Guided wave nondestructive testing of axial stress in the stud

Longitudinal guided wave and flexural guided wave are used to nondestructively test axial stress in the stud. Based on the theory of elastodynamics, the longitudinal guided wave and flexural guided wave group velocity dispersion curves for M22 stud were calculated. And the optimum frequencies of excitation wave for testing axial stress were obtained, which are ranging from 50 kHz to 80 kHz. In this frequency domain, only two guided wave modes exist: L(0, 1) and F(1, 1) and the dispersion properties for those two mode are weak. The propagation velocities of longitudinal guided wave and flexural guided wave with different frequencies in the stud under axial stress σ were also calculated. The results show that both longitudinal and flexural guided wave group velocities decrease linearly with the increasing of axial stress in the stud. By testing the time that longtitudinal and flexural guided wave spend propagating in the stud which is under axial stress, the value of axial stress can be determined easily.