• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.283-288
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• 2005

Application of semiconductor sensors has widely spreaded into various industries because those have several merits like easy miniaturization and batch production comparison with previous mechanical sensors. But external conditions such as thermal and repetitive load have a bad effect on sensors's lifetime. Especially, this paper was focused on fatigue life of a interconnect made by various materials. Firstly we implemented the stress analysis for interconnect under thermal load and wording pressure. And the fatigue lifetime of each material was induced by Manson & Coffin Equation using the plastic stress-strain curve obtained by the plastic-elastic Finite Element Analysis.

• Journal of the Korean institute of surface engineering
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• v.39 no.1
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• pp.35-42
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• 2006

In this study, the fatigue properties on the cavitation damage of the flame quenched 8.8Al-bronze (8.8Al-4.5Ni-4.5Fe-Cu) as well as the current nuclear pump impeller materials (8.8Al-bronze, STS316 and SR50A) has been investigated using an ultrasonic vibratory cavitation test. For this the impact loads of cavitation bubbles generated by ultrasonic vibratory device quantitatively evaluated and simultaneously the cavitation erosion experiments have been carried out. The fatigue analysis on the cavitation damage of the materials has been made from the determined impact load distribution (e.g. impact load, bubble count) and erosion parameters (e.g. incubation period, MDPR). According to Miner's law, the determined exponents b of the F-N relation ($F^b$ N = Constant) at the incubation stage (N: the number of fracture cycle) were 5.62, 4.16, 6.25 and 8.1 for the 8.8Al-bronze, flame quenched one, STS316 and SR50A alloys. respectively. At the steady state period, the exponents b of the F-N' curve (N': the number of cycle required for $1{\mu}m$ increment of MDP) were determined as 6.32, 5, 7.14 and 7.76 for the 8.8Al-bronze, flame quenched one, STS316, and SR50A alloys, respectively.

• The Journal of Internal Korean Medicine
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• v.41 no.6
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• pp.1015-1029
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• 2020

Purpose: This study assessed the validity of a questionnaire (SEID-Q27) for diagnosis of chronic fatigue syndrome (CFS), designed based on the systematic exertion intolerance disorder (SEID) criteria. Methods: Two groups of participants were recruited: 1. a non-CFS control group: adult university personnel with a Chalder fatigue scale (CFQ) score ≥15, and 2. a CFS patient group: patients from an online CFS community diagnosed with CFS (diagnostic code of G93.3) with the symptoms present. The survey ran from September to October, 2020. The validity of the questionnaire was investigated by factor analysis and receiver operator characteristic (ROC) analysis. Results: Among the 35 adults surveyed, 30 (86%) participants had CFQ scores ≥15 (15 males and 15 females) and 5 (14%) had a CFS diagnosis (2 males and 3 females). The total mean score was significantly different between the two groups (CFS: 6.8±2.2 vs. control: 4.4±2.4, p<0.05). The area under the curve (AUC) was 0.827. With a cut-off point 62, the sensitivity was 60%, specificity 97%, and the discriminant ability of the survey was 79%. Conclusions: The SEID -Q27 appears to be a useful instrument for the diagnosis of CFS using SEID criteria. However, further large-scale studies are needed with greater numbers of participants.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.86-94
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• 2023

In this study, a supplementary detail capable of restraining out-of-plane deformation was proposed for steel slit dampers, and a constant amplitude cyclic loading test was performed with the application of the proposed detail and the shape ratio of the damper as variables. Repeated hysteresis and cumulative plastic deformation according to the test results were analyzed. Repeated hysteresis of the slit damper with the proposed detail showed a stable spindle-shaped hysteresis within the set variable range, and no out-of-plane deformation of the damper was observed until ultimate state. It was confirmed that the restraining panel effect through the application of the proposed details is effective in terms of both the strength and deformation capacity of the damper. In addition, experimental parameters for the fatigue curve evaluation of slit dampers were derived in this study. Based on the results, it is judged that quantitative comparison of structural performance with various types of seismic devices will be possible in the future.

