Fatigue life enhancement of automobile wheel disc considering multi-axial stresses based on critical plane approach

Abstract

We report an optimization procedure of automobile steel wheel fatigue life enhancement considering multi axial stresses based on critical plane approach via Design of experiments (DOE), Response surface methodology (RSM) and reflective Newton methodology. The wheel disc stiffener shape was optimized by defining seven parameters of the stiffener shape (design factors). Central composite design of experiments theory was used to select a minimum but sufficient combination of the design factors, FEM analysis was used to compute the stresses in the disc wheel under cornering load for each design factor combination. To verify the FEM modeling, we conducted an experimental fatigue test. The stress components variation for any arbitrary direction of loading were estimated and the multi axial fatigue and critical plane approach were used to evaluate the margin to fatigue damage. We found that stress components for only three radial loading directions of the rotating force are required to obtain sufficiently accurate stress histories at critical point and critical direction. A clear method was introduced regarding the correct shear stress range selection on critical plane. The RSM, a quadratic surface, was fitted to analytical results regarding the mentioned models. To verify the accuracy of the fitted surface, the responses at the design factors combinations were calculated via the identified quadratic model and compared to the FEM analysis results. Optimum value of design factors was obtained through reflective Newton method which led to generation of the refined wheel stiffener shape. The proposed method for determining the stress components could be used in any similar rotating parts such as wheel hub, brake disc, brake drum, etc.