Change search
Link to record
Permanent link

Direct link
BETA
Ahmadi, Alireza
Publications (10 of 61) Show all publications
Soleimanmeigouni, I., Ahmadi, A., Arasteh Khouy, I. & Letot, C. (2018). Evaluation of the effect of tamping on the track geometry condition: a case study (ed.). Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, 232(2), 408-420
Open this publication in new window or tab >>Evaluation of the effect of tamping on the track geometry condition: a case study
2018 (English)In: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 232, no 2, p. 408-420Article in journal (Refereed) Published
Abstract [en]

Tamping is one of the major activities applied by railway maintenance managers to recover track geometry condition. Modelling the tamping effectiveness along with track geometry degradation is essential for long term prediction of track geometry behaviour. The aim of this study is to analyse theeffect of tamping on the different track geometry measures, i.e. longitudinal level, alignment and cant; on the basis of inspection car records from a part of Main Western Line in Sweden. To model recovery after tamping a probabilistic approach is applied. The track geometry condition before tamping was considered as the dominant factor for modelling the model parameters. Correlation analysis has performed to measure the linear relation between the recoveries of the different geometry measures. The results show a moderate correlation between the recovery of the longitudinal level and that of the cant, and a weak correlation between the recovery of the longitudinal level and that of the alignment. Linear regression and Wiener process are also applied to model track geometry degradation and to obtain degradation rates. Theeffect of tamping on degradation rate is analysed. It is observed that the degradation rate was increased after tamping intervention.  

Place, publisher, year, edition, pages
Sage Publications, 2018
National Category
Other Civil Engineering
Research subject
Operation and Maintenance
Identifiers
urn:nbn:se:ltu:diva-15883 (URN)10.1177/0954409716671548 (DOI)000424780200006 ()f7391512-a026-4e7c-a4d0-96223a5957dd (Local ID)f7391512-a026-4e7c-a4d0-96223a5957dd (Archive number)f7391512-a026-4e7c-a4d0-96223a5957dd (OAI)
Note

Validerad;2018;Nivå 2;2018-02-12 (svasva)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-06-28Bibliographically approved
Soleimanmeigouni, I., Xiao, X., Ahmadi, A., Xie, M., Nissen, A. & Kumar, U. (2018). Modelling the evolution of ballasted railway track geometry by a two-level piecewise model. Structure and Infrastructure Engineering, 14(1), 33-45
Open this publication in new window or tab >>Modelling the evolution of ballasted railway track geometry by a two-level piecewise model
Show others...
2018 (English)In: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 14, no 1, p. 33-45Article in journal (Refereed) Published
Abstract [en]

Accurate prediction and efficient simulation of the evolution of track geometry condition is a prerequisite for planning effective railway track maintenance. In this regard, the degradation and tamping effect should be equipped with proper and efficient probabilistic models. The possible correlation induced by the spatial structure also needs to be taken into account when modelling the track geometry degradation. To address these issues, a two-level piecewise linear model is proposed to model the degradation path. At the first level, the degradation characteristic of each track section is modelled by a piecewise linear model with known break points at the tamping times. At the second level, Autoregressive Moving Average models are used to capture the spatial dependences between the parameters of the regression lines indexed by their locations. To illustrate the model, a comprehensive case study is presented using data from the Main Western Line in Sweden

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Other Civil Engineering
Research subject
Operation and Maintenance
Identifiers
urn:nbn:se:ltu:diva-63815 (URN)10.1080/15732479.2017.1326946 (DOI)000415674800003 ()2-s2.0-85019663898 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-11-01 (andbra)

Available from: 2017-06-09 Created: 2017-06-09 Last updated: 2018-06-28Bibliographically approved
Mahmood, Y. A., Garmabaki, A., Ahmadi, A. & Verma, A. K. (2018). Reliability model for frequency converter in electrified railway. International Journal of Electrical Power & Energy Systems, 94, 385-392
Open this publication in new window or tab >>Reliability model for frequency converter in electrified railway
2018 (English)In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 94, p. 385-392Article in journal (Refereed) Published
Abstract [en]

