• 제목/요약/키워드: HPF (Hot Press Forming)

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유한요소해석을 이용한 열간프레스성형 적용 로어 컨트롤 암의 성형품질 조건 최적화 (Optimization of Conditions of Forming Quality for Hot-press-formed Lower Control Arm Using Finite Element Analysis)

  • 손현성;최병근
    • 한국자동차공학회논문집
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    • 제19권1호
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    • pp.45-50
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    • 2011
  • Hot-Press-Forming (HPF), an advanced sheet metal forming method using stamping at a high temperature of about $900^{\circ}C$ and quenching in an internally cooled die set, is one of the most successful forming process in producing crash-resistant parts such as pillars and bumpers with complex shape, ultrahigh strength, and minimum springback. To optimize conditions of a forming quality in HPF process and secure a safe product without any failures, such as fractures and wrinkling, the simulations based on the coupled thermo-mechanical analysis for a hot-press-formed lower control arm are applied with Taguchi's orthogonal array experiment. Three factor variables - the friction coefficient, blank shape, and hole location for burring - are selected to be optimized. The most effective condition of a forming quality for a hot-press-formed lower control arm is suggested. The simulation results are confirmed with experimental ones.

열간프레스성형에서의 기계적 물성 측정 (Measurement of Mechanical Properties for Hot Press Forming)

  • 안강환;유동훈;석동윤;김홍기;박성호;정관수
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2009년도 춘계학술대회 논문집
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    • pp.450-453
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    • 2009
  • In order to overcome drawbacks of the advanced high strength steel such as inferior formability and large springback, the hot press forming process(HPF) has been being applied for forming of automotive sheet parts. Good formability and dimensional accuracy without springback as well as good crash performance of final products are the advantages of the HPF process. In this work, a method to characterize the mechanical properties of the HPF steel was developed based on the simple tension test at high temperatures and its finite element analysis, while it was applied to obtain strain rate and temperature dependent flow curves of the HPF steel. The final flow curves were represented by utilizing the Johnson-Cook type equation both in uniform and post-uniform deformation regions.

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보론강판의 열간 벤딩 공정에서 성형인자가 기계성질에 미치는 영향 (The Effect of Forming Parameter on Mechanical Properties in Hot Bending Process of Boron Steel Sheet)

  • 권기영;신보성;강충길
    • 소성∙가공
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    • 제19권4호
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    • pp.203-209
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    • 2010
  • In the hot press forming process (HPF), a martensitic structure is obtained by controlling the cooling rate when cooling a boron sheet that is heated up to over $900^{\circ}C$. The HPF process has various advantages such as the improvement in formability and material properties and minimal spring back of the deformed materials. The factors related to the cooling rate depend on the heat transfer characteristics between heated materials and dies. Therefore, in this study, the cooling rate is controlled by adjusting the heat transfer coefficient of the material at the pressing process. And, the mechanical properties and microstructure of the deformed material is demonstrated during the HPF process where cold dies are used to form the heated steel plate. This is achieved by varying the major forming conditions that control the cooling rate regarded as the most important process parameter.

열-소성 연계 해석을 이용한 자동차 로어암 부품 개발 (Development of Automobile One-piece Lower-Arm Part by Thermo-Mechanical Coupled Analysis)

  • 손현성;김흥기;최병근;조열래
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2008년도 추계학술대회 논문집
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    • pp.218-221
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    • 2008
  • Hot Press Forming (HPF), an advanced sheet forming method in which a high strength part can be produced by forming at high temperature and rapid cooling in dies, is one of the most successful forming process in producing components with complex geometric shape, high strength and a minimum of springback. In order to obtain effectively and accurately numerical finite element simulations of the actual HPF process, the flow stress of a boron steel in the austenitic state at elevated temperatures has been investigated with Gleeble system. To evaluate the formability of the thermo- mechanical material characteristics in the HPF process, the FLDo defined at the lowest point in the forming limit diagrams of a boron steel has been investigated. In addition, the simulation results of thermo-mechanical coupled analysis of an automobile one-piece lower-arm part are compared with the experimental ones to confirm the validity of the proposed simulations.

