• 한국산학기술학회논문지
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• 제10권12호
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• pp.3559-3566
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• 2009

종래에는 신발 부품 등을 제작하는데 주조금형을 가열, 냉각하는 별도의 가열판과 냉각판을 사용해 왔다. 그러나 이것은 금형을 가열 및 냉각하는데 시간이 너무 오래 걸리는 단점이 있었다. 따라서 본 연구에서는 기존의 가열판과 냉각판을 사용하던 방법을 대체하여 파이프 인서트 주조 금형을 사용한 신발창의 프레스 성형에 대한 적용 가능성을 제안하였다. 유한요소법을 사용한 수치해석이 금형의 온도분포 해석에 적용되었으며, 또한 LabView에 의해 그 온도를 실제로 측정하였다. 프레스 성형용 파이프 인서트 주조금형에 의해 부품을 제작하는 공정은 특히 생산성면에서 아주 효과적이라고 검증되었다.

• 한국자동차공학회논문집
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• 제18권2호
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• pp.61-66
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• 2010

A virtual manufacturing system that is composed of JMatPro, a material modeler and $DEFORM^{TM}$-HT, a finite element package is applied to the hot press forming process: high temperature material properties for each phase such as flow stress, elastic modulus, Poisson's ratio, thermal expansion coefficient, in addition to TTT curve are predicted by JMatPro and taken into $DEFORM^{TM}$-HT to predict the material behavior considering phase transformation and heat transfer simultaneously. In order to verify the accuracy of computation, the residual stress and the springback were compared with the experimental measurements. Both the predicted and measured principal residual stresses and amount of springback were in good agreement. It was also found that the residual stresses generated from hot press forming are not negligible as it has been generally assumed, although the springback deformation is quite small.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.257-260
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• 1997

The high precision of the products manufatured by press forming requires the high stiffness of press machines. In this study, the C-frame type press is analyzed to provide the basic idea on the C-frame press design, especially on the frame design. The finite element method is applied for the analysis and the isotropic propertics of the frame material is also considered. The results are summarized in terms of stresses and displacement distributions. Also, the openback angle of the presses is compared with two different models. The CS-150 and ECS-150 models, which are presses model having 150 ton frame capacity relatively and produced by SSangYong precision Co. LTD, are applied for the analysis.

• 한국산학기술학회논문지
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• 제1권2호
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• pp.21-26
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• 2000

플로포밍은 무절삭 점진성형공정으로 축 대칭 원형제품의 다품종 소량생산에 있어 스템핑이나 딥드로잉과 같은 박판성형 공정과 비교했을 때 매우 경제적이며 효율적인 공정이다. 본 연구에서는 기존 공정과의 품질비교를 통한 플로포밍 공정의 유용성 검토를 위해 현재 프레스 드로잉 공정으로 생산중인 자동차용 자동변속기 부품을 1-롤러 플로포밍 공정을 이용하여 대체 성형해 보았다. 실험결과 플로포밍 공정은 제조부품의 형상변화에 따른 설비변경 비용과 개발기간이 짧아 효과적인 유연 생산 시스템임을 알 수 있었다. 또한 플로포밍 공정을 프레스 드로잉 공정과 연계하여 성형하면 성형품의 정밀도와 생산성 향상에 매우 효과가 있음을 알 수 있었다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.198-201
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• 2009

As a way to improve the safety of automotives and to reduce the weight of vehicles, new forming technologies and advanced materials are in high demand in the automotive industry. However, the advanced strength steel has inferior formability and large springback. In order to overcome such drawbacks, the hot press forming process (HPF) has been being applied for forming of automotive sheet parts. In this work, new equipment was suggested to measure unlimited displacement range compared to previous one which was able to measure only up to 10mm displacement range. The external extensometer connected with grips by wire was applied to equipment so that total strain range was measured up to failure also in high temperature. And the finite element analysis was conducted to characterize the mechanical properties of the HPF steel. Finally, the flow curves were represented by utilizing the Johnson-Cook type equation both in uniform and post-uniform deformation regions.

