Nondestructive Evaluation of Materials Tensile Strength via Nonlinear Acoustics Data

The nonlinear acoustic approach is assessed for applications as a nondestructive tool for reconstructing stress-strain curves and quantifying the ultimate tensile strength for variety of materials. The direct algorithm uses the polynomial stress-strain expansion up to the third power of strain and the literature data on the second-order nonlinearity parameters to calculate relevant segments of the stress-strain curves. Since the third-order nonlinearity parameters are unknown for majority of materials the calculations used an iteration scheme to obtain closer approximations to the experimental data available from static tensile tests. The solution to the inverse problem identifies the range of the nonlinearity parameters for a given tensile strength and enables to categorize the contribution of the quadratic and cubic nonlinearities in mechanical response for different materials.