Robust Design of Automotive Inverter Components using Tests and Simulations

Vibration qualification tests are indispensable for vehicle manufacturers and suppliers. Carmakers’ specifications are therefore conceived to challenge the mechanical endurance of car components in the face of numerous in-service detrimental phenomena: In automotive industries, components are commonly qualified by means of a test without failure, the goal being to determine whether it will or not "pass" customer requirements. Validation of newly designed components is obtained via bench test and structural simulation. Simulation has gained traction in recent years because it represents the first step of the design validation process. In particular, FEA simulations are powerful to predict the dynamic behavior of physical testing on prototypes, enable engineers to optimize the design and predict the durability. This paper illustrates how FEA simulations were applied to product validation in the pre-serial phase to optimize manufacturing process. In particular, we will focus on the PCB of an electrical driven compressor (EDC), undergoing final vibration validation tests up to failure to reinforce the product. Two failure modes were identified and fixed thanks to simulation's iterations. The first failure mode regarded one of the PCB components: the simulation results lead to a more reliable manufacturing process, particularly to the additional damping element (glue) and its optimal position on the critical PCB elements. The second failure mode concerned the optimization of the screwing torque that holds the PCB rigidly with the housing. Understanding various screws angles and torque values sensibly ameliorated the mechanical endurance of the PCB during the shaker test. The novelty of this approach lies in using simulations to control the PCB's dynamic response (e.g., optimizing applied glues to avoid stress concentration) and optimizing the PCB assembly components. In addition to simulation, controlling screw angle in testing is essential for achieving a uniform assembly process, thereby reducing the risk of variability-induced stress concentrations.