Ductile Fracture and S–N Curve Simulation of a 7075-T6 Aluminum Alloy under Static and Constant Low-Cycle Fatigue

Aluminum alloys are attractive for use in structural materials in the aerospace industry, such as for wings and fuselages, due to their high specific strength. The 7075-T6 aluminum alloy is the most competitive alloy in this field because of its good resistance to corrosion and excellent relative density. Ductile damage initiation and evolution in the 7075-T6 aluminum alloy are considered and analyzed under static tension and fully reversed constant amplitude low-cycle fatigue. The damage criteria are implemented with an explicit dynamic finite element model. The static tensile damage data are compared with published experimental results. The S–N curve and surface damage under fatigue are well predicted. Hysteresis loops and strain amplitudes are measured. Moreover, the effects of cycle frequency inputs of 10 Hz and 100 Hz are studied. It is determined that increasing the average input frequency and stress amplitude affects both the fracture surface and the fatigue life. An analysis of the hysteresis loop during loading shows that the material is involved in strain hardening during the first hundred cycles and then softens before failure occurs.