Simulation On Ultrasonic Nonlinear Characteristics Of Aluminum Plastic Damage

In this paper,the simulation model of electromagnetic ultrasonic nonlinear is set up and applied in the 6061 aluminum alloy specimens with plastic deformation to study the relationship between the nonlinear and the plastic deformation,and the simulation results are verified through the experiment.The main research work is as follows:(1)According to the strain energy function of Murnaghan model,this paper deduced the relationship between the Murnaghan model parameters and the plastic damage;Based on the third harmonic constitutive model,studied the relationship of third harmonic amplitude and nonlinearity.The tension and compression asymmetry coefficient is used for characterization of nonlinearity.(2)Establishes the simulation model of electromagnetic ultrasonic detecting nonlinear plastic damage based on the Murnaghan model.Quantifies the relationship between the plastic damage and nonlinearity by the changes of the second harmonic amplitude.According to the variation of second harmonic amplitude and the strain energy function,determined the area and the state of plastic damage.(3)Establishes simulation model of electromagnetic ultrasonic detecting nonlinear plastic damage based on the third harmonic constitutive model.The changes of third harmonic amplitude are analyzed by changing the nonlinearity.Introduces the relative asymmetric nonlinear coefficient and analyses the relationship of the third harmonic and nonlinearity qualitatively.(4)Make an experimental verification on the aluminum plates with varying degrees of plastic damage using nonlinear electromagnetic ultrasonic system.Spectrum analysis is carried out on the experimental data and study the relationship between the plastic damage degree of the aluminum plates and the nonlinearity.