• Composites Research
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• 제32권5호
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• pp.249-257
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• 2019

In this paper, the buckling behavior of triaxially braided circular arch with monosymmetric open section subjected to three-point bending was studied experimentally and numerically. First, test specimens were manufactured using vacuum assisted resin transfer molding (VARTM). Then the specimen was tested under three-point bending to determine the ultimate buckling strength. Before performing the numerical analysis, effective material properties of the braided composite were obtained through micro-meso scale analysis virtual testing validated with available test results. Then linear buckling analysis and geometrically non-linear post buckling analysis, established to simulate the test setup, were performed to study the buckling behavior of the composite frame. Analysis results were compared with experimentally obtained ones for verification. The effect of manufacturing defects of tow misalignment, irregular surface and resin rich region, and uncertainties during test setup were studied using numerical models. From the numerical analyses performed it was observed that both manufacturing defect and uncertainties had effect on the buckling behavior and strength.

• 한국생산제조학회지
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• 제7권2호
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• pp.23-28
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• 1998

In this paper, the experimental and numerical results of buckling loads for laminated composite plates are compared. Using boundary conditions of buckling test are all fixed supports. Experiments were conducted for plates with fiber angles $ heta$=30$^{\circ}$, 45$^{\circ}$,60$^{\circ}$ and aspect ratio a/b=0.8. Experimental results were obtained from load-deflection curves of buckling test. Numerical methods were presented to evaluate buckling loads, using structural analysis results from ANSYS.

• Structural Engineering and Mechanics
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• 제87권5호
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• pp.419-429
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• 2023

This study conducts numerical analyses of a thin-walled composite cylinder under axial compression and internal pressure of 10 kPa. Numerical vibration correlation technique and nonlinear postbuckling analyses are conducted using the nonlinear finite element analysis program, ABAQUS. The single perturbation load approach and measured imperfection data are used to represent the geometric initial imperfection of thin-walled composite cylinder. The buckling knockdown factors are derived using present initial imperfection and analysis methods under axial compression without and with the internal pressure. Furthermore, the buckling knockdown factors are compared with the buckling test and computation time are calculated. In this study, derived buckling knockdown factors in present study have difference within 10% as compared with the buckling test. It is shown that nonlinear postbuckling analysis can derive relatively accurate buckling knockdown factor of present thin-walled cylinders, however, numerical vibration correlation technique derives reasonable buckling knockdown factors compared with buckling test. Therefore, this study shows that numerical vibration correlation technique can also be considered as an effective numerical method with 21~91% reduced computation time than nonlinear postbuckling analysis for the derivation of buckling knockdown factors of present composite cylinders.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.254-260
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• 2000

The spacer grid is one of the main structural components in fuel assembly, which supports the fuel rods, guides cooling water, and protects the fuel assembly from the external impact load such as earthquakes. The nonlinear dynamic impact analysis is conducted by using the finite element code ABAQUS/Explicit. Boundary condition for dynamic analysis is well applied to the test condition. Simulation results also similarly predict the local buckling phenomena. In addition to the buckling parameter, the local buckling cause is examined by both simulation and test method. It is found to correspond well with the test results. Impact tests are also carried out for some specimens of the spacer grid in order to compare the results between the test and the simulation. This test is accomplished by a free fall dummy weight onto the specimen. From this test, only the uppermost and lowermost layers of the multi-cell are buckled, which implies the local buckling at the weakest point of the grid structure.

• 한국안전학회지
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• 제23권4호
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• pp.67-71
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• 2008

Formwork is a temporary structure that supports its weight and that of fresh concrete as well as construction live loads. Slab formwork consists of sheathing, stringer, hanger and shore. In construction site, pipe supports are usually used as shores which are consisted of the slab formwork. In this study, compressive strength of 80 pipe supports was measured by knife edge test and plate test. Buckling load of pipe supports was analyzed by structural analysis program(MlDAS). Theoretical buckling load with/without initial deformation was got by theoretical analysis. According to these results, buckling load which was analyzed by structural analysis program(MlDAS) was larger than compressive strength of knife edge test and plate test. Theoretical buckling load without initial deformation was larger than compressive strength of knife edge test and plate test. But Theoretical buckling load with initial deformation was lower than compressive strength of knife edge test and plate test. Initial deformation equation for test method according to the pipe support length was suggested. Therefore, the present study results will be used to design the slab formwork safely.

