• 한국해양공학회지
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• 제21권2호
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• pp.50-59
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• 2007

Steam generator tubes are degraded from wear, stress corrosion cracking, rupture and fatigue and so on. Therefore, the failure assessment of steam generator tube is very important for the integrity of energy plants. In the steam generator tubes, sometimes, the local wall thinning may result from severe degradations such as erosion-corrosion damage and wear due to vibration. In this paper, the elasto-plastic analysis was performed by FE code ANSYS on steam generator tubes with wall thinning. Also, the four-point bending tests were performed on the wall thinned specimens, and then it was compared with the analysis results. We evaluated the failure mode, fracture strength and fracture behavior from the experiment and FE analysis. Also, it was possible to predict the crack initiation point by estimating true fracture ductility under multi-axial stress conditions at the center of the thinned area from FE analysis.

• 대한물리의학회지
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• 제18권4호
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• pp.121-131
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• 2023

PURPOSE: The purpose of this study was to evaluate the effects of ice and hot packs on proprioception, balance, and muscle strength in knee extensor muscle fatigue. METHODS: A total of 31 male and female students in their twenties from a university in A, Chungnam, Korea, were selected as participants. Three experiments were conducted to assess static balance, dynamic balance, proprioception, and muscle strength before and after induction of muscle fatigue, and following intervention. RESULTS: In the case of stability typical (ST), a significant difference was observed in pillow with eye open (PO) when a Hot pack was applied (p < .05). The weight distribution index (WDI), showed significant differences in normal eye open (NO) and Normal eye closed (NC) tests when ice packs and hot packs were applied (p < .05). In the dynamic balance assessment using Y-balance, significant differences were observed in all values except for pre- and post-intervention in the medial and lateral directions (p < .05). The recovery of proprioceptive sensation showed a significant difference when ice packs were applied (p < .05). In muscle strength, significant differences were observed in all comparisons between measurement time points (p < .05). CONCLUSION: Rest was most effective for static balance, and cold and warm compresses were most effective in recovering dynamic balance. For proprioception, cold compresses were most effective. Muscle strength had a positive effect on recovery in all three intervention methods. These results show that cold and warm compresses can be useful in the recovery of various functions related to muscle fatigue.

• 근관절건강학회지
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• 제10권2호
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• pp.188-202
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• 2003

The aim of study was to investigate the effects of 12 forms of Sun-style Tai-Chi for arthritis(TCA) on physical symptom(pain, tenderness, swelling fatigue, and blood pressure), physical function(balance, flexibility, grip strength) and social-psychological health status in osteoarthritis(OA) patients and rheumatoid arthritis(RA) patients. This study was done with one group pretest-posttest design. A total 21 arthritis patients(6 OA patient and 15 RA patient) participated in 60 minute session consisting of warm-up exercise 12-main movement including qigong, and cool-down exercise twice a week for 6weeks. Physiological and social-psychological variables were measured before and after TCA 12 form. The researcher who completed a Tai Chi workshop for exercise leaders in Australia and Seoul taught the Tai Chi movement step by step until the patient felt comfort enough to perform them correctly by themselves during the first 4 weeks. At the last 2 weeks, the subject perform 10-15set of these at a session with traditional music to help patients move in a slow tempo. TCA 12 forms program showed significant improvement in fatigue(p=0.039) of rheumatoid arthritis patient and pain(p=0.006), fatigue(p=0.013), tenderness(p=0.032), flexibility(rt arm up, p=0.014, If arm up, P=0.003), grip strength(rt hand, p=0.002, If hand, P=0.003) of osteoarthritis patients. With assessment by Arthritis Impact Measurement Scale 2 questionnaire(AIMS2), physical component(0.002) and social interaction(0.025) on osteoarthritis patients were significantly improved. Evaluation of the participants about TCA exercise noted that the exercise was fairly easy(23.6%), moderately difficult(57.1%), and fairly difficult(14.3%). Considering the result of this study, TCA exercise program was more effective in pain, tenderness, grip strength, flexibility, and physical and social interaction on osteoarthritis patients than rheumatoid arthritis patients. Tai-Chi for arthritis 12 form was an appropriate intensity exercise for osteoarthritis patients.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.258-260
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• 2004

현재의 피로강도 평가법에서는 각종 실험적인 방법 및 이론적인 방법 등 여러 가지 방법으로 피로강도설계를 하고 있는 실정이다. 그리고 이러한 피로특성에 대한 정확한 평가를 위해서 대상구조물에 작용하는 하중성분과 재료 및 구조적인 특성의 상호 연관관계에 대한 연구가 지속되어지고 있다. (중략)

• 대한조선학회논문집
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• 제60권2호
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• pp.65-75
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• 2023

Ships operated at sea for a long time are subjected to various kinds of loads, which may cause various types of damage. Such damages will eventually reduce the strength of hull structures. Therefore, it is necessary to estimate and evaluate the residual strength and remaining fatigue life of aging ships in order to secure structural safety, establish a reasonable maintenance plan, and make a judgment of life extension. For this purpose, the corrosion damage and local denting damage should be measured, fatigue damage estimation should be performed, and material properties of aged steel should be identified. For this study, in order to investigate the mechanical properties of aged steel, steel plates were obtained from a naval ship that reached the end of her life span. The specimens were manufactured from the obtained steel plates, and static and dynamic tensile tests, fatigue tests, and metallographic tests were performed. The mechanical properties obtained from the aged steel plates were compared with those of new steel plates to quantify the aging effect on the mechanical properties of marine steel materials.

