• Journal of the Korean Professional Engineers Association
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• v.20 no.3
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• pp.5-14
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• 1987

연속체의 해석에 있어서, 특별한 경우를 제외하고는, 구조물의 개략적인 거동을 파악해야 될 경우가 종종 있다. 이러한 요구에 부응하기 위해서 강체요소법(Rigid Element Method)이라 불리우는 새로운 해석법이 개발되었다. 강체요소법은 원래 평정연구실에서 벽식프리캐스트 철근콘크리트 구조물의 탄소성해석을 하기 위해서 개발된 해석법에 착안하여, 내수벽과 같은 연속체에 적용함으로서 시작된 수치해석법이다. 그 후 저자들은 도통쉘, 구형쉘 혹은 이들이 조합된 쉘구조물에 적용할 수 있도록 개발 확장하였다. 강체요소법의 기본개념은 연속체의 분해된 각 요소를 강체(rigid body)라고 가정하고, 각 요소들은 요소의 강성으로 치환된 가상스프링으로 서로 연결되어 있다고 가정하여, 이 가상스프링의 거동을 평가함으로서 전체구조물의 거동을 파악하는 해석법이다. 이때 요소의 주변에 취해진 스프링은 해석을 단순화하기 위해서 축력, 면내전단력 및 면외전단력만을 전달한다고 가정하고, 요소의 강체변위(자유도)는 요소내의 임의의 한 점에서 취하며, 이 점에서의 강체변위(rigid displacements)는 요소의 주변에 취해진 스프링을 통하여 다른 요소로 전달된다. 상기와 같은 강체요소법의 개념을 연속체의 탄성 및 탄소성해석에 적용하면, 해석적 개념이 단순할 뿐만 아니라 구조물 전체의 자유도수를 대폭 줄여 컴퓨터 계산시간을 절약할 수 있는 잇점이 있고, 거시적인 모델(macroscopic modeling)과 미시적인 모델 (microscopic modeling)의 중간적인 성격을 가지기 때문에 구조물의 파괴상황에 대해서도 그 개략을 파악할 수 있다. 본 논문에서는 강체요소법을 보다 일반화된 해석법으로 개발, 확장하기 위해서 종전에 단층스프링시스템(single-layer spring system)으로 해석이 어려웠던 문제점들을 보완한 복층프링시스템(double-layer spring system)을 사용함으로서 휨, 비틀림의 효과를 파악할 수 있는 이론적 개념을 적용한 새로운 구요소, 원통요소 및 평면요소를 개발하고, 이러한 강체요소들의 적합매트릭스의 유도 및 해석저긴 방법을 정식화하였다. 또 휨, 비틀림 및 전단력의 효과를 고려한 사각형원통요소 및 능형원 통요소를 이용하여 원통쉘의 탄성 및 탄소성해석할 수 있는 프로그램을 개발하고, 이 프로그램으로 캔틸레버로된 연속형철근콘크리트 원통쉘의 탄성 및 탄소성해석에 적용하여 구조물의 거동에 관한 수치해석의 결과, 즉 내력의 분포, 균열의 진전, 파괴의 상황 및 변형의 상태 등을 파악해 보았다.

• Geotechnical Engineering
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• v.13 no.4
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• pp.149-162
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• 1997

A series of torsion shear tests were performed to study the strength characteristics of sand under various stress paths during rotation of principal stress. These results can be classified into two groups of 25cm and 40cm according to the height of specimen, and toy que was applied only in the clockwise direction. In this study, strength characteristics of sand for the principal stress ratio in torsion sheartests were investigated and their results were compared with Lade's failure criterion. And the effect for specimen was considered. From the results of tests, friction angle of sand was affected by the deviatoric principal stress ratio $b:(\sigma_2 -\sigma_s)/(\sigma_2, -\sigma_3)$Failure strength of sand was determined not by the stress paths but by the current stress state. From comparison of specimens on 25cm and 40cm height, effect of end restraint could not be found. In the test where b is over 0.5 due to extension force, necking phenomenon by the strain localization was found.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.471-474
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• 2008

기업들에게 있어 가격 경쟁력을 갖추기 위한 노력은 끊임없이 이어져 왔으며, 제조 부분에서의 원가절감이나 합리화 등은 어느정도 성과를 이끌어 내는데 성공하였다. 하지만 최근들어 그런 생산비 절감의 경우 점점 한계점에 도달한 모습을 내비치고 있는 실정이며, 이에 기업들은 자연스럽게 매년 그 증가 폭이 커지고 있는 물류로 눈길을 돌리고 있다. 따라서 물류에 대한 관리는 최근 각 기업들에게 있어서 최대 관심사임에 틀림없으며, 이를 위해 기업들은 앞 다투어 물류 정보시스템을 도입하고 이를 활용하려 하고 있다. 하지만 아직까지는 물류 정보의 표준화와 연동 문제 등으로 인해 어려움이 뒤따르고 있는 실정이다. 본 논문에서는 이런 물류정보시스템 운영에 대한 적용 사례를 물류비 시스템을 예로 들어 분석을 해보았으며, 물류정보시스템이 안고 있는 난제를 극복하기 위한 하나의 방안으로 RFID 도입을 통해 물류비 절감과 업무 프로세스 개선을 제시하고자 한다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.393-398
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• 2001

