• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.41-48
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• 1989

This paper investigates the relationship between strain hardening exponents(n) of various marine materials and fatigue crack retardation effect after applying single overload. Using the four different sheet materials, following results are obtained. (1) The fatigue crack propagation rate after applying single overload was retarded and the effects of this retardation were closely related to the strain hardening exponent. (2) The larger the strain hardening exponents were, the more were the fatigue crack retardation effects after applying single overload. (3) The considerable crack closure with the applying of a overload was observed in matrals with large strain hardening exponent. When n is smaller than 0.1, the fatigue crack retardation effects are negligible. On the contrary, when n is larger than 0.2 the fatigue crack retardation effects are significant.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.909-914
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• 2007

In this paper, an overload detecting algorithm for an excavator is presented. The proposed overload detecting algorithm is based on the time series analysis especially moving window. The main purpose of this paper is to prevent a damage or crack from the fatigue in advance. 16 channel sensors data are considered and maximum stress is computed by a sensor fusion method every moving window. After the maximum stress every window is compared with a given threshold, this overload detecting algorithm decides overload or not.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.2
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• pp.69-80
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• 2017

In or To use, manage, and preserve sustainable water resources for the current and future generations amid the threat of abnormal climate, it is necessary to establish a smart water grid system, the next-generation intelligent water management system. In this study, sensors, which make use of the five senses to watch, listen, and detect machine vibration, bearing temperature, machine operation sounds, current, voltage, and other symptoms that cannot be verified when the irrigation facilities are running, are used to establish various decision-making criteria appropriate to on-site situations. Based on such criteria, the unmanned conditions in the facilities were verified and analyzed. Existing technologies require on-site workers to check any defects caused by overloading of machines, which is the biggest constraining factor in the application of an unmanned control system for irrigation facilities. The new technology proposed in this study, on the other hand, allows for the unmanned analysis of the existence of machine vibration. This controls the decision-making process of any defect based on the analysis results, and necessary measures are taken automatically, resulting in improved reliability of the unmanned automation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.567-580
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• 2000

This paper proposes an integrated approach, which is independent of specimen geometry and loading type, for predicting the fatigue life of spot welded specimens. We first establish finite element models reflecting the actual specimen behaviors observed on the experimental load-deflection curves of 4 types of single spot welded specimens. Using finite element models elaborately established, we then evaluate fracture parameter J-integral to describe the effects of specimen geometry and loading type on the fatigue life in a comprehensive manner. It is confirmed, however, that J-integral concept alone is insufficient to clearly explain the generalized relationship between load and fatigue life of spot welded specimens. On this ground, we introduce another effective parameter $J_e$ composed of $J_I$, $J_{II}$, $J_{III}$, which has been demonstrated here to more sharply define the relationship between load and fatigue life of 4 types of spot welded specimens. The crack surface displacement method is adopted for decomposition of J, and the mechanism of the mixed mode fracture is also discussed in detail as a motivation of using $J_e$.

• 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.

• Journal of the KSME
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• v.29 no.2
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• pp.118-124
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• 1989

피로파괴의 발생원인을 살펴보면 다음과 같이 4가지로 구별된다. (1) 설계불량 (2) 가공불량 (3) 소재불량 (4) 부적절한 사용 그러나 현재 기계설계시 일반적으로 형상계수 및 충격계수를 포함한 안전율을 여유있게 고려하기 때문에 피로강도가 간접적으로 설계시 반영되어 피로파괴는 주로 가공이나 원소재 불량 및 사용상의 부주의에 의한 경우가 대부분이다. 즉 기계가공 도중에 노치가 유입되어 응력집중을 발생시키거나, 규정된 표면처리 혹은 열처리가 이루어지지 못해서 재료의 피로강도가 저하한 경우가 많으며, 소재 역시 비금속 개재물이 다량 함유되어 있거나 열처리 특성이 조악한 소재가 사용되어 요구되는 강도를 확보하지 못한 경우도 많다. 그 반면 사용자 측에서도 설계강도를 무시한 과부하를 인가하거나, 부식환경 혹은 고온에서 사용하여 피로파괴를 촉진시키는 경우도 있으므로 사용자도 설계조건을 인식하여 그 한계를 넘지 않도록 해야 한다. 피로파괴는 단순한 원인에 의한 경우가 적고 복잡한 여러 형상이 중첩되는 경우가 많기 때문에 해석하기 어려운 경우가 많다. 결국 피로 파괴의 방지는 피로강도를 저하시킬 수 있는 요인들을 종합하여 설계단계에서부터 최종 사용단계까지 지속적인 관리에 의해서만 달성 될 수 있다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.7
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• pp.84-93
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• 2007

