Investigation of contact acoustic nonlinearity at solid interface

Recently contact acoustic nonlinearity (CAN) has attracted more and more attentions in acoustic nonlinearity studies. In this paper, acoustic nonlinearity caused by an interface between two polished aluminum blocks was studied. The variation of second harmonic signal vs. the amplitude of fundamental signal and the applied pressure on the blocks was measured. The experiment results show that the second harmonic has a great increment when the applied pressure decreases or the input signal voltage, i.e. the input acoustic signal, increases. With the applied pressure 66.4kN/m², the equivalent acoustic nonlinearity parameter β is about 150. When the applied pressure decreases, the β value will greatly increase to several thousand. The results were also compared with J.M. Richardson´s theory