Effect of surface integrity induced by machining on high cycle fatigue life of 7075-T6 aluminum alloy

The metallurgical, mechanical and topographical modifications induced by machining strongly influence the surface quality of the final components which, in turn, dictates the functional performance and service-life of engineered products. This paper aims to extensively discuss the effect of machining parameters and cooling/lubrication strategies on the high cycle fatigue strength of 7075-T6 aluminum alloy. More in detail, three different cutting speeds (90, 120 and 150 m/min) and four cooling/lubrication methodologies (dry, cryogenic, minimum quantity lubrication and high pressure air jet) have been analyzed. The obtained fatigue samples have been tested under fully reversed stress conditions in the high cycle fatigue regime. An adapted analytical model, taking into account the effect of the surface changes, is also proposed in order to drastically reduce the number of destructive tests needed assessing the effects of the processing parameters on the overall fatigue endurance.