• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 추계학술발표회요약집
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• pp.262.1-262
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• 2001

• 대한기계학회논문집A
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• 제23권6호
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• pp.1039-1047
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• 1999

It is necessary to evaluate the fatigue behavior of rail steel under the multi-axial stress state to assure the railway vehicle's safety. For this purpose, the stress analysis to investigate the crack initiation criteria, static failure and fatigue behavior under mixed-mode are performed. The stress analysis results show that the initiation of the transverse fissure depends on the maximum shear stress below the surface. For the mixed mode, the fatigue crack growth behavior which is represented by the projection crack length and comparative S.I.F, ${\Delta}K_v$, shows the more conservative results. Also, its rate is lower than that of the case of the mode I, and this difference decreases with increasing the stress ratio, R.

• 대한토목학회논문집
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• 제14권4호
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• pp.761-769
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• 1994

열차 바퀴의 접촉하중에 의해 레일이 받는 하중형식은 모드 I과 모드 II가 조합된 혼합모드 하중 상태로서 본 연구에서는 레일강의 피로파괴거동을 규명하기 위해 Richard가 개발한 혼합모드 파괴시험편 및 시험 지-그(Jig)를 이용하여 파괴시험을 실시하였으며 그 결과로부터 혼합모드에 대한 용력강도계수의 상관관계를 이용하여 균열성장경로를 평가하고 기제안된 다양한 파괴기준을 비교하였다. 그 결과, 레일강의 균열성장경로는 최대원주응력설과 변형에너지밀도설을 파괴기준은 주변형률설을 따름을 알 수 있었다.

• 펄프종이기술
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• 제31권5호
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• pp.57-72
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• 1999

Traditional theories of the tensile failure of paper have assumed that uniform strain progresses throughout the sheet until an imperfection within the structure causes a catastrophic break. The resistance to tensile elongation is assumed to be elastic , at first, throughout the structure, followed by an overall plastic yield. However, linear image strain analysis (LISA) has demonstrated that the yield in tensile loading of paper is quite non-uniform throughout the structure, Traditional theories have failed to define the flaws that trigger catastrophic failure. It was assumed that a shive or perhaps a low basis weight area filled that role. Studies of the fracture mechanics of paper have typically utilized a well-defined flaw around which yield and failure could be examined . The flaw was a simple razor cut normal to the direction of tensile loading. Such testing is labeled mode I analysis. The included fla in the paper was always normal to the tensile loading direction, never at another orientation . However, shives or low basis weight zones are likely to be at random angular orientations in the sheet. The effects of angular flaws within the tensile test were examined. The strain energy density theory and experimental work demonstrate the change in crack propagation from mode I to mode IIas the initial flaw angle of crack propagation as a function of the initial flaw angle is predicted and experimentally demonstrated.

• 대한기계학회논문집A
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• 제24권4호
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• pp.982-990
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• 2000

The finite element alternating method is extended further for general three dimensional cracks in an isotropic body subjected to the mode I loading. The required analytical solution for a dime dimensional crack in an infinite isotropic body is obtained by solving the integral equations. In order to remove the high singularity in integration, the technique suggested by Keat et al. was used. With the proposed method several example problems are solved in order to check the accuracy and efficiency of the method.

• Journal of Mechanical Science and Technology
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• 제14권9호
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• pp.978-984
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• 2000

The aim of this study is to investigate the ductile fracture behaviour under Mode I loading using SA533B pressure vessel steel. Experiments consist of the Round Notch Bar Test (RNB), Single Edge Crack Bending Test (SECB), and V-Notch Bar Test (VNB). Results from the RNB test were used to tune the damage modelling constant. The other tests were performed to acquire the J-resistance curves and to confirm the damage constants. Microstructural observation includes the measurement of crack profile to obtain the roughness parameter. Finally, simulation using Rousellier Ductile Damage Theory (RDDT) was carried out with 4-node quadrilateral element ($L_c=0.25\;mm$). For the crack advance, the failed element removal technique was adopted with a ${\beta}$ criterion. In conclusion, the predicted simulation using RDDT showed a good agreement with the experimental results. A trial using a roughness parameter was made for a new evaluation of J-resistance curve, which is more conservative than the conventional one.

