• 제목/요약/키워드: Overload

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다중 과하중에 의한 A1 7075-T6 합금의 피로균열 성장지연현상에 관한 연구 (A Study on Fatigue Crack Growth Retardation Phenomena of Al 7075--T6 Alloy under Multiple overload(I))

  • 이택순;이유태
    • 한국해양공학회지
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    • 제6권1호
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    • pp.96-104
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    • 1992
  • Aircraft structures and engineering structures are always subject to variable amplitude loads. Variable amplitude loads include some kind of loading history; for example, constant amplitude load, single peak overload and block overload etc. Crack growth under variable amplitude loading exhibits retardation effect. In this study, the 4 point bending fatigue test was performed by hydrolic servo fatigue testing machine on 7075-T6 Al-alloy. The retardation effect of overload ratio and numbers of overload cycle was quantitatively studied. 1) Change of retardation effect against increment of overload ratio is more evident when the multiple overload is applied than single overload is done. 2) The number of overload cycle is very important factor about the crack growth retardation effect when the overload ratio is more than 1.75; that is not when the overload ratio is less than 1.75. 3) Overload affected zone size increased gradually by increment of crack growth retardation effect. 4) Crack driving force is more greatly reduced when the crack tip branched off two direction than it sloped to one direction.

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실시간 감시를 이용한 배전용변압기 과부하 평가 시스템 개발 (Development of Overload Evaluation System of Distribution Transformers using Real-Time Monitoring)

  • 박창호;윤상윤
    • 전기학회논문지
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    • 제59권10호
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    • pp.1741-1747
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    • 2010
  • The development of overload management systems for distribution transformers offers new opportunities for improving the reliability of distribution systems. It allows network planners to optimize the system resource utilization and investment cost. Such an improvement in the flexibility of the distribution network is only possible if the operator has more accurate knowledge of the realtime conditions of distribution transformers. In this paper, we present an improved overload decision system for distribution transformers using realtime monitoring data. Our study can be categorized into two parts: (a) improvement in the criteria for judging the overload conditions of distribution transformers and (b) development of an overload evaluation system using realtime monitoring data. In order to determine the overload criteria, overload experiments are performed on sample transformers; the results of these experiments are used to define the relationship between the transformer overload and the increase in the top-oil temperature. To verify the accuracy of the experimental results, field tests are performed using specially manufactured transformers, the loads and top-oil temperatures of which can be measured. For arriving at online overload decisions, we propose methods whereby the measured load curve can be converted into an overload characteristic curve and the overload time can be calculated for any load condition. The developed system is able to evaluate the overload for individual distribution transformers and calculate the losses using realtime monitoring data.

소셜 미디어 과부하가 사용자의 비의도적 회피 행동에 미치는 영향 (The Impact of Social Media Overload on Users' Unintentional Avoidance Behavior)

  • 차오신;오세환
    • 한국정보시스템학회지:정보시스템연구
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    • 제32권3호
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    • pp.165-181
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    • 2023
  • Purpose Digital platforms, together with the innovative technologies of modern society, are accelerating the digital innovation of the entire economy and society. Although social media platforms are gradually integrated into daily life, due to social media overload, users limit their use of the platform for a certain period of time or eventually choose to stop using it. In the context of social media platform, the purpose of this paper is to study the effects of information overload, social overload and system function overload on users' unintentional avoidance behavior, mediated by fatique and dissatisfaction. Design/methodology/approach This study empirically examines the influence of social media overload characteristics on users' unintentional avoidance behavior of platform utilization using the S-O-R framework. Data from 236 Chinese social media users were collected through a questionnaire survey, and the hypotheses were validated by evaluating the research model using the SmartPLS 4.0 program using Partial Least Square (PLS) method. Findings According to the empirical analysis result, based on the S-O-R model, first, it is confirmed that information overload and system feature overload have significant positive(+) effects on fatigue. Second, this study finds that information overload, social overload and fatigue have significant positive(+) effects on dissatisfaction. Thirdly, fatigue and dissatisfaction have significant positive(+) effects on unintentional avoidance. In addition, social overload has no significant effect on fatigue, while system feature overload has no significant effect on dissatisfaction.

열동형 과부하 계전기의 메커니즘 해석 (Mechanism Analysis of Thermal Overload Relay)

  • 이경구
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1999년도 하계학술대회 논문집 A
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    • pp.287-289
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    • 1999
  • This paper proposes mechanism analysis in thermal overload relay. Overload protection performance is closely connected with mechanism of thermal overload relay. In shortage of analytical technique, we have experienced many difficulties in development of thermal overload relay. We applied analytical results to develop optimum thermal overload relay.

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스마트 주택 자동화를 위한 주택 전기과부하 경보 성능 평가 시스템 개발 (Development of a Digital Home Electric Overload Alarm Performance Evaluation System for Smart Home Automation)

  • 고윤석
    • 한국전자통신학회논문지
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    • 제14권2호
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    • pp.339-344
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    • 2019
  • 본 논문에서는 주택 전기 과부하로 인한 전기화재 피해를 최소화할 수 있는 스마트 주택 자동화를 위한 DSP 기반의 디지털 주택 과부하 경보기를 실험 제작하였다. 그리고 주택 과부하 경보 기술의 유효성을 검증하기 위해서 인공적으로 과부하를 발생시킬 수 있는 하나의 전기 과부하 경보 성능 평가 시스템을 설계, 개발, 구축하고, 과부하 시험을 통해 개발된 주택 과부하 경보기의 유효성을 검증하였다. 특히, EMTP-RV를 이용하여 과부하 시험 모델을 개발하고 과부하 시험을 모의, 계측결과와 비교함으로서 과부하 성능 검증결과의 신뢰성을 확인하였다.

