Evolution of Yield Loci for Aluminum Alloy AA6016 and Deep Drawing Steel DC06 under the Influence of Non-Linear Strain Paths

2013 ◽  
Vol 549 ◽  
pp. 21-28 ◽  
Author(s):  
Marion Merklein ◽  
Sebastian Suttner
Keyword(s):  
Aluminum Alloy ◽  
Deep Drawing ◽  
Strain Path ◽  
Material Behavior ◽  
Linear Strain ◽  
Hardening Behavior ◽  
Strain Paths ◽  
Yield Loci ◽  
Strain Path Changes ◽  
Stress States

The application of modern materials plays an important role directly under the aspect of lightweight potential. To exploit these options effectively a numerical accurate reproduction of the material behavior is indispensable. Especially in the case of large deformations a directional and strain rate dependent hardening behavior can be observed. By disregarding this effect significant failure in the computed stress state can arise, which can conduct to a corruption of the spring-back forecast. Within this contribution a new test method for analyzing the evolution of subsequent yield loci under strain path changes for the aluminum alloy AA6016 and the deep drawing steel DC06 is presented. In the first stage of the experimental investigations, yield loci with linear strain paths were considered to characterize the material behavior for the initial condition. On further experiments with several stress states the strain path dependent hardening behavior of the material is determined. The non-linear strain paths are realized through uniaxial prestrained primary specimens with following extraction of secondary samples for following stress states, e.g. a modified ASTM simple shear test specimen. Subsequent yield loci are investigated and compared to the yield surfaces Hill48 and Barlat 2000 (Yld2000-2d) with an isotropic hardening behavior. With this study the evolution of the yield locus for prestrained specimens is evaluated. The research of the subsequent yield loci for strain path changes serves as basis for further scientific investigations with a view to assess different approaches of isotropic-kinematic hardening models in consideration of the analyzed steel and aluminum sheet metals.

An Experimental Investigation of the Yield Loci of 1100-0 Aluminum, 70:30 Brass, and an Overaged 2024 Aluminum Alloy After Various Prestrains

1986 ◽  
Vol 108 (4) ◽  
pp. 313-320 ◽  
Author(s):  
D. E. Helling ◽  
A. K. Miller ◽  
M. G. Stout
Keyword(s):  
Aluminum Alloy ◽  
Small Strain ◽  
Yield Locus ◽  
Material Behavior ◽  
Shear Stresses ◽  
2024 Aluminum Alloy ◽  
Yield Loci ◽  
Aluminum Alloy 2024 ◽  
Von Mises ◽  
Normal And Shear Stresses

The multiaxial yield behaviors of 1100-0 aluminum, 70:30 brass, and an overaged 2024 aluminum alloy (2024-T7) have been investigated for a variety of prestress histories involving combinations of normal and shear stresses. Von Mises effective prestrains were in the range of 1.2–32%. Prestress paths were chosen in order to investigate the roles of prestress and prestrain direction on the nature of small-strain offset (ε = 5 × 10−6) yield loci. Particular attention was paid to the directionality, i.e., translation and distortion, of the yield locus. A key result, which was observed in all three materials, was that the final direction of the prestrain path strongly influences the distortions of the yield loci. Differences in the yield locus behavior of the three materials were also observed: brass and the 2024-T7 alloy showed more severe distortions of the yield locus and a longer memory of their entire prestrain history than the 1100-0 aluminum. In addition, more “kinematic” translation of the subsequent yield loci was observed in brass and 2024-T7 than in 1100-0 aluminum. The 2024-T7 differed from the other materials, showing a yield locus which decreased in size subsequent to plastic straining. Finally, the implications of these observations for the constitutive modeling of multiaxial material behavior are discussed.