• Nuclear Engineering and Technology
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• 제33권1호
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• pp.93-101
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• 2001

The spacer grid is one of the main structural components in the fuel assembly, which supports the fuel rods, guides cooling water, and protects the system from an external impact load, such as earthquakes. Therefore, the mechanical and structural properties of the spacer grids must be extensively examined while designing them. In this paper, a numerical method for predicting the buckling strength of spacer grids is presented. Numerical analyses on the buckling behavior of the spacer grids are performed for a various array of sizes of the grids considering that the spacer grid is an assembled structure with thin-walled plates and imposing proper boundary conditions by nonlinear dynamic finite element method using ABAQUS/Explicit. Buckling tests on several numbers of specimens of the spacer grid were also carried out in order to compare the results between the test and the simulation result. The drop test is accomplished by dropping a carriage on the specimen at a pre-determined position. From this test, the specimens are buckled only at the uppermost and the lowermost layer among the multi-cells, which is similar to the local buckling at the weakest point of the grid structure. The simulated results also similarly predicted the local buckling phenomena and were found to give good correspondence with the experimental values for the thin-walled grid structures.

• 한국공간구조학회논문집
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• 제23권1호
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• pp.61-68
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• 2023

Buckling Restrained Braces can not only express the strength considered at the time of design, but also reduce the seismic load by energy dissipation according to the plastic behavior after yield deformation of the steel core. The physical characteristics and damping effect may be different according to the buckling prevention method of the steel core by the lateral restraint element. Accordingly, in this study, To compare hysteresis characteristics, Specimen(BRB-C) filled with mortar, specimen(BRB-R) combined with a buckling restraint ring and Specimen(BRB-EP) filled with engineering plastics was fabricated, and a cyclic loading test was performed. As a result of the cyclic loading test, the maximum compressive strength, cumulative energy dissipation and ductility of each test specimen was similar. But in case of the cumulative energy dissipation and ductility, BRB-C filled with the mortar specimen showed the lowest. This is considered to be because the gap between the steel core and the reinforcing material for plastic deformation was not uniformly formed by pouring mortar around the core part.

• 한국항공우주학회지
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• 제33권4호
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• pp.35-40
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• 2005

압축하중을 받는 실린더형 구조물에 대한 보강방법으로는 스킨-스트링거, 격자보강 형상 등 여러 종류가 있다. 그 중 isogrid 형상은 정삼각형형태의 보강대가 반복되는 보강구조로서 여러 가지 조합하중 및 집중하중에 대한 대처능력이 우수한 보강구조이다.본 논문에서는 격자보강 구조 중 isogrid 구조에 대한 압축 좌굴시험 및 비선형 해석을 수행하였다. Isogrid 패널은 두께가 11.43 mm, 높이가 660 mm, 외경이 2.4 m이며 70도의 원호를 이루는 알루미늄합금 일체형 구조이다. 시편에 대한 압축 좌굴시험을 통하여 국부좌굴강도, 전체좌굴강도, 국부좌굴후의 거동 등을 확인하였다. 또한 MSC/MARC를 이용한 비선형 FEM 해석을 수행하여 구조시험 결과와 비교하였다. 해석 시에는 패널의 소성 가공 시 발생한 형상공차를 고려하였다. 시험결과와 해석결과는 좌굴하중 및 좌굴모드가 모두 비교적 일치하였다.

• 한국항공우주학회지
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• 제50권2호
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• pp.75-82
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• 2022

내부 압력과 압축하중을 받는 발사체 추진제 탱크 구조의 좌굴 하중을 비파괴적으로 예측할 수 있는 기법이 필요하다. 기하학적 초기 결함이 존재하는 단순 원통 구조의 전역 좌굴 하중은 좌굴이 발생하지 않는 범위에서의 고유진동수-압축하중의 상관관계를 이용한 Vibration correlation technique (VCT)을 사용하여 비파괴적으로 예측 가능하다. 본 연구에서는 내부 압력과 압축하중을 동시에 받는 추진제 탱크 구조 형태인 얇은 금속재 단순 원통 구조의 진동 및 좌굴 시험을 수행하였고 VCT를 이용하여 전역 좌굴 하중을 예측하였다. 두께가 얇은 구조의 진동 시험을 위해 스피커를 이용한 비접촉식 가진 방법을 이용하였고 응답은 고분자 압전 센서(PVDF)로 측정하였다. VCT로 예측된 전역 좌굴 하중을 좌굴 시험에서 측정된 좌굴 하중과 비교하여 비파괴적 전역 좌굴 하중 예측 기법을 검증하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.265-272
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• 1997

In this paper the bending collapse characteristics of 60 series Al rectangular tubes were studied with a pure bending collapse test rig which could apply the pure bending moment, there occured three kinds of bending collapse modes - local buckling, delayed buckling, tensile failure - depending on the b/t(width/thickness) ratio and material properties. Experiment results are compared with the results of finite element method.