The development of the effective ultrasonic simulation technique based on the superposition technique of points sound source for defect sizing

In recent year, the extremely thick plate becomes used in the deck plate of the large ships. To prevent the brittle fracture it is important to detect and measure the inner defects. If the defect sizing can be accurately measured during the in-service period, the estimation of the residual life becomes possible. Ultrasonic Testing is used in order to inspect the inner defects in a thick plate, and it is necessary to select adequately the probe frequency, size, refraction angle, or another condition to evaluate the defect size accurately. The estimation of the defect size in vertical direction to plate surface is important from the viewpoint of fatigue strength. But the vertical defect size and also the inclined defect size are hardly to be estimated accurately.In this study, the simulation program based on the superposition technique of points sound source was developed to estimate the inner defects in the deck plate precisely by authors. Moreover, the effectivity was clarified by simulation using FEM and experimentation using the test specimens including artificial defects.