Selection of Operating Parameters to Prevent Central Bursting Defects During Cold Extrusion

Zimerman, Z.; Darlington, H.; Kottcamp, E. H.

doi:10.1007/978-1-4615-1757-3_2

Cited by 12 publications

(12 citation statements)

References 3 publications

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“…9, the processing map using instability and fracture conditions predicted occurrence of chevron crack in the experiment properly. In addition, the safe zone was observed mainly for lower reduction in area or relatively small semicone angle as reported in the work by Zimerman et al [7]. However, the safe zone in the processing map was bigger when the critical damage value was increased.…”

Section: Processing Map In the Cold Extrusionmentioning

confidence: 62%

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A study on chevron crack formation and evolution in a cold extrusion

2010

J Mech Sci Technol

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A numerical algorithm based on the element deletion method and rigid-viscoplastic finite element approach depending on CockcroftLatham and specific plastic work fracture criteria was applied to predict formation and evolution of possible cracking in a cold extrusion of aluminum and steel alloys. The Cockcroft-Latham fracture criterion induced an internal crack while an external crack occurred owing to the specific plastic work criterion in simulations. As a result, the Cockcroft-Latham criterion was found to be valid for predicting chevron cracking in comparison with the experimental observation available in the literature. Using the Cockcroft-Latham criterion, cracking was carefully investigated in terms of the size of the crack and gap distance between cracks depending on the number of elements and boundary condition at the punch interface. The critical damage values for the Cockcroft-Latham fracture criterion were also calculated based on the tensile instability and fracture conditions to investigate their effect on possible cracking. Finally, a processing map based on the Cockcroft-Latham fracture criterion for preventing chevron cracking in the cold extrusion of commercially available steel alloy was developed by considering processing parameters such as reduction in area and semicone angle. According to this investigation, the developed element deletion method with the Cockcroft-Latham fracture criterion was reasonably accurate for carrying out chevron cracking analyses in the cold extrusion with proper selection of a critical damage value.

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Section: Processing Map In the Cold Extrusionmentioning

confidence: 62%

“…Zimmerman et al [7] experimentally showed that a safe region consists of small die angle and high reduction in area. Zimmerman and Avitzur [8] suggested a criterion for central bursting according to their analytical work based on the upper bound method.…”

Section: Introductionmentioning

confidence: 98%

A study on chevron crack formation and evolution in a cold extrusion

2010

J Mech Sci Technol

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“…The uncoupled model predicts a reasonably constant effective stress value of about 170 MPa along the surface, lower in magnitude than that at the central axis of the wire. Aravas [40] performed a finite element analysis using Gurson's [31] constitutive model, to analyse multistage extrusion for process parameters, which according to Zimmerman et al [9] would give central burst defects during the second reduction pass. The effective stress in the second pass was found to remain relatively uniform along the central axis of the wire.…”

Section: Effect Of Central Bursts On Effective Stress Distributionmentioning

confidence: 99%

“…Amongst the most basic of these is the well-known shape parameter Δ [5][6][7], which characterises the likelihood of central bursting based on the values of reduction ratio and die angle. Analytical attempts [1,8,9], based on admissible velocity fields, have included the additional influence of friction and strain hardening effects on the likelihood of central bursting formation. Despite giving reasonable predictions, these criteria are quite adventitious, in that they are not concerned with the stress and strain distribution, but only with the energy required.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of axisymmetric wire drawing by means of a coupled damage model

McAllen

Phelan

2007

Journal of Materials Processing Technology

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“…This internal cracks result in a drastic reduction in the service capacity of the product. Investigation of these hidden cracks, to avoid the faulty product transfer to market, requires nondestructive ultrasonic testing on every one of products, Zimerman et al [64], which is neither practical nor cheap. Thus, proper investigation is required on the governing mechanisms of damage accumulation in extrusion.…”

Section: Introductionmentioning

confidence: 99%

Application of Continuum Damage Mechanics in discontinuous crack formation: Forward extrusion chevron predictions

2008

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Key wordsFracture mechanisms (formation of central bursts), damage coupled elasto-plasticity, finite strain, finite elements. MSC (2000) 00-xx Dedicated to Professor Peter Haupt on the occasion of his 70th birthdayMaterializing Continuum Damage Mechanics (CDM), numerical modeling of discrete internal cracks, namely central bursts, in direct forward extrusion process is presented. Accordingly, in a thermodynamically consistent setting, a local Lemaitre variant damage model with quasi-unilateral evolution is coupled with hyperelastic-plasticity. The formulations are constructed in the principal axes where simultaneous local integration schemes are efficiently developed. To this end, the framework is implemented as ABAQUS/VUMAT subroutine to be used in an explicit FE solution scheme, and utilized in direct forward extrusion simulations for bearing steel, 100Cr6. Discontinuous cracks are obtained with the element deletion procedure, where the elements reaching the critical damage value are removed from the mesh. The periodicity of the cracks shows well accordance with the experimental facts. The investigations reveal that, application of the quasiunilateral conditions together with the crack closure parameter has an indispensable effect on the damage accumulation zones by determining their internal or superficial character.

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Selection of Operating Parameters to Prevent Central Bursting Defects During Cold Extrusion

Cited by 12 publications

References 3 publications

A study on chevron crack formation and evolution in a cold extrusion

A study on chevron crack formation and evolution in a cold extrusion

Numerical analysis of axisymmetric wire drawing by means of a coupled damage model

Application of Continuum Damage Mechanics in discontinuous crack formation: Forward extrusion chevron predictions

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