Reliability analysis of frequency converters based on failures and outages reports constitute an important basis for asset performance and management. Two- and four-state reliability models that recognize the operating characteristics of base load units and peaking units are presented and compared in this study. In this study, a four-state model is modified to a three-state model by combining the ‘needed’ and ‘not-needed’ forced-out states. Moreover, the transitions in the three-state model for power frequency converter have been designed according to real operational data. An outage-reporting database modelled considering IEEE STD 762 is presented and compared with the existing failure-reporting database of the case considered here. Furthermore, a method to extract information missing in the failure-reporting database by electrical readings is proposed to meet the requirements of the outage-reporting database. The study found that the results of indexes based on the IEEE four-state model are not reasonable for the frequency converter given their differences with the gas-turbine results under operational conditions. The forced outage rates and availability factors of twelve actual traction frequency converters of Swedish railways network are presented to validate the modified model.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Outage-data reporting system, Unit state reliability model, IEEE STD 762, Frequency converter
National Category
Reliability and Maintenance Other Civil Engineering
Research subject
Operation and Maintenance
Identifiers
urn:nbn:se:ltu:diva-65173 (URN)10.1016/j.ijepes.2017.08.002 (DOI)000412610000035 ()2-s2.0-85027709160 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-08-17 (rokbeg)

Available from: 2017-08-17 Created: 2017-08-17 Last updated: 2018-05-07Bibliographically approved
Soleimanmeigouni, I., Ahmadi, A. & Kumar, U. (2018). Track geometry degradation and maintenance modelling: A review (ed.). Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, 232(1), 73-102
Open this publication in new window or tab >>Track geometry degradation and maintenance modelling: A review
2018 (English)In: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 232, no 1, p. 73-102Article in journal (Refereed) Published
Abstract [en]

Increased demand for railway transportation is creating a need for higher train speeds and axle loads. These, in turn,increase the likelihood of track degradation and failures. Modelling the degradation behaviour of track geometry anddevelopment of applicable and effective maintenance strategies has become a challenging concern for railway infrastructuremanagers. During the last three decades, a number of track geometry degradation and maintenance modellingapproaches have been developed to predict and improve the railway track geometry condition. In this paper, existingtrack geometry measures are identified and discussed. Available models for track geometry degradation are reviewedand classified. Tamping recovery models are also reviewed and discussed to identify the issues and challenges of differentavailable methodologies and models. Existing track geometry maintenance models are reviewed and critical observationson each contribution are provided. The most important track maintenance scheduling models are identified and discussed.Finally, the paper provides directions for further research.

Place, publisher, year, edition, pages
Sage Publications, 2018
National Category
Other Civil Engineering
Research subject
Operation and Maintenance
Identifiers
urn:nbn:se:ltu:diva-14797 (URN)10.1177/0954409716657849 (DOI)000419833100006 ()2-s2.0-85040348348 (Scopus ID)e3794ef4-cb25-49e0-b55c-a579ff2ea6f5 (Local ID)e3794ef4-cb25-49e0-b55c-a579ff2ea6f5 (Archive number)e3794ef4-cb25-49e0-b55c-a579ff2ea6f5 (OAI)
Note

Validerad;2018;Nivå 2;2018-01-18 (svasva)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-06-28Bibliographically approved
Pourgol-Mohammad, M., Hejaz, A., Ghasemi, P., Ahmadi, A. & Jalali-Vahid, D. (2017). Design for reliability of automotive systems: case study of dry friction clutch. International Journal of Systems Assurance Engineering and Management, 8(3), 572-583
Open this publication in new window or tab >>Design for reliability of automotive systems: case study of dry friction clutch
Show others...
2017 (English)In: International Journal of Systems Assurance Engineering and Management, ISSN 0975-6809, E-ISSN 0976-4348, Vol. 8, no 3, p. 572-583Article in journal (Refereed) Published
Abstract [en]

