Design and Experimental Verification of Pseudoelastic-Based Constant-Force Springs

Constant-force springs were designed with Ni-Ti pseudoelastic alloy. Through local concentration of flexural deformations, the design produces “pseodoelastic hinges” under relatively small deformations. Constant moments at these “pseudoelastic hinges” produce a relatively constant level of spring force under increasing deformations. Local concentration of flexural deformations are achieved in this design through bracing the spring element outside the locations where deformations concentrate. Experimental data verified the desirable constant-force behavior of the springs and their desirable fatigue life, relaxation attributes, and corrosion resistance. The pseudoelastic spring design presented here is subject of approved and pending U.S. patent applications.