Orientation and Path Dependence of Formability in the Stress- and the Extended Stress-Based Forming Limit Curves

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
C. Hari Manoj Simha ◽  
Kaan Inal ◽  
Michael J. Worswick
Keyword(s):  
Strain Path ◽  
Path Dependence ◽  
Forming Limit ◽  
Stress Space ◽  
Forming Limit Diagrams ◽  
Metall Trans ◽  
Strain Paths ◽  
Strain Path Changes ◽  
Path Dependent ◽  
Forming Limit Curves

This article analyzes the formability data sets for aluminum killed steel (Laukonis, J. V., and Ghosh, A. K., 1978, “Effects of Strain Path Changes on the Formability of Sheet Metals,” Metall. Trans. A., 9, pp. 1849–1856), for Al 2008-T4 (Graf, A., and Hosford, W., 1993, “Effect of Changing Strain Paths on Forming Limit Diagrams of Al 2008-T4,” Metall. Trans. A, 24A, pp. 2503–2512) and for Al 6111-T4 (Graf, A., and Hosford, W., 1994, “The Influence of Strain-Path Changes on Forming Limit Diagrams of Al 6111 T4,” Int. J. Mech. Sci., 36, pp. 897–910). These articles present strain-based forming limit curves (ϵFLCs) for both as-received and prestrained sheets. Using phenomenological yield functions, and assuming isotropic hardening, the ϵFLCs are transformed into principal stress space to obtain stress-based forming limit curves (σFLCs) and the principal stresses are transformed into effective stress and mean stress space to obtain the extended stress-based forming limit curves (XSFLCs). A definition of path dependence for the σFLC and XSFLC is proposed and used to classify the obtained limit curves as path dependent or independent. The path dependence of forming limit stresses is observed for some of the prestrain paths. Based on the results, a novel criterion that, with a knowledge of the forming limit stresses of the as-received material, can be used to predict whether the limit stresses are path dependent or independent for a given prestrain path is proposed. The results also suggest that kinematic hardening and transient hardening effects may explain the path dependence observed in some of the prestrain paths.

Effect of Plastic Anisotropy on Forming Limit Prediction

2005 ◽  
Vol 495-497 ◽  
pp. 1573-1578 ◽  
Author(s):  
S. He ◽  
Albert Van Bael ◽  
Paul van Houtte
Keyword(s):  
Strain Path ◽  
Plastic Anisotropy ◽  
Yield Locus ◽  
Material Behavior ◽  
Forming Limit ◽  
Sheet Metals ◽  
Forming Process ◽  
Forming Limit Diagrams ◽  
Strain Path Changes ◽  
Complex Strain

A model based on Marciniak-Kuczynski (M-K) theory [1] for the prediction of forming limit diagrams (FLDs) for anisotropic sheet metals is presented. The plastic anisotropy is taken into account by the shape of the yield locus generated on the basis of measured crystallographic texture. As a result, not only the material behavior during the monotonic loading can be well described and predicted, but also the complex strain-path changes during the forming process can be taken into account. Examples of predicted FLDs for two aluminum alloys are given. Comparisons with experimental results are presented.

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

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1049
Author(s):  
Chong Yang ◽  
Yibing Mei ◽  
Dan Meng ◽  
Guoguo Zhu ◽  
Shengwei Liu ◽  
...  
Keyword(s):  
Yield Strength ◽  
Strain Path ◽  
Texture Evolution ◽  
Rolling Direction ◽  
Mechanical Anisotropy ◽  
Heterogeneous Distribution ◽  
Az31 Sheet ◽  
Strain Paths ◽  
Strain Path Change ◽  
Strain Path Changes

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.

