Evaluation and Prediction of Forming Limit of Boron (22MnB5) sheet metal in a Hot Press Forming Process

아루무감(Arumugam S),홍성훈(S. H. Hong),뚜안(D. T. Nguyen),마니반난(Manivannan R),김영석(Y. S. Kim) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.5

At presence the industrial practice demands a reliable determination of forming limits which assures the prediction of properly selecting the forming process in a digital environment. Therefore, technological limits defined with the forming limit diagrams (FLDs) have to be known. The experimental evaluation of FLDs for sheet metal is time consuming and demands expensive equipment. Hot press forming (HPF) is an advanced sheet metal forming methodology which can able to produce high strength final product by forming the part with high temperature and also cooling the part rapidly inside dies, it’s an one of the most successful forming process which can produce a component with complex geometric shape, high strength and minimum spring back. For conventional sheet metal forming processes the forming limit diagram (FLD) is primarily applied as failure criterion in the automotive industry regarding a FE-based process design. This works deals with the prediction of formability of sheet metal during the hot press forming. In order to predict the FLD at high temperature, we used Marciniak-Kuczynski flat punch for equi-biaxial and round punch for uniaxial and plane strain for In-plane deformation test. However, thermo-mechanical coupled simulation carried out by using DEFORM-3D for forming and predicting the failure by using Normalized Cockcroft-Latham failure criterion model. By applying the above failure criteria in DEFORM-3D FLD simulation, we need to determine the critical damage values (C?) calculated from out of plane deformation test for uniaxial and plane strain experiments carried out at 25℃ (RT), 500℃ and 700℃. In addition, the formability of the simulation results in a hot press formed part is compared with the experimental ones to confirm the validity of the proposed simulations.

블래더 프레스 성형 시스템 개발 연구

유창용,김봉환,안국찬,김문경 한국기계기술학회 2015 한국기계기술학회지 Vol.17 No.2

In this paper, research development about a bladder press forming system has been carried out for sheet metal forming. The bladder press forming system consists largely of three units as follows forming process unit, driving unit and hydraulic power unit including bladder. Structural analysis of frame of total system by the ANSYS program, flow analysis of bladder by CFX version 14 and hydraulic circuit analysis by AMESim were carried for basic design of bladder press forming system. We can get a good forming results from bladder press system. Developed bladder press forming system will be largely used in aircraft manufacturing industry field.

블래더 프레스 성형 시스템 개발 연구

유창용,김봉환,안국찬,김문경 한국기계기술학회 2015 한국기계기술학회지 Vol.17 No.2

In this paper, research development about a bladder press forming system has been carried out for sheet metal forming. The bladder press forming system consists largely of three units as follows forming process unit, driving unit and hydraulic power unit including bladder. Structural analysis of frame of total system by the ANSYS program, flow analysis of bladder by CFX version 14 and hydraulic circuit analysis by AMESim were carried for basic design of bladder press forming system. We can get a good forming results from bladder press system. Developed bladder press forming system will be largely used in aircraft manufacturing industry field.

핫 프레스 포밍을 위한 고열전도성 금형에 대한 연구

금종원(Jongwon Kum),박옥조(Okjo Park),홍석무(Seokmoo Hong) 한국기계가공학회 2016 한국기계가공학회지 Vol.15 No.3

Due to the need for advanced technologies in the automotive industry, the demand for lighter and safer vehicles has increased. Even though various nonferrous metals, like Aluminum, Magnesium and also Carbon Fiber Reinforced Plastic (CFRP), have been implemented in the automotive industry, a lot of technical research and development is still focused on ferrous metals. In particular, the market volume of High Strength Steel (HSS) parts and Ultra High Strength Steel (UHSS) by hot press forming parts has expanded significantly in all countries’ automotive industries. A new tool steel, High Thermal-Conductivity Tool Steel (HTCS), for stamping punches and dies has been developed and introduced by Rovalma Company (Spain), and it is able to support better productivity and quality during hot press forming. The HTCS punches and dies could help to reduce cycle time due to their high thermal conductivity, one of the major factors in hot press forming operation. In this study, test dies were manufactured in order to verify the high thermal conductivity of HTCS material compared to SKD6. In addition, thermal deformation was inspected after the heating and cooling process of hot press forming. After heating and cooling, the test dies were measured by a 3D scanner and compared with the original geometry. The results showed that the thermal deformation and distortion were very small even though the cooling time was reduced by 2 seconds.

