• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.251-254
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• 2005

The flow forming has been used to produce long thin walled tube parts, with reduced forming load and enhanced mechanical and surface quality for a good finished part compared with other method formed parts. So flow forming technique is used widely in industrial production. Especially spinning and flow farming techniques an used frequently in automotive, aerial, defense industry. In this paper, FEM analysis of three-roller backward flow forming of a workpiece is carried out to study effects of forming depth and feed rate on forming force. The axial and radial forces on several forming depth and feed rate conditions are obtained. The phenomena such as bell mouth, build up and bulging during simulation are observed as well.

• Journal of the Society of Naval Architects of Korea
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• 제40권6호
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• pp.88-95
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• 2003

Liquid storage rectangular tank structures are used in many fields of airplane and marine engineering. Fatigue damages are sometimes observed in these tanks which seem to be caused by resonance. Therefore it is essentially important to estimate vibration characteristics of tank structures. Many Investigators studied the vibration of cylindrical and rectangular tank structures containing still fluid. In general, the eigenbehavior of interior liquid is characterized by the sloshing mode while that of the structure by the bulging mode. However, the structure deformation to the sloshing mode and the liquid free-surface fluctuation to the bulging mode have been neglected in the classical added-mass computation. in the present paper, we study the vibration characteristics with sloshing mode effect.

• Journal of Industrial Technology
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• 제27권A호
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• pp.121-130
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• 2007

Centrifuge model tests were performed to find appropriate equations proposed previously of estimating the bearing capacity of the composite clayey soil reinforced with sand compaction pile. Model tests were carried out with changing the replacement ratio of SCP (20%, 40%, 70%), contents of fine materials (5%, 10%, 15%) and ratio of treated width to loading width (1B, 2B, 3B). Test results about bearing capacity of the composite ground were obtained by performing the surcharge load tests with measurements of applied loads and vertical displacement. Bearing capacities against bulging and shear failures were estimated by the existing equations. As results of comparing the estimated bearing capacity with experimental values the bearing capacities estimated by Greenwood's equation (1970) for bulging failure mode were similar to the test results.

• Journal of Electrical Engineering and Technology
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• 제7권1호
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• pp.91-96
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• 2012

We introduce an understanding of silver (Ag) inkjet overlap-printing characteristics from the viewpoints of cohesion between ink droplets and adhesion between an ink droplet and a surface. The printing characteristics were closely monitored by changing the surface energy to elucidate the effect of adhesion and cohesion on printing instability, such as droplet merging and line bulging. The surface energy of the substrate was changed through the hydrophilization of a hydrophobic fluorocarbon-coated surface. The surface energy and ink wettability of the prepared surfaces were characterized using sessile drop contact angle analysis, and printing instability was observed using an optical microscope after drop-on-demand inkjet printing with a 50% overlap in diameter of deposited singlet patterns. We found that the surface energy is not an appropriate indicator based on the experimental results of Ag ink printing on a hydrofluoric-treated silicon surface. The analytical approach using adhesion and cohesion was helpful in understanding the instability of the inkjet overlap-printing, as adhesion and cohesion represent the direct interfacial relationship between the Ag inks used and the substrate.

• The Journal of Korea CHUNA Manual Medicine
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• 제3권1호
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• pp.43-53
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• 2002

Objectives : The object is to study a clinical effect regarding the conservative treatment of the patient who was diagnosed as the herniated Intervertebral lumbar disc(HIVD) and hospitalized in the oriental medical hospital and clinical study about the type of the HIVD. Methods. The clinical studies were done on 65 cases (hospitalized in Dept. of Oriental Rehabilitation Medicine, jaseng on oriental medical hospital from June 2001 to May 2002) who complained of low back pain or sciatica and diagnosed as HIVD on CT(computerized tomography) or MRI(magnetic resonance imaging). They were given both oriental conservative treatment and exercise during the hospitalization period. We investigated and observed 20 items about sex, age, weight, height, occupation, smoking. obesity, duration of disease, clinical symptom and treatment duration in basis of medical recording which was drawn up at patient hospitalization. We classified HIVD with 4 types(Bulging. Protruded. Extruded, Sequestered) and decided the case which simultaneously had 2 overs with Mixed type. The treatment evaluation standard was classified with 4 branches; Excellent. Good, Fair and Poor. Results & Conclusions : The treatment result of over 'fair' is bulging type 85%, protruded type 92.7%, extruded type 100% and the mixed type was 85.1 %. The effect was good in order of bulging, mixed, protruded and extruded type. It appeared most plentifully with 30 people in L4-5 and L5-S 1 disc herniation type.

• Transactions of the Korean Society of Mechanical Engineers
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• 제16권4호
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• pp.684-695
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• 1992

The present study is concerned with the analysis of three-dimensional sheet metal forming process by the upper-bound method. For the analysis a systematic approach is necessary for the expression of geometric configuration of the deforming workpiece. In the present paper geometric configuration is constructed by three unit surfaces which are defined by sweeping the vertical section curves and boundary curve. The principal components of strain increment during the process is calculated directly from the change of geometric configuration for an arbitrary triangular element. The corresponding solution is found through optimization of the total energy consumption with respect to some parameters assumed in the velocity field and geometric profile. In order to verify the effectiveness of the present method, hydrostatic bulging of a rectangular disphragm is analyzed and the computation by the present method for the geometric shape renders the good result. From the comparison of the present results with the existing experimental results and elastic-plastic finite element solutions, good agreements have been obtained for the pressure curves, polar membrane strains and pressure distributions. The present method can thus be further applied to the analysis of other three-dimensional sheet metal forming processes.

