• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2000년도 춘계학술대회논문집
• /
• pp.159-162
• /
• 2000

Wrinkles and shape distortions are generated during the forming of B-pillar(or center pillar) which is a component of the automobile side-frame. The stretch flanging modes at the joining part of the B-pillar and the roof-rail or the side-still give rise to forming problems when taior-welded blanks are applied to the side-frames. The authors simplified B-pillar lower part to T shaped section to investigate the forming behaviors. Three of die step locations and two of blank types were tested to show the effects of weld line locations and edge conditions on he forming of tailor welded blanks. The heights of body wrinkles and the strain distribution in the stretch flanged area were measured and compared.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2009년도 제7회 압연 심포지엄
• /
• pp.117-120
• /
• 2009

The rolling of flat slabs or sheet metal is probably the most advanced technique of metalworking technology. In spite of this very intensive activity, the problem if edge cracking has not been resolved. Although edge cracking is a major industrial problem, relatively little well-documented experimental work has been published on subject. Despite the paucity of exact experiments, it is reasonably certain from published data that three causes contribute to its occurrence; (1) limited ductility of the rolled material (2) uneven deformation at the edges and (3) variations in stresses along the width of the rolled material, particular near the edge. The present study was carried out to show the generation of edge cracking using ductile fracture criteria and FE-simulation. The validity of simulated results was verified by rolling experiments of steel strip.

• 한국정밀공학회지
• /
• 제23권2호
• /
• pp.81-87
• /
• 2006

This study has been focused on the analysis of high speed shear forming process for lead-acid battery grids. The grid plays an important role of electrical charge. It is necessary to ensure the best battery's performance that the grid should have a best quality. The clearance between punch and die, the velocity of punch and the critical damage value are very important parameters for making a good grid form. The finite element analysis of the shear forming process is carried out by measuring and optimizing these three important parameters. The result of this study concludes that these parameters has a great influence on grid quality.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1991년도 춘계학술대회 논문집
• /
• pp.251-255
• /
• 1991

The primary objectives of the rolling process are to reduce the cross section of the incoming material while improving its properties and to obtain the desired section at the exit from the rolls. Many engineering metals, suchas aluminium alloys, copper alloys, and steels are often cast intoingots and are then further processed byhot rolling into blooms, slabs, and billets, which are subsequently rolled into other products such as plate, sheet, tube, rod, bar, and structural shapes. In shape rolling a round or square bar is rolled in several passes into various shapes. During eachpass, the bar elongates as well as spreads. Thus, a very complex three-dimensional metal flow takes place. In this paper TASKS results for the simulation of a 7 pass square-to-round shape rolling are presented. The results are verified by comparing it with experimental results from a previous study conducted at the Battelle Columbus Labs

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2002년도 춘계학술대회 논문집
• /
• pp.121-124
• /
• 2002

This paper resents a virtual forming system to simulate deep drawing process for stress-strain information by utilizing virtual system designed using Virtual Reality Modeling Language (VRML) and computer aided analysis (CAE) tool. The CAE tool to calculate stress, strain, and deformation is designed using Finite Element Method. Stress distributions and deformation profiles as well as the operation of forming machine can be simulated and visualized in the web. The developed system consists of three modules, input module, virtual forming machine module, and output module. The input nodule was designed using HTML and ASP. The input data for FEM calculation is directed to the forming machine module for calculation. The results from the forming machine module can be visualized through output module as well as the forming process simulation.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.728-732
• /
• 2004

In the FE analysis of sheet metal forming, efficient results can be obtained by using shell elements rather than using solid elements. However, shell elements have some limitations to describe three-dimensional material laws. In the recent years, solid-shell element, which has only translational degree of freedom like solid element, has been presented. The assumed nature strain (ANS) and enhanced assumed strain (EAS) methods can be used to remove several solid-shell locking problems. In this paper, ANS method was used for diminish transverse shear locking and EAS method for thickness locking. Using the element, the steel pipe making process from flat plate analyzed effectively, which is including bending and welding.

• Advances in nano research
• /
• 제13권2호
• /
• pp.113-120
• /
• 2022

In this paper, a finite element (FE) simulation has been developed in order to examine the nonlinear stability of reinforced sandwich beams with graphene oxide powders (GOPs). In this regard, the nonlinear stability curves have been obtained asuming that the beam is under compressive loads leading to its buckling. The beam is considered to be a three-layered sandwich beam with metal core and GOP reinforced face sheets and it is rested on elastic substrate. Moreover, a higher-order refined beam theory has been considered to formulate the sandwich beam by employing the geometrically perfect and imperfect beam configurations. In the solving procedure, the utalized finite element simulation contains a novel beam element in which shear deformation has been included. The calculated stability curves of GOP-reinforced sandwich beams are shown to be dependent on different parameters such as GOP amount, face sheet thickness, geometrical imperfection and also center deflection.

