MULTIAXIAL FATIGUE BEHAVIOR OF SLM TI6AL4V ALLOY: X-RAY COMPUTED Μ-TOMOGRAPHY ANALYSIS [Keynote]

Crack formation and propagation phenomena in selective laser melting (SLM) Ti-6Al-4V alloy samples were analyzed under combined axial and torsional fatigue loads. In fact, SLM defects lead to a lower fatigue strength and a larger fatigue life variation with respect to to conventionally manufactured parts. Internal defects were captured by X-ray computed μ-tomography (μ-CT) and their evolution was monitored by interrupted fatigue tests. Critical defects were analyzed by the strain intensity factor (SIF) using two differ- ent models based on the Murakami’s method: a modified Smith-Watson and Topper (MSWT) criterion and a virtual strain energy (VSE) criterion. The trend of the crack growth rate was analyzed by the effective defect area at different number of fatigue cycles. The μ-CT data were also used to build finite element models (FEM) of cracked samples to analyze the whole stress-strain distribution in the near crack tip region.
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