Plasticity induced crack closure in Middle-Crack Tension specimen: numerical versus experimental

Numerical studies played a major role in the current understanding of plasticity induced crack closure (PICC), however it is well known that the numerical models simplify the reality by considering discrete crack propagations, relatively high fatigue crack growth rates, sharp cracks and that propagation occurs at a well-defined load. The objective of this paper is to find if despite these limitations, the numerical predictions of PICC are close to the experimental results. Experimental work was developed to obtain crack opening values in 1-mm-thick middle-tension (M(T)) specimens of AA6016-T4 aluminium alloy. The opening level was determined from remote compliance data captured by a pin microgauge placed at the centre of the specimen. A numerical model was developed and optimized replicating the experimental test in terms of sample geometry, loading parameters, material behaviour and crack opening measurement technique. The adoption, in the numerical analysis, of a remote measurement technique for determining PICC was found to be robust and adequate for mesh refinement studies. A good agreement was found between experimental and numerical results.