Finite element method estimation of temperature distribution of automotive tire using one-way-coupled method

Numerical simulation of automotive tires is still a challenging problem due to their complex geometry and structures, as well as the non-uniform loading and operating conditions. Hysteretic loss and rolling resistance are the most crucial features of tire design for engineers. A decoupled numerical model was proposed to predict hysteretic loss and temperature distribution in a tire, however temperature dependent material properties being utilized only during the heat generation analysis stage. Cyclic change of strain energy values was extracted from 3-D deformation analysis, which was further used in a thermal analysis as input to predict temperature distribution and thermal heat generation due to hysteretic loss. This method was compared with the decoupled model where temperature dependence was ignored in both deformation and thermal analysis stages. Deformation analysis results were compared with experimental data available. The proposed method of numerical modeling was quite accurate and results were found to be close to the actual tire behavior. It was shown that one-way-coupled method provides rolling resistance and peak temperature values that are in agreement with experimental values as well.

Roughness-Induced Adhesive Hysteresis in Self-Affine Fractal Surfaces

It is known that in the presence of surface roughness, adhesion can lead to distinct paths of loading and unloading for the area–load and penetration–load relationships, thus causing hysteretic loss. Here, we investigate the effects that the surface roughness parameters have on such adhesive hysteresis loss. We focus on the frictionless normal contact between soft elastic bodies and, for this reason, we model adhesion according to Johnson, Kendall, and Roberts (JKR) theory. Hysteretic energy loss is found to increase linearly with the true area of contact, while the detachment force is negligibly influenced by the maximum applied load reached at the end of the loading phase. Moreover, for the micrometric roughness amplitude hrms considered in the present work, adhesion hysteresis is found to be affected by the shorter wavelengths of roughness. Specifically, hysteresis losses decrease with increasing fractal dimension and cut-off frequency of the roughness spectrum. However, we stress that a different behavior could occur in other ranges of roughness amplitude.

Rolling Resistance Revisited

ABSTRACT Rolling resistance defined as energy loss per unit distance is well accepted by the tire science community. It is commonly believed that the dominant part of energy loss into heat is caused by the viscoelasticity of rubber compounds for a free-rolling tire. To calculate the rolling loss (hysteretic loss) into heat, a method based on tire forces and moments has been developed to ease required measurements in a lab or field. This paper points out that, by this method, the obtained energy loss is not entirely converted into heat because a portion of the consumed power is used to compensate mechanical work. Moreover, that part of power cannot be separated out by tire forces and moments–based experimental methods. The researchers and engineers have mistakenly ignored this point for a long time. The finding was demonstrated by a comparative analysis of a rigid, pure elastic, and viscoelastic rolling body. This research mathematically proved that rolling loss into heat is not resolvable in terms of tire forces and moments with their associated velocities. The finite element model of a free-rolling tire was further exercised to justify the concept. These findings prompt revisiting rolling resistance in a new way from the energy perspective. Moreover, an extended definition of rolling resistance is proposed and backward compatible with its traditional definition as a resistive force.

Magnetic Hysteresis Loss Calculations of HTS Coil under Rotating Magnetic Fields

We calculate magnetic hysteresis loss of HTS coil under rotating magnetic field. No transport current through the coil is assumed other than induced current. In order to find the frequency and applied field direction dependence of the loss, we present the loss versus applied field amplitude curves, for the frequencies f=1, 10, 100 and 1000 Hz, for seven different orientations of magnetic field. The hysteretic loss through the SC component increases with increasing frequency. This behavior is a consequence of higher field penetration to the tape at higher frequencies.

Evolution of Meso-Structures for Non-Pneumatic Tire Development: A Case Study

The evolution of meso-structures in the development of the shear band of Michelin’s non-pneumatic tire, the Tweel, is presented in this paper. Designers and researchers at Clemson University worked on a research projects with Michelin to support NIST efforts in fuel efficiency improvement and NASA efforts in manned exploration systems. The goal of each was to replace the elastomeric material of shear band with materials which can tolerate harsh temperatures and shear loads or to replace the materials with linear elastic low-hysteretic loss materials. The concepts initially proposed by ideation method were prototyped for physical testing. A case study examining the documentation reports for each project is conducted to provide a reflective understanding of how the evolution in the projects occurred. The goal of developing this retrospective is to try to identify guidelines and approaches that could be integrated into a designer driven systematic approach for custom design of meso-structures.