Elastoplastics Modeling of the Spark Plug Final Assembly Process

The spark plug final assembly process plays an important role in the performance and quality of spark plugs. In this paper methods of computer modeling and analysis of complex assembly processes for engine components such as the spark plug are presented. The final assembly process is simulated as a loading history consisting of thermal and mechanical loadings. The movement of the crimping die is modeled as a rigid surface deforming the shell, pressing the insulator down, and deforming the gasket. Combinations of different types of finite elements were employed to simulate the assembly process. A new modeling technique for the gasket deformation which uses much less computation time is presented. This is accomplished by considering the gasket to be pressed between two rigid surfaces. The contact pressure is then substituted back into the full model. Finally, the die is moved back from the fully compressed position to its initial position and the structural spring-back and residual stresses are determined. All analyses were performed using the nonlinear finite element code ABAQUS [1]. The elastoplastic stress and deformation fields of the shell, crimp, gasket, and insulator are discussed and suggestions for approaches to other problems are made.