Durability Investigation of Cast Iron Cap Inserts in an Aluminum Bedplate of a Turbocharged 2.2L ln-Line-4 Gasoline Engine

This paper presents a study on the durability of cast iron cap inserts in an aluminum bedplate of a turbocharged 2.2L gasoline passenger car prototype engine under full load. This engine component was chosen for analysis as it is an element of essential importance in overall powertrain structural integrity especially for an engine with higher peak cylinder pressures due to forced induction engine operating condition.

A Finite Element Method (FEM) analysis was carried out to investigate the durability of various cap insert designs. Cap inserts under full load can induce high stress regions in the model, which may indicate likely failure areas on the component. Iterative simulations were performed to measure and characterize both the tensile and compressive stress regions in different cap insert designs using the combined Thermal, Assembly and Firing conditions of the engine. A Fatigue Safety Factor algorithm of the stress results was then built across all relevent crank angles using the Modified Goodman criterion to identify locations of low durability for bedplate design improvement.

Additionally, a comparative analysis using a higher grade cap insert material was performed to study the influence of material strength properties on component durability. The abovementioned FEM activity and supporting analysis results assisted crankcase designers in better understanding how to optimize the turbocharged engine cap insert component whilst at the same time preventing possible bedplate failure.