• Journal of Ship and Ocean Technology
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• v.1 no.1
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• pp.57-72
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• 1997

The larger trends related to cracking in ocean going vessels (primarily tankers and bulk carriers) are reviewed on the basis of available data. The typical interrelated causes of such cracking are: high local stresses, extensive use of higher strength steels, inadequate treatment of dynamic loads, adverse operational factors (harsh weather, improper vessel handling), and controllable structural degradation (corrosion, wear, stevedore damage). Three consequences of cracking are then discussed: structural failure, pollution, and increased maintenance. The first two, while rare, are potentially of high consequence including loss of life. The types of solutions that can be employed to improve the durability of ships in the face of fatigue cracking are then presented. For existing vessels, these solutions range from repairs based on structural analysis or service experience, control of corrosion, and enhanced surveys. For new vessels, the use of advanced design procedures that specifically address dynamic loads and fatigue cracking is necessary. As the preferred solution to the problem of cracking in ships, this paper advocates prevention by explicit design by first principles.

• Steel and Composite Structures
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• v.52 no.4
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• pp.391-403
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• 2024

The flexural behavior of composite sandwich wall panels with different thicknesses, numbers of holes, and hole forms, and arrangement form of longitudinal steel bar (uniform type and concealed-beam type) are investigated. A total of twelve composite sandwich wall panels are prepared, utilizing modified polystyrene particles mixed with foam concrete for the flexural performance test. The failure pattern of the composite sandwich wall panels is influenced by the extruded polystyrene panel (XPS) panel thickness and the reinforcement ratio in combination, resulting in both flexural and shear failure modes. Increasing the XPS panel thickness causes the specimens to transition from flexural failure to shear failure. An increase in the reinforcement ratio leads to the transition from flexural failure to shear failure. The hole form on the XPS panel and the steel bar arrangement form affect the loading behavior of the specimens. Plum-arrangement hole form specimens exhibit lower steel bar strain and deflection compared to linear-arrangement hole form specimens. Additionally, specimens with concealed beam-type steel bar display lower steel bar strain and deflection than uniform-type steel bar specimens. However, the hole form and steel bar arrangement form have a limited impact on the ultimate load. Theoretical formulas for cracking load are provided for both fully composite and non-composite states. When compared to the experimental values, it is observed that the cracking load of the specimens with XPS panels closely matches the calculations for the non-composite state. An accurate prediction model for the ultimate load of fully composite wall panels is developed. These findings offer valuable insights into the behavior of composite sandwich wall panels and provide a basis for predicting their performance under various design factors and conditions.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.244-249
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• 2008

It happened a failure on special bolt which supported main landing gear actuator up-lock rod of 00 aircraft. Fracture was occurred at end of center drilled hole and thread machined on bolt. Metallographic, fractographic, and other characteristics of embrittlement analysis and experiments carried out on the failed bolt to find out the reason. Bolt surface was cadmium electroplated(EP) to give lubrication and provide excellent corrosion resistance. Resultly, Bolt was failed due to cadmium embrittlement occurred during baking treatment as well as center drilled hole. for the failure that are relevant to failure analysis and prevention. For their successful functional application, cadmium EP bolts require proper and adequate baking treatment after electroplating, and is complete with no center drilled hole

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.15 no.2
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• pp.40-49
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• 2019

In this paper, failure probabilities of the OPR1000 reactor vessel under pressurized thermal shock (PTS) were estimated using the probabilistic fracture mechanics code, R-PIE. Input variables of initial crack distribution, crack size, copper contents, and upper shelf toughness were selected for the sensitivity analyses. A wide range of the input data were considered. Through-wall cracking frequencies determined by the product of the vessel failure probability and the corresponding occurrence frequency of the transient were also compared to the acceptance criterion. The results showed that transient history had the most significant impact on the vessel failure probability. Moreover, conservative assumptions resulted in extremely high through-wall cracking frequencies.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.769-774
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• 2010

It happened fractures on special bolt which supported main landing gear actuator up-lock rod of aircraft. Cracks were initiated mainly from the center hole and the external thread of the special bolt. To find out failure root causes, metallographic, fractographic analyses as well as test work were carried out. From the fractographic study by SEM work, fracture occurred by a brittle intergranular type failure. The fracture could be occurred primarily by solid-metal-induced embrittlement due to cadmium embrittler penetrated into the flaw existed after machining work for center hole and thread on the bolt during baking treatment processing to eliminate hydrogen. For its successful application, cadmium EP bolts require proper and adequate baking treatment after electroplating, and make no more drilled center hole on the bolt to prevent same failure.

