• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.7-12
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• 2004

A lifetime prediction of holddown spring screw in nuclear fuel assembly was performed using fracture mechanics approach. The spring screw was designed such that it was capable of sustaining the loads imposed by the initial tensile preload and operational loads. In order to investigate the cause of failure and to predict the stress corrosion cracking life of the screw, a stress analysis of the top nozzle spring assembly was done using finite element analysis. The elastic-plastic finite element analysis showed that the local stresses at the critical regions of head-shank fillet and thread root significantly exceeded than the yield strength of the screw material, resulting in local plastic deformation. Normalized stress intensity factors for PWSCC life prediction was proposed. Primary water stress corrosion cracking life of the Inconel 600 screw was predicted by using integration of the Scott model and resulted in 1.78 years, which was fairly close to the actual service life of the holddown spring screw.

• 한국정밀공학회지
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• 제27권8호
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• pp.28-34
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• 2010

Railway wheel and axle is the most critical components in railway system. A wheel and axle failure can cause a derailment with its attendant loss of life and property. The service conditions of railway vehicles have become severe in recent years due to a general increase in operating speeds. Therefore, more precise evaluate of wheelset strength and safety has been desired. Fracture mechanics characteristics such as dynamic fracture toughness, fatigue threshold and charpy impact energy with respect to the tread, plate, disc hole of wheel and the surface of press fitted axle are evaluated. This paper describes the difference of fracture toughness, fatigue crack growth and fatigue threshold at the locations of wheel and axle. The results show that the dynamic fracture toughness, $K_{ID}$, is obviously lower than static fracture toughness, $K_{IC}$ and the fracture mechanics characteristics are difference to the location of wheel tread and hole.

• 대한정형도수물리치료학회지
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• 제15권2호
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• pp.44-49
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• 2009

Purpose : The purpose of this study was to evaluate the incidence and mortality for hip fracture in the elderly in Jeju-do. Methods : We enrolled 254 cases among 318 patients older than 50 years of age with a hip fracture during two years period(2003-2004). We investigated the incidence and mortality during follow up 3~4 years period until December 31, 2007. Results : The crude incidences of hip fracture the age group ${\geq}50$ years were 141(11.2/10,000) in 2003, 177(13.6/10,000) in 2004, and 249(17.0/10,000), 69(6.3/10,000) for women and men, respectively. The mean age of them was 78.3 years, male was 69(21.7%), female was 249(78.3%) among 318 patients. Survivor was in the 146(57.5%), death was in the 108(42.5%) among 254 cases period for follow up. In the death group, activity was significantly lower at the time of post-fracture 3(p=0.013), 6(p=0.000), and 12 months(p=0.000). The mortality of hip fracture and crude death rate(CDR) were 108(42.5%, n=254), 11,884(1.7%, n=675,889) in 2003~2007 in Jeju. Conclusion : Developing and applying a variety of activity programs that increase activity in post-fracture may improve activities of daily living, reduce burden of family and society, be useful in improving the quality of life and ultimately lower the mortality.

• Computers and Concrete
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• 제5권3호
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• pp.261-277
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• 2008

This paper presents methodologies for remaining life prediction of plain concrete structural components considering tension softening effect. 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. A methodology to account for tension softening effects in the computation of SIF and remaining life prediction of concrete structural components has been presented. The tension softening effects has been represented by using any one of the models mentioned above. Numerical studies have been conducted on three point bending concrete structural component under constant amplitude loading. Remaining life has been predicted for different loading cases and for various tension softening models. The predicted values have been compared with the corresponding experimental observations. It is observed that the predicted life using bi-linear model and power curve model is in close agreement with the experimental values. Parametric studies on remaining life prediction have also been conducted by using modified bilinear model. A suitable value for constant of modified bilinear model is suggested based on parametric studies.

• 대한기계학회논문집A
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• 제31권12호
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• pp.1214-1220
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• 2007

The vertical roller mill, which performs the grinding and partly blending of raw material, is the one of the important machine to produce ordinary portland cement. It has been reported that an unexpected fatigue failure occurred in a table liner in the course of grinding portland cement. The life of table liner is estimated to $4{\times}10^7$ cycles in the design stage, but at the field, when its operating time reaches to $2{\times}10^6{\sim}8{\times}10^6$ cycles, the fracture of table liner begins to be found. The fracture of table liner is initiated from the outside edge of grinding path contacting with the grinding roller. Its maintenance normally take 30 % of the total maintenance costs of the roller mill. Therefore, this study shows the clarification of the reasons occurring the fatal destruction of the table liner by fatigue fracture analysis utilizing fracture mechanics and by the finite element method. And, the results from Goodman diagram illustrate relationship of including information on the transition between tensile and bending fatigue strength in the fatigue characterization of table liner.

