Abstract
In the present paper, an interfacial strength between thin film and substrate is evaluated by laser ultrasonic waves. The laser beam is irradiated on the substrate which have a thin film on the lower side. The elastic-ultrasonic wave is excited by the laser beam, and it propagates in the transverse direction for the plate. The supersonic wave reflects on the back of monotony, becomes an expansion wave, and reaches the interface. Finally, delamination on the interface is caused by the expansion wave. In the present study, the interfacial stress is estimated by inverse analysis using Laplace-transformed boundary element method. The displacement history on the surface of the specimen can be related by interfacial stress by transfer function. The transfer function can be obtained by numerically by 3-dimensional analysis with boundary element method. The test specimens made from Al substrate and Ti thin film are used in the present study. It is confirmed that the interfacial strength between thin film and substrate is 30.5MPa from the present investigation.