선박 외판 성형에서 목적 형상과 전개 평판의 최적 정합을 위한 ICP(Iterative Closest Point) 알고리즘 적용

이장현(Jang Hyun Lee),윤종성(Jong Sung Yoon),류철호(Cheolho Ryu),이황범(Hwang Beom Lee) (사)한국CDE학회 2009 한국CDE학회 논문집 Vol.14 No.2

Generally, curved surfaces of ship hull are deformed by flame bending (line heating), multi-press forming, and die-less forming method. The forming methods generate the required in-plane/bending strain or displacement on the flat plate to make the curved surface. Multi-press forming imposes the forced displacements on the flat plate by controlling the position of each pressing points based upon the shape difference between the unfolded flat plate and the curved object shape. The flat plate has been obtained from the unfolding system that is independent of the ship CAD. Apparently, the curved surface and the unfolded-flat surface are expressed by different coordinate systems. Therefore, one of the issues is to find a registration of the unfolded surface and the curved shape for the purpose of minimum amount of forming works by comparing the two surfaces. This paper presents an efficient algorithm to get an optimized registration of two different surfaces in the multi-press forming of ship hull plate forming. The algorithm is based upon the ICP (Iterative Closest Point) algorithm. The algorithm consists of two iterative procedures including a transformation matrix and the closest points to minimize the distance between the unfolded surface and curved surfaces. Thereby the algorithm allows the minimized forming works in ship-hull forming.

다점 프레스를 이용한 곡면 성형의 가공 정보 산출을 위한 IDA 방법

윤종성(JONG-SUNG YOON),이장현(JANG-HYUN LEE),유철호(CHEOL-HO RYU),황세윤(SE-YUN HWANG),이황범(HWANG-BEOM LEE) 한국해양공학회 2008 韓國海洋工學會誌 Vol.22 No.6

Flame bending has been extensively used in the shipbuilding industry for hull plate forming. In flame bending, it is difficult to obtain the desired shape because the residual deformation dependson the complex temperature distribution and the thermal plastic strain. Mechanical bending such as reconfigurable press forming, multi-point press forming or die-less forming has been found to improve the automation of hull plateforming because it can more accurately control the desired shape than line heating. Multi-point forming is a process in which external forces are used to form metal work-pieces. Therefore it can be a flexible and efficient forming technique. This paper presents an optimal approach to determining the press-stroke for multi-point press forming of curved shapes. Air integrated configuration of Finite element analysis (FEA) and spring-back compensation algorithm is developed to calculate tile strokes of the multi-point press. Not only spring-back is modeled by elastic plastic shell elements but also an iterative algorithm to compensate the spring-back is applied to adjust the amount of pressing stroke. An iterative displacement adjustment (IDA) method is applied by integration of the FEA procedure and the spring-back compensation work. Shape deviation between the desired surface and deformed plate is minimized by the IDA algorithm.

마그네슘 AZ31재를 이용한 차체부품 개발

윤태욱(Taewook Yoon),김래형(Raehyug Kim),이문용(Moonyong Lee),이규현(Gyuhyun Lee) 한국자동차공학회 2012 한국자동차공학회 지부 학술대회 논문집 Vol.2012 No.11

This study indicated that development of car body part in using Mg AZ31. Although Mg alloy (AZ31) which consist of HCP structure is hard to form in room temperature, it can be formed in warm temperature more than 200℃. The reason why it can improve forming ability in warm temperature is that non basal slip is activated. Car body part is made up warm press forming die with system of improved non basal slip. Before development of warm press forming system, warm forming die is designed and made up FLD TEST with FLC curve, warm forming analysis with the decrease rate of the thickness. Throughout a various process parameters such as blank temperature in 250℃, forming speed 10mm/sec and BHF 1ton so on, the optimized process condition and the design specification result in. Throughout the result of this study, the development technology of car body part is considered.

