Tribology Conference: ITC Nagasaki 2000 ; October 29 - November 2, 2000, Tokyo: Japan Society of Tribologists , 2000, p. 1239-1243Conference paper (Refereed)
  • 208.
    Berges, Luis
    et al.
    Department of Design Engineering and Manufacturing, University of Zaragoza.
    Galar, Diego
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Stenström, Christer
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Qualitative and quantitative aspects of maintenance performance measurement: a data fusion approach2013In: International Journal of Strategic Engineering Asset Management (IJSEAM), ISSN 1759-9733, E-ISSN 1759-9741, Vol. 1, no 3, p. 238-252Article in journal (Refereed)
    Abstract [en]

    The measurement of maintenance performance is often faced with a lack in knowledge about the real function of the maintenance department within organisations, and consequently appropriate targets from the global mission and vision are absence. Measurement metrics are not adapted to real needs, which have a strong human factor; nor is there a roadmap of the amount of data to be collected, their processing or how they are used in decision making. This article proposes a model where qualitative and quantitative methods are combined to complement the advantages of both.

  • 209.
    Berglund, Anders
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Tretten, Phillip
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Who wins from academic consulting2013In: Design Education-Growing Our Future: Proceedings of the 15th International Conference on Engineering and Product Design Education (E&pde13, Glasgow: The Design Society Institution of Engineering Designers , 2013, p. 82-87Conference paper (Refereed)
    Abstract [en]

    University teachers who start teaching right after graduation have not used and developed their knowledge professionally thus they have never had the opportunity to test their acquired knowledge in practice. This results in teaching that tends to be heavily theoretical because the teacher teaches what he/she has learned in studies, instead of teaching the knowledge gained through professional experience. Unfortunately a teacher can feel insecure when not knowing if their teaching reflects currently used methods and/or appropriate tools. An effect of this can be that teachers who feel insufficient in their role as teachers. The aim of this paper is to see if academic consulting not only increases the practical experience of the teacher, but also helps the teacher in their role and gives them a better understanding of what the state of the art is. While some schools have some cooperation with the business community, both in student projects and research projects, although it is not common with external non-research consultation projects, which are conducted by the university teachers. A questionnaire was sent to both teachers and students’ asking them of their experience of academic consulting’s benefits to the classroom experience. As a follow-up were several interviewed, along with clients to gain more insight. The results showed that teachers, students and the clients benefited from these types of projects.

  • 210.
    Berglund, Anders
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Tretten, Phillip
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Håkansson, Anders
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    A systematic self-assessment tool2012In: Proceedings of the 14th International Conference on Engineering and Product Design Education: Design Education for Future Wellbeing, EPDE 2012, 2012, p. 311-316Conference paper (Refereed)
    Abstract [en]

    The Bologna Process has led to fundamental changes in the way students are taught. This in turn has led to new quality assurance systems for teaching. For good outcomes to occur both the teachers and students need to be aware of the intended learning outcome (ILO) and this is made clearer by well defined Teacher/Learner Activities (TLAs). The Systematic Grading Procedure (SGP) has been shown to assist teachers grading student’s 3D-image work, fulfilling a need for assistance in subjects requiring grading of subjective nature. With the application of this method have both teachers and students been given a tool that helps them better understand the grading process and the level of importance of different parts of the 3D work. The aim of this study was to assess students’ learning outcomes. The SGP was used and compared by both teachers and students in assessing their own work. This study used four students who were introduced to the SGP at the introduction of the course. This was done to give then an idea how they are to understand the ILOs. After one of their assignments was graded the students were given an opportunity to improve their work using the SPG. Three of the four choose to improve their work. The ensuing interview and results showed that the SGP could be used as a tool to help students and teachers with the ILO and TLAs. In addition to that the SGP should further be tested for verification.

  • 211.
    Berglund, Anders
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Tretten, Phillip
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Högström, Per
    Luleå University of Technology, Department of Arts, Communication and Education, Education, Language, and Teaching.
    Is video feedback in higher education worth a byte?2015In: Great Expectations: Design Teaching, Research & Enterprise: Design Teaching, Research & Enterprise - Proceedings of the 17th International Conference on Engineering and Product Design Education (E&PDE15) / [ed] Ahmed Kovacevic ; Guy Bingham; Brian Parkinsson, Glasgow: The Design Society Institution of Engineering Designers , 2015, p. 258-263Conference paper (Refereed)
    Abstract [en]

    Feedback can be given in various situations, like after examinations, project work, and course completion. It is widely accepted that feedback is important for students’ learning, and it can be used in various ways, such as, written, face-to-face, and with the assistance of video recordings. This study focuses on the use of video recorded feedback to gather knowledge on how video recorded feedback can enhance the students learning. Since feedback in the study was given in video recordings, an alternate way was introduced, which add further insights for teaching and learning at university levels. The results showed that 94% preferred video recorded feedback over written feedback and they, in general, preferred face to face feedback (59%). Although, follow-up questions showed that the students found the recorded option beneficial since they could review the video several times in order to see and hear exactly what was stated and what part of their work it related to. In conclusion, video feedback of student work was perceived to be beneficial and the students and the teacher positively accepted it.

  • 212.
    Berglund, Filip
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Structural analysis and condition monitoring of grinding mills: a case study2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Grinding mills are large rotating cylindrical steel vessels used to grind ore and minerals into finer particles. The mills are important parts of the mineral enrichment process and the grinding is the last step of the comminution process, where the particle size is reduced by a combination of abrasion and impact.The rotation of the mill under loaded conditions can result in fatigue cracks. Fatigue cracks and associated failures have been identified as a major problem in mineral processing plants. The cracks lead to unpredicted and unplanned production stoppages for inspections and for repair and replacement of the cracked mill parts. This leads to increasing costs due to production loss, additional man-hours and spare parts.The purpose of the research presented in this licentiate thesis was to calculate the structural strains, stresses, displacements, etc. in grinding mills in operation, to prevent overloading, to calculate crack propagation speeds and critical crack lengths, and to develop new improved mills that would withstand the current loading. This research has also aimed to propose, develop and test methods for the detection and monitoring of fatigue cracks in mills during operation, in order to facilitate optimal maintenance decision-making based on current crack sizes.The performed research is a case study of the secondary pebble mills of LKAB, a mining company in northern Sweden. The mills are situated inside dressing plants KA1 and KA2 in Kiruna. To achieve the goals, a number of crack detection and monitoring methods were investigated and evaluated as to their ability to find and monitor fatigue cracks on the running mills. Measurements with wireless strain measurement equipment, infrared thermography and crack propagation sensors were performed on the mills in operation.A finite element model of a mill was developed to calculate the strains and stresses in the mill at any position in the mill and for any loading condition. A variety of spatial discretizations, boundary conditions, material properties and loading alternatives were considered to simulate the behaviour of the real mill in the best possible way. To calculate the loading on the mills in operation, a mathematical model and computer software were developed to calculate the charge configuration, as well as the loading and the magnitude and distribution of the forces acting on the mill in operation. Using the finite element model and the computer software, the global displacement field of the entire mill structure was calculated using quasi-static loading for different inputs of the charge and process parameters.To verify the finite element results, the measured strain ranges for one complete rotation of the mill were compared with the corresponding calculated ones. The numerical results were also verified with logged process data, such as bearing reaction forces. One conclusion, based on the comparisons, is that the developed finite element model and the developed software tools can be considered useful for engineering applications.The developed software tools, together with the finite element model, make it possible to calculate the global displacement field of the entire mill structure for any situation. This is achieved by inputting the desired process data and charge parameters into the software, calculating the loads and force distributions, exporting them to the finite element model, and running the simulation. From the global displacement field, strains, stresses, reaction forces, displacements, etc. can be calculated with standard routines for any position in the mill.The performed research work gives a deeper understanding of the field of structural analysis and load calculation of grinding mills in operation. The complexity of modelling the behaviour of mills in operation is high. Consequently, it is difficult to obtain accurate estimations of crack propagation speeds and critical crack sizes based on the calculated stresses.It has been found that strain measurements, with strain gauges attached to the mill mandrel, can be used to detect and monitor larger circumferential cracks near the flanges in the mill in operation, since the measured strain ranges increase with the crack size. It has further been found that infrared thermography can be used as a method to indicate cracks without stopping the mill, as the increased thermal gradient around the cracks can be detected by a special type of thermal instrument.Crack propagation sensors have proven to be ideal for high-precision online monitoring of the crack propagation of smaller cracks at the corners of the manholes in the mill. Finally, it has been found that strain measurement is a useful method not only to verify finite element results and to detect and monitor cracks, but also to prevent overloading of the mill and to estimate charge features such as the filling level, the charge shape and the position of the charge circumferentially inside the mill during operation.

