Void growth and morphology evolution during ductile failure in an FCC single crystal
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O R I G I NA L A RT I C L E
Madhu Kiran Karanam · Viswanath R. Chinthapenta
Void growth and morphology evolution during ductile failure in an FCC single crystal
Received: 29 February 2020 / Accepted: 24 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Void growth and morphology evolution are studied using a 3D representative volume element with a spherical void embedded in an FCC single crystal. The plastic flow contours are studied to determine the scenarios leading to fully plastic flow and plastic flow with elastic region. Further, the effect of anisotropy on void growth is studied through three initial crystallographic orientations (ICOs) [100], [110], & [111] with respect to loading direction. Void growth and macroscopic stress variations with applied strain are obtained from our simulations. It is observed that the peak stress corresponds to rapid void growth initiation. The peak stress is found to be dependent on void volume fraction and ICO. Furthermore, an additional geometrical parameter, diagonal distortions (Ddi ) is introduced to classify the non-spheroidal void shapes observed in deformed anisotropic crystal. Keywords Void growth · Void morphology · Ductile failure · Crystal plasticity
1 Introduction Micromechanical analysis of the ductile failure process is on an increasing trend due to its ability to model the behavior of modern material with complex microstructures effectively. The ductile failure process typically starts with nucleation of voids by fracture and de-cohesion of the second phase particles. The nucleated voids then grow and coalesce to form micro-cracks, which eventually lead to failure of the material. The ductile failure process depends primarily on the geometry of the void (i.e., void shape, void size, distribution of voids), material anisotropy, work hardening, and the stress state around it. Several studies have already been performed to understand this process, both theoretically and experimentally [1–6]. Through the experimental and theoretical studies, the process of void growth is relatively well understood using phenomenological methods. However, the evolution of the morphology of the voids, which is an essential factor in determining the initiation of coalescence and, in turn, the ductile failure, is sparingly studied. A brief of the work in this field is presented here. The initial theoretical model for void growth was proposed by Rice and Tracey [7], who studied the void growth in the infinite rigid-plastic medium. They observed that under tensile loading with mean stress superposed over it, the volume-changing part of void growth dominates the shape-changing part at higher values of remote stress. However, at lower and moderate values of remote stress, these contributions are equally important. Following that Gurson [1] developed yield function using unit cell model with an isolated cylindrical and spherical void in a rigid-plastic cell for two types of flow field, one with fully plastic flow Communicated by Andreas Öchsner. M. K. Ka
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