<p>Traffic is a major source of green house gases. The transport field</p><p>stands for 32 % of the energy consumption and 28 % of the total</p><p>CO2 emissions, where road transports alone causes 84 % of these figures. The energy consumed by a car traveling at constant speed, is</p><p>due to engine ineffiency, internal friction, and the energy needed to</p><p>overcome resisting forces such as aerodynamic drag and rolling resistance.Rolling resistance plays a rather large role when it comes to fuel economy. An improvement in rolling resistance of 10 % can yield fuel</p><p>consumption improvements ranging from 0.5 to 1.5 % for passenger</p><p>cars and light trucks and 1.5 to 3 % for heavy trucks.</p><p>The objective of this thesis is to estimate the power consumption</p><p>in the tyres. To do this a car tyre is modeled with waveguide finite</p><p>elements. A non-linear contact model is used to calculate the contact</p><p>forces as the tyre is rolling on a rough road. The contact forces combined</p><p>with the response of the tyre is used to estimate the input power</p><p>to the tyre structure, which determines a significant part of the rolling</p><p>resistance. The tyre model accounts for: the curvature, the geometry of the</p><p>cross-section, the pre-stress due to inflation pressure, the anisotropic</p><p>material properties and the rigid body properties of the rim. The model</p><p>is based on design data. The motion of the tyre belt and side wall is</p><p>described with quadratic anisotropic, deep shell elements that includes</p><p>pre-stress and the motion of the tread on top of the tyre by quadratic,</p><p>Lagrange type, homogenous, isotropic two dimensional elements.</p><p>To validate the tyre model, mobility measurements and an experimental</p><p>modal analysis has been made. The model agrees very well</p><p>with point mobility measurements up to roughly 250 Hz. The eigenfrequency prediction is within five percent for most of the identified</p><p>modes. The estimated damping is a bit too low especially for the antisymmetric modes. Above 500 Hz there is an error ranging from 1.5 dB</p><p>up to 3.5 dB for the squared amplitude of the point mobility.</p><p>The non proportional damping used in the model is based on an <em>ad</em></p><p><em>hoc </em>curve fitting procedure against measured mobilities.</p><p>The contact force predictions, made by the division of applied</p><p>acoustics, Chalmers University of Technology, are based on a non-linear</p><p>contact model in which the tyre structure is described by its flexibility</p><p>matrix. Topographies of the surface are scanned, the tread pattern is</p><p>accounted for, and then the tyre is ’rolled’ over it. The contact forces</p><p>are inserted into the tyre model and the response is calculated. The</p><p>dissipated power is then calculated through the injected power and the</p><p>power dissipated within each element. Results are promising compared</p><p>to literature and measurements.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:kth-3994 |
| Date | January 2006 |
| Creators | Fraggstedt, Martin |
| Publisher | KTH, Aeronautical and Vehicle Engineering, Stockholm : KTH |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Licentiate thesis, comprehensive summary, text |
| Relation | Trita-AVE, 1651-7660 ; 2006:26 |
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