Keywords: optimization, topology, compliant, mechanism, evolutionary, FEM.

This work presents a new procedure for compliant mechanism design. The proposed method is based in a modified version of the evolutionary structural optimization technique (ESO) which has been adapted for its application in topology optimization of compliant mechanisms. Most research in the last decades considered this method for compliance structural optimization almost exclusively. However, the application of this procedure for optimum design of compliant mechanisms has not been studied extensively. Here an additive version of this procedure is proposed to deal with this type of optimization. An area where the use of compliant mechanisms is advantageous and plays a very important role is in micro electro mechanical systems (MEMS) design, since they can be manufactured at a very small scale. Recently, topology optimization has become an efficient tool for automatically conceiving these kinds of monolithic elements [1]. To realize such a design methodology, formal techniques of structural topology optimization were adopted but the design goals were modified specifically to suit the functional requirement of compliant mechanisms.

The proposed procedure is based in the evolutionary structural optimization method [2], which has been successfully applied to several optimum material distribution problems, such us stiffness, frequency or buckling problems. Nevertheless, even if the ESO method has been used commonly for maximum stiffness design of structures, its viability for compliant mechanisms design has not been tested yet. The present paper aims to progress in this work direction. It will be shown that an additive version of this method must be adopted in order to achieve the optimum design, since the traditional ESO method's element removal technique is not efficient in this case. The proposed method will apply the objective functions and restrictions suggested in previous works, as well as original formulations and alternative approaches derived in this investigation which improve the solutions obtained by other authors.

The unwanted formation of checkerboard patterns is prevented by an enhanced version of the classical smoothing technique frequently adopted when evolutionary topology optimization is applied. Here we introduce a variable smoothing order, which means that the number of smoothing iterations is not constant through optimization process. The proposed method has been tested in several numerical applications and benchmark examples to illustrate and validate the approach, and satisfactorily applied to the solution of two-dimensional examples.

1

M.P. Bendsoe and O. Sigmund, "Topology Optimization. Theory, methods and applications", Springer-Verlag, New York, 2003.

2

Y.M. Xie and G.P. Steven, "Evolutionary structural optimization", Springer-Verlag, London, 1997.

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