Non-contacting Residual Stress Measurement by Thermoelasticity

S.-J. Lin, Y.-C. Chou and H.-H. Li
National Kaohsiung University of Applied Sciences, TW

Keywords: thermoelasticity, TSA, residual stress, non-destructive stress analysis

Summary:

Thermoelastic stress analysis (TSA) is a nondestructive and non-contacting experimental technique, which exploits thermoelastic response of materials to provide full-field stress information over a surface. Fundamental thermorelastic theory is based on the thermoelastic effect and that is as a material experiences mechanical excitation, the material gets cooler in tension or warmer in compression. Temperature variation due to thermoelastic behavior can be very small and even approximately attain the order of 10-3. TSA technique utilizes infrared detectors to capture the tiny temperature change on the stressed surface and correlate it to the change in the sum of normal stresses or isopachic stress. Traditionally, theoretical thermoelasticity indicated that for an elastic body under adiabatic and reversible conditions, the rate of temperature disturbance of a dynamically loaded member is linearly proportional to the stress amplitude and the proportionality is defined to be thermoelastic constant. However, recent thermoelastic studies discovered that the thermal response is not only a function of stress amplitude, but mean stress which represents a static component of stress. This work will introduce residual stress measurement using TSA and the corresponding experimental measurements based on 2024 T351 Al alloy will be provided as well.