• The KSFM Journal of Fluid Machinery
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• v.9 no.2 s.35
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• pp.13-18
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• 2006

This paper was studied to design Process considered flexibility and reliability of suction and discharge valves. Flexibility and reliability of valves are main important factors in compressor valves design. And they are incompatible with efficiency of compressor. In this study, we have performed the optimal design of CO2 compressor valves to consider these factors. At first, we analyzed performance simulation of compressor to obtain optimal flexibility level of valves. From this simulation, we could get some important data at valve design like the optimal natural frequency and the height of retainer. After that we studied to reliability of valves corresponding to optimal flexibility level by finite element method. For each case bending stress and natural frequency were obtained by it. Also we investigated the fatigue stability to obtain optimal valve shape that ensured to reliability.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.247-254
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• 2003

The lightness of components required in automobile and machinery industry is requiring high strength of components. In particular manufacturing process and new materials development for solving the fatigue fracture problem attendant upon high strength of suspension of automobile are actively advanced. In this paper, the effect of compressive residual stress of spring steel(JISG SUP-9) by shot-peening on fatigue crack growth characteristics in high temperatures($100^{\circ}$, $150^{\circ}$, $180^{\circ}$) was investigated with considering fracture mechanics. So, we can obtain followings. (1)Compressive residual stress decreases in high temperature, that is, with increasing temperature. (2)The effect of compressive residual stress on fatigue crack growth behavior in high temperature increases below ${\Delta}K=17{\sim}19MPa$ (3)It was investigated by SEM that the constraint of compress residual stress for plastic zone of fatigue crack tip was decreased in high temperature as compared with room temperature.

• 한국기계연구소 소보
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• s.18
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• pp.169-175
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• 1988

The influence of mean strain on the behavior of early stage stress amplitude was investigated quantitatively in low cycle fatigue. It was obtained that the exponent of cyclic strain(n') and the coefficient of cyclic strain(C') decreased with increasing cycle numbers in compressive mean strain level. But it was the opposite in 0% mean strain and tensile mean strain level. And the cyclic yield strength ($\delta_(yc)$) was constant irrespective of mean strain or cyclic strain

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.5
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• pp.120-126
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• 1998

Second step shot peening was applied on both smooth specimen and U-notch specimen in order to investigate the stress distribution and the improvement in fatigue strength. Various experiments and measurements such as rotary bending fatigue test and the measurement of compressive residual stress were performed. The results showed that the fatigue strength of second step shot peened specimens increased by 34 percent compared to that of unpeened ones. Compressive residual stress also considerably increased, which resulted in the increase of fatigue strength. finite element analysis showed that shot peening is effective in decreasing the bending stress by external force. The effectiveness of shot peening in reducing the compressive residual stress was anticipated by the superposition of the concentrated stress and the compressive residual stress.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.283-283
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• 2015

현재 LAC 베어링에 적용되는 표면 처리는 일반적으로 하드터닝+슈퍼피니싱 가공이 적용되고 있고, 장수명을 위한 표면 처리 기술이 보다 더 요구되는 추세이다. Burnishing 기술은 매끄럽고 단단한 공구를 베어링 궤도면에 충분한 압력을 가하여 서로 문질러(rubbing) 마찰면을 소성 변형시켜 표면 거칠기 및 압축 잔류 응력 등을 향상 시키는 기술이며, 베어링과 같은 금속의 경우 버니싱 가공 적용 시 광택을 띠는 특성을 가지므로 외관 품질 향상에 기여하므로 슈퍼 피니싱 공정을 대신할 수 있다. 또한 표면 finishing, 표면 경도, 내마모성 및 피로/부식 저항성을 향상시킨다. 이에 본 연구에서는 슈퍼 피니싱 가공을 대신하기 위한 버니싱 가공의 물성을 검토하였고, 다른 공정과의 비교를 통한 버니싱 기술의 효과 확인하였다.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.2
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• pp.39-46
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• 1990

