• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.150-154
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• 2008

In this research, stress components and principal stresses of O-ring under internal pressure and under uniform squeeze rate were obtained from the stress freezing method of photoelastic experiment and photoelastic experimental Hybrid method for 3-dimensional problems. The obtaining processes of those were introduced. It was certified that the processes of those are effective for the 3-dimensional stress analysis of structures. Stress freezing method, the obtaining processes of those and photoelastic experimental hybrid method were effectively applied to the stress analysis of O-ring made from rubber that under uniform deformation and internal pressure. Stress components and principal stress of Oring under uniform squeeze rate and under internal pressure were analyzed.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.123-128
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• 1998

In fracture problems, stress intensity factors obtained theoretically and experimentally have been effectively utilized in the analytical evaluation of the cracks effect. The effect of surface crack of a cylindrical and a hollow cylindrical bar is investigated, as well as the effect of the thickness of a hollow cylindrical bar and inclined crack of a hollow cylinder subjected to torsion moment. In this study, stress intensity factor Km of mode III which expresses the stress state in the neighborhood of a crack tip is used. Stress analysis was conducted of the inside of a hollow cylinder in the axial direction of three dimensional crack tip subjected to torsion moment by combining the caustics method and the stress freezing method.

• 대한기계학회논문집
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• 제15권2호
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• pp.424-435
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• 1991

To develop the photoelastic experiment method for the orthotropic material under pure torsional moment is the main objective of this research. In the development of photoelastic experiment for orthotropic material under pure torsional moment, the important problems and their solutions are the same as following. In the model material for photoelastic experiment, it was found that C.F.E.C.(Copper Fiber Epoxy Composite) can be used as the model material of photoelastic experiment for orthotropic material. In the stress freezing cycle, it was assured that stress freezing cycle for epoxy can be used as the stress freezing cycle of the photoelastic experiment for orthotropic material. In the slicing method, it was found that the negative oblique slicing method can be effectively used as slicing method in 3-dimensional photoelastic experiment. In the measuring method of stress fringe values and physical properties in the high temperature, it was found that stress fringe values can be directly measured by experiment and physical properties can be directly or indirectly by equation between stress fringe values and physical properties developed by author. In the stress analysis method of orthotropic material under pure torsional moment by photoelastic experiment, it will be studied in the second paper.

• 대한기계학회논문집A
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• 제22권1호
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• pp.227-237
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• 1998

In case the systems have radioactivity, toxic liquid or expensive fluid, and have to be performed repair work at one point of the system pipe, the formation of an internal ice plug by the removal of heat from the pipe is often consideredas a useful method. In this procedure, an annular jacket is placed around the pipe, and the jacket is then filled with liquid Nitrogen(-196.deg. C). Thermal analysis by the finite element method based on the laboratory experiments has been constructed. The result of the finite element analysis on the experimental model shows to be reasonable, and thus the finite element analysis for different pipe size, material and thickness has been performed to see if the ice plugging procedure in various applications can be safely performed without possibility of damage to the pipe. It has been confirmed that in carbon steel pipes the maximum stress is found around the boundary of the freezing jacket, and the stress increases as pipe thickness increases, but the maximum stress shows no consistency along the increment of the pipe diameter. The maximum stresses appear lower than yield stress in carbon steel. It has been also shown that in stainless steel pipes the maximum stresses are also found around the boundary of the freezing jacket, but almost the same value in spite of different pipe size an thickness, and the maximum stresses show slightly higher than the yield stress of the stainless steel.

• 한국농공학회논문집
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• 제52권1호
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• pp.51-59
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• 2010

The cemented sand and gravel (CSG) method is a construction technique that adds cement and water to rock-like materials, such as rivered gravel or excavation muck which that can be obtained easily at areas adjacent to dam sites. This study was performed to evaluate the unconfined compressive strength properties and freezing and thawing resistance of CSG materials with unit cement content. The three types of CSG-80, CSG-100 and CSG-120 with cement content were designed to evaluate the optimum water content, dry density, strength, stress-strain, micro structure and durability factor. As the results, the optimum water content ratio with cement content showed almost similar tendency, and the unconfined compressive strength and dry density increased as cement content increases. The strength ratio of 7 days for 28 days were in the range of 55~61 % and the strain ratio in stress-strain curve were in the range of 0.8~1.6 % nearby maximum strength in 28 days. It is expected that this study will contribute to increasing application of CSG method as well as to increasing the utilizing of CSG materials as a environmentally friendly CSG method.

