Performance prediction of hydroplaning via coupling of computational fluid dynamics (CFD) and FE modeling has delivered a detailed insight into the local mechanisms and root causes of hydroplaning but is still very time consuming and extensive. The goal of the present work is the development of simple rules of thumb and easy to understand models to give the tire designer a quick approach to optimize the hydroplaning performance of his design concepts including the target conflicting trade-offs. Based on the DOE study covering basic winter and summer tread patterns and tread compounds taking into account interactions, total void, longitudinal, and lateral void distributions have been varied. Experimental designs have been tested concerning longitudinal hydroplaning behavior on front and rear driven cars and lateral hydroplaning. Most important target conflicting performance criteria such as wet and dry braking, noise, rolling resistance, winter traction, and force and moment characteristics among others have been tested additionally. The existing models using hydrodynamic pressure influences have been reviewed and extended. A simple to use development tool has been programed to quantify pattern design to get a quick prediction of tire performance changes (“Void Slider”).
Due to shorter development cycles and high cost pressure, the tread pattern development process is optimized by an analysis tool, which can predict the influence of the tread pattern on several tire properties. By using this tool conventional development cycles can be substituted by several virtual development cycles. The tool modules for the tire properties traction, handling, plysteer residual aligning torque (PRAT), groove wander, and noise are presented in this paper. The applicability of evolution strategy on tread pattern development is demonstrated, being another prerequisite for a future virtual pattern development process.
Today's tread pattern design development is done independently from the tire body construction in order to achieve the best traction and uniform local wear performance. Nevertheless, a better understanding of the interaction between tread and body is necessary to improve the above mentioned properties. An identical tire has been investigated in four pattern steps, starting from a smooth tire, carving a block structure with longitudinal and lateral grooves, and finishing with additional sipes in the blocks. A new developed test stand, which is capable of measuring the stresses in the contact patch of the rolling tire in all directions with a resolution of 1 mm, is described. The local contact stresses of the investigated tread blocks are simulated by FEA using the measured loading conditions of the smooth tire. The results of this simulation are compared with measurements and mechanically interpreted.
Evaluation of tread pattern designs with respect to performance of winter tires on snow is still predominantly based on empirical knowledge. To gain greater insight into the complex interaction between the elastic tread block and the inelastically deforming snow, numerical simulations by means of the Finite Element Method (FEM) were carried out in conjunction with experimental investigations. An elastoplastic material model for snow was developed. Calibration of the model parameters is based on shear and compression tests conducted on specimens made of natural and artificial snow. Good correlation is obtained between results from laboratory experiments and from numerical simulations with respect to the deformations and the frictional behavior of a single rubber block sliding on snow.