Application of Design of Experiments to Foreign Object Damage on 7075-T6

In this work, Design of Experiments is applied to identify which factors mostly influence the residual stress distribution in an hourglass specimen subject to the impact of a foreign object. The specimen is made of 7075-T6, that is one of the most popular alloys in the aeronautical sector. After the impact, the specimen is assumed to be tested with an axial or bending fatigue load. For this reason, the study is conducted on the axial stresses induced by the impact of the object on the specimen, assessed by means of finite element analysis. Only the stresses in the region x=[-2 mm; 2 mm], with x=0 corresponding to the position of the minimum cross section of the specimen before the impact, were considered. In this region, stress concentrations are probable during the fatigue test. The results showed that high impact forces induce high tensile stresses, unfavorable from a fatigue point of view. Therefore, it is preferable that the impacting object has a low weight and reduced speed.