• Journal of the Korean Society of Manufacturing Process Engineers
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• 제19권2호
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• pp.30-37
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• 2020

We propose a practical method for increasing formability of a sheet metal plate using laser heat treatment (LHT) and cladding process. In this work, two kinds of process such as laser-induced heat treatment and cladding were utilized to evaluate the effect on formability of SUS316 sheets with different thickness of 1 and 3 mm. By using a vertically line-patterned tensile specimen that was LHTed or cladded on its surface, the process parameters of each surface treating method were studied and optimized. Through the basic test, we knew that the laser power of 900 W and scanning speed of 500 mm/min was the best condition for increase of formability. As the treatment results, ultimate tensile strength and elongation were increased as approximately 2.1 and 7.0%, respectively. To verify the usefulness of this work in industrial cases, we conducted a bulging test using with and without LHTed SUS316 sheet metal blanks. The results show that the bulging height of LHTed sheet was increased by 73% compared to that of the original one.

• Geomechanics and Engineering
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• 제12권3호
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• pp.417-439
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• 2017

The stone columns are increasingly being used as a soil improvement method for supporting a wide variety of structures (such as road embankment, buildings, storage tanks etc.) especially built on soft soil. Soil improvement by the stone column method overcomes the settlement problem and low stability. Nevertheless, stone column in very soft soils may not be functional due to insufficient lateral confinement. The required lateral confinement can be overcome by encasing the stone column with a suitable geosynthetic. Encasement of stone columns with geogrid is one of the ideal forms of improving the performance of stone columns. This paper presents the results of a series of experimental tests and numerical analysis to investigate the behavior of stone columns with and without geogrid encasement in soft clay deposits. A total of six small scale laboratory tests were carried out using circular footing with diameters of 0.05 m and 0.1 m. In addition, a well-known available software program called PLAXIS was used to numerical analysis, which was validated by the experimental tests. After good validation, detailed of parametric studies were performed. Different parameters such as bearing capacity of stone columns with and without geogrid encasement, stiffness of geogrid encasement, depth of encasement from ground level, diameter of stone columns, internal friction angle of crushed stone and lateral bulging of stone columns were analyzed. As a result of this study, stone column method can be used in the improvement of soft ground and clear development in the bearing capacity of the stone column occurs due to geogrid encasement. Moreover, the bearing capacity is effected from the diameter of the stone column, the angle of internal friction, rigidity of the encasement, and depth of encasement. Lateral bulging is minimized by geogrid encasement and effected from geogrid rigidity, depth of encasement and diameter of the stone column.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제37권12호
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• pp.1201-1208
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• 2009

Dome stretching tests and tension tests were performed to evaluate the formability of a copper alloy used for manufacturing the regenerative cooling chamber. The test specimens were prepared to investigate the effect of heat treatment and direction of specimens on the formability. The test results show that forming limit values are increased by the heat treatment of the material but the variation of the forming limit values by manufacturing direction is negligible compared to the heat treatment effect, and forming limit values are also different according to the test methods. These results indicate that the high temperature heat treatment of the material before bulging is a very important process to deform the inner cylindrical structure of the regenerative cooling chamber into a nozzle shape by the bulging process without necking or fracture and the test methods also have a great effect on a evaluation of the formability. The forming limit diagram obtained in this study would be utilized to the design of regenerative cooling chamber nozzles.

• Journal of Korean Medicine Rehabilitation
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• 제21권4호
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• pp.119-130
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• 2011

Objectives: The purpose of this study is to find cut the characteristics of intervertebral disc changes arid relative factors of the patients with spondylolisthesis. Methods: We investigated 95 cases of patients who visited one Korean traditional medicine hospital and were diagnosed as spondylolisthesis on lumbar spine X-ray and lumbar spine magnetic resonance imaging(MRI). We selected these cases retrospectively and randomly. We analysed the relativity between number of changed discs and type of change disc and age, level of spondylolisthesis and type of spondylolisthesis. Results: 1. The number of changed discs increased with older and degenerative spondylolisthesis type(p<0.05) and was not related to the level of spondylolisthesis. 2. Bulging disc is the dominant type of disc change(74.12%). The type of changed disc was shown to be similar in lytic and degenerative spondylolisthesis. It was not relative to the level of spondylolisthesis(p>0.05). 3. The direction of nerve compression was diffuse type in about halfly of the patients(47.06%) and the symptoms of patent and dermatome did not matched in 54 cases. Conclusions: The patients who visited a Korean medicine hospital and were diagnosed as spondyolithesis have different characteristics from the established studies. Their discs changed dominantly to diffuse bulging type and the symptoms of patient were not related with the direction and level of the changed discs were spondylolisthesis existed.