This paper presents the direct application of topology optimization to the design of shape memory alloy (SMA) thermal actuators. Because SMAs exhibit strongly nonlinear, temperature-dependent material behavior, designing effective multidimensional SMA actuator structures is a challenging task. We pursue the use of topology optimization to address this problem. Conventional material scaling topology optimization approaches are hampered by the complexity of the SMA constitutive behavior combined with large actuator deflections. Therefore, for topology optimization we employ the element connectivity parameterization approach, which offers improved analysis convergence and robustness, as well as an unambiguous treatment of nonlinear materials. A path-independent SMA constitutive model, aimed particularly at the NiTiR-phase transformation, is employed, allowing efficient adjoint sensitivity analysis. The effectiveness of the proposed SMA topology optimization is demonstrated by numerical examples of constrained and unconstrained formulations of actuator stroke maximization, which provide insight into the characteristics of optimal SMA actuators. Key words: shape memory alloys; NiTi; topology optimization; element connectivity parameterization; geometric nonlinearity; material nonlinearity@en

This paper presents the first application of topology optimization to the design of shape memory alloy actuators. Shape memory alloys (SMAs) exhibit strongly nonlinear, temperature-dependent material behavior. The complexity in the constitutive behavior makes the topology design of SMA structures intractable by the conventional element density-based topology optimization. Therefore, in the present study, the recently developed element connectivity parameterization (ECP) formulation is applied, which offers important advantages for complex nonlinear topology optimization problems. A history-independent constitutive model of SMAs is employed which allows efficient adjoint sensitivity analysis. The effectiveness of the proposed technique is illustrated by several numerical examples.@en

This paper presents the application of systematic model-based design techniques to the design of Shape Memory Alloy (SMA) actuators. Shape memory alloys are promising materials for (micro-)actuation in space applications, because of the relatively large deformations and forces that can be achieved. However, their complex constitutive behavior and the fact that several physical domains (electrical, thermal and mechanical) are involved makes the design effective SMA actuators with complex shapes and layouts challenging. Hence, design optimization techniques are expected to play an important role in the further development of SMA actuators. This paper presents shape and topology optimization of SMA structures and shows the effectiveness of these design approaches by several representative examples.@en