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  • 1.
    Ahmer, Muhammad
    et al.
    AB SKF, Gothenburg, Sweden.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Gustafsson, Martin
    AB SKF, Gothenburg, Sweden.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    A unified approach towards performance monitoring and condition-based maintenance in grinding machines2020Conference paper (Refereed)
    Abstract [en]

    The process controller in a precision grinder for bearing rings puts high performance demands on the machine to achieve desired quality in production. This paper presents a unique approach of adding additional sensors for machine condition monitoring for the purpose of learning and using high fidelity condition indicators. The consolidation of real-time sensor data and the process control signals yields high-dimensional dataset. Automatic segmentation helps optimize the amount of data for processing and data mining ahead of fault diagnosis. The proposed setup is state of the art for prognostics as part of condition-based maintenance in a production machine.

  • 2.
    Ahmer, Muhammad
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. AB SKF, Gothenburg, Sweden.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Gustafsson, Martin
    AB SKF, Gothenburg, Sweden.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    An implementation framework for condition-based maintenance in a bearing ring grinder2022In: Leading manufacturing systems transformation – Proceedings of the 55th CIRP Conference on Manufacturing Systems 2022 / [ed] Emanuele Carpanzano, Claudio Boër, Anna Valente, Elsevier, 2022, Vol. 107, p. 746-751Conference paper (Refereed)
    Abstract [en]

    The demand on a bearing ring grinder, as any other machine tool, is to produce parts as per the specification and desired quality. A failure to achieve the quality can be due to functional issues or mechanical failure modes. Ultimately this results in lower productivity and higher production costs. Despite the increased emphasis on practicing condition-based machine maintenance (CBM) in manufacturing applications, it is still considered a challenge to fully deploy CBM in production machines due to diversity in equipment and variety in machine configurations as well as complex characteristics of failure modes. Although there exists extensive literature on CBM for machine tools and subsystems, the issue remains with realization of a technically capable and cost effective CBM system, specifically for a bearing ring grinder. Therefore, sensor(s) selection, data acquisition setup, data processing and analysis are the essential factors considered in the proposed framework to ensure a systematic and organized CBM implementation. The CBM setup is evaluated against production of bearing rings under different process and failure conditions. A machine type independent data acquisition system is designed to capture both machine and process dynamics. The data gathered from sensors at strategic locations exhibits its effectiveness in capturing the process and condition variations in relation to time and operating modes. The presented results of data analysis support the capability and effectiveness of the proposed framework. The utility of this framework can be extended for any number of scenarios including predictive maintenance or adaptive process optimization where solutions using machine learning and artificial intelligence tools can benefit from high dimensional structured dataset. The proposed framework provides a strong foundation to fast track the adaption of CBM in other production machines having similar subsystems.

  • 3.
    Ahmer, Muhammad
    et al.
    AB SKF, Gothenburg, Sweden.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Gustafsson, Martin
    AB SKF, Gothenburg, Sweden.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Integration of process monitoring and machine condition diagnostics to improve quality prediction in grinding2021In: 9th CIRP Conference on High Performance Cutting / [ed] Erdem Ozturk; David Curtis; Hassan Ghadbeigi, Elsevier, 2021, p. 170-173Conference paper (Refereed)
    Abstract [en]

    Bearing ring grinding incorporates sensors to control the grinding cycle in real time. Prediction of output quality is difficult due to the complex combination of process settings and machine characteristics. Causal relationship of machine performance with varying operating conditions was studied with reference to the produced quality by adding condition monitoring setup to the machine. Data driven diagnostics of machine condition through integration of condition and process monitoring sensor data at the completion of the grinding cycle improves quality cognisance. This can be used to tune control parameters to achieve more predictable quality in successive cycles.

  • 4.
    Ahmer, Muhammad
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. AB SKF, Gothenburg, Sweden.
    Sandin, Fredrik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Gustafsson, Martin
    AB SKF, Gothenburg, Sweden.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Dataset Concerning the Process Monitoring and Condition Monitoring Data of a Bearing Ring Grinder2022Data set
    Abstract [en]

    In the manuscript, we have investigated the effective use of sensors in a bearing ring grinder for failure classification in the condition-based maintenance context. The proposed methodology combines domain knowledge of process monitoring and condition monitoring to successfully achieve failure mode prediction with high accuracy using only a few key sensors. This enables manufacturing equipment to take advantage of advanced data processing and machine learning techniques.

    The grinding machine is of type SGB55 from Lidköping Machine Tools and is used to produce functional raceway surface of inner rings of type SKF-6210 deep groove ball bearing. Additional sensors like vibration, acoustic emission, force, and temperature sensors are installed to monitor machine condition while producing bearing components under different operating conditions. Data is sampled from sensors as well as the machine's numerical controller during operation. Selected parts are measured for the produced quality.

  • 5.
    Ahmer, Muhammad
    et al.
    Manufacturing and Process Development, AB SKF, Gothenburg, Sweden.
    Sandin, Fredrik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Gustafsson, Martin
    Manufacturing and Process Development, AB SKF, Gothenburg, Sweden.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Failure mode classification for condition-based maintenance in a bearing ring grinding machine2022In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 122, p. 1479-1495Article in journal (Refereed)
    Abstract [en]

    Technical failures in machines are major sources of unplanned downtime in any production and result in reduced efficiency and system reliability. Despite the well-established potential of Machine Learning techniques in condition-based maintenance (CBM), the lack of access to failure data in production machines has limited the development of a holistic approach to address machine-level CBM. This paper presents a practical approach for failure mode prediction using multiple sensors installed in a bearing ring grinder for process control as well as condition monitoring. Bearing rings are produced in a set of 7 experimental runs, including 5 frequently occurring production failures in the critical subsystems. An advanced data acquisition setup, implemented for CBM in the grinder, is used to capture information about each individual grinding cycle. The dataset is pre-processed and segmented into grinding cycle stages before time and frequency domain feature extraction. A sensor ranking algorithm is proposed to optimize feature selection for failure classification and the installation cost. Random forest models, benchmarked as best performing classifiers, are trained in a two-step classification framework. The presence of failure mode is predicted in the first step and the failure mode type is identified in the second step using the same feature set. Defining the feature set in the failure detection step improves the predictor generalization with the classifiers’ performance accuracy of 99%99% on the test dataset. The presented approach demonstrates an efficient failure mode classification by selecting crucial sensors resulting in a cost-effective CBM implementation in a bearing ring grinder.