Antecedents of News Consumers' Perceived Information Overload and News Consumption Pattern in the USA

  • Lee, Sun Kyong;Kim, Kyun Soo;Koh, Joon
    • International Journal of Contents
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    • 제12권3호
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    • pp.1-11
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    • 2016
  • This exploratory study examines the critical factors associated with news consumers' perception of information overload and news consumption patterns. An online survey was conducted with Qualtrics panels (N = 1001). The demographics and three antecedent factors of perceived information overload were considered including the frequency of news access through multiple media platforms, level of attention to news, and interest in news. Three news consumption patterns were investigated as possible consequences of perceived information overload: news avoidance, selective exposure, and willingness to pay for news. The results of hierarchical regression analyses revealed a meaningful distinction between general and news information overload. Overall, news consumers who paid more attention to news through newer media/platforms/devices perceived higher levels of information overload, were more willing to pay for the news, and often avoided news or selectively exposed themselves to certain sources of news to manage news information overload.

단일 과대 하중에 의한 균열 성장 지연 거동 예측 (Prediction of Crack Growth Retardation Behavior by Single Overload)

  • 송삼흥;최진호;김기석
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 1996년도 추계학술대회 논문집
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    • pp.928-932
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    • 1996
  • Single overload fatigue tests with overload sizes ranging from 50% and 100% have been performed to investing ate the fatigue crack growth retardation behavior. A modified and experimental method of Willenborg's model for prediction of crack growth retardation behavior has been developed, based on evaluations of equivalent plastic zone size (EPZS) changing its size along the overload plastic zone boundary. The minimum crack growth rates of each overload size are linearly decreased with overload size increasing, but fatigue lives extended by single overload are increasing much more unlike the crack growth rates. Comparisons of crack growth behavior predicted by EPZS model and Willenborg model have shown that the EPZS model accounts for overload effects better than Willenborg model. These effects include delayed retardation, large retardation region, minimum crack growth rate, and the increase rate of crack growth rate in the region crack growth rate recovered.

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강의 피로균열지연거동에 미치는 과대하중의 영향과 통계적 변동에 관한 연구 (Influence of overload on the fatigue crack growth retardation and the statistical variation)

  • 김선진;남기우;김종훈;이창용;박은희;서상하
    • 한국해양공학회지
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    • 제11권3호
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    • pp.76-88
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    • 1997
  • Constant .DELTA.K fatigue crack growth rate experiments were performed by applying an intermediate single and multiple overload for structural steel, SM45C. The purpose of the present study is to investigate the influence of multiple overloads at various stress intensity factor ranges and the effect of statistical variability of crack retardation behavior. The normalized delayed load cycle, delayed crack length and the minimum crack growth rate are increased with increasing baseline stress intensity factor range when the overload ratio and the number of overload application were constant. The crack retardation under low baseline stress intensity factor range increases by increasing the number of overload application, but the minimum crack growth rate decreases by increasing the number of overload application. A strong linear correlation exists between the minimum crack growth rate and the number of overload applications. And, it was observed that the variability in the crack growth retardation behavior are presented, the probability distribution functions of delayed load cycle, delayed crack length and crack growth life are 2-parameter Weibull. The coefficient of variation of delayed load cycle and delayed crack length for the number of 10 overload applications data are 14.8 and 9.2%, respectively.

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"잡 크래프팅이 안전을 만든다." : 직무 과부하가 안전 행동에 미치는 영향 ("Job Crafting Makes Safety": The Effect of Work Overload on)

  • 김병직
    • 대한안전경영과학회지
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    • 제24권1호
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    • pp.81-89
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    • 2022
  • Since the competitive environment, work overload among employees has been increasing. The purpose of this paper is to investigate the impact of work overload on safety behavior and its intermediating mechanisms. In specific, this paper delves into the mediating effect of job stress, as well as the moderating effect of job crafting in the association between work overload and job stress. To empirically test the hypotheses, this study utilized survey data from 168 Korean employees by conducting structural equation modeling(SEM) analysis. The results demonstrated that work overload has a positive (+) influence on job stress, which has a negative (-) influence on safety behavior. Moreover, job stress mediated the association between work overload and safety behavior. Furthermore, job crafting moderated the work overload-safety behavior link.

단일 과대하중에 의한 레이저 용접 판재의 피로균열 전파거동 (Effect of Single Overload on the Fatigue Crack Growth Behavior of Laser Welded Sheet Metal)

  • 곽대순;김석환;오택열
    • 한국정밀공학회지
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    • 제21권4호
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    • pp.161-169
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    • 2004
  • In this study, we investigated fatigue crack growth behavior of laser welded sheet metal due to a single overload. Fatigue specimens were made using butt joint of cold rolled sheet metal that was welded by $CO_2$ laser. The fatigue crack propagation tests were performed in such a way that fatigue loading was parallel to the weld line while crack propagation was perpendicular to the weld line. Single overload was applied when fatigue crack tip was arrived near the weld line. The distances between the crack tip and the weld line at which a single overload was applied were 6, 4 and 2mm. The effect of specimen thickness and overload ratio on the fatigue behavior was determined. The plastic zone size of crack tip due to the single overload was determined from the finite element analysis. For investigating fatigue crack growth behavior, we used different thickness specimen 0.9mm and 2.0mm, and variable overload ratio applied fatigue crack propagation test. Also we used finite element analysis for investigating the plastic zone size of crack tip when single overload applied