• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.385-386
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• 2006

A brake disk in railway vehicle is safety part. Requirements not only in performance but also in comfort, serviceability and working lifetime are high and rising. In this study, we carried out fatigue test and thermal stress analysis. To determine a pressure distribution, contact pressure analysis precede thermal stress analysis. Especially, characteristics of the brake disk were analyzed in considering intial velocity, and thickness of a frictional plate. Form the comparing the results of experiment and FEM analysis, fatigue characteristic and fatigue life assessment ok a brake disk of railway vehicle were performed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.1
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• pp.98-107
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• 1998

There are many weld defects such as surface crack, lack of fusion, and imcomplete penetration in the butt joint of the existing steel bridges. The crack-like defects may significantly reduce the fatigue life of the structure. This paper presents the procedure and the results of the fatigue assessment of the butt joints with weld defect in the existing steel girder bridge. The butt joints with imcomple penetration were instrumented with strain gages to determine the stress histogram under normal traffic. Based on the measured stress histogram the crack propagation analyses were performed for the fatigue assesment. By using the suggested procedure and methodology, one can decide the time of periodic inspection and the necessity of repair of the butt joints with serious weld defects in the existing steel bridge.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.1
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• pp.1-7
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• 2020

In general, an inspection schedule is established based on the long-term fatigue life during the design stage. However, in the design stage, it is difficult to clearly identify the uncertainty factors affecting long-term fatigue life. In this study, the probabilistic fatigue life assessment was conducted in accordance with the methodology of DNV-GL. Firstly, The initial crack distribution estimated through the initial crack propagation analysis was updated by reflecting the results of crack inspection. Secondly, the updated crack distribution was compared with the initial crack distribution, and the probability of failure was updated with the effect of crack inspection.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.73-75
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• 2005

The objective of this study is to estimate the feasibility of X-ray diffraction method application for fatigue life assessment of the high-temperature pipeline steel such as main steam pipe, reheater pipe and header etc. in power plant. In this study, X-ray diffraction tests using various types of specimen simulated low cycle fatigue damage were performed in order to analyze fatigue properties when fatigue damage conditions become various stages such as 1/4, 1/2 and 3/4 of fatigue life, respectively. As a result of X-ray diffraction tests for specimens simulated fatigue damages, we conformed that the variation of the full width at half maximum intensity decreased in proportion to the increase of fatigue life ratio.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.103-110
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• 2010

In this study, an assessment method on creep-fatigue crack initiation and crack growth for a Mod.9Cr-1Mo steel (ASME Grade 91) structure has been developed with an extension of the French RCC-MR A16 procedure. The current A16 guide provides defect assessment procedure for a creep-fatigue crack initiation and crack growth for an austenitic stainless steel, but no guideline is available yet for a Mod.9Cr-1Mo steel which is now widely being adopted for structural materials of future nuclear reactor system as well as ultra super critical (USC) thermal plant. In the present study an assessment method on creep-fatigue crack initiation and crack growth is provided for the FMS (Ferritic-Martensitic Steel) and assessment on the creep-fatigue crack behavior for a structure has been carried out. The assessment results were compared with the observed images from a structural test.

• Special Issue of the Society of Naval Architects of Korea
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• 2015.09a
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• pp.63-68
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• 2015

This paper presents fatigue analysis of helideck structures located in FPSO. After FPSO is moved to the target position where production of resource is performed, FPSO stays at the target position and performs production of resource, storage and off-loading during the design life. Helideck structure is located in FPSO essentially for the movement of personnel and life rescue at emergency situations by using helicopters. Because inertial load induced by FPSO motion and landing and taking-off load of helicopter occur at helideck structures cyclically, helideck structures should be designed to withstand fatigue loads. Therefore, The fatigue assessment of helideck structures should be performed with fatigue loads. Effect of stress concentration due to misalignment between welded plates is considered in fatigue assessment additionally.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2977-2981
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• 2021

Corrosion fatigue crack growth (FCG) behavior of 316LN stainless steel was investigated in high-temperature pressurized water at different temperatures, load ratios (R = K_max/K_min) and rise times (t_R). The environmental assisted effect on FCG rate was observed when both the R and t_R exceeded their critical values. The FCG rate showed a linear relation with stress intensity factor range (ΔK) in double logarithmic coordinate. The environmental assisted effect on FCG rate depended on the ΔK and quantitative relations were proposed. Possible mechanisms of environmental assisted FCG rate under different testing conditions are also discussed.

• Journal of Welding and Joining
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• v.30 no.6
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• pp.86-91
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• 2012

Fatigue tests and analyses were carried out to investigate fatigue strength and crack initiation point of load-carrying asymmetric double bevel cruciform welded joints. Mesh-insensitive structural stress approach was adopted to estimate high precise fatigue life and crack initiation point. Two different case material and weld shape were considered in this study. Results of fatigue tests and analyses were compared and discussed in consideration of applicability of structural stress approach as the reliable fatigue assessment method of cruciform welded joints.

• Journal of muscle and joint health
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• v.5 no.2
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• pp.206-221
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• 1998

The purpose of this study was to validate translated Multidimensional Assessment of Fatigue(MAF) scale. The scale is a 16-item scale that measures four dimensions of fatigue : severity, distress, impact, timing. Fourteen items are numerical rating scales and 2 items have multiple choice responses. Data were collected from the 137 patients with rheumatoid arthritis after content validation. Criterion validity was tested by correlation coefficient with Piper Fatigue Scale, which resulted in 0.7573(p<.0000). Construct validity was tested by item analysis and factor analysis. Corrected item-total correlation coefficients were 0.63-0.88. And factor analysis showed 2 factors : fatigue degree factor and fatigue impact factor. These two factors explained 73.5% of total variance. Reliability of internal consistency was 0.96 in Cronbach's alpha. Further validation study is necessary in each factor in other settings with other subjects.

• Journal of Ocean Engineering and Technology
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• v.20 no.5 s.72
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• pp.82-88
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• 2006

This assessment is concerned with the fatigue strength of the tendon porch found in TLP. Lorge-scale fatigue tests with models constructed at 30% the size of the real structures have been carried out to investigate the fatigue behavior of the API 2W Grade 50 steel recently produced by POSCO. The fatigue life for the present test models was obtained based on the concept of nominal stress. A comparison of the present test results with those obtained by a numerical approach based on the structural analysis results has showngood agreement. The present results were also compared with the design curves in DnV RP-C203.