• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.178-183
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• 1998

This paper examines the crack growth behavior of 7075-T651 and 5052-H32 aluminum alloys for variable load within tensile load range condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure are investgated by compliance method. The applied initial stress ratio is R=0.3 and variable load are R=0.65, 0.46. Crack length, stress intensity factor range, ratio of effective stress intensity factor range and crack growth rate etc. are inspected with fracture mechanics estimate.

• The Journal of the Korean dental association
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• v.38 no.7 s.374
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• pp.656-663
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• 2000

Recently dental emergency patients tend to increase and diversify because of increased living quality and acknowledgement of health care. We performed this study to understand the pattern of dental emergency and perform the adequate diagnosis and treatment. From August 1998 to July 1999, we inverstigated the rate of dental emergency, distribution according to disease pattern, monthly distribution, and types of emergency treatment from all the emergency patients that visited emergency medicine of Daejin Medical Center, Jesaeng Hospital. There were 266 dental patients(0.978%) from total 27,192 emergency patients. Types of emergency situations included lip lacerations, teeth fracture, teeth missing or avulsion, TMJ contusion, mandible fracture, tongue laceration, toothache, teeth luxation, and so forth. Dental emergency had highest frequency in July. The most common treatments included primary closure of soft tissue lacerations, fixations of luxated teeth and medications.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.232-236
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• 2004

The fracture characteristics of unidirectional composite single-lap bonded joints were investigated experimentally and numerically. The effects of bonding method, surface roughness, bondline thickness and the existence of fillet on the failure characteristics and strength of bonded single-lap joints were evaluated experimentally. The failure process, failure mode and the behavior of load-displacement curve was apparently different according to bonding method. The failure load of the specimen co-cured without adhesive was definitely superior to other types of specimens but the specimens co-cured with adhesive film had a less strength than secondary bonded specimens. In the secondary bonded specimens, the lower value of surface roughness and existence of fillet improved the strength of specimens. The strain energy release rates calculated by geometric nonlinear finite element analyses and Virtual Crack Closure Technique for the secondary bonded specimens considering the three types of initial cracks - comer crack, edge crack and delamination crack - were consistent with the test results.

• Journal of Chest Surgery
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• v.29 no.12
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• pp.1398-1400
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• 1996

The cardiac anatomic position immediately beneath the sternum leaves it vulnerable to injury when this bone is fractured. Cardiac rupture, however, is uncommon but survival following this injury is rare. We report the case of one patient who survived right ventricle perforation resulting from sternal fracture. The patient developed signs of pericardial tamponade and was brought to the operating theatre immediately for surgery through the emergency anterolateral thoracotomy Perforation of th right ventricle was repaired by direct closure without cardiopulmonary bypass. We believe that patients with cardiac rupture who reach the hospital alive can often be saved by prompt diagnosis and surgery.

• Journal of the Korean Ceramic Society
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• v.33 no.5
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• pp.602-615
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• 1996

The purpose of the present study is to investigate the microstructural effect on the R-curve behavior in three aluminas with different grain size distributions by analyzing the bridging stress distribution. The crack opening displacement (COD) according to the distance behind the stationary crack tip was measured using an in situ SEM fracture method. The measured COD values in the fine-grained alumina agreed well with Wiederhorn's sollution while they deviated from Wiederhorn's solution in the two coarse-grained aluminas because of the increase of the crack closure due to the grain interface bridging in the crack wake. A numerical fitting procedure was conducted by the introduction of the power-law relation and the current theoretical model together with the measured COD's in order to obtain the bridging stress distribution. The results indicated that the bridging stress function and the R-curve computed by the current model were consistent with those computed by the power-law relation providing a reliable evidence for the bridging stress analysis of the current model. The strain-softening exponent in the power-law relation n, was calculated to be in the range from 2 to 3 and was closely related to the grain size distribution. Thus it was concluded from the current theoretical model that the grain size distribution affected greatly the bridging stress distribution thereby resulting in the quantitative analysis of microfracture of polycrystalline aluminas through correlating the local-fracture-cont-rolling microstructure.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.4
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• pp.88-94
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• 2004

High manganese steel was maintained stability of Non-Magnetics performance. Fatigue tests were carried out under constant stress amplitude, using a non-magnetic high manganese steel. The fatigue crack growth mechanism of the high manganese steel was clarified from results such as observation of crack growth path and fracture surface. The result of getting this study was shown as following: 1) Remarkably ${\Delta}Kth$ of the high manganese steel is big with about 3 times of the general steel product. 2) In the low ${\Delta}K$ value region, da/dN is dependent on Kmax, and in the high ${\Delta}K$ value region, it is dependent on ${\Delta}Keff$. The reason of this behavior is crack closure due to fracture surface roughness and fretting oxide. 3) It seems to ease the stress concentration of crack tip crack growth behavior in the ${\Delta}Kth$ vicinity by the generation of the secondary crack.

