Experimental and Computational Approach to Fatigue Behavior of Polycrystalline Tantalum

Abstract

This work provides an experimental and computational analysis of low cycle fatigue of a tantalum polycrystalline aggregate. The experimental results include strain field and lattice rotation field measurements at the free surface of a tension–compression test sample after 100, 1000, 2000, and 3000 cycles at ±0.2% overall strain. They reveal the development of strong heterogeneites of strain, plastic slip activity, and surface roughness during cycling. Intergranular and transgranular cracks are observed after 5000 cycles. The Crystal Plasticity Finite Element simulation recording more than 1000 cycles confirms the large strain dispersion at the free surface and shows evidence of strong local ratcheting phenomena occurring in particular at some grain boundaries. The amount of ratcheting plastic strain at each cycle is used as the main ingredient of a new local fatigue crack initiation criterion.

Trends in Plasticity of Metals and Alloys

“…Two works concern new approaches to the problem of fatigue behavior of materials [3,4]. In [3], the combination of the digital image correlation and electron backscatter diffraction techniques allows revealing the strong heterogeneities of strain and lattice rotation at the free surface of a tantalum polycrystalline aggregate during low cycle fatigue. The crystal plasticity finite element simulation confirms the strongly heterogeneous local ratcheting.…”