  • 6.
    Ahmer, Muhammad
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Manufacturing and Process Development, AB SKF, 415 50 Gothenburg, Sweden.
    Sandin, Fredrik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Gustafsson, Martin
    Manufacturing and Process Development, AB SKF, 415 50 Gothenburg, Sweden.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Using Multivariate Quality Statistic for Maintenance Decision Support in a Bearing Ring Grinder2022In: Machines, E-ISSN 2075-1702, Vol. 10, no 9, article id 794Article in journal (Refereed)
    Abstract [en]

    Grinding processes’ stochastic nature poses a challenge in predicting the quality of the resulting surfaces. Post-production measurements for form, surface roughness, and circumferential waviness are commonly performed due to infeasibility in measuring all quality parameters during the grinding operation. Therefore, it is challenging to diagnose the root cause of quality deviations in real-time resulting from variations in the machine’s operating condition. This paper introduces a novel approach to predict the overall quality of the individual parts. The grinder is equipped with sensors to implement condition-based maintenance and is induced with five frequently occurring failure conditions for the experimental test runs. The crucial quality parameters are measured for the produced parts. Fuzzy c-means (FCM) and Hotelling’s T-squared (T2) have been evaluated to generate quality labels from the multi-variate quality data. Benchmarked random forest regression models are trained using fault diagnosis feature set and quality labels. Quality labels from the T2 statistic of quality parameters are preferred over FCM approach for their repeatability. The model, trained from T2 labels achieves more than 94% accuracy when compared to the measured ring disposition. The predicted overall quality using the sensors’ feature set is compared against the threshold to reach a trustworthy maintenance decision.

  • 7.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction characteristics of environmentally adapted lubricants in boundary lubricated contacts2017Conference paper (Other academic)
    Download full text (pdf)
    fulltext
  • 8.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Predicting wet clutch service life performance2013Doctoral thesis, comprehensive summary (Other academic)
    Download full text (pdf)
    FULLTEXT01
  • 9.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Sustainable performance of wet clutch systems2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In industry today there are increasing demands not only on product performance, but also on environmental performance. In striving to develop high performance environmentally adapted products, optimization of product life is a central issue. The success of design optimization relies on an understanding of the degradation process and of the associated degradation mechanisms. A high level of costs is often associated with downtime of machinery caused by service and by replacement of machine components. Knowledge of ageing mechanisms facilitates evaluation of the remaining useful life, thus optimizing performance during the entire service life of components. In this study the ageing process of wet clutches has been investigated. Wet clutches are used in automatic transmissions and limited slip differentials in private vehicles and are designed to transfer torque. A wet clutch consists of a clutch pack submerged in lubricant. Separator and friction discs are alternately positioned in the clutch pack. The separator discs are connected to the input shaft and the friction discs are connected to the output shaft. When the clutch pack is pushed together friction is generated between the friction and separator discs. Torque transfer is thus created in the interface between contacting surfaces and torque transfer characteristics are determined by the interaction between lubricant and contacting surfaces. The investigations performed in this thesis have been designed to increase the understanding of wet clutch ageing and failure. Tests have been performed from full scale to model tests. Full scale testing describes the actual system which means that all significant degradation mechanisms are present. The disadvantage with full scale testing is that it is difficult to separate and isolate degradation mechanisms. In small scale model tests it is possible to isolate the degradation mechanisms and hence also what effects they have. Correlation of results from full scale to small scale can in turn increase the understanding of which degradation mechanisms are important for the system and how they influence the wet clutch system. The wet clutch lubricant and the contacting surfaces provide the friction characteristics of the clutch. Therefore, this work has focused on how lubricant degradation affects friction characteristics and hence wet clutch performance. Results in this study show that friction levels increase as lubricant degradation proceeds. In accelerated wet clutch test rig ageing, results in this study indicate that high temperatures in the interface between contacting surfaces greatly influence wet clutch degradation.

    Download full text (pdf)
    FULLTEXT01
  • 10.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Emadi, Seyedehmaryam
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lubricant Maintenance Based on Condition Monitoring2016In: STLE 2016 Annual Meeting and Exhibition, 2016Conference paper (Refereed)
  • 11. Berglund, Kim
    et al.
    Larsson, Roland
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lubricant ageing effects on wet clutch friction characteristics2009Conference paper (Refereed)
  • 12.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Larsson, Roland
    Lubricant ageing effects on the friction characteristics of wet clutches2010In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 224, no 7, p. 639-647Article in journal (Refereed)
    Abstract [en]

    The friction characteristics and performance of wet clutches have been investigated by several authors. Studies have also been made to understand the frictional performance during the service life of the clutch system. However, most lifetime studies have been conducted for systems with paper-based friction material so that systems using sintered bronze friction material remain largely unexplored. To study the friction performance of how these systems can vary over time, the friction characteristics for a clutch system using lubricants aged in three different ways were compared. The effects on friction characteristics resulting from oxidation of the lubricant, reduced additive concentration, and ageing under real operating conditions in a wet clutch test rig were studied. The oxidation effects on friction characteristics were examined using a modified waterless turbine oil oxidation stability test on a fully formulated lubricant. Five oxidation time periods from 48 to 408 h were investigated. For each period of oxidation, a friction performance test was run using a pin-on-disc machine. The ageing carried out in a wet clutch test rig is a standard test of a wet clutch systems manufacturer which is used in order to verify that an oil-friction disc combination will last the full service life of the specific application. This test gives a realistic ageing process similar to that in a wet clutch in a field test. Under boundary-lubricated conditions, additives are vital to the performance of wet clutches. Therefore, the effect of reducing the additive concentration in the oil was also studied, in the range of 10 to 100 per cent of the original additive package used in the fully formulated wet clutch lubricant. Results showed that a general friction increase can be observed for oxidation, additive reduction, and test rig ageing. It was also concluded that different methods of simulating the wet clutch ageing process differ and cannot be directly correlated with each other

  • 13.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Olsson, Richard
    Borgwarner TTS.
    Evaluating lifetime performance of limited slip differentials2014In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 26, no 3, p. 189-201Article in journal (Refereed)
    Abstract [en]

    Extensive research has been performed regarding wet clutch function and performance. Although wet clutches are used in both automatic transmissions and limited slip differentials in cars, most research has been performed for wet clutches incorporated in automatic transmissions. The operating conditions of wet clutches in automatic transmissions differ from the operating conditions of the wet clutches used in limited slip differentials. Therefore, a method and a test bench to use in the investigation of the degradation of limited slip differentials were developed in this work. The typical operating conditions of the limited slip differential and the differences compared with wet clutches incorporated in automatic transmissions were also addressed. Tests performed showed that the developed test bench and method can be used to address differences in frictional response over time for different types of operating condition

  • 14.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Olsson, Richard
    BorgWarner TorqTransfer Systems, Landskrona, SE-26151, Sweden.
    Predicting boundary friction of aging limited slip differentials2014In: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 137, no 1, article id 012101Article in journal (Refereed)
    Abstract [en]

