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In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

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Two sets of experiments are performed to examine the delamination mechanism of ultra low-k material during chemical mechanical polishing (CMP): (i) a macro-scale polishing test using a metallographic polisher and (ii) a micro-scale scratch test on a micro-tribometer. Delamination has been observed at higher pressures in both sets of experiments and the relationship between delamination rate and pressure has been established. Contact mechanics models are proposed to correlate results from the two sets of experiments, combining a Weibull model of failure with a statistical asperity contact model. Results confirm the usefulness of the combined testing procedure in predicting safe polishing pressures during CMP.

Three elements of work are described: (i) a contact mechanics model of the polishing pad, used to predict asperity pressures, (ii) micro-tribometer tests on wafers coated with low-k material and (iii) CMP tests on wafer samples. Delamination of low-k samples is observed at higher pressures in both the micro-tribometer and CMP tests. The correlation between the two tests confirms the usefulness of this combined approach to developing process maps of CMP.