• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.312-317
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• 2005

In this study, using the stamping, analysis program, PAM STAMP, applied to the drawing result of springback analysis and draw analysis with applying on the best design planning as many times simulations from the initial stage of the die developing of automotive panels. Especially, after inspecting the design method with stamping analysis and springback analysis, write about the die development examples, using CADCEUS which is the software revising the amount of springback.

• Transactions of Materials Processing
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• v.15 no.4 s.85
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• pp.281-288
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• 2006

Most of automobile member parts experience severe springback problems because of their complicated shape and high yielding strength. Now it becomes imperative to develop an effective method to resolve these problems. However, there remain several obstacles to get accurate estimation of dimensional shape. Especially the effective algorithms to simulate sheet metal forming processes including drawing, trimming, flanging and springback is demanded for the multi stage simulation of automobile member parts. In this study, for the purpose of accurate springback calculation, a simulation program which is robust in springback analysis is developed. Favorable enhancement in computation time for springback analysis by using latest equation solving technique and robust solution convergence by continuation method are achieved with the program. In analysis, the multi processes of rear side member are simulated to verify the system. For the evaluation of springback accuracy practically, all conditions including boundary conditions for springback analysis and inspection conditions for dimensional accuracy are applied. The springback results of simulations show good agreement with the experiments.

• Transactions of Materials Processing
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• v.9 no.6
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• pp.574-581
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• 2000

A vertically-walled auto-body part is one of the most difficult stamping parts because of angle change, wall curl, and twisting of the blank after springback as well as fracture and wrinkle. In this study, computational simulations of the vertically-walled auto-body part are carried out focusing on angle change, wall curl, and twisting after springback. Binderwrap blank shape is used in forming analysis for precise initial contacts between punch and blank. An adaptive mesh method is used in springback analysis for precise calculation of bending moments. In springback analysis, the differences of 2 and 3 dimensional analysis are compared and the effects of blank holdig force and friction coefficient are evaluated. In order to verify the validity of simulation results, they are compared with measured ones. The predicted thickness distribution and formed shape are agreed well with those of the measurement. The Predicted springback amount is less than that of the measurement.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.144-147
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• 2002

In this study, springback analysis of side rear member is carried out. Side rear member is one of the parts which shows severe springback problems. Forming, trimming, flanging and springback stages can be analyzed successively. From forming analysis, we identified the possible spots in which tearing may occur and can prevent failure. In springback analysis we used the boundary conditions same as applied to the blank on the checker so that the computational result can be compared with experimental one. Form .the comparison, springback analysis can yield relatively good results in a qualitative sense. However, in order to get good deformation result quantitatively, there still remains unsettled tasks in the forming analysis with very small die radius. It is found that we have to develop the element with better bending characteristics and precise contact treatment.

• Transactions of Materials Processing
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• v.6 no.5
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• pp.386-394
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• 1997

The analysis of the springback is done based on the stress of sheet after forming. Therfore, it is important to get the accurate stress from forming analysis. In this study, some parameters that influence on the accuracy of the springback estimation are investigated. Discretization of sheet and tools, choice of penalty constant and damping in contact treatment, and tool speed scaling are chosen as parameters. As a numerical example, the 2D draw bending benchmark problem of the NUMISHEET'93 is used. Also, the springback results of the s-rail benchmark problem of the NUMISHEET'96 are presented.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.649-656
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• 2008

Springback is one of factors affecting precision in metal forming. Its effect is particularly prominent in bending process. In this study, bending and forging process are used in order to manufacture a micro spring with two bending region from $60{\mu}m$ diameter wire. Springback in the process lowers the precision of the micro spring. Overbending for springback compensation has wide usage in a general way. However, this method requires repeated modifications of press dies until the tolerance is allowable, which causes that production cost and time increase. In this paper, we analyzed the mechanism of springback in the forming process of the micro spring using finite element method. In addition, a simple method to control springback without modifying dies was proposed by performing numerical analysis with various parameters.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.211-218
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• 2000

