점탄성 원통의 모드 I 균열 해석

심우진,오근,Sim Woo-Jin,Oh Guen 한국전산구조공학회 2006 한국전산구조공학회논문집 Vol.19 No.3

In this paper, the stress intensity factor, energy release rate and crack opening displacement are computed using the finite element method for axisymmetric viscoelastic cylinders with the penny-shaped and circumferential cracks. The triangular elements with quarter point nodes are used to describe the stress singularity around the crack edge. The analytical solutions are also derived by using the elastic-viscoelastic correspondence principle and compared with the numerical results to show the validity and accuracy of the presented method. Viscoelastic materials are assumed to behave elastically in dilatation and like a three-parameter standard linear solid. 원환균열과 원주균열을 지닌 축대칭 선형 점탄성 중실축과 중공축이 외력을 받을 때 파괴역학 변수로서 응력확대계수, 에너지방출률 그리고 균열개구변위의 수치해를 유한요소해법을 이용하여 구한다. 균열선단에서는 응력의 특이성을 지닌 1/4절점 삼각형 특이요소가 사용된다. 또한 수치해를 비교 검증하기 위해 탄성-점탄성 상응원리를 이용하여 선형파괴역학의 탄성해들로부터 점탄성 이론해가 유도 제시된다. 해석에 사용되는 점탄성 물성은 체적변형은 탄성적이고 전단변형은 표준선형고체처럼 거동한다고 가정한다. 제시된 수치해법과 이론해는 축대칭 점탄성 거동 연구에 중요한 자료가 된다.

축대칭 문제에서의 동적 응력집중 해석

심우진,이성희,Sim, Woo-Jin,Lee, Sung-Hee 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.11

In this paper, the finite element equations for the time-domain numerical analysis of transient dynamic axisymmetric problems are newly presented. which are based on the equations of motion in convolution integral as in the previous paper. A hollow cylinder subjected to a sudden internal pressure is solved first as a benchmark problem and then the dynamic stress concentrations are analyzed in detail far hollow cylinders having inner and outer circumferential grooves subjected to sudden internal or axial loadings, all the computed results are compared with the existing or the computed ones obtained by using the commercial finite element packages Nastran and Ansys to show the validity and capability of the presented method.

유한요소법에 의한 열점탄성 응력해석

심우진,박인규,Sim, Woo-JIn,Park, In-Kyu 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.7

Uncoupled, quasi-static and linear thermoviscoelastic problems are analyzed in time domain by the finite element approximation which is developed using the principle of virtual work and viscoelasticity matrices instead of shear and bulk relaxation functions as in usual formulations. The material is assumed to be isotropic, homegeneous and thermorheologically simple, which means that the temperature-time equivalence postulate is effective. The stress-strain laws are expressed by relaxation-type hereditary integrals. In spatial and time discritizations, isoparametric quadratic quadrilateral finite elements and linear time variations are adopted. For explicit derivations, the viscoelastic material is assumed to behave standard linear solid in shear and elastically in dilatation. Two-dimensional examples are solved under general temperature distributions T = T(x, t), and compared with other opproximate solutions to show the versatility of the presented analysis.

경근이완요법이 중풍 주관절 경직에 미치는 효과

심우진 ( Woo Jin Sim ),문상현 ( Sang Hyun Moon ),류한진 ( Han Jin Ryu ),정석희 ( Suk Hee Jung ),김성수 ( Sung Soo Kim ),이종수 ( Jong Soo Lee ) 한방재활의학과학회 2004 한방재활의학과학회지 Vol.14 No.1

Objective: Muscles Along Meridians Release Therapy is non-invasive soft tissue release technique as a kind of the Chuna treatment. Three yin meridians of upper extremities were chosen in releasing elbow flexion spasticity after stroke. The effects between control and sample groups were compared. Methods: 40 spasticity patients with hemiplegic stroke were randomized into two groups. 21 patients were treated with muscles along meridians release therapy for 2 weeks. The other 19 patients were cotrol groups. Outcomes were assessed by modified Ashworth scale, VAS, Fugl-Meyer score and modified Barthel index. Results: In terms of spasticity, motor performance ability of upper extremity and passive ROM of shoulder abduction, the sample group showed statistically significant improve. In terms of shoulder pain, motor power of elbow extension and ADL, significant difference between two groups was not shown. Conclusions: In this clinical study, Muscles Along Meridians Release Therapy can be used for improving spasticity, motor performance ability and passive ROM after hemiplegic stroke.

