The prediction of central burst defects in extrusion and wire drawing

A simple cell model based damage dependent yield surface is used to model the effect of void nucleation and growth in an aluminum alloy during an axisymmetric cold extrusion process. Material parameters for characterization of the yield surface are determined through a physically consistent micromechanical cell modeling technique. The model can account for the behavior of a void containing a particle under severe compressive processing conditions. The formation of distinct, equally spaced, arrowhead shaped Ôcentral burstÕ defects is observed during simulation of the extrusion process. Application of the model to a two-stage rolling process is also briefly illustrated. Formation of central bursts during extrusion and edge cracking during rolling is explained in terms of the hydrostatic stress distribution and the related void growth. The affects of material hardening, surface friction and die geometry are examined in the case of extrusion. Correlation is found between the simulations and analytical and experimental results, confirming the suitability of the constitutive model.

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“…12a). (Ko and Kim, 2000). free surfaces (the crack faces), which leads to a stress relief zone around the cracks.…”

Section: Billet Materials Constitutive Behaviormentioning

confidence: 99%

“…Attempts have also been made to use a Cockroft and Latham (1968) type energy criterion, notably by Ko and Kim (2000) and Liu and Chung (1990). As with most energy criteria no direct coupling between the damage criteria and the subsequent deformation is included in the model i.e.…”

Section: Introductionmentioning

confidence: 99%

Prediction of central bursting during axisymmetric cold extrusion of a metal alloy containing particles

McVeigh

Liu

2006

International Journal of Solids and Structures

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“…Finite element modelling of fracture propagation by removing elements (i.e. giving zero stiffness) is commonly known as the element failure technique (Hambli and BadieLevet 2000;Saanouni et al 2004;Ko and Kim 2000). A numerical algorithm based on Cockcroft-Latham criterion (Choi et al 2010) and Gurson-TvergaardNeedleman damage model (Tang et al 2011) was applied to study the damage evolution in the cold extrusion and the multi-pass wire drawing process respectively.…”

Section: Introductionmentioning

confidence: 99%

The influence of the drawing parameters and temperature rise on the prediction of chevron crack formation in wire drawing

2012

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The objective of the present work is to predict the formation of chevron crack in copper wire drawing process. The first part of this paper is to determine the chevron crack formation initiated by a central burst inside the wire material using experimental tests. These results are compared with results from a series of numerical simulations using the CockcroftLatham fracture criterion. The second part of this work concerns the determination of a curve that divides the chevron and safe zones for a better wire drawing process. The conditions of central burst defects formation along the wire axis depend on drawing parameters and friction coefficient between the die and the wire. The friction coefficient is defined as a linear function of temperature rise which is measured close to the wiredie interface. The obtained results show that the friction A. Haddi (B) Laboratoire Génie Civil et géo-Environnement (LGCgE), coefficient depending on temperature rise during wire drawing has an impact on the damage of copper wire.

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“…In addition, due to the complexity of the equations involved, the applications of such criteria are only suitable for simple geometries and boundary conditions. The availability of finite element computer programs has resulted in the implementation of fracture criteria to metal forming analysis by numerous researchers (Clift et al, 1989;Chevalier, 1992;Chaouadi et al, 1994;Gouveia et al, 1996;Campos and Cetlin, 1998;Choi et al, 1998;Phelan et al, 1999;Ko and Kim, 2000;McAllen and Phelan, 2005). This approach has resulted in some success.…”

Section: Introductionmentioning

confidence: 99%

“…Komori (1999Komori ( , 2003 and Ko and Kim (2000) have investigated the occurrence of central burst defects in drawing and extrusion respectively, utilizing rigid plastic material laws. Significant differences in the deformation zone stresses and distribution pattern have been reported where the FE analysis has been approximated using a rigid-plastic material law (Pilarczyk et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

Ductile Fracture by Central Bursts in Drawn 2011 Aluminium Wire

McAllen

Phelan

2005

Int J Fract

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This paper reports on the application of numerical techniques to predict the initiation and propagation of central burst defects in the wire drawing process. The development and implementation of a suitable failure model into a commercial finite element code, via a user written subroutine, has enabled the occurrence of ductile fracture by central bursting in 2011 Aluminium alloy wire to be successfully analysed. In validating the numerical model, the drawing force, die pressure and occurrence of central burst defects has been compared with previously published experimental data. Results from the numerical model suggest that a 'nose shape' curve divides the safe and unsafe zones for the successful drawing of the wire. It follows that no central bursts are expected to occur, regardless of the die angle used, when the reduction ratio is less than a critical value. When central bursts did occur, the effective strain was found to vary periodically along the surface of the wire. These oscillations corresponded with the occurrence of central burst defects and resulted in variations in the final diameter of the wire. These variations in the final diameter of the wire are thought to be representative of an external defect known as 'bamboo markings', which are often an external indication of central burst defects within the wire.

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The prediction of central burst defects in extrusion and wire drawing

Cited by 61 publications

References 9 publications

Prediction of central bursting during axisymmetric cold extrusion of a metal alloy containing particles

Prediction of central bursting during axisymmetric cold extrusion of a metal alloy containing particles

The influence of the drawing parameters and temperature rise on the prediction of chevron crack formation in wire drawing

Ductile Fracture by Central Bursts in Drawn 2011 Aluminium Wire

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