  • 213.
    Berglund, Filip
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Structural analysis of a rotating mining mill with the finite element method2011In: Proceedings of Computational Modelling'11, Minerals Engineering International , 2011Conference paper (Other academic)
  • 214.
    Berglund, Filip
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Nordström, Jakob
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Parida, Aditya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Non-destructive testing (NDT) methods for detection and monitoring of fatigue cracks in mining mills2011In: International Journal of COMADEM, ISSN 1363-7681, Vol. 14, no 2, p. 18-26Article in journal (Refereed)
  • 215.
    Berglund, Filip
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Parida, Aditya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Health monitoring of mining mills with infrared thermography2011In: Proceedings of the 24th International Congress on Condition Monitoring and Diagnosis Engineering Management: COMADEM 2011 / [ed] Maneesh Singh; Raj B.K.N. Rao; J.P. Liyanage, COMADEM International, 2011, p. 1190-1196Conference paper (Refereed)
    Abstract [en]

    Infrared thermography has been investigated as a non destructive testing method for health monitoring of rotating mining mills. The idea is to monitor the thermal differences on the mill surface with thermal camera in order to detect and maintain cracks and other material damage in the mill material. A general description of the thermography technique, the theory behind, advantages and drawbacks as well as its use in other applications is presented. To test the usefulness of the method, real life measurements with IR-camera have been performed on several mining mills at a mining company located in northern Sweden. The results from these measurements are presented and discussed in this article. Infrared thermography is a fast and relatively cheap inspection method which can find and monitor material damage in rotating mining mills and help the maintenance personal in taking the corrective maintenance decisions.

  • 216.
    Bergman, Peter
    Luleå tekniska universitet.
    Optimisation of fragmentation and comminution at Boliden Mineral, Aitik Operation2005Licentiate thesis, comprehensive summary (Other academic)
    Abstract [sv]

    Syftet med denna avhandling är att optimera fragmenteringen i Bolidens Minerals dagbrott Aitikgruvan. Sprängning är en av huvudprocesserna i gruvbrytning och dess resultat har stor inverkan på gruvans totala ekonomi. Resultatet av fragmenteringen påverkar inte bara gruvans produktivitet och enhetskostnader utan även de efterföljande processerna krossning och malning i anrikningsverket. Optimeringar av delar i ett system leder ofta till en suboptimering av hela systemet. Traditionellt har gruvan och anrikningsverket varit uppdelade i separata resultatenheter med följd att gruvan suboptimerad sprängningen mot gruvans kostnader, utan hänsyn till resultatet längre fram i produktionskedjan. I det här arbetet inriktas designen av sprängningen mot de optimering av hela processen gruva och anrikning, d.v.s. maximera genomsättningen. Primärkvarnarna i anrikningsverket har identifierats som flakhals i produktionssystemet, gruva/anrikningsverk, varför sprängoptimering inriktas mot att maximera genomsättningen i dessa. Aitikgruvan är utrustad med teknik som möjliggör spårning av malmen från position i gruvan genom anrikningsverk, vilket medför att även resultat i anrikningsverk, t.ex. genomsättning i primärkvarnarna, kan återkopplas till dess ursprungliga position i gruvan. Utifrån kvarnarnas beteende, fyllnadsgrad, effekt och ingående styckefall, under produktion, kan en optimal förändring i styckefall bestämmas. Med utgångspunkt från att malmen har lika fragmenteringsegenskaper i dess stupningsriktning kan antagandet göras att malmen i underliggande pall har liknande mekaniska egenskaper som den aktuella salvan/området, vilket antas ge lika resultat vid samma sprängdesign. Det optimala styckefallet återkopplas till gruvan och en sprängdomänsindelning och sprängdesign för dessa domäner kan göras för nästkommande brytningsnivå. Med utgångspunkt från det optimala styckefallet för primärkvarnarna för de olika områdena i gruvan, bestäms sprängdesignen för underliggande pall med hjälp av en sprängmodell och en krossmodell. För att modellera krossningen och sprängningen görs inga laboratorietest eller fältarbeten, utan de ingående parametrarna fås ur den styckefallsfördelning, både före och efter kross, som uppnås i de olika sprängdomänerna. För att undersöka om finare styckefall ger ökad genomsättning i primärkvarnarna har fem testsalvor skjutits och utvärderats. Salvorna har jämförts mot de salvor som låg rakt ovan i föregående pall. Testsalvorna fick 35% högre specifik laddning än vad som vanligtvis används. Salvornas position i gruvan var inte valda utifrån sprängdomänsindelningen, utan tagna när tillfälle gavs. Genomsättningsökningen för de fem testsalvorna blev i medel åtta procent. För de två testsalvorna som låg i sprängdomänen som har den högsta förväntade genomsättningsökningen blev genomsättningen 14 respektive 22 procent högre. Den samlade kunskapen om styckefallets inverkan på genomsättningen i primärkvarnarna pekar mot att finare styckefall i regel ger högre genomsättning. Innan metodiken med att bestämma det optimala styckefallet kan användas fullt ut, måste fler undersökningar göras för att fastställa sambanden, framförallt behövs fler testsalvor. För utveckling av kross- och sprängmodellerna måste styckefallsmätningen bli mer tillförlitlig.