중풍 주관절 경직에 대한 음경(陰經)과 양경(陽經)전침 효과의 비교

심우진 ( Woo Jin Sim ),정석희 ( Suk Hee Jung ),김성수 ( Sung Soo Kim ),신현대 ( Hyun Dae Shin ),이종수 ( Jong Soo Lee ) 한방재활의학과학회 2003 한방재활의학과학회지 Vol.13 No.1

Objective : The electroacupunture(EA) is frequently used to enhance stroke rehabilitation. Many studies about spasticity after stroke with EA were undergone. But mainly the elctrophysiologic character of EA is compared such as the frequency, waveform, intensity andvoltage of EA stimulation. There is no study that what is more effective the EA on Yin or Yang meridians to spastic patients afterstroke in traditional concept. So we compared the effect between Yin and Yang meridians EA to the stroke spasticity.Methods :53 spasticity patients with hemiplegic stroke were randomized into two groups. 27 patients were treated by the EA on Yinmeridians for elbow joint spasticity(named Yin EA group). The other 26 patients were treated by the EA on Yang meridians(namedYang EA group). The frequency of stimulation was 2Hz and the intensity was set at a level sufficient to include muscle contractionduring 3 weeks. Outcomes were assessed by modified Ashworth scale, Fugl-Meyer score and modified Barthel index.Result :In terms of spasticity, only Yang meridians group showed statistically significant improved, in terms of motor function, Yin meridiansgroup is significantly more effective than Yang meridians group, and in terms of ADL, comparision between Yin and Yangmeridians group is not significantly meaningful.Conclusion : These results support that the effect of Yin and Yang EA on stroke patients is classified. For antispastic effect the Yin meridians EA is more effective and for motor rehabilitation Yang meridians EA is more effective.

축대칭 선형 점탄성 구조물의 정적 유한요소해석

오근,심우진,Oh Guen,Sim Woo-Jin 한국전산구조공학회 2005 한국전산구조공학회논문집 Vol.18 No.3

본 논문에서는 축대칭 형상의 점탄성 구조물이 정적 하중을 받을 때에 대한 시간영역에서의 유한요소해법의 정식화 과정을 제시한다. 또한, 여러 가지 경계조건을 갖는 점탄성 중공구나 원통 문제들의 변위나 응력 이론해들을 탄성-점탄성 상응원리를 이용하여 유도하고 제시한다. 이때 점탄성 재료는 부피변형이 탄성적이고 전단변형은 3요소로 구성된 표준선형 고체처럼 거동한다고 가정한다. 구대칭, 축대칭 및 평면변형률 유한요소모텔을 이용한 수치결과들을 유도된 이론해들과 비교하여 제시된 유한요소해법과 이론해들의 타당성과 정확성을 보인다. In this paper, the time-domain finite element formulations for axisymmetric linear viscoelastic problems, especially for the viscoelastic hollow sphere and cylinder, under various boundary conditions are presented with the theoretical solutions of them obtained by using the elastic-viscoelastic correspondence principle. It is assumed that the viscoelastic material behaves like a standard linear solid in distortion and elastically in dilatation. Numerical examples are solved based on the spherically symmetric, axisymmetric and plane strain finite element models. Good agreements are obtained between numerical and theoretical solutions, which shows the validity and accuracy of the presented method.

전침이 중풍재활에 미치는 영향에 대한 문헌적 고찰

이종수,심우진,Lee, Jong-Soo,Sim, Woo-Jin 척추신경추나의학회 2002 대한추나의학회지 Vol.3 No.1

Objectives : Electroacupuncture(EA) has been suggested as a treatment for stroke rehabilitation. But whether, how much, by what mechanism and when it is effective has not been answered satisfactorily. Therefore it is important to critically review clinical trials and laboratory researches about EA for stroke rehabilitation. Subjectives : We researched various recent sources of EA for stroke rehabilitation such as medical journals and especially tried to review methodologically best randomized controlled trials(RCTs). Results and Conclusions : 1) EA increases brain plasticity, activity, blood flow and secretion of neuropeptides in CNS. 2) EA is significantly effective at the case that more than half of the neural motor pathway is reserved. 3) The acupoints, frequncy and intensity of EA should be determined by patient-specific symptoms of stroke. 4) More studies is needed for merdian functions for stroke rehabilitation.

