The effect of stress invariants on ductile fracture limit in steels

Coppola, Tommaso; Cortese, Luca; Folgarait, P.

doi:10.1016/j.engfracmech.2009.02.006

Cited by 97 publications

(57 citation statements)

References 15 publications

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“…These tests consists in the use of specimens with specially designed shapes (axisymmetric or flat) in order to accelerate fracture of the material. The research conducted by many scientists demonstrates that fracture depends not only on grain size, temperature and strain rate [1,[9][10][11], but on the state of stress described by a strain history as well [3,[12][13][14][15]. The main conclusion drawn from the results is that the ductile fracture criterion is well-suited for the modelling of material fracture when the stresses are similar in the test and the investigated process alike.…”

Section: Introductionsupporting

confidence: 49%

Preliminary Analysis of a Rotary Compression Test

Pater¹,

Walczuk²,

Lis³

et al. 2018

Adv. Sci. Technol. Res. J.

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The paper addresses the problem of material fracture in cross rolling processes. A new test based on rotary compression for determining limit values of the damage function after the Cockroft-Latham criterion is proposed. A FEM analysis is performed to determine the stress and strain states in a workpiece subjected to this test. The numerical results demonstrate that the axial region of the workpiece is characterized by the presence of alternating tensile and compressive stresses conducive to fracture. The distribution of the Cockroft-Latham integral in the axial region of the workpiece is determined.

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Section: Introductionsupporting

confidence: 49%

Preliminary Analysis of a Rotary Compression Test

Pater¹,

Walczuk²,

Lis³

et al. 2018

Adv. Sci. Technol. Res. J.

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“…Furthermore, r m ; r Mises and h define the cylindrical Haigh-Weestergaard coordinate system which can represent all stress states. Readers are referred to Bai and Wierzbicki (2010) and Coppola et al (2009) for detailed geometric representations.…”

Section: Characterization Of Stress Statesmentioning

confidence: 99%

“…Bao and Wierzbicki (2004) performed a comparative study on eight models of this class, featuring weighting functions from McClintock (1968), Rice and Tracey (1969), Leroy et al (1981), Clift et al (1990) and the modified Cockcroft and Latham criterion (1968) by Oh et al (1979). They analyzed the applicability of each model and proposed a three-branch weighting function that works over a large range of stress triaxiality g. While classical ductile fracture models use g (or pressure) as the only stress state parameter controlling ductility, recent studies (Zhang et al, 2001;Kim et al, 2004;Coppola et al, 2009) have shown that ductile fracture limit also depends on the deviatoric stress state, represented by the Lode parameter. Xue (2007a,b) introduced the Lode parameter into the weighting function and formed a more general ductile fracture model incorporating the effect of all three stress invariants on damage evolution.…”

Section: Introductionmentioning

confidence: 98%

Numerical failure analysis of a stretch-bending test on dual-phase steel sheets using a phenomenological fracture model

Luo

Wierzbicki

2010

International Journal of Solids and Structures

166

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a b s t r a c tAdvanced High Strength Steels (AHSS) are increasingly used in automotive industry due to their superior strength and substantial weight advantage. However, their compromised ductility gives rise to numerous manufacturing issues. One of them is the so-called 'shear fracture' often observed on tight radii during stamping processes. Since traditional approaches, such as the Forming Limit Diagram (FLD), are unable to predict this type of fractures, great efforts have been made to develop failure criteria that could predict shear fractures. In this paper, a recently developed Modified Mohr-Coulomb (MMC) ductile fracture criterion (Bai and Wierzbicki, 2010) is adopted to analyze the failure behavior of a Dual Phase (DP) steel sheet during stretch-bending operations. The plasticity and ductile fracture of the present sheet are fully characterized by a Hill'48 orthotropic model and a MMC fracture model, respectively. Finite element models with three different element types (3D, shell and plane strain) were built for a Stretch Forming Simulator (SFS) test (Shih and Shi, 2008), numerical simulations with four different R/t values (die radius normalized by sheet thickness) were performed. It has been shown that the 3D and shell element simulations can predict failure location/mode, the upper die load-displacement responses as well as wall stress and wrap angle at the onset of fracture for all R/t values with good accuracy. Furthermore, a series of parametric studies were conducted on the 3D element model, and the effect of tension level (clamping distance), tooling friction, mesh size and fracture locus on failure modes and load-displacement responses were investigated.

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“…In the case of material behaviour obeying the Hollomon rheological law, the upper and lower limits of the fracture locus can be correlated through the Tresca failure hypothesis [7]. The equivalent strain at fracture e f , valid for any value of the stress triaxiality T, can then be expressed by Eq.…”

Section: The Fracture Criterionmentioning

confidence: 99%