Papers by Author: Dong Won Jung

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Authors: Xue Wen Chen, Dong Won Jung, Ai Xue Sun
Abstract: Technology and die design are very important in the development of forging products due to its great influence on the quality, cost and manufacturing efficiency of the final products as well as the life of the forging die. In the environment of the severe competition, how to improve the quality of forging technology and die design, to reduce the product cost and ultimately to enhance competitiveness of the forging factory are the problems that forging technology and die designer have to solve. In order to improve the quality of forging technology and die design, a design optimization method based on approximate model (response surface model) and FEM technique for hot forging process is proposed in this paper. During design optimization process, finite element analysis is incorporated to calculate the objective function and check the design alternatives. Design of experiment (DOE) method is used to collect sample points and calculate the polynomial coefficients of response surface model, and approximate model is used to calculate the optimum search direction. Finally, a case study is conducted for a gear workpiece hot forging process. The objective function is the degree of uniformity of equivalent-strain, which can be defined as mean square deviation of the equivalent-strain in each element and the average equivalent-strain of all elements, and the design parameters are the initial H0/D0 ratio of billet and the key dimensions of the die. Then the design optimization mathematical model is established. The result shows that the objective function value is dropped from 0.7914 and converges at 0.4843 within 17 iterations, the optimal design parameters are obtained.
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Authors: Xue Wen Chen, Jun Wei Zhao, Dong Won Jung
Abstract: Flanging is a method of sheet metal forming process under combined compressive and tensile conditions using a punch and die to raise closed rims (flanges or collars) on pierced holes. For the flanging product used for the automotive steering part, the thickness of the bottom radius area is very important because of the crack usually occurred during the using process. But during conventional flanging process, the thickness of the rim and the bottom radius area were decreased seriously and make the hole flanging not strong enough to be used. In order to increase the thickness of bottom radius area of the flanging wall, a new method that combines flanging process and cold forging process was proposed in this paper and a special forming die set was designed with a stripper subjected to counter-pressure with an aim to obtain a more substantial flange. FEM software DEFORM 3D was employed to simulate these flanging part forming processes. The results showed the thickness of bottom radius area of the flanging wall was increased and a more substantial flange was obtained.
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