Topology optimization in the design of stress-constrained compliant mechanisms
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Topology design of compliant mechanisms has gained wide popularity among the scientific community, and their use in the mechanical engineering field is of upmost importance. Local stress constraints are usually introduced in the topology optimization problem of compliant mechanisms to guarantee the attainment of realistic solutions. In this work, an overweight constraint is considered in the design process, replacing the use of local stress constraints. The material distribution in the domain is modeled with a uniform relative density within each element of the mesh and with quadratic B-splines. These strategies to define the material layout require the use of a finite element (FEM) formulation and an Isogeometric based (IGA) formulation, respectively. An input-parameters sensitivity analysis is developed to make a comparison of the two strategies for defining the material distribution of the domain. The sensitivity analysis as well as the evaluation of the importance of introducing stress constraints in the problem are developed by solving some benchmark problems. Regarding the sensitivity analysis of input parameters, the results show that the ratio between the material and the springs stiffness is the parameter with the largest influence on the solutions. On the other hand, the results show that the stress constraints have to be considered in the formulation of the problem to avoid instability and structural integrity issues and obtain the compliant mechanisms with the best performance.
