Abstract
Fatigue is one of the most prevalent mechanisms of failure. Thus, the evaluation of the fatigue crack growth process is fundamental in engineering applications subjected to cyclic loads. The fatigue crack growth rate is usually accessed through the da/dN-ΔK curves, which have some well-known limitations. In this study a numerical model that uses the cyclic plastic strain at the crack tip to predict da/dN was coupled with the Gurson–Tvergaard–Needleman (GTN) damage model. The crack propagation process occurs, by node release, when the cumulative plastic strain reaches a critical value. The GTN model is used to account for the material degradation due to the growth of micro-voids process, which affects fatigue crack growth. Predictions with GTN are compared with the ones obtained without this ductile fracture model. Crack closure was studied in order to justify the lower values of da/dN obtained in the model with GTN, when compared with the results without GTN, for lower ΔK values. Finally, the accuracy of both variants of the numerical model is accessed through the comparison with experimental results.
Highlights
The results show that the 25th crack crack closure were studied for two different values of stress intensity factor
Approach is followed, this may be explained by the occurrence of higher plastic zones at approach is followed, this may be explained by the occurrence of higher plastic zones at the the crack tip, which lead to sooner increments of plastic strain in the farthest nodes
Fatigue crack growth is predicted here assuming that cyclic plastic deformation at the crack tip is the fatigue crack growth driving force
Summary
It can affect FCG since metallic materials have intrinThe growth and coalescence of micro-voids is a mechanism usually associated with sic defects which can grow, while new defects can be nucleated Under these conditions, ductile failure of metals. The quantification of the influence of the micro-voids with the stress state and plastic strain [16] It is an internal and cumulativeis performed through an entitydirectly called [17]. The main study is assessing thematerial effect ofdamage accounting for through the GTN plastic strain at objective the crack of tip,this which is affected by the defined model the predicted. [21], using considerations, introduced a yield plastic strain at the crack tip, which is affectedand, by the material damage defined through potential for materials containing micro-voids from the study of a single cavity in a the GTN model.
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