• Title/Summary/Keyword: Overload effect

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The relationship between job demands-resources and safety compliance, and the mediating effect of job burnout (직무요구 및 직무자원과 안전순응의 관계에서 직무소진의 매개역할)

  • Lim, Myung Suh;Ahn, Kwan Young
    • Journal of the Korea Safety Management & Science
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    • v.16 no.1
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    • pp.89-99
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    • 2014
  • This paper reviewed the relationship between job demands/resources and safety compliance, and the mediating effect of job burnout. Based on the responses from 247 employees, the results of multiple regression analysis appeared as follow; 1) two demands factors(role ambiguity and role overload) effect positively on safety compliance. 2) job resources factors(autonomy and social support) effect negatively on safety compliance. 3) job burnout effects negatively on safety compliance. 4) job burnout mediates between 4 job demands/resources(role ambiguity and role overload, autonomy, social support) and safety compliance.

Development of RCD Auxiliary Trip Device by using High Precision Current Sensor (고정밀 전류센서를 이용한 RCD 보조트립 장치 개발)

  • Kwak, Dong-Kurl
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.8
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    • pp.1532-1537
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    • 2009
  • Nowadays the diversity and large-capacity of electric appliances are strong effect on electrical fires augment in an alarming way. But, as the inactive response characteristics of the existing RCD (Residual Current protective Device) used on low voltage power distribution lines, so control of overload and electric short circuit faults, major causes of electrical fires, are not enough. Therefore this paper is confirmed the unreliability of the existing RCD by electrical faults simulation and is proposed a auxiliary trip device of RCD by using a high precision current sensor (namely, reed switch) for the prevention of electrical disasters in low voltage power distribution lines caused by overload or electric short circuit faults. The sensitive reed switch in the proposed ATD (auxiliary trip device) exactly detects the increased magnetic flux with the overload or the short current caused by a number of electrical faults, and then rapidly cuts off the existing RCD. The proposed auxiliary trip device of RCD is confirmed the excellent characteristics in response velocity and accuracy in comparison with the conventional circuit breaker through various operation performance analysis. The proposed ATD can also prevent electrical disaster, like as electrical fires, which resulted from the malfunction and inactive response characteristics of the existing RCD.

Determining the Position of Supporter to prevent a Overload applied to the Wedge Type Rail Clamp (과부화 방지를 위한 쐐기형 레일클램프의 지지대 위치 설정)

  • Han, Dong-Seop;Han, Geun-Jo;Lee, Seong-Wook
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2006.11a
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    • pp.294-297
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    • 2006
  • The rail clamp is the device to prevent the crane slips along a rail from the wind blast as well as to locate a container crane in the set position during an operating mode. In this study we conduct the research for determining the proper position of supporter to prevent the overload applied to the rail clamp with respect to the wedge angle in the wedge type rail clamp. The friction force between the jaw pad and the rail to prevent that the crane slips along a rail, when the wind blows, is generated fly the rail-directional wind load. Accordingly the proper position of the supporter to prevent the overload is determined fly analyzing the forces applied to the rail clamp in the wedge working stage. In order to analyze the effect of the wedge angle on the position of supporter, 5-kinds of wedge angles, such as 2, 4, 6, 8, $10^{\circ}$, were adapted as the design parameter, and the wind speed of 40m/s was adapted as the design wind speed criteria.

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A Study on the Delayed-Retardation of Fatigue Crack Growth Following Single Peak Overload (단일과대하중에 의한 피로균열추전의 지대지연현상에 관한 연구)

  • 오세욱;강상훈
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1186-1192
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    • 1990
  • It is well known that the fatigue crack growth retardation following overloads can be estimated reasonably well by the models of Wheeler and Willenborg. These models, however, can not explain the delayed-retardation revealed by every experimental result. This means that they necessarily have some qualitative defects in themselves despite of a fair approximation of quantity. In fact, they did not take into account the effects of the compressive portion of the overload cycle such as the change of reversed plastic zone size. The present study is focused on the acceleration effect in the reversed plastic zone in order to analyze qualitatively delayed-retardation phenomenon following single peak overload on the fatigue crack growth behavior using 2024-T3 aluminum alloy.

