• 한국자동차공학회논문집
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• 제20권1호
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• pp.141-146
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• 2012

Aluminum alloys have been used with various thicknesses suitable for light weight of structure. It is known that the thickness effect of material is an important factor affecting fatigue crack propagation under constant fatigue stress condition. In this work, we presented the behavior of fatigue crack propagation in thin plate compared to thick plate Al 2024-T3 alloy with referred thickness effect in a correlative equation determined by the shape factor and the loading factor. We chose two factors that are used in the correlative equation with considering that the experiments were carried out under a constant fatigue stress condition. The thickness ratio of thin plate compared to thick plate and the equivalent effective stress intensity factor ratio depending on thickness were chosen as shape and loading factors. A correlative equation is utilized to determine the equivalent effective stress intensity factor range of thin plate and identify the degree of increasing phenomenon of fatigue life in thin plate compared to thick plate.

• Journal of Mechanical Science and Technology
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• 제18권6호
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• pp.915-923
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• 2004

This study investigated the fatigue lives and mechanical properties of the carbon black filled natural rubber for the vibration-proof parts of the railway vehicle and automobile. The carbon blacks were one of the sources of crack nucleation and crack propagation in the rubber matrix, like the cementite and the maganese sulfide in iron matrix. Different kinds of carbon blacks resulted in different fatigue lives, critical J-values, and fracture morphologies. It was noticed that the critical J-value remained almost the same regardless of the length of a pre-crack. In addition, different kinds of carbon blacks generated different fracture morphologies, and microscopic and macroscopic roughnesses. The critical J-value has linear relations to the roughness, and it seemed related to the size distribution of carbon black particles. By reviewing all the experi-mental data, we found the factors that were related to the fatigue lives, and the logarithmic value of the fatigue life could be linearly expressed by the combination of the critical J-value and the macroscopic roughness. We also proposed a new estimative equation of fatigue life.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.474-478
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• 2008

In this paper, the technique to reinforce the structure using the sensitivity information is proposed. Design variables related to the geometry of structure at fatigue fracture points are determined and sensitivities of fatigue life at fracture points with respect to the variation of design variables are calculated. Then the vector composed of gaps between the target life and initial life cycles at fracture points is calculated. The linear algebraic equation to solve the variation of design variables is composed. From the equation, the design variables for reinforced structure are determined.

• 대한기계학회논문집A
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• 제33권11호
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• pp.1341-1346
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• 2009

In this paper, the technique to reinforce the durability performance of structure using the sensitivity information for the frame structure is applied. The fatigue life calculation for the frame structure is performed from the quasi-static and transient analysis and the characteristics of two methods are compared for the fatigue analysis. Then the reinforcement technique is applied. First, some design variables related to the locations of fatigue failure is selected. Then sensitivities of fatigue life at fracture points with respect to the variation of design variables are calculated and the vector composed of gaps between the target life and initial life cycles is calculated. If the number of fatigue fracture points is same as the number of design variables, the variations of the design variables are calculated from the linear algebraic equation. If not, the variations of the design variables are calculated from the optimization formulation with the constraints.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.317-320
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• 2008

Between traffic-induced vibration of a bridge and fatigue damage of its attached structures are very closely related. But any evaluation and design method considering the fatigue damage is not established yet. As an experimental method of evaluation of the fatigue durability, a method based on cumulative damage using a stress range histogram has been often used. However, to use the method, the fatigue durability of unmeasured points could not be evaluated. Then, in this paper, dynamic analysis of a sign frame on a bridge is carried out based on the vibration data of the bridge. And model optimization was performed for good agreement between measured responses and computed responses. As a result, we could get stress range histograms and calculate fatigue durability of unmeasured points.

• 오토저널
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• 제5권1호
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• pp.32-44
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• 1983

In case of $K_{Imax}$ < $K_{Iscc}$, the corrosion fatigue of high strength steel in 0.1N $H_{2}$S $O_{4}$ solution and 3.5% salt water is as follows. 1. The fatigue life shortens in order of 3.5% salt water and 0.1N $H_{2}$S $o_{4}$ solution. 2. The fatigue crack growth rate in air is obtained as the following equation. (dc/dN)$_{atr}$=7.23*10$^{-6}$ (.DELTA. K)$^{2.23}$ 3. The corrosion fatigue crack growth rate in environment is divided into three regions, that is, First Region, Second Region and Third Region from the small cyclic stress intensity. 4. The formation rate of the active surface on metal is slower than the mechano-chemical reaction rate in First Region. The crack growth rate depends on time and the cyclic stress intensity and is expressed as the following equation. (dc/dN)$_{I}$=C(/DELTA. K)$^{\delta}$ 5. The formation rate of the active surface is faster than the mechano-chemical reaction rate in Second Region and the synergistic effect by stress and corrosion becomes slow. In case the fatigue load is large, we have the critical crack growth rate which is not related to the cyclic stress intensity. 6. The corrosion crack growth rate by the mechano-chemical reaction is the same in $H_{2}$S $O_{4}$ solution and salt water, so Hydrogen accelerates the crack growth. 7. The environment has no effect on the corrosion fatigue crack growth rate in Third Region. 8. In First Region and Second Region, dimple is observed on the fatigue fracture surface in 0.1N $H_{2}$S $O_{4}$ solution. 9. The striation is observed in any environment as in air in Third Region and its interval approximately coincide with the crack growth rate.ate.e.e.

