Investigation of an automotive subsystem submitted to vibration loads considering scatter of influence parameters

Modern vehicles contain numerous subsystems for comfort, safety, electrification and autonomous driving functions that are mounted to the body-in-white structure. These subsystems are submitted to stochastic vibrational loads induced mainly by the road unevenness. The vibration fatigue behaviour of the subsystems and their connection to the body-in-white structure depend on a great number of influence parameters and associated uncertain scatter bands that are usually unknown and difficult to consider in the design process. This study investigates the oscillation behaviour and fatigue life of a current car component excited by vibrational loads focusing on scatter of relevant influence parameters (mass, stiffness) on a pronounced statistical sample basis. An experimental modal analysis is used to determine eigenmodes and damping characteristics for the three variants: nominal value, increased mass and reduced stiffness. As a further experimental investigation vibration fatigue tests are performed. A probabilistic approach using a simulation tool chain with the aid of commercial computer aided engineering (CAE) programs is proposed to consider scatter effects on the fatigue life of the component submitted to vibration loads and its connection to the body-in-white structure. The simulation fidelity when using uncertain broader scatter bounds is compared to simulation fidelity using both measured data and modal analysis output. Furthermore, correlations between the vibration behaviour and the fatigue of the component are derived. Finally, the hardware fatigue tests results are compared to the simulation results. A very good agreement for eigenmodes, frequency response functions and fatigue lifetime was observed between simulation model and experimental findings. A significant accuracy improvement of the fatigue life simulation using the introduced probabilistic simulation method considering measured scatter bounds for uncertain input parameters is presented.