Burst phase angle thermography with elastic waves

Defect selective non-destructive testing methods are increasingly being used for safety relevant applications in aerospace and related fields(1). The main advantage is the clarity in interpretation of such methods: defects are revealed while non-relevant structural information is suppressed. One way to achieve defect selectivity is the combination of mechanical load to generate heat inside a sample and thermography to detect the resulting thermal waves(2,3). Ultrasound Lock is one example of an established defect selective testing method described previously(4,5). In this paper, several kinds of excitation sources and modulation shapes are discussed.