Robust Design of an Automotive Polymer Component EGR Valve Position Sensor Rotor

Due to the increasing application of polymer material in structural components within automotive industry, the application of robust structural design becomes increasingly more important. In this paper, a fractured polymer component, a position sensor rotor from a heavy-duty diesel Exhaust Gas Recirculation (EGR) valve, was studied in detail by finite element methods (FEM). This process included three stages. First, a 3D nonlinear FEM (contact element) was constructed and sensor rotor stress and deformation were obtained under assembly and operation environments. The Coulomb-Mohr failure theory was employed to evaluate the existing design margin relative to the load cases understood from the application. In the second stage, a design sensitivity analysis was performed to select the robust design alternatives from among several improved designs. This was conducted via the utilization of both FEM results and analytical approximation solutions, which were developed using elastic mechanics to validate FEM results. In general, the FEM results were found in good agreement with the elastic mechanics solutions. Thirdly, the comprehensive design criteria were established based on polymer material behavior of crazing and local yield initiation at operating temperatures. These techniques were used to evaluate the final design adequacy using the results from 3D nonlinear FEM study. Finally, a structural reliability assessment was conducted on the baseline and three new designs, which showed that the final design of sensor rotor is robust with high reliability. It successfully passed both the rigorous analytical criteria as well as physical product testing.