The technique of high speed machining is widely studied in machining fields, because the high efficiency and accuracy in machining can be obtained in high speed machining. Unfortunately the development of tool for high speed machining in not close behind that of machine tool. In this study, several types flat endmill is prepared for obtaining data according to tool shape. Especially, we concentrated in helix angle, number of cutting edge, rake angle and relief angle. Machinability is measured by cutting force, tool life, tool wear, chip shape and surface roughness according to cutting length. 3-axis cutting forces are acquired from the invented tool dynamometer for high speed machining. Particularly, we found out that the axial cutting force waveform has a good relation with tool wear features. By above results, it is suggested the endmill tool with $45^{\circ}$ helix angle, 6 cutting edge, $-15^{\circ}$ rake angle and $12^{\circ}$ relief angle be suitable for high speed machining

• Journal of the Korean Magnetics Society
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• v.27 no.4
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• pp.135-139
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• 2017

The magneto-impedance effect (MI effect) has been investigated in metal core/soft magnetic shell composite wires fabricated by electrodeposition of $Ni_{80}Fe_{20}$ on Cu wire (diameter $190{\mu}m$). The diagonal impedances $Z_{zz}$ and $Z_{{\theta}{\theta}}$ in cylindrical coordinate showed strong MI effect for the magnetic field applied along z-axis, while the off-diagonal impedance $Z_{{\theta}z}$ showed very weak MI effect. We have tried to develop the Cu $core/Ni_{80}Fe_{20}$ shell composite wire having strong MI effect in off-diagonal impedance by electrodeposion under torsional strain. The core/shell composite wire electrodeposited under torsional angles above $270^{\circ}$ showed significantly enhanced MI effect in the off-diagonal impedance. The maximum MI effect was observed in the composite wire electrodeposited under torsional angle of $360^{\circ}$. The developed method to enhance off-diagonal MI effect is expected to increase the applicability of the core/shell composite wire to magnetic sensor material.

• Journal of KSNVE
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• v.10 no.4
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• pp.655-661
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• 2000

Diesel power plant can be used as a power supplier for the isolated place where consumption of electric power is variable. The reason is that mobility and durability of diesel engine is superior to those of other thermal engines. However, there are some disadvantages for using these diesel engines such as bigger vibratory excitation force comparing to the others, which result from high combustion pressure of cylinders and inertia force of piston reciprocating masses. In this paper, control and optimization of torsional vibration of 12K90MC-S engine for diesel power plant using uneven crank angles is identified by theoretical analysis and vibration measurement.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.2
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• pp.71-78
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• 2011

A kart is a vehicle without the suspension system and the differential gear. The kart frame as an elastic body plays the role of a spring. By the cornering of a kart, rolling, pitching and twisting motions are induced in the kart frame. Also the slip or noncontact of the wheel and a permanent deformation of the kart frame can be induced. In order to examine closely this phenomenon, measurement on height-displacements with various sensors and tracking system and analysis on the kart frame twisting characteristics with the rolling and pitching angle are needed. According to the measurement result, while driving in a curve at high speed the kart frame is quite twisted. Analysis on the measurement results shows that a kart used primarily in high speed requires a frame with low torsional stiffness and a frame material with high tensile strength and large elongation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.4
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• pp.279-290
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• 2004

The differential quadrature method (DQM) for a system of coupled differential equations governing the elastic stability of thin-walled curved members is presented, and is applied to computation of the eigenvalues of out-of-plane buckling of curved beams subjected to uniformly distributed radial loads including a warping contribution. Critical loads with warping, which were found to be significant, are calculated for a single-span wide-flange beam with various end conditions, opening angles, and stiffness parameters. The results are compared with the exact methods available. New results are given for the case of both ends clamped and clamped-simply supported ends without comparison since no data are available The differential quadrature method gives good accuracy and stability compared with previous theoretical results.

• Composites Research
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• v.12 no.2
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• pp.53-61
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• 1999

A failure criterion must be considered in each failure mode and loading condition to provide easy determining strength parameters, flexibility and rational simplicity. In this study, new failure criterion was developed by introducing equivalent strength under biaxial loading of tension and torsion. The experimental results showed that the equivalent biaxial strength has a power law relation with respect to a parameter, cos($tan^{-1}R_b$). Failure strength under biaxial loadings could be predicted as a function of tensile strength, torsional strength and biaxial ratio. The scattering of experimental data could be predicted using a Weibull distribution function and the concept of equivalent biaxial strength. Also, in this study, a fatigue theory was developed based on a plane stress model which enabled the S-N curve for combined stress states to be predicted from the S-N data for uniaxial loading. The prediction models can be predicted a biaxial strength and fatigue life of general laminated composite naterials under multi-axial loadings.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.44-47
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• 2002

A liner static and dynamic analysis for a golf shaft, which is made of carbon fiber reinforced composite materials, is presented in this study. Major mechanical parameters of golf shafts such as deflection, torsional angel, frequency of vibration(CPM), and kick point are analyzed by finite element method. The effects of major parameters on the performance of golf shafts are also discussed. The results show that the major parameters of golf shafts are strongly dependent on the material properties of fibers and design pattern of golf shafts. The present results will be useful to design sheet-rolled golf shafts.