• 대한기계학회논문집A
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• 제30권11호
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• pp.1455-1460
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• 2006

The relationship between fatigue crack growth behavior and cyclic crack tip opening displacement is studied. An elastic-plastic finite element analysis (FEA) is performed to examine the growth behavior of fatigue crack, where the contact elements are used in the mesh of the crack tip area. We investigate the relationship between the reversed plastic zone size and the changes of the cyclic crack tip opening displacement along the crack growth. We investigate the effect of the element size when predict fatigue crack opening behavior using the cyclic crack tip opening displacement obtained from FEA. The cyclic crack tip opening displacement is related to fatigue crack opening behavior.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.67-72
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• 2001

The LBB behavior and the crack opening displacement after a crack penetrated wall thickness of statically indeterminate piping system were investigated in this study, compared with statically determinate piping system. The reduction of ultimate strength caused by a crack was relatively small in the statically indeterminate piping system. The statically indeterminate piping system has more safety margin for LBB behavior than the statically determinate piping system. The crack opening displacement could be evaluated by using the plastic rotation angle proposed to evaluate the crack opening displacement after crack penetration in pipe with a non-penetrating crack.

• 대한기계학회논문집
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• 제14권6호
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• pp.1576-1582
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• 1990

본 연구에서는 Al 2024-T3 판으로 제작된 한면 노치 시편에 여러 조건의 피로 하중을 가하여 노치면내에 형성된 미소 피로균열의 COD를 광학적 간섭현상에 기초를 둔 미소 변위측정기(Interferometric Strain/Displacement Gage`ISDG)를 개량하여 측 정하였다. 이 ISDG의 컴퓨터 조정방식을 정밀화시켜 0.02$\mu\textrm{m}$까지의 상대변위를 측정 할 수 있도록 보완하였다. 고정밀화돈 측정기로 수십 $\mu\textrm{m}$길이의 미소균열의 COD도 측 정하였고 컴류터에 저장시킴으로써 시험후 미소 피로균열에 대한 열림 특성을 분석할 수 있다. 측정된 미소 피로균열의 균열열림특성을 고찰하고 긴 균열의 열림특성과도 비교.분석 하였다.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.337-343
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• 2006

Numerical calculations are made in order to find a possible correlation between the J-integral and the crack mouth opening displacement(CMOD) in dynamic nonlinear fracture experiments of 3-point bend(3PB) specimens. Both elastic-plastic and elastic-viscoplastic materials are considered at different impact velocities. The J-integral may be estimated from the crack mouth opening displacement which can be measured directly from photographs taken during dynamic experiments.

• International Journal of Precision Engineering and Manufacturing
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• 제1권2호
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• pp.84-93
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• 2000

Computer simulations of the mechanical behavior of 3 point bend specimens with a quarter notch under impact load are performed. This validity is found to be identified by the experimental proof. The cases with various loading rates applied at the side of the specimen are considered. An elastoplastic von Mises material model is chosen. Gap opening displacement, reaction force, crack tip opening displacement and strain rate are also compared with rate dependent material(visco-plastic material). The stability during various dynamic load can be seen by using the simulation of this study. These differences of the cases with various loading rates are also investigated.

• 대한금속재료학회지
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• 제46권6호
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• pp.345-350
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• 2008

The magnitude of constraint effect $A_2$ value was experimentally estimated by using crack tip opening displacement(CTOD) between elastic and plastic regions near crack tip front for CT specimen with $25.4t{\ss}{\AE}$ SS400 steel. The constraint effect, $A_2$ was dependent on specimen configuration and on the measured positions of CTOD near crack front. $A_2$ should be estimated using the opening displacement calculated within crack front plastic region. If not, it's not reliable to evaluate of constraint effect at crack growth initiation in this paper.

• Journal of Mechanical Science and Technology
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• 제16권1호
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• pp.24-31
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• 2002

The leak-before-break (LBB) behaviors of a structural component under high and low fatigue loads are an important problem in nuclear power plants, liquid nitrogen gas tankers and chemical plants. This paper is an experimental study to evaluate the crack opening behavior after penetration for plate and pipe specimens. Crack opening displacement after penetration under low fatigue load could be satisfactorily determined at the center of the plate thickness regardless of the specimen size. In the case of high fatigue load, it is shown that the crack opening displacement at the center of a penetrated crack carl be derived using the gross stress, $\sigma$/sug G/, and the front surface crack length, a$\_$s/, together with the back surface crack length, a$\_$b/.

