• 한국결정성장학회지
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• 제33권6호
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• pp.216-225
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• 2023

본 연구에서는 냉간 헤딩 공정에서 성형하중과 펀치 금형의 마모 감소를 통한 펀치 수명 증대를 위해 헤딩용 펀치 형상 최적설계를 수행하였다. 기존 생산에 사용되는 냉간 헤딩 펀치와 성형공정에 대한 유한요소해석 시뮬레이션을 통해 성형하중과 유동 특성 분석, 펀치금형에 집중되는 유효응력 및 마모량에 대하여 분석하였으며, 이를 통해 금형 마모와 밀접한 주요 설계인자를 확인하였다. 펀치금형의 최적설계 변수로서는 펀치 금형 포인트각(Point angle), 에지 반경값(Corner radius), 펀치소재재종(die material type), 마찰계수(friction coefficient) 등의 4가지 변수를 대상으로 4인자 3수준 인자 및 변수 수준을 설정하고, 성형해석 시뮬레이션과 다구찌법을 활용하여 설계인자별 영향도를 분석하여 최적의 최적설계 인자를 결정하였다. 본 연구를 통해 얻어진 최적설계변수를 적용하여 냉간 헤딩용 펀치 최적설계 시뮬레이션 결과, 각 펀치에 발생하는 최대유효응력은 최대 8.9 % 감소 효과를, 최대 펀치 마모 깊이는 37 % 감소 효과를, 성형하중은 평균 20% 수준 의 감소효과를 얻을 수 있었다. 현재, 소성 성형제품군이 적용되는 자동차, 건설 플랜트사에서 요구되는 고품질에 대응하면서도 적정 제조원가 절감을 위한 성형성 개선을 위한 성형공정개발 및 금형설계의 최적화가 지속적으로 필요하며, 향후 연구 결과를 현업에 적용하여 제품 성형성 개선 및 금형수명 증대 관리를 위한 기술자료로 활용하고자 한다.

• 열처리공학회지
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• 제17권4호
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• pp.211-215
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• 2004

Conventional spheroidization process of cold heading quality steels requires long heat treatment time, and reduction of the heat treatment time is important for improving productivity in the industry. Recently, hot deformation method has been proposed as a means of increasing spherodization kinetics. In this study, the influences of hot deformation on the spherodization behavior of cold heading quality steels were investigated. Hot deformation at the temperature range of $700^{\circ}C$ significantly enhances the spheroidization kinetics. Hot deformation can lead to a substantial reduction of spherodization process time as low as 1~5 hrs.

• 수산해양기술연구
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• 제30권1호
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• pp.53-63
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• 1994

1) 강소성 유한 요소법 프로그램 RDHPSC는 2단헤딩 가공에 있어서의 신뢰 할 수 있는 해석수단이다. 2) RDHPSC에 의한 2단헤딩의 해석은 2단헤딩가공에서의 최적 가공 조건의 결정에 유용한 정보를 제공할 수 있다. 3) 2단헤딩 가공중의 금속흐름을 수치해석에서의 격자 변형에 의해 관찰될 수 있다. 4) 2단헤딩 가공중의 표면 결함의 발생가능성은 수치해석 결과에서 원수방향응력과 계수 D를 관찰함으로서 탐색되어질 수 있다. 5) 2단헤딩가공중에 있어서의 내부결함 발생가능성은 수치해석의 격차 변형을 통하여 알 수 있다. 6) 마무리 가공금형 수명에 대한 최적가공조건은 수치해석에서의 접촉압력을 조사하여 얻을 수 있다.(이 논문의 결론부분임)

• 소성∙가공
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• 제20권1호
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• pp.48-53
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• 2011

Fasteners are used to join the various electronic products and machines. So, the quality and reliability of the fastener are strongly requested. In this study, the analyses of the multi-stage cold forging of TORX screws for storage parts are carried out. In manufacturing of TORX screws, crack and folding defects are observed. Therefore, the analysis is focused on the prediction of the defects. Based on the analysis results, the upper die and process conditions are redesigned to reduce the defects. The upper die shape for preform forming is redesigned to prevent folding and sharp shape change. The Cockroft-Latham damage criterion is introduced to predict the crack initiation. Analysis results shows that the maximum Cockroft-Latham damage value is decreased by 40% in the forming using the modified upper die.

