Quantitative evaluation of hidden defects in cast iron components using ultrasound activated lock-in vibrothermography

摘要: This paper reports one of the first experimental results on application ultrasound activated lock-in vibrothermography for quantitative assessment buried flaws in complex cast parts. The use amplitude modulated ultrasonic heat generation allowed selective response defective areas within part, as defect itself is turned into a local thermal wave emitter. Quantitative evaluation hidden damages was accomplished by estimating independently both area and depth extension flaws, while x-ray 3D computed tomography used reference sizing accuracy assessment. To retrieve flaw's area, simple yet effective histogram-based phase image segmentation algorithm with automatic pixels classification has been developed. A clear correlation found between (phase) signature measured infrared camera target surface actual mean cross-section flaw. Due to very fast cycle time (<30 s/part), method could potentially be applied 100% quality control casting components.