• Computers and Concrete
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• 제13권4호
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• pp.569-585
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• 2014

In this paper, a four-layer road structure consisting of an edge transverse crack is simulated using three-dimensional finite element method in order to capture the influence of a single-axle wheel load on the crack propagation through the asphalt concrete layer. Different positions of the vehicular load relative to the cracked area are considered in the analyses. Linear elastic fracture mechanics (LEFM) is used for investigating the effect of the traffic load on the behavior of a crack propagating within the asphalt concrete. The results obtained show that the crack front experiences all three modes of deformation i.e., mode I, mode II and mode III, and the corresponding stress intensity factors are highly affected by the crack geometry and the vehicle position. The results also show that for many loading situations, the contribution of shear deformation (due to mode II and mode III loading) is considerable.

• 대한기계학회논문집
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• 제16권12호
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• pp.2226-2240
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• 1992

본 연구에서는 이방성체에 대한 구체적인 코스틱스 실험법을 확립하기 위하여 다음과 같은 연구를 수행 하였다. 첫째, 이방성체에 대한 코스틱스상 및 초기곡선의 사상방정식을 기하광학 및 Sih의 응력장을 이용하여 구하고, 이 식에 의한 이론상을 여러가지 경계조건하에서 컴퓨터 그래픽 하여 유도한 사상방정식의 타당성을 검토 하 였다.둘째, 본 논문에서 개발한 두 가지 종류의 직교이방성체를 사용하여 실험을 수행하고 실험에 의한 코스틱스상을 이론상과 비교, 검토 하였다.셋째, 이방성체의 코스틱스상으로부터 응력확대계수를 구하는 방법을 제시하고 이 방법을 실제 시편에 적용하여 신뢰 할수 있는 결과를 얻는 초기곡선의 범위를 결정 하였다. 그리고 이 범위에서 구한 응력확대 계수 값을 경계요소법을 이용한 변위외삽법에 의한 결과와 비 교함으로써 본 논문에서 제시하는 방법이 이방성체의 응력확대계수를 구하는 한 방법 으로 유효하게 사용될 수 있음을 밝혔다.

• Structural Engineering and Mechanics
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• 제65권6호
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• pp.699-706
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• 2018

In the present contribution, fracture resistance of U-notched GPPS members under mixed mode I/III loading conditions is assessed by using the Averaged Strain Energy Density (ASED) criterion. This criterion has been founded based on the ASED parameter averaged over a well-defined control volume embracing the notch edge. The validation of the theoretical criterion predictions is evaluated through comparing with the results of a series of mixed mode I/III fracture tests conducted on rectangular-shaped GPPS specimens weakened by a single edge U-notch. A recently developed apparatus for mixed mode I/III fracture experiments is employed for measuring the fracture loads of the specimens. The test samples are fabricated with different notch tip radii with the aim of evaluating the influence of this major feature of the U-notched components on the mixed mode I/III fracture behavior. It is shown that the onset of brittle fracture in U-notched GPPS specimens under various combinations of tension and out-of-plane shear can well be predicted by means of the ASED criterion.

• 한국안전학회지
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• 제14권4호
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• pp.28-36
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• 1999

In this paper, A circular arc crackered plate in biaxially stretched sheets was investigated in the boundary element method. The applications of fracture mechanics have traditionally concentrated on crack problems under an mode I, straight crack. However, many service failures occur from growth of cracks subjected to mixed mode loadings. A rectangular plate with arc crack or slanted central crack, under biaxial tensile loading, was treated analytically and also solved numerically. The Results from BEM applying different loading conditions, crack length (a/W), arc angle($\alpha$) are presented and discussed. The stress intensity factors are evaluated by the techniques of the J-integral. The decomposition method, used to decouple the stress intensity factors in mixed mode problems, is implemented by a considering a small circular contour path around each crack tip. The BIE method was successfully applied to a circular arc crackerd plate problem, also slanted centre cracked plate under mixed mode.