• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.427-431
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• 1986

3점 굽힘 시험편, 중앙균열 인장 시험편, 콤팩트 인장 시험편에 대한 J적분식을 하나의 일반화된 형태로 유도한다. 이 일반식은 Eftis와 Liebowitz에 의해 제안된 하중과 하중점 변위 사이의 관계와 Sumpter에 의한 탄성과 소성성분 J적분의 중첩개념을 이용함으로써 유도된다. 일반식에 포함된 .eta.계수를 위 3가지 시험편에 대해서 결정한다. 위 3가지 시험편에 대한 J적분의 최종식은 하중과 하중점 변위곡선 아래의 면적을 측정하지 않아도 되는 형태로 나타난다. 본 연구의 결과식은 Landes등에 의한 실험치와 비교하여 매우 잘 일치함을 보인다.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.4 s.97
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• pp.178-188
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• 1999

충격하중을 받는 시험편 높이의 1/4 길이의 notch를 가진 3점 굽힘시험편들의 기계적 거동에 관한 컴퓨터 시뮬레이션을 하고 이 시뮬레이션에 대한 실험적 검증도 하여 그 타당성을 입증하였다. 시험편들의 양쪽 가장자리(지지점)에서 작용되어지는 여러 가지의 하중속도에 대한 경우들과 탄소성 von Mises 재질인 모델들을 시뮬레이션에 포함시켰으며 이들에 대한 결과들을 간극 개구 변위, 반력, 크랙선단 개구 변위 및 변형률등이 속도에 의존되는 재질(점소성 재질)에 대한 시뮬레이션 결과와 비교하였다. 또한 여러가지의 동적 하중을 받는 상황하에서의 안정성이 본 연구의 시뮬레이션을 통하여 비교되었으며 그 차이점들이 규명되었다.

• Composites Research
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• v.12 no.3
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• pp.66-74
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• 1999

A modified mixed mode bending test was performed to investigate the mixed mode delamination for carbon/epoxy composite material. Various mixed mode ratios could be produced by changing the applied load position on the loading lever and the bending load position on the specimen. The modified mixed mode bending test was analyzed to obtain strain energy release rates using beam theory, compliance method and finite element method, This results were in good agreement with the experimental result, which confirmed the validity of this test.

• Journal of the KSME
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• v.18 no.3
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• pp.57-61
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• 1978

안전벨브설비의 기계적설계와 해석에관련된 가장 중요한 고려사항중의 하나는 설비내의 임계점을 찾아내고 그 점에서의 모우멘트를 계산하는 것이다. 만약 굽힘모우멘트를 적절히 계산하지 않으 연 기술기순에 포함된 하중 및 응력기준에 합격할 수 없을 것이다. 이 모우멘트를 결정하는데 최 소한도 본 부록의 2부에 설명된 다음 하중들을 포함함이 바람직하다. 1. 열팽창 2. 사하중 3. 지진 4. 벨브 송출로부터의 반작용력 5. 기타 기계적하중 안전밸브설비의 핵석에서 교차점, 엘보우, 변이점등을 포함한 모든 중요단면 및 기타 관련된 배 관, 용기및 배관설비와 상호작용하는 그들의 지지점들을 포함함이 바람직하다. 안전밸브설비와 그 에 관련된 배관을 직선 또는 곡선 요소들을 연결된 하나의 통합된 질량계로서 모형화하는 것이 가장 적절하다.

• Composites Research
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• v.33 no.3
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• pp.108-114
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• 2020

Piecewise Integrated Composite (PIC) beam is composed of different stacking against loading type depending upon location. The aim of current study is to assign robust stacking sequences against external loading to every corresponding part of the PIC beam based on the value of stress triaxiality at generated reference points using the k-NN (k-Nearest Neighbor) classification, which is one of representative machine learning techniques, in order to excellent superior bending characteristics. The stress triaxiality at reference points is obtained by three-point bending analysis of the Al beam with training data categorizing the type of external loading, i.e., tension, compression or shear. Loading types of each plane of the beam were classified by independent plane scheme as well as total beam scheme. Also, loading fidelities were calibrated for each case with the variation of hyper-parameters. Most effective stacking sequences were mapped into the PIC beam based on the k-NN classification model with the highest loading fidelity. FE analysis result shows the PIC beam has superior external loading resistance and energy absorption compared to conventional beam.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1387-1394
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• 2014

In a photoelastic experiment, it is necessary to know the material stress fringe constant of the photoelastic specimen to determine the stresses from the measured isochromatic fringe orders. The material stress fringe constant can be obtained using a simple tension specimen and/or a circular disk under diametric compression. In these methods, there is generally a need to apply numerous loads to the specimen in response to the relationship of the fringe order. Then, the least squares method is used to obtain the material constant. In this paper, the fringe orders that appear on a four-point bending specimen are used to determine the fringe constant. This method requires four photoelastic fringes obtained from a circular polariscope by rotating the analyzer to 0, ${\pi}/4$, ${\pi}/2$, and $3{\pi}/4$ radians. Using the four-point bending specimen to determine the material stress fringe constant has an advantage because measurements can be made at different locations by applying a constant load. The stress fringe constant measured with this method is within the range suggested by the manufacturer of the photoelastic material.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.6
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• pp.80-87
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• 2020

The currently observed trend in car manufacturing is to increase energy-efficiency by producing lighter cars. This study examines the replacement of particular parts, specifically around the impact beam, with material composites 30% lighter than conventional steel currently used. The shape of the impact beam was determined as the trapezoidal cross-sectional area with central reinforcement, using three-point bending analysis. A prototype was fabricated based on the findings of our study and its performance was evaluated by the three-point bending analysis; 2 ply of aramid applied for its displacement. The performance of the final prototype for the door assembly was evaluated using a side-door strength test, which resulted to measured initial strength of 10.5 KN and intermediate strength of 15.6 KN. This research provides a promising solution for better impact beam manufacturing.

• Journal of Aerospace System Engineering
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• v.11 no.5
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• pp.13-19
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• 2017

In this study, the bending analysis of composite laminates using the classical laminated theory is investigated. A piece-wise linear incremental approach is employed to describe the nonlinear mechanical behavior of the composite laminates, and a 2D strain-based interactive failure theory is employed to predict the ultimate flexural loads. The 3-point bending tests are performed for cross-ply and quasi-isotropic laminates. The analysis results with the failure theory are verified by comparing the analysis findings to the experimental outcome.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.702-705
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• 2005

Metallic sandwich plates with Inner dimpled shell subjected to 3-point bending have been analyzed and then optimized for minimum weight. Inner dimpled shells can be easily fabricated by press or roll with high quality precision and bonded with same material skin sheets by resistance welding or adhesive bonding process. Optimized shape of inner dimple is a hemispherical shell to minimize weight without failure, including face yielding, face buckling and inner dimple buckling. It is demonstrated that bending stiffness of sandwich plate is 2 or 3 times than solid plates with same strength

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.4
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• pp.256-265
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• 2019

In this paper, the progressive damage of an orthogonal grid shell fabricated with plain weave fabric CFRP under bending load was investigated. The orthogonal grids were cured with the bottom composite shell. Progressive damage analysis of an orthogonal grid shell under bending was performed using nonlinear finite element method with Hashin-Rotem failure criterion and Matzenmiller-Lubliner-Taylor(MLT) model. In addition, the three - point bending test for the structure was carried out and the test results were compared with the analysis results. The comparison results of the strain and displacement agreed well. The damage area estimated by the progressive damage analysis were compared with the visual inspection and ultrasonic non-destructive inspection.