• 소성∙가공
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• 제28권3호
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• pp.115-122
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• 2019

In this paper, finite element analysis of an automatic five-stage precision cold forging process of a yoke, a steering part of a passenger's car, is conducted with emphasis on spring back analysis at the yoke-forming stage and its experimental verification is subsequently made. An elastoplastic finite element method with MINI-element technique employed for the analysis of the entire process is explained. There is emphasis that the thin film of material formed between the punch and die in the stage may result to some errors especially in elastoplastic finite element analysis of spring back due to frequent remeshing. The numerical robustness of the spring back analysis in regards to remeshing is hence shown first through investigation into its effect on the predicted spring back. Experimental measurement of displacement due to spring back is carried out for comparison with the predicted results, and they are in a qualitative agreement with each other.

• 소성∙가공
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• 제5권2호
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• pp.115-121
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• 1996

Recently it is attempted to manufacture gears by various cold forging methods to meet requirements of mass production and uniform qualities. Compared to machined gears cold forged ears reveal higher tooth strength and better surface roughness but they reveal lower geometrical accuracies. Therefore in the present study a series of experiments are performed to investigate relations between geometrical accuracies of dies and billet and those of the final product. The geometrical accuracies of forged gears are considered through functional gear-element tolerances by measuring pitch error profile error lead error radial error tooth thickness and rolling test. Results of the experiments can be summarized as follows: (1) involute spur gears of KS 5(or AGMA7) accuracies can be made,(2) concentricity of die set should be maintained within 0.01mm (3) clearance between the billet and die set should be less than 0.1mm (4) con-centricity and radial runout should be less than 0.08mm and 0.1mm respectively. However it is thought that FEM analysis of elastic/thermal deformations of dies and the billet is necessary for a better understanding of the findings obtained through the present study.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.170-173
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• 2004

Recently many kinds of gears have been produced by forging in order to enhance the mechanical properties of the gears and the productivity of the process. Developments in forging technology are the reason for the increased usage. However, a critical problem of the forged gears is the dimensional change or distortion caused by elastic recovery after forging, and relief of the residual stresses during subsequent heat treatments. Distortion is of great concern to the manufacturers of precision parts, because it influences directly the dimensional accuracy and the grade of carburized bevel gears. In the present paper, distortion due to elastic and heat treatment of bevel gears Is investigated. Distortions of forged gears, machined gears and die aremeasured and compared. Numerical analysis is used to simulate the complete cold forged process and heat treatment process for the machined gears and shows good agreement with the experimental measurements.

• 한국정밀공학회지
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• 제13권4호
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• pp.43-52
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• 1996

This paper describes interactive computer procedures for design the forming sequences in cold forging. This system is implemented on the personal computer and its environment is a commercial AutoCAD system. The programming language. AutoLISP, was used for the configuration of the system. Since the process of metal forming can be considered as a transformation of geometry, treatment of the geometry of the part is a key in process planning. To recognize the part section geometry, the section entity representation, the section coordinate-redius representation and the section primitive geometru were adopted. This system includes six major modules such as input module, forging design module, forming sequence design module, die design module, FEM verification module and output module which are used independently or in all. The sequence drawing wigh all dimensions, which includes the dimensional tolerances and the proper sequence of operations, can generate under the environment of AutoCAD. The acceptable forming sequences can be verified further, using the FE simulation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.774-777
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• 2001

This paper describes a research work of developing a computer-aided design system of cold forging products. An approach to the system is based on the knowledge-based rules. Knowledge for the system is formulated from plastic theories, experimental results and the empirical knowledge of field experts. The system has been written in AutoCAD with a personal computer and is composed of six modules, which are selection of billet material, input of final product, process planning design, preform modification, insert design, shrink rings design module. Based on knowledge-based rules, the system is designed by considering several factors such as volume constancy, limite of formability by material, preform shape and so on.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.237-238
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• 2006

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.94-97
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• 1999

The study has been performed for the relation between die and product in closed die upsetting by the experiment. the strain of die has been given by the simple experiment using the strain gauge located at the outer surface of die and the deformation history of die and product has been given by the experiment and Lame's formula. the product with accurate dimension and shape can be obtained by analysing elastic deformation of die during upsetting process. The deformation of die during metal forming process has been given by the experiment and lame's formula. The product with accurate dimension and shape can be obtained by analysing elastic deformation of die during upsetting process. The deformation of die during metal forming process has been usually predicted by the experience of industrial engineers of finite element analysis. But it is difficult to predict the dimension of product at unloading and ejected states. The study has given useful result for the deformation history of die and product through the experiment and Lame's formula at closed die upsetting and can be applied in the die design for product with accurate dimension.

• 소성∙가공
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• 제18권2호
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• pp.150-155
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• 2009

A shaft for laser printers has to be produced with high dimensional accuracy of a few micrometers. Most companies produce the shaft, therefore, by machining. These days, forging process is tried to be employed in manufacturing the shaft for productivity. In this study, the dimensional inaccuracy of straightness is studied and the underfill is not focused because the shaft shape is simple and the load capacity of press is sufficient. The straightness and concentricity of the shaft is important for the operation of a laser printer. Many design parameters such as preform shapes, tooling dimensions, forging load, and billet geometries may affect on the dimensional accuracy. In the forging process of shafts, a billet which is cut from wires is used. The billet, therefore, may be a little bit curved but not always straight. The elastic recovery is considered to cause the dimensional inaccuracy. Therefore, the effect of the forging load on the elastic recovery and straightness is investigated through the finite element analyses using DEFORM-3D and ABAQUS.

• 소성∙가공
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• 제29권6호
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• pp.362-369
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• 2020

In this study, elastoplastic finite element analysis with multi-body treatment was used to elucidate the mechanical phenomena occurring from pre-stressing of die-system. A finite element analysis model with detailed conditions is proposed. The effects of die pre-stressing slope on the circumferential components of the pre-stressed die inserts were evaluated. The role of tight fitting between the supporter and die case was also emphasized because it has a significant effect on the undesirable change in the target slope of machined inner surface of the die case around the die insert. The two mechanical problems include the one between die-insert and die case and the other between supporter and die case, and their correlation is minimized to establish the optimum design in the die structural design stage because it cannot be quantitatively controlled owing to various factors affecting the die structural behavior during die pre-stressing.

• 한국정밀공학회지
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• 제21권7호
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• pp.153-162
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• 2004

This paper describes a research work on the die design for the deep drawing ＆ ironing(D.D.I.) of high pressure gas cylinder. D.D.I die set is large-sized die used in horizontal press, which is usually composed of drawing, and ironing die. Design method of D.D.I. die set is very different from those of conventional cold forging die set.. Out diameter of the die set is fixed because of press specification and out diameter of the insert should be as small as possible for saving cost of material. In this study, D.D.I die set has been designed to consider those characteristics and the feasibility of the designed die has been verified by FE-analysis. In addition, the automated system of die design has been developed in AutoCAD R14 by formulating the applied methods to the regular rules.