Applying Modeling and Simulation to Evaluate Field Failure Modes: a Case Study in Starter Drive Application

In response to several field failures of a specific model of starter drive - which is a component of starter motors used in Internal Combustion Engines (ICEs), - for application in heavy duty vehicles, a systematic Root Cause Analysis (RCA) was conducted in warranty returned parts. Controlled laboratory tests were not able to successfully replicate the failure mode. The failure caused the disassemble of the starter drive and it has become a difficult task to determine the root cause and propose solutions to fix the problem, therefore a deeper analysis of the warranty data was carried out by using both finite element analysis (FEA) and lumped parameter dynamic modeling and simulation. The FEA model was used to check potential weakness of the structural design that could point out the failure cause. The dynamic model was developed in order to evaluate effects such as impact loads, much higher than that expected by the static analysis, by consequence of the high relative velocity and resulting accelerations of components in contact during the short period of time in which the startup process of ICEs occurs. A potential root cause was determined and experimental pull tests and engine bench durability cycle tests confirmed the accuracy of the simulation models. Hence, the use of simulation tools can be considered as important aid when non-obvious field failure analysis are needed to speed up the implementation of a more reliable and robust design. Moreover this strategy minimizes well known deleterious consequences generated by recurring field failures that remains for a long time without an effective solution.