    The prediction of friction is a challenge for scientists and engineers in a wide variety of applications in industry today. One such an application is the limited slip differential. The friction characteristics of the wet clutch are central to the performance of the limited slip differential system. Frictional changes with aging of the limited slip differential affect both the torque transfer accuracy and the tendencies to vibrations and noise generation due to stick-slip or shudder. Therefore, the objective of this work is to establish a method to predict the frictional changes of aging limited slip differential systems. In this study, a number of experiments were performed to establish a method to predict the changes in boundary friction with time due to aging. Accelerated aging was performed for different sets of operating conditions. Results from the tests were used to establish and verify a model to predict friction increase in limited slip differentials. The method assumes that frictional changes with aging are caused by decreased concentrations of friction modifying additives. The decrease in concentration was assumed to depend on the lubricant bulk temperature according to the Arrhenius equation. The model agreed well with tests performed at operating conditions close to the real operating conditions of the limited slip differential. The developed method can be implemented in a vehicle where it can be used to compensate for frictional changes and to indicate when service should be made.

  • 15.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Larsson, Roland
    Pach, Mayte
    Statoil Lubricants R&D.
    Olsson, Richard
    Haldex Traction AB.
    Wet clutch degradation monitored by lubricant analysis2010In: SAE technical paper series, ISSN 0148-7191, no 2010-01-2232Article in journal (Refereed)
    Abstract [en]

    In the competitive market of the car industry today, companies need to continuously strive to optimize the performance, price and environmental properties of their products in order to survive. Wet clutches, as parts of transmission components of passenger cars are no exception. An understanding of how the wet clutch system functions and fails is necessary to optimize price and service life. The friction characteristics of the wet clutch system are determined by lubricant-surface interactions in the contact between the friction discs. Wet clutch failure can often be associated with the deterioration of friction characteristics which eventually leads to stick-slip or shudder. Consequently, knowledge of why and of how friction characteristics change over time is of the outermost significance to enable the understanding and prediction of wet clutch performance. As the lubricant is an essential component of the wet clutch system, lubricant ageing is a factor of importance. Oxidation, thermal degradation, shearing, additive degradation and water contamination could all be considered to influence lubricant ageing. The aim of this work was therefore to find suitable ways of measuring the remaining useful life of wet clutch lubricants and to correlate changes in friction characteristics with changes in lubricant properties. Both field trials and measurements in a wet clutch test rig were performed. Viscosity, acid number, additive degradation, water contamination, particle content and metal content were measured for the lubricant as it degraded. Particle content results showed a rapid increase early in the ageing process. However, as ageing progressed particle levels actually decreased and this was probably a result of particles slowly grinded between contacting surfaces. On the other hand, metal content increased as ageing progressed, which could indicate slowly progressing wear. Water levels were found to be higher in field trials than in lubricants used in wet clutch test rigs. It is concluded that this was due to the severe and accelerated operating conditions of the wet clutch test rig.

  • 16.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Larsson, Roland
    Pach, Mayte
    Statoil Lubricants R&D.
    Olsson, Richard
    Haldex Traction AB.
    Wet clutch degradation monitored by lubricant analysis2010In: SAE 2010 Powertrains, Fuels and Lubricants Meeting: October 25 - 27, 2010, San Diego, California, USA ; [papers], Warrendale, Pa: Society of Automotive Engineers, Incorporated , 2010Conference paper (Other academic)
    Abstract [en]

    In the competitive market of the car industry today, companies need to continuously strive to optimize the performance, price and environmental properties of their products in order to survive. Wet clutches, as parts of transmission components of passenger cars are no exception. An understanding of how the wet clutch system functions and fails is necessary to optimize price and service life. The friction characteristics of the wet clutch system are determined by lubricant-surface interactions in the contact between the friction discs. Wet clutch failure can often be associated with the deterioration of friction characteristics which eventually leads to stick-slip or shudder. Consequently, knowledge of why and of how friction characteristics change over time is of the outermost significance to enable the understanding and prediction of wet clutch performance. As the lubricant is an essential component of the wet clutch system, lubricant ageing is a factor of importance. Oxidation, thermal degradation, shearing, additive degradation and water contamination could all be considered to influence lubricant ageing. The aim of this work was therefore to find suitable ways of measuring the remaining useful life of wet clutch lubricants and to correlate changes in friction characteristics with changes in lubricant properties. Both field trials and measurements in a wet clutch test rig were performed. Viscosity, acid number, additive degradation, water contamination, particle content and metal content were measured for the lubricant as it degraded. Particle content results showed a rapid increase early in the ageing process. However, as ageing progressed particle levels actually decreased and this was probably a result of particles slowly grinded between contacting surfaces. On the other hand, metal content increased as ageing progressed, which could indicate slowly progressing wear. Water levels were found to be higher in field trials than in lubricants used in wet clutch test rigs. It is concluded that this was due to the severe and accelerated operating conditions of the wet clutch test rig.

  • 17.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lundh, Henrik
    BorgWarner TorqTransfer Systems, Landskrona.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prediction of driveline vibrations caused by ageing the limited slip coupling2016In: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 230, no 12, p. 1687-1698Article in journal (Refereed)
    Abstract [en]

    The prediction of the wet-clutch service life still remains a challenge for scientists and engineers. Previous research has shown the significance of the wet-clutch friction characteristics on the driveline dynamics. To avoid driveline vibrations an increasing friction coefficient with increasing sliding speed is desirable. Consequently, prediction of the occurrence of driveline vibrations relies on a detailed knowledge of how the friction characteristics are affected by wet-clutch degradation, as well as an understanding of the driveline dynamics. Wet clutches are used in both automatic transmissions and all-wheel-drive systems in cars, where they are referred to as limited slip couplings by manufacturers. Wet clutches used in automatic transmissions are subjected to high slip levels, but for very limited time periods. In all-wheel-drive systems, where the limited slip coupling can be used to control the torque transfer to, for example, the rear wheels, the slip levels are low but continuous. Most wet-clutch research has been performed for clutches in automatic transmissions and not for clutches used in all-wheel-drive systems. Thus, a simulation model was developed to evaluate how different operating conditions of the limited slip coupling influence degradation of the friction characteristics and the tendencies towards driveline vibrations. First, the changes in the friction characteristics with the time of ageing are simulated. The friction characteristics after ageing are used as the input to a simplified driveline model, which is used to evaluate the occurrence of vibrations. It is shown how the developed simulation model can be used as an efficient tool for engineers. The developed simulation model can be used to predict how the operating conditions for the limited slip coupling influence degradation of the friction characteristics.