• 소성∙가공
• /
• 제32권2호
• /
• pp.87-91
• /
• 2023

In the present work, the ductile fracture behaviors of ultra-high strength steel sheets along the different loading directions are investigated under various loading paths. Three loading paths, i.e., in-plane shear, uniaxial tension, plane strain tension deformations, are considered, and the corresponding specimens are described. The experiments are conducted using the digital image correlation (DIC) system to analyze the strain at the onset of the fracture. The experimental results show that the loading path for each specimen sample is linear, and different values of the fracture strains for the loading direction from the plane strain tension are observed. The ductile fracture model of the modified Mohr-Coulomb (MMC) is constructed based on the experimental data and evaluated along the rolling direction and transverse direction under various loading paths.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
• /
• pp.233-240
• /
• 1996

Analyses of the viscous and end effects on electromagnetic (EM) pumps of annular linear induction type for the sodium coolant circulation in Liquid Metal Fast Breeder Reactors have been carried out based on the MHD laminar flow analysis and the electromagnetic field theory. A one-dimensional MHD analysis for the liquid metal flowing through an annular channel has been performed on the basis of a simplified model of equivalent current sheets instead of three-phase currents in the discrete primary windings. The calculations show that the developed pressure difference resulted from electromagnetic and viscous forces in the liquid metal is expressed in terms of the slip, and that the viscous loss effects are negligible compared with electromagnetic driving forces except in the low-slip region where the pumps operate with very high flow velocities comparable with the synchronous velocity of the electromagnetic fields, which is not applicable to the practical EM pumps. A two-dimensional electromagnetic field analysis based on an equivalent current sheet model has found the vector potentials in closed form by means of the Fourier transform method. The resultant magnetic fields and driving forces exerted on the liquid metal reveal that the end effects due to finiteness of the pump length are formidable. In addition, a two-dimensional numerical analysis for vector potentials has been performed by the SOR iterative method on a realistic EM pump model with discretely-distributed currents in the primary windings. The numerical computations for the distributions of magnetic fields and developed pressure differences along the pump axial length also show considerable end effects at both inlet and outlet ends, especially at high flow velocities. Calculations of each magnetic force contribution indicate that the end effects are originated from the magnetic force caused by the induced current ( u x B ) generated by the liquid metal movement across the magnetic field rather than the one (E) produced by externally applied magnetic fields by three-phase winding currents. It is concluded that since the influences of the end effects in addition to viscous losses are extensive particularly in high-velocity operations of the EM pumps, it is necessary to find ways to suppress them, such as proper selection of the pump parameters and compensation of the end effects.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2010년도 하계학술대회 논문집
• /
• pp.56-56
• /
• 2010

Single-walled carbon nanotubes (SWCNTs) have attracted much attention as a promising material for transparent conducting films (TCFs), due to their superior electrical conductivity, high mechanical strength, and complete flexibility as well as their one-dimensional morphological features of extremely high length-to-diameter ratios. This study investigated three kinds of SWCNTs with different purities: as-produced SWCNTs (AP-SWCNTs), thermally purified SWCNTs (TH-SWCNTs), thermally and acid purified SWCNTs (TA-SWCNTs). The purity of each SWCNT sample was assessed by considering absorption peaks in the semiconducting ($S_{22}$) and metallic ($M_{11}$) tubes with UV-Vis NIR spectroscopy and a metal content with thermogravimetric analysis (TGA). The purity increased as proceeding the purification stages from the AP-SWCNTs through the thermal purification to the acid purification. The samples containing different contents of SWCNTs were dispersed in water using sodium dodecyl benzensulfate (SDBS). Aqueous suspensions of different purities of SWCNTs were prepared to have similar absorbances in UV-Vis absorption measurements so that one can make the TCFs possess similar optical transmittances irrespective of the SWCNT purity. Transparent conductive SWCNT networks were formed by spraying an SWCNT suspension onto a poly(ethyleneterephthalate) (PET) substrate. As expected, the TCFs fabricated with AP-SWCNTs showed very high sheet resistances. Interestingly, the TH-SWCNTs gave lower sheet resistances to the TFCs than the TA-SWCNTs although the latter was of higher purity in the SWCNT content than the former. The TA-SWCNTs would be shortened in length and be more bundled by the acid purification, relative to the TH-SWCNTs. For both purified (TH, TA) samples, the subsequent nitric acid ($HNO_3$) treatment greatly lowered the sheet resistances of the TCFs, but almost eliminated the difference of sheet resistances between them. This seems to be because the electrical conductivity increased not only due to further removal of surfactants but also due to p-type doping upon the acid treatment. The doping effect was likely to overwhelm the effect of surfactant removal. Although the nitric acid treatment resulted in the similar. electrical properties to the two samples, the TCFs of TH-SWCNTs showed much lower sheet resistances than those of the TA-SWCNTs prior to the acid treatment.