Clamping devices with constant force or pressure are desired in medical instruments, such as hemostatic forceps and the artificial sphincter, to prevent soft tissues from injures due to overloading. This paper studies the design method issues in constant force components using superelastic shape memory alloy. A generalized method for generating a constant force components-based shape memory alloy is proposed. An example of a C-shaped shape memory alloy sheet with a thickness of 0.2 mm is presented. The design results using the generalized design method for a C-shaped shape memory alloy sheet with 0.2 mm thickness are compared with its experimental results. Based on the generalized design method, the obtained design solutions for Cases 1 and 2 are coincident with the results obtained by the experiments. It could be seen that the generated design shape of the superelastic shape memory alloy component might obtain constant force within a relatively large deformation range. It is validated that the proposed generalized design method was feasible and effective. It is also illustrated that changing the geometric dimensions of the superelastic SMA component might obtain constant force within a relatively large deformation range.
Keywords: constant force; finite element analysis; generalized design method; shape memory alloy; superelastic.