  • 18.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Rodiouchkina, Maria
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Kalliorinne, Kalle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Johansson, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    A novel reciprocating tribometer for friction and wear measurements with high contact pressure and large area contact configurations2021In: Lubricants, ISSN 2075-4442, Vol. 9, no 12Article in journal (Refereed)
    Abstract [en]

    There are many moving machine assemblies with conformal tribological contacts at very high contact pressures, e.g., sliding bearings, propeller shaft bearings and machine guideways. Furthermore, applications such as trunnion and guide vane bearing in Kaplan turbines have very low sliding speeds and oscillatory types of motion. Although there is a vast selection of tribology test rigs available, there is still a lack of test equipment to perform friction and wear tests under high contact pressure, reciprocatory sliding and large area contact. The aim of this work is thus to develop a novel reciprocating tribometer and test method that enables friction and wear tests under low-speed reciprocatory sliding with contact pressures up to 90 MPa in a flat-on-flat contact configuration. First, a thorough description of the test rig design is given. Secondly, the influence of contact pressure and stroke length on the tribological properties of a stainless steel and polymer composite material combination is studied. The significance of considering creep, friction during the stroke and contact temperature is specifically highlighted. The novel tribometer can be used to screen different bearing and shaft material combinations and to evaluate the friction and wear performance of self-lubricating bearings for the specific operating conditions found in Kaplan turbines. 

  • 19.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Rodiouchkina, Maria
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Influence Of Operational and Surface Conditions on the Tribological Performance of Self-Lubricating Polymer Composite Bearing Materials Used in Hydropower Applications2019In: 74th STLE Annual Meeting and Exhibition: Program Guide and Schedule, Society of Tribologists and Lubrication Engineers (STLE) , 2019, p. 138-140Conference paper (Refereed)
    Abstract [en]

    In hydropower applications, self-lubricating polymer composite bearings has proven to be a good and environmentally friendly replacement for the traditionally used grease lubricated bronze bearings. However, in recent years, end users have experienced several bearing failures due to more demanding operating conditions due to integration of fluctuating renewable energy sources, e.g. wind and solar power, into the electric power systems.

    The aim of this work is to summarize and highlight important findings regarding the influence of various parameters on the tribological behaviour of these bearing materials using a linear reciprocating pin-on-disc configuration.

    Results indicates that low sliding speed and high nominal pressure offer the best performance for these bearing materials, with a reduction in frictional loses with up to 45% and almost three times lower wear. Furthermore, friction and wear can be reduced even more by optimizing the surface topography and hardness of the shaft.

  • 20.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction and Wear of Self-Lubricating Materials for Hydropower Applications under Different Lubricating Conditions2017In: Lubricants, ISSN 2075-4442, Vol. 5, no 3, article id 24Article in journal (Refereed)
    Abstract [en]

    Self-lubricating bearings in hydropower applications are often lubricated with water under boundary lubricating conditions. Polyhydric alcohols replacing water have shown the potential to reduce both friction and wear. The objective of this work is, therefore, to evaluate the effect of a polyhydric alcohol-based environmentally-acceptable lubricant (EAL) on the friction and wear of self-lubricating materials for conformal contacts under boundary lubricating conditions. The lubricating properties of four commercially-available self-lubricating bearing materials were investigated under three different lubricating conditions: dry, water and a new polyhydric alcohol-based EAL. Bearing materials include one metallic composite and three polymer composites. A reciprocating motion test rig was used to evaluate the wear and friction properties. Surface analysis was performed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and optical profilometry. Results show that the wear rate for the polymer composites is increased when water is present compared to dry operating conditions. The new polyhydric alcohol-based EAL substantially improves both friction and anti-wear performance of all four self-lubricating bearing materials compared to both dry and water conditions. Surface analysis indicates that the material transfer to the counter-surface is limited when the polyhydric alcohol-based EAL is used.

  • 21.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction characteristics of environmentally adapted lubricants in boundary lubricated contacts2017Conference paper (Refereed)
  • 22.
    Berglund, Kim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Performance of self‐lubricating materials for hydropower applications under different lubricating conditions2016In: Nordic Symposium on Tribology - NORDTRIB 2016, 2016Conference paper (Other academic)
  • 23.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Spencer, Andrew
    Dynamics, Acoustics and Tribology, Engine Dynamics, Scania, Scania Technical Centre.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The effect of ageing on elastohydrodynamic friction in heavy-duty diesel engine oils2017In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 231, no 6, p. 708-715Article in journal (Refereed)
    Abstract [en]

    To further improve the efficiency of machine components found in automotive engine systems it is important to understand the friction generation in these components. Modelling and simulation of these components are crucial parts of the development process. Accurate simulation of the friction generated in these machine components is, amongst other things, dependent on realistic lubricant rheology and lubricant properties, where especially the latter may change during ageing of the lubricant. Many modern heavy-duty diesel engines are in operation for several hundred hours before the engine oil is changed. In this work, two engine oils, one 10 W-30 and one 5 W-20, have been aged in full heavy-duty diesel engine bench tests for 400 and 470 hours respectively. This roughly corresponds to the amount of ageing these oils are subjected to between oil drains in field conditions. The aged oils were subjected to a number of oil analyses showing, among other things, a maximum increase in oil viscosity of 12.9% for the 5 W-20 oil and 5.5% for the 10 W-30 oil, which is most likely primarily an effect of evaporation and oxidation. The aged oils were tested in a ball-on-disc test rig under elastohydrodynamic conditions where friction was measured and the performance was compared to fresh samples of the same oils. The results show that there is almost no difference in elastohydrodynamic friction when comparing the aged oils with the fresh oils. These results indicate that it is not necessary to include oil ageing in numerical elastohydrodynamic friction models as long as the oil is changed before the ageing has reached a critical level

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  • 24.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Spencer, Andrew
    Scania.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The effect of oil ageing on friction in elastohydrodynamic lubrication2018Conference paper (Refereed)
    Abstract [en]

    Numerical modeling of friction in elastohydrodynamically lubricated contacts are of high importance in the development of various types of machine elements such as gears, rolling element bearings and cam followers. The friction generated in the machine elements of a system does not only affect efficiency, but also the dynamics and overall function. Accurate simulation of the friction generated in machine components is, among other things dependent on realistic lubricant properties, which may change during ageing of the lubricant. Many modern machines are in operation for several hundred ours before the oil is changed. In this work, two engine oils, one 10W-30 and one 5W-20, have been aged in full heavy-duty diesel engine bench tests for a duration comparable to the amount of ageing these oils are subjected to between oil drains in field conditions. The aged oils were subjected to several analyses showing, among other things, a maximum increase in viscosity, and a reduction in some additives. Fresh and aged oils were tested in a ball-on-disc test rig under elastohydrodynamic conditions where friction was measured. The results showed almost no difference in elastohydrodynamic friction between the fresh and the aged oils.

