Abstract
This paper presents a stiffness-oriented structure topology optimization (TO) method for the design of a continuous, hinge-free compliant mechanism (CM). A synthesis formulation is developed to maximize the mechanism’s mutual potential energy (MPE) to achieve required structure flexibility while maximizing the desired stiffness to withstand the loads. Different from the general approach of maximizing the overall stiffness of the structure, the proposed approach can contribute to guiding the optimization process focus on the desired stiffness in a specified direction by weighting the related eigen-frequency of the corresponding eigenmode. The benefit from this is that we can make full use of the material in micro-level compliant mechanism designs. The single-node connected hinge issue which often happened in optimized design can be precluded by introducing the eigen-frequency constraint into this synthesis formulation. Several obtained hinge-free designs illustrate the validity and robustness of the presented method and offer an alternative method for hinge-free compliant mechanism designs.
Highlights
Numerical engineering examples for topology optimization validate its advantages in terms of systematism and high efficiency, compared with the kinematicsbased approach
It will be shown that the proposed method can be employed to solve the difficult tradeoffs between flexibility and stiffness and to solve the single node hinge issue as well
Optimization results often turn out to be connected with the single node hinge, for the first two examples, the synthesis weighting index (SWI)
Summary
Distributed or hinge-free compliant mechanisms are continuous, monolithic (onepiece) and flexible mechanisms, which can transfer displacement and force from input port to output port in other directions by elastic deformation and have enough stiffness to withstand the external loads as well [1]. Luo et al [19] proposed a new multi-objective formulation for topology optimization of compliant mechanisms which considers to maximum the MPE and minimum the mean compliance simultaneously. Besides energy-based formulation, other approaches to design compliant mechanisms using topology optimization are studied to balance flexibility and stiffness requirements. Pedersen et al [23] introduced a material path-generating method and formulated an objective function for the synthesis design of large-displacement compliant mechanisms which was built by a global Lagrangian finite element formulation. This paper develops a stiffness-oriented structure topological synthesis method to design a hinge-free compliant mechanism in which flexibility and stiffness requirements are considered. It will be shown that the unwanted single-node hinge connection issue has been successfully addressed by introducing the eigen-frequency constraints into the optimization formulation This approach can provide an alternative method for hinge-free compliant design.
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