• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.532-538
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• 2012

Failure mechanisms for a highly filled elastomer were discussed, and the stip-yield and the inherent flaw models were applied to them. Then, failure assessment diagram methods were investigated by means of modified two models. Fracture toughness tests using CCT(center-cracked tension) specimens made of a highly filled elastomer were conducted to generate the failure assessment diagrams. The failure assessment diagram of the inherent flaw model was normalized in order to compare with that of the modified strip-yield model. From the comparison of two failure assessment diagrams, it was found that the failure assessment diagram of the modified inherent flaw model more conservatively assesses the failure than that of the modified strip-yield model.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.5
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• pp.67-73
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• 2012

Failure mechanisms for a solid propellant were discussed, and the stip-yield and the inherent flaw models were applied to them. Then, failure assessment diagram methods were investigated by means of modified two models. Fracture toughness tests using CCT(center-cracked tension) specimens made of a solid propellant were conducted to generate the failure assessment diagrams. The failure assessment diagram of the inherent flaw model was normalized in order to compare with that of the modified strip-yield model. From the comparison of two failure assessment diagrams, it was found that the failure assessment diagram of the modified inherent flaw model more conservatively assesses the failure than that of the modified strip-yield model.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.247-247
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• 2002

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.3
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• pp.289-295
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• 2004

Pressure tubes are major component of nuclear reactor, but only selected samples are periodically examined due to numerous numbers of tubes. Current in-service inspection result show there is high probability of flaw existence at uninspected pressure tube. Probabilistic analysis is applied in this study for the integrity assessment of uninspected pressure tube. All the current integrity evaluations procedures are based on conventional deterministic approaches. So it is expected that the results obtained are too conservative to perform a rational evaluation of lifetime. More realistic failure criteria, based on FAD are also proposed for the probabilistic analysis. As a result of this study failure probabilities for various conditions are calculated, and examined application of FAD and LBB concept.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1211-1215
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• 2003

Pressure tubes are major component of nuclear reactor, but only selected samples are periodically examined due to numerous numbers of tubes. Current in-service inspection result show there is high probability of flaw existence at un-inspected pressure tube. Probabilistic analysis is applied in this study for the integrity assessment of un-inspected pressure tube. But all the current integrity evaluations procedures are based on conventional deterministic approaches. So many integrity evaluation parameters are not directly apply to probabilistic analysis. As a result of this study failure assessment diagram are proposed based on test data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2022-2032
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• 1999

In recent years, the subject of remaining life assessment has drawn considerable attention in the power generation industry. In power generation systems a variety of structural components, such as steam pipes, turbine rotors, and superheater headers, typically operate at high temperatures and high pressures. Thus a life prediction methodology accounting for fracture and rupture is increasingly needed for these components. For accurate failure assessment, in addition to the single parameter such as K or J-integral used in traditional fracture mechanics, the second parameter like T-stress describing the constraint is needed. The most critical defects in such structures are generally found in the form of semi-elliptical surface cracks in the welded piping-joints. In this work, selecting the structures of surface-cracked plate and straight pipe, we first perform line-spring finite element modeling, and accompanying elastic-plastic finite element analyses. We then present a framework for including constraint effects (T-stress effects) in the R6 failure assessment diagram approach for fracture assessment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1187-1194
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• 2009

During the last decade, possibility of flaw occurrences has been rapidly increased world-widely as the increase of operating times of petro-chemical facilities. For instance, from a recent in-service inspection, three different sized surface cracks were detected in welding parts of a spherical oxygen holder in Korea. While API579 code provides corresponding engineering assessment procedures to determine crack driving forces, in the present work, numerical analyses are carried out for the cracked oxygen holder to investigate effects of complex geometry, analysis model and residual stress. With regard to the detailed finite element analysis, stress intensity factors are determined from both the full three-dimensional model and equivalent plate model. Also, as an alternative, stress intensity factors are calculated for equivalent plate model by employing the noted influence stress function technique. Finally, parametric structural integrity evaluation of the cracked oxygen holder is conducted in use of failure assessment diagram method, J/T method and DPFAD method. Effects of the geometry and so forth are examined and key findings from the simulations are fully discussed, which enables to determine practical safety margins of spherical components containing a defect.

• Composites Research
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• v.22 no.5
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• pp.30-36
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• 2009

The failure strengths and modes in carbon fiber reinforced polymeric composites, with two serial bolt-fastened composite joints, were investigated to evaluate the typical joint configurations of composite components. The parametric studies were performed experimentally at room temperature dry and elevated temperature wet, $82.2^{\circ}C$ on several different laminate configurations. Based on the experimental data presented, two basic load-displacements curves are observed. Each failure mode has the characteristic curve. It is showed that the bearing failure mode occurs in elevated temperature wet condition. It is analysed that the strength of bearing failure mode is not highly depending on the effective modulus of specimen. The failure strength at elevated temperature wet is decreased by the cause of interfacial deterioration between fiber and matrix with moisture absorption.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.54-59
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• 2004

In this paper probabilistic fracture mechanics(PFM) approach is employed to evaluate the integrity of CANDU Zr-2.5Nb pressure tubes. Modified failure assessment diagram(Jr-FAD), plastic collapse, and critical crack length(CCL) approach are used for evaluating failure probability of the tubes. Jr-FAD was extended from the Kr-FAD because fracture of pressure tubes occurs in brittle manner due to hydrogen embrittlement of material by deuterium fluence. For developing the probabilistic integrity evaluation module, AECL procedures and fracture toughness parameters of EPRI were used.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.945-951
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• 2013

This study evaluated the fatigue strength of the bogie frame of an urban maglev train through fatigue analysis, cumulative damage, and fatigue tests based on a proposed fatigue evaluation method. The results of FEM analysis in which various load combinations were adopted showed that all data were under the fatigue limit of a butt welded joint made of A6005 in a Goodman diagram. The cumulative fatigue damage was calculated at the highest level from a bolt connecting the area of the electromagnetic pole in the casting block; however, the total sum was evaluated as D=0.808 based on $1{\times}10^7$ cycles, which indicates that it did not exceed the failure criteria. In addition, the results of the fatigue testshowed that there was no crack at any position in the bogie frame, which corresponded to the results of fatigue analyses.