Quantitative Analysis of Subsurface Defects of STS Materials by Finite Element Modelling in Infrared Thermographic Testing

The suitability of infrared thermography is assessed through the estimation of the temperature variation or thermal contrast induced by a defect. In this study, finite difference numerical analysis is applied on the three dimensional solid body with artificially created subsurface defects at some depth to simulate the heat flow in the infrared thermography inspection process. The result shows that the numerical simulation is helpful to optimize the experimental conditions and explain the experimental data for infrared thermographic testing. Numerous experiments have demonstrated that infrared thermographic methods are effective for detection of subsurface defects in the materials. Infrared Thermography is an emerging approach for non-contact, non-intrusive, and non-destructive inspection of various solid materials such as metals, composites and semiconductors for industrial and research interests. Infrared thermography is a non-contact, non-intrusive and non-destructive inspection technique that can be used for the quantitative determination of the sizes and locations of subsurface defects. It utilizes an infrared camera to monitor and record the temperature variation over the viewed surface. The presence of a defect at a certain depth interferes with the heat flow causing local surface temperature variations or any other changes in the thermal properties of the materials. It provides local colourful images of concerning area where local changes of surface temperature indicate surface defects [1-4]. Modelling of infrared thermography testing can help to obtain the physical insight of the thermal phenomena occurring during and after thermal excitation of specimen and fully understand all the aspects of their thermal behaviour. In this research, a finite element method based model has been applied to simulate the thermal phenomena for infrared thermography testing. 2. Numerical Approach