• Title/Summary/Keyword: Testing time

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Testing unknown age classes of life distributions based on TTT-transform

  • El-Din, M.M. Mohie;Abu-Youssef, S.E.;Ali, Nahed S.A.
    • International Journal of Reliability and Applications
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    • v.14 no.1
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    • pp.1-9
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    • 2013
  • A nonparametric procedure for testing exponentially against used better than aged in expectation (UBAE) class of life distributions is presented. We construct a test statistics based on scaled total time on test (TTT)-transformation, to test exponentiality against UBAE class of life distributions. The distribution of the statistic is investigated via simulation. Practical applications of the proposed test are presented.

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Testing of EBELC classes of life distributions based on TTT-transform

  • Abu-Youssef, S.E.;Mohie El-Din, M.M.;Hassan, M.Kh.
    • International Journal of Reliability and Applications
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    • v.13 no.1
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    • pp.49-56
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    • 2012
  • Using total time on test transform (TTT), a new approach is taken for testing exponentiality versus the unknown age, exponential better than equilibrium life in convex ordering (EBELC). Selected critical values are tabulated for sample size n =2(2)50 and powers of the test are estimated for some commonly used distributions in reliability. Finally real example is presented to illustrate the theoretical results.

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Ultrasonic Detection of Small Crack in Studs[Bolts] by Time Difference of Thread Signals(TDTS) (초음파진행 시간차에 의한 STUD[BOLT] 나사산의 미세한 결함검출)

  • Suh, D.M.;Park, D.Y.;Kim, C.K.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.10 no.1
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    • pp.38-46
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    • 1990
  • It is difficult to detect such flaws as stress - corrosion cracking or corrosion wastage(loss of bolt diameter) in the threads. In many cases the critical size of a flaw is very small(1-2 mm order