  • 25.
    Emadi, Maryam
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Does your lubrication system conform to the concept of green chemistry?2016Conference paper (Other academic)
    Abstract [en]

    We frequently find “EAL” (environmentally acceptable lubricant or relevant such as “environmentally friendly,” “environmentally adapted,” “environmental benign,” “biodegradable,” “ecological,” “green,” in the title and keywords of tribology papers. It intimates "something good for environment" and may catch the readers' attention. However, one might feel unease because the definition of these terms is unclear. These terms are too loosely used with the authors’ satisfaction in most cases. Of course, lubrication engineering contributes to protect global environment by improving energy efficiency and prolonging machine life through reducing friction and wear. In this regard, lubrication itself is definitely one of the “green” technologies. This led a simple question – why adjectives such as “environmental” are used with lubrication? The unrivalled reference book in tribology defines “environmentally friendly lubricants” as “readily biodegradable in nature” [1]. We agree with it, but shall ask "is biodegradability enough for protection of global environment?" This motivated us to propose unambiguous criteria for EAL.

  • 26.
    Fatima, Nowshir
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Influence of water on the tribological properties of zinc dialkyl-dithiophosphate and over-based calcium sulfonate additives in wet clutch contacts2015In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 87, p. 113-120Article in journal (Refereed)
    Abstract [en]

    Usually the wet clutch lubricant properties vary with different formulations of base oil types and additives. The aim of this paper was to evaluate the effect of water on the performance of additives in ATF. Simplified lubricants, ZDDP and over-based Ca-sulfonates detergent additives in an API Group I mineral base oil, were employed to compare with the commercial fully-formulated automatic transmission fluid (DEXRON®VI) during water-contamination. A full-scale wet clutch test rig was used to evaluate the frictional response due to water contamination of the lubricants. Fourier Transform Infrared Spectroscopy was utilized to evaluate the variation in the solubility of these polar organic additives in the water phase and Karl-Fischer titration was utilized to evaluate the post-test water content for different formulations.

  • 27.
    Marklund, Pär
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Kassfeldt, Elisabet
    Baldos II, Sweden's most fuel efficient car: approved for street use2010In: SAE 2010 Powertrains, Fuels and Lubricants Meeting: October 25 - 27, 2010, San Diego, California, USA ; [papers], Warrendale, Pa: Society of Automotive Engineers, Incorporated , 2010Conference paper (Other academic)
    Abstract [en]

    Baldos II originates as an entry for the 2009 Shell Eco-marathon competition. It is built in cooperation between students from different fields of study, such as Mechanical Engineering, Industrial Design Engineering and Computer Science from Luleå University of Technology, Sweden. The car has been designed to meet the requirements set by Swedish authorities for legal street use. This includes wind screen wiper, 3-point seat belt, proper lighting, reverse gear and twin electric engines. Baldos II is tested and found to be Sweden's most fuel efficient car approved for street use.The internal combustion engine in the serial hybrid drive train is modified from an ordinary gasoline engine to run on pure ethanol. The fuel consumption of the vehicle corresponds to 0.065 litres ordinary gasoline/10 km, which results in a CO2 emission of 12 g/km. The car is design for one person only, and has room for a luggage in the size of an ordinary cabin bag. With full tank the total weight is 220 kg, and the total length is 2650 mm. The light weight has been achieve thorough an advanced monocoque chassis manufactured of carbon fiber sandwich construction.According to safety regulations the car is equipped with dual circuit hydraulic disc brakes. Today, the Team Baldos aims for defining a higher standard for street vehicles in Sweden.

  • 28. Marklund, Pär
    et al.
    Berglund, Kim
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The influence on boundary friction of the permeability of sintered bronze2008In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 31, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Components made of sintered bronze are often used in tribological systems. Examples of applications are self lubricated bearings, wet clutches and brakes and synchromesh components for manual gearboxes. The bronze material in these applications is often porous and permeable. However, the required level of permeability i.e., the ability for a fluid to flow inside the material varies widely for different applications. This implies the need to investigate if the permeability can influence the properties of a tribological system. Various studies have been performed in order to investigate the permeability of different materials but a possible relationship between permeability and boundary lubrication performance has not yet been thoroughly investigated. In this article this relationship has been investigated in a pin-on-disk apparatus for test specimens with a permeability that is well-defined. Materials with three different permeabilities were investigated together with non-permeable test specimens. The results indicate that permeability has a small influence on the friction coefficient when the tribological system is operating with good lubrication of the contact. The function of the tribological system when working under starved conditions is also investigated and a very clear relationship between permeability and the ability to cope up with starved running conditions is shown. This is explained in terms of the varying ability of the materials' to store lubricant in pores. Non-porous test specimens were also tested as a comparison with the permeable test specimens in the investigation with starved running conditions . The results show that a material with high permeability works much better under starved running conditions than that with low permeability.

  • 29.
    Rodiouchkina, Maria
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Dry sliding wear and friction behavior of self-lubricating polymer composite bearing materials under extreme operating conditions2017Conference paper (Refereed)
  • 30.
    Rodiouchkina, Maria
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Rodushkin, Ilia
    ALS Laboratory Group, ALS Scandinavia AB, SE-977 75 Luleå, Sweden.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Influence of Counter Surface Roughness and Lay on the Tribological Behaviour of Self-Lubricating Bearing Materials in Dry Sliding Conditions at High Contact Pressures2022In: Lubricants, E-ISSN 2075-4442, Vol. 10, no 8, article id 167Article in journal (Refereed)
    Abstract [en]

    In Kaplan turbines, the most critical components are the self-lubricating polymer composite bearings used to control the guide vanes and the turbine blades. Reducing the sliding wear and friction of these bearings can benefit both the economy and the environment, including longer useful life, lower operational costs, and higher efficiency. In this study, the influence of stainless-steel counter surface roughness and lay on the tribological behaviour of three bearing materials used in hydropower applications were investigated using a linear reciprocating flat-on-flat configuration under high contact pressure and low sliding speed. The surface roughness was measured using white light interferometry. SEM and EDS analysis were used to investigate the worn surfaces. Results from this study show that overly smooth surfaces result in higher friction and wear of the counter surface, while rougher surfaces have a negative effect on the wear of the polymers. Highest surface coverage using protective transfer layers is found on the steel surfaces with the perpendicular lay and is accompanied with a lower coefficient of friction compared to the parallel lay. The dominant wear mechanism of the bearing materials changes from delamination wear to abrasive wear between the lowest and the intermediate roughness for steel surfaces with the parallel lay. It can be concluded that counter surface topography has a significant influence on the tribological behaviour of these bearing materials and that the effect differs between the self-lubricating polymer composites.