프레스 퀜칭 유한요소 해석에 의한 자동차용 드라이브 플레이트 제조 공정 최적화

이명규(M.G. Lee),김성준(S-J. Kim),곽은정(E.J. Kwak),강경필(G.P. Kang) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.5

본 연구에서는 프레스 퀜칭 공정에서 고려되어야 하는 여러 공정 변수 중 하중, 냉각채널의 크기, 위치 및 개수, 냉각 시간이 성형 및 냉각공정 후 부품의 성능에 미치는 영향을 유한요소 해석을 통하여 알아보았다. 공정변수 이외에도 특히 상변태 시에 발생하는 소성변형이 부품의 치수변화에 미치는 영향에 대한 해석을 제공하였다. 열역학 및 상변태에 기반한 유한요소 해석결과 본 연구에서 선택한 자동차 부품인 드라이브 플레이트의 경우 벤딩 부위에서 접촉이 우선적으로 나타나고 이에 따라 마르텐사이트의 변태가 다른 지점보다 먼저 시작되어 이때 발생하는 체적변화가 다른 부위의 접촉 양상을 불량하게 만들 수 있다는 것이 발견되었다. 또한, 변태소성변형이 냉각 후 잔류응력을 감소시켜 스프링백 값을 낮춤을 확인하였다. 비록 단순한 형태의 부품에 대한 해석을 수행하였지만, 본 연구 결과는 향후 복잡한 제품의 프레스 퀜칭 해석 시 유용한 정보를 제공할 수 있을 것이다. Finite element (FE) simulation based on thermo-mechanical constitutive equations is introduced to study the effect of various parameters on properties of final hot press formed product. The FE analysis considers the phase transformations occurring during the hot forming and subsequent quenching. The thermo-mechanical parameters are obtained from the commercial software JMatPro® with calibration by published data. The model part is the drive plate which is installed in the automotive transmission and delivers a torque to an engine and the sheet material is typical boron added steel for the hot press forming. Several process parameters including punch load, location, number and size of cooling channels and quenching time are chosen to investigate how the final part satisfies the manufacturer"s specifications such as hardness (or higher volume fraction of martensite) and flatness (lower springback). Besides the process parameters, the effect of phase transformation plasticity is also analyzed especially on the springback after hot press forming.

Dual-phase hot-press forming alloy

Yi, H.L.,Ghosh, S.,Bhadeshia, H.K.D.H. Elsevier Sequoia 2010 Materials science & engineering. properties, micro Vol.527 No.18

Hot-press forming steels are formed in a fully austenitic state followed by die-quenching in order to generate martensite and achieve strong steel. The ductility however, tends to be limited. We explore in this work a novel steel design in which the forming operation is in the two-phase austenite and ferrite field, so that the quenching results in a dual-phase ferrite and martensite microstructure at ambient temperature. It is demonstrated that better properties are achieved. The interpretation of the mechanisms of deformation during tensile testing indicates that the ductility can be further enhanced without compromising strength. The new steel also can be heated to temperature which is lower than that used for conventional hot-press forming steels, before transfer into the forming press.

FE Analysis of Forming Limit Diagram of 22MnB5 Sheet Using Fracture Energy Theory

Dae Young Ahn,Ok Dong Lim,Min-Sik Lee 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.10

A forming limit diagram (FLD) is used to define the strain limit of a material fracture during sheet formation. Owing to its usefulness in the FE analysis of hot stamping, numerous studies have been conducted regarding the FLD based on temperature. There have been few studies on the forming limit of martensite, which must be investigated to measure the impact characteristics and impact toughness to evaluate the safety of car components. Moreover, the need for FLDs of hot press products to evaluate the collision characteristics of automobile parts is increasing. In this study, a stretch test is performed to measure the forming limit of 22MnB5 steel before and after hot press forming. To minimize the error between the experimental data and FE simulation, fracture energy theory was applied to the damage evolution technique to enhance the accuracy of the fracture results. Accordingly, an FE analysis of the FLD was performed using the ABAQUS software, and the method for minimizing the error compared to the actual data of FLD is examined. The results were validated between an experiment and FE analysis by applying forming limit analysis data to the FE analysis of the tensile test.