• 한국산학기술학회논문지
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• 제11권1호
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• pp.7-12
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• 2010

본 논문에서는 무 펀치 피어싱 공정 (기존 피어싱 공정에서 펀치 대신 유압을 사용)을 통해 형성된 구멍에서 내부에 수직 벽을 형성시키는 데 중요한 역할을 하는 공정 인자를 찾기 위한 최적화 해석을 수행하였다. 최적화 기법으로는 다꾸치법을 사용하였다. 또한 수직 벽 형성을 해석하는데 있어서는 연성파괴이론 중 하나인 Lemaitre 손상이론을 차용하였다. 최적화 해석 결과 수직벽 형성에 가장 큰 영향을 주는 인자로서 '다이의 모서리 반경'이 선정되었다.

• 한국산학기술학회논문지
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• 제10권5호
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• pp.929-934
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• 2009

본 논문에서는 고압의 유제론 펀치 대신 사용하는 무 펀치 피어싱공정을 통해 얇은 금속판에 거의 직벽을 가진 구멍을 내기 위한 방법으로 위, 아래 양 방향으로 교번적으로 고압을 거하는 피어싱공정을 제안하고 이를 기존 단 방향 피어싱공정 결과와 비교하였다. 연성파괴이론 중 하나인 Lemaitre 손상이론을 도입하여 두 방법에 따른 절단면의 모양을 수치적으로 얻은 후 이들 간의 차이를 나타내었다. 해석 결과, 양 방향에서 교번적으로 가압한 경우 수직도가 수직선 기준 $3.6^{\circ}$정도의 매우 작은 편차를 보여 단면 형상이 거의 수직으로 나타남을 알 수 있었다.

• 한국산학기술학회논문지
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• 제20권9호
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• pp.517-524
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• 2019

오버드라이버 허브클러치는 자동차 6단 자동 변속기 미션에 장착되어 엔진의 여유출력을 이용해 연료사용을 절감시켜주는 부품이다. 본 연구에서는 오버드라이버 허브클러치 제품에 대해 피어싱 공정 중 펀치에 가해지는 하중 및 소재 처짐량을 최소화 하고자 한다. 공정 중 펀치의 하중과 처짐량에 영향을 줄 수 있는 다이 클리어런스(die clearance)와 전단각도(shear angle) 그리고 마찰계수(friction coefficient)를 설계 변수로 설정했다. 또한 펀치의 하중과 소재 처짐량에 대해 각 설계 변수들의 영향도를 확인하기 위해 민감도 분석(sensitivity analysis)을 진행했다. 그 결과 전단 각도, 마찰 계수, 다이 클리어런스 순으로 하중 및 처짐량에 대해 민감한 것으로 조사되었다. 이를 통해 펀치의 하중과 소재 처짐량을 목적함수로 설정하고, 반응표면법(Response Surface Method)을 통해 각 설계 변수들과 목적함수의 방정식을 도출했다. 이를 통해 설정된 설계 변수들의 최적 값을 도출해 유한요소해석에 적용한 결과 펀치의 하중 및 소재의 처짐량이 기존대비 22.14% 개선됐다.

• 한국정밀공학회지
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• 제17권3호
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• pp.149-157
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• 2000

Tool wear in the shearing process such as blanking, piercing and trimming is very important, because it has great effects on the dimensional accuracy, working efficiency and economy. Most of tools in the shearing process have the coated layer at surface fur good wear and corrosion resistance. When the surface of tool is teated, the wear Phenomena of coated surface layer and inner layer may be different. This paper describes a computer modelling technique by the finite element method in order to investigate the wear mechanism and to predict the wear profile of Ti-N coated tool in piercing process according to the volume of Production. Wear coefficients of the coated layer and inner layer are obtained through Pin-on-Disk wear test, respectively. To verify the effectiveness of the suggested technique, the technique is applied to wear analysis in piercing recess of piston pin and simulation results are compared with experimental ones.

• Journal of Advanced Marine Engineering and Technology
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• 제36권6호
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• pp.802-807
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• 2012

SPR(Self-piercing rivet)은 판재 접합법으로서 스틸과 알루미늄 합금 등의 이종재료 접합에 사용되고 있다. 접합 공정은 피어싱을 포함한 소성변형이 함께 이루어진다. 프레스에서 펀치의 아래에 있는 리벳은 상부판재를 피어싱하고 하부 판재와 기계적으로 맞물리며 소성변형되어 결합된다. 본 논문에서는 SPR을 제작하기 위한 단조공정을 설계하였고, 이를 위하여 상용 유한요소해석 코드인 DEFORM-2D를 이용하여 해석하였다. 리벳 제작을 위한 단조공정의 설계에서 공정 순서, 성형성, 단조하중, 응력과 변형률 분포 등을 조사하였다. 또한 시뮬레이션 결과를 통하여 적합한 단조공정을 설계하였다. 설계된 공정은 업세팅, 헤드부 성형, 후방압출, 두 번째 챔퍼링의 네 단계로 구성된다. 그리고 단조공정에 대한 시뮬레이션 결과는 같은 조건을 적용한 실험 결과를 통하여 검증하였다.

