Influence of air pressure on the micro-beam dynamics

The knowledge of materials mechanical properties is essential for the design of Microsystems. In this context, an experimental technique is proposed for the characterization of materials in small dimensions and in surrounding air at various pressure levels. Dynamic tests were performed on a cantilever beam made of single-crystal silicon, mounted on a support excited by a shaker. The dynamic responses recorded by a Laser vibrometer lead to the modal parameters identification in order to determine their evolution when the excitation amplitude and the air pressure inside the Vacuum chamber are changed. An analytical simulation with the Hosaka model is also presented, which is in good agreement with the experimental results. Then a nonlinear modal identification is performed. It is based on the logarithmic decay method applied in the time-frequency domain thanks to the wavelet transform of the time responses. The evolution of natural frequency and modal damping versus the vibration amplitude is identified for many values of pressure, from the primary vacuum to the atmospheric pressure.