  • 217.
    Beyglou, Ali
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    On the Operational Efficiency in Open Pit Mines2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Open pit mines constitute more than half of global minerals production. Yet most of the large, high-grade, and close to the surface deposits have been depleted or are currently in production. Besides, volatility in commodity prices and stringent environmental regulations limit the up-scaling expansions in large open pits. Consequently, the mines are determined to increase their operational efficiency in order to thrive. This has recently led to major metallurgical improvements in the processing of ores; whereas the improvements in mining of the said ores are relatively overdue in terms of efficiency and technological advancement. This thesis concentrates on the mining activities and their efficiency in open pits with a focus on drilling, blasting, loading, and crushing. As all of these tasks revolve around the fragmentation of run-of-mine ore, their relationships and efficiencies are explored within the context of fragmentation.

    Fragmentation is a result of complex interactions between rockmass, blasting geometry, explosive, and timing sequence of blast holes. The influence of rockmass and timing sequence on fragmentation and efficiency are explored, as well as the target fragmentation for efficient loading and crushing. Moreover, the techniques for measuring fragmentation are evaluated as to whether they can benefit mines in terms of efficiency. As the circumstances in open pits are essentially site-specific, these issues are addressed as a case study of the Aitik mine in Sweden.

    The research comprised four elements. First, the influence of rockmass fractures on blast results and downstream efficiency was evaluated via full-scale field trials. The fractures in and around the case study mine were mapped using a photogrammetric technique and six production blasts were adapted to the major fracture sets to evaluate the effect of initiation direction on downstream efficiency. Second, the influence of the timing sequence of blast holes was explored within the theories of stress waves interaction and their consequent effect on fragmentation. Theoretical and numerical solutions were accompanied by six field trials in full-scale to evaluate the influence of short delay times on fragmentation and efficiency. Third, an empirical study was conducted to correlate fragmentation to the efficiency of loading and crushing; this was done to define a target fragmentation for the studied case. Finally, the techniques to assess fragmentation were discussed both quantitatively and qualitatively.

    The findings indicated that rockmass fractures have a significant influence on the quality of blasts and efficiency of downstream tasks. In the case study mine, adjustments to orientation of drill pattern and initiation direction of blasts suggested that careful experimentation in this regard can yield a favourable initiation direction with respect to existing discontinuities. Finer fragmentation and higher loading efficiencies can be achieved by adapting the blast designs to the existing fractures, which can lead to significant savings in the long run. On the contrary, the influence of stress waves interaction on blast results turned out to be marginal. Neither the theoretical and numerical solutions nor the field trials showed any significant improvements in blast results from short delays. In fact, it was found rather implausible to expect any noticeable improvements by using short delays.

    The empirical method to evaluate target fragmentation proved useful as well. It was shown that by incorporating different data from various sources in a mine, one can follow the ore from muckpile to loaders and then to crushers. Having a qualitative understanding of the fragmentation, and by developing tools to measure efficiency, one can estimate what fragmentation is most favourable for an efficient operation. Finally, two image-based methods to assess fragmentation were discussed in terms of repeatability and statistical significance. It was found that the scatter in both methods is rather large, introducing a certain ambiguity in representativeness of their results. Admittedly, it was found that in matters of long-term efficiency, the number, size and representativeness of assessed samples are of more importance compared to the accuracy of individual measurements.

  • 218.
    Beyglou, Ali
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Target fragmentation for efficient loading and crushing: The Aitik case2017In: The Southern African Journal of Mining and Metallurgy, ISSN 2225-6253, E-ISSN 1543-9518, Vol. 117, no 11, p. 1053-1062Article in journal (Refereed)
    Abstract [en]

    Blast-induced fragmentation has a significant influence on the operational efficiency of open pit mines, especially on loading and crushing, the two immediate tasks after blasting. This study presents an empirical method to determine the target fragmentation for efficient loading and crushing at the Aitik mine in Sweden. In the study, the loading efficiency of rope shovels was correlated to the energy consumption and throughput of a gyratory crusher. Two photographic techniques were utilized to assess the feed fragmentation, considering the lithological origin of the ore as an indicator of hardness. The results indicate ore hardness is most influential in mid-range fragmentation, with a marginal effect in coarser fragmentations. The influence of fragmentation is more pronounced in the coarse region, with a sudden reduction in efficiency for P80 values coarser than 800 mm. The results suggest tailoring the fragmentation to a P80 of 600-800 mm could lead to higher operational efficiency at Aitik. 

  • 219.
    Beyglou, Ali
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Face to Surface –Task 1: Baseline Mapping of the Mining Operation in Aitik2015Report (Other academic)
    Abstract [en]

    “Face to Surface” is a project within the strategic innovation program “Mining and Metals”, which is a collaboration between Vinnova, Formas and Energy Agency of Sweden with additional funding from Boliden Mineral AB and LKAB. The project is aimed to improve productivity and efficiency of mining activities through optimization of the overall production chain. The current status report corresponds to the first task of the project–Baseline Mapping.The report presents the overall process chain of mining operation in Boliden Aitik copper mine, Sweden. The production chain is initially described as a system of singular processes. Each process is then described in more details, including inter-relations and downstream effects of each process within the operation. The report provides a basis for identification of potential fields of improvement in the process. The subsequent tasks of the project will be conducted upon internal discussions based on the findings of this report.

  • 220.
    Beyglou, Ali
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Nils
    Boliden Mineral AB.
    Adjusting Initiation Direction to Domains of Rock Mass Discontinuities in Aitik Open Pit Mine2015In: 11th International Symposium on Rock Fragmentation by Blasting: Fragblast11, Carlton, Vic: The Australasian Institute of Mining and Metallurgy, 2015, p. 385-391Conference paper (Refereed)
    Abstract [en]

    As demand for optimisation of mining processes increases, more attention is drawn to blast performance and fragmentation improvement. Fractures and discontinuities are among the most influential factors in blast results, therefore one of the initial steps towards blast optimisation is to gather information about the rock mass and integrate it in blast design. This paper presents a method for assessment of rock mass discontinuities and integrating it in production blasts in the Aitik open pit copper mine in Sweden. 3D photogrammetric techniques were utilised to map discontinuities and distinguish domains of similar geologic structures in the pit. As a pilot study for a future campaign, four different initiation directions were tested through six pilot blasts in one of the domains. The results were compared in terms of swell and loading efficiency of rope shovels to identify the correlation between blast performance and initiation direction compared to major discontinuity families. It was established that in the trial domain, blasts initiated towards north or north-west yielded larger swell and better performance of loading. Comparing these blasts with discontinuity families show that there is a correlation between blast performance and initiation direction according to the dip and strike of these discontinuities. Such knowledge can be used for future blasts in the same domain to increase long-term operational efficiency through slight modifications in drill pattern and initiation design.

