Model Describing Material-Dependent Deformation Behavior in High-Velocity Metal Forming Processes

International Journal of Mechanical Sciences

2013

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The microstructure evolution during cold rolling of commercial purity AA1050 aluminum is investigated through numerical simulations. A finite strain elasto-viscoplastic constitutive model is employed, where the dislocation density and average grain size are taken as variables characterizing the deformed microstructure. Grain size evolution due to dynamic recrystallization is considered and the microstructure quantities are allowed to influence the macroscopic material behavior in terms of the flow stress and deformation-rate dependence. The effects of such process parameters as rolling friction, thickness reduction in each rolling pass and amount of rolling asymmetry are discussed. The results indicate that grain refinement due to dynamic recrystallization is most significantly affected by the amount of thickness reduction in each pass and the level of rolling friction and to a lesser extent by the asymmetry of the rolling process. An increasing degree of asymmetry will, however, reduce the variations in grain size through the sheet thickness and leave the material more homogeneously recrystallized.

“…Numerical implementation of constitutive models, using the above approach, is also discussed in [8,50].…”

Section: Numerical Implementationmentioning

confidence: 99%

Influence of process parameters on grain refinement in AA1050 aluminum during cold rolling

International Journal of Mechanical Sciences

2013

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“…A 100Cr6 steel was studied in two differently heat-treated conditions: as-received spheroidize-annealed material (SA) having a microstructure of ferrite, containing spheroidized carbides and also a material that was quenched and tempered (QT) at 610 • C for 120 minutes resulting in a martensitic microstructure with a hardness of 170 HV, cf. [12]. Tensile specimens, cf.…”

Section: Resultsmentioning

confidence: 99%

“…Thermoelastic effects in connection with measurements of the subsequent stored energy of cold work are discussed in relation to experiments in [8][9][10][11][12][13]. Similar studies were performed in [14,15] which focussed on the temperature evolution in front of a propagating crack.…”

Section: Introductionmentioning

confidence: 89%

A Note on the Kelvin Effect in 100Cr6 Steel with Application to Identification of the Elastoplastic Limit

2012

ISRN Thermodynamics

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Experimental and analytical results are presented regarding the temperature evolution in 100Cr6 steel under uniaxial loading. Differently heat-treated conditions of the material are studied at different strain rates. In the annealed state, the materials exhibits a pronounced initial yield stress as it passes from the elastic region to the plastic through discontinuous yielding. In contrast, the quenched and tempered material yields continuously. The focus of the paper is on the temperature decrease during elastic deformation that precedes the more pronounced heating due to inelastic dissipation once the elastoplastic limit stress is surpassed. The applicability of the maximum temperature decrease in the elastic regime as a replacement for the commonly used 0.2%-strain measure to define the elastoplastic limit is discussed. For 100Cr6 steel, the 0.2%-strain measure is found, in some cases, to overestimate the initial yield stress by 50 MPa. The drop in temperature corresponding to the shift from elastic to inelastic material behavior is experimentally determined and compared to predictions by the Kelvin formula which in the current study give a maximum 50% error.

“…Note that beside the evolution equations for the dislocation density and the grain size, only one additional scalar equation related to the effective viscoplastic strain enters the local stress-updating algorithm, rendering a numerically efficient implementation of the model. These aspects are discussed in [57].…”

Section: Simulation Resultsmentioning

confidence: 99%

Modeling of continuous dynamic recrystallization in commercial-purity aluminum

Materials Science and Engineering: A

Wallin

Ristinmaa

2010

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a b s t r a c tA constitutive model for polycrystalline metals is established within a micromechanical framework. The inelastic deformation is defined by the formation and annihilation of dislocations together with grain refinement due to continuous dynamic recrystallization. The recrystallization studied here occurs due to plastic deformation without the aid of elevated temperatures. The grain refinement also influences the evolution of the dislocation density since the recrystallization introduces a dynamic recovery as well as additional grain and subgrain boundaries, hindering the movement of dislocations through the material microstructure. In addition, motivated by experimental evidence, the rate dependence of the material is allowed to depend on the grain size. Introducing a varying grain size into the evolution of the dislocation density and in the rate dependence of the plastic deformation are believed to be important and novel features of the present model. The proposed constitutive model is implemented in a numerical scheme allowing calibration against experimental results, which is shown using commercial-purity aluminum as example material. The model is also employed in macroscale simulations of grain refinement in this material during extensive inelastic deformation.