• Journal of Ocean Engineering and Technology
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• v.2 no.2
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• pp.61-70
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• 1988

In order to consider the concept of the fitness for purpose'in fatigue design of offshore structure, fracture mechanics is applied to evaluate initial or weld defects. Generally, linear elastic fracture mechanics has been applied to tstimate initial fatigue crack propagation rate as well as long fatigue crack propagation rate. But, initial fatigue crack propagation rate in elasto-plastic notch field may not be characterized by application of stress intensity factor range .DELTA. K, because plastic effect due to stress concentration of notch may contribute to initial crack propagation. Therefore, to introduce the plastic effect into fatigue crack driving force, in this studty, the evaluating method of J-integral range .DELTA. J, was developed by willson was modified for application to notch field. In calculation of .DELTA. J obtained from the modified J-integral, stress gradient and crack closure behavior in the notch field were considered. The initial crack propagation rates in the notch fields of mild steels and high tensile strength steels were correlated to .DELTA. J. As the result, it was cleared that the present .DELTA. J is applicable to charachterize the fatigue crack propagation rates in both the elastic and elasto-plastic notch fields.

• Structural Engineering and Mechanics
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• v.19 no.3
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• pp.347-359
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• 2005

This paper attempts to develop the analytical model of estimating the fatigue damage using a linear elastic fracture mechanics method. The stress history on a welding member, when a truck passed over a bridge, was defined as a block loading and the crack closure theory was used. These theories explain the influence of a load on a structure. This study undertook an analysis of the stress range frequency considering both dead load stress and crack opening stress. A probability method applied to stress range frequency distribution and the probability distribution parameters of it was obtained by Maximum likelihood Method and Determinant. Monte Carlo Simulation which generates a probability variants (stress range) output failure block loadings. The probability distribution of failure block loadings was acquired by Maximum likelihood Method and Determinant. This can calculate the fatigue reliability preventing the fatigue failure of a welding member. The failure block loading divided by the average daily truck traffic is a predictive remaining life by a day. Fatigue reliability analysis was carried out for the welding member of the bottom flange of a cross beam and the vertical stiffener of a steel box bridge by the proposed model. Results showed that the primary factor effecting failure time was crack opening stress. It was important to decide the crack opening stress for using the proposed model. Also according to the 50% reliability and 90%, 99.9% failure times were indicated.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.802-810
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• 2003

In this paper, the modified singular fracture process zone (S-FPZ) model is proposed to consider variation of a fracture criterion for continuous crack propagation in concrete. The fracture properties of the proposed fracture model are strain energy release rate at a micro-crack tip and crack closure stress (CCS) versus crack opening displacement (COD) relationship in the FPZ. The proposed model can simulate the estimated fracture energy of experimental results. The analysis results of the experimental data shows that specimen geometry and loading condition did not affect the CCS-COD relation. But the strain energy release rate is a function of not only specimen geometry but also crack extension. Until 25 mm crack extension, the strain energy release rate is a constant minimum value, and then it increased linearly to the maximum value. The maximum fracture criterion occurred at the peak load for an large size specimen. The fracture criterion remains the maximum value after the peak load. The variation of the fracture criterion is caused by micro-cracking and micro-crack localizing. The fracture criterion of strain energy release rate can simply be the size effect of concrete fracture, and it can be used to quantify the micro-tracking and micro-crack localizing behaviors of concrete.

• Structural Engineering and Mechanics
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• v.74 no.6
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• pp.723-735
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• 2020

This study is reported the adhesion failure in adhesive bonded composite and specifically for the T-joint structure. Three-dimensional finite element analysis has been performed using a commercial tool and the necessary outcomes are obtained via an eight noded solid element (Solid 185-element) from the library of ANSYS. The structural analysis input has been incurred through ANSYS parametric design language (APDL) code. The normal and shear stress distributions along different layers of the joint structure have been evaluated as the final outcomes. Based on the stress distributions, failure location in the composite joint structure has been identified by using the Tsai-Wu stress failure criterion. It has been found that the failure index is maximum at the interface between flange and web part of the joint (top layer) which indicates the probable location of failure initiation. This kind of failures are considered as adhesion failure and the failure propagation is governed by strain energy release rate (SERR) of fracture mechanics. The different adhesion failure lengths are also considered at the failure location to calculate the SERR values i.e. mode I fracture (opening), mode II fracture (sliding) and mode III fracture (tearing) along the failure front. Also, virtual crack closure technique (VCCT) principle of fracture mechanics steps is used to calculate the above said SERRs. It is found that the mode I SERR is more dominating compared to other two modes of failure for the joint considered. Finally, the influences of various parametric (geometrical and material) effect on SERR of the joint structure are evaluated and discussed in details.