An investigation on the crack growth in aluminum alloy 7075-T6 under cyclic mechanical and thermal loads

This study evaluates the consequences of mechanical load frequencies and thermal fluctuations on the fatigue crack growth in CT samples made by AA7075-T6. A controllable electrical resistance heating furnace/cooling fan setup was built for applying constant and variable thermal loads. In the first step, fatigue crack growth behavior was studied under different constant temperatures and a maximum load as 12 kN with R = 0. This evaluation indicated that the fatigue lives of the samples were reduced by increasing the constant temperature. Numerical simulations were performed by using the concept of the contour integral in evaluation of the stress intensity factors (SIFs) and crack growth based on Walker's Equation. Applying cyclic temperatures on the samples and altering the mechanical load frequencies revealed that reducing the load frequency from 30 to 10 Hz hasn't considerable effects on the fatigue crack propagation behavior. On the other hand, lowering the frequency to 5 Hz resulted in a minor decrease in the fatigue lives, while more reduction to 0.5 or 0.1 Hz, severely reduced the failure cycles.

Automated summary

This study evaluates the effects of mechanical load frequencies and thermal fluctuations on the fatigue crack growth in CT samples made by AA7075-T6. The results showed that increasing the constant temperature reduces the fatigue lives of the samples. Numerical simulations indicated that reducing the load frequency has little impact on the fatigue crack propagation behavior, while further reduction severely decreases the failure cycles.