• Magazine of the Korea Concrete Institute
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• v.9 no.2
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• pp.133-144
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• 1997

Concrete plasticity models fol the analysis of reinforced concrete members in plane stress are studied. The proposed plasticity model for reinforced concrete provides a unified approach combining plasticity theory and damage models. It addresses strength mhancement under rnultiaxial compression. and tensile cracking damage. The model uses multiple failure criteria for compressive crushing and tensile cracking. For tensile cracking behavior. rotating-crack and fixed-crack plasticity models are compared. As crushing failure criterion, the Drucker-Prager and the von Mises models are used for comparison. The model uses now and existing damnge models fbr tension softening, tension stiffening. and compression softening dup to tensilt. cracking. Finite element analyses using the unified method are compatxd with existing rxpcrimcntal r.esults. To vei.ify the proposcd crushing and cracking plasticity models, the experiments have load capacities govc11.nc.d either by compressive crushing of'concrete or by yi~lding of' reinforcing steel.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.579-582
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• 2005

Tunnel lining is the final support of a tunnel and reflects the results of the interaction between ground and support system. Recently it is very difficult to support and manage the tunnel because the cracks on tunnel lining cause problems in supporting and managing tunnels. Therefore the analysis of the cracks is quite strongly required. The major role played by the steel fiber occurs in the post-cracking zone, in which the fibers bridge across the cracked matrix. Because of its improved ability to bridging cracks, steel fiber reinforcement concrete(SFRC) has better crack properties than that of reinforced concrete. In this study, mechanical behaviour of a tunnel lining was examined by model tests. The model tests were carried out under various conditions taking different loading shapes, thicknesses and leakage of lining, and volume content of steel fiber. From these model test, the cracking load, the failure load, defection and cracking position and type were examined and the characteristics of deformation and failure for tunnel lining were estimated and researched.

• Computers and Concrete
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• v.4 no.1
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• pp.67-82
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• 2007

The discrete crack-concept is applied to study the 3D propagation of tensile-dominated failure in plain concrete. To this end the Partition of Unity Finite Element Method (PUFEM) is utilized and the strong discontinuity approach is followed. A consistent linearized implementation of the PUFEM is combined with a predictor-corrector algorithm to track the crack path, which leads to a robust numerical description of concrete cracking. The proposed concept is applied to study concrete failure during the PCT3D test and the predicted numerical results are compared to experimental data. The proposed numerical concept provides a clear interface for constitutive models and allows an investigation of their impact on concrete cracking under 3D conditions, which is of significant scientific interests to interpret results from 3D experiments.

• Journal of Mechanical Science and Technology
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• v.14 no.2
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• pp.152-158
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• 2000

The contents of this paper include the evaluation of corrosion characteristics and the behaviour of stress corrosion cracking (SCC) for the weldment and post weld heat treatment (PWHT) specimen and parent of HT -60 steel using a slow strain rate test (SSRT) in synthetic seawater. Corrosion characteristics were obtained from the polarization curves by potentiostat, and SCC phenomena were evaluated through the parameters such as reduction of area and time to failure by comparing the experimental results in corrosive environment with those obtained in air. Corrosion rate of the weldment was the fastest, followed by parent and PWHT specimen. SCC phenomena between the weldment of HT-60 steel and synthetic seawater were shown. Besides, SCC was dependent upon the pulling speed greatly. Maximum severity of SCC was obtained at a speed of $10^{-6}mm/min$, whereas SCC could not be seen almost at $10^{-4}mm/min$. The resistance to SCC for PWHT specimen was improved considerably compared that of the weldment at $10^{-6}mm/min$. In case of SCC failure, it was verified from SEM examination that brittle mode and lots of pits could be seen at the fractured region near the surface of the specimen.

• Nuclear Engineering and Technology
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• v.10 no.2
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• pp.65-72
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• 1978

In this paper, it is attempted to investigate the phenomena of iodine stress corrosion cracking of Zircaloy-4 cladding failures in reactor through the results of similar out-of-pile test in iodine vapour. The main result of this experiment is a finding of the relation between the threshold stress which can lead to iodine stress corrosion cracking of Zircaloy-4 tube and the iodine concentration. The values of critical stress and the critical iodine concentration are also obtained. A model which relates failure time of Zircaley-4 tube to failure stress and iodine concentration is suggested as follows: log t$_{F}$ =5.5-(3/2)log$_{c}$-4log $\sigma$ where t$_{F}$ : failure time, minutes c: iodne concentration, mg/㎤ $\sigma$: stress, 10$^4$psi.