Evaluation of the Work-Hardening of Brass Sheets Following Strain Path Changes

2010 ◽  
Vol 89-91 ◽  
pp. 353-358
Author(s):  
Wellington Lopes ◽  
Elaine Carballo Siqueira Corrêa ◽  
Haroldo Béria Campos ◽  
Maria Teresa Paulino Aguilar ◽  
Paulo Roberto Cetlin
Keyword(s):  
Simple Shear ◽  
Work Hardening ◽  
Tensile Testing ◽  
Strain Path ◽  
Adequate Description ◽  
Simple Tension ◽  
Strain Paths ◽  
Strain Path Changes ◽  
Machining Operations

The strain paths followed by metals during sheet forming can be quite complex, especially when successive forming steps are involved. The work hardening of metals associated with these strain paths differs from that caused only by monotonic straining, such as simple tension or compression. It is important to have an adequate description of the work hardening of the material under processing, especially when numerical simulations of the forming are used. The experimental evaluation of the effect of strain path changes on the material work hardening is usually performed through tensile testing following the strain path changes. This technique, however, demands complex machining operations of the formed sheets and the imposed strain is severely limited by impending necking. The present paper utilizes simple shear as a tool for the determination of the work hardening of CuZn34 brass sheets following various strain path changes associated with combinations of different modes of deformation such as rolling, tension, cyclic and forward shears. The results indicate that the cyclic shearing delays the occurrence of plastic instabilities for brass previously tensioned, occurring the opposite for final monotonic shearing. These phenomena were correlated with the probable microstructural evolution of the CuZn34 brass.

A Theoretical Study of the Effect of the Double Strain Path Change on the Forming Limits of Metal Sheet

2013 ◽  
Vol 554-557 ◽  
pp. 127-138 ◽  
Author(s):  
Marilena Butuc ◽  
Frédéric Barlat ◽  
José Grácio ◽  
Gabriela Vincze
Keyword(s):  
Sheet Metal ◽  
Strain Path ◽  
Theoretical Study ◽  
Alloy Sheet ◽  
Initial Shape ◽  
Forming Limits ◽  
Remarkable Effect ◽  
Strain Paths ◽  
Strain Path Change ◽  
Strain Path Changes

The present paper aims at a theoretical study of the forming limits of a sheet metal subjected to double strain path changes by using as reference material the AA6016-T4 aluminum alloy sheet. The simulation of plastic instability is carried out through the Marciniak-Kuczynski analysis. The initial shape of the yield locus is given by the Yld2000-2d plane stress yield function. The strain hardening of the material is described by the Voce type saturation law. Linear and several complex strain paths involving single and double strain path changes are taken into account. The validity of the model is assessed by comparing the predicted and experimental forming limits under linear and selected one strain path change. A good accuracy of the developed software on predicting the forming limits is found. A sensitive analysis of the influence of the type and value of the double prestain in the occurrence of the plastic flow localization is performed. A remarkable effect of the double strain path change on the sheet metal forming limits is observed.

Analysis of Nonisothermal Deep Drawing of Aluminum Alloy Sheet With Induced Anisotropy and Rate Sensitivity at Elevated Temperatures

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Kamyar Ghavam ◽  
Reza Bagheriasl ◽  
Michael J. Worswick
Keyword(s):  
Aluminum Alloy ◽  
Strain Rate ◽  
Deep Drawing ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Alloy Sheet ◽  
Material Behavior ◽  
Aluminum Alloy Sheet ◽  
Rate Dependency ◽  
Strain Rate Dependency

In this paper, a finite element model is developed for 3000 series clad aluminum alloy brazing sheet to account for temperature and strain rate dependency, as well as plastic anisotropy. The current work considers a novel implementation of the Barlat YLD2000 yield surface in conjunction with the Bergstrom hardening model to accurately model aluminum alloy sheet during warm forming. The Barlat YLD2000 yield criterion is used to capture the anisotropy while the Bergstrom hardening rule predicts the temperature and strain rate dependency. The results are compared with those obtained from experiments. The measured stress–strain curves of the AA3003 aluminum alloy sheet at elevated temperatures and different strain rates are used to fit the Bergstrom parameters and measured R-values and directional yield stresses are used to fit the yield function parameters. Isothermal uniaxial tensile tests and nonisothermal deep drawing experiments are performed and the predicted response using the new constitutive model is compared with measured data. In simulations of tensile tests, the material behavior is predicted accurately by the numerical models. Also, the nonisothermal deep drawing simulations are able to predict the load–displacement response and strain distributions accurately.

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