• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.4
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• pp.57-66
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• 2002

본 연구는 굽힘 하중하에서 탄성평판 구조 해석을 위한 경계적분방법 구성을 주목적으로 하고 체계적인 모듈화시스템 개발의 첫 이론 부분을 확립하였다. 굽힘 문제에서의 4개의 고유변수인 처짐, 기울기, 굽힘모우멘트, 상당 전단력의 항으로 경계적분방정식을 구성하였다. 물리적인 의미를 갖는 두 새로운 핵함수 도입으로 구성된 이들 적분방정식은 경계요소 구성시 나타나는 특이거동의 문제점을 간단한 두 탄성해에 의해 정규화 시켰으며 수치 적분 과정도 Cauchy 주치 적분 수렴성에서의 특별취급과는 달리 효율적으로 일반화시켰다. 경계적분식의 수치해석방법을 서술하였으며 집중하중하의 비대칭문제의 근사수치해를 도시하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.2
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• pp.11-22
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• 1989

The finite element utilizing isoparametric plate element is applied for the elastic analysis of straight box girder bridges. A continuous box girder is analyzed as an example to verify the validity and accuracy of this method. It is indicated that the deflections and longitudinal stresses obtained by this method agree well with those from the orther methods. This theory may, therefore, be directly used as an efficient tool to analyze and design box girder bridges subjected to arbitrary loading and boundary conditions.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1254-1258
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• 2007

Electro-active polymer (EAP), one of the smart materials, is a new alternative offering ultra-precise movements and bio-compatibility. We present the results of the design, fabrication, and performance evaluation of a fabricated diaphragm-type polymer actuator using segmented polyurethane(SPU). This paper illustrates the relationship between the elastic modulus and maximum deflection as a key property of the Maxwell stress effect and also presents the relationship between the dielectric constant and maximum deflection as a key property of the electrostriction effect, especially in polymer actuators using SPU. A diaphragm-type actuator was used to induce an equation of the vertically distributed load by using a fully clamped circular plate as the boundary condition. To verify the equation, the results were compared to the data measured from load cell. In the near future, a low-cost check valves and bio-robot can be applied by its actuators.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1830-1835
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• 2007

In the present work, the effect of strength mismatch on plastic limit loads is quantified for strength-mismatched plates with constant-depth surface cracks under tension, via three-dimensional, small strain elastic-perfectly plastic finite element analyses. Relevant variables related to plate and crack geometries are systematically varied, in addition to the weld width. An important finding is that a parameter related to the weld width-to-ligament ratio is proposed, based on which limit loads can be uniquely quantified. The proposed limit load solutions is a valuable input to estimate nonlinear fracture mechanics parameters based on the reference stress approach.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.386-391
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• 1998

The effect of the changes in parameter angles(precone, droop, sweep) on the lead-lag damping was focused on. Experiment was made with hingeless 4-blade rotors and NACA 0012 airfoil. For the measurement of the rotating natural frequencies and lead-lag damping, non-rotating swash plate was oscillated at the regressing lag mode frequency and the data were acquired after the excitation was cut off. Analysis was made using a finite element formulation based on Hamilton's principle. The main blade is assumed as elastic beams. Quasi-steady strip theory is used to obtain aerodynamic forces, and non-circulatory forces are also included.

• Structural Engineering and Mechanics
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• v.76 no.2
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• pp.239-250
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• 2020

This paper deals with free vibration of plates with steps and internal line supports by using a modified matched interface and boundary (MMIB) method. Different kinds of interfaces caused by steps, rigid and elastic line supports and their combinations are taken into account. Detailed MMIB procedures for dealing with these different interfaces are presented. Various examples are chosen to illustrate the accuracy and convergence of MMIB method. Numerical results show that the proposed MMIB is a highly accurate and convergent approach for solving the title issue. This study will extend the application range of MMIB method.

• Steel and Composite Structures
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• v.11 no.2
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• pp.115-130
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• 2011

Considering the randomness of material parameters in the laminated composite plate, a scheme of stochastic finite element method to analyze the displacement response variability is suggested. In the formulation we adopted the concept of the weighted integral where the random variable is defined as integration of stochastic field function multiplied by a deterministic function over a finite element. In general the elastic modulus of composite materials has distinct value along an individual axis. Accordingly, we need to assume 5 material parameters as random. The correlations between these random parameters are modeled by means of correlation functions, and the degree of correlation is defined in terms of correlation coefficients. For the verification of the proposed scheme, we employ an independent analysis of Monte Carlo simulation with which statistical results can be obtained. Comparison is made between the proposed scheme and Monte Carlo simulation.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.6
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• pp.164-171
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• 2008

A modified generalized particle algorithm, MGPA, was suggested to improve the computational efficiency of standard SPH method in numerical analysis of high speed impact behavior. This method uses a numerical failure mechanism than material failure models to describe the target penetration. MGPA algorithm was more effective to describe the impact phenomena and new boundaries produced during the calculation process were well recognized and treated in the target penetration problem of a bullet. When bullet perforation problems were analyzed by this method, MGPA algorithm calculation gives the stable numerical solution and stress oscillation or particle penetration phenomena were not shown. The error range in ballistic velocity limit is less than $2{\sim}13%$ for various target thickness.

• Journal of Korean Society of Steel Construction
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• v.9 no.1 s.30
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• pp.3-11
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• 1997

Laminated composite shells exhibit properties comsiderably different from those of the single-layer shell. Thus, to obtain the more accurate solutions to laminated composite shells ptoblems, effects of shear strain should be condidered in analysis of them. A higher-order shear deformation theory requires no shear correction coefficients. This theory is used to determine the buckling loads of elastic shells. The theory accounts for parabolic distribution of the transverse shear through the thickness of the shell and rotary inertia. Exact solutions of simply-supported shells are obtained and the results are compared with the exact solutions of the first-order shear deformation theory, and the classical theory. The present theory predicts the buckling loads more accurately when compared to the first -order and classical theory.

• Journal of Welding and Joining
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• v.20 no.2
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• pp.50-58
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• 2002

Residual stress is generated in the structures as a result of irregular elastic-plastic deformation during fabrication processes such as welding, heat treatment, and mechanical processing. There are several factors attributed to the origin of residual stresses, tensile or compressive. The stresses can be determined by destructive ways or nondestructive ways using X-ray or neutron diffraction. Although X-ray diffraction is a well established technique, it is practically limited to near-surface stresses. Neutrons penetrate easily into most materials and neutron diffraction permits non-destructive evaluation of lattice strain within the bulk of large specimens because the radiation is more deeply penetrating for metallic engineering components. This paper presented application of neutron diffraction technique to the residual stress measurement using 20 mm thick welded stainless steel plate($100{\times}100 \textrm{mm}^2$)