The pole transformer is one of the most important facility to insure the stability of electric power supply. which distributes electricity to customers directly. However there are a lot of defects which are caused by manufacturing fails(in 3 years) or deterioration (in 13 years), so we need a more improved transformer which insures quality. This thesis talks about the development of the new-type transformer using the hybrid insulation that is durable thermally, mechanically, and electrically. It would show how to lay out and produce the transformer using the hybrid insulation. And finally we are sure that we could increase the utilization rate of a transformer by 160% as compared with its own capacity through the overload test. Also, we carried out the examination about the short-circuit and insulation with a 100[kVA] model transformer, so that we expound the analysis of magnetic-mechanical forces intensity and the measure for improving short-circuit efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.243-254
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• 2014

It is essential to predict the coil temperature under over load and over speed conditions for reliability in high speed low torque surface mounted PM synchronous motors(SPM). In the present study, the losses and coil temperature are measured under rated condition and calculated under over speed and over load conditions in the three different motors with 35PN440, 25PN250 and 15HTH1000. The heat transfer modeling has been performed based on acquired losses and temperature. The difference of coil temperature between heat transfer modeling and experiment is less than 6.4% under no load, over speed and over load conditions. Subsequently, the coil temperature of the motor with 15HTH1000 is 84.4% of the coil temperature of the motor with 35PN440 when speed is 0.9 and load is 3.0. The output of motor with 15HTH1000 is 85.2% greater than the output of the motor with 35PN440 when the dimensionless coil temperature is 1.0.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.1
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• pp.71-78
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• 1984

본 논문은 왕복동 내연기관의 방열에 관한 연구의 하나로서 디이젤 기관 실린더 헤드와 흡 배기 밸브의 온도 분포와 열유속의 분포를 구한 것이다. 방열 해석은 기관의 정상 작동된 다음의 실린 더 헤드의 열부하가 일정하다고 생각하여 실린더 헤드의 밸드 시이트 양단의 온도와 연소 가스 배출 온도, 흡기 및 냉각수 온도를 측정하고 온도분포 및 열유속을 유한요소법을 적용하여 구하 였다. 본 연구의 결과 실린더 헤드 및 밸브의 과부하는 밸브의 경우에는 밸브 헤드 중심과 밸브 헤드 중심 부근에서 일어나며, 실린더 헤드의 경우에는 헤드 중심부 표면에서 발생하였다. 흡 배 기 밸브 및 물재킷부의 온도 분포 및 열유속의 분포를 주어진 냉각수 온도 조건에 대하여 구한 후 이들을 비교 검토 하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.662-670
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• 2001

We evaluate the effectiveness and validity of J(sub)e, which comprehensively describes the effects of specimen geometry and loading type, in predicting the fatigue life of auto seat belt anchor panel. We first simplify the heat affected zone model to reduce the number of finite elements. We then establish finite element models reflecting the actual overload behavior of 3 types of seat belt anchor specimens. Using finite element models elaborately established, we obtain the effective crack driving parameter J(sub)e composed of its ductility-dependent modal components. It is confirmed that the J(sub)e concept successfully predicts the fatigue life of multi-spot welded panel structures represented by auto seat belt anchors here.