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Al 도금 HPF 강판과 전기아연도금 TRIP 강판의 저항 점 용접 시 연속타점 전극의 수명에 미치는 도금층의 영향 (Effect of Coating Layer on Electrode Life for Resistance Spot Welding of Al-Coated Hpf and Zn-Coated Trip Steels)

  • 손종우;서종덕;김동철;박영도
    • Corrosion Science and Technology
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    • 제11권1호
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    • pp.29-36
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    • 2012
  • The resistance spot welding of high strength steel degrades the weldability because of its high strength with rich chemical composition and coating layer to protect from corrosion. During the each resistance welding process the electrodes tip reacts with coating layer, then subsequently deteriorates and shorten electrode life. In this study, the Al-coated HPF (Hot Press Forming) steels and Zn-coated TRIP steels were used to investigate the electrode life for resistance spot welding. Experimental results show that the reactivity of Al-coating on HPF steels to electrode tip surface behaviors different from the conventional Zn-coated high strength steels. The electrode tip diameter and nugget size in electrode life test of Al-coated HPF steels are observed to be constant with respect to weld numbers. For Al-coated HPF steels, the hard aluminum oxide layer being formed during high temperature heat treatment process reduces reactivity with copper electrode during the resistance welding process. Eventually, the electrode life in resistance spot welding of Al-coated HPF steels has the advantage over the galvanized steel sheets.

열간프레스성형에서의 변형 측정장치 개발 및 기계적 거동의 물성화 (Develop of Strain Measurement and Characterization of Mechanical Behavior for Hot Press Forming)

  • 유동훈;석동윤;김돈건;안강환;손현성;김교성;정관수
    • 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.

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상변태를 고려한 핫프레스포밍 공정의 유한요소해석 (FE Analysis of Hot Press Forming Process considering the Phase Transformation)

  • 강경필;이경훈
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2008년도 추계학술대회 논문집
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    • pp.226-229
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    • 2008
  • Hot press forming is an advanced forming technology fur manufacturing of complex and crash-resistant automotive parts using ultra high strength steels. The 3-dimensional FE analysis of hot press forming process, in which process the deformation, heat transfer and phase transformation behavior are fully coupled, is carried out. The vast amount of material properties for the FE analysis is obtained from material properties calculation software which is based on thermodynamic calculations. The overall methodology for the FE analysis of HPF process and the analysis results are discussed here.

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열유동 해석을 통한 핫프레스 포밍 금형의 냉각 성능 평가 (Evaluation of Cooling Capability of Hot Press Forming Die with Thermal CFD Simulation)

  • 이경훈;이재진;서창희
    • 소성∙가공
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    • 제25권4호
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    • pp.242-247
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    • 2016
  • CFD simulation with FlowVision® is used to evaluate the capability of cooling channel in hot press forming dies. Two different types of cooling channels, dry drilled and pocket types are considered for comparison. Two different approaches for simulating cooling channel are considered. One is single-phase velocity calculation for coolant only and the other is multiphase thermal and velocity calculation for die, blank and coolant all together. Both approaches show better cooling performance in pocket type cooling channel. Also both approaches show their own effectiveness in designing cooling channel of hot press forming dies.

HPF 적용을 위한 극저탄소강의 강도에 미치는 침탄 열처리의 영향 (Strength Change in Ultra Low Carbon Steel due to Carburizing Heat Treatment for Hot Press Forming)

  • 강수영
    • 대한금속재료학회지
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    • 제50권6호
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    • pp.433-438
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    • 2012
  • Strength change in ultra low carbon steel carburized at $880^{\circ}C$ and $930^{\circ}C$ for 10, 30, 60 and 120 minutes was investigated. The results were analyzed by a tensile test, chemical composition analysis, optical microscopy and scanning electron microscopy. Stress in the 0.5% strain specimen in the tensile test increased as the time treated at $880^{\circ}C$ and $930^{\circ}C$ increased, because the carbon diffusion layer and the martensite of the specimen increased with increasing treatment time. Martensite was found in the ferrite region in the specimen treated at $880^{\circ}C$, which is attributed to grain boundary diffusion.