• Journal of Oral Medicine and Pain
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• 제23권1호
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• pp.21-36
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• 1998

The purpose of this study was analyse the mandibular movements in patients with internal derangement of the temporomandibular joint according to diagnostic subgroups. The author classified patients with internal derangement of the temporomandibular joint into 4 diagnostic subgroups by means of the magnet resonance imagings, and evaluated the clinical signs and the mandibular movements with Mandibular Kinesiograph(MKG) in each subgroups. The mandibular movements, measured in this study, were the types of movement in frontal and sagittal plane, velocities in opening and closing movement, and the opening and closing movement, and the opening and closing velocity pattern. The data were compared between the 5 groups including the normal group. The results were as follows : 1. Pain was more frequently observed in the anterior disc displacement without reduction group than in the anterior disc displacement with reduction group. Sound of joint was more frequently observed in the anterior disc displacement with reduction group, and limitation of mandibular opening movement was more frequently observed in the anterior disc displacement without reduction group. Duration of the anterior disc displacement without reduction group was significantly short compared to that of the anterior disc displacement with reduction group, and duration of the unilateral anterior disc displacement without reduction group was shortest in the experimental group. The frequency of Angle's classifications had not significant correlations between the experimental groups. 2. Active and passive range of the opening movement, maximum protrusive movement, maximum lateral movement toward left side were significantly decreased in the experimental groups compared to the control group, but there was no significant difference in the range of the maximum lateral movement toward right side between the control and experiment groups. In unilateral anterior disc displacement without reduction group, the range of maximum lateral movement toward unaffected side was no significant difference in the range of the maximum lateral movement between toward affected side and toward unaffected side. 3. Maximum opening velocity, maximum closing velocity, average opening velocity, average closing velocity and maximum velocity of terminal tooth contact were significantly decreased in the experimental groups compared to control group. There was no significant difference in maximum opening velocity and maximum velocity of Terminal tooth contact between the subgroups of the experimental group each other, but there was significant difference in maximum closing velocity, average opening velocity and average closing velocity between the subgroups each other. 4. In the frontal plane of the MKG, the frequency of complex deviation type(F-2)pattern was significantly increased in the anterior disc displacement with out reduction group compared to the anterior disc displacement with reduction group and the control group. In the sagittal plane, the frequency of coincident type(S-1)was decreased in the same group. 5. In the maximum opening velocity pattern, the frequency of no-peak type (OV-3)in the unilateral anterior disc displacement with reduction group was significantly increased compared to the control group. The frequency of 1-peak type (OV-1) and 2-peak type (OV-2) was decreased in the anterior disc displacement with out reduction group, but the frequency of no-peak type (OV-3)was increased in the same group. In the maximum closing velocity pattern, the frequency of no-peak type (CV-3) was significantly increased in the anterior disc displacement without reduction group. Compared to the anterior disc displacement with reduction group and the control group. The frequency of 1-peak type (CV-1) and 2-peak type (CV-2) in the anterior disc displacement with reduction group was decreased than that in the control group.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.729-732
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• 2003

The K-R design curve is an engineering method of linear-elastic fracture analysis under plane-stress loading conditions. By the way, linear-elastic fracture mechanics (LEFM) is valid only as long as nonlinear material deformation is confined to a small region surrounding the crack tip. Like general steels, it is virtually impossible to characterize the fracture behavior with LEFM, in many materials. Critical values of J contour integral or crack tip opening displacement (CTOD) give nearly size independent measures of fracture toughness, even for relatively large amounts of crack tip plasticity. Furthermore, the crack tip opening displacement is the only parameter that can be directly measured in the fracture test. On the other. the crack tip opening angle (CTOA) test is similar to CTOD experimentally. Moreover, the test is easier to measure the fracture toughness than other method. The shape of the CTOA curve depends on material fracture behavior and, on the opening configuration of the cracked structure. CTOA parameter describes crack tip conditions in elastic-plastic materials, and it can be used as a fracture criterion effectively. In this paper, CTOA test is performed for steel JS-SS400 hot-rolled thin plates under plane-stress loading conditions. Special experimental apparatuses are used to prevent specimens from buckling and to measure crack tip opening angle for thin compact tension (CT) specimens.

• Nuclear Engineering and Technology
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• 제39권1호
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• pp.75-84
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• 2007

This paper presents a closed-form model for evaluating the restraint effect of pressure induced bending on the opening of a circumferential through-wall crack, which is considered plastic deformation behavior. Three-dimensional finite element analyses with different crack lengths, restraint conditions, pipe geometries, magnitudes of internal pressure, and tensile properties were used to investigate the influence of each parameter on the pressure-induced bending restraint on the crack opening displacement. From these investigations, an analytical model based on elastic-perfectly plastic material was developed in terms of the crack length, symmetric restraint length, mean radius to thickness ratio, axial stress corresponding to the internal pressure, and normalized crack opening displacement evaluated from a linear-elastic crack opening condition. Finite element analyses results demonstrate that the proposed analytical model reliably estimated the restraint effect of pressure-induced bending on the plastic crack opening of a circumferential through-wall crack and properly reflected the dependence on each parameter within the range over which the analytical expression was derived.