Method of Finite Differences in Time Domain. Calculating Echo Signals in Anisotropic Inhomogeneous Materials, Pattern Noise

Abstract

When developing ultrasonic testing techniques for such complex objects as composite welds, the method of finite differences in time domain (FDTD) can be used to calculate echo signals in numerical experiments. Since the FDTD method is based on explicit numerical solution of the wave equation for an elastic medium, it can be used to take account of such effects as the emergence of a run round wave on a volume reflector, the transformation of a longitudinal wave into a lateral one under scattering of ultrasound by a crack, and the rescattering of pulses between reflectors and test-object boundaries. Applying the FDTD method to modeling the propagation of ultrasound in the sample with a high pattern noise and in the samples made of anisotropic inhomogeneous materials is substantiated. The FDTD calculation of the direct problem of propagation of elastic vibrations in a solid may prove useful when solving the inverse problem of ultrasonic nondestructive testing.