A framework of modelling slip-controlled crack growth in polycrystals using crystal plasticity and XFEM

P Zhang,R.X Zhou,L.G Zhao,S Lu,T.Y Yu,K.P Baxevanakis

doi:10.1088/1742-6596/1885/4/042014

Abstract

Short cracks tend to develop at high and irregular rates compared to macroscopic cracks, making the prediction of fatigue life a challenging task. In this work, a numerical framework combining crystal plasticity model and the Extended Finite Element Method (XFEM) is applied to study the slip-controlled short crack growth in a polycrystal superalloy RR1000. The model is calibrated from experiments and used to evaluate short crack growth paths and rates. Two fracture criteria are used and compared: the onset of fracture is controlled by the total and individual cumulative shear strain respectively, and the crack grows either perpendicular to the direction of maximum principal strain or along crystallographic directions.

Highlights

IntroductionNumerous experiments have observed that early-stage cracks exhibit a propagation behaviour different from long cracks, having tortuous slip-controlled crack path and fluctuations in crack growth rate, and being highly affected by the local microstructure
Numerous experiments have observed that early-stage cracks exhibit a propagation behaviour different from long cracks, having tortuous slip-controlled crack path and fluctuations in crack growth rate, and being highly affected by the local microstructure.To numerically study short cracks, various techniques have been adopted to simulate the initiation and propagation
We aim to develop a framework that combines the crystal plasticity (CP) and XFEM to model the short crack propagation in polycrystals

Summary

Introduction

Numerous experiments have observed that early-stage cracks exhibit a propagation behaviour different from long cracks, having tortuous slip-controlled crack path and fluctuations in crack growth rate, and being highly affected by the local microstructure. To numerically study short cracks, various techniques have been adopted to simulate the initiation and propagation. The recently proposed Extended Finite Element Method (XFEM) (Moës et al, 1999) introduces enrichment functions into the standard FEM to describe arbitrary discontinuous structures, allows us to model cracks in a mesh-independent way, without predefined paths or remeshing. A number of microscopic fracture criteria have been developed to simulate short crack growth in metals. Crystal plasticity (CP) theory is embedded to introduce crystallographic mechanism, which allows us to capture the behaviour of early-stage cracks.

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Conclusion