Fatigue life prediction in frequency domain using thermal-acoustic loading test results of titanium specimen

Abstract

High supersonic vehicles are exposed to high temperature generated by aerodynamic heating. Thermal protection system structures are used on the skin of the fuselage and wings to prevent the transfer of high temperatures into the interior of the vehicle. Thin skin panels can be exposed to acoustic loads by high power engine noise and jet flow noise, which can cause sonic fatigue damage. Therefore, it is necessary to examine the behavior of supersonic/hypersonic vehicle skin structures under thermal-acoustic loads and to predict fatigue life. In this paper, thermal-acoustic testing of titanium specimens under thermal-acoustic load was performed. The response stress history of the specimen was obtained, and the fatigue life was predicted using the time and frequency domain fatigue life prediction method. The effect of the mean stress on the predicted results of the time and frequency domian fatigue life was analyzed. Stress history was generated using a sine series of random phases from stress PSD without phase information. The fatigue life in the generated stress history was predicted using the time and frequency domain fatigue life prediction methods. As the temperature increased, the mean stress of the response stress and the error in the frequency domain fatigue life prediction results increased. The error in the frequency domain fatigue life prediction results with the mean stress effect were greatly reduced by considering the completely reversed stress.