• 한국지진공학회논문집
• /
• 제27권6호
• /
• pp.275-281
• /
• 2023

The demand for high-strength steel is rising due to its economic efficiency. Low-cycle fatigue (LCF) tests have been conducted to investigate the nonlinear behaviors of high-strength steel. Accurate material models must be used to obtain reliable results on seismic performance evaluation using numerical analyses. This study uses the combined hardening model to simulate the LCF behavior of high-strength steel. However, it is challenging and complex to determine material model parameters for specific high-strength steel because a highly nonlinear equation is used in the model, and several parameters need to be resolved. This study used the particle swarm algorithm (PSO) to determine the model parameters based on the LCF test data of HSA 650 steel. It is shown that the model with parameter values selected from the PSO accurately simulates the measured LCF curves.

• 한국산학기술학회논문지
• /
• 제17권7호
• /
• pp.585-596
• /
• 2016

본 연구는 청소년의 스트레스 인지, 식생활, 신체활동, 음주, 흡연, 잠으로 피로회복 정도에 따라 주관적 행복감에 미치는 영향을 파악하고, 이를 바탕으로 향후 청소년의 주관적 행복감을 향상시키는 실질적인 방안을 위한 기초자료를 제공하고자 한다. 2015년 제11차 청소년건강행태온라인조사 원시자료의 9,599명을 대상으로 IBM SPSS 20.0과 IBM SPSS AMOS 23 프로그램을 이용하였으며, 빈도분석, 기술통계, 상관분석, 부트스트래핑과 팬텀변수를 이용하였다. 연구결과, 주관적 행복감에 가장 많은 영향을 미치는 직접효과는 스트레스 인지(${\beta}=-.457$, p =. 005), 잠으로 피로회복(${\beta}=.136$, p = .004), 신체활동(${\beta}=.055$, p = .005), 식생활(${\beta}=-.035$, p = .014), 흡연(${\beta}=-.030$, p = .011이었다. 스트레스 인지가 주관적 행복감으로 가는 경로의 간접효과(${\beta}=-.052$, p = .006)가 있었으며, 팬텀변수를 이용하여 다중매개의 간접효과 크기와 유의도를 분석한 결과 스트레스 인지와 주관적 행복감 사이에 간접효과는 잠으로 피로회복(${\beta}=-.041$, p = .001), 신체활동(${\beta}=-.007$, p = .003), 식생활(${\beta}=-.003$, p = .008), 흡연(${\beta}=-.002$, p = .001)순으로 나타났으며, 음주는(${\beta}=000$, p = .636) 간접효과가 없었다. 그러므로 청소년의 주관적 행복감을 증진시키기 위하여 다학제간의 협력이 요구되며 가정, 학교, 지역사회 및 국가차원의 교육환경 개선과 인력 및 재정적 지원이 모색되어야 할 것이다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제23권6호
• /
• pp.77-83
• /
• 2019

원자력발전소에 지진격리장치를 설치하면 지진에 의한 하중을 지진격리장치가 담당하면서 설치 전보다 큰 변위가 발생하게 될 것으로 예상되며, 변위증가에 따라 일부 설비의 지진리스크가 증가될 가능성이 있다. 특히 지진격리된 구조물과 일반 구조물을 연결하는 설비인 배관 시스템의 경우 지진리스크가 크게 증가될 것으로 예상된다. 본 연구에서는 원자력발전소 배관 시스템의 취약부위인 강재 배관 Tee의 한계상태를 누수로 정의하고 면내반복가력시험을 수행하였다. 강재 배관 Tee의 모멘트와 변형각은 기존의 센서를 이용한 계측이 어려우므로 이미지 신호를 이용하여 측정하였다. 본 연구에서는 3인치 강재 배관 Tee의 모멘트와 변형각의 관계를 이용한 누수 선도 및 저주기 피로 곡선들을 제시하였다.

• Structural Engineering and Mechanics
• /
• 제74권4호
• /
• pp.567-576
• /
• 2020

Considerable controversy surrounds the choice of the best abutment type for implant prosthetics. The two most common structures are hex and non-hex abutments. The non-hex abutment typically furnishes a larger contact area between itself and the implant than that provided by a hex structure. However, when a hex abutment is loaded, the position of its contact area may be deeper than that of a non-hex abutment. Hence, the purpose of this study is to determine the different biomechanical behaviors of an internal bone-level implant based on the abutment type-hex or non-hex-and clinical crown length under static and cyclic loadings using finite element analysis (FEA). The hex structure was found to increase the implant and abutment stability more than the nonhex structure among several criteria. The use of the hex structure resulted in a smaller volume of bone tissues being at risk of hypertrophy and fatigue failure. It also reduced micromovement (separation) between the implant components, which is significantly related to the pumping effect and possible inflammation. Both static and fatigue analyses, used to examine short- and long-term stability, demonstrated the advantages of the hex abutment over the non-hex type for the stability of the implant components. Moreover, although its impact was not as significant as that of the abutment type, a large crown-implant ratio (CIR) increased bone strain and stress in the implant components, particularly under oblique loading.

• 한국철도학회논문집
• /
• 제17권4호
• /
• pp.260-269
• /
• 2014

본 논문의 목적은 철도교량 단부 전환부 궤도의 구조적 거동특성을 평가하는 것이다. 국내 고속철도 교량상 궤도표준단면을 이용하여 전환부 궤도구조를 설계 및 제작하여 피로시험 전, 후에 대한 전환부 궤도시스템의 중립축 및 동특성(고유진동수 및 감쇠비)의 변화를 비롯하여 피로균열 발생경향을 수치해석 결과와 비교, 검토하였다. 연구결과, 국내 고속철도 궤도설계기준을 준용하여 설계한 전환부 궤도시스템에 대한 동특성을 실험적으로 산정하였으며 국내 철도하중 및 충격효과를 고려한 피로하중에 대한 구조적 건전성을 실험 및 해석적으로 입증하였다.

