Metal Flow Through Conical Converging Dies—A Lower Upper Bound Approach Using Generalized Boundaries of the Plastic Zone

Zimerman, Z.; Avitzur, B.

doi:10.1115/1.3427695

Cited by 35 publications

(13 citation statements)

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“…The maximum value of hydrostatic stress is reduced on the centerline as friction is increased, resulting in a more homogeneous deformation across the billet. This is consistent with the computational findings of Oh et al (1979) and Lim and Dunne (1997), the experimental findings of Liu and Chung (1990) and the analytical treatment by Zimerman and Avitzur (1970). Fig.…”

Section: Friction-defect Relationshipsupporting

confidence: 94%

“…It is known that central bursting is more likely to occur in materials which undergo work hardening (Zimerman and Avitzur, 1970). In a non-work hardening metal, the material near the surface undergoes high plastic strain, while the material near the center is more ÔrigidÕ and is forced ahead, creating an inhomogeneous deformation field across the die.…”

Section: Strain Hardening Effect On Damagementioning

confidence: 99%

“…If the driving force for the cracked sample is less than for the uncracked sample, central bursting will occur. This approach was extended by Zimerman and Avitzur (1970) to account for strain hardening; however it does not address the underlying micromechanics of the central bursting failure phenomena.…”

Section: Introductionmentioning

confidence: 99%

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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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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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Section: Friction-defect Relationshipsupporting

confidence: 94%

Section: Strain Hardening Effect On Damagementioning

confidence: 99%

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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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“…His work showed that distortion increases with increasing reduction and die angle. Zimerman and Avitzur [7] and Pan et al [8] proposed upper bound models with flexibility in the velocity field to allow the distorted grid to change with friction. As expected, these models confirmed that distortion increases with increasing friction.…”

Section: Previous Studies On Distortion Of Axisymmetric Extrusionsmentioning

confidence: 99%

Minimizing distortion during extrusion using adaptable dies

Gordon¹,

Tyne²,

Moon³

2012

International Journal of Mechanical Sciences

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“…Chen and Ling [4] hyperbolic dies. Zimmerman and Avitzur [5] also modeled extrusion using the upper bound method with generalized shear boundaries. Mehta et al developed a kinematically admissible velocity field and compared it with the experimentally obtained flow field using the visioplasticity technique [6].…”

Section: Introductionmentioning

confidence: 99%

An Upper Bound Solution of Backward Tube Extrusion Process Through Curved Punches

Haghighat¹,

Asgari²

2014

Acta Metall Slovaca

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In this paper, an upper bound approach is used to analyze the process of backward tube extrusion through arbitrarily curved punches. Based on the assumptions of proportional angles and proportional distances from the mandrel surface in the deformation zone, two kinematically admissible velocity fields are proposed and those are used in upper bound solution. By using the developed upper bound solution, optimum punch lengths which minimize the extrusion forces are determined for a streamlined punch shape and also for a conical punch. The corresponding results are also determined by using a finite element code, ABAQUS, and by doing some experiments and compared with the analytical results. This comparisons show a good agreement. Keywords: Backward tube extrusion, Upper bound, Experiment IntroductionIn backward extrusion, there is no relative movement between the initial billet and the container and it is characterized by the absence of friction between the initial billet surface and the container. This process needs lower extrusion force and also it is suitable for producing partially extruded products because of the simplicity in ejecting of the extruded part from the container as compared with forward extrusion process. In this process, such as other metal forming processes, calculation and optimization of extrusion force are important. Among various analytical and numerical approximate methods of solution, the upper bound technique and the finite element method have been widely used for the analysis of the extrusion process. One of the limitations of most of the current FEM solution schemes for metal forming is that they do not provide parametric analysis. Hence, any parametric investigation is usually done manually by changing one FE model to another until a feasible solution is obtained. Establishment of analytical solutions for extrusion process facilitates parametric study and may help in understanding the mechanics behind the extrusion processes better. Even though the finite element gives detailed information, it takes considerable CPU time. Using the upper-bound technique has the merits of saving computer's CPU and it appears to be a useful tool for analyzing metal forming problems when the objective of such an analysis is limited to prediction of deformation load and/or to study metal flow during the process. A number of people have used the upper bound method to analyze the extrusion process. Avitzur [1-3] developed models for forward rod extrusion through conical dies using the upper bound approach. Chen and Ling [4] developed a velocity field for axisymmetric extrusions through cosine, elliptic and

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Metal Flow Through Conical Converging Dies—A Lower Upper Bound Approach Using Generalized Boundaries of the Plastic Zone

Cited by 35 publications

References 0 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

Minimizing distortion during extrusion using adaptable dies

An Upper Bound Solution of Backward Tube Extrusion Process Through Curved Punches

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