Topology optimization of pressure-actuated compliant mechanisms

Topology optimization of a compliant mechanism under pressure input is presented by treating void regions with incompressible hydrostatic fluid. Since an input force is not imposed on one point, existing problem formulations such as attaching a spring on the node under the input force or constraining the input displacement are not valid for the present problem. Instead, to obtain the structural stiffness of a compliant mechanism, the mean compliance by the input pressure is considered. To deal with incompressibility, as an alternative to the mixed displacement–pressure formulation, displacement-based nonconforming finite elements are employed for both two- and three-dimensional problems. The effectiveness of the proposed approach is verified by designing grippers and stretchers.