Two-Dimensional Analyses of Subharmonic Generation at Closed Cracks in Nonlinear Ultrasonics

Nonlinear ultrasonics plays an important role in the detection of closed cracks in critical structures and machines, such as atomic power plants and airplanes. Although the design and operation of nonlinear measurement require realistic modeling and simulation in two dimensions (2D), only one-dimensional modeling has succeeded in reproducing subharmonic generation. In this study, we propose 2D analysis using a damped double nodes (DDNs) with compression residual stress in the finite-difference time-domain method. We then succeeded in reproducing the essential feature of observed subharmonic generation at closed stress corrosion cracks.