Deformation, residual stress, and constitutive relations for quenched W319 aluminum
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20/6/03
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Deformation, Residual Stress, and Constitutive Relations for Quenched W319 Aluminum M.L. NEWMAN, B.J. ROBINSON, H. SEHITOGLU, and J.A. DANTZIG A study of the development of deformation and transient and residual stresses during quenching in aluminum alloy W319 is presented. Rapid tension tests were performed on W319 in the supersaturated solution state at several temperatures and strain rates. A material model following the mechanical threshold stress (MTS)–Voce formulation is developed and implemented in both a simple one-dimensional code and a fully three-dimensional form as a user material subroutine in ABAQUS. The results of the tension tests are used to determine the parameters in the thermomechanical constitutive model. Unidirectional beam quenching experiments are performed to test the applicability of the constitutive model. Residual stresses in the beams are measured using a groove removal technique upon completion of the quenching process. Residual stress and deformation results from beam quenching experiments compare well to the analytical results computed using the constitutive model.
I.
INTRODUCTION
IN recent years, there has been a continuous increase in the use of low-cost aluminum alloys to replace heavier or more expensive metals in automobile engine and suspension components. Cylinder heads, engine blocks, and other cast parts can be made both lighter and less expensive through the use of these alloys. Strength requirements are met by precipitation hardening, which involves a water quench, followed by an aging treatment at an intermediate temperature. The thermal gradients induced by the quench can lead to permanent, measurable part distortion and residual stresses. Tight geometric tolerances for these applications requires that the distortion and residual stress be predicted consistently and accurately. The additional cost of machining a distorted part back into tolerance can easily offset the savings of using a low-cost alloy in the casting. Further, residual stresses can significantly decrease the fatigue life of such parts due to thermomechanical cycling. It is therefore important to predict and control quenching residual stresses. We use a combination of rapid tension tests and beam quenching experiments similar to those of Aksel et al.[1,2] and Becker and co-workers[3,4] to develop a constitutive model for quenched, supersaturated W319. The constitutive model combines a creep model based on the work of Slavik and Sehitoglu[5] at high temperature with a phenomenological unified plasticity model based on the mechanical threshold stress (MTS) model of Follansbee and Kocks[6] for lower temperatures and higher strain rates. M.L. NEWMAN, formerly Graduate Student with the Department of Mechanical and Industrial Engineering, University of Illinois Urbana– Champaign, Urbana, IL 61801, is Engineer/Scientist with the Proctor and Gamble Company, West Chester, OH 45069. B.J. ROBINSON, formerly with the Department of Mechanical and Industrial Engineering, University of Ill
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