• 성인간호학회지
• /
• 제26권4호
• /
• pp.413-423
• /
• 2014

Purpose: This study was aimed to identify NANDA-NOC-NIC linkage in cancer patients receiving chemotherapy. Methods: This study was a descriptive study conducted in three steps. First, nursing diagnoses were identified from the electronic nursing records. Second, content validity of nursing diagnoses and outcomes were evaluated. Third, major nursing interventions associated with expected nursing outcomes were collected from 97 nurses who worked in the oncology unit. Data were analyzed using descriptive statistics. Results: Four major nursing diagnoses were identified: acute pain, knowledge deficit, health seeking behaviors, and ineffective protection. Associated with each respective diagnosis, 3 major outcomes (pain level, pain control, and comfort state) for acute pain, 8 major nursing outcomes (diet, disease process, treatment regimen, illness, ostomy care, prescribed activity, health behavior, and infection management) for knowledge deficit, 4 major outcomes (health promoting behavior, health promotion, health belief, and knowledge: health resource) for health seeking behaviors, and 3 major outcomes (fatigue level, immune status, and nutritional status) for ineffective protection were identified. In addition, nursing interventions frequently used in clinical practice for each major nursing outcome were identified. Conclusion: The identified NANDA-NOC-NIC linkage can contribute to improving the applications of nursing process and care plans.

• Tribology and Lubricants
• /
• 제18권2호
• /
• pp.167-172
• /
• 2002

The wear behaviors of ultrahigh molecular weight polyethylene pins against titanium alloy and stainless steel disks moving in two different kinematic motion were investigated by conducting repeat pass rotational sliding and linear reciprocal sliding wear tests. Linear reciprocal motion wore more the polyethylene pin than did repeat pass rotational motion for both disk materials. It means that the repeated directional change of contact stresses generates more wear debris in polyethylene. For the linear reciprocal sliding tests, titanium alloy disks were damaged with some scratches after one million cycles but no surface damage was observed on the polyethylene pins. On the other hand, fur the repeat pass rotational sliding tests, all titanium alloy disks were severely abraded on the entire region of sliding track. This phenomenon can be interpreted by that stress fatigue under repeated sliding contact initiated titanium oxide layer wear particles from disk surface, and these hard particles were embedded into polyethylene pin and then they severely abraded the disk surface. From these results it can be concluded that the kinematic motion in pin-on-disk wear tests play a crucial role on the wear behaviors of UHMWPE pins against titanium alloy and stainless steef discs.

• Nuclear Engineering and Technology
• /
• 제45권2호
• /
• pp.265-276
• /
• 2013

Pressure tubes made of Zr-2.5 wt% Nb alloy are important components consisting reactor coolant pressure boundary of a pressurized heavy water reactor, in which unanticipated through-wall cracks and rupture may occur due to a delayed hydride cracking (DHC). The Canadian Standards Association has provided deterministic and probabilistic structural integrity evaluation procedures to protect pressure tubes against DHC. However, intuitive understanding and subsequent assessment of flaw behaviors are still insufficient due to complex degradation mechanisms and diverse influential parameters of DHC compared with those of stress corrosion cracking and fatigue crack growth phenomena. In the present study, a deterministic flaw assessment program was developed and applied for systematic integrity assessment of the pressure tubes. Based on the examination results dealing with effects of flaw shapes, pressure tube dimensional changes, hydrogen concentrations of pressure tubes and plant operation scenarios, a simple and rough method for effective cooldown operation was proposed to minimize DHC risks. The developed deterministic assessment program for pressure tubes can be used to derive further technical bases for probabilistic damage frequency assessment.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
• /
• pp.67-71
• /
• 2000

The wear behaviors of ultrahigh molecular weight polyethylene pins against titanium alloy and stainless steel disks moving in two different kinematic motion were investigated by conducting repeat pass rotational sliding and linear reciprocal sliding wear tests. Linear reciprocal motion wore more the polyethylene pin than did repeat pass rotational motion for both disk materials. It means that the repeated directional change of contact stresses generates more wear debris in polyethylene. For the linear reciprocal sliding tests, titanium alloy disks were damaged with some scratches after one million cycles but no surface damage was observed on the polyethylene pins. On the other hand, for the repeat pass rotational sliding tests, all titanium alloy disks were severely abraded on the entire region of sliding track. This phenomenon can be interpreted by that stress fatigue under repeated sliding contact initiated titanium oxide layer wear particles from disk surface, and these hard particles were embedded into polyethylene pin and then they severely abraded the disk surface. From these results it can be concluded that the kinematic motion in pin-on-disk wear tests play a crucial role on the wear behaviors of UHMWPE pins against titanium alloy and stainless steel disks.

• 한국압력기기공학회 논문집
• /
• 제16권2호
• /
• pp.58-67
• /
• 2020

This study presents cyclic stress-strain and tensile test results at room temperature (RT) and 316℃ using cold-worked TP304 stainless steel base and weld metals. By comparing the cyclic hardening/softening behavior and failure cycle of cold-worked materials with those of irradiated austenitic stainless steels, the feasibility of simulating the irradiation effect on cyclic deformation and failure behaviors of TP304 stainless steel base and weld metals was investigated. It was found that, in the absence of strain-induced martensite trasformation, cold-working could properly simulate the change in cyclic hardening/softening behavior of TP304 stainless steel base and weld metals due to neutron irradiation. It was also recognized that cold-working could adequately simulate the reduction in failure cycles of TP304 stainless steel base and weld metals due to neutron irradition in the low-cycle fatigue region.