• Transactions of Materials Processing
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• v.9 no.4
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• pp.421-427
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• 2000

The present study has focused on the development of shear textures during groove pressing in an aluminum alloy sheet. The shear components 23 and 13 developed during the groove pressing process. The process consisting of two steps of grooving and flattening each effectively gave rise to a high shear deformation In the sheet without reduction in thickness. The main texture component obtained from the process was the rotated Bs-orientation. The evolution of shear components during the groove pressing caused an increase in R-value of aluminum sheet comparing to a normally processed rolled sheet.

• Journal of the Korean Wood Science and Technology
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• v.30 no.1
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• pp.25-33
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• 2002

Improvement of density profile and sound absorption capability of particleboard was attempted. Three types of hot pressing methods examined ; flat-platen pressing method (A-type pressing), hot pressing in forming box (B-type pressing), and hot pressing set up jagged caul in forming box (C-type pressing). The raw materials were larch(Larix leptolepis (S, et. Z.) Gorden) shavings, phenol formaldehyde resin, and the particleboard perforated with stair type. The physical and mechanical properties such as specific gravity, bending strength (MOR), internal bonding strength (IB) and sound absorption coefficients were examined. The results are summarized as follows : 1) The MOR and internal bonding strength of the board pressed in forming box were higher than those of flat-platen pressed board. 2) The minimum density to average density ratio in thickness direction which pressed in forming box showed about 923%, in the case of 35 mm commercial particleboard and 50 mm flat-platen pressed board, its values showed about 66.4% and 865% respectively. 3) Sound absorption coefficients of the particleboard perforated with stair type were higher than those of flat-plated pressed board and commercial particleboard.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.3061-3071
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• 2000

Densification behavior of titanium alloy powder was investigated under hot pressing at various pressures and temperatures. Experimental date were obtained for densification of titanium alloy powder under an instantaneous loading and subsequent creep deformation during hot pressing. The constitutive models of Fleck et al. and the modified Gurson were employed for thermo-phastic deformation under the instantaneous loading and that f Abouaf and co-workers for creep deformation of titanium alloy powder during hot pressing. By implementing these constitutive equations into a finite element program(ABAQUS), finite element results were compared with experimental data during hot pressing. To investigate the effect of friction between the power and die wall, density distributions of power compacts were measured and compared with finite element calculations. Finite element results from the models of Fleck et al. and the modified Gurson agreed reasonably good with experimental data for densification and density distribution of titanium alloy powder under the instantaneous loading during hot pressing. Finite element results from the model of Abouaf and co-workers, however, somewhat overestimate experimental data for creep deformation of power compacts during hot pressing.

• Journal of Sensor Science and Technology
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• v.27 no.4
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• pp.259-263
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• 2018

A radial artery pulse wave is measured while pressing an artery with constant force. However, pulse waveform measurements vary depending on pressing force and direction. Accurate pulse waveform measurements are important for analysis. Thus, it is necessary to define the measurement range of the permissible force and direction from which a correct pulse waveform is derived. In this study, pulse waves were generated by a pulse wave generator for accurate control. The pulse waves generated for different angles and pressing forces were analyzed. The augmentation index (AIx), which is the most commonly used index for evaluating vascular stiffness, was analyzed. The AIx was measured within ${\pm}6^{\circ}$ of the vessel direction and within ${\pm}8^{\circ}$ perpendicular to the vessel direction with a force that was 25% or more of the pressing force at which the maximum pressure wave was generated. We identified the applicable pressing force and angle range by analyzing the effect of pressing angle on the pulse wave. The AIx analysis performed using the pulse wave measurement device is reliable and reproducible.

• Journal of the Korean Ceramic Society
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• v.30 no.1
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• pp.62-68
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• 1993

Densification of alumina powder, grain size and fracture toughness of sintered body by hot pressing after cold compaction were investigated and compared to traditional hot pressing process (without cold cyclic compaction). To achieve a higher densification and to reduce the hot pressing time, hot pressing after cold cyclic compaction was more efficient compared to traditional hot pressing. This phenomenon resulted from the increment of packing densityby the acceleration fo rearrangement of powders under cold cyclic compaction. The grain size of sintered body was only dependent on relative density, and densification during hot pressing was governed by thelattice diffusion. Comprisons of grain size, densification mechanism and fracture toughness resulted from hot pressing after/without cold cyclic compaction showed that a low cyclic pressure may not effect on the fragmentation of alumina powders.

