Non-isothermal Deep Drawing Research Articles

Experimental investigation of non-isothermal deep drawing of DP600 steel

To increase the limiting drawing ratio (LDR) in deep drawing, experiments are conducted on DP600, IF, and HSLA steels. The flange region of blank is heated up to temperatures in the warm range by inductance heating. During heating, the central portion of blank is cooled by water to prevent the reduction of the strength of the material in the central region. The temperature increase of flange region is observed by two infrared sensors focusing on two different points, one on the blank rim and the other near the die radius. An intensive cooling by cold water is applied to the bottom side of a blank during deep drawing. Increases up to 25.58% on LDR are obtained. There is no significant change in the microstructure of the material due to warm forming. Material characterization is obtained by a Gleeble 3800 thermo-mechanical testing machine for the temperature range 150–300 °C.

Improvement in Material Flow During Nonisothermal Warm Deep Drawing of Nonheat Treatable Aluminum Alloy Sheets

Automotive industries are very much interested in implementing warm forming technology for fabrication of light weight auto-body panels using aluminum alloys without localized thinning or splitting. A nonheat treatable and low formable AA5754-H22 aluminum alloy sheet was selected in the present work, and a laboratory scale warm deep drawing test set-up and process sequences were designed to improve material flow through independent heating of punch and dies. Significant enhancement in cup depth was observed when the temperature of punch and dies were set to 30 °C and 200 °C, respectively. Thermo-mechanical finite-element (FE) model of the nonisothermal deep drawing test was developed successfully to study the improvement in material flow incorporating Barlat-89 yield theory using temperature dependent anisotropy coefficients and Cowper–Symonds hardening model. It was found that a nonisothermal temperature gradient of approximately 93 °C was established within the blank from the center to flange at the start of deformation, and subsequent evolution of temperature gradient helped in improving material flow into the die cavity. The effect of temperature gradient on forming behavior in terms of cup height, ear profile, and thinning development across flange, cup wall, and blank center were predicted and validated with experimental results.

Nonisothermal warm deep drawing of SS304: FE modeling and experiments using servo press

Experimental and viscoplastic finite element analysis (FEA) of thermo-mechanical plastic deformation in nonisothermal warm deep drawing is studied using SS304. A nonisothermal deep drawing tool is used in a servo-motor-controlled press. Drawability window of SS304 under elevated temperatures (25–225 °C) and low to high strain rates (drawing speeds of 2.5, 25, and 50 mm/s) were determined. A viscoplastic thermal material model is adopted for nonwork softening material behaviors, as seen in low-temperature forming of SS304, and found to be easily applicable and quite satisfactory. Tensile and equi-biaxial bulge tests were conducted for more accurate flow stress data to be used in FEA. Measured punch load–stroke and cup’s curvilinear thickness (rolling/transverse) curves were successfully compared with predictions from the nonisothermal FE model of the warm deep drawing.

Elevated temperature constitutive behavior and simulation of warm forming of AZ31B

Tension and compression testing has been performed over a wide range of temperatures (23–250°C), strain rates (0.001–1s−1) and material orientations to characterize the mechanical response of AZ31B-O. Instantaneous r-values were measured and their evolution with plastic strain. A strong evolving asymmetry/anisotropy is observed comparing the tension and compression flow stresses and r-values at room temperature, while weaker anisotropy/asymmetry is seen at higher temperatures. Higher strain rate sensitivity is measured at elevated temperatures. An evolving anisotropic/asymmetric continuum level material model based on a CPB-type yield function (Cazacu et al., 2006), as modified by Ghaffari Tari et al. (2014), was used to fit the material behavior at different temperatures. Two approaches are considered to introduce thermal softening and strain rate sensitivity. For isothermal conditions, a rate-sensitive Cowper–Symonds strain hardening model, fit at individual temperatures, captured the material behavior well. For non-isothermal conditions, a strain rate and temperature dependent hardening response based on a modified Nadai model was used. Both approaches have been coded into a user material subroutine within the commercial finite element package, LS-DYNA and used to simulate limiting dome height experiments performed at 250°C and non-isothermal deep drawing experiments in which the temperature distribution within the blank ranged between 170°C and 250°C.

Temperature Controlling System Design of Non-Isothermal Deep Drawing Mould for Magnesium Alloy Sheet

The temperature and its distribution of non-isothermal deep drawing mould is one of the key technologies for magnesium alloy sheet forming process. It exerts a tremendous influence on the service life of deep drawing mould and affects magnesium alloy sheet deep drawing effect. An intelligent PID temperature controller with adaptive ability and self-organization was proposed to control the temperature of non-isothermal deep drawing mould, which included disk-shaped resistance heating coils heating die and blank holder, room temperature water cooling punch of the mould. The temperature control system greatly improved the quality of deep drawing parts of magnesium alloy sheet due to its simple structure, high anti-interference and high controlling precision.

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

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.

Formability improvement with independent die and punch temperature control

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.

