Numerical experiments on reflection of transverse waves by inclined free-surface steps and free-surface open slits in ultrasonic flaw detection

摘要

Takahashi has conducted ultrasonic flaw detection experiments on the reflection of transverse waves by an inclined free-surface step and has also performed corresponding calculations using the sound wave theory proposed by Werneyer. The same author has additionally conducted experiments on the reflection of transverse waves by a 1 mm high inclined free-surface open slit and has found a large difference between the experimental and calculated values. To verify the effectiveness of elastic wave theory for quantification of defects, corresponding numerical experiments of the same reflection cases of transverse waves have been performed. The inclination angle of the transverse wave is 45°, and the inclination angles of the steps or cracks range between 0-50° at 10° intervals. The calculated results are found to agree with the experimental ones within a 2～3 dB error. Visualisation of the reflection waves is accomplished with vector diagrams. The physical mechanisms of new reflection phenomena, such as head waves and corner waves, are clarified in detail.