• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.283-288
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• 2005

Application of semiconductor sensors has widely spreaded into various industries because those have several merits like easy miniaturization and batch production comparison with previous mechanical sensors. But external conditions such as thermal and repetitive load have a bad effect on sensors's lifetime. Especially, this paper was focused on fatigue life of a interconnect made by various materials. Firstly we implemented the stress analysis for interconnect under thermal load and wording pressure. And the fatigue lifetime of each material was induced by Manson & Coffin Equation using the plastic stress-strain curve obtained by the plastic-elastic Finite Element Analysis.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.6
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• pp.675-680
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• 2016

This is a study for the improvement of the defected elevator spar in operating aircraft. The elevator spar web holes were analyzed to find out the cause of the cracks. The fatigue striations were observed and the cracks occurred by the repetitive stresses during the elevator works. Also the outboard connection structure of the elevator and horizontal stabilizer was more weak shape than the inboard. The design changes were recommended and the analyses were performed to verify the improvement of the changed shapes.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.43-54
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• 1987

Cumulative damage characteristics of concrete, on which rapetitive loads are applied, are investigated. Preliminarily, a series of uniaxial compression tests on cylindrical specimens of plain concrete is carried out to find out that, among various factors, stress levels of repetitive loadings and loading order are the most governing factors of cumulative damage of concrete. Based on this preliminary study, fatigue tests are carried out applying two levels of stresses, stepwisely. As a result, it is found that characteristics of cumulative damage of concrete are governed by nonlinear relationships and do not follow Miner's linear theory. It is also observed that cumulative damage characteristics and static strengths of concrete vary with loading history of stresses. Empirical equations which may be useful in predicting fatigue characteristics and remaining life of concrete stuctures are proposed for concrete subjected two stress levels.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.104-107
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• 2004

The crack widths of reinforced concrete flexural members are influenced by repetitive fatigue loadings. The bond stress-slip relation is necessary to estimate these crack widths realistically. The purpose of the present study is, therefore, to propose a realistic model for bond stress-slip relation under repeated loading. To this end, several series of tests were conducted to explore the bond-slip behavior under repeated loadings. Three different bond stress levels with various number of load cycles were considered in the tests. The present tests indicate that the bond strength and the slip at peak bond stress are not influenced much by repeated loading if bond failure does not occur. However, the values of loaded slip and residual slip increase with the increase of load cycles. The bond stress after repeated loading approaches the ultimate bond stress under monotonic loading and the increase of bond stress after repeated loading becomes sharper as the number of repeated loads increases. The bond stress-slip relation after repeated loading was derived as a function of residual slip, bond stress level, and the number of load cycles. The models for slip and residual slip were also derived from the present test data. The number of cycles to bond slip failure was derived on the basis of safe fatigue criterion, i.e. maximum slip criterion at ultimate bond stress.

• Tribology and Lubricants
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• v.27 no.1
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• pp.40-44
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• 2011

The object of this study is to investigate influences of supplied lubricant quantities on spur gear's pitting life. Pitting is a sort of contact fatigue failures and made by a repetitive load. Basically, pitting is difficult to predict its life by an analysis due to many factors to be considered about tribology problems. In this paper, pitting life was proved by experiment using two roller machine. For a contact fatigue test, operating circumstances should be considered. During the test, temperature and lubricant quantities are considered and to investigate an influence of lubricant quantities, a comparison between optimally enough and not enough lubricant quantity was implemented.

• Journal of the Korea Convergence Society
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• v.6 no.5
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• pp.85-90
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• 2015

In this study, the life evaluation due to the structural configuration of bumper attached at the front side of ATV vehicle is studied on the basis of fatigue analysis. As the purpose of this study, the characteristic of bumper exposed on the repetitive loading condition like the vibration is understood. The position of crack happened at the fatigue situation is grasped in advance and complemented in advance. It is considered that the multipurpose vehicle is designed to not be driven on the paved general road but the rough road like the unpaved load. And the weak part of bumper is understood through the study of life evaluation on this driving environment. The durability can be improved by doing the safe design of automotive bumper on the basis of the analysis result. And it is possible to be grafted onto the convergence technique at design and show the esthetic sense.

• Journal of the Korean Society of Safety
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• v.16 no.1
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• pp.79-83
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• 2001

Posture of the upper limbs in field works is known to be an important risk factor associated with CTD(Cumulative Trauma Disorders). In particular, uncomfortable posture and highly repetitive works in shipbuilding industry(for instance, sand blasting, grinding and blast painting, etc) made workers exposed to a great risk of injuries. The purpose of this paper is to analyze recruitment pattern of the muscles according to posture(joint angle displacement) during grinding. In this study, EMG signals of pectoralis major, latissimus dorsi, and posterior deltoid muscle were measured and analyzed from FlexComp EMG solution. And subjective ratings of perceived exertion were made using Borg's CR-10 rating scale.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.621-624
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• 2000

중량물을 다루는 작업들 중 허리를 이용한 들기 작업은 LBP(Low Back Pain) 및 기타 상해들을 유발한다. 실제 작업장에서 허리 상해에 대한 문제가 중요하게 부각됨에도 불구하고, 허리근육을 대상으로 피로회복의 효과에 대한 연구가 적절하게 제시되고 있지 않은 실정이다. 본 연구에서는 이같은 문제점을 해결하기 위해 Sub-maximal상태에서 유발된 근육의 피로가 초기 상태로 회복되기 위한 휴식시간을 EMG를 통하여 정량적으로 산정하였다. 그 결과, 휴식시간에 따른 피로 회복이 통계적으로 유의한 차이를 보였다. 본 결과는 허리요소작업이 들어 있는 실제작업장에서 작업의 반복에 따른 적절한 휴식시간을 정량적으로 제시하는데 필요한 기초자료를 제공함으로써 허리에 관련된 근골격계 질환을 예방하고자 하는데 이용될 수 있는 것으로 기대한다.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.181-184
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• 2002

In this research, a basis test on steel fiber concrete's material property was carried out and optimum design as well as material property was examined. In corroboration of it, the compressive strength was compared with the tensile strength and this paper tried to get the initial load of flexural cracking and the ultimate load in the positive-negative moment section through the static test of beam. The addition rate of the steel fiber, 0.75 SFRC specimen was failed at $65{\sim}75%$ of the static ultimate strength and it could be concluded that fatigue strength to two million cycle was around 75.2%.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.101-102
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• 2006

PZT thin films, which are the representative ferroelectric materials in ferroelectric random access memory (FRAM), have some serious problem such as the imprint, retention and fatigue which ferroelectric properties are degraded by repetitive polarization. BL T thin film capacitors were fabricated by plasma etching, however, the plasma etching of BLT thin film was known to be very difficult. In our previous study, the ferroelectric materials such as PZT and BLT were patterned by chemical mechanical polishing (CMP) using damascene process to top electrode/ferroelectric material/bottom electrode. It is also possible to pattern the BLT thin film capacitors by CMP, however, the CMP damage was not considered in the experiments. The properties of BLT thin films were changed by the change of polishing pressure although the removal rate was directly proportional to the polishing pressure in CMP process.