Development of reversed deep drawing without blank-holder for producing brass elliptical cup

A new technique “Reverse Deep Drawing Process” without blank holder was adopted, for the single stage to produce an elliptical cup through an elliptical die. In this process an elliptical-cup is produced by pushing an elliptical blank using a hollow elliptical punch through an elliptical die in a single stroke. FEM via ANSYS is used to analyze this process. The clearance ratio was varied to study its effect on some parameters of this process like load, stress, strain, thickness distributions. A die with clearance =1mm and blank thickness=1mm gave the best drawability in this technique and no wrinkling observed on the product but it has minimum earring. Several attempted have been done to get the shape and dimensions of the blank, the major axis (a) =85mm & the minor axis (b) =65 mm was the better blank for this process to produce elliptical cup of major axis is twice minor axis. Good agreements are evident between the experimental and finite element results; the discrepancy is 4.0797% for load-extension and 0.852% for the wall thickness in minor axis and 1.145% in major axis.

Reverse deep drawing process: Material anisotropy and work-hardening effects

The present work aims to study the constitutive models’ influence on the reverse deep drawing simulation of cylindrical cups. Several constitutive laws were considered to predict the combined effects of anisotropy as well as the changes in strain path direction of the stainless steel. To this end, a number of models were used, worth mentioning among which are the isotropic with nonlinear kinematic hardening laws, along with the isotropic von Mises and anisotropic Hill’48 yield criteria. For the models’ parameters identification, uniaxial tensile and shear tests at several orientations to the rolling direction as well as reversed shear tests were carried out. Then, a subsequent comparison between experimental data and numerical simulations of reverse deep drawing tests were performed, using the finite element code Abaqus/Explicit. On the basis of the major reached results, it has been found that for the first stage, whatever the yield criteria used and for all the hardening models, the numerical punch-force evolution correlates well with the experimental one. For the second stage, the punch-force evolution was found to be remarkably more influenced by the yield criteria than by the kinematic laws. The major strain distribution greatly depends on the yield criteria. Meanwhile, it was slightly linked to the work hardening.

Applying Nagata Patches in the Description of Smooth Tool Surfaces Used in Sheet Metal Forming Simulations

This study deals with the new strategy currently implemented in DD3IMP in-house code to describe the forming tools using Nagata patches. The strategy is based on the use of the Nagata patch interpolation to generate smooth contact surfaces over coarse faceted finite element meshes. The description of the adopted algorithm is briefly presented, highlighting the contact search algorithm employed. The reverse deep drawing of cylindrical cups, proposed as benchmark at the Numisheet’99 conference, is selected to examine the accuracy and robustness of the proposed approach. The effect of the gap between the blank-holder and the die is studied, adopting two distinct strategies: fixed gap and variable gap. The numerical results are compared with the experimental ones, previously presented and discussed in [1]. It is shown that the agreement is very good both in terms of punch force evolution and thickness distribution.

Deformation Optimization for Inconel718 Superalloy Sheet Hydroforming Numerically and Experimentally

For deep cylindrical cups with a large height-diameter ratio, it is difficult to be hydroformed in one stroke. Reverse deep drawing is necessary after deep drawing. Deformation optimization was performed to achieve a large drawing ratio and uniform thickness. An inconel718 superalloy deep cup was investigated numerically and experimentally. For a larger total drawing ratio 3.1, different deformations were analyzed for hydromechanical deep drawing and reverse hydromechanical deep drawing under the condition of different loading paths. Effects of deformations were discussed on the thickness. Typical defects were analyzed for different deformation. Optimal deformation was determined for hydromechanical deep drawing and reverse hydromechanical deep drawing. The results show that a superalloy cup with a total drawing ratio 3.1 could be successfully hydroformed, and the minimum thickness is 0.65 mm.