• Journal of the KSME
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• v.36 no.9
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• pp.855-866
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• 1996

승요차 앞자축에 장착되어 회전하면서 동력을 전달하는 드라이브축은 운행중에 주로 비틀림하중을 받는다. 따라서 동 부품의 피로해석 및 설계를 위해서는 실제 운행중에 받는 서비스토크의 크기, 주파수 등에 관한 데이터가 필요하다. 차량에 탑재된 엔진의 토크와 회전수 등의 규격으로부터 드라이브축에 부가되는 최대 토크 값을 예측할 수 있으나, 자동차 운행주에는 승차인원, 도로조건, 운전자의 운전습관 등 여러가지 외적인 영향으로 인하여 서비스토크가 불규칙하게 변할 것으로 예상되므로 서비스토크를 정확히 예측하기는 어려운 실정이다. 또한, 최근의 자동차 구조부품에 대한 설계개념이 무한수명 설계에서 경량화 설계로 변화되고 있으며, 따라서 자동차 드라이브축도 실제 운용하중을 바탕으로 한 정확한 수명예측 및 강도설계가 요구되고 있다. 본 연구에서는 4륜구동형 승용차용 드라이브축에 대해 실제 운용하중에서의 피로수명을 예측하기 위해 1)텔리메트리를 이용하여 토크를 측정하고, 2) 일정진촉하중하에서의 드라이브축의 비틀림 피로시험을 수행하고, 3) 일정진폭하중하에서의 드라이브축의 비틀림 피로시험을 수행하고, 4) 축류 소재의 피로특성 데이터를 구성하여 5) 자체 개발한 프로그램으로 피로수명을 예측하고자 한다.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.19-25
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• 2013

The joining methods of steel structures of gas facilities, bridges, ships etc. by welding are composed mostly of T-type or cruciform fillet welding and full penetration or partial penetration according to the uses and the shape of the structures. In this study, it was examined the characteristics of fatigue crack according to penetration depth in relation to material thickness in the cruciform fillet welded joints. From the results, it was investigated the safe design stresses within the range of infinite life. When the LOP length is long the range of infinite life is small with root failure and when the LOP length is short the range of infinite life is large with teo failure. For the specimen of material thickness, 20mm welded by 3 pass compared with 10mm, 15mm welded by 2 pass, the fatigue strength and the range of infinite life was more improved by increasing of notch toughness from formation of micro-ferrite acicular structure.

• Journal of the KSME
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• v.55 no.2
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• pp.45-49
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• 2015

해석 및 측정 기술의 발전과 고내구성 소재 개발 등으로 인해 그동안 무한 수명으로 여겨져 왔던 천만 회의 피로수명을 넘어 운용되는 구조물들이 많아졌다. 이 글에서는 초고주기 피로현상과 이에 기초한 내구 설계의 개념 변화 및 시험법 등에 대해 소개하고자 한다.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.39-45
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• 2008

A levitation rail is placed on the top of track structure to operate Maglev vehicles and a part of track that link up with a sleeper is applied repeated load in Maglev vehicles operation. This paper aimed to verify validity of design for levitation rail, through the fatigue analysis about load which is applied to levitation rail in Maglev vehicles operation and impact load occurring in an emergency landing. Load conditions applied design load(23kN/m) in normal operation and skid drop load(24kN/m) in vehicle drop. And boundary conditions are consider bolt fixing and welding. Through static analysis, weak point and maximum stress of levitation rail could be obtained. S-N(stress-life) method was used in oder to predict fatigue life, and Goodman relationship was applied to consider a effect of mean stress. Also damage was calculated by using Miner's. As a result of fatigue analysis, levitation rail had a fatigue life which was more than requirement ($10^6$cycle) in all analysis conditions. Assumption that $10^8{\sim}10^9$cycles is infinite life, all analysis conditions had infinite life except a case under drop load and bolt fixing($1.21{\times}10^6$).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1270-1274
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• 2003

The objective of this paper is to introduce the standard of evaluation methods and fatigue test for linear motion rolling bearing. In particular, attention well be given to the list of evaluation and fatigue results in this paper. The life of a linear motion rolling bearing is given by the length of distance covered between the connection parts before the first evidence of fatigue develops in the material of one of the raceways of rolling elements. The main factors that contribute to fatigue failures include: Number of load cycles experienced; Range of stress experienced in each load cycle; Mean stress experienced in each toad cycle; Presence of local stress concentrations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.47-54
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• 2014

Endurance of ship hull can be estimated by existing regulations and fatigue estimation methods. These can be applied to the hull materials that are recommended by ship regulations but can't be applied to new materials. In this study, structural force in the worst sailing condition is obtained by the acceleration measurement test of small polyethylene boat and the endurance of small polyethylene hull is estimated by rainflow cycle counting method and linear cumulative damage rule. Maximum Von-Mises stress on the polyethylene boat is 1.8MPa and much lower than the fatigue strength of at least 5.9MPa for the fatigue life of $1{\times}10^9$ cycles. Fatigue life of the polyethylene boat hull is estimated to be 6,229 years.