• Journal of Welding and Joining
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• 제11권2호
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• pp.42-52
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• 1993

The corrosion fatigue fracture behaviour of dual phase steel was investigated in 3% NaCl solution at 302MPa and 137MPa. Fatigue test was conducted by cantilever type of self-made rotary bending fatigue testing machine. The fatigue strength increased with increasing the hardness of 2nd phase. Corrosion pit originated at the boundary of the 2nd phase. The size and number of corrosion pits were influenced by the 2nd phase hardness, and pits remained constant in size just after they were transited into cracks. The life of crack initiation was effected by stress level. The shape of relation of .DELTA. K and da/dN has smaller scattering in it in 3% NaCl solution than that in air. The higher the 2nd phase hardness is, the greater the corrosion fatigue life becomes. Corrosion fatigue fracture behaviour was primarily effected by mechanical factor in case of high stress(302MPa), but by electro-chemical reaction in a lower stress(137MPa). As stress level got lower and hardness of the 2nd phase got higher, the roughness of fracture surface increased.

• Journal of Acupuncture Research
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• 제35권3호
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• pp.145-148
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• 2018

The purpose of this case study was to use Korean medicine to treat posterior cruciate ligament avulsion fracture. The patient suffered left knee pain resulting from an avulsion fracture and was hospitalized for 59 days and treated with acupuncture and traditional Korean medicine. The effect of the treatment was evaluated using the Numerical Rate Scale, the Western Ontario and McMaster universities Osteoarthritis Index, and the European Quality of Life Five Dimensions. Following treatment of the pain in the left knee, scores for Numerical Rate Scale, Western Ontario and McMaster universities Osteoarthritis Index, and European Quality of Life Five Dimensions were improved. This study suggested that Korean Medicine could be an effective treatment for posterior cruciate ligament avulsion fractures. Further studies are needed to substantiate this conclusion.

• 대한기계학회논문집A
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• 제24권3호
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• pp.634-644
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• 2000

Fatigue crack growth and life is estimated by various fracture mechanical parameters but affected by load, material and environment. Fatigue character of component without surface notch cannot be e valuated by above-mentioned parameters due to microstructure of in-service material. Single fracture mechanical parameter or nondestructive parameter cannot predict fatigue damage in arbitrary boundary condition but multiple fracture mechanical parameters or nondestructive parameters can Fatigue crack growth modelling with three point representation scheme uses this merit but has limit on real-time monitoring. Therefore, this study shows fatigue damage model using backpropagatior. neural networks on the basis of X-ray half breadth ratio B/$B_o$ fractal dimension $D_f$ and fracture mechanical parameters can predict fatigue crack growth rate da/dN and cycle ratioN/$N_f$ at the same time within engineering estimated mean error(5%).

• 대한물리의학회지
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• 제4권2호
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• pp.125-131
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• 2009

Purpose：This study performed to evaluate the effect of hip fracture among persons over 50 years old, in Jeju-do, Korea, on mortality, activity of daily living(ADL). Methods：Three hundred eighteen patients over to 50 years of age who lived in Jeju-do and sustained a hip fracture from January 1st 2003 to December 31th 2004 were recruited. The information collected from the hospital records for each patient included age, sex, date of onset, and patients investigated activity grade, ADL, outdoor walking aid on 3month, 6month and 12month. Results：The incidence was 12.5/10,000 for total patients(female 17.0/10,000, male 6.3/10,000) in population over 50 years old. Patients who had lower activity grade and ADL level, showed higher mortality, and patients using outdoor walking aid showed higher mortality. Conclusion：The activity grade, ADL level, Using of outdoor walking aid affect mortality, so more programs about ADL must be developed for the life span and quality of life.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2292-2306
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• 2024

This study addresses cracks and fracture problems in engineering structures that may cause significant challenges and safety concerns, with a focus on pressure vessels in nuclear power plants. Comprehensive parametric three-dimensional mixed mode fracture analyses for inclined and deflected nozzle corner cracks with various crack shape aspect ratios and depth ratios in nuclear reactor pressure vessels are carried out. Stress intensity factor (SIF) solutions are obtained using FRAC3D, which is part of Fracture and Crack Propagation Analysis System (FCPAS), employing enriched finite elements along the crack front. Also, improved empirical equations are developed to allow the determination of mixed mode SIFs, K_I, K_II, and K_III, for any values of the parameters considered in the study. This study provides practical solutions to assess the remaining life and fail-safe conditions of nuclear reactors by providing accurate SIF determination.