The Study of Inspection on Thin Film Resistance Strain Gauge Contact Failure by Electrical Excitation Thermal-Wave Imaging

Contact failure as one of primary failures, which occurs between thin film resistance strain gauge (FRSG) and metal measured objective substrate, seriously influences the measurement validity and precision of the strain gauge. In this article, an electrical excitation thermal-wave imaging (EE-TWI) method is proposed for the inspection of contact failure. Equivalent circuits of the contact resistance under an external electrical source are used to identify the location of the contact failure. Long pulse thermography and lock-in thermography (LIT) are experimentally studied on the detection of contact failure. Pulsed phase thermography and principal component thermography in long pulse thermography as well as the amplitude, quadrature component in LIT are desirable to form the EE-TWI feature images, respectively. A graph-based segmentation method is employed to distinguish and localize the contact failure from EE-TWI images. EE-TWI provides a powerful tool for the contact failure evaluation of integrated thin film resistance strain gauge (FRSG) and has a significant potential to ensure the thin FRSG sticking performance and quality with application of mechanical properties measurements.