Won-Byong Bae

Finite element analysis on the effect of die clearance on shear planes in fine blanking

Abstract Finite element analysis was performed to investigate the effect of the die clearance on shear planes in the fine blanking of a part of an automobile safety belt. For the analysis, AISI1045 was selected as the material, which was used in manufacturing part of an automobile safety belt, and Cockcroft–Latham fracture criterion was applied. The effect of die clearance on die-roll width, die-roll depth, burnish zone, and fracture zone has been investigated in a finite element analysis by a rigid–plastic FEM code, DEFORM-2D. From the analysis, it was found that die-roll width and depth of the shear plane increase with increasing die clearance. The burnish zone decreases with increasing die clearance, but the variation of the fracture zone is the opposite that of the burnish zone, because the increase in die clearance requires less fracture energy. Theoretical predictions were compared with experimental results. There was significant agreement between theory and experiment.

The effect of V-ring indenter on the sheared surface in the fine-blanking process of pawl

Abstract Finite element analysis has been performed to investigate the effect of V-ring indenter on the sheared surface in the fine blanking of pawl, which is a part of the automotive safety belt and is made of AISI1045 sheet. The Cockcroft and Latham’s fracture criterion and the element kill method are used in order to simulate the blanking operation successfully. Simulation results are obtained for various positions and heights of the V-ring indenter, and the experimental results are compared with theoretical results. It is shown that the FEM simulation results can be useful for predicting the optimal condition for fine blanking products.

A study on the hot-deformation behavior and dynamic recrystallization of Al–5 wt.%Mg alloy

A numerical analysis was performed to predict flow curves and dynamic recrystallization behaviors of Al-5wt%Mg alloy on the basis of results of hot compression tests. The hot compression tests were carred out in the ranges of 350 ~ 500 and 5 ~ 3 /sec to obtain the Zener-Hollomon parameter Z. The modelling equation for flow stress was a function of strain, strain rate, temperature. The influence of these variables was quantifield using the Zener-Hollomon parameter. In the modelling equation, the effects of strain hardening and dynamic recrystallization were taken into consideration. Therefore, the modelling stress-strain curves of Al-5wt%Mg alloy were in good agreement with experimental results. Finally, the dynamic recrystallization kinetics were illustrated through the inspection of microstructure after deformation.

Analysis of tube-spinning processes by the upper-bound stream-function method

Abstract Trapezoidal and spherical velocity fields using the stream function are suggested in tube spinning. In this paper the basic mechanisms of tube spinning are explained. A search is made for the optimum roller oblique angle in terms of process parameters, such as the feed rate, the ratio of the wall thickness reduction and the friction factor. The acquired total power consumption is optimized by the Flexible Tolerance Method which is used for minimizing the multi-variable non-linear function with constraint conditions. Thus the total power consumption required in deformation and the related tangential forces are obtained using the upper-bound stream-function method. The results show that the trapezoid velocity field using the stream function provides the best agreement with the results of model-material experiment.

An experimental study on forming characteristics of pre-coated sheet metals

To analyze the forming and friction characteristics of pre-coated metals (PCMs) that are widely used in household appliances, rectangular deep drawing and friction tests were performed. There were four types of die materials (STD11(TiCN), STD11(TD), STD11, AMPCO) used in the deep drawing tests, and the results show that STD11 and AMPCO are better than others in respect to forming load and surface roughness. The friction mechanism, the thickness of materials and the effect of the roller’s diameter on the friction coefficient and surface roughness were examined in the friction test. The PCMs used in the tests had low friction coefficients (μ=0.15–0.20) in non-lubricated condition due to the coating film acting as lubrication. The friction coefficient decreased as the radius of the roller increased and the surface of product became better as the thickness of the material decreased.

A study of the manufacturing of tie-rod ends with casting/forging process

Abstract Aluminium casting/forging is used to produce aluminium tie-rod ends for the steering systems of automobiles. First, casting experiments were carried out to attain a satisfactory preform for forging of tie-rod ends. In the casting experiment, the effects of additives, Ti+B, Zr, Sr, and Mg, on the mechanical properties and the microstructure of a preform cast were investigated. A finite element analysis was performed to determine an optimal configuration of the cast preform. Lastly, a forging experiment was carried out to make the final product of an aluminium tie-rod end by using the cast preform. In the casting experiments, when 0.2% Ti+B and 0.25% Zr were simultaneously added into a molten Al–Si alloy, the highest values of tensile strength and elongation of the cast perform were obtained. When 0.04% Sr was added into the molten aluminium ally, the finest silicon structure was observed in the cast perform. The highest hardness was obtained when 0.2% Mg was added. In the forging experiment, it was confirmed that the optimal configuration of the perform cast could be predicted by FE analysis. The hardness of a cast/forged product using the designed perform was superior to that of required specifications.

An upper-bound analysis of the backward extrusion of tubes of complicated internal shapes from round billets

Abstract A new kinematically-admissible velocity field is proposed to determine the final-stage extrusion load and the average extruded height in the backward extrusion of internally non-axisymmetric tubes from round billets. The proposed velocity field is applied to the backward extrusion of internally trochoidal gear-shaped tubed and rounded rectangular-shaped tubes, the profile function of a rounded rectangle being approximated by using a Fourier series. Experiments are carried out with fully-annealed commercial aluminum-alloy billets at room temperature using various shaped punches. The theoretical predictions of the extrusion load are in good agreement with the experimental results and there is generally reasonable agreement in average extruded height between theory and experiment.

Analysis of the cogging process for heavy ingots by finite element method and physical modelling method

Abstract For a design of the cogging processes to obtain sound forgings of the monoblock rotor, the effects of forging parameters have been investigated. Parameters such as die configuration, die width and reduction of height have been considered in the design of the process. The three-dimensional finite element analysis is carried out for the cogging processes in order to study the distribution of effective strains, hydrostatic stresses and axial stresses. Physical modelling of 1/40th scale using plasticine modelling clay is performed to verify the results of simulation and to design the process. Optimal working conditions of heavy ingots are suggested for defect-free product quality.

An upper-bound elemental technique approach to the process design of asymmetric forgings

Abstract An upper-bound elemental technique (UBET) program has been developed to predict forging load, die-cavity filling, preform in asymmetric forging. To analyze the process easily, it is suggested that the deformation is divided into two different parts. Those are axisymmetric part in corner, plane-strain part in lateral. The plane-strain and axisymmetric parts are combined by building block method. The total energy is computed through combination of two deformation parts. A dumbbell-type preform has been obtained from height and volumetric compensations of the billet based on the backward simulation. Experiments have been carried out with pure plasticine at room temperature. Theoretical predictions are in good agreement with experimental results.

An analysis of backward extrusion of internally circular-shaped tubes from arbitrarily-shaped billets by the upper-bound method

Abstract A simple kinematically admissible velocity field for the backward extrusion of internally circular-shaped tubes from arbitrarily-shaped billets is proposed. From the proposed velocity field, the upper-bound extrusion load and the average extruded height for regular polygonal-shaped billets and rounded rectangular-shaped billets are determined with respect to chosen parameters. Experiments are carried out with full-annealed aluminum alloy billets at room temperature using four circular-shaped punches. The theoretical predictions of extrusion load are in good agreement with the experimental results. There is also reasonable agreement in average extruded height between theory and experiment.