• 한국약용작물학회지
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• 제26권1호
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• pp.1-7
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• 2018

Background: Rehmanniae radix preparata (RRP) has been used as a traditional medicine and is one of the most important oriental herbal medicines. However, the physical characteristics of RRP are not suitable for use in industry. The present study was under-taken to determined the preparation method of RRP powder and the physicochemical characteristics of RRP powder by milling under different pre-freezing temperatures. Methods and Results: Moisture content, powder yield, particle size, bulk density, compressive stress, extraction yield, and 5-HMF content of PRR powders by milling with pre-freezing temperatures (-20, -40, -60, and $-80^{\circ}C$) were analyzed, and correlation among these factors was determined. Powder yield increased and particle size decreased in a pre-freezing temperature-dependent manner from -20 to $-60^{\circ}C$. The Hausner ratio increased from 1.186 to 1.225 with decreasing temperature from -20 to $-80^{\circ}C$, whereas compressive stress showed the opposite trend. Extraction yield and 5-HMF content were not significantly different between RRP powder. Significant correlations were observed among pre-freezing temperature and physical characteristics (e.g., yield, particle size, Hausner ratio, and compressive stress). Conclusions: These results suggest that the pre-freezing temperature is an important factor affecting the physical characteristics of PRR powder and applicable to the industrial production of RRP powder.

• 한국정밀공학회지
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• 제25권3호
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• pp.165-175
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• 2008

An ankle-foot orthosis(AFO) is a brace for persons with gait disabilities to support or replace the function of ankle joint. Ankle-foot orthoses(AFO's) are usually prescribed to alleviate the drop-foot by constraining the excessive plantar flexion. The shape and the strength of the AFO are often based on 'trial and error' due to a lack of knowledge of the stress distribution in the AFO. In this study, an improved stress-freezing method was proposed to measure the stress distribution characteristics in the AFO. As a result, a photoelastic material with low freezing temperature was developed to measure the stresses under a person's direct contact loading condition. The three-dimensional stress-1rozen photoelastic models of AFO's for five stages of stance phase such as heel contact, foot flat, mid stance, heel off, and toe off were produced. The results of photoelastic analysis revealed that the stresses developed in the AFO were varied considerably from tensile to compressive or vice versa, during walking. At the posterior part of ankle joint in the AFO, the maximum compressive stress of 1.81MPa was observed in the mid stance, and the maximum tensile stress of 0.74MPa was observed during heel contact. The overall stress levels in the AFO's were low in the toe off phase. The results suggested that the posterior part of ankle joint might be the most fragile part in the AFO.

• Journal of Biosystems Engineering
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• 제16권3호
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• pp.211-218
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• 1991

In this study, the break of the rotary blade which is occured from a stress concentration of the inside of blade by the outside impulsive load, is analyzed to 3-dimension used by the Freezing Photoelastic Method. These results are as follows. 1. The bending and compression stress are the greatest at the location of blade case. 2. The section area of 3cm-location from the blade case is the smallest, therefore, there are breaked 58% of all at this location and are proofed to the most danger section 3. The section area which by stress concentration of 3cm-location from blade case is caused by the production of blade, and it was higher danger of break than another location's. 4. In the location of 6cm and 9cm from the blade case, the bending stress has received a little and the section area has larger than another's, so it is not almost possible that the break at that location 5. In order to prevent of break, the external part which has contacted soil have to made tender for receiving a little stress and the internal part which received a large stress have to strengthen.

• 한국생산제조학회지
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• 제8권1호
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• pp.21-27
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• 1999

In this study, stress intensity factors KI, KII, KIII are existing at the same time to a hollow cylindrical bar of three dimension inclination crack. In order to investigate by experimentally the effect of the inclination angle $\psi$ of crack, artificial inclination cracks in the circumferential direction are put in the surface of a hollow cylindrical bar made by the epoxy-resin. Experimentally, stress analysis methods of stress intensity factors were proposed. But, suitable method are the caustic method and the photoelastic stress freezing method. The mixed mode of KI, and KII, were determined by the photoelastic method of the classical approach method and the FORTRAN language program of the used smallest square method.

• 한국생산제조학회지
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• 제7권5호
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• pp.46-52
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• 1998

In fracture problems, stress intensity factors obtained theoretically and experimentally have been effectively utilized in the analytical evolution of the cracks effect. The effect of surface crack of a cylindrical and a hollow cylindrical bar is investigated, as well as the effect of the thickness of a hollow cylindrical bar and inclined crack of a hollow cylinder subjected to torsion moment. In this study, stress intensity factor Km of mode III which expresses the stress state in the neighborhood of a crack tip is used. stress analysis was conducted on the inside of hollow cylinder inthe axial direction of three dimensional crack tip subjected to torsion moment by combining the caustics method and the stress freezing method.