충격압축하중을 받는 횡등방성 중실축의 과도 동적해석

오근,심우진,Oh, Guen,Sim, Woo-Jin 한국전산구조공학회 2007 한국전산구조공학회논문집 Vol.20 No.5

원형축이 축방향으로 충격하중을 받으면 외경에서 반사된 파가 축의 중앙으로 집중되어 순간적으로 큰 응력이 발생하게 된다. 본 연구에서는 여러 가지 충격 축하중을 받는 횡등방성 반-무한 원형축을 대상으로 중실축 내의 종방향 응력전파를 축대칭 유한요소법과 Houtolt 시간적분법을 이용하여 프로그램을 작성하고 수치적으로 해석하여 그 결과를 횡등방성 재료의 재료구성비에 따라 자세히 설명한다. 제시된 해법의 타당성은 본 논문 수치 결과와 기 해석된 다른 해법에 의한 수치결과의 비교를 통해 검증된다. 여러 종류의 충격하중들에 따른 파동의 결과를 2차원, 3차원적으로 제시하여 축응력 전파를 이해하는데 기본 자료가 되도록 하였다. 또한 유한요소법을 이용하여 수치해석을 함에 있어 정확한 수치결과를 얻기 위한 무차원 동특성 시간변수에 대해 기술하였다. Elastic wave propagations in the semi-infinite transversely isotropic cylinder under various kinds of longitudinal impact loads are analyzed using the axisymmetric finite element method and Houbolt time-integration scheme. For which the finite element program is newly constructed and verified through the comparison of present numerical results with those by other researchers. E-type glass-epoxy composite cylinders with different fiber volume fractions are adopted and studied in detail with dynamic responses of the isotropic cylinder. Three dimensional wave motions are given in graphic form to show the realistic view of the wave propagation. Nondimensionalized dynamic characteristic variables which relate the size of finite element mesh, the time step, and the wave speed are presented for obtaining accurate and stable numerical results.

실리콘 중공 가스켓의 구조적 특성에 관한 연구

이승하,이태원,심우진,Lee, Seung-Ha,Lee, Tae-Won,Sim, Woo-Jin 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.10

In this paper, the deformed shape, the contact forces and the load-displacement curves of the real hollow gasket made of silicon rubber are analyzed using a commercial finite element program MARC. In the numerical analysis, the silicon rubber is assumed to have the properties of the geometric and material nonlinearity and the incompressibility, and the hyperelastic constitutive relations of that material are represented by the generalized Mooney-Rivlin and Ogden models. The outer frictional contact between the hollow gasket and the groove of rigid container and the inner self-contact of the hollow gasket are taken into account in the course of numerical computation. Experiments are also performed to obtain the material data for numerical computation and to show the validity of the mechanical deformation of the hollow gasket, resulting in good agreements between them.

단순방사선 검사상 주관절 외상과염과 경추 척추증의 관계

윤우석,한순현,이종수,심우진,Youn, You-Suk,Han, Soon-Hyun,Lee, Jong-Soo,Sim, Woo-Jin 척추신경추나의학회 2002 대한추나의학회지 Vol.3 No.1

Objectives : To study that lateral epicondylitis(tennis elbow) is related with cervical spondylosis. Subjects : The study was composed of 25 patients of lateral epicondylitis(LEP group) and 25 normal control group(CON group). Method : Simple radiologic scale was compared such as cervical lordotic angle, grading for disc degeneration. Pavlov ratio and Intervertebral body Index Results : Cervical lordotic angle and disc degeneration is not significantly different. And Pavlov ratio and intervertebral body index is significantly decrease in the LEP group. Conclusion : The cervical spondylosis is related with ocuuring lateral epicondylitis.