A Parametric Design Study for Minimizing Bolt Boss Stress of Engine Front Cover

In the automotive engines, knowledge on the thermo-elasticity a priori is very informative in the early design stage. Especially, increasing demand on engine performance and fuel economy has resulted in progressively higher loadings on internal components of combustion engines with lighter weight. Therefore the structural integrity should be confirmed in the early engine design stage otherwise engine development cost will be huge. Cover type components like front cover have shown very high and localized hot spot at the bolt boss flange in many of the engine analyses. A lot of time and effort had been put to reduce this high stress by changing the design, but those have not always been effective. Therefore an effective guideline for cover flange design became necessary. This study describes an efficient and reliable analysis technique for minimizing stress of front cover flange by using automated computer modeling and numerical method. Simplified cylinder head, cylinder block and front cover with joint bolts were assembled and five design parameters of the front cover were selected. The investigation of how those parameters impact the stress values at the flange was carried out. Morpher was used to model modification based on the design parameter with given range. ABAQUS was used to verify the structural behavior of the simplified engine assembly. Isight was used as an optimization environment allowing the integration of those commercial tools. The proposed design parameters were applied to the actual design and the effective stress decrease was confirmed.