Using Servo-Drive Presses to Determine the Effect of Blank Holder Pressure on Temperature Change in Warm Forming of Sheet

Heat transfer coefficient (HTC) is one of the most important and difficult-to-obtain parameter in high temperature environment. Contact pressure and workpiece surface roughness are among important parameters that affect the heat transfer in elevated temperature forming of sheets. In this study, HTCs are investigated experimentally by using a servo-drive press. With the flexibility that the servo-drive press offers, effect of various blank holder pressures on temperature change is determined. Before and after surface roughness conditions of aluminum and magnesium (from two different manufacturers) alloy sheets are compared. Experimental setup was modeled using deform 2d, and measured temperature curves were compared with the finite element analysis (FEA) predictions and a window of heat transfer coefficients were determined for warm forming of sheets. Determined heat transfer coefficients were implemented in a nonisothermal deep drawing FE model in deform 2d and results were compared with experiments. Good agreement was obtained between FEA predictions and experiments.

Warm Forming Simulation of Dual-Phase Steel Tailor-Welded Blanks Based on Thermo-Mechanical Coupled Method

A thermo-mechanical coupled finite element model for warm forming of dual-phase steel (DP) laser tailor-welded blanks (TWBs) was established based on ABAQUS software. The isothermal deep drawing of rectangular cups at elevated temperatures and the non-isothermal deep drawing at the temperature of 400°C were simulated. The distributions of temperature and differences between the isothermal and non-isothermal conditions were discussed. The results show that the temperature has great effect on the warm forming of DP-TWBs, and it achieves the best formability at the forming temperature of 400°C, and the non-isothermal deep drawing can further improve the warm formability.

Mechanical properties and deep drawability of Mg–Gd–Y–Zr alloy rolling sheet at elevated temperatures

Mechanical properties and deep drawability of Mg–Gd–Y–Zr alloy rolling sheet were systematically studied. For this purpose, uniaxial tensile tests were conducted to investigate mechanical properties, strain rate sensitivity parameter (m-value) and plastic strain ratio (R-value) of the sheet at elevated temperatures. The sheet exhibited a high strength at 513K and superplasticity above 623K. The m-value and R-value ranged from 0.07 to 0.32 and 0.9 to 1.4, respectively. Non-isothermal deep drawing experiments were performed to explore the influence of technical parameters on deep drawability. For comparison purpose, traditional AZ31 sheet was chosen for testing on the same device. Limiting drawing ratio (LDR) of Mg–Gd–Y–Zr sheet reached >5.2 that was much higher than that of AZ31 sheet. Textures of the initial sheet and the necking regions for post-deforming cylindrical cups were measured. It is suggested from texture analysis that the activation of pyramidal slip system accounted for the locally necking of the cup-wall. The excellent drawability of Mg–Gd–Y–Zr sheet was attributable to its relatively stronger temperature sensitivity of flow stress and was not connected with an exceptional R-value or m-value.

An Experimental Study on Nonisothermal Deep Drawing Process Using Aluminum and Magnesium Alloys

Weight reduction is one of the major goals in the automotive, appliance, and electronics industries. One way of achieving this goal is to use lightweight alloys such as aluminum and magnesium that have high strength to weight ratios. However, due to their limited formability at room temperature, forming needs to take place at elevated temperatures and mostly under nonisothermal conditions. In this study, nonisothermal deep drawing process using aluminum and magnesium alloys was investigated using a servo motor driven press and a heated tool set. Using the flexibility of the servo press kinematics, blanks were heated in the tool set prior to forming. Temperature-time measurements were made at various blank holder interface pressures in order to determine the required dwell time to heat the blank to the forming temperature. Several lubricants for elevated temperature forming were evaluated using the deep draw test, and a PTFE based film was found to be the best performing lubricant. Deep drawing tests were conducted to determine the process window (maximum punch velocity as functions of blank size and temperature) for Al 5754-O and Mg AZ31-O. Maximum punch velocities of 35 mm/s and 300 mm/s were obtained for the Al and Mg alloys, respectively. Comparisons for the Mg alloy sheets from two different suppliers were made and significant differences in formability were found. Experiments were conducted in order to understand the effect of constant and variable punch velocity and the temperature on the mechanics of deformation. Variable punch velocity is found to improve the thickness distribution of the formed part.

Finite element analysis and formability of non-isothermal deep drawing of AZ31B sheets

Magnesium alloys exhibit poor formability at room temperature, but the formability can be improved at elevated temperature. In this study the formability and non-isothermal deep drawing at elevated temperature of magnesium alloy AZ31B sheets is studied by experiment and finite element analysis. The forming temperature, lubricant and sheet thickness are considered in this study. The experimental results indicate that the highest limit drawing ratio (LDR) is at a forming temperature of 260°C for 0.58mm thick AZ31B sheet, and the highest LDR is 2.63. The highest LDR is at a forming temperature of 200°C for 0.50mm thick AZ31B sheet, and the highest LDR is 2.5. The experimental data shows a good agreement with the simulation results.