• 대한기계학회논문집A
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• 제40권11호
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• pp.979-986
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• 2016

등속조인트의 일종인 트리포드 축은 동력전달용으로 고속열차의 KTX와 KTX-산천에 모두 적용되고 있으며, 동력대차에서 모터 감속장치(MRU)와 차축 감속장치(ARU)를 연결해 고속회전동력을 전달하는 핵심 요소이다. 축 방향의 미끄럼 운동이 가능한 트리포드 축은 열차 구동을 위한 토크를 전달하며, 동력전달 시스템에 과토크 발생 시 축의 퓨즈부가 절단되어 동력을 차단한다. 본 연구에서는 리니어 액추에이터를 이용한 대용량 비틀림 시험장치의 개발과 이를 이용한 트리포드 축의 정적 비틀림 강도와 피로수명을 확인하고자 하였다. 또한 구조해석을 통해 축의 취약부를 파악하고 비틀림 피로해석 결과와 실제 피로시험의 결과를 비교분석하여 비틀림 성능 개선을 위한 설계안을 제시하고자 하였다. 한편 트리포드 축의 피로에 따른 열화를 파악하기 위해 히스테리시스 곡선을 이용하였으며, 히스테리시스 곡선의 기울기 변화를 통해 피로고장 시점을 확인하였다.

• 한국정밀공학회지
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• 제23권1호
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• pp.166-173
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• 2006

This paper investigated strength of a bogie frame for Korean tilting train that is being developed in KRRI. In this study, static load tests based on Japanese Industrial Standard (JIS) were performed. In order to simulate vertical and lateral components generated by tilting link mechanism, four hydraulic actuators were used. The eight load cases such as vertical, lateral, traction, braking and driving gear loads were applied for evaluation of the strength of bogie frame. The stresses measured at the stress concentration points were assessed using Goodman diagram. From the experimental results, structural safety of the bogie frame could be ensured.

• 대한기계학회논문집A
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• 제33권11호
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• pp.1225-1232
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• 2009

This study suggests a structural design process for the upper control arm installed at a vehicle. Static strength and durability are the most important responses in the structural design of a control arm. This study considers the static strength in the optimization process. The inertia relief method for FE analysis is utilized to simulate the static loading conditions. According to the classification of structural optimization, the structural design of a control arm is included in the category of shape optimization. In this study, the metamodel technique using the kriging method is adopted to obtain the minimum weight satisfying the strength constraint. Then, the final design is suggested by considering the durability criteria. The durability assessment is obtained by the index of fatigue durability called the SWT (Smith-Watson-Topper) index. The final optimum shape has been proposed by trial and error method.

• Steel and Composite Structures
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• 제18권4호
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• pp.1045-1062
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• 2015

Concrete-filled circular t steel tubular joints (CFSTJs) in practice are frequently subjected to fluctuated loadings caused by wind, earthquake and so on. As fatigue crack is sensitive to such cyclic loadings, assessment on performance of CFSTJs with crack-like defect attracts more concerns because both high stress concentration at the brace/chord intersection and welding residual stresses along weld toe cause the materials in the region around the intersection to be more brittle. Once crack initiates and propagates along the weld toe, tri-axial stresses in high gradient around the crack front exist, which may bring brittle fracture failure. Additionally, the stiffness and the load carrying capacity of the CFSTJs with crack may decrease due to the weakened connection at the intersection. To study the behaviour of CFSTJs with initial crack, experimental tests have been carried out on three full-scale CFCST T-joints with same configuration. The three specimens include one uncracked joint and two corresponding cracked joints. Load-displacement and load-deformation curves, failure mode and crack propagation are obtained from the experiment measurement. According to the experimental results, it can be found that he load carrying capacity of the cracked joints is decreased by more than 10% compared with the uncracked joint. The effect of crack depth on the load carrying capacity of CFCST T-joints seems to be slight. The failure mode of the cracked CFCST T-joints represents as plastic yielding rather than brittle fracture through experimental observation.

• 한국공작기계학회논문집
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• 제13권3호
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• pp.91-97
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• 2004

The door closer is a typical system which consists of spring and damper. The door closer is a device to close the door more slowly. The virtual prototypes of cylinder-type door closer are developed. The simulations of virtual prototype are performed to obtain the load history of the guide pin. The structural strength assessment of the guide pin is performed to verify a design safety. The fatigue life and damage of the guide pin are predicted using a FEMFAT 4.3h based on the finite element analysis.