• 소성∙가공
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• 제15권6호
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• pp.453-458
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• 2006

While the die casting has been mainly used to manufacture the magnesium alloy parts, the press forming is considered as an alternative to the die casting for saving the manufacturing cost and improving the structural strength of the magnesium alloy parts. Because the magnesium alloy has low formability at room temperature, forming at elevated temperatures is a necessary condition to obtain the required material flow for press forming. However, the elevated temperature forming does not always guarantee the sufficient formability under the dry friction condition because the surface damage such as scratch or wear may accelerate the material failure. In the present study, the solid-type lubricants such as PTFE, graphite and $MoS_2$ were tested for the square cup warm deep drawing using the magnesium alloy AZ31 sheet. The formability improvement by using the lubricant was examined by comparing the maximum deep drawing depth using the PTFE against no lubricant. The formability difference for the different lubricant was also examined based on the maximum deep drawing depth.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.152-157
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• 2009

Titanium alloy sheets have excellent specific strength and corrosion resistance as well as good performance at high temperature. Recently, titanium alloys are widely employed not only aerospace parts but also bio prothesis and motorcycle. But the database is insufficient of the titanium alloy for press forming process. In this study, the effect of temperature on the forming limit diagram was investigated for Ti-6Al-4V titanium alloy sheet through the Hocker's punch stretching test at elevated temperature. Experimental results obtained in this study can provide a database for development of press forming process at elevated temperature of Ti-6Al-4V titanium alloy sheet. From the experimental studies it can be concluded that the formability of Ti-6Al-4V titanium alloy sheet is governed by the ductile failure for the testing temperature below and vice versa neck-induced failure above the recrystalization temperature $0.5T_m$. The formability of Ti-6Al-4V titanium alloy sheet at $750^{\circ}C$ increases about 7 times compared with that at room temperature.

• 대한조선학회논문집
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• 제48권6호
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• pp.528-538
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• 2011

As a forming method for curved hull plates more efficient than the flame bending, mechanical bending using multi point press forming and die-less forming is discussed in this paper. the mechanical forming is a flexible manufacturing system for automatically forming of hull parts. It is especially suited to varied curved parts. This paper discusses a multiple point pressing machine composed of a pair of reconfigurable punches in order to achieve the rapid forming of curved hull plates using division forming and presents how forming information is obtained from the given design surface. Although the mechanical forming can be efficient in the metal forming, spring back after pressing is a phenomenon which must be carefully considered when quantifying the process variables. If the spring back is not accurately controlled, the fabricated shell plate cannot meet assembly tolerance. This paper describes the principles to calculate the proper stroke of each punch at the divided areas. the strokes are determined by an iterative process of sequential pressing and spring back compensation from an unfolded flat shape to its given design surface. FEA(finite element analysis) is used to simulate the spring back of the plate and the IDA(iterative displacement adjustment) method adjusts the offset of pressing punches from the deformation results and the design surface. The shape deviations of two surfaces due to spring back are compensated by integrated system using FEA and IDA method. For the practical application, It is aimed to develop an integrated system that can automatically perform the compensation process and calculate strokes of punches of the double sides' reconfigurable multiple-press machine and some experimental results obtained with mechanical bending are presented.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.162-169
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• 2004

In press forming of sheet metals, the material sheet is usually subjected to very large plastic strain under in-plane stressing. Moreover, the sheet also very often is subjected to out-of-plane compressive force between tools such as the upper and lower dies, the blank holder and the die, and so forth. In this paper, it is clearly demonstrated theoretically that out-of-plane stress may notably raise the forming limit strain and thus it can be effectively utilized to avoid earlier fracture of the sheet in press forming.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.353-356
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• 2008

Tool design is carried out for a press forming of a cross member in the rear suspension assembly based on the result of the finite element analysis. The analysis simulates the two-stage stamping process with the initial design and it fully reveals the unfavorable mechanism which develops inferiorities during forming. In this paper, a new design guideline is proposed to modify the process and tool shapes for a single-stage forming process. With the improved tool design, this study fabricates prototypes that satisfy the durability requirement.