Finite Element and Design of Experiments Study on Stresses in Impact-Damaged Hourglass Specimens Subjected to Rotating Bending

Abstract

Residual stresses and stress concentrations induced by impact-damage may shorten the fatigue life and cause premature failure of aeronautical components. Under cyclic loading, fatigue cracks may initiate at the points where high tensile stresses occur and propagate to failure. In this work, an experimentally validated finite element model was used to assess the stress state in impact-damaged 7075-T6 hourglass specimens subjected to rotating bending. In the first simulation step, the finite element method was used to model residual stresses in the specimens for various impact cases, with different masses of impacting objects and impact speeds and angles. In the subsequent simulation step, the damaged specimens were subjected to rotating bending. The total stresses in the impact region were obtained through the superposition of the residual stresses caused by the impact and the stresses due to the rotating bending load. The design of experiments was applied to the obtained finite element results to identify which impact parameters mostly influence the stress distribution in the damaged specimens. The analysis showed that the most significant parameter is the impact speed, followed by the material and the size of the impacting object while the influence of the impact angle is low.