Effect of manufacturing processes on structural fatigue strength and life prediction method of automobile wheel bearing

Vo-Huu-Thuc Nguyen

Value for the audience

The presentation will introduce the influence of different processes on the ultimate fatigue endurance of wheel bearing, based on the numerical simulations and experimental fatigue tests. A case study on NTN Europe bearings help reveals the effects of the prestrain, the residual stresses and their relaxation, and the surface rugosity resulted from fabrication phases on the component, especially the effect of forging, shot blasting, orbital forming and heat treatment.
Audience will get familiar with and understand the geometrical optimization during dimensionning step at NTN Europe to ensure the reliable prediction results, the relation between fabrication processes and fatigue strength of the component, the tools used to simulate and predict fatigue life of wheel bearings. Audience will also get in-depth discussion about the aspect of structural fatigue which is less frequently studied by wheel bearing manufacturers, and the effect of manufacturing processes which is a potentially more promising field of research for bearings manufacturers as new generations of wheel bearings are being developed.

Summary

The aim of this study is to propose a reliable and generalizable flexible numerical approach for the structural fatigue life calculation of automotive wheel bearings. The proposed methodology will take into consideration the impact of the manufacturing processes, including forging, shot blasting, heat treatment and orbital forming on the structural high cycle fatigue resistance of the component. Note that Rolling Contact Fatigue of the component is not considered in this work. The influences of pre-strain, surface condition and residual stresses will be characterized by fatigue tests at different levels: normalized specimens, elementary structures and the component. The results of the fatigue tests on normalized specimens with different surface conditions and under different load ratios will be compared with the results obtained by validation tests on the wheel bearings to determine the security zone in which there is no risk of cracking the component. Fatigue tests on elementary structures will make it possible to further understand the cracking mechanisms by decoupling the effects of different fabrication processes. Based on these experimental data and the analysis of the tested samples, fatigue criteria adapted to each critical zone of the bearing will be developed. These will be implemented into a numerical simulation workflow, including the manufacturing process and the use of the final component, with the commercial finite element software, Forge and Abaqus. The final objective is to improve the precision and reliability of the structural fatigue life predictions.

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