Design and production of highly reliable and safer automotive systems with longer life has been a challenge. The pressure is outcome of high competitive market and recent safety issues of reputable car manufacturers. In this paper, an integrated methodology is proposed based on design for reliability of automotive systems and considering its reliability/safety critical sub-systems. In the proposed approach, the FMEA results are used in the process of failure mode/mechanism identification. The basic failure data, mostly obtained from generic databases, are adjusted by multiplicative corrective factors to account for the design and environment impacts on system failure characteristics. The system is modeled by reliability block diagram method, simulated by Monte Carlo technique. The results of FMEA and reliability evaluation are used for system improvement by reducing the components’ failure rates and potential change of system configuration. The components’ reliability is improved by increasing the quality of components by utilization of high quality materials and modern manufacturing techniques. Modification of system configuration, e.g., adding redundancy, is an alternative for system reliability improvement in some cases. The results show that the friction lining component is the most critical elements in terms of reliability importance. After completion of this phase, an assessment is done for system reliability by comparing the system reliability targets. As a case study, dry friction clutch is studied for assessment of the proposed method. In this study, the life test requirement is researched for each component using a reliability testing techniques. Finally, the uncertainties are computed associated with the failure data and final reliability estimations and the results were presented with a confidence interval.

Place, publisher, year, edition, pages
Springer, 2017
National Category
Other Civil Engineering
Research subject
Operation and Maintenance
Identifiers
urn:nbn:se:ltu:diva-65581 (URN)10.1007/s13198-017-0644-2 (DOI)000410268700006 ()2-s2.0-85029228563 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-09-11 (andbra)

Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2018-09-14Bibliographically approved
Ahmadi, A., Soleimanmeigouni, I., Letot, C. & Block, J. (2017). Inspection Optimization under imperfect maintenance performance. In: Diego Galar, Dammika Seneviratne (Ed.), Proceedings of MPMM 2016: 6th International Conference on Maintenance Performance Measurement and Management, 28 November 2016, Luleå, Sweden. Paper presented at Maintenance Performance and Measurement and Management 2016(MPMM 2016). November 28, Luleå, Sweden (pp. 139-). Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Inspection Optimization under imperfect maintenance performance
2017 (English)In: Proceedings of MPMM 2016: 6th International Conference on Maintenance Performance Measurement and Management, 28 November 2016, Luleå, Sweden / [ed] Diego Galar, Dammika Seneviratne, Luleå: Luleå tekniska universitet, 2017, p. 139-Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Scheduled maintenance and inspection development is one of the main requirements for emergency equipment and safety devices. These types of devices have hidden functions which are used intermittently or infrequently, so their failure will not be evident to the operating crew. The analytical model presented in this paper deals with the periodically tested units with overhauls (preventive maintenance) after certain number of inspections and a renewal after a series of overhauls. The cost based optimization method presented in this paper identifies the optimum interval and frequency of Failure Finding Inspection (FFI) and restoration. In the proposed model, repair due to failures found by inspection makes the unit As Bad As Old, and restoration/overhaul action rejuvenates the unit to any condition between As Good As New and As Bad As Old. As Good As New effectiveness also is considered for renewal action. It considers inspection and repair times, and takes into account the costs associated with inspection, repair, restoration, and also the cost of accidents due to the occurrence of multiple failure. The results show that when the unit is not under aging process, the optimal alternative for each inspection interval is the one with highest possible number of inspection without restoration. Finally, it is observed that when the cost of accident is quite high it is needed to perform inspections at smaller intervals to control the risk of accident.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2017
National Category
Other Civil Engineering
Research subject
Operation and Maintenance
Identifiers
urn:nbn:se:ltu:diva-63893 (URN)978-91-7583-841-0 (ISBN)
Conference
Maintenance Performance and Measurement and Management 2016(MPMM 2016). November 28, Luleå, Sweden
Available from: 2017-06-12 Created: 2017-06-12 Last updated: 2018-06-28Bibliographically approved
Lopes, J. C. .., Scarpel, R., Abrahão, F. T. .., Galar, D. & Ahmadi, A. (2017). Optmization In Performance-Based Logistics Contracts. In: Diego Galar, Dammika Seneviratne (Ed.), Proceedings of MPMM 2016: 6th International Conference on Maintenance Performance Measurement and Management, 28 November 2016, Luleå, Sweden. Paper presented at Maintenance Performance and Measurement and Management 2016(MPMM 2016). November 28, Luleå, Sweden (pp. 133-138). Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Optmization In Performance-Based Logistics Contracts
Show others...
2017 (English)In: Proceedings of MPMM 2016: 6th International Conference on Maintenance Performance Measurement and Management, 28 November 2016, Luleå, Sweden / [ed] Diego Galar, Dammika Seneviratne, Luleå: Luleå tekniska universitet, 2017, p. 133-138Conference paper, Published paper (Refereed)
Abstract [en]

