Inspection of thin film resistance strain gauge contact failure using electrical excitation thermal-wave imaging

Peng Song, Junyan Liu, Fei Wang and Yunji Xie


Contact failure as one of the primary failures, which occurs between thin film resistance strain gauge and metal measured objective substrate, seriously influences the measurement validity and precision of the strain gauge. In this work, 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 (LPT) and lock-in thermography (LIT) are experimentally studied on the detection of contact failure. Pulsed Phase Thermography and Principal Component Thermography in LPT as well as the amplitude, and 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 and has a significant potential to ensure the thin film resistance strain gauge sticking performance and quality with the application of mechanical properties measurements.

Automated Defect Detection for Epoxy-Carbon Prepreg Laminates in Data Fusion Approach

Xavier Maldague, Pengfei Zhu, Ziang Wei, Zahra Omidi, Geoffrey Marchais, Thibault Boulanger and Pierre Servais


Fibre-reinforced polymer composites have become widely used materials in the manufacturing of aerospace, boat building, and automotive, due to their high specific stiffness and strength, chemical resistance, etc. However, the curing process has a major influence on void content and fibre-matrix interface, affecting the quality of the composite part. In this work, non-destructive testing based on infrared thermography and shearography is used to detect the subsurface defects and impact damage in epoxy-carbon prepreg laminates. Different data fusion methods are used for the incrementing of the detection ability. For the requirement of industrial applications, an automated defect detection method named YOLOv7 is performed in the data fusion view. To improve the detection ability of YOLOv7, a data augmentation method named MixUp is used to construct the datasets obtained from the simulation. The experimental results show the excellent detection capacity of the proposed method. Furthermore, the experimental results also illustrate that the data fusion technique of the Dempster-Shafer method has the best effect compared with the other methods.

Thermographic visualization of non-stationary high speed flow in a channel

Murat Muratov, Irina Znamenskaya, Elizaveta Karnozova and Alexander Lutsky


This paper explores the possibility of non-invasive heat fluxes visualization and analysis of high speed channel flows using infrared thermographic registration. Panoramic IR imaging was performed as the plane shock wave have passed through the test chamber and diffracted on a rectangular obstacle \((6 \times 2 \times 48\, mm )\) on the wall in the shock tube channel \((24 \times 48\, mm)\). The evolution of the heat fluxes maps on the test chamber inner walls (IR-transparent windows) are recorded using a high-speed infrared recorder with operating range \(1.5 - 5.1\, \mu m \). The images of thermal fields were compared with shadow imaging and two-dimensional numerical simulation of the non-stationary gas-dynamics flow around after the shock wave diffraction on the ledge.