Modeling strain-path changes in aluminum and steel

Qin, Jisheng; Holmedal, Bjørn; Zhang, Kai; Hopperstad, Odd Sture

doi:10.1016/j.ijsolstr.2017.03.032

Cited by 33 publications

(21 citation statements)

References 25 publications

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“…In addition to dislocation hardening, the texture evolution induced by the activation of From VPSC results, the plastic deformation during tension was dominated by the slip dislocation. The distribution of dislocation was heterogeneous at grain level which related to the prestrain direction [10,32,33]. Dislocation hardening during reloading is induced by dislocation pile-up produced by prestrain.…”

Section: Resultsmentioning

confidence: 99%

Mechanical Anisotropy Induced by Strain Path Change for AZ31 Mg Alloy Sheet

Yang

Mei

Meng

et al. 2020

Metals

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The variation of strain paths induces anisotropy during practical sheet forming processes, which is very important for the subsequent processing technology of anisotropic Mg alloys. In this study, two-step loading tests (tension-tension) were performed to clarify the effect of strain path changes on the evolution of anisotropy on rolled AZ31 sheet. Specimens were preloaded with tension along the rolling direction (RD) with 9% of prestrain. Then, second tension was conducted along 0°, 30°, 45°, 60° and 90° from the RD. It was found that yield strength during the second loading increased along the same direction compared to uniaxial tension without prestraining. For the second loading, the yield strength and flow stress decreased with the increase of the angle from the RD. It was found that the strain path change resulted in stronger anisotropy than that induced by texture. Moreover, it was found that the main deformation modes were basal and prismatic slips during the second loading based on visco-plastic self-consistent (VPSC) modeling. The relative activities of basal and prismatic slips were affected by the second loading direction due to texture evolution. The mechanical anisotropy induced by strain path changes was ascribed to the coupling of the heterogeneous distribution of dislocations and texture evolution induced by prestraining.

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Section: Resultsmentioning

confidence: 99%

Mechanical Anisotropy Induced by Strain Path Change for AZ31 Mg Alloy Sheet

Yang

Mei

Meng

et al. 2020

Metals

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“…In the continuum-plasticity theory, Bauschinger effects are Deformation twinning by pseudo slip systems or the stress-differential effect are examples of mechanisms that distort the yield surface. In the continuum-plasticity theory, Bauschinger effects are commonly handled by a back stress, even in complex models accounting for strain-path changes [37], but recently, significant progress has been reported on continuum models involving yield-surface distortions [21][22][23][24][25][26]. Similarly, crystal-plasticity models with latent hardening predict a shape change of the crystal yield surface during deformation [17,18,20].…”

Section: Discussionmentioning

confidence: 99%

“…At room temperature, one may apply ξ s ≡ 1, as the exponent n will be larger than 50, i.e., the instant strain-rate sensitivity for most metals at room temperature is m > 0.02. The advanced continuum-plasticity models [21][22][23][24][25][26] can be calibrated based on virtual experiments, performed using models for distortions of the yield surface by virtual experiments calculated by physical-based crystal-plasticity models [17,18,20], which may complement rather demanding mechanical experiments.…”

Section: Discussionmentioning

confidence: 99%

“…This allows yield-surface distortions as predicted by models dealing with strain-path changes related to Bauschinger and cross-hardening effects, e.g., [17][18][19][20]. Recently progress on similar distortional-hardening approaches in continuum plasticity models has been reported in [21][22][23][24][25][26]. The same framework can be applied to pseudo-slip systems applied in deformation-twinning models [27].…”

Section: Introductionmentioning

confidence: 98%

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Regularized Yield Surfaces for Crystal Plasticity of Metals

Holmedal

2020

Crystals

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The rate-independent Schmid assumption for a metal crystal results in a yield surface that is faceted with sharp corners. Regularized yield surfaces round off the corners and can be convenient in computational implementations. To assess the error by doing so, the coefficients of regularized yield surfaces are calibrated to exactly interpolate certain points on the facets of the perfect Schmid yield surface, while the different stress predictions in the corners are taken as the error estimate. Calibrations are discussed for slip systems commonly activated for bcc and fcc metals. It is found that the quality of calibrations of the ideal rate-independent behavior requires very large yield-surface exponents. However, the rounding of the corners of the yield surface can be regarded as an improved approximation accounting for the instant, thermal strain-rate sensitivity, which is directly related to the yield-surface exponent. Distortion of the crystal yield surface during latent hardening is also discussed, including Bauschinger behavior or pseudo slip systems for twinning, for which the forward and backward of the slip system are distinguished.

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“…Regarding the mechanical characterization of sheet metal following complex deformation paths, the tests with strainpath change have a great importance because they highlight the kinematic hardening, linked to the Bauschinger effect and to the phenomena of stagnation of work hardening [10]- [12]. Taking these phenomena into account in the model leads to a better prediction of certain defects observed in the forming of the sheet metal [13]- [15].…”

Section: Introductionmentioning

confidence: 99%

Strain-path dependent hardening models with rigorously identical predictions under monotonic loading

Yang

Vincze

Baudouin

et al. 2021

Mechanics Research Communications

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Accurate sheet metal simulation often requires advanced strain-path dependent material models, in order to predict the material response under complex loading conditions, including monotonic, reverse and orthogonal paths. More and more flexible models imply higher and higher costs in terms of parameter identification, computer implementation and simulation time, and robust comparison is often compromised by the inconsistent predictions of advanced models under monotonic loading. In this paper, a simple and general approach is proposed for the alteration of advanced hardening models in order to make them rigorously identical to each other under monotonic loading. This objective was reached without any drawback other than the addition of the corresponding equations. On the contrary, the flexibility and accuracy of the selected models was improved, and the parameter identification procedure became simpler, more accurate and more robust. Three material models of increasing complexity were selected to demonstrate the interest of this approach with respect to a complete set of characterisation experiments for a DP600 sheet steel.

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Modeling strain-path changes in aluminum and steel

Cited by 33 publications

References 25 publications

Mechanical Anisotropy Induced by Strain Path Change for AZ31 Mg Alloy Sheet

Mechanical Anisotropy Induced by Strain Path Change for AZ31 Mg Alloy Sheet

Regularized Yield Surfaces for Crystal Plasticity of Metals

Strain-path dependent hardening models with rigorously identical predictions under monotonic loading

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