• 대한기계학회논문집A
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• 제35권11호
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• pp.1437-1443
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• 2011

선박 건조를 위한 기본 자재인 후판은 압연공정을 통해 생산된다. 본 논문에서는 후판압연 중에 발생하는 폭방향 휨을 일으키는 비대칭 요인들을 제어할 수 있는 설정모델을 제시한다. 일련의 삼차원 유한요소해석을 통해서 휨과 비대칭 요인 사이의 관계를 예측한다. 그 관계를 무차원 변수로 이루어진 선형 방정식으로 수식화 시킴으로써 설정모델을 도출한다. 소재 폭방향으로 두께 편차와 온도차이가 있는 경우에 대해서 파이롯트 압연 시험으로 통해서 설정모델의 정도를 검증한다. 본 모델에 의해 예측된 휨 곡률이 각각의 비대칭 요인들에 의해 측정된 휨 곡률과 상당히 일치하는 결과를 보여 주었다.

• Structural Engineering and Mechanics
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• 제44권1호
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• pp.35-49
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• 2012

A series of fatigue test were carried out on scarfed lap joints (SLJ) using in airfoil siding to explore the effect of structural details, such as rows of rivets, lap angles, on its fatigue performance. Finite element (FE) analysis was employed to explore the effect of lap angle on load transfer and the stress evolution around the rivet hole. At last, the fatigue lives were predicted by nominal stress approach and critical plane approach. Both of the test results and predicted results showed that fatigue life of SLJ was remarkably increased after introducing lap angle into the faying surface. Specimen with the lap angle of $1.68^{\circ}$ exhibits the best fatigue performance in the present study.

• Computers and Concrete
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• 제19권5호
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• pp.477-488
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• 2017

In this paper, an innovative technique for finite element (FE) modeling of steel tube-confined concrete (STCC) columns with active confinement under axial compressive loading is presented. In this method, a new constitutive model for the stress-strain relationship of actively-confined concrete is proposed. In total, 14 series of experimental STCC stub columns having active confinement were modeled using the ABAQUS software. The results obtained from the 3D model including the compressive strength at the initial peak point and failure point, as well as the axial and lateral stress-strain curves were compared with the experimental results to verify the accuracy of the 3D model. It was found that there existed a good agreement between them. A parametric study was conducted to investigate the effect of the concrete compressive strength, steel tube wall thickness, and pre-stressing level on the behavior of STCC columns with active confinement. The results indicated that increasing the concrete core's compressive strength leads to an increase in the compressive strength of the active composite column as well as its earlier failure. Furthermore, a reduction in the tube external diameter-to-wall thickness ratio affects the axial stress-strain curve and the confining pressure, while increasing the pre-stressing level has a negligible effect on the two.

• 한국터널지하공간학회 논문집
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• 제8권1호
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• pp.41-51
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• 2006

본 논문에서는 숏크리트 라이닝 충간 부착성이 숏크리트 라이닝의 하중지지력에 미치는 영향에 대한 내용을 다루었다. 이를 위해 축소 모형시험과 유한요소해석을 병행하여 더블쉘 터널 시공시 숏크리트 충간 부착성과 숏크리트 라이닝의 하중지지 특성과의 관계를 알아보았다. 연구결과 NATM의 더블쉘 구소와 같이 라이닝 층간 부착이 확보되지 않는 경우에는 이완하중 작용시 응력이 집중되는 경향을 보이는 것으로 나타났으며, 토피고 증가에 따라 그 차이가 증가하는 것으로 나타났다. 본 연구결과를 종합하여 설계와 시공시 고려하여야 할 주안점을 제시하였다.

• Advances in Computational Design
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• 제3권1호
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• pp.71-86
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• 2018

Thin-walled cross-sections can be optimized to enhance their resistance and progress their behaviour, leading to more competent and inexpensive structural system. The aim of this study is to afford a methodology that would facilitate progress of optimized cold formed steel (CFS) column section with maximum ultimate strength for practical applications. The proposed sections are designed to comply with the geometrical standards of pre-qualified column standards for CFS structures as well as with the number of industrialized and practical constraints. The stiffening evaluation process of CFS lipped channel columns, a five different cross section are considered. The experimental strength and behaviour of the proposed sections are verified by using the finite element analysis (FEA). A series comprehensive parametric study is carried out covering a wide range of section slenderness and overall slenderness ratio of the CFS column with and without intermediate web stiffeners. The ultimate strength of the sections is determined based on the Direct Strength Specification and other design equation available from the literature for CFS structures. A modified design method is proposed for the DSM specification. The results indicate that the CFS column with complex edge and intermediate web stiffeners provides an ultimate strength which is up to 78% higher than standard optimized shapes with the same amount of cross sectional area.

