• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.8
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• pp.3638-3643
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• 2013

These days, workers in a construction site conduct a rebar bending process with a machine. This bending process has some problems such as long processing time and bad quality of the rebar. In order to manufacture a rebar having precision and machinability, we should study on Spring-back phenomenon. This phenomenon affects a shape of rebar after unloading due to restoration ability of material and it is influenced by bending angle, bending radius and a rebar diameter. The change of spring-back ratio according to the change of the parameters are analyzed by FEM. Consequently, Spring-back increases around $0.1^{\circ}$ as bending angle increases $10^{\circ}$. and it also increases around $0.6^{\circ}$ as diameter of rebar increases from ${\varphi}$ 10mm to ${\varphi}$ 16mm. while we can confirm that it decreases around $0.2^{\circ}$ as bending angle increases $10^{\circ}$.

• Journal of the Korea Convergence Society
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• v.13 no.4
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• pp.287-292
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• 2022

In this paper, the stochastic distribution of the springback amount is investigated for the stamping process of a U-channel shaped-product with ultra-high strength steel. Using the reliability-based design optimization technique (RBDO), stochastic distribution of process parameters is considered in the analysis including material properties and process variation. Quantification of the springback scatters is carried out with the statistical analysis method according to the material strength. It is found that the scattering amount of springback decreases while the amount of springback increases as the tensile strength of the blank material increases, which is investigated by analyzing the strain and stress distribution of the punch and die shoulder. It is noted that the proposed scheme is capable of predicting and responding to the unavoidable scattering of springback in the sheet metal forming process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.1
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• pp.7-14
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• 2011

Soft copper tube is one of the popular materials which are used for shipbuilding, automobiles, and freezing and HVAC equipment. However, these materials have problems that they cause occasionally outside wrinkle, spring back, wall thinning phenomena. In this study, to avoid these phenomena, was manufactured a mild materials devoted bending machine, which selected a bending method where the mandrel presses the pipe along with the sliding guide rail during bending process. During the course of confirming this performance, it was found that as the diameter of copper tube used for materials became smaller, the spring back phenomenon increased. And as the bending angle became larger, it became larger. In addition, we could manufacture mold products which scarcely generated wrinkle when bending copper tubes.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.6
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• pp.475-481
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• 2013

The residual stresses occur in the Frequency Selective Surface(FSS) embedded hybrid composite structures after co-curing due to mismatch among the coefficient of thermal expansions and stiffness values between the FSS and composite materials. The spring backs occur due to these residual stresses. Therefore, in this paper, the spring-backs caused by residual stresses in FSS embedded composite structures were studied with considering effect of symmetric and unsymmetric stacking sequence of composite laminates.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.3
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• pp.26-31
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• 1992

본 연구에서는 ABBAQUS/EXPLICIT CODE를 이용하여 자동차용 휠 디스크의 성형성을 파악하기 위한 모델링 방식과 컴퓨터 시뮬레이션의 결과인 스프링백, 잔류응력, 두께 변화, 변형률 등을 소개하기로 한다. 컴퓨터 시뮬레이션을 휠 디스크 스탬핑에 이용한 경우 스탬핑시 발생하는 여러현상을 쉽게 예측할 수 있으며, 또한 금형의 Geometry 결정 및 홀더와 펀치의 작용하중 등 금형 설계시 요구되는 데이타 확보가 매우 용이하다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.646-649
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• 1995

An experimental and analyical investigations were undertaken to improve understanding of spring-back phenomena of chopped fiber reinforced thermoplastic composite sheet. The materials tested contained 20, 35, 40 percent by weight of readomly oriented glass fiber in a prolypropylene matrix. The simple bending tests were performed at temperatures ranging form 75 .deg. c to 150 .deg. c with 25 .deg. c increment and at punch speed of 1mm/sec and 0.01mm/sec. The spring-back angel measured in pure bending is compared with the prediction base on the analytical model. Good agreement between experimental and predicted results was observed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.162-168
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• 2008