It is desirable but difficult to predict springback quantitatively and accurately for successful tool and process design in sheet stamping operations. The result of springback analysis by the finite element method (FEM) is sensitively influenced by numerical factors such as blank element size, number of integration points, punch velocity, contact algorithm, etc. In the present work, a parametric study by Taguchi method is performed in order to evaluate the influence of numerical factors on the result of springback analysis quantitatively and to obtain the combination of numerical factors which gives the best approximation to experimental data. Since springback is determined by the residual stress after forming process, it is important to evaluate stress distribution accurately. The oscillation in the time history curve of stress obtained by the dynamic-explicit finite element method says that the stress solution at termination time is in very unstable state. Therefore, a variability study is also carried out in this study in order to assess the stability of implicit springback analysis starting from the stress solution by explicit forming simulation. The U-draw bending process, one of the NUMISHEET '93 benchmark problems, is adopted as an application model because it is most popular one for evaluating the springback characteristic.

• Design & Manufacturing
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• v.12 no.2
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• pp.40-45
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• 2018

Recently, in construction equipment machinery production, development has focused on environmentally-friendly functions to improve existing production capacity. For excavators as well, emphasis has been placed on response to environmental regulations, miniaturization, and noise reduction, while technology is being developed considering cost reduction and safety.Accordingly, the front support, an inner reinforcement part of the excavator, as well as high-strength steel plates to improve safety and reduce weight, are being applied.However, in the case of high-strength materials, Springback occurs in the final formed part due to high residual stress during product forming. Derivation of a forming or product shaping process to reduce springback is needed. Accordingly, regarding the front support, an inner reinforcement part of the excavator, this study derived a method to improve springback and secure shape stiffness through analysis of the springback occurrence rate and springback causes through a forming analysis.As for the results of analyzing the springback occurrence rate of existing products through forming analysis, springback of -22.6 mm < z < 27.35 mm occurred on the z-axis, and it was confirmed that springback occurred due to the stiffness reinforcing bead of the upper and middle parts of the product.To control product residual stress and springback, we confirmed a tendency of springback reduction through local pre-cutting and stiffness reinforcement bead relocation.In the local pre-cutting model, springback was slightly reduced by 5.3% compared with the existing model, an insignificant reduction effect. In the stiffness reinforcement bead relocation model, when an X-shaped stiffness reinforcement bead was added to each corner portion of the product, springback was reduced by at least 80%.The X-shaped bead addition model was selected as the springback reduction model, and the level of stiffness compared to the existing model was confirmed through a structural analysis.The X-shaped bead additional model showed a stress springback of 90% and springback reduction of 7.4% compared with the existing model, indicating that springback and stiffness will be reinforced.

• Transactions of Materials Processing
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• v.25 no.1
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• pp.21-28
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• 2016

In the current study, reduction of springback is quantified and the reasons for the reduction are investigated. The testing involved a digital servo motion applied to a U-draw bending to produce a hat-type product from high strength steels such as DP780 and DP980. The change in springback is compared between the constant speed motion and three kinds of servocontrolled motions during forming experiments. In order to predict the springback for the servo-controlled tool motion, a finite element method was utilized for the springback analysis considering a kinematic hardening model for the steel. The comparison of springback between the analysis and the experiments shows that they have similar tendencies. Also, the analysis results indicate that the springback reduction is greatly influenced by a decrease in the friction coefficient, which originates from the contact and detach phenomena between the tooling and the blank during the up-and-down motion of the upper die following the servo-controlled motion.

• Transactions of Materials Processing
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• v.13 no.5
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• pp.409-414
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• 2004

TRIP steel has got attention in automobile industry because of its high strength and high formability. However, the information on deformation behavior of TRIP steel, including bending and springback, is not enough until now. In this research, the V-die bending experiment and analysis have been done to obtain the information of springback of TRIP steel. And a new numerical method, where elastic modulus is varied with the change of the strain, was suggested. Tensile test for TRIP steel was done to get tensile properties as well as strain dependency of elastic modulus of the material. Strain-dependency of elastic modulus was used the numerical analysis of V-die bending and unbending process to predict springback amount. The results were compared with experiment, showing reasonable agreement. Through the analysis of V-die bending as well as draw bending of TRIP steel, the proposed scheme with variable elastic modulus was proven to well predict the deformation behavior of TRIP steel during bending and springback.