Creative Design of Large-Angle Pin Type Load Cell for the Overload Limiter of a Movable Crane (이동식크레인의 과부하방지장치용 광각도 핀형 로드셀의 창의적 설계)

  • Han, Dong Seop;Ha, Jeong Min;Han, Geun Jo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.9 no.1
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    • pp.35-41
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    • 2010
  • An overload limiter is used to prevent its overturning accident during an operation of a movable crane. Recently the indirect measuring method, which measures hoisting load and overturning moment of overload limiter, demands instead of the existing method, which measures only hoisting load. The indirectly measuring method is how to conduct the hoisting load and overturning moment as measuring the load of hydraulic cylinder for a luffing driving of boom. So we need to develop the multi-angular pin type load cell with the measuring angle of ${\pm}10$ degree instead of the existing load cell with the measuring angle of ${\pm}2$ degree. In this study the finite element analysis is conducted to evaluate the effect of the aspect ratio of measuring cross section on the measuring limit of the load cell to develop the many-angular pin type load cell. For this investigation, the aspect ratio of measuring cross section and load applying angle were adopted as design parameters and the stresses of measuring part were evaluated for each parameter.

Prediction of Fatigue Crack Propagation Behavior Under Mixed-Mode Single Overload (혼합모드 단일과대하중 하에서 피로균열 전파거동의 예측)

  • Lee, Jeong-Moo;Song, Sam-Hong
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.359-364
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    • 2004
  • In this study, experiments were tried on the mixed-mode I+II single overloading model which changes the loading mode of overload and fatigue load. Aspects of deformation field in front of the crack which is formed by mixed-mode I+II single overloading were experimentally studied. Then the shape and size of mixed-mode plastic zone were approximately calculated. The propagation behavior of fatigue crack was examined under the test conditions combined by changing the loading mode. The behavior of fatigue cracks were greatly affected by shapes of plastic deformation field and applying mode of fatigue load. Accuracy of prediction and evaluation for fatigue life may be improved by considering all aspects of deformation and behavior of fatigue cracks.

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Effect of specimen thickness on fatigue crack growth and retardation behavior of 7075-T73 aluminum alloy (7075-T73 알루미늄 합금의 피로균열진전거동 및 지연현상에 미치는 두께의 영향)

  • 김정규;박병훈;류석현
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.4
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    • pp.670-679
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    • 1989
  • The constant amplitude loading and 100% single overloading fatigue studies of domestic high tensile 7075-T73 aluminum alloy were performed to exmine the effect of specimen thickness and its mechanisms on fatigue crack growth behavior. The stage II fatigue crack growth rates tend to increase with decreasing specimen thickness under constant amplitude loading condition and this has relation with stress intensity factors and plastic zone size. The amount of retardation by an overload increased with decreasing specimen thickness when the crack depth and baseline stress intensity factors were constant. The crack depth is one of major factors which affect retardation phenomena by an overload and the amount of retardation increase with decreasing the crack depth. Its main mechanisms are crack closure and decreasing of K at the crack tip by branching and deflection of crack. And they are affected by near surface more severely than central portion of specimen.

Improvement to Crack Retardation Models Using ″Interactive Zone Concept″

  • Lee, Ouk-Sub;Chen, Zhi-Wei
    • International Journal of Precision Engineering and Manufacturing
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    • v.3 no.4
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    • pp.72-77
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    • 2002
  • The load interaction effect can be best illustrated by the phenomenon of overload retardation. Some prediction methods for retardation are reviewed and the problems discussed in the present paper. The so-called under-load effect much of the retardation disappears if a very low level minimum stress follows the overload, is also of importance for a prediction model to work properly under random load spectrum. The concept of Interactive Zone (IZ) fully considering reversed plasticity during unloading was discussed. This IZ concept can be combined with existing models to derive some improved models that can naturally take account of the under-load effect. Some simulations by IZ improved models for test under complex load sequences including multiple overloads and both over/under loads are compared with test results. It is seen that the improvement by IZ concept greatly enhanced the ability of existing models to accommodate complex load interaction effects.

A Study on the Effect of Overloading on Fatigue Life (과대하중이 피로수명에 미치는 영향에 관한 연구)

  • 김경수;신병천;심천식;박진영;조형민
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.3
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    • pp.45-53
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    • 2003
  • Ships and ocean structures are subjected to random loads caused by irregular waves. The irregularity of amplitude from random loading affects on fatigue crack growth and fatigue life. However the effects of irregularity of loading on fatigue including random loading have not been explained exactly. Therefore in this paper crack growth tests on DENT specimens under constant-amplitude loading including a single tensile overload are conducted to investigate the effect of overload on crack growth rate. The size of plastic zone and crack growth rate before and after a single tensile overloading are measured using ESPI system. Crack growth retardation model that is characterized by crack growth length and the size of plastic zone was proposed and compared with test result. From the research, the validity of proposed model is examined on crack growth retardation, and consequently fatigue life.