• 소성∙가공
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• 제16권1호
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• pp.67-74
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• 2007

This study is aimed to find out the optimal forming conditions by comparing and analyzing material flow, deformation pattern, and a forming load through rigid-plastic FEM for a flange using pipe. Flanges are widely used for various purposes as connectors of industrial steel pipes which are manufactured by drawing process. The forming feature of flange was reviewed through both heading process and radial extrusion process in a cold working condition. As a result of simulation, the shape of flange can not be made by heading process, but made by radial extrusion process. The effects of design factors, such as gap-height, die-comer radius, and frictional factors on maximum forming load and deformation pattern are investigated for radial extrusion process.

• 소성∙가공
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• 제17권3호
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• pp.155-160
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• 2008

We analyzed a sequence of multi-stage automatic cold forging processes composed of four axisymmetric processes followed by a non-axisymmetric process using rigid-plastic finite element based forging simulators. The forging sequence selected for an example involves a piercing process and a heading process accompanying folding or overlapping, which all make it difficult to simulate the processes. To reduce computational time and to enhance the solution reliability, only the non-symmetric process was analyzed by the three-dimensional approach after the axisymmetric processes were analyzed by the two-dimensional approach. It has been emphsized that this capability is very helpful in simulating the multi-stage automatic forging processes which are next to axisymmetric or involve several axisymmetric processes.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 추계학술대회 논문집
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• pp.141-148
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• 1994

In order to improve the productivity of cold forging at low production cost, an integrated system's approach is necessary in handling the material preparation and the optimum process design, considering the forming machines, tooling, and operation including quality control. As the first step toward this approach, an expert system for multi-stage cold forging process design for fasteners with various head geometries is developed using Prolog language on IBM 486 PC. For effective representation of the complex part geometries, the system uses the multiple element input, and the forward inference scheme in determination of the initial billet size and intermediate forging steps. In order to determine intermediate steps, the basic empirical rules for extrusion, heading, and trimming were applied. The required forming loads and global strain distributions at each forging step were calculated and displayed on the PC monitor. The designed process sequence drawing can be obtained by AutoCAD. The developed system will be useful in reducing trial and error of design engineers in determining the diameter and height of the initial cylindrical billet from the final product geometry and the intermediate necessary sequences.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.195-200
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• 2007

We analyzed a sequence of multi-stage automatic cold forging processes composed of four axisymmetric processes followed by a non-axisymmetric process using rigid-plastic finite element based forging simulators. The forging sequence selected for an example involves a piercing process and a heading process accompanying folding or overlapping, which all make it difficult to simulate the processes. To reduce computational time and to enhance the solution reliability, only the non-symmetric process was analyzed by the three-dimensional approach after the axisymmetric processes were analyzed by the two-dimensional approach. It has been emphsized that this capability is very helpful in simulating the multi-stage automatic forging processes which are next to axisymmetric.

• 소성∙가공
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• 제15권8호
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• pp.562-567
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• 2006

Micro-alloyed steel or heat-treatment-free used in clean technology have been replacing for conventional quenched-and-tempered structural steels since the micro-alloyed forging steel was developed in early 1970s in Germany for saving money of heat treatment, simplified process, short delivery and good productivity. In this paper, ball stud assembled in steering system for automobile was selected to compare conventional process making heat treatment with new process using high strength micro-alloyed steel without heat treatment. The conventional process for ball stud was composed of a total of 6 steps including upsetting, forward extrusion, machining, burnishing and tread rolling with heat treatment and shot blasting. As opposed to conventional process, newly proposed process for ball stud using the clean technology without heat treatment is simplified such as forward extrusion, heading, upsetting, forming having a flange shape and tread rolling. Also net shape forming process to achieve specified process not to include machined step fur manufacturing the ball stud was applied to newly simplified process since micro-alloyed steel is difficult to be formed.

• 오토저널
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• 제16권1호
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• pp.31-41
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• 1994

1. 가공성 평가실험 및 평가기술. 1.1 가공성 평가시험법. 1.2 실험방법. 1.3 피단한계. 1.4 파단발생 평가이론. 1.5 파단평가이론의 적용. Bulk재 소성가공 공정중에 있어서 거시적 가공성평가 방법 및 응용방법에 대하여 논하였다. Bolt Heading 가공과 같은 냉간압조 가공에 있어서 상기 모델들에 의한 재료고유의 가공한계선과 변형경로를 비교하므로써 가공성을 평가할 수 있으며 또한 보다 복잡한 형상제품의 최적가공을 위한 가공조건 및 재질선정의 최적화에도 유용하게 이용될 수 있다.