Analysis of the behavior of a Shape Memory Alloy beam under dynamical loading

Shape Memory Alloys (SMAs) are widely studied as new materials with potenti al for use in various passive or active vibration isolation systems. Up to now, few papers deal with a precise description of their proper dynamic beh aviour. However, it is important to clearly understand the dissipation mech anisms in order to optimize the design of a structure. We present here a de tailed characterization of a Cu-Al-Be beam. The stress induced phase transf ormation austenite --> martensite produces a strongly nonlinear behaviour. The aim of this study is to confront experimental results to a rheological model of the beam. The experimental setup consists in a cantilever beam exc ited by a light electromagnetic actuator. The response is measured by an ac celerometer fixed at the free end of the beam. Stepped sine measurements ha ve been performed around the frequency of the first mode of the beam under different excitation levels. The obtained frequency response functions stro ngly depend on the global vibration amplitude. Then a specific finite eleme nt model has been designed, taking into account the geographic repartition of the two phases inside the beam. The simulations show a similar behaviour and allow the interpretation of the experimental observations. (C) 2001 Ed itions scientifiques et medicales Elsevier SAS.