This presentation was made at the 2019 NAFEMS World Congress in Quebec Canada

Resource Abstract

The engine cylinder head is one of the most critical components in an automotive power train system. It is an essential point for engine block designers to know the shape in order to fulfill their requirements. Owing to bolt tightening force between cylinder head and block with gasket and thermal loading (cooling down and heating up periodically) in combustion chambers, the contact pressure distribution in the boundary surface between head and block is significantly influenced by the external loading. The usage of topology optimization for head and/or block enables us to find the averaged contact pressure distribution by shaping the stiffness distribution. It may be one of the major solution candidates for almost all analysts who are accustomed to use structural FE solver every day.



The main purpose of this study is to confirm the advantage of topology optimization considering contact conditions. The process of generating a new shape of a cylinder head is shown by one virtual engine model. In this study, it is also emphasized that the nonlinear material characteristic and different initial gap widths of several gasket parts are not modified. The complex structure assembled by multiple parts has several contact regions. The all-in-contact condition is guaranteed by the constraint conditions during optimization process. The contact pressure strongly depends on the stiffness distribution. To avoid leaking fluid or gas to outside, the limited and the averaged contact pressure should be kept beyond the defined constraint conditions.



In this topology optimization, the first constraint condition is to keep averaged contact pressure beyond a given value. And the second constraint condition is defined to be controlled by the bore distortion within the reference value. Under both constraint conditions, the minimum weight of cylinder head is calculated as an objective function through the complete optimization process.



The example model is calculated and the optimization is performed with the industrial software PERMAS. Special emphasis is placed on the run time, because topology optimization with contact calculation are often seen as run time critical.