• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.6
• /
• pp.74-79
• /
• 2004

The effects of change in injection pressure on spray structure have been investigated in high temperature and pressure field. To analyze the structure of evaporative diesel spray is important in speculation of mixture formation process. Also emissions of diesel engines can be controlled by the analyzed results. Therefore, this study examines the evaporating spray structure by using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 72 MPa to 112 MPa with a high pressure injection system(ECD-U2). The PIV(Particle Image Velocimetry) technique was used to capture flow variation of the evaporative diesel spray. A study on the mixture formation process of diesel spray was executed by the results of flow analysis in this study. Consequentially the large-scale vortex flow could be found in downstream spray and the formed vortex governs the mixture formation process in diesel spray.

• Journal of the Korean Society for Precision Engineering
• /
• v.7 no.2
• /
• pp.28-38
• /
• 1990

The study is concerned with the theoretical and experimental investigation of axisymmetric fluid pressure-driven hydroforming of sheet metal by forming over the die cavity. The rigid-plastic finite element method is employed to calculate the stress and strain distribution. The effect of blank size and die radius is also studied in the finite element analysis. Experiments are carried out for hydroforming of cold-rolled steel sheets under various process conditions. The computational results are compared with the experimental results for the forming pressure vs. pole displacement relations and strain distributions. Comparison has shown that theoretical predictions by the finite element method are in good agreement with the experiment with the experimental observations. Thus, it is shown that the rigid-plastic finite element method is effectively used in the analysis of axisymmetric fluid pressure-driven hydroforming process.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.262-267
• /
• 2007

In this paper, we study about wear properties for the metal matrix composites fabricated by low pressure infiltration process. Metal fiber preform reinforced aluminum alloy composite were fabricated by low pressure casting process under 0.4MPa. Infiltration condition was changed the pressure infiltration time of 1 s, 2 s and 5 s under a constant pressure of 0.4MPa. The molten alloy completely infiltrated the FeCrSi metal perform regardless of the increase in the pressure acceleration time. However, the infiltration time at the pressure acceleration time of 1s was shorter than at the pressure acceleration time of 2s or 5s. The FeCrSi/A366.0 composite was investigated the porosity. The porosity is reducing as the pressure acceleration time compared with the pressure acceleration time of 2s and 5s. The FeCrSi/A366.0 composites were investigated the wear resistance. FeCrSi/A366.0 composite at pressure acceleration time of 1s has excellent wear resistance.

• Journal of Korean Society of Disaster and Security
• /
• v.16 no.1
• /
• pp.91-103
• /
• 2023

This study aims to investigate the dynamic fracture characteristics of rocks and rock-like materials subjected to the Nonex Rock Cracker (NRC), a vapor pressure crushing agent that produces vapor pressure by instantaneously vaporizing a liquid mixture crystallized through the thermite reaction. Furthermore, the study seeks to develop an analytical technique for predicting the fracture pattern. A dynamic fracture test was performed on a PMMA block, an artificial brittle material, using the NRC. High-speed cameras and dynamic pressure gauges were employed to capture the moment of vapor pressure generation and measure the vapor pressure-time history, respectively. The 2-dimensional Dynamic Fracture Process Analysis (2D DFPA) was used to simulate the fracture process caused by the vapor pressure, with the applied pressure determined based on the vapor pressure-time history. The proposed analytical method was used to examine various fracture patterns with respect to granite material and high-performance explosives.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2001.05a
• /
• pp.197-200
• /
• 2001

A manufacturing process of composite pressure vessel was studied. The vessel was fabricated using the filament winding process. It is utilized as a container of high pressure Helium gas which propels a rocket fuel and an oxidizer. The layup patterns were determined based on the lamination theory. 3-axis controlled filament winding machine was developed to realize the patterns. The vessel was successfully fabricated using the developed machine. And the hydraulic pressure test was performed to measure an applied pressure-strain relations on the composite vessel.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.90-95
• /
• 2007

In order to investigate the optimum condition of the autofrettage process for the diesel engine injection pipe, different values of autofrettage pressure, pressure rising time, pressure holding time, and repetition of autofrettage process were applied. Autofrettage was preformed by applying the hydrostatic internal pressures of 603 MPa, 535 MPa, 500 MPa on the fuel injection pipe, corresponding to theoretically 50%, 30%, and 20% overstrain levels, respectively. The autofrettage residual stresses in the injection pipe were experimentally determined by using X-ray diffractometer. As the overstrain level increased, the magnitude of compressive residual stress at the bore increased. It was found that the rising time to reach the autofrettage pressure, holding time at the autofrettage pressure, and repeating application of the autofrettage pressure on the pipe had no significant influence on the residual stress distributions.

• Journal of Microbiology and Biotechnology
• /
• v.17 no.3
• /
• pp.524-529
• /
• 2007

Pressure inactivation behavior of Bacillus amyloliquefaciens spores was investigated in deionized water. The spores of B. amyloliquefaciens were subjected to $105^{\circ}C$ and 700 MPa. The magnitude of the decrease in viability after pressure treatment was similar to that after pressure treatment followed by heat shock. The increase of dipicolinic acid (DPA) release was correlated with the spore inactivation, and the hydrophobicity did not significantly change during the pressure-assisted thermal processing (PATP). Lag phase duration increased with increasing pressure process time. The mechanisms of spore germination and inactivation during the PATP were related to a complex physiological process.

• Carbon letters
• /
• v.1 no.3_4
• /
• pp.158-164
• /
• 2001

It is well known that the fabrication process of carbon/carbon composites is very complex. Above all, the carbonization process have major effect on the morphology development of carbon matrix. Carbon/carbon composites of 4-directional fiber preform were fabricated using the coal tar based pitch as a matrix precursor in this study. According to carbonization pressure of 1 bar, 100 bar, 600 bar, and 900 bar, morphological changes of cokes and matrix of composites were discussed. As the carbonization pressure increased to 600 bar, the flow pattern morphology of bulk mesophse was well developed. On the contrary, mosaic pattern morphology was found in case of 900 bar of carbonization pressure. It is confirmed that the carbonization pressure have profound effect on the degree of graphitization and crystal size of carbon matrix. Even in the highly densified carbon/carbon composites, large voids were still found in the matrix pocket region.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.679-682
• /
• 2002

Resistance spot welding using air gun has been used for joining the sheet metal in automotive manufacturing process. Although air gun has many advantages, it also has the limitation to control the pressure as a factor to improve weld quality. In this study, we apply servo gun using servo motor to resistance spot welding and find the relationship between welding pressure and welding quality. Trough the experiment to change welding pressure during the welding cycle, we can make it clear that the change of welding pressure is greatly influence on the welding quality. To get in a. using response surface methodology, drew out the optimal welding pressure profile for welding quality progresses. We made an optimal profile of welding pressure which improves welding quality using response surface methodology.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.17 no.1
• /
• pp.153-160
• /
• 2018

A pressure vessel consists of an inner tank and the outer tank; the material of the inner tank is austenite stainless steel, and the outer tank is general carbon steel. As the storage amount increase, the size of the inner tank for LNG also increases, which eventually increases the weight of the LNG storage tank. The Cold Stretch method can transport and store the LNG in a larger amount than the conventional pressure container, and the weight of the pressure vessel can also be reduced at 50 70% due to the reduction of the thickness, which is excellent from an economic and energy consumption perspective. Although the Cold Stretch method has these advantages, the domestic situation has not developed any related legislation. In this study, the actual production of pressure vessels using the Cold Stretch method will be processed and the volume expansion after the Cold Stretch will be checked and compared with the mechanical properties.