Performance-based    Logistics    (PBL)    contracts    require  metrics  and  methodologies  set  in  a  systemic  way  to  provide  readiness  for  the  warfighter  at  reasonable  costs.  There  must be a clever and verifiable connection of metrics in order to access  and  analyze  data and  to  deliver  sound  and  consistent  inputs  for  the  entire  support  system  to  accomplish  its  goals.    A  system   of   incentives   and   penalties   usually   takes   place   and   suggests  functions  to  be  maximized  and/or  minimized  in  a  multi-criterion  and  highly  integrated  environment.  This  study  deals  with  the  optimization  of  the  entire  setup  of  Performance-Based Logistics  contracts  and  is  limited  to  a  preliminary  study  in  a  simple  scenario  that  has  showed  a  promises  results.    A  mixed  method, using both the Ɛ-Constraint  and    Goal  Programming  is  proposed to model the case. Results indicate that metrics used for reliability,    maintainability,    availability    and    supportability    (RAMS)  and  costs  can  be  optimized  simultaneously  for  clever  contracts.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2017
National Category
Other Civil Engineering
Research subject
Operation and Maintenance
Identifiers
urn:nbn:se:ltu:diva-63875 (URN)978-91-7583-841-0 (ISBN)
Conference
Maintenance Performance and Measurement and Management 2016(MPMM 2016). November 28, Luleå, Sweden
Available from: 2017-06-12 Created: 2017-06-12 Last updated: 2017-11-24Bibliographically approved
Pourgol-Mohammad, M. & Ahmadi, A. (2017). Special issue of IREC2016 conference selected papers. Paper presented at 4th International Reliability Engineering Conference (IREC2016) held in Tabriz, Iran, on May 2–4, 2016. International Journal of Systems Assurance Engineering and Management, 8(3), 529-531
Open this publication in new window or tab >>Special issue of IREC2016 conference selected papers
2017 (English)In: International Journal of Systems Assurance Engineering and Management, ISSN 0975-6809, E-ISSN 0976-4348, Vol. 8, no 3, p. 529-531Article in journal, Editorial material (Other academic) Published
Place, publisher, year, edition, pages
Springer, 2017
National Category
Other Civil Engineering
Research subject
Operation and Maintenance
Identifiers
urn:nbn:se:ltu:diva-65421 (URN)10.1007/s13198-017-0662-0 (DOI)000410268700001 ()2-s2.0-85029211751 (Scopus ID)
Conference
4th International Reliability Engineering Conference (IREC2016) held in Tabriz, Iran, on May 2–4, 2016
Available from: 2017-08-30 Created: 2017-08-30 Last updated: 2018-07-10Bibliographically approved
Garmabaki, A., Ahmadi, A., Block, J., Pham, H. & Kumar, U. (2016). A Reliability Decision Framework for Multiple Repairable Units (ed.). Paper presented at . Reliability Engineering & System Safety, 150, 78-88
Open this publication in new window or tab >>A Reliability Decision Framework for Multiple Repairable Units
Show others...
2016 (English)In: Reliability Engineering & System Safety, ISSN 0951-8320, E-ISSN 1879-0836, Vol. 150, p. 78-88Article in journal (Refereed) Published
Abstract [en]

In practice, the analyst is often dealing with multiple repairable units, installed in different positions or functioning under different operating conditions, and maintained by different disciplines. This paper presents a decision framework to identify an appropriate reliability model for massive multiple repairable units. It splits non-homogeneous failure data into homogeneous groups and classifies them based on their failure trends using statistical tests. The framework discusses different scenarios for analysing multiple repairable units, according to trend, intensity, and dependency of the units’ failure data. The proposed framework has been verified in a fleet of aircraft and in two simulated data sets. The results show a reliability model of multiple repairable units may contain a mixture of different stochastic models. Considering single reliability models for such populations may cause erroneous calculation of the time to failure of a particular unit, which can, in turn, lead to faulty conclusions and decisions. When dealing with massive and non-homogeneous multiple repairable units, the application of the proposed framework can facilitate the selection of an appropriate reliability model.

