• 소성∙가공
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• 제22권6호
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• pp.328-333
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• 2013

The current study aims to determine the limit strains more accurately and reasonably when producing a forming limit curve (FLC) from experiments. The international standard ISO 12004-2 in its recent version (2008) states that the limit major strain should be determined by using the best-fit inverse second-order parabola through the experimental strain distribution. However, in cases where fracture does not occur at the center of the specimen, due to insufficient lubrication, the inverse parabola does not give a realistic fit because of its intrinsic symmetry in shape. In this study it is demonstrated that an inverse quartic function can give a much better fit than an inverse parabola in almost all FLC test samples showing asymmetric strain distributions. Using a quartic fit creates more reliable FLCs.

• 소성∙가공
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• 제26권3호
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• pp.144-149
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• 2017

In order to characterize the macroscopic mechanical response of ultra-thin (0.1 mm thick) ferritic stainless steel sheet at various loading paths, a crystal plasticity finite element method (CP-FEM) was introduced. The accuracy of the prediction results was validated by comparing with the experimental data. Based on the results, the forming limit diagram (FLD) was predicted using a modified Marchinicak-Kuczinski model coupled to a non-quadratic anisotropic yield function, namely, Yld2000-2d. The predicted FLD was found to be in good agreement with the experimental data.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 춘계학술대회 논문요약집
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• pp.82-82
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• 2004

우리나라는 신발 생산 특히 부품소재 부분에서 세계적인 경쟁력을 갖추고 있는 것으로 평가되고 있으며, 이 중 E.V.A midsole은 가볍고 충격흡수성 등과 같은 특성이 매우 우수하여 샌달의 midsole 부품으로 널리 사용되고 있지만 현재의 midsole 제조방식은 생산성의 한계에 직면하고 있다. 즉, 패턴 갑피(upper)와 Phylon mold를 각각 생산한 후 별도의 공정에서 두 제품을 접착하여 샌달을 만들기 때문에 두 제품을 따로 생산하므로 현재와 같은 방식의 제조에 의한 기존 방식의 샌달은 제작비용의 증가 및 생산성 저하 등의 여러 가지 문제점을 가지고 있어 보다 새로운 일체형 자동화 사출 mold에 의한 샌달 제조방식의 필요성이 절실한 실정에 있다.(중략)

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 춘계학술대회 논문집
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• pp.92-100
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• 1994

Forming limit diagrams for three different galvanized deep drawing quality steel sheets have been measured by hemispherical punch stretching. The experimental forming limit diagrams have been compared with results calculated using the shear instability criterion and the M-K model which takes into account a strain gradient effect resulting from bending (curvature) of a flat sheet by punch stretching. The measured data were in good agreement with the results calculated using exponent M value of 8 in Hosford's yield criterion for the M-K model and M= 6 for the shear instability model.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.195-198
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• 2009

In this study, in order to get the forming limit of AHSS sheet in the negative minor strain region, the shapes of die corner and drawbead are redesigned by employing the Taguchi's design of experiment method and the FEM forming simulation. With the redesigned FLD tool, the forming limit tests of automotive multi-phase(Dual Phase and Complex Phase) steel sheets which induce the normal fractures on the blank are performed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 춘계학술대회 논문집
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• pp.36-39
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• 2001

Tubular hydroforming has attracted increased attention in the automotive industry recently. In this study, a professional finite element program for analysis and design of tube hydroforming processes has been developed, called HydroFORM-3D, which is based on a rigid-plastic model. With the developed program several hydroforming processes such as a tee extrusion, an automotive rear axle housing and lower arm are analyzed and designed. And also, the Oyane's ductile fracture integral I was calculated from the histories of stress and strain according to every element and then the forming limit of the hydroforming process could be evaluated. The pediction of the bursting failure and the plastic deformation during typical hydroforming processes shows to be reasonable so that this approach can be extended to other various tube hydroforming processes.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2011년도 춘계학술대회
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• pp.263-265
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• 2011

우리나라 해역에서 선박의 대형화, 고속화와 선박교통량의 증가 및 항만과 해양개발 등으로 해상교통 환경은 급속하게 변화하고 있으며, 항로의 좌 우 측방 한계 표시, 항행위해요소의 표시 등의 용도로 사용되는 부표류는 항만, 연안해역 및 내륙수로에서 통항 선박의 안전을 위하여 그 수요가 점진적으로 늘어나고 있다. 변화하는 해양교통 환경에 능동적으로 대처하고 부표관리 업무의 효율성을 증대하기 위하여 경량화, 내부식성, 저비용 등 장점으로 정온도가 유지되는 항내나 내륙수로 등에서 국제적으로 항로표지용 부표로 이용되고 있는 플라스틱 부표의 국외 개발 동향, 제조 방법 및 시제품의 특성 평가를 통한 기술 향상 방안에 대하여 기술하였다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.90-94
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• 2002

In this paper, Compression in the case where dissimilar blocks are twinned variously are carried out in the condition of lubricated interface. The degree of growth is experimentally investigated. Moreover, numerical simulations are carried out by the elastic-plastic FEM for the case of the dissimilar blocks with the initial sawtooth angle of 60。. The dissimilar blocks are twinned, larger difference between material properties leads smaller growth, and the degreased interface leads smaller growth than that in the lubricated one. Furthermore, by the simulation of compression where dissimilar blocks are twinned, it is confirmed that the tendency of the general deformation pattern is very similar to the experiment.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2011년도 춘계학술대회 및 Fine pattern PCB 표면 처리 기술 워크샵
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• pp.207-207
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• 2011

The numerical simulation of the Forming Limit Diagram(FLD) test was carried out to calculate the limiting dome height(LDH: ISO12004-2) for aluminum alloy sheet Al6061-T6. The finite element analysis was used as an effective method for evaluating formability and diagnosing possible production problems in sheet stamping operations. To predict fracture during the stamping process, several failure models such as Cockcroft-Latham, Rice-Tracey, Brozzo and ESI-Wilkins-Kamoulakos(EWK) criteria were applied. The predicted results were discussed and compared with the experiments for Al6061-T6.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 제2회 박판성형심포지엄 논문집 박판성형기술의 현재와 미래
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• pp.74-82
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• 1998

The limit drawing ratio (LDR) is a major process parameter in the process design of deep drawing. If the actual drawing ratio is greater than the LDR for a particular stage, then an intermediate stage has to be added to the process sequence to avoid failure during the ratio. In this study, the optimal process design considering forming limit is performed for the first-drawing and redrawing by using finite element method combined with ductile fracture criterion. The LDR and the site of fracture initiation are predicted by means of the fracture criterion. From the results of finite element analysis, the optimal value of drawing ratio is obtained, which contributes to the more uniform distribution of thickness and the smaller values of the ductile fracture in final cup.