Karl Brian Nielsen

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

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.

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 key parameters in sheet hydroforming combined with stretching forming and deep drawing

Abstract Sheet hydroforming has proven to be an effective method for manufacturing complicated parts. To explore sheet deformation under complex strain conditions, the forming process of a conical cup was studied on the basis of the proposed hydromechanical deep drawing with uniform pressure on to the blank. The failure types including fracture and wrinkling were analysed in detail. The process windows for the pressure in the die cavity were drawn out using the different roughness of the punch surface in local areas. The forming process of the conical cup was explored using pure aluminium and soft steel. Effects of the key process parameters including the punch surface roughness and the pressure variation on the finally formed parts were investigated in both experiment and simulation. It was shown that the results from the simulation were in reasonable agreement with those from the experiment.

Determination of the plastic anisotropy r in sheet metal using automatic tensile test equipment

When the plastic strain ratio r for sheet metal is determined automatically using an automatic tensile testing machine, extensometers for measuring the elongation and width strain and a data processing program, it is required by the norms that compensation for the elastic strains is made. A method is proposed for compensation of the elastic strains when the plastic strain ratio r is determined automatically. It has been verified experimentally that the use of the proposed method gives a r-value that is almost identical to the r-value obtained from measurements carried out on the tensile test specimen in the unloaded condition.

Hydromechanical Deep Drawing with Uniform Pressure on the Flange

Abstract Conventional hydromechanical deep drawing is difficult to simulate due to difficulties regarding the determination of the pressure distribution on the flange when a leak flow occurs between the draw die and the flange. To avoid this problem the hydromechanical deep drawing process has been modified in such a way, that the pressure on the flange is uniform throughout the deep drawing. The uniform pressure on the flange makes it easy to simulate the modified hydromechanical deep drawing process. The modified hydromechnical deep drawing process has been investigated experimentally and the experiments show that the concept works in practice; cylindrical cups made from aluminium have been drawn successfully with a drawing ratio as high as 3.0. The paper presents the modified hydromechanical deep drawing process and experimental results obtained are compared to results obtained using FEM.

Finite element analysis of the hydromechanical deep-drawing process of tapered rectangular boxes

Abstract Tapered rectangular boxes of aluminum and mild steel were formed using the hydromechanical deep drawing process. The experiments are described and discussed, and the process is analyzed numerically using the explicit finite element method. The numerical results are discussed and compared with the experimental results. Blanks of octagonal shape and circular shape and of various dimensions are simulated and compared, suggestions being made on this basis. The failure modes of local thinning and body wrinkling occurring in the experiments are predicted.

Numerical Simulation of the Integral Hydro-Bulge Forming of Non-Clearance Double-Layer Spherical Vessels: Deformation Analysis

Abstract The integral hydro-bulge forming (IHBF) process of non-clearance double-layer spherical vessels is analyzed by means of the explicit finite element code LS-DYNA3D. The deformation process of the double-layer shell from the initially flat-blank frustum shell to the final spherical shape is discussed, the final diameter and its variations, the development of the contact situation and the thickness distribution are fully analyzed. The numerical results agree well with the experimental results. During hydro-bulging, the inner shell is firstly deformed and then the outer shell begins deformation under the contact pressure from the inner shell, the two layer shells contact gradually each other, at the end of the process the two layers completely contact and are deformed into spherical shapes. The thinning is higher near every blank centre, lower at every blank edge and blank corner. The corners can be deformed into spherical shapes with appropriate deformation.