• Journal of Powder Materials
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• v.1 no.2
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• pp.159-166
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• 1994

The variation of the microstructures and the mechanical properties with varying vacuum hot pressing temperature and pressure was investigated in PyM processed 20 vol%) SiCw/ 2124Al composites. As increasing the vacuum hot pressing temperature, the aspect ratio of whiskers and density of composites increased due to the softening of 2124Al matrix with the increased amount of liquid phase. The tensile strength of composite increased with increasing vacuum hot pressing temperature up to $570^{\circ}C$ and became saturated above $570^{\circ}C$, To attain the high densification of composites above 99%, the vacuum hot pressing pressure was needed to be above 70 MPa. However, the higher vacuum hot pressing pressure above 70 MPa was not effective to increase the tensile strength due to the reduced aspect ratio of SiC whiskers from damage of whiskers during vacuum hot pressing. A phenomenological equation to predict the tensile strength of $SiC_w$/2124AI composite was proposed as a function including two microstructural parameters, i.e. density of composites and aspect ratio of whiskers. The tensile strength of $SiC_w$/2124AI were found more sensitive to the porosity than other P/M materials due to the higher stress concentration and reduced load transfer efficiency by the pores locating at whisker/matrix interfaces.

• Journal of Energy Engineering
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• v.1 no.1
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• pp.58-65
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• 1992

Pt loaded porous carbon Pt/C electrode was prepared by hot pressing process to enhance the electrode performance in PAFC (phosphoric acid fuel cell). By changing the hot pressing conditions and PTFE contents, Pt/C electrodes were prepared and the electrochemical characteristics of oxygen reduction and unit-cell performance were evaluated. The optimum condition of hot press to make electrode is 360$^{\circ}C$ and 10 kg/$\textrm{cm}^2$. Maximum performance was obtained at 30 wt% PTFE content in the catalyst layer with 80% utilization of platinum clusters. Unit-cell performance of hot pressed Pt/C electrode was 200 mA/$\textrm{cm}^2$ at 700 ㎷ and stable performance was maintained more than 200 hr.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.7
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• pp.1073-1080
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• 1997

The stage 1 compaction behavior of tool steel powder under die pressing was studied. The friction effects between the powder and the die wall under different die pressing modes were also investigated. The elastoplastic constitutive equations based on the yield functions by Fleck et al. and by Shima and Oyane were implemented into a finite element program to simulate die compaction processes. Finite element calculations were compared with experimental data for densification and density distribution of tool steel powder under single and double action die pressing. Finite element calculations using the yield function by Fleck et al. agreed better with experimental data than by Shima and Oyane.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1076-1086
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• 2003

The effect of a rubber mould on densification behavior of aluminum alloy powder was investigated under cold isostatic compaction. A thickness of rubber mould and friction effect between die wall and rubber mould were also studied. The hyperelastic constitutive equation based on the Ogden strain energy potential was employed to analyze deformation of rubber. The elastoplastic constitutive equation of Shima and Oyane and that of Lee on densification were implemented into a finite element program (ABAQUS) to simulate densification of metal powder for cold isostatic pressing and rubber isostatic pressing. Finite element results were compared with experimental data for densification and deformation of aluminum alloy powder under isostatic compaction.

• Transactions of Materials Processing
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• v.15 no.5 s.86
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• pp.382-386
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• 2006

Preform design is an effective means of achieving the homogeneous deformation of workpiece materials and decreased load in metal forming. However, this approach has not been applied to equal channel angula. pressing (ECAP). In this paper, plastic deformation behavior of workpieces having four different preform shapes during ECAP was investigated using finite element analyses. The results indicated that a preform design of the workpiece head has a beneficial effect on homogeneous deformation, reducing the maximum pressing load at the initial stage and eliminating folding defects at strain concentration points.