| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系 === 106 === Thermoelastic Stress Analysis (TSA) is a contemporaily non-contacting and non-destructive technique. This technique employs arrayed infrared detectors to capture temperature change on the surface of a stressed material and provides full-field stress information over the surface. According to thermoelastic behavior, when the material is under tensile loaded, the temperature will drop slightly ; on the contrary, when the material is under compressive loaded, the temperature will rise slightly. This mechanical response of the temperature disturbance is the thermoelastic effect of the material. In general, the amount of temperature change caused by the stressed material is very small, only about in the order of . This research uses arrayed infrared detector, to record the small temperature changes on the surface of the loaded material. According to the traditional thermoelastic stress analysis theory, if the material is a elastic body, and satisfy the adiabatic and reversible conditions, the temperature change of the cyclically loaded material will be linearly proportional to the isopachic stress. This linear proportional ratio is the thermoelastic coefficient, which is a constant. In other words, based on the traditional thermoelastic stress analysis relation, after the material is loaded, a slight temperature change is proportional to the sum of principal stresses or isopachic stress.
However, the revised thermoelastic stress analysis theory found that when the material is subjected to a dynamic load, the thermoelastic response generated by the material is related to the mean stress ; moreover, the thermoelastic coefficient has also found to be associated with the mean stress and thereby the thermoelastic coefficient was corrected to the thermoelastic parameter instead of a constant. Based on the mechanics aspect, the mean stress is the static stress, and the residual stress is also present in the structure as the type of static stress, therefore, the residual stress can also be considered as the mean stress. Consequently, the thermoelastic stress analysis technique can be employed to analyze the residual stress existing in the material by applying the modified thermoelastic stress analysis theory. This research will use TSA measurements to investigate the residual-stressed 2024 T351 perforated aluminum plate, and then apply the revised thermoelastic stress analysis theory to determine the residual stress distributed on the aluminum plate.
|
|---|