• Structural Engineering and Mechanics
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• v.32 no.3
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• pp.459-475
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• 2009

This paper presents analytical methodologies for remaining life prediction of plain concrete structural components considering tension softening and size effects. Non-linear fracture mechanics principles (NLFM) have been used for crack growth analysis and remaining life prediction. Various tension softening models such as linear, bi-linear, tri-linear, exponential and power curve have been presented with appropriate expressions. Size effect has been accounted for by modifying the Paris law, leading to a size adjusted Paris law, which gives crack length increment per cycle as a power function of the amplitude of a size adjusted stress intensity factor (SIF). Details of tension softening effects and size effect in the computation of SIF and remaining life prediction have been presented. Numerical studies have been conducted on three point bending concrete beams under constant amplitude loading. The predicted remaining life values with the combination of tension softening & size effects are in close agreement with the corresponding experimental values available in the literature for all the tension softening models.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.4 s.142
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• pp.388-395
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• 2005

A numerical procedure is proposed as a mesh-size insensitive structural stress definition that gives a stress state at a weld toe with relatively large mesh size. The structural stress values obtained using different finite element types, i.e. shell element and solid element, are examined for typical weld structures. The calculation procedures are performed using the balanced nodal forces and moments obtained from finite element solutions. A consistent formulation based on work equivalent argument has been implemented to transform the balanced nodal forces and moments from shell to line force and line moments at each nodal position. The mesh-insensitivity, the effect of distance $\delta$(where the stress is calculated) and the potential limitations of the structural stress method are examined for various types of weldments. Based on the results from this study, it is expected to develop a more precise stress estimation technique for fatigue strength assessment of welded structures.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1587-1590
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• 2005

A rigid-plastic finite element analysis for the die forging process of a socket ball joint, which is used in the transportation system, was carried out. And also with the results, the elastic stress analysis for the forging die was performed in order to get basic data for the die life prediction. The die fatigue life prediction was simulated using Goodman's and Gerber's equation. The prediction technique for the fatigue life of a forged product, the socket ball joint, using DEFORM-3D is presented and the results are commented upon. Archard's wear model was used for the wear simulation and then the wear simulation and then the wear quantity was quantity was evaluated using volume. In order to prove the wear simulation results to be reliable, wear quantity of the real forging die set in used a forging factory was measured using a 3-dimensional measurement apparatus. The simulation results were relatively in good agreement with the experimental measurements.

• International Journal of Ocean System Engineering
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• v.3 no.4
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• pp.209-217
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• 2013

This paper presents a mooring design procedure for a floating offshore wind turbine. Offshore environmental data for Jeju are taken from KHOA (Korea Hydrographic and Oceanographic Administration) and used for the environmental conditions in numerical analyses. A semi-submersible-type floating wind system with a 5-MW-class wind turbine studied by the DeepCwind Consortium is applied. Catenary mooring with a studless chain is chosen as the mooring system. Design deliverables such as the nominal sizes of chain and length of the mooring line are decided by considering the long-term prediction of the breaking strength of the mooring lines where a 100-year return period is used. The designed mooring system is verified using a fatigue calculation based on rain-flow cycle counting, an S-N curve, and a Miner's damage summation of rule. The mooring tension process is obtained from time-domain motion analyses using ANSYS/AQWA.

• Journal of the Korean Ceramic Society
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• v.35 no.5
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• pp.429-436
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• 1998

The mechanical properties and damage mode of {{{{ {Y}_{2 } {O}_{3} }}-doped tetragonal (Y-TZP) can-didated as biomaterials were performed under indentation stress-strain curve critical load for yield and cracking strength degradation and fatigue behavior with Hertzian indentation tests. This material shows the brittle behavior which is confirmed by indentation stress-strain response. The critical load for cracking(Pc) is much higher than that for yields (Py) indicating crack resistance Strength were strongly dependant on contact area and there were no degradation when the indenter size was ${\gamma}$=3.18 mm suggesting that Y-TZP should be highly damage tolerant to the blunt contacts. Multi-cycle contact were found to be innocuous up to {{{{ {10 }^{6 } }} cycles at 500N and {{{{ {10 }^{5 } }} cycles at 1000N in water. On the other hand contacts at {{{{ {10 }^{6 } }} cycles at 1000 N in water did show some signs of incipient degradation. By contrast contacts with Vickers indenter pro-duced substantial strength losses at much lower loads suggesting that the mechanical integrity of this ma-terial would be compromised by inadvertent sharp contacts.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.930-937
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• 2005

One of the useful technology for light-weightening of components required in the automobile and machine industry is to use of high strength materials. To improve material properties, carbonizing treatment, nitrifying treatment, and shot-peening method are representatively applied, However, the shot-peening method is generally used to remove the surface defect of steel and to improve the fatigue strength on surface. Benefits by shot peening are to make increase resistance against fatigue, stress corrosion cracking, fretting, galling, erosion and closing of pores. In this paper, investigated the effect of shot peening on the corrosion of SUP-9 steel immersed in $3.5\%$ NaCl solution and corrosion characteristics by the heat treatment during shot peening process. The immersion test was performed on the four kinds of specimens. Corrosion potential, polarization curve, residual stress and etc. were investigated from the experimental results.