Designing a lightweight and durable engine is universally important from the standpoints of fuel economy, vehicle dynamics and cost. However, it is challenging to theoretically find an optimal solution which meets both requirements in products such as the cylinder head, to which various thermal loads and mechanical loads are simultaneously applied.
In our research, we focused on “non-parametric optimization” and attempted to establish a new design approach derived from the weight reduction of a cylinder head. Our optimization process consists of topology optimization and shape optimization. In the topology optimization process, we explored an optimal structure with the theoretically-highest stiffness in the given design space. This is to provide an efficient structure for pursuing both lightweight and durable characteristics in the subsequent shape optimization process. The shape optimization process used the result achieved in the topology optimization to obtain a detailed shape having lightweight properties while satisfying high-cycle fatigue strength by coupling it with the fatigue analysis software. In addition to the requirement of high-cycle fatigue strength, various constraints were taken into account simultaneously such as functional constraints including gasket contact pressure and manufacturing constraints including minimum wall thickness or demolding.
As the results of this optimization research demonstrate, 14% weight reduction from a cylinder head designed by conventional means was accomplished. This result validates that the established approach is both practical and effective at reducing the weight of the cylinder head with fulfilling a variety of requirements in design.