National Category
Other Civil Engineering
Research subject
Operation and Maintenance
Identifiers
urn:nbn:se:ltu:diva-16337 (URN)10.1016/j.ress.2016.01.020 (DOI)000373553800008 ()2-s2.0-84957998942 (Scopus ID)ff71273c-c01e-473a-8fbf-892f4c195fe4 (Local ID)ff71273c-c01e-473a-8fbf-892f4c195fe4 (Archive number)ff71273c-c01e-473a-8fbf-892f4c195fe4 (OAI)
Note
Validerad; 2016; Nivå 2; 20160204 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Soleimanmeigouni, I. & Ahmadi, A. (2016). A Survey on Track Geometry Degradation Modelling (ed.). In: (Ed.), Uday Kumar; Alireza Ahmadi; Ajit Kumar Verma; Prabhakar Varde (Ed.), Current Trends in Reliability, Availability, Maintainability and Safety: An Industry Perspective. Paper presented at International Conference ICRESH-ARMS 2015 : 01/06/2015 - 04/06/2015 (pp. 3-12). : Encyclopedia of Global Archaeology/Springer Verlag
Open this publication in new window or tab >>A Survey on Track Geometry Degradation Modelling
2016 (English)In: Current Trends in Reliability, Availability, Maintainability and Safety: An Industry Perspective / [ed] Uday Kumar; Alireza Ahmadi; Ajit Kumar Verma; Prabhakar Varde, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 3-12Conference paper, Published paper (Refereed)
Abstract [en]

Railway transportation is exposed to a higher demand that necessitates the use of trains with higher speed and heavier axle loads. These increase the track geometry degradation rate, which needs a more effective control on geometry degradation. Keeping the track geometry in acceptable levels requires proper inspection and maintenance planning that inevitably entails in-depth knowledge of track geometry degradation. In addition, it is needed to identify the most effective approach for degradation modelling. To do so, it is vital to synthesis published results into a summary of what is known and validated and what is not as a major step. To this end, this paper reviews track degradation models, discusses various degradation measures, and proposes directions for future researches. It is found that combining the mechanistic and statistical approaches can leads to a more accurate prediction of track geometry degradation behaviour.

Place, publisher, year, edition, pages
Encyclopedia of Global Archaeology/Springer Verlag, 2016
Series
Lecture Notes in Mechanical Engineering, ISSN 2195-4356
National Category
Other Civil Engineering
Research subject
Operation and Maintenance
Identifiers
urn:nbn:se:ltu:diva-27387 (URN)10.1007/978-3-319-23597-4_1 (DOI)0d35d95c-b94f-41cf-923e-ede84f670870 (Local ID)978-3-319-23596-7 (ISBN)978-3-319-23597-4 (ISBN)0d35d95c-b94f-41cf-923e-ede84f670870 (Archive number)0d35d95c-b94f-41cf-923e-ede84f670870 (OAI)
Conference
International Conference ICRESH-ARMS 2015 : 01/06/2015 - 04/06/2015
Note
Godkänd; 2016; Bibliografisk uppgift: Containing selected papers from the ICRESH-ARMS 2015 conference in Lulea, Sweden, collected by editors with years of experiences in Reliability and maintenance modeling, risk assessment, and asset management, this work maximizes reader insights into the current trends in Reliability, Availability, Maintainability and Safety (RAMS) and Risk Management. Featuring a comprehensive analysis of the significance of the role of RAMS and Risk Management in the decision making process during the various phases of design, operation, maintenance, asset management and productivity in Industrial domains, these proceedings discuss key issues and challenges in the operation, maintenance and risk management of complex engineering systems and will serve as a valuable resource for those in the field. ; 20151222 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-06-28Bibliographically approved
Organisations

Search in DiVA

Show all publications