• 한국정보시스템학회지:정보시스템연구
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• 제25권2호
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• pp.111-129
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• 2016

Purpose Today, world-wide societies share their daily life and many communities exchange their information through the explosive developed SNS and the social media systems. However, many SNS fatigue related factors forced the discontinuance of SNS. This paper is aim to examine effect of SNS feature and negative emotion to figure out the reason of SNS discontinuance. This is verifying the effect of maintenance of SNS, security concern and psychological concern on SNS fatigue and the effect of upward/lateral comparison on negative emotion. Moreover, the effect of SNS fatigue and negative concern on the SNS discontinuance intention was examined. Design/methodology/approach This research used to the survey method to test its hypotheses and the survey population is Facebook SNS users. A software tool called AMOS 18 is used to analyze the structural equation model. Findings The results showed that maintenance of SNS, security concern and psychological concern had a positive effect on SNS fatigue respectively and upward/lateral comparison did on negative emotion. In addition, SNS fatigue and negative emotion had significant effect on discontinuance intention.

• 한국산학기술학회논문지
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• 제11권6호
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• pp.2169-2177
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• 2010

본 연구는 공무원들의 스트레스나 피로수준과 같은 사회심리적 건강상태가 그들의 직급, 근무경력 등의 직업관련 특성이나 업무요구도, 업무자율성, 직장 내에서의 사회적 지지와 같은 직무스트레스 내용에 의해 영향을 받고 있는지를 구조방정식모형을 통하여 검토하고자 시도하였다. 연구대상은 대전광역시의 5개 정부 공공기관에 근무하는 일반 사무직 행정공무원 805명이었으며, 자료 수집은 2009년 10월 1일부터 11월 30일까지의 기간 동안에 표준화된 자기기입식 설문지(self-administered questionnaire)를 사용하여 실시하였다. 연구결과, 공무원들의 스트레스 및 피로수준은 직급, 근무경력, 업무만족도, 업무자율성, 상사의 지지도 및 동료의 지지도와는 유의한 음의 상관관계를 나타낸 반면, 년 간 결근일수, 업무요구도와는 유의한 양의 상관관계를 나타내었다. 구조방정식모형 분석 결과 연구대상자들의 직무스트레스 요인은 직업관련 특성 요인보다 사회심리적 건강상태에 더 큰 영향을 미쳤으며, 직무스트레스가 높을수록 사회심리적 건강상태를 나타내는 스트레스와 피로수준을 높여주는 것으로 나타났다. 한편, 직업관련 특성의 인지정도가 높을수록 직무스트레스 요인을 감소시키는 효과가 있는 것으로 나타났다. 따라서 공무원들의 스트레스나 피로를 감소시키기기 위해서는 직업관련 특성에 따른 직무내용의 개선을 위한 프로그램의 개발 및 시행이 필요할 것으로 생각된다.

• 한국해양공학회지
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• 제8권1호
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• pp.114-122
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• 1994

X-ray stress constant, K, was determined for the diffraction line of (211)plane by using Cr-K$\alpha$ radiation. K was -340.87 MPa/deg. Fatigue crack propagation tests of SS41 steel were conducted under stress ratios of 0.1, 0.3 and 0.5. The half-value breadth of X-ray diffraction profile was measured at and beneath the fracture surface. The half-value breadth, B, on the fracture surface was found to increase with increasing $K_max$. The value of B was influenced by stress ratio in SS41 steel. The half-value breadth took the maximum value at the borden of reversed plastic zone, while it approached to the initial (pre-fatigue) value near the boundary of monotonic plastic zone. The maximum depth of the plasticzone was evaluated on the basis of the half-value breadth distribution. The depth $\omega$$_y$ is related to $K_max$by the following equation : $\omega$$_y$ = $\alpha$($K_max$/$\sigma$$_y$$)^2$ where .sigma.$\sigma$$_y$ is the yield strength obtength obtained in tension test .alpha.is 0.136 for SS41 steel.

• 한국콘텐츠학회논문지
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• 제17권12호
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• pp.25-33
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• 2017

상호작용 속도의 증가는 과잉 관계(over-relations)의 문제가 나타날 수 있다. 과잉 관계로 인한 심리적, 시간적 부담으로 SNS에 대한 피로감을 느껴 SNS 이용을 기피하는 이용자들이 생기고 있다. SNS 피로감(fatigue), SNS 불안감(anxiety) 등 SNS 이용으로 인해 발생된 부작용에 관한 사항들은 'SNS 스트레스'라고 볼 수 있다. 본 연구에서는 SNS에 대한 부정적인 측면을 스트레스라는 관점에서 살펴보며, 스트레스의 발생 원인을 상호작용의 과잉에서 찾고자 한다. 본 연구는 페이스북 이용자들을 대상으로 총 261부를 분석에 활용하였다. SEM(Structural Equation Model) 분석 결과, 모든 연구가설이 채택되었다. 정보공유와 커뮤니케이션 모두 사회적 상호작용 과부하에 긍정적인 영향을 미쳤으며, 사회적 상호작용 과부하가 스트레스를 불러일으키는 것으로 나타났다. 본 연구는 실증적으로 SNS 피로감을 유발시키는 원인으로 상호작용성을 대입해 SNS가 가진 특징이 오히려 부정적인 결과를 초래할 수 있다는 것을 검증하였다는 점에서 의의가 있다.