In this study, the mechanical behavious of a center crack which propagates between two holes in a panel are investigated. It is confirmed experimentally and analytically that a center crack stops and a small crack initiates from holes and propagates to fracture because of the compressive stress arising along the path of the fatigue crack propagation. Futhermore, it is noted that regardless of the configuration of the crack and the structure, Paris' law can be applied to the fatigue crack propagation.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.9
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• pp.61-67
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• 1997

Hardened layer and compressive residual stress created by carburized treatment effect on bending strength of gear massively. Also, shot peening treatment improves the strength of carburized gear as it does the hardness and residual stress of surface layer. In these days shot peening techniques are welcomed as one of physical improvement ways around the surface of materials. It is used widely because qualitative analysis of shot peening has become possible and surface treatment can be done with very little costs comparaed to other surface improvement methods. Therefore this study investigates the effect of shot peening in surface shape and bending fatigue strength after doing many kinds of shot peening treatments, then doing fatigue test and also explained characteristics of shot peening gear.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.5
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• pp.33-41
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• 2011

In this paper, we propose a lossless compression scheme for cloud point data of the target construction by using doubleness and decreasing useless information of cloud point data. We use Hough transform to find the horizontal angle between construction and terrestrial LIDAR. This angle is used for the rotation of the cloud point data. The cloud point data can be parallel to x-axis, then y-axis doubleness is increased. Therefore, the cloud point data can be more compressed. In addition, we apply two methods to decrease the number of cloud point data for useless information of them. One is decimation of the cloud point data, the other is to extract the range of y-coordinates of target construction, and then extract the cloud point data existing in the range only. The experimental result shows the performance of proposed scheme. To compress the data, we use only the position information without additional information. Therefore, this scheme can increase processing speed of the compression algorithm.

• Composites Research
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• v.24 no.1
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• pp.10-16
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• 2011

Many tests are required to predict the fatigue life of composite laminates made of various materials and having different layup sequences. Aiming at reducing the number of tests, a methodology was presented in this paper to predict fatigue life of composite laminates based on fatigue life prediction of constituents, i.e. the fiber, matrix and interface, using micromechanics of failure. For matrix, the equivalent stress model which is generally used for isotropic materials was employed to take care of multi-axial fatigue loading. For fiber, a maximum stress model considering only stress along fiber direction was used. The critical plane model was introduced for the interface of the fiber and matrix, but fatigue life prediction was ignored for the interface since the interface fatigue strength was presumed high enough. The modified Goodman equation was utilized to take into account the mean stress effect. To check the validity of the theory, the fatigue life of three different GFRP laminates, UDT[$90^{\circ}2$], BX[${\pm}45^{\circ}$]S and TX[$0^{\circ}/{\pm}45^{\circ}$]S was examined experimentally. The comparison between predictions and test measurements showed good agreement.

• Journal of Korea Technology Innovation Society
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• v.12 no.1
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• pp.165-188
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• 2009

The major purposes of the research are to see the underlying disciplines of technology innovation management which contribute to Korean research. To do that, we employed author cocitation analysis which has been proved to be robust. We compiled all the citations of two major Korean journals between 1993 and 2006. We also included up to 3rd author, which makes a cocitation analysis more comprehensive, compared with the previous analysis for the first author only. We identified 239 authors who have more than 10 citations. From the cocitation combinations based on the 239 authors, we selected and analyzed 100 most cocited authors. Out of 100 authors a group of 23 authors who command both higher citations and cocitations were chosen for detailed analysis. The results show that the average number of publications is 22.2, the average number of citations to them is 58.5, and the average number of citations to a publication is 2.6. Also, the average number of cocitations is around 10 times that of citations. The results indicate that there are six major disciplines: Technology/Innovation, Management of Technology, Economics of Technology, Development, Valuation of Technology, and Growth. Noteworthy points are the following. 1) Most of the members of the technology management group are management scholars, and the groups of economics of technology and growth are economists, while the groups of technology innovation and development group are not represented by specific disciplines. 2) Considering the groups overall from the traditional academic disciplines, the main branches are management and economics. 3) The valuation of technology group consists mostly of Korean researchers.