  • 31.
    Rodiouchkina, Maria
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Influence of counter surface roughness and orientation on the tribological behavior of self-lubricating bearing materials in dry sliding conditions2018Conference paper (Refereed)
    Abstract [en]

    Bearing failures account for a significant share of the operational economical losses in hydropower plants. In Kaplan turbines, the most critical components are the self-lubricating polymer composite bearings used for regulation of the guide vanes and the turbine blades as they operate at high loads, low sliding speeds and small oscillatory movements. Reducing the sliding wear and friction of these bearings would offer a positive impact on both the economy and environment including longer useful life, lower operational costs and higher efficiency.

    In this study, influence of counter surface roughness and orientation on the tribological behavior of bearing materials used in hydropower applications are investigated using a linear reciprocating block-on-block configuration under high pressure and low sliding speed. Surface roughness was measured using white light interferometry. SEM and EDS analysis were used to investigate the polymer surfaces and the transfer film formation.

    Results from this study indicates that too smooth surfaces result in higher friction and wear of the counter surface while rougher surfaces have a negative effect on the wear of the polymers. It can be concluded that counter surface topography has a significant influence on the tribological behavior of these bearings and the effect differs between materials.

  • 32.
    Rodiouchkina, Maria
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rodushkin, Ilia
    ALS Laboratory Group, ALS Scandinavia AB.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Material Characterization and Influence of Sliding Speed and Pressure on Friction and Wear Behavior of Self-Lubricating Bearing Materials for Hydropower Applications2018In: Lubricants, ISSN 2075-4442, Vol. 6, no 2, article id 39Article in journal (Refereed)
    Abstract [en]

    Nowadays, hydropower plants are forced to have more frequent power control and the self-lubricated bearings used in the applications are one of the most critical components affected by the continuously changing operating conditions. In this study, microstructure and composition of two commercially available bearing materials (Orkot TXM Marine and Thordon ThorPlas) used in hydropower turbines were studied. In addition, the influence of sliding speed and applied pressure on the friction and wear behavior of the materials was investigated systematically for dry sliding conditions. The bearing materials were characterized using X-ray microtomography, Nuclear Magnetic Resonance (NMR) spectroscopy and Inductively Coupled Plasma–Sector Field Mass Spectrometry (ICP-SFMS) techniques. Friction and wear tests were carried out with a polymer pin sliding against a stainless steel (SS2333) plate with a linear reciprocating motion. Test conditions were: room temperature, 9–28 MPa pressure and 10–40 mm/s sliding speed ranges. Surface analysis of the polymer pins and the wear tracks were performed by optical profilometry, Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) techniques. Test results show that, for both materials, the coefficient of friction (COF) is decreasing at higher pressures. Surface analysis reveals higher concentrations of solid lubricants in the transfer layers formed at higher pressures, explaining the decrease in COF. Furthermore, the specific wear rate coefficients are increasing at higher sliding speeds, especially at lower pressures. Results of this study demonstrate that, under dry sliding conditions, changes in sliding speed and pressure have a significant influence on the tribological behavior of these bearing materials.

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  • 33.
    Rodiouchkina, Maria
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lind, Jonna
    Tribomaterials Group, The Ångström Laboratory, Uppsala University, SE-752 37, Sweden.
    Pelcastre, Leonardo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Kassman Rudolphi, Åsa
    Tribomaterials Group, The Ångström Laboratory, Uppsala University, SE-752 37, Sweden.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological behaviour and transfer layer development of self-lubricating polymer composite bearing materials under long duration dry sliding against stainless steel2021In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 484–485, article id 204027Article in journal (Refereed)
    Abstract [en]

    Fibre-reinforced thermosets and thermoplastics containing PTFE are commonly used in marine and hydropower applications due to their self-lubricating ability in both dry and water lubricated contacts. The constant development of such composite bearings over the last decades make them even more attractive in these fields of application, due to their low maintenance cost and long service life. Their tribological performance is usually estimated by extrapolation of short, accelerated tests, which may induce risks of inaccurate or even incorrect interpretation.

    In this work, reciprocating dry sliding behaviour of these materials against stainless steel is investigated under typical hydropower conditions. The aim is to study the wear and friction behaviour and the development of transfer layers during long sliding tests, corresponding to years of operation. In order to mimic operational shutdowns, the tests are stopped every 20 h and the counter surfaces are examined using 3D optical interferometry and SEM to study development of surface topography and transfer layers.

    Test results show that the wear rates of both materials decrease significantly with time. For the thermoplastic, COF decreases with time due to accelerated material transfer observed after 80 h. In contrast, much less material transfer is observed for the fibre-reinforced thermoset, which shows its highest transfer amount after 20 h. Surface analysis indicates severe abrasive wear of the counter surface caused by the wear debris from steel and reinforcements in the material and is accompanied by simultaneous COF increase for the thermoset. Cross-sectional analysis reveals thinner transfer layers and higher wear of the steel in the middle of the wear tracks, where the sliding speed and number of load cycles are highest. These findings contribute to a more accurate interpretation of results obtained than that of short time tests regarding the tribological performance of these materials. As a direct conclusion, the selection of counter surface material can be crucial.

  • 34.
    Rodiouchkina, Maria
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lindsjö, Henrik
    N63 Degrees AB, SE-835 95, Sweden.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Effect of stroke length on friction and wear of self-lubricating polymer composites during dry sliding against stainless steel at high contact pressures2022In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 502-503, article id 204393Article in journal (Refereed)
    Abstract [en]

    The increased control of hydropower plants (i.e. shift from water level to primary control) leads to an increased number of load cycles on critical components such as bearings in hydropower turbines. Despite having shorter sliding amplitudes, this may result in a longer accumulated sliding distance that reduce the useful life of the bearings.

    In this study, the effect of stroke length on the tribological performance of two self-lubricating polymer composites, commonly used for bearings in hydropower turbines, during dry sliding against stainless steel is investigated. The reciprocating tests are carried out under relevant conditions, i.e. high pressures and long sliding distance, corresponding to years of operation of a hydropower turbine. The worn polymer and stainless-steel surfaces are examined using 3D optical surface profilometer and SEM/EDS to study the wear and friction mechanisms.

    The results show an increasing wear rate with increased stroke length for both bearing materials, especially when the stroke length is longer than the length of the polymer pin. The thermoset show the same trend for the frictional behaviour and it is attributed to decrease in coverage by transfer layers and solid lubricants at the sliding interface as well as increase in abrasive wear of the stainless steel. Meanwhile, the highest friction is observed at the shortest stroke length for the thermoplastic and the lowest at the intermediate stroke. Surface analysis reveals higher abrasive wear of the stainless-steel counter surface at the longest stroke length for both bearing materials due to lower wear particle entrapment. It can be concluded that changes in sliding amplitude have a significant influence on the tribological performance of the two polymer composites sliding against stainless steel.

