New Methods for Nonlinear Damping Identification of Damping Alloy

This paper presents two methods for the identification of nonlinear internal damping of alloy. One is the moving autoregressive model (MARM) method, and the other is the time-varying autoregressive model (TVARM) method. These procedures have been successfully implemented on two numerical examples. Comparison between simulation results demonstrates that the computation accuracy of the TVARM method is higher than that of the MARM method. In the experiments, the internal damping properties of the alloy Al-33Zn-6Si are researched, employing the rectangle beam with a nonuniform stress field and the trapezoid beam with a quasi-uniform stress field, respectively. Experimental results show that the internal damping of the alloy increases with the increasing strain and appears a nonlinear behavior. Moreover, the damping values of the trapezoid beam are relatively higher than those of the rectangle beam. Compared to the MARM method, the TVARM method can give a better description of nonlinear damping because the relation curve of loss factor versus strain obtained by the TVARM method is smoother than that obtained by the MARM method.