  • 221.
    Biledt, E.
    et al.
    Luleå tekniska universitet.
    Kumar, Uday
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Condition monitoring of hydraulic system on load-hand dump machines1991In: Condition monitoring '91: proceedings of an International Conference on Condition Monitoring held at the Stadthalle, Erding, Germany, 14-16 May 1991 / [ed] Mervin H. Jones; J. Guttenberg; H. Brenneke, Swansea: Pineridge Press , 1991Conference paper (Refereed)
  • 222.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Arvanitidis, Ioannis
    Jönsson, Pär
    Kungliga tekniska högskolan, KTH.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Physical modeling and control of dynamic foaming in an LD-converter process2001In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 37, no 4, p. 1067-1073Article in journal (Refereed)
    Abstract [en]

    This paper deals with physical modeling and control of dynamic foaming in the LD-converter process. An experimental setup consisting of a water model, digital signal processor, and PC hardware is built and shown to be useful for studying dynamic foaming. Furthermore, a foam height estimation algorithm is presented and validated through experiments. Finally, sound signals from the LD-converter and water model are compared and similarities between them are found.

  • 223.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Arvanitidis, Ioannis
    Medvedev, Alexander
    Jönsson, Pär
    Kungliga tekniska högskolan, KTH.
    Foam level control in a water model of the LD converter process2001In: Automation in mining, mineral, and metal processing 2001: a proceedings volume from the 10th IFAC symposium, Tokyo, Japan, 4 - 6 September 2001 / [ed] Mituhiko Araki, Oxford: Published for the International Federation of Automatic Control by Pergamon , 2001Conference paper (Refereed)
    Abstract [en]

    This paper deals with estimation and control of foam level in dynamic foaming. An improved foam level estimation methodology from a microphone signal and its automatic calibration is presented. The dynamical reaction of the foam level on air lance movements is modelled using system identification. Based on the resulting mathematical model, a controller for foam level stabilisation is designed and applied to a water model, representing the LD converter process. It is shown that the foam level can be controlled using a microphone as the measurement device and air lance movement as the actuator.

  • 224.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Arvanitidis, Ioannis
    Department of Metallurgy, Royal Institute of Technology.
    Medvedev, Alexander
    Jönsson, Pär
    Kungliga tekniska högskolan, KTH.
    Foam level control in a water model of the LD converter process2001In: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, Vol. 34, no 18, p. 273-278Article in journal (Refereed)
    Abstract [en]

    This paper deals with estimation and control of foam level in dynamic foaming. An improved foam level estimation methodology from a microphone signal and its automatic calibration is presented. The dynamical reaction of the foam level on air lance movements is modelled using system identification. Based on the resulting mathematical model, a controller for foam level stabilisation is designed and applied to a water model, representing the LD converter process. It is shown that the foam level can be controlled using a microphone as the measurement device and air lance movement as the actuator.

  • 225.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Arvanitidis, Ioannis
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Jönsson, Pär
    Kungliga tekniska högskolan, KTH.
    Foam level control in a water model of the LD converter process2003In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 11, no 1, p. 49-56Article in journal (Refereed)
    Abstract [en]

    This paper deals with estimation and control of foam level in dynamic foaming. An improved foam level estimation methodology from a microphone signal and its automatic calibration is presented. The dynamical reaction of the foam level on air lance movements is modelled using system identification. Based on the resulting mathematical model, a controller for foam level stabilisation is designed and applied to a water model, representing the LD converter process. It is shown that the foam level can be controlled using a microphone as the measurement device and air lance movement as the actuator.

  • 226. Biswal, Munro
    et al.
    Parida, Aditya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    An integrated approach for open e-Maintenance2010In: Proceedings of the 1st international workshop and congress on eMaintenance, Luleå tekniska universitet, 2010, p. 107-114Conference paper (Refereed)
    Abstract [en]

    The present day e-maintenance space is evolving with isolated legacy sub-systems or packages that span heterogeneous and domain specific industry verticals. Developing a unified platform for e-maintenance catering to the varied domains shall hence pose a major challenge. An open systems based platform for emaintenance can overcome some of these hurdles by defining the otherwise disparate systems as abstract entities with well defined public interfaces. The interfaces can be broadly classified based on the technology types, thus allowing individual vertical emaintenance applications to align with their respective business interests. In all, this shall greatly help in reducing the overall operating costs and at the same time provide increased flexibility, reusability and reliability. The underlying standard protocol, defined through a group consensus, shall be responsible for transport of the e-maintenance data between the distributed subsystems via the TCP/IP standard within multiple administrative domains of e-maintenance across wired and wireless networks. This paper also looks at e-maintenance from a systems integration perspective and illustrates how open systems based approach can help achieve integration better.

  • 227.
    Bjarnason, B.
    et al.
    Luleå tekniska universitet.
    Ljunggren, Christer
    Luleå tekniska universitet.
    Stephansson, Ove
    Luleå tekniska universitet.
    New developments in hydrofracturing stress measurements at Luleå University of Technology1989In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 26, no 6, p. 579-586Article in journal (Refereed)
    Abstract [en]

    Instrument and theoretical developments in hydrofracturing stress measurements at Lulea University of Technology since the first workshop in Monterey in 1981 are described and the general experience with the method in Sweden is summarized. A new field unit is described which includes a 1000-m long multihose and a 100 MPa water pump. Stress measurements by means of injection tests on preexisting fractures have been introduced and applied at two sites in Sweden. A theory has been developed which permits estimation of the maximum and minimum horizontal stresses in cases where transverse hydrofractures are created in the borehole wall instead of axial.

  • 228.
    Bjarnason, Bjarni
    Luleå tekniska universitet.
    Hydrofracturing rock stress measurements in the Baltic shield1986Licentiate thesis, monograph (Other academic)
  • 229. Bjarnason, Bjarni
    et al.
    Leijon, Bengt
    Luleå tekniska universitet.
    Stephansson, Ove
    Luleå tekniska universitet.
    The Bolmen project1986Report (Other academic)
  • 230.
    Bjarnason, Bjarni
    et al.
    Luleå tekniska universitet.
    Stephansson, Ove
    Luleå tekniska universitet.
    Torikka, Arne
    Luleå tekniska universitet.
    Bergström, K.
    Luleå tekniska universitet.
    Four years of hydrofracturing rock stress measurements in Sweden1986In: Rock stress and rock stress measurements: proceedings of the International Symposium on Rock Stress and Rock Stress Measurements, Stockholm 1-3 September 1986 / [ed] Ove Stephansson, Luleå: CENTEK , 1986, p. 421-247Conference paper (Refereed)
  • 231.
    Björling, Sten-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Integration of knowledge management systems and end-user interfaces for MPMM2011In: MPMM 2011: Maintenance Performance Measurement & Management: Conference Proceedings / [ed] Diego Galar; Aditya Parida; Håkan Schunnesson; Uday Kumar, Lulleå: Luleå tekniska universitet, 2011, p. 209-212Conference paper (Refereed)
    Abstract [en]

