An investigation of stress concentration, crack nucleation, and fatigue life of thin low porosity metallic auxetic structures

This paper investigates, both experimentally and numerically, the mechanical response of low porosity thin metal samples under fatigue loads. The specimens, characterized by an overall porosity of 10%, were designed using selected patterns of voids and then fatigue tested to estimate the influence of both auxetic and non-auxetic tessellations on the mechanical performance. During the loading, detailed deformation maps were recorded by means of bi-dimensional Digital Image Correlation (DIC). The experimental data collected during this study indicate that the use of auxetic patterns could be a strategy to enhance the fatigue life of porous structures. In addition, DIC analysis is shown to be an excellent non-contact experimental method to assess the cumulative damage of the samples and to predict the crack starting points well before they are detectable by the unaided eye.