• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.3
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• pp.187-195
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• 2024

This paper presents two-dimensional boundary value problems of the stress-based gradient elasticity within the smoothed finite element method (S-FEM) framework. Gradient elasticity is introduced to address the limitations of classical elasticity, particularly its struggle to capture size-dependent mechanical behavior at the micro/nano scale. The Ru-Aifantis theorem is employed to overcome the challenges of high-order differential equations in gradient elasticity. This theorem effectively splits the original equation into two solvable second-order differential equations, enabling its incorporation into the S-FEM framework. The present method utilizes a staggered scheme to solve the boundary value problems. This approach efficiently separates the calculation of the local displacement field (obtained over each smoothing domain) from the non-local stress field (computed element-wise). A series of numerical tests are conducted to investigate the influence of the internal length scale, a key parameter in gradient elasticity. The results demonstrate the effectiveness of the proposed approach in smoothing stress concentrations typically observed at crack tips and dislocation lines.

• The Korean Journal of Rheology
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• v.1 no.1
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• pp.5-11
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• 1989

슬릿트나 관형의 흐름에서 유체의 유변학적 성질을 측정하기 위해서는 벽면에서의 압력구배를 알아야한다. 벽면에서의 압력측정은 특히 관형의 경우 압력구멍의 존자가 불가 피하다. 압력구멍에 의한 오차에 대한 이론적인 고찰이 있었지만 사용된 몇가지 가정이 실 험적인 과찰과 일치하지 않아 이들 이론에 대한 강한 의문을 제기하고 한다. 한편 실험적인 결과는 묽은 고분자 용액인 경우 측정압력에 대한 상대적인 압력구멍 오차가 무시할 수 없 을 정도로 크다. 압력구멍 오차는 압력구멍의 크기, Reynolds 수 (점성) 및 Weissenberg 수 (탄성)의 함수로 나타나고 있다. 그러나 농도가 비교적 높은 고분자 용액이나 용융체는 상대 적으로 무시할 수 있을 정도의 압력구멍 오차를 나타낸다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.235-240
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• 2011

A flexible hose attached to a mother ship experiences various motions that depend on the movement of the mother ship and that of underwater vehicle. Although the motion of the hose is a very important factor that determines how a mother ship should be steered in a real situation, it is difficult to experimentally obtain information about the hose motion. Therefore, we study the motion of the hose analytically. The ANCF(absolute nodal coordinate formulation) was used to model the hose, because this formulation can relax the Euler-Bernoulli theory and the Timoshenko beam theory and allow the deformation of the cross section. The mother ship is assumed to be a rigid body with 6 degrees of freedom. The motion of the hose is predominantly affected by the behavior of the mother ship and by the fluid flow.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.779-789
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• 1998

In this paper, the thermal shock responses of collinear cracks in a layered medium are investigated based on the uncoupled, quasi-static plane thermoelasticity. The medium is modeled as a bonded structure composed of a surface layer and a semi-infinite substrate. Between these two dissimilar homogeneous constituents, a functionally graded interfacial zone exists with the nonhomogeneous features of continuously varying thermoelastic properties. Three cracks are assumed to be present in the layered medium, one in each one of the constituent materials, aligned collinearly normal to the nominal interfaces. A system of singular integral equations is solved, subjected to the forcing terms of equivalent transient thermal tractions acting on the locations of cracks via superposition. Main results presented are the transient thermal stress intensity factors to illustrate the parametric effects of various geometric and amterial combinations of the medium with the thermoelastically graded interfacial zone and the collinear cracks.

• Journal of the Korea Concrete Institute
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• v.13 no.4
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• pp.336-345
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• 2001

The construction of underwater structures has been increased, but underwater concrete hassome problems of quality deterioration and contamination around in-situ of civil and architecture; therefore, new materials and methods for them are demanded. In this paper in-situ application of underwater antiwashout concrete which is manufactured for trio purpose of not only decreasing suspended solids and the heat of hydration but also increasing long term strength was studied. In the case of mock-up test(Ⅰ), when underwater antiwashout concrete, whose slump flow was 58 cm, was placed in the mock-up test at a speed of 24 ㎥/hr, it took about a minute to flow to the side wall, and the surface was maintained at horizontal level. In this case, compressive strength of the core specimens in each section was higher than the standard design compressive strength of 240 kgf/㎠. In the case of mock-up test(II), pH value and suspended solids of high strength underwater antiwashout concrete were 10.0∼11.0 and 51 mg/ℓ at 30 minutes later, initial and final setting time were about 30, 37 hr, and the slump flow of that was 53$\pm$2 cm. In the placement at a speed of 27 ㎥/hr, there was no large difference in flowing velocity, with or without reinforcement and flowing slope was maintained at horizontal level. In this case, compressive strength and elastic modulus of the core specimens somewhat decreased as flowing distance was far : however, those of central area showed the highest value.