• Computers and Concrete
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• 제20권5호
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• pp.583-593
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• 2017

Applications of fibre-reinforced polymer (FRP) composites for retrofitting, strengthening and repairing concrete structures have been expanded dramatically in the last decade. FRPs have high specific strength and stiffness compared to conventional construction materials, e.g., steel. Ease of preparation and installation, resistance to corrosion, versatile fabrication and adjustable mechanical properties are other advantages of the FRPs. However, there are major concerns about long-term performance, serviceability and durability of FRP applications in concrete structures. Therefore, structural health monitoring (SHM) and damage detection in FRP-retrofitted concrete structures need to be implemented. This paper presents a study on investigating the application of Rayleigh wave for detecting debonding defect in FRP-retrofitted concrete structures. A time-of-flight (ToF) method is proposed to determine the location of a debonding between the FRP and concrete using Rayleigh wave. A series of numerical case studies are carried out to demonstrate the capability of the proposed debonding detection method. In the numerical case studies, a three-dimensional (3D) finite element (FE) model is developed to simulate the Rayleigh wave propagation and scattering at the debonding in the FRP-retrofitted concrete structure. Absorbing layers are employed in the 3D FE model to reduce computational cost in simulating the practical size of the FRP-retrofitted structure. Different debonding sizes and locations are considered in the case studies. The results show that the proposed ToF method is able to accurately determine the location of the debonding in the FRP-retrofitted concrete structure.

• Journal of Mechanical Science and Technology
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• 제18권12호
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• pp.2158-2173
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• 2004

In this paper, the higher order terms in the crack tip stress fields are investigated macroscopically for more realistic assessment of structural material behaviors. For reactor pressure vessel material of A533B ferritic steel, effects of crack size and temperature have been evaluated using 3-point SENB specimens through a series of finite element analyses, tensile tests and fracture toughness tests. The T-stress, Q-parameter and q-parameter as well as the K and J-integral are calculated and mutual relationships are investigated also. Based on the evaluation, it has proven that the effect of crack size from standard length (a/W=0.53) to shallow length (a/W=0.11) is remarkable whilst the effect of temperature from -20$^{\circ}C$ to -60$^{\circ}C$ is negligible. Finally, the cleavage fracture toughness loci as a function of the promising Q-parameter or q-parameter are developed using specific test results as well as finite element analysis results, which can be applicable for structural integrity evaluation considering constraint effects.

• 대한기계학회논문집A
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• 제31권3호
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• pp.304-312
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• 2007

The objective of this study is to develop a local failure criterion for a wall thinning defect of piping components. For this purpose, a series of tensile tests was performed using several types of simulated specimens with different stress states, including smooth round bar, notched round bar (five different notch radii), and grooved plate (three different groove radii). In addition, finite element (FE) simulations were performed on the simulated specimen tests and the results were compared with the test results. From the comparisons, the equivalent stress and strain corresponding to maximum load and final failure of notched specimens were proposed as failure criteria under tensile load. The criteria were verified by employing them to the estimation of failure of grooved plate specimens that simulate the wall thinning defect. It showed that the proposed criteria accurately estimate the maximum load and final failure of grooved plate specimen tests.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 춘계 학술대회논문집
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• pp.145-155
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• 1998

A computer code has been developed for the computation of the viscous flow around a ship model with the free surface. In this code, the incompressible Reynolds-averaged Navier-Stokes equations are solved numerically by a finite difference method which employes second-order finite differences for the spatial discretization and a four-stage Runge-Kutta scheme for the temporal integration of the governing equations. For the turbulence closure, a modified version of the Baldwin-Lomax model is exploited. The location of the free surface is determined by solving the equation of the kinematic free-surface condition using the Lax-Wendroff scheme and the boundary-fitted grid is generated at each time step so that one of the grid surfaces always coincides with the free surface. An inviscid approximation of the dynamic free-surface boundary condition is applied as the boundary conditions for the velocity and pressure on the free surface. To validate the computational method and the computer code developed in the present study, the numerical computations are carried out for both Wigley parabolic hull and Series 60 $C_B=0.6$ ship model and the computational results are compared with the experimental data.

• 한국기계가공학회지
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• 제17권4호
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• pp.169-176
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• 2018

Removal of angular deformation induced during the welding of butt joints in thick steel plates needs expert skill and is costly. To reduce deformation, proper joint designs are studied with a prediction of deformation prior to welding. However, as the thickness of a plate increases, a predictive analysis of the welding process is more difficult, especially if there is an increase in the number of welding passes in the joint. In this study, a numerical model with the finite element method (FEM) was developed to analyze the angular deformation in the multi-pass welding of butt joints of plates made of AH32 steel that had a thickness of up to 100 mm. A series of numerical simulations were then performed based on the developed model to predict the deformations for thick plates. With the results obtained by the analyses, this study suggested optimal X-shape grooves for the butt joints of thick plates to minimize the angular deformation. As the thickness of the plate increased to 100 mm, the ratio of the depth of the front-side groove to that of the back-side groove should be gradually increased to nearly 1:3.