Joachim Danckert

Development of hydro-mechanical deep drawing

Abstract The hydro-mechanical deep-drawing process is reviewed in this article. The process principles and features are introduced and the developments of the hydro-mechanical deep-drawing process in process performances, in theory and in numerical simulation are described. The applications are summarized. Some other related hydraulic forming processes are also dealt with as a comparison.

Applying the finite-element method for determination of tool wear in conventional deep-drawing

Abstract The prediction of tool wear in conventional deep-drawing is accomplished using the finite-element method. The distribution of tool wear on the draw-die profile is obtained and compared to industrial observations. This is achieved by proposing a semi-empirical wear model in which the tool wear is a function of both the normal pressure and the relative velocity between the sheet and the tooling. Furthermore, a parameter study has been carried out to see the effect on the tool wear when changing selected parameters, for example the blank thickness and the strain hardening.

Analysis of the hydromechanical deep drawing of cylindrical cups

The hydromechanical deep drawing process of aluminum cups and mild steel cups is analyzed experimentally and numerically. The effects of the process parameters on the final product quality are discussed. A working zone with a suitable maximum chamber pressure is obtained from the experimental results. The explicit finite element method is used with Hills transversely anisotropic material model for the numerical analysis. The numerical results are compared with those obtained in the experiments, process defects of local thinning are predicted and the thickness variations are discussed

Experimental investigation of a square-cup deep-drawing process

The analysis of the deep-drawing of a square cup has been carried out as part of an international bench-mark research program organised by the NUMISHEET organising committee. Aluminum and mild steel have been employed in the experiments. The draw-in of the flange has been determined for a punch travel equal to 15 and 40 mm. A grid consisting of squares was electrochemically etched on the surface of the blanks, and the principal strains were determined in three directions from grid measurements for the above-mentioned punch travels. The thickness strains were determined also from direct measurements of the thickness, the thickness strains so determined comparing favourably with the thickness strains determined from the grid measurements.

The Residual Stress Distribution in the Wall of a Deep-Drawn and Ironed Cup Determined Experimentally and by FEM

Summary A two stage axisymmetric deep drawing process followed by ironing of the cup wall has been simulated with the explicit FEM code LS-Dyna2D. The results show that the ironing process causes a drastic change in the residual stress distribution; the residual stresses are lowered and a much more favourable distribution with regard to fatigue and stress corrosion is obtained. The FEM results compare favourably with experimental results.

Effect of anisotropy and prebulging on hydromechanical deep drawing of mild steel cups

Abstract The hydromechanical deep drawing processes of mild steel cups have been investigated experimentally and numerically. Experiments were carried out with the fixed gap method (with spacers) and the conventional method (without spacers) under different prebulging pressures. The shape variations and the thickness distributions of the workpieces were measured and discussed. The effects of anisotropy and prebulging pressure on the final product quality are discussed. The processes were analyzed by the explicit finite element code DYNA3D with the Barlat–Lian’s three-parameter material model. The numerical results are compared with those obtained in the experiments.

Hydromechanical deep-drawing of aluminum parabolic workpieces - experiments and numerical simulation

Aluminum parabolic workpieces were formed with hydromechanical deep-drawing technology. The deep-drawing process was analyzed by using the explicit finite element method with various process parameters. Defects of wrinkling and rupture are predicted for some forming conditions, and the thickness distribution results are in good agreement with the experimental results. Thinning mainly takes place during the first third of the punch travel, while wrinkling mainly takes place during the final half-stage of the punch travel. The effects of chamber pressure and blank holding force on the deformation of the workpieces are discussed. The numerical results are compared with those obtained in the experiments.

Numerical model for the oil pressure distribution in the hydromechanical deep drawing process

Abstract This paper presents an attempt to simulate the hydromechanical deep drawing process using the finite element method (FEM). The basic idea is to compute the counter pressure and the fluid film pressure by solving a finite difference approximation of Reynold’s equation. The concept is implemented as a contact algorithm in Exhale2D, an explicit finite element code for two-dimensional analyses. The numerical results illustrate a rather good agreement with experimental data.

Optimization of the draw-die design in conventional deep-drawing in order to minimise tool wear

Abstract An important problem in the production of drawn parts is tool wear, especially at the draw-die. If tool wear can be reduced this can increase the tool lifetime and make a more continuous production flow, due to a reduction in the number of break-downs when the tools have to be re-polished. This paper presents an attempt to reduce tool wear using the finite-element method and a general optimization technique to re-design the geometry of the draw-die profile of a deep-drawing with respect to minimizing the tool wear.

Analysis of the Ring Test Method for the Evaluation of Frictional Stresses in Bulk Metal Forming Processes

Abstract The paper presents a theoretical analysis of the ring test which takes into account the influence from strain hardening and instead of adopting Coulombs law or the concept of a constant friction factor m for describing the frictional stresses, the friction model τ = fαk (f = friction factor, α = ratio between real and apparent area of contact, k = yield stress in pure shear) has been adopted. The analysis shows, that the commonly made assumption that the frictional stresses are constant, is not fulfilled in the ring test and shows that it is possible by adopting the friction model τ = fαk to obtain ring test calibration curves which can be used to evaluate the frictional stresses both at low and high normal surface pressures.