Design and Testing of a Thin-Flexure Bistable Mechanism Suitable for Stamping From Metal Sheets

We present a new technique for fabricating compliant mechanisms from stamped metal sheets. The concept works by providing thinned segments to allow rotation of flexural beams 90 deg about their long axis, effectively providing a flexure as wide as the sheet's thickness. The method is demonstrated with the design and fabrication of a metal bistable mechanism for use as a threshold accelerometer. A new model based on elliptic integral solutions is presented for bistable mechanisms incorporating long, thin flexures. The resulting metal bistable mechanisms are tested for acceleration threshold sensing using a drop test and a vibration test. The mechanisms demonstrate very little variation due to stress relaxation or temperature effects. The force-displacement behavior of a mechanism is also measured. The mechanisms' switching force is less than the designed value because of out-of plane motion and dynamic effects.