Experimental fracture characterisation of an anisotropic magnesium alloy sheet in proportional and non-proportional loading conditions

Formability of austenitic and ferritic stainless steels at warm forming temperature

This paper reviews the most recent models for description of the anisotropic plastic behavior and formability of sheet metals. After a brief review of classic isotropic yield functions, recent advanced anisotropic criteria for polycrystalline materials of various crystal structures and their applications to cup drawing are presented. Next, the discussion focuses on novel formulations of anisotropic hardening. A brief review of the experimental methods used for characterizing and modeling the anisotropic plastic behavior of metallic sheets and tubes under biaxial loading is presented. The experimental methods and theoretical models used for measuring and predicting the limit strains, development of new tests for determining the Forming Limit Curves (FLC), as well as on studying the influence of various material or process parameters on the limit strains are presented.

Advances in anisotropy of plastic behaviour and formability of sheet metals

Elevated temperature constitutive behavior and simulation of warm forming of AZ31B

Warm forming has some important advantages, the most significant being that forming limit strains increase at elevated temperatures. To quantify this advantage for an AA3003 brazing sheet, forming limit diagrams were determined using warm tooling developed to perform limiting dome height (LDH) experiments together with a digital image correlation (DIC) system used to perform in situ strain measurement. Forming limit curves (FLCs) were developed at several temperature levels and strain-rates. The formability experiments demonstrated that while temperature has a significant effect on formability, forming speed has a mild effect within the studied range. Elevating the temperature to 250 °C improved the formability more than 200 % compared to room temperature forming while forming at lower speeds increased the limiting strains by 10 % and 17 % at room temperature and 250 °C, respectively. A comparison between FLDs developed using DIC methods versus circle grid (CG) analysis showed good agreement between the two methods; however, the degree of scatter in the CG method increased significantly for the higher temperature tests.

Formability of AA3003 brazing sheet at elevated temperatures: limiting dome height experiments and determination of forming limit diagrams

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

A combined experimental and numerical study of the effects of die and punch temperature on the formability of a modified AA3003 aluminum alloy sheet for a case study sample is presented. Here, the non-isothermal deep drawing of a cup-like feature in a thin gauge aluminum automotive component is considered. An experimental forming setup that incorporates both heated dies and a cooled punch has been developed. A parametric study of the effects of die temperature, punch temperature, and blank holder force on the formability of the part is conducted. Numerical simulations of the warm forming process are performed using a coupled thermo-mechanical finite element model. The temperature-dependant material model combines the Bergstrom hardening rule with Barlat’s YLD2000 yield function and was implemented in LS-DYNA as a user-defined material model. Selected experimental cases were modelled numerically and compared to experiments. The FEA model was validated against experimental results by comparing measured and predicted punch force versus displacement as well as trends in the formability as a function of die temperature.

Formability improvement with independent die and punch temperature control

The effect of temperature on formability of aluminum alloy sheet is studied by developing the Forming Limit Diagrams, FLD, for aluminum alloy 3000‐series using the Marciniak and Kuczynski technique by numerical simulation. The numerical model is conducted in LS‐DYNA and incorporates the Barlat’s YLD2000 anisotropic yield function and the temperature dependant Bergstrom hardening law. Three different temperatures; room temperature, 250° C and 300° C, are studied. For each temperature case, various loading conditions are applied to the M‐K defect model. The effect of the material anisotropy is considered by varying the defect angle. A simplified failure criterion is used to predict the onset of necking. Minor and major strains are obtained from the simulations and plotted for each temperature level. It is demonstrated that temperature improves the forming limit of aluminum 3000‐series alloy sheet.

Formability analysis of aluminum alloy sheets at elevated temperatures with numerical simulation based on the M‐K method

To investigate the effectiveness of the warm forming a coupled thermo-mechanical model is developed in LS-Dyna. The temperature dependant material properties of the material, a long-life 3000 series clad aluminum alloy brazing sheet are modelled using a user defined material subroutine accommodating the Barlat YLD2000 anisotropic plane-stress yield surface and the physically motivated Bergstrom hardening rule. The maximum thickness reduction is adopted as a simplified failure criteria to determine both the location and failure depth for the numerical models. The original progressive tooling is modified to incorporate the application of individual temperatures on the dies and the punch. The dies (die and blank holder) are heated with embedded cartridge heaters and the punch is cooled by circulation of chilled water. Select experimental cases are modelled. FEA model is validated against experimental results by comparing punch force versus displacement as well as failure location. The numerical results for either successful or failed simulations are compared with corresponding experimental samples.

Reza Bagheriasl

Papers

Formability of AA3003 brazing sheet at elevated temperatures: limiting dome height experiments and determination of forming limit diagrams

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

Formability improvement with independent die and punch temperature control

Formability analysis of aluminum alloy sheets at elevated temperatures with numerical simulation based on the M‐K method

An effective warm forming process; numerical and experimental study