TOPOLOGY OPTIMIZATION OF COMPLIANT MECHANISMS WITH STRENGTH CONSIDERATIONS*

Multicriteria formulations that have been reported previously in topology design of compliant mechanisms address flexibility and stiffness issues simultaneously and aim to attain an optimal balance between these two conflicting attributes. Such techniques are successful in indirectly controlling the local stress levels by constraining the input displacement. Individual control on the conflicting objectives is often difficult to achieve with these flexibility-stiffness formulations. Resultant topologies may sometimes be overly stiff, and there is no guarantee against failure. Local stresses may exceed the permissible yield strength of the constituting material in such designs. In this article, local failure conditions relating to stress constraints are incorporated in topology optimization algorithms to obtain compliant and strong designs. Quality functions are employed to impose stress constraints on retained material, ignoring nonexisting regions in the design domain. Stress constraints are further relaxed to regularize the design space to help the mathematical programming algorithms based on the Karush-Kuhn-Tucker conditions yield improved solutions. Examples are solved to corroborate the solutions for failure-free compliant topologies that are much improved in comparison to those obtained using flexibility-stiffness multicriteria objectives. *Communicated by S. Azarm.

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