Effect of temperature on the growth of fatigue surface cracks in aluminum alloys

To understand the effect of temperature on the rate of fatigue crack growth in D16T and B95AT aluminum alloys, fatigue crack growth experiments using a constant load amplitude were carried out on hollow cylindrical specimens with induced external semi-elliptical surface cracks. The rates of fatigue crack growth in the specimens were determined as a function of temperature, ranging from low (-60 degrees C) to elevated (+250 degrees C), and were analyzed as a function of the elastic and plastic stress intensity factors (SIF). The process of numerical calculations includes the analysis of the elastic constraint parameters in the form of the non-singular T-stress and Tz factor, as well as the elastic-plastic constraint parameters in the form of the local stress triaxiality h and In factors for the various tested materials at the different tested temperatures. The interpretation of the fatigue crack growth data in terms of the plastic SIFs results in a single general curve with a small scatter band over a wide range of temperatures.