  • 35.
    Rodiouchkina, Maria
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Pelcastre, Leonardo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lind, Jonna
    Uppsala University, Uppsala, Sweden.
    Kassman Rudolphi, Åsa
    Uppsala University, Uppsala, Sweden.
    Tribological behaviour of self-lubricating polymercomposite bearing materials during long-time dry sliding2019In: 74th STLE Annual Meeting and Exhibition, Society of Tribologists and Lubrication Engineers (STLE) , 2019, p. 140-140Conference paper (Refereed)
    Abstract [en]

    Thermosets and thermoplastics containing PTFE are used in marine and hydropower applications due to their long service life and self-lubricity in dry and water-lubricated contacts. Their tribological performance is usually extrapolated from short, accelerated tests, which induces risks of inaccurate or incorrect interpretation.

    The aim of this study is to investigate the tribological behaviour and development of transfer layers during long sliding tests (160 hours), corresponding to years of operation. To mimic operational shutdowns, the tests were stopped every 20 hours to study the evolution of the surface topography and transfer layers.

    The wear rates of both materials decreased significantly with time. For the thermoplastic, COF decreased due to accelerated material transfer after 80 hours, highlighting the importance of long duration tests. The thermoset showed the highest transfer amount after 20 h and cause severe abrasive wear on the counter surface accompanied by a COF increase.

  • 36.
    Rudnytskyj, André
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Rodiouchkina, Maria
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hultqvist, Tobias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Contact mechanics and wear of self-lubricating polymer bearings used in hydropower applications2018Conference paper (Refereed)
    Abstract [en]

    Hydropower plants are today subjected to more frequent transient operating conditions due to the increased use of intermittent energy production sources, such as solar and wind. The changes arise from the need to regulate the power input to the electrical grid, posing questions on the reliability of the self-lubricated bearings used in hydropower applications. Aiming to study the effects of the transient conditions on wear and lifetime of these bearings, modelling and simulation have been employed to systematically investigate how different parameters influence the sliding contact. A simplified model developed using COMSOL Multiphysics 5.3 and LiveLink™ for MATLAB® of polymer composite bearing materials and stainless steel counter surface is presented and evaluated under different tribological conditions in terms of properties such as pressure, sliding speed, temperature and wear. Roughness of real surfaces is measured by white light interferometry and integrated in the model. Experimental results on the influence of important parameters on the behavior of such bearings are also presented, not only to validate the model, but also to provide input data to the simulation. The results of this study show that the simulation model can be used to identify critical operating conditions for self-lubricating bearings used in hydropower applications.

  • 37.
    Sandström, Lars-Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Fault Detection And Friction Monitoring In Hydropower Turbines2022Conference paper (Other academic)
  • 38.
    Shi, Yijun
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Vadivel, Hari
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Studying the tribological properties of PEEK composites lubricated by different lubricants for hydropower turbine application2016Conference paper (Refereed)
  • 39.
    Somberg, Julian
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Saravanan, Prabakaran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Vadivel, Hari Shankar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Sustainalube AB, Sweden.
    Ukonsaari, Jan
    Vattenfall AB, R&D, Sweden.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological characterisation of polymer composites for hydropower bearings: Experimentally developed versus commercial materials2021In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 162, article id 107101Article in journal (Refereed)
    Abstract [en]

    To mitigate the effects of downstream lubricant spillage from hydroelectric power plants, environmentally friendly lubricants are required. For the sustainable operation of oil-free bearings, the development of high performance bearing materials is crucial. In this study, the tribological performance of PPS and UHMWPE-based composites, incorporating various reinforcements, such as graphene oxide, is evaluated and compared with five commercial materials. Experiments were performed under different lubricating conditions; Dry, water, and using a glycerol-based environmentally adaptive lubricant (EAL). The use of water inhibited an adequate transfer film, which increased wear for most materials. EAL lubrication showed a significant reduction in friction (up to 98%) when compared to dry conditions. The experimentally developed PPS composite provided superior tribological properties, especially under water-lubricated conditions.

  • 40.
    Strömbergsson, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Bearing faults in the wind turbine drivetrain: Comparative study of monitoring with FFT and the Discrete Wavelet Transform2017Conference paper (Refereed)
  • 41.
    Strömbergsson, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Increasing Wind Turbine Drivetrain Bearing Vibration Monitoring Detectability Using an Artificial Neural Network Implementation2021In: Applied Sciences, E-ISSN 2076-3417, Vol. 11, no 8, article id 3588Article in journal (Refereed)
    Abstract [en]

    The highest costs due to premature failures in wind turbine drivetrains are related to defects in the gearbox, with bearing failures being overrepresented. Vibration monitoring has been identified as the primary tool to detect and diagnose these types of failures. However, late or no signs of the failures are still being reported. Artificial neural networks (ANNs) has been shown to favourably be used as a classifier of bearing failures to increase the detection and diagnosis performance, which requires labelled data when training for all types of considered failures. However, less work has been done with an ANN used to create descriptive functions of the vibration and turbine operation data relationship and thereby negating inherent variance in the vibration data and increasing the detectability when a defect appears. Therefore, this study utilizes the relationship between the rotational speed recorded during a vibration measurement and the calculated condition indicator values of specific bearing failures in three wind turbine gearbox failures. An ANN establishes a function between the rotational speed and condition indicator values with healthy training data collected before the failure occurred. Thereafter, whole datasets leading up to the changing of the gearboxes is used to predict the condition indicator values without the failure influence. The difference between the predicted and true values show an increased sensitivity of the detection in two cases of gearbox output shaft bearing failures as well as indicating a planet bearing failure which with the previous data had gone undetected.

  • 42.
    Strömbergsson, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Multi-body simulation and validation of fault vibrations from rolling-element bearings2021In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 235, no 9, p. 1834-1841Article in journal (Refereed)
    Abstract [en]

    Dynamic simulations are often used to evaluate the vibrational response of rolling-element bearings experiencing defects. Previously, the optimal accelerometer position has been found to be as close as possible to the bearing. However, further details about the influence of rotational symmetry have not been closely investigated. This paper presents a dynamic simulation model of a radially loaded complete spherical roller bearing with a defect in the inner ring and placed in a housing with 72 equally spaced accelerometer positions around the circumference. Surface accelerations have been extracted and transformed into the frequency domain. Thereafter, the vibrational components indicating the defect have been evaluated around the circumference. The results show an optimal position as close as possible to the primary loaded zone and validation test rig experiments show a reasonable qualitative agreement.

