Influence of Prior Heat and Creep on Fatigue in Structural Elements of DTD 5014 (RR58) Aluminium Alloy
Abstract:
Effects of heat on fatigue have been studied by fatigue tests at ambient temperature on specimens first subjected to a single period of heating with and without steady load applied. The tests employed constant amplitude loading on various structural elements in DTD 5014 RR58 aluminium alloy material. Heating was applied at temperatures in the range 100 deg C to 170 deg C for times ranging from 1h to 20000h. The initiation of fatigue cracks was significantly affected by heating, particularly at temperatures of 110 deg C and higher when the effects occurred comparatively rapidly. The two mechanisms of importance were changes in microstructure at the machined surface which encouraged initiation, and changes in residual stress by creep which encouraged or discouraged initiation according to the creep being compressive or tensile.