    Maintenance can be considered as a combined information and knowledge processing and management system. Effective knowledge, practices and experiences management is growing in importance, especially in advanced processes and management of advanced and expensive assets. Efforts of integrating maintenance knowledge management (MKM) processes with MKMM will be increasingly more important due to the increasing complexities of these overall systems – the context in which the performance measurements has been performed is also important input in the performance analysis. Integration of MKM in MPMM can result in higher quality of the decisions and actions in the maintenance processes and in the overall work to increase efficiency and decreasing costs in the organizations.Integration of MKM (Maintenance Knowledge Management – knowledge, experiences and practices management) with collaborative structures and interfacing abilities with qualified services for simulation, modeling and computations can be regarded as Intelligence-based Maintenance (iMaintenance).These infrastructures present in iMaintenance can further improve MPMM efforts due to possible utilization of more accurate property and context information and services – changes in installations, environmental factors etc. not easily integrated in current MPMM implementations.Integration of MPMM with iMaintenance solutions can also improve the interaction between management and the maintenance operators and also allow improved interaction and integration with production operators in the organization. MPMM can with this approach be integrated as a natural component in the overall ICT-based maintenance and collaboration solutions – the performance status reporting will be seen as a natural extension to the normal routines. In this context the usability of the end-user environments will be very important – especially when designing systems for mobile use by maintenance operators in the field.

  • 232.
    Björling, Sten-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Modular tool concepts for sustainable product development environments2009In: Proceedings of the 2nd International Conference on Advanced Design and Manufacture / [ed] Daizhong Su; Quingbin Zhiang; Shifan Zhu, Trans Tech Publications Inc., 2009, p. 55-59Conference paper (Refereed)
    Abstract [en]

    An existing demonstrator for E-maintenance solutions for advanced aviation maintenance staff was extended to incorporate abilities as a collaborative environment for developers of sustain­able products. Most of the existing core concepts and functions in the demonstrator were found to be viable: work context management, modularisation, information and web services access. This paper pres­en­ts more in detail the modularization concept used in the demonstrator and its potential use in collaborative environments for sustainable prod­ucts developers. This concept if implemented allow faster integration of external web services and information sources into the sustainable product design work­flows and processes.

  • 233.
    Björling, Sten-Erik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Baglee, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Galar, Diego
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Singh, Sarbjeet
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Kumar, Uday
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Maintenance knowledge management with fusion of CMMS and CM2013In: DMIN 2013 International Conference on Data Mining: 22nd -25th July 2013, Las Vegas, Nevada, USA, 2013Conference paper (Refereed)
    Abstract [en]

    Maintenance can be considered as an information, knowledge processing and management system. The management of knowledge resources in maintenance is a relatively new issue compared to Computerized Maintenance Management Systems (CMMS) and Condition Monitoring (CM) approaches and systems. Information Communication technologies (ICT) systems including CMMS, CM and enterprise administrative systems amongst others are effective in supplying data and in some cases information. In order to be effective the availability of high-quality knowledge, skills and expertise are needed for effective analysis and decision-making based on the supplied information and data. Information and data are not by themselves enough, knowledge, experience and skills are the key factors when maximizing the usability of the collected data and information. Thus, effective knowledge management (KM) is growing in importance, especially in advanced processes and management of advanced and expensive assets. Therefore efforts to successfully integrate maintenance knowledge management processes with accurate information from CMMSs and CM systems will be vital due to the increasing complexities of the overall systems.Low maintenance effectiveness costs money and resources since normal and stable production cannot be upheld and maintained over time, lowered maintenance effectiveness can have a substantial impact on the organizations ability to obtain stable flows of income and control costs in the overall process. Ineffective maintenance is often dependent on faulty decisions, mistakes due to lack of experience and lack of functional systems for effective information exchange [10]. Thus, access to knowledge, experience and skills resources in combination with functional collaboration structures can be regarded as vital components for a high maintenance effectiveness solution.Maintenance effectiveness depends in part on the quality, timeliness, accuracy and completeness of information related to machine degradation state, based on which decisions are made. Maintenance effectiveness, to a large extent, also depends on the quality of the knowledge of the managers and maintenance operators and the effectiveness of the internal & external collaborative environments. With emergence of intelligent sensors to measure and monitor the health state of the component and gradual implementation of ICT) in organizations, the conceptualization and implementation of E-Maintenance is turning into a reality. Unfortunately, even though knowledge management aspects are important in maintenance, the integration of KM aspects has still to find its place in E-Maintenance and in the overall information flows of larger-scale maintenance solutions. Nowadays, two main systems are implemented in most maintenance departments: Firstly, Computer Maintenance Management Systems (CMMS), the core of traditional maintenance record-keeping practices that often facilitate the usage of textual descriptions of faults and actions performed on an asset. Secondly, condition monitoring systems (CMS). Recently developed (CMS) are capable of directly monitoring asset components parameters; however, attempts to link observed CMMS events to CM sensor measurements have been limited in their approach and scalability. In this article we present one approach for addressing this challenge. We argue that understanding the requirements and constraints in conjunction - from maintenance, knowledge management and ICT perspectives - is necessary. We identify the issues that need be addressed for achieving successful integration of such disparate data types and processes (also integrating knowledge management into the “data types” and processes).

  • 234. Björling, Sten-Erik
    et al.
    Kumar, Uday
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    ICT concepts for managing future challenges in e-maintenance2009In: 22nd International Congress on Condition Monitoring and Diagnostic Engineering Management: COMADEM 2009 ; June 9 - 11, 2009, San Sebastian, Spain, Miramar Palace / [ed] Aitor Arnaiz, Eibar: Fundaci n Tekniker , 2009Conference paper (Refereed)
    Abstract [en]

    The maintenance & operations fields are & will increasingly be dominated by information fragmentation, product & process complexities, increasingly important needs to access relevant knowledge in an ever faster pace, increased need for accurate analysis & implementation of the analysis results & need for more effective & accurate management.In addition to this the created solutions & processes also has to be effectively used in different work contexts including mobile work contexts & supporting interoperability with external ICT systems & processes. ICT-based frameworks should according to the factors & challenges described above be structured to be flexible enough to over time integrate new types of information & services, be usable both internally in the industrial facilities & in the field (mobile) & effectively act as a bridge between older & future ICT-systems. An example of such an integration approach is the PROTEUS project aiming at developing an "integrating" platform for maintenance management. The frameworks described during this presentation also will include modularised integration of not only data in existing maintenance systems and knowledge resources but also integration with web services (SOA), access & management of external computational services (analysis). These different modules will be accessible more dynamically than earlier web-based solutions. This in an environment that support several parallel work contexts & use not only in fixed networks but also in mobile / nomadic settings allowing a high degree of flexibility for the maintenance & operations staff.

