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  • 1.
    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.

  • 2.
    Fatima, Nowshir
    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.
    Water contamination effect in wet clutch system2013In: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 227, no 3, p. 376-389Article in journal (Refereed)
    Abstract [en]

    Water contamination in wet clutch systems can be a problem since both torque characteristics and wear resistance can be influenced by water presence. The present paper reveals the effect of externally added water on the wet clutch frictional performance. Commercially available standard paper based friction plates and steel separator plates lubricated in commercially available automatic transmission fluid were investigated in a recently developed automated test rig implementing a well confined experimental approach. Frictional response was observed for three different situations with different water amount and water exposure time. There is observed undesirable friction increase with increasing water amount in the system. The rate of increase in friction coefficient does not linearly depend on the amount of added water and this is a noticeable outcome from the common possible water contamination effects like change in lubricant viscosity, inadequate additive performance and weakening of friction material. The more reduced separator plates’ surface roughness (Ra) in a water contaminated clutch system compared to an uncontaminated one can be a reason for the change in friction. It is also shown that different water exposure time has no large impact on the change in friction level and separator plate’s roughness.

  • 3.
    Holgerson, Mikael
    et al.
    Luleå tekniska universitet.
    Lundberg, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Engagement behaviour of a paper-based wet clutch: Part 1: Influence of drive torque1999In: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 213, no 4, p. 341-348Article in journal (Refereed)
    Abstract [en]

    Owing to increasing demands when designing wet clutches for automatic transmissions, more knowledge about their behaviour is needed. In cars with power shifting automatic transmissions, an engine torque is continuously transmitted through the gear box. Most experimental and theoretical work concerning investigations of wet clutches today uses the inertia type of test apparatus, e.g. the SAE test machine 2. However, this type of test machine has no possibility of investigating the influence of a drive torque from the power supply. In order to investigate the influence of drive torque on wet clutch engagements, a new type of apparatus was built, which can operate with different combinations of inertia and drive torque. This apparatus can perform engagements more similar to those in automatic transmissions. The aim of this paper was to compare experimental outputs obtained using these principles of testing, concerning the influence of drive torque. It was found that the friction characteristics of wet clutches are independent of how the input energy is produced. This means that friction can be investigated with both principles. It was also found that an apparatus using only inertia gives shorter engagement times and higher temperatures than an apparatus including a drive torque at the same level of input energy. This can be explained by different power characteristics. Therefore, when investigating temperatures of wet clutch engagements, one must be careful when translating the results into reality.

  • 4.
    Holgerson, Mikael
    et al.
    Luleå tekniska universitet.
    Lundberg, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Engagement behaviour of a paper-based wet clutch: Part 2: Influence of temperature1999In: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 213, no 5, p. 449-455Article in journal (Refereed)
    Abstract [en]

    To increase comfort, performance and fuel economy, a more careful optimization of automatic transmissions is needed. Of special interest is how the temperature influences the engagement characteristics. In order to increase the level of knowledge in this area, a wet clutch test rig including a drive torque and inertia was used. The temperature and the developed energy were varied in order to investigate their influence on the characteristics of an engagement. As a consequence the influence of instant temperature, maximum temperature and instant normal force was also studied. Some of the most important conclusions of the investigation are that both the dynamic and static friction coefficients slightly decrease and the engagement time increases with increasing temperature. It was also found that the static and dynamic friction coefficients are not influenced by energy if the instant temperature is the same. An important parameter that describes the risk of stick-slip is the quotient between the static and dynamic friction. It was found that this quotient decreases with increasing temperature, and thus the risk of stick-slip is also supposed to decrease.

  • 5.
    Körning-Ljungberg, Jessica
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Human Work Science.
    Parmentier, Fabrice
    University of Balearic Islands.
    Psychological effects of combined noise and whole body vibration: a review and avenues for future research2010In: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 224, no D10, p. 1289-1302Article in journal (Refereed)
    Abstract [en]

    Vehicle drivers are often exposed to noise, whole-body vibrations (WBV) and mental loads, but the knowledge of how combined effects from multiple environmental stressors affect mental load is sparse. Studies have shown that the effect of one factor may be different than the effect of two factors presented together. For example, negative combined effects have been found when people perform mental tasks (e.g., Sommer and Harris, 1973; Harris and Schoenberger, 1980), as well as in subjective ratings (e.g., Ljungberg, Neely, Lundström, 2004). Although some of the studies investigating the combined effects of noise and WBV suffer from low ecological validity and few have investigated the possible effects on higher cognitive functions. Applying methods well-known to be sensitive to sound exposures by using serial recall tasks (e.g., Jones, Madden & Miles, 1992) as well as methods developed in the studies of noise after-effects (e.g., Glass & Singer, 1972) may be a way to continue the research field of combined effects of noise and WBV

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