  • 43.
    Strömbergsson, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Wind turbine drivetrain condition monitoring by vibration analysis Part B:: Anomaly detection using artificial neural networksManuscript (preprint) (Other academic)
  • 44.
    Strömbergsson, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Division of Machine Elements, Lule&aring: University of Technology, Luleå SE 97187, Sweden.
    Larsson, P-E
    Industrial Digitalisation & Solutions, SKF (Sweden), Luleå, Sweden.
    Property requirements of vibration measurements in wind turbine drivetrain bearing condition monitoring2021In: Insight: Non-Destructive Testing & Condition Monitoring, ISSN 1354-2575, E-ISSN 1754-4904, Vol. 63, no 11, p. 667-674Article in journal (Refereed)
    Abstract [en]

    Wind turbine drivetrain bearing failures continue to lead to high costs resulting from turbine downtime and maintenance. As the standardised tool to best avoid downtime is online vibration condition monitoring, a lot of research into improving the signal analysis tools of the vibration measurements is currently being performed. However, failures in the main bearing and planetary gears are still going undetected in large numbers. The available field data is limited when it comes to the properties of the stored measurements. Generally, the measurement time and the covered frequency range of the stored measurements are limited compared to the data used in real-time monitoring. Therefore, it is not possible to either reproduce the monitoring or to evaluate new tools developed through research for signal analysis and diagnosis using the readily available field data. This study utilises 12 bearing failures from wind turbine condition monitoring systems to evaluate and make recommendations concerning the optimal properties in terms of measurement time and frequency range the stored measurements should have. The results show that the regularly stored vibration measurements that are available today are, throughout most of the drivetrain, not optimal for research-driven postfailure investigations. Therefore, the storage of longer measurements covering a wider frequency range needs to begin, while researchers need to demand this kind of data.

  • 45.
    Strömbergsson, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Per-Erik
    Industrial Digitalisation & Solutions, SKF (Sweden), Luleå, Sweden.
    Bearing monitoring in the wind turbine drivetrain: A comparative study of the FFT and wavelet transforms2020In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 23, no 6, p. 1381-1393Article in journal (Refereed)
    Abstract [en]

    Wind turbines are often plagued by premature component failures, with drivetrain bearings being particularly subjected to these failures. To identify failing components, vibration condition monitoring has emerged and grown substantially. The fast Fourier transform (FFT) is the major signal processing method of vibrations. Recently, the wavelet transforms have been used more frequently in bearing vibration research, with one alternative being the discrete wavelet transform (DWT). Here, the low‐frequency component of the signal is repeatedly decomposed into approximative and detailed coefficients using a predefined mother wavelet. An extension to this is the wavelet packet transform (WPT), which decomposes the entire frequency domain and stores the wavelet coefficients in packets. How wavelet transforms and FFT compare regarding fault detection in wind turbine drivetrain bearings has been largely overlooked in literature when applied on field data, with non‐ideal placement of sensors and uncertain parameters influencing the measurements. This study consists of a comprehensive comparison of the FFT, a three‐level DWT, and the WPT when applied on enveloped vibration measurements from two 2.5‐MW wind turbine gearbox bearing failures. The frequency content is compared by calculating a robust condition indicator by summation of the harmonics and shaft speed sidebands of the bearing fault frequencies. Results show a higher performance of the WPT when used as a field vibration measurement analysis tool compared with the FFT as it detects one bearing failure earlier and more clearly, leading to a more stable alarm setting and avoidable, costly false alarms.

  • 46.
    Strömbergsson, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Per-Erik
    Industrial Digitalisation & Solutions, SKF (Sweden), Luleå, Sweden..
    Wind turbine drivetrain condition monitoring by vibration analysis Part A:: Property requirements of vibration measurementsManuscript (preprint) (Other academic)
  • 47.
    Strömbergsson, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Saari, Juhamatti
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Thomson, Allan
    Industrial Digitalisation & Solutions, Livingston, Scotland.
    Mother wavelet selection in the discrete wavelet transform for condition monitoring of wind turbine drivetrain bearings2019In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 22, no 11, p. 1581-1592Article in journal (Refereed)
    Abstract [en]

    Although the discrete wavelet transform has been used for diagnosing bearing faults for two decades, most work in this field has been done with test rig data. Since field data starts to be made more available, there is a need to shift into application studies.

    The choice of mother wavelet, ie, the predefined shape used to analyse the signal, has previously been investigated with simulated and test rig data without consensus of optimal choice in literature. Common between these investigations is the use of the wavelet coefficients' Shannon entropy to find which mother wavelet can yield the most useful features for condition monitoring.

    This study attempts to find the optimal mother wavelet selection using the discrete wavelet transform. Datasets from wind turbine gearbox accelerometers, consisting of enveloped vibration measurements monitoring both healthy and faulty bearings, have been analysed. The bearing fault frequencies' excitation level has been analysed with 130 different mother wavelets, yielding a definitive measure on their performance. Also, the applicability of Shannon entropy as a ranking method of mother wavelets has been investigated.

    The results show the discrete wavelet transforms ability to identify faults regardless of mother wavelet used, with the excitation level varying no more than 4%. By analysing the Shannon entropy, broad predictions to the excitation level could be drawn within the mother wavelet families but no direct correlation to the main results. Also, the high computational effort of high order Symlet wavelets, without increased performance, makes them unsuitable.

  • 48.
    Wu, Jian
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University.
    Huang, Xianzhu
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing .
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Feng, Xin
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing .
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    CuO nanosheets produced in graphene oxide solution: An excellent anti-wear additive for self-lubricating polymer composites2018In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 162, p. 86-92Article in journal (Refereed)
    Abstract [en]

    In the present work, graphene oxide is used as template to produce CuO nanosheets, which solves aggregation and dispersion problems of CuO nanosheets resulting in improved lubricating performance. SEM and AFM studies show that CuO nanosheets are present in fusiform flake shape with a thickness, width and length of around 13, 400 and 1000 nm, respectively. CuO nanosheets were added to the carbon fibers reinforced Polytetrafluoroethylene (CF/PTFE) to study their lubricating performance. It is interesting, from fractured surfaces of composites, to find that CuO nanosheets enhance the interface properties between carbon fibers and PTFE. The wear resistance property of CF/PTFE is remarkably improved after filling CuO nanosheets. For example, the wear rate is reduced by 51% after filling 1.5 wt % CuO nanosheets. The wear resistance improvement effect of CuO nanosheets is much better than that of commercial CuO nanogranules and CuO nanorods. Worn surfaces and counter-surfaces studying indicates that CuO nanosheets can not only prevent the rubbed-off of PTFE or the detachment of CF, but also improve the properties of transfer films, which greatly reduce the adhesive wear and abrasive wear.

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