Low-Cost Thermoelastic Stress Analysis

Abstract

The popularity of thermoelastic stress analysis (TSA) has been hampered by the high capital cost of the equipment, the need for a cyclic load and for a surface with uniform emissivity. Current commercially-available TSA systems allow data to be collected when the component of interest is subject to random loading which has broadened the potential applications of TSA. Recent work has shown that matt black paint, which is traditionally applied to achieve uniform emissivity, is not necessary and aerospace primers are adequate for TSA work. At the same time, a number of investigators have explored the use of microbolometers as a lower cost alternative to the staring array cameras that form the core of the commercially available TSA systems and are a major component of the high price tag. However, the cost of microbolometers is still measured in the thousands of dollars; and so, the use of low-cost, chip-mounted infrared sensors has been explored in the EU H2020 project INSTRUCTIVE. The results demonstrate that, using a simple algorithm implemented in MATLAB and a sensor costing a few hundreds of dollars, it is possible to obtain TSA data from a cyclically-loaded test specimen. The quality of the results is proportional to the investment in the sensor but nevertheless the low-cost affordable approach yields useful results and offers the potential for TSA to be used in structural health monitoring to provide early warning of damage to a structure.