Study on the Influence of the Gurson–Tvergaard–Needleman Damage Model on the Fatigue Crack Growth Rate

Edmundo R Sérgio,Micael F Borges,Diogo M Neto,Fernando V Antunes

doi:10.3390/met11081183

Abstract

The fatigue crack growth (FCG) process is usually accessed through the stress intensity factor range, ΔK, which has some limitations. The cumulative plastic strain at the crack tip has provided results in good agreement with the experimental observations. Also, it allows understanding the crack tip phenomena leading to FCG. Plastic deformation inevitably leads to micro-porosity occurrence and damage accumulation, which can be evaluated with a damage model, such as Gurson–Tvergaard–Needleman (GTN). This study aims to access the influence of the GTN parameters, related to growth and nucleation of micro-voids, on the predicted crack growth rate. The results show the connection between the porosity values and the crack closure level. Although the effect of the porosity on the plastic strain, the predicted effect of the initial porosity on the predicted crack growth rate is small. The sensitivity analysis identified the nucleation amplitude and Tvergaard’s loss of strength parameter as the main factors, whose variation leads to larger changes in the crack growth rate.

Highlights

This study aims to evaluate the influence of the Gurson– Tvergaard–Needleman (GTN) parameters on the crack growth rate predicted by a node release numerical model
The propagation is simulated by node release, which occurs when the accumulated plastic strain reaches a critical value
GTN damage model was adopted to account for the loss of strength, due to the accumulation of damage, which accompanies the occurrence of plastic strain

Summary

Introduction

The fatigue crack growth (FCG) process is widely evaluated using the stress intensity factor range (∆K) [1,2]. This concept is interesting because it is related to the stress and strain fields occurring near the crack tip. The introduction of the crack closure concept allowed to explain the results obtained when considering overloads [4], short cracks [5], and mean stress [6]. The crack closure is related to non-linear concepts [7] while ∆K is fundamentally elastic [8]

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Results

Conclusion