• Journal of Korean Society of Steel Construction
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• v.18 no.1
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• pp.11-22
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• 2006

Message Signs (VMS) structures offer an increase in traffic safety through their ability to relay massages to motorists for warnings of hazards ahead, traffic congestion, accidents, and lane closings. The geometry of these signs sometimes results in the significant cyclic loading of the supports structure due to wind gusts, which can result from passing trucks or from natural wind. This study presents the results of analytical and experimental investigations of VMS structures. The commercially available softwareGTSTRUDL (2003) was used to perform space-frame structural analyses of these welded tubular structures. Fatigue evaluations were performed using stress ranges from field measurements and from structural analyses. Based on the results of the structural analyses that were conducted, where fatigue design loadings that had been derived from AASHTO Specifications for Structural Supports for Highway Signs, Luminaries, and Traffic Signals (2001) were used, the structures that had been studied were found not to have infinite fatigue life. According to the limited measurements that were made in this study, the fatigue design loadings derived from AASHTO Specifications (2001) appear to be conservative, but they are not overly conservative. The results of this study should be used to make a reasonable design of VMS structures, and to maintain their standards.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.17-24
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• 1998

압축기의 종류는 크게 dynamic type과 positive displacement type으로 우선 나눌 수 있다. 전자는 제트엔진에 사용되는 압축기에서 보는 바와 같이 기체의 속도를 변화시켜 동압을 정압으로 바꾸어 압력을 얻는 경우이다. 후자는 기체를 둘러싼 체적을 줄여서 압력을 얻는데 가전제품에 쓰이는 냉각용 압축기의 대부분의 종류가 이에 해당된다. 압축 기체의 종류에 따라 공기 압축기, 가스 압축기, 냉각용 압축기로도 나눌 수 있겠다. 냉각용 압축기는 다시 여러 가지 방법으로 분류할 수 있겠지만, 구동 모타의 용량이나 냉각 용량에 따라, 대형, 소형으로 분류하거나, 압축기를 둘러싼 셀의 구조에 따라 밀폐형과 반 밀폐형으로 나눌 수 있다. 밀폐형은 냉매를 반 영구적으로 보충할 필요가 없도록 용접형 셀을 가진 구조로 압축기를 다시 열어서 보수할 수가 없다. 냉장고나 냉방기 같은 가전 제품에 쓰이는 압축기는 대부분 소형 밀폐형이 되겠다. 산업용의 중,대형 압축기는 보수의 목적으로, 자동차 냉방용 압축기는 동력이 엔진축에서 공급되는 구조 상의 이유로 반 밀폐형이 채택된다. 보수가 사실상 불가능한 밀폐형의 구조 상 소형 냉장용 압축기는 거의 무한 수명을 감안한 설계를 요하게 되고, 이것이 압축기의 보수적인 설계 및 개발 성향에 어느 정도 영향을 주었다고 볼 수 있다. 이런 소형 밀폐형 압축기(positive displacement, fractional horsepower, hermetic compressor)에 관한 연구의 소개가 이 글의 주 관심이 되겠다. 압력을 얻기 위해 체적을 변화시키는 mechanism도 여러 가지가 있는 바, 왕복동식 피스톤(reciprocating piston) 압축기가 가장 오랫동안 사용되어 온 구조이다. 회전식으로 압축을 얻는 방식으로는 로타리 피스톤식, 스크류식, 스크롤식 압축기가 있다. 로타리 피스톤(rotary piston)식 압축기는 약 20여년 전 부터 냉방용 압축기에서부터 널리 쓰이게 되었다. 약 10여년전부터 상용화 된 스크롤(scroll) 형 압축기도 현재 상대적으로 용량이 큰 가정용 냉방기를 중심으로 많이 쓰이고 있다. 스크류형 압축기는 보통 중대형 상업용에 주로 쓰인다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.11
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• pp.949-954
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• 2016

When a snowplow is operating in the up or down direction, the sensor stops the movement automatically and the wire could be broken from an endless drive in the reverse direction impact or conversely winding wire. In the present study, a new bobbin was designed to ensure the durability of snowplows; in this design, the bobbin plays the role of a clutch during power transfer or idling. This will protect the blade of the snowplow during an impact and maintain close contact of the blade with the road. Therefore, the new technology to eliminate the tension and fatigue of the wire is suggested by winding a chain instead of the wire in the newly designed bobbin. From these, it was developed to extend the life of the snowplow without causing damages to the vehicle.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.5
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• pp.372-379
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• 2017

Software reliability factor during the software development process is elementary. Case of the infinite failure NHPP for identifying software failure, the occurrence rates per fault (hazard function) have the characteristic point that is constant, increases and decreases. In this paper, we propose a reliability model using the chi - square distribution which depends on the degree of freedom that represents the application efficiency of software reliability. Algorithm to estimate the parameters used to the maximum likelihood estimator and bisection method, a model selection based on the mean square error (MSE) and coefficient of determination($R^2$), for the sake of the efficient model, were employed. For the reliability model using the proposed degree of freedom of the chi - square distribution, the failure analysis using the actual failure interval data was applied. Fault data analysis is compared with the intensity function using the degree of freedom of the chi - square distribution. For the insurance about the reliability of a data, the Laplace trend test was employed. In this study, the chi-square distribution model depends on the degree of freedom, is also efficient about reliability because have the coefficient of determination is 90% or more, in the ground of the basic model, can used as a applied model. From this paper, the software development designer must be applied life distribution by the applied basic knowledge of the software to confirm failure modes which may be applied.