Multibody Dynamic Simulation of a Double ‘A’ Suspension Focusing on the Lower Control Arm Fatigue Life Analysis

Abstract

A vehicle suspension subsystem consists of springs, shock absorbers and linkages, which attach to the wheels and chassis. The interaction between vehicle suspension and road generates dynamic forces in the suspension subsystem. In fact, vehicles travel at variable speed suffering a wide spectrum of vibrations and, usually, road profiles describe the roughness of the pavement surface, which represent their elevation as a function of a distance traveled or time. Consequently, suspension subsystem undergoes complex loading history that never reaches a level sufficient to cause failure in a single application. This means that components may fail due to fatigue. At this context a Double A suspension, which has two sets of linkages called lower and upper control arms, could fail by fatigue according to MBS and FEA. Thus, this work aims to present a MBS analysis of a Double A suspension submitted to a random road profile using a multibody commercial software. The fatigue life analysis focus in the lower control arm (LCA). For this, forces components (longitudinal, vertical and lateral force) and torques, composed by eleven loading history acting on pre-defined points at the LCA, characterize the response of the component in such a situation. In fact, forces computed by multibody simulations improve the FEA by providing better assessment of how they vary throughout the random profile. For FEA, a methodology is proposed to simplify the loads acting at this element and perform the fatigue analysis by finite element method, in which transient analysis was performed. This work represents a secondary stage of a broader study concerning the proposition of a constant amplitude proportional loading road profile based on the fatigue life results obtained from the complex loading history. Thus, it is expected to obtain in future works a simple signal to reproduce in numerical simulations, especially in fatigue analysis, and in experimental tests.