3D study of plastic flow localization at a void-sheet. (1st May 2020)

• Record Type: Journal Article
• Authors: Tvergaard, Viggo; Legarth, Brian Nyvang
• Is Part Of: International journal of mechanical sciences. Volume 173(2020)
• Publication Date: 2020-05-01
• Subjects: Shear bands -- Localization -- Large strain -- Viscoplasticity -- Void shape evolution; Mechanical engineering -- Periodicals; Génie mécanique -- Périodiques; Mechanical engineering; Maschinenbau; Mechanik; Zeitschrift; Periodicals; 621.05
• DOI: 10.1016/j.ijmecsci.2020.105426
• Languages: English
• ISSNs: 0020-7403

Abstract

Highlights: Nonlinear 3D finite element computations carried out for void-sheets. Focus on strain at localization including initial and current orientation of void band. Void shape evolution near shear band instability. Various load cases (3D, axisymmetric, plane). Graphical abstract: A single layer of voids in a ductile material is considered using full 3D finite element to study the effect of this material imperfection on the onset of shear band localization, and to study the failure evolution. The layer is inclined relative to the main tensile direction, and the initially spherical voids are taken to be uniformly spaced both along the inclined direction and transverse to it. For each stressstate analyzed a number of initial inclinations, χ 0, of the void layer are considered, and the angle of inclination giving the smallest critical strain, ϵ 2 c, is used as an approximation of the critical band orientation. Different initial void sizes, relative to the void spacing, are considered. Abstract: A single layer of voids in a ductile material is considered to study the effect of this material imperfection on the onset of shear band localization, and to study the failure evolution in the void-sheet mechanism. The layer is inclined relative to the main tensile direction, and the initially spherical voids are taken to be uniformly spaced both along the inclined direction and transverse to it. The material is elastic-viscoplastic with isotropic hardening. When the solid is subjected to a prescribed strain-rate and the shear band width is negligible compared to specimen dimensions, an infinite ratio of the strain-rate in the band relative to the overall prescribed strain-rate defines the onset of localization. For each stress-state analyzed a limited number of initial inclinations of the void layer are considered, with an angular spacing of 5 degrees, and the angle of inclination giving the smallest critical strain is used as a good approximation of the critical band orientation. Different initial void sizes, relative to the void spacing, are considered. It is shown that increased void spacing in the transverse direction significantly delays localization. Also the effects of different levels of strain hardening are compared. The evolution of the void shape during shear localization is studied, to be able to follow the void-sheet failure mechanism. The critical strain for the onset of void coalescence is compared with the critical strain for shear bands.