  • 235. Björnfot, Folke
    et al.
    Stephansson, Ove
    Luleå tekniska universitet.
    Interaction of grouted rock bolts and hard rock masses at variable loading in a test drift of the Kiirunavaara mine, Sweden1984In: Rock bolting: theory and application in mining and underground construction ; proceedings of the International Symposium on Rock Bolting, Abisko, 28. August - 2. September 1983 / [ed] Ove Stephansson, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1984, p. 377-395Conference paper (Refereed)
    Abstract [en]

    description is presented on the interaction between a reinforced drift and the surrounding rock. It attempts to explain the support mechanisms and characteristics of cement grouted rock bolts, as used in hard rock mining and underground construction. A 20 m long section of a test drift at the 514 m level in the Kiirunavaara Mine, was instrumented with 20 rock bolts mounted with strain gauges and linked to a data logger, and 50 bolts combined with single-anchor extensometer. Rock movements were measured with 23 borehole extensometers, 45 convergence measurement stations, and precise levelling. 14 stress monitors recorded changes in the tangential stresses in the surrounding rock mass.

  • 236.
    Björnfot, Folke
    et al.
    Luleå tekniska universitet.
    Stephansson, Ove
    Luleå tekniska universitet.
    Interaction of grouted rock bolts and hard rock masses at variable loading in a test haulage of the Kiirunavaara Mine, Sweden1983In: CIM bulletin, ISSN 0317-0926, E-ISSN 1718-4169, Vol. 76, no 856, p. 22-Article in journal (Other academic)
  • 237. Björnfot, Folke
    et al.
    Stephansson, Ove
    Luleå tekniska universitet.
    Mechanics of grouted rock bolts: field testing in hard rock mining1984Report (Other academic)
  • 238. Blackwood, R.L.
    et al.
    Sandström, S.
    Boliden Mineral AB.
    Leijon, Bengt A.
    Luleå tekniska universitet.
    A study of the bond strength in cemented epoxy solid inclusion stress cell installations1986In: Rock stress and rock stress measurements: proceedings of the International Symposium on Rock Stress and Rock Stress Measurements, Stockholm 1-3 September 1986 / [ed] Ove Stephansson, Luleå: CENTEK , 1986, p. 523-528Conference paper (Refereed)
  • 239.
    Block, J.
    et al.
    Saab Aerotech, Linköping.
    Söderholm, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Tyrberg, T.
    Saab Aerotech, Linköping.
    Evaluation of preventive maintenance task intervals using field data from a complete life cycle2008In: IEEE Aerospace Conference Proceedings: -8 March 2008 : [Big Sky, Montana]., Piscataway, N.J: IEEE Communications Society, 2008, Vol. Article number 4526635, p. 1-11Conference paper (Refereed)
    Abstract [en]

    In this paper the appropriateness of initial preventive maintenance task intervals and the improvement of changed intervals are evaluated. The evaluation criteria are partly derived from logic found in the RCM (Reliability-Centered Maintenance) methodology. Empirical data is related to the whole life cycle of the Swedish military aircraft system FPL 37 Viggen, from 1977 to 2006. The analysis shows that the maintenance intervals are partly appropriate and that some performed changes are improvements. These conclusions are strengthened if the phase-out of the aircraft system is considered, where the preventive maintenance strategy has been replaced with a corrective one, in order to achieve cost-effectiveness. Considering the perfect repair assumption, it seems that the overhaul tasks essentially bring the items back to a state as good as new. The performed evaluation mostly considers when the failures are recognized, i.e. during operation or during maintenance. Hence, aspects such as item accessibility, personnel skill levels, and maintenance task intervals for other items are not included in the evaluation.

  • 240.
    Block, J.
    et al.
    Logistic Analysis and Fleet Monitoring Division, Saab Aerotech.
    Tyrberg, T.
    Maintenance Information, Systems Division, Saab Aerotech.
    Fuqing, Yuan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Optimal repair for repairable components during phaseout an aircraft fleet2010In: IEEE Aerospace Conference Proceedings, Piscataway, NJ, 2010, article id 5446880Conference paper (Refereed)
    Abstract [en]

    The successive removal of units from a group of systems during phasing out leads to a variable requirement for stock level of spare parts. Repairable units from phased out systems can be reused for the remaining functional systems in the group. Hence, the stock level of spare parts increases and the demand for spare parts decreases. This can lead to excessive stocking of spare parts and high maintenance costs for spare parts. This paper proposes a methodology to determine the optimum time to stop repair of repairable units to minimize the maintenance cost. It uses a Poisson Distribution based on NHPP (Non-Homogenous Poisson Process) to predict the available number of units, while fulfilling the demand for spare parts for the remaining systems. A concept, called Minimal Margin is introduced to formulate the problem and nonlinear programming is proposed to obtain the optimum solution. Finally, a numerical example is presented to demonstrate the approach

  • 241.
    Block, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Dependability analysis of military aircraft fleet performance in a lifecycle perspective2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Today's highly advanced technological flying platforms, such as aircraft, helicopters and Unmanned Air Vehicles (UAVs), are characterised by a high degree of complexity. Simultaneously, they are used in different operational and mission profiles, and also in multiple operational environments and geographical settings. In addition, the interaction between major stakeholders, such as operators and support providers, has been drastically changed by concepts such as Performance-Based Logistics (PBL), where the support providers' commitment increases through the offering of availability performance at a fixed price. These changes put new and stringent requirements on dependability analysis to make efficient use of field data (e.g. generated by built-in tests, operation and maintenance) to sustain, improve and predict the availability performance of flying platform fleets. The purpose of the research presented in this thesis is to explore and describe methodologies and tools for dependability analysis, modelling and simulation of fleets of complex systems, in order to support improvement decisions throughout the fleets' whole lifecycle. More specifically, the objective of the research is to contribute to the development of a tool for modelling and simulation of multiple parallel lifecycle phases of complex technical systems in a fleet. The focus is on the assessment of field data and the extraction and prediction of information for continuous improvement of subsystem reliability performance, organisational maintenance support performance and fleet availability performance. The empirical work focuses on the Swedish military aeronautics community. The data has been collected through interviews, observations, document studies and archival records, such as recordings of in-flight parameters and maintenance actions. The data has been analysed to investigate critical aspects, such as the perfect repair assumption, the appropriateness of decisions about changes of maintenance intervals and of the No Fault Found (NFF) phenomenon. Through a literature study and practical efforts, this thesis also outlines and exemplifies methodologies and tools that support dependability analysis of an aircraft fleet. In addition, modelling and simulation efforts have been made to enable prediction of aircraft fleet performance and beneficial adjustments of support resources during the fleet retirement phase. The results act as input to a conceptual model that describes the phasing-in, operation and retirement of an aircraft fleet. The model aims to identify when it is cost-effective to consider the Remaining Useful Life (RUL) of individual repairable components comprising aircraft being retired, and utilise these components as spare parts for the aircraft staying in service. In summary, the performed work indicates that, in today's context with PBL and excessive amount of available data, dependability analysis, modelling and simulation must become more transparent, traceable and intersubjective.

