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Vehicle Model for Tyre-Ground Contact Force Evaluation

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Vehicle Model for Tyre-Ground Contact Force Evaluation Vehicle model for tyre-ground contact force evaluation Lejia Jiao Master Thesis in Vehicle Engineering Department of Aeronautical and Vehicle Engineering KTH Royal Institute of Technology TRITA-AVE 2013:40 ISSN 1651-7660 Postal address Visiting Address Telephone Telefax Internet KTH Teknikringen 8 +46 8 790 6000 +46 8 790 6500 www.kth.se Vehicle Dynamics Stockholm SE-100 44 Stockholm, Sweden Acknowledgment I owe gratitude to many people for supporting me during my thesis work. Especially, I would like to express my deepest appreciation to my supervisor, Associate professor Jenny Jerrelind, for her enthusiasm and infinite passion for this project. Without her patient guidance and persistent help, this thesis would not have been possible. I am particularly indebted to my parents for inspiring me to this work. I would like to thank Associate professor Lars Drugge, who introduced me to vehicle-road interaction and gave me enlightening instruction. In addition, I would like to give my sincere thanks to Nicole Kringos and Parisa Khavassefat, for helping me to understand the pavement and sharing model and data with me; to Ines Lopez Arteaga, for giving me feedbacks from tyre expert’s point of view. The great interdisciplinary cooperation and teamwork helped me to have a good understanding of the whole vehicle-tyre-pavement system, and get rational tyre and pavement parts included in my models. Last but not least, I would like to thank all my friends, for their understanding, encouragement and support. Stockholm June 26, 2013 Lejia Jiao i ii Abstract Economic development and growing integration process of world trade increases the demand for road transport. In 2008, the freight transportation by road in Sweden reached 42 million tonne-kilometers. Sweden has a tradition of long and heavy trucks combinations. Lots of larger vehicles, with a maximum length of 25.25 meters and weight of 60 tonnes, are used in national traffic. Heavier road transport and widely use of large vehicles contribute to the damages of pavement. According to a recent research by the VTI, total cost of road wear by freight transport in Sweden in 2005 was about 676 million SEK. If the weights of all vehicles were limited to 40 tonnes, according to the new EU rules, the cost of wear in 2005 would have been 140 million SEK less. Lots of studies about road damage caused by vehicle have been done since the last decades. It has been found that the dynamic tyre force plays an important role in the damages of pavement. However, the influence of vehicle-pavement interaction on pavement damage has not been investigated to any large extent yet. The aim of this study is to provide suitable computational truck models, study the influence of vehicle-pavement interaction and parameters of vehicle on pavement damage. To fulfil the aims, this study presents vehicle models, including quarter, half, full vehicle models and quarter vehicle model coupled with pavement, used to compute the dynamic tyre force. The different models are then compared. Two actual road profiles measured by laser, a smooth one and an uneven one, are used for evaluation. The models are analysed to find out the vehicle parameters that influence the road damage most and to learn about how detailed models are needed. It’s found that difference does exist between more detailed models and less detailed ones, and it’s non-negligible. It will increase with the increase of road unevenness. The dynamic tyre force will not be affected much by coupling the pavement, unless the road surface is very uneven or wheel hop exists. On uneven roads, energy mainly dissipates in vehicle suspension. However, on even roads, vibration can be well damped in tyre before it reaches suspension, so most of energy dissipates in tyre. Different components influence the tyre force differently. The influence varies with different frequency range of input signal (road profile) as well. The effects of sprung parts are mainly in low frequency range, while the effects of unsprung parts are mainly in high frequency range. Parameters of vehicle body influence the dynamic tyre force most. The effect of cabin is much smaller compared to vehicle body and unsprung part. Changes in parameters of pavement will not influence the road load, but its resonant frequency. Therefore, the best way to reduce dynamic tyre load is to design a more lightweight vehicle body, softer and better damped suspension. iii iv Contents 1 Introduction ............................................................................................................. 1 1.1 Background ............................................................................................................................. 1 1.2 Problem description ............................................................................................................... 1 1.3 Aim ........................................................................................................................................... 3 2 Methodology ........................................................................................................... 4 3 Vehicle models ........................................................................................................ 5 3.1 Introduction ............................................................................................................................ 5 3.2 Model establishment .............................................................................................................. 6 3.2.1 Quarter vehicle model .................................................................................................... 6 3.2.2 Quarter vehicle model coupled with pavement ......................................................... 8 3.2.3 Half vehicle model ........................................................................................................ 10 3.2.4 Full vehicle model ......................................................................................................... 13 4 Model comparison .................................................................................................. 16 4.1 Parameters used in simulation ............................................................................................ 16 4.1.1 Vehicle parameters ........................................................................................................ 16 4.1.2 Pavement parameters ................................................................................................... 17 4.2 Quarter, half and full vehicle .............................................................................................. 18 4.3 Influence of coupled pavement ......................................................................................... 24 4.4 Energy dissipation ................................................................................................................ 27 5 Parametric study .................................................................................................... 29 5.1 Typical response and frequency distribution ................................................................... 29 5.2 Effect of mass ....................................................................................................................... 32 5.3 Effect of stiffness ................................................................................................................. 35 5.4 Effect of damping ................................................................................................................ 38 6 Conclusions ............................................................................................................ 41 7 Future work ............................................................................................................ 44 8 References .............................................................................................................. 45 v vi 1 Introduction This chapter gives a brief review of history and background, a short introduction to the subject and the goals of this study. 1.1 Background With the growing and deepening of the integration process of world trade, the demand for freight transport, especially by road, continues to increase. According to the Swedish Road Administration, the freight transport by road is continuously increasing, and arrived around 45 billion tonne-kilometres in 2008, which has exceeded train and marine transport [1]. Sweden has a tradition of long and heavy trucks combinations. Lots of larger vehicles, with a maximum length of 25.25 metres and weight of 60 tonnes, are used in national traffic [2]. Heavier road transport and widely use of larger vehicles will contribute to the damages of pavement, such a fatigue cracking, permanent deformation etc. The maintenances of road call for huge amount of investment. According to research performed by the Swedish national Road and Transport Research Institute (VTI), in Sweden, total cost of road wear by freight transport in 2005 was about 676 million SEK. If all the freight transportation carried out with vehicles weighing more than 40 tonnes is redistributed to vehicles that weigh a maximum of 40 tonnes, according to the new EU rules, the cost of wear in 2005 would have been 140 million SEK less [2]. However, limiting the maximum weight of vehicles isn’t the only and best measurement to reduce the pavement wear and thereby reduce the associated cost. If the mechanisms, which lead to the road surface damage, and the
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