Recently surround molding parts using stainless steel are applied to international and domestic high grade vehicles, but there are great difficulties in die manufacture because of springback and twist after forming process. To solve this problem, finding the method of reduction springback is very important. In this study the springback which might happen during making a die that produce stainless steel surround molding parts is predicted and the geometry of die which satisfy the tolerance between product and panel after forming and springback will be suggested using automatic die compensation module.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.44-48
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• 1993

산업현장에서부터 실생활용품에 이르기까지 각종판재를 소재로하여 제작하는 가공품은 종류나 수가 매우 많다고 할수 있다. 이러한 제품들을 제작 하기 위해 여러단계의 성형 공정을 거치게 되며 원만한 성형공정 을 수행하기 위한 적절한 판재성형 제어방법으로써 다이곡률 반경의 변화나 블랭크홀딩가압정도의 부분적 변화로 드로잉률을 향상시키는 방법도 있으나 이보다 판재의 성형공정 제어방법에서 공구사이 상하에 비드 를 설치하여 판재를 성형할 경우 성형공정후 제품의 두께 분포가 비교적 균일해지고 드로잉의 마찰저항을 부분적으로 증가시키며 판재성형중 미끄럼 저항의 균형을 이루어 성형시킬 판소재가 절감도며 또한 성형중 주름을 억재하여 드로잉률을 향상시킨다. 다른 방법에 비해 비드는 설차가 간단해서 적절한 형상의 bead set을 선정하여 산업현장에서 실제 사용하고 있으며 또한 소재가 비드를 통과한후 탄성역에서 소성역으로 전환되기에 성형공정 이후 스프링백 현상으로인한 제품형상의 치수가 변하는 현상을 방지하는 효과도 기대할수 있다. 따라서 본 연구에서는 자동차용판재인 아연도금피막 강판으로 실험한 결과와 비드 이론식을 고찰해 보고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.450-455
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• 2017

A shield connector is an automotive electrical component that is used to connect electrical wiring in a vehicle. This part is made by progressive pressing using a phosphor bronze material with high electrical conductivity. The shape of the product is not complicated, but plastic forming techniques are required, such as deep drawing and bending, as well as shearing techniques such as piercing and notching. The finite element method was used to model the process. The strip layout design stage of the progressive die makes it possible to examine the thickness change, the stability of the forming process, and the spring-back. As a result of this analysis, it is possible to predict the correction values for the tendency of cracks, wrinkles, and incomplete plastic deformation, and to identify possible problems in advance. As a countermeasure against the forming error caused by the drawing process analysis, the drawing shape was modified and applied in the process design. For effective material utilization, a 3D strip layout was designed using an optimized blank shape based on nesting. The results improve the crack stability and spring-back of shield connector products produced through progressive pressing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.68-72
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• 1992

자동차 및 각종 판재 성형시 성형율을 향상시키는 방법에는 신소재 개발, 금형기술개발, 접촉부의 마찰을 줄여 주기 위한 윤활 등등이 있겠으나 손쉽게 공구다이 상하에 비드를 설치하여 판재를 성형할 경우 미끄럼 저항의 균형을 이루어 주름 억제와 두께분포가 보다 균일해지며 스프링백 현상 등으로 인한 성형 후 치수 불량 등을 주어 판재성형율을 향상시키는데 기여할 수 있다. 본 연구에서는 펀치가 판재를 성형하기 위해 진행됨에 따라 공구다이와 펀치간의 접촉각도가 변하게 되는 점을 고려하여 인출 각도변화에 따른 인출특성 및 마찰계수 변화등을 알아보고자 하며 원형 형태의 환저비드, 단일원형비드, 이중원형 비드의 종류와 크기변화 및 비드좌우 모서리 변화, 공구다이모서리변화, 블랭크가압력 변화, 비드 전진깊이 변화, 비드통 과 후 재료의 기계적 성질 변화등 인출 특성에 영향을 미치는 인자들을 변화시켜나가며 이에 따르는 인출특성을 Data Bank화 시켜 비드 종류나 형상에 따른 금형설계의 기초자료를 제공하고자 한다.