• 한국정밀공학회지
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• 제10권2호
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• pp.114-125
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• 1993

In the present study the newly developed CAD/CAM system is applied to the process of the molding design, machining for mini-sized and precise processive die, and the production of press-stamped parts. When the design of a die was completed by means of CAD, wire cut NC data were generated with the aid of a design drawing in the CAD system and then inputed into the wire cut machine, and with the aid of a hole chart which had been made for this purpose, all the data were classified into the categories of CNC milling, jig boring, jig grinding, and machine center, and then developing a program of generating NC data, errors in process were reduced and programming time was shortened. The program was developed by using Autolisp language which was built-in the CAD, and realizing the intergation of designing a die, generating and processing NC data directly by a designer, designing time and machinery processing time were shorted. And the traditionally required working time for design. NC program required 6 days of work becomes 4 days of work by using the developed CAD/CAM system so that the efficiency shows 150% of the reduction working time. The prpgram of the design of the automation a progressive die mold was developed in the PC-Class Autocad system, therefore development expense could be reduced, and the integration of the CAD/CAM of the progressive die mold with the standard DB being built could be realized.

• Design & Manufacturing
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• 제15권4호
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• pp.51-56
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• 2021

Piercing is the process of shearing a circular hole in sheet metal, whose high shear force makes it difficult to secure the durability of tools. In addition, uneven clearance between tools due to poor alignment of the piercing punch causes accelerated die wear and breakage of the tool. This study reviewed the feasibility of in-situ determining alignment failure during the piercing process by analyzing the signal deviation of a bolt-type piezo sensor installed inside the tool whose alignment level was controlled. Finite element analysis was performed to select the optimal sensor location on the piercing tool for sensitive detection of process signals. A well-aligned piercing process results in uniform deformation in the circumferential direction, and shearing is completed at a stroke similar to the sheet thickness. Afterward, a sharp decrease in shear load is observed. The misaligned piecing punch leads to a gradual decrease in the load after the maximum shear load. This gradual decrease is due to the progressive shear deformation that proceeds in the circumferential direction after the initial crack occurs at the narrow clearance site. Therefore, analyzing the stroke at which the maximum shear load occurs and the load reduction rate after that could detect the misalignment of the piercing punch in real-time.

• Design & Manufacturing
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• 제16권3호
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• pp.28-33
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• 2022

The recent increasing application rate of advanced high-strength steel(AHSS) for automotive parts makes it difficult to ensure the durability of forming tools. Significant load and friction generated during the piercing process of AHSS increase the wear rate and the damage degree to dies. These harsh process conditions also yield product failures, such as dimensional inconsistency of pierced holes and insufficient quality of hole's sheared edge. This study analyzed the effect of punch wear on the sheared surface of pierced parts and the forming load during the piercing process. Wear-shaped punches showed approximately 20% higher piercing load than normal-shaped punches, and the rollover ratio of the sheared surface also increased. It is considered that the dull edge of wear-shaped punches does not penetrate directly into the material but shears after tensioning it in a piercing direction. In addition, wear-shaped punches experienced compressive load even after completing the piercing process during the down-stroke and tensile load during the up-stroke. This load variation is related to the smaller diameter piercing holes produced by wear-shaped punches compared to normal-shaped punches. Thus, we demonstrated the predictability of the wear level of dies through a comparative analysis of the piercing load pattern.

• 소성∙가공
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• 제26권5호
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• pp.271-276
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• 2017

A tee is the most common pipefitting used to combine or divide fluid flow. Tees can connect pipes of different diameters or change the direction of a pipe run. To manufacture tee type of stainless steel pipe, combinations of punch piercing and burr forming have been widely used in the industry. However, such method is considerably time consuming with regard to performing empirical work necessary to attain process conditions to prevent upper end tearing of the tee product and meet target tee height. Numerous experiments have shown that the piercing profile is the main cause of defects mentioned above. Furthermore, the mold design is formed through trial and error according to pipe diameters and changes in requirements. Thus, the objective of this study was to perform piercing and burring process analysis via finite element analysis using DYNAFORM to resolve problems mentioned above. An optimization design method was used to determine the piercing punch profile. Three radii of the piercing punch (i.e., large, small, and joined radii) were selected as design variables to minimize thinning of a tee pipe. Based on results of correlation and multiple regression analyses, we developed a predictive approximation model to satisfy requirements for both thickness reduction and target height. The new piercing punch profile was then applied to actual tee forming using the developed prediction equation. Model results were found to be in good agreement with experimental results.