  • 242.
    Block, Jan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Ahmadi, Alireza
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Tyrberg, Tommy
    Saab Support and Services.
    Using Monte Carlo simulation as support for decision making while negotiating a PBL contract2014In: IEEE Aerospace Conference. Proceedings, ISSN 1095-323X, article id 6836495Article in journal (Refereed)
    Abstract [en]

    In connection with performance-based logistics (PBL) contracts for aircraft fleets it is very important to carefully analyse both operations and maintenance before and during the contract negotiation phase. Monte Carlo Simulation is a valuable methodology in this context since it allows delimiting and exploring a complex parameter space in a transparent and relatively easily visualized manner. With timely analyses it is possible to identify both technical and economic risks and minimize the possible consequences, a process that benefits both parties in the negotiation process. This paper describes a part of this process in connection with the negotiation of a PBL contract for the Swedish Air Force SAAB 105 (SK 60) trainer fleet between Saab AB and the Swedish Defence Materiel Administration (FMV). The information used in the simulations was largely empirical data derived from previous operations of the aircraft system. The main factors that were simulated were operational requirements, fleet size, spares inventories, turn-around times, failure rates and influence of extraneous factors (e. g. weather). The simulations resulted in considerable savings due to reduction of the active fleet size, and increased reclamation of surplus spares and units from retired aircraft.

  • 243.
    Block, Jan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Ahmadi, Alireza
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Tyrberg, Tommy
    Saab Support and Services.
    Kumar, Uday
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Fleet-level reliability analysis of repairable units: a non-parametric approach using the mean cumulative function2013In: International Journal of Pedagogy, Innovation and New Technologies, ISSN 0973-1318, E-ISSN 2392-0092, Vol. 9, no 3, p. 333-344Article in journal (Refereed)
    Abstract [en]

    Complex technical systems are normally repaired rather than replaced when they fail. It is often desirable to analyze the reliability characteristics of these systems based on data generated in a customer use environment, in order to assess the reliability, frequency of failure or other parameters which may be influenced by the systems’ age and usage. Despite the advantages of continuously analyzing reliability data to be able to improve the maintenance programme continuously, methods such as parametric and non-parametric analysis are often ignored due to a belief that the mean time between failures (MTBF) is sufficient to describe the reliability pattern of repairable units. This paper describes the use of the mean cumulative function (MCF) and linear estimates based on the recurrence rate to predict the expected number of failures in the future. Reliability data from two repairable units are used to verify the procedure and comparison. The empirical data used in the paper is based on field data gathered during the operational life of the Swedish military aircraft system FPL 37 Viggen from 1977 to 2006, which essentially is the whole life cycle of the system.

  • 244.
    Block, Jan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Ahmadi, Alireza
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Tyrberg, Tommy
    Saab Aerotech.
    Kumar, Uday
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Fleet-level Reliability of Multiple Repairable Units: a Parametric Approach using the Power Law Process2014In: International Journal of Pedagogy, Innovation and New Technologies, ISSN 0973-1318, E-ISSN 2392-0092, Vol. 10, no 3, p. 239-250Article in journal (Refereed)
    Abstract [en]

    The application of parametric reliability analysis methods for repairable units, such as Power law process, is quite clear and straightforward for a single repairable unit. However, in practice, the analyst needs to know the reliability characteristics of units at a fleet level. The application of parametric reliability analysis methods at the fleet level, even if it is limited in scope, is quite complex. The aim of this paper is to describe the use of the power law process for multiple repairable units with differing reliability characteristics, to predict the expected number of failures at fleet level. The empirical data used in the paper are based on field data gathered during the operational life of two types of multi repairable units used in the Swedish military aircraft system FPL 37 Viggen from 1977 to 2006. The paper performs the trend test using TTT-based MIL-HDBK-189 and Laplace tests, and assesses the equality of shape-parameters for the intensity function of the power law process for multiple units. Estimation of the scale- and shape-parameters using maximum likelihood estimation is also performed. The parametric approach using power law process was found to yield relatively accurate estimations of number of failures, compared to empirical data

  • 245.
    Block, Jan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Ahmadi, Alireza
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Tyrberg, Tommy
    Logistics Analysis and Fleet Monitoring, Saab Support and Services, Linköping.
    Söderholm, Peter
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    Part-out-based spares provisioning management: A military aviation maintenance case study2014In: Journal of Quality in Maintenance Engineering, ISSN 1355-2511, E-ISSN 1758-7832, Vol. 20, no 1, p. 76-95Article in journal (Refereed)
    Abstract [en]

    Purpose – The purpose of this paper is to present the prerequisites for a part-out-based spares provisioning (PBSP) programme during the phase-out of an aircraft fleet. Furthermore, associated key decision criteria are identified and a framework for the phase-out management process is presented. Design/methodology/approach – Once a decision has been taken to phase-out an aircraft fleet, a number of routines for operations, maintenance and storage are affected and new tasks and functions must be introduced before initiating the actual parting-out process. A decision-making system and a management framework is needed to manage spares planning during the end-of-life phase to ensure availability at minimum cost and to ensure a manageable risk of backorders. Findings – For PBSP programme during the phase-out of an aircraft fleet to succeed and be cost-effective, a number of linked processes, tasks and decisions are required, e.g., those included in the framework proposed in this paper (see Figure 3). A successful implementation of PBSP also requires that these processes and tasks are carried out in a timely manner and that the communications between the concerned parties are prompt, clear and direct. One experience from the studied case is that close and trustful contacts and cooperation between the operator and maintenance provider(s) will greatly facilitate the process. Originality/value – Although the PBSP method is fairly commonly applied within both the military and the civilian sector, somewhat surprisingly very literature has been published on the subject. Indeed, remarkably little has been published on any aspects of maintenance during the end-of-life period.

  • 246. Block, Jan
    et al.
    Söderholm, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Tyrberg, Tommy
    Saab Aerotech.
    Changes in items' failure pattern during maintenance: an investigation of the perfect repair assumption2008In: Annual Reliability and Maintainability Symposium, 2008: RAMS 2008 ; Las Vegas, Nevada, USA, 2008, 28 - 31 Jan, Piscataway, NJ: IEEE Communications Society, 2008, p. 117-122Conference paper (Refereed)
    Abstract [en]

    It is clear that the simple ‘perfect repair' assumption is not immediately applicable to any of the studied types of hardware, i.e. Cooling Turbine, High-Voltage Generator, Hydraulic Accumulator, and Radar Transmitter. Hence, the assumption of ‘perfect repair' needs to be validated for each specific type of item. Assumptions based on the type of physical hardware (e.g. mechanical item or avionics item) are not always trustworthy.Strangely enough the ‘perfect repair' assumption fits best for the Cooling Turbine, which is a highly stressed mechanical item, while the fit is much poorer for the Radar Transmitter, which is an avionics item and for the Hydraulic Accumulator.For the Radar Transmitter the trend seems to be very scattered. For items with a large number of failures early in their life-cycle, repair is ‘better than perfect', i.e. the items become more reliable after repair, presumably by elimination of less reliable subcomponents. However, this effect is not seen for items with few failures early in their life-cycle. For these items ‘perfect repair' initially seems to be a valid model. However, in many cases repair becomes ‘less than perfect' later in the life-cycle. For the Hydraulic Accumulator this trend is even more accentuated and individual items seem to fall into two distinct subpopulations with opposite reliability trends.

  • 247.
    Block, Jan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Tyrberg, T.
    Saab Aerotech.
    Söderholm, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    No Fault Found events during the operational life of military aircraft items2009In: 8th International Conference on Reliability, Maintainability and Safety, 2009: ICRMS 2009 ; 20 - 24 July 2009, Chengdu, China / [ed] Rui Kang, Piscataway, NJ: IEEE Communications Society, 2009, p. 920-924Conference paper (Refereed)
    Abstract [en]

    No fault found (NFF) events are critical and well-known problems for certain aircraft items. This paper presents a study of these events for repairable items with on-condition maintenance, based on operational data from a military aircraft. Some findings are that: the number of NFF events is influenced by item type and number of repairs; most NFF events are initiated by faults recognized during operation; and different inspections contribute to NFF events. Hence, item design and tests at different operational modes and maintenance echelons should be better aligned to reduce the number of NFF events

  • 248.
    Bondarchuk, Alexander
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Rock mass behavior under hydropower embankment dams: results from numerical analyses2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Bridges are an important element of the infrastructure today. The technical competence has reached high levels in most countries and the limits given to a bridge designer are set by economic restrictions rather than technical skill. The ever lasting chase for more economic solutions and procedures includes both a wish for cheaper constructions as well as for a decrease in the following maintenance costs. The roller bearings used in conventional bridges are known to generate high costs both during construction and due to maintenance, and the possibility to remove these bearings and accompanying expansion joints are therefore investigated since several years. In Sweden, the absence of bridges built with integral abutments has made it difficult to test and evaluate this solution. In 2005, an international project called Intab was launched with the explicit aim to look at different solutions possible to use if joints and bearings are excluded. One of the most common discussed problems concerning bridges built without expansion joints is the accommodation of longitudinal elongation due to temperature variations. A bridge built with integral abutments is often supported by piles made of steel or concrete. The longitudinal elongation of the superstructure induces a displacement and a moment in these piles, which in time may cause a fatigue failure. Therefore it is of big interest to look at the amplitude of these strains. Within the Intab project, a pilot object was built in Nordmaling, ~50 km south of Umeå. It is a 40 meter long and 5 meter wide composite bridge with two steel girders and a concrete deck. The steel piles in this bridge is equipped with strain gauges who are used both for longterm and shortterm measurements. The sampled data from longterm measurement is collected on a computer on site, and then downloaded through a traditional modem. The data from the shortterm measurement is sampled and collected immediately during the test. The shortterm test is performed during both summer and winter conditions, and consists of a lorry passing the bridge while different measurements are done. The result from the measurement is also compared to calculations and a 2-D FE-model. It seems that short-term measurements performed during warmer months, May and October, show better agreement with the FE-simulations than the tests performed during the winter. The used FE-model is based on restrictions from Bro 2004. Regarding the long-term measurements, the obtained strain values are not in a range where fatigue can be considered as a severe problem.

  • 249.
    Bondarchuk, Alexander
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Rock mass behavior under hydropower embankment dams with focus on fracture erosion and rock mass stability2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In Sweden there are about 190 large hydropower dams of varying age. According to the definition by the International Commission of Large Dams (ICOLD), if the height of the dam exceeds 15 m it is referred as large. Majority of these dams are of embankment type. The peak of the dam construction in Sweden was between 1950 and 1980, hence, the major part of the dams are between 30 and 60 years old. It is well known that the strength of dam body and foundation rock deteriorates with time. For this reason there are ongoing concerns for the hydropower industry regarding the production and safety of the dams. Currently, the majority of research efforts are concentrated on degradation of hydropower dams whereas less attention is paid to the bedrock under the dam, which is a critical factor for construction integrity and functionality.This work is focused on:1. Better understanding of the rock mass response to the loads caused by construction and exploitation of a hydropower dam, i.e. the loads from the weight of the dam and the water in the reservoir;2. Validation of the developed conceptual model on the case study; 3. Investigation of how static and cyclic loads of the hydropower dam effect the fracture erosion and rock mass stability and grout curtain based on case study (in long-term perspective). An extensive literature review of this field is performed. Based on it a series of factors are selected which are important in terms of opening and shearing along geological structures under dams and reservoirs. Developed conceptual model together with numerical code UDEC (2D) helped to identify the most significant (stress conditions, structural geology and properties of discontinuities) conditions of the rock. The construction of a dam on rock foundation (with its water reservoir) causes redistribution of the stress field, and affects the state of mechanical and hydro-geological properties of the rock mass beneath the dam. The combination of sub-horizontal discontinuities (bankning discontinuities) with sub-vertical discontinuities, which are perpendicular to the river valley, give rise to a water leakage under the dam. This behavior depends on the direction of the dip angle of the sub-horizontal discontinuities, either downstream or upstream. The adverse effect is caused by downstream direction. Magnitude and direction of the in-situ stress field, density of discontinuities, and friction angle of joints are also major factors which affect the behavior of the rock mass considerably. All these findings are in good agreement with the results of other authors. As the developed numerical model showed good agreement with previous research it was adopted for a case study. Håckren dam (Sweden) had been selected for this purpose. A series of field (mapping, RMR, Q, GSI) and laboratory tests (Bulk density, Porosity, Water content, Point Load Strength index) were applied. Results of numerical models showed a good agreement with monitored leakage into the inspection gallery. The deformations within the foundation rock mass has not been monitored therefore numerical results has been evaluated based on the literature review. Results from the numerical models in terms of shear and normal deformations (openings) in the bedrock did not show significant deformations (around 1 mm for shear deformation and less than 0.1 mm in case of opening). Cyclic loading of the water in the reservoir results in accumulation of the deformations within the rock mass. Such processes may create favorable conditions for development of erosion within the bedrock. Numerical results showed an increase of accumulated shear deformations within the rock mass within the first years but then it stabilized. These deformations are occurring along subhorizontal discontinuities in downstream side of the dam and along intermediate joints on the upstream side. The magnitude of opening of the discontinuities is staying low, less than 0.3mm. The inflow into the inspection tunnel increased only during the first years, and then stabilized. However the flow velocity around the inspection tunnel showed a small increase along several simulated years. Numerical simulations showed the stability of the foundation rock of the Håckren dam after construction and within 10 idealized years of the exploitation of the dam. The used approached showed its validity and applicability for preliminary evaluation of the foundation rock of the embankment dams, based on the Håckren dam case.

  • 250. Bondarchuk, Alexander
    et al.
    Ask, Maria
    Dahlström, Lars-Olof
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical analysis of rock mass behavior under hydropower embankment dams2009In: Föredrag vid Bergmekanikdag i Stockholm 9 mars 2009, Stiftelsen bergteknisk forskning - Befo , 2009, p. 149-158Conference paper (Other academic)
    Abstract [sv]

    Numeriska analyser av bergmassans beteende under fyllningsdammar för vattenkraftproduktion

2345678 201 - 250 of 2233
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf