Assessment of Microbolometer Infrared Cameras for Thermoelastic Stress Analysis

A means of simulating the performance of infrared (IR) cameras is described, with the purpose of assessing the suitability of the IR camera for thermoelastic stress analysis (TSA). The approach is demonstrated on two IR cameras containing different sensors: a standard microbolometer and a very low cost microbolometer based thermal core. The simulations take into account the sensor spatial resolution, the lenses and the sensor sensitivity. The analytical solution for a disc in 2‐point diametral compression (Brazilian disc) is used to generate the simulated thermoelastic response. The results from camera simulations are quantitatively compared with the experimental data, and accuracy and precision of the thermoelastic response relative to the simulated data are established for each camera. The approach highlights the limitations of using microbolometer based cameras for TSA. Additionally, three image processing algorithms for TSA, that is, least‐squares fitting, lock‐in and Fast‐Fourier Transform (FFT), are compared. The study showed that the three algorithms deliver similar results, with the least‐squares fitting using less computational time. Importantly, the results obtained with the thermal core are promising, strongly indicating that multiple camera TSA is a realistic possibility with an outlook to having cameras permanently installed on structures. However, at present, it is clear that the thermal core can only be used in a qualitative sense for TSA, as it has a very low response exacerbated by significant attenuation caused by the intrinsic sensor time constant in microbolometer‐based IR detectors and inbuilt software‐based noise reduction procedures.