Ultrasound lock-in thermography for advanced depth resolved defect selective imaging

Ultrasound lock-in thermography('attenuation mapping') is a defect selective 'dark field' NDT technique with a high probability of defect detection (PoD), since only defects produce a signal while other features are suppressed. The basic contrast mechanism is the enhanced local mechanical loss turning a variably loaded defect into a heat source. The method is being applied for quality maintenance, for example in the aerospace and automotive industry to monitor the integrity of thermal features. A variety of examples will be presented to illustrate how well the method is suited to locate defects and to distinguish their depths.