A model for ductile fracture based on internal necking of spheroidal voids

Ragab, Ahmed

doi:10.1016/j.actamat.2004.05.015

Cited by 36 publications

(22 citation statements)

References 42 publications

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“…The void coalescence mechanism in the PLL is due to necking failure of the intervoid ligament, which occurs transverse to the principal loading direction. Several extensions of Thomason's PLL model have been proposed (Pardoen and Hutchinson 2000 ;Zhang et al 2000;Benzerga 2002;Ragab 2004a). Assuming no variation in the flow stress of the matrix material within the unit cell, coalescence in Ragab (2004a) modified PLL model occurs when the following condition is satisfied…”

Section: Void Coalescence Due To Internal Neckingmentioning

confidence: 99%

“…5a are valid for a relatively large range of triaxiality from 1 3 ≤ σ hyd σ ≤ 2 Ragab (2004b). Assuming the matrix material of the unit cell is incompressible, the evolution equation of Ragab (2004a) for the unit cell aspect ratio, λ 2 = L y L x , as shown in Fig. 2, can be expressed in rate form aṡ…”

Section: Evolution Of Void Shape and Unit Cellmentioning

confidence: 99%

“…Since the dominant nucleation mechanism and fraction of void nucleating particles are unknown, we assume that every martensite particle is a candidate for nucleation, f n = 5.5%, and the nucleated void is initially spherical, λ 1 o = 1. The remaining parameter to be predetermined is the initial aspect ratio of the unit cell which we assume to be cubic, λ 2 o = 1, as in Ragab (2004a). Now that all of the microstructure-based parameters have been predetermined, the nucleation stress and strain are determined parametrically by comparing the numerical and experimental formability data.…”

Section: Selection Of Damage-based Materials Parametersmentioning

confidence: 99%

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Damage-based finite-element modeling of tube hydroforming

et al. 2009

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Numerical simulations of straight tube hydroforming of a dual phase (DP600) advanced high strength steel were performed using a variant of the Gurson-Tvergaard-Needleman (GTN) constitutive model to account for the influence of void shape and shear on coalescence. The effect of axial-feed (end-feed) on damage development and formability is investigated for end-feed loads of zero and 133 kN. A parametric study was conducted to determine an appropriate void nucleation stress and strain and the numerical values compared with the experimental data. The calibrated GTN damage model gives good agreement with the experimentally determined burst pressure, formability and failure location with the best performance occurring for the high end-feed load.

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Section: Void Coalescence Due To Internal Neckingmentioning

confidence: 99%

Section: Evolution Of Void Shape and Unit Cellmentioning

confidence: 99%

Section: Selection Of Damage-based Materials Parametersmentioning

confidence: 99%

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Damage-based finite-element modeling of tube hydroforming

et al. 2009

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“…Another failure condition based on internal necking of the matrix material ligament between two adjacent voids is suggested by Ragab [25] as…”

Section: Stresses and Strains In Bulk Formingmentioning

confidence: 99%

“…The current aspect ratio 1 estimated from a semiempirical relation for void shape evolution within the range 1/6 Յ 1i Յ 6 is suggested by Ragab [25] as for initially prolate void: 1i Ն 1 and for initially oblate void: 1i Յ 1…”

Section: Stresses and Strains In Bulk Formingmentioning

confidence: 99%

An approach to predict free surface fracture in bulk forming

Ragab

2006

Metall Mater Trans A

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This work presents a unified approach to predict surface strains at failure in bulk forming processes. The approach does not deal with a specific process but rather with prescribed strain and stress paths. The material to be processed is assumed to possess an initial void volume fraction that grows and coalesces with straining, ending by fracture. The predictions are based on a formulation for voided solids according to the Gurson-Tvergaard yield function adapted to include orthotropic anisotropy. The incident of fracture is characterized by shear band formation within the ligaments of the matrix material among spheroidal voids as described by McClintock. The results are represented by a straight line plot of tensile limit strain versus the compressive strain for different loading paths. These limit curves are shown to be dependent on the initial void fraction, hardening, and anisotropy of the matrix material. Alloys with lower initial void fractions as well as those of higher hardening show better workability. The model is applied to predict bulk formability curves for steels AISI 1040 and 1045, Aluminum Al 7075-T6, and copper, based on the proper selection of micromechanical parameters for these alloys. The validity of the model is ensured through fairly favorable comparison with experimentally determined limit curves. The current failure conditions are suitable to predict the experimental dual slope fracture line that may exist for some alloys such as cold-drawn steel AISI 1045 and aluminum 2024-T6 by considering two mechanisms of failure: internal necking in the ligament material between voids, followed by transition to shear band formation.

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Numerical Prediction of Ductile Fracture in Bi-Axially Stretched Sheet Metal

AbdelKader

Saleh

2020

The Minerals, Metals &Amp; Materials Series

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A model for ductile fracture based on internal necking of spheroidal voids

Cited by 36 publications

References 42 publications

Damage-based finite-element modeling of tube hydroforming

Damage-based finite-element modeling of tube hydroforming

An approach to predict free surface fracture in bulk forming

Numerical Prediction of Ductile Fracture in Bi-Axially Stretched Sheet Metal

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