Random vibration fatigue of welded structures - Applications in the automotive industry

Abstract

The automotive industry is facing its most significant transformation since the first Ford factory. The rise of electrical vehicles alongside autonomous driving and additive manufacturing increase demand for lightweight vehicles, which requires proper numerical analysis tools in place in order to keep the costs low and to achieve durability targets. Vibration in heavy and light-duty vehicles poses many challenges in the design phase mainly due to the uncertainties associated with the loads and material properties. Therefore stochastic methods have attracted the attention of engineers responsible for the fatigue assessment of truck chassis and their welded attachments. In order to address the mesh scale sensitivity in the finite element method (FEM), Dong et al created the Battelle Structural Stress Method, an elegant alternative to the Volvo nodal force/moment method which was named Verity®. For fatigue life evaluation of welds Verity® is used in conjunction with a master SN curve also developed by the same authors. The present paper proposes a frequency domain variant of the Verity® Method to be used in random vibration fatigue applications along with Dirlik and T&B methods. Frequency domain approaches enjoy the statistical advantage of using probability density functions instead of rainflow cycle counters, which offers computational benefits (in terms of time) in multi-channel long history scenarios. This paper thoroughly describes the proposal and shows an example of its application to a brake chamber support attached to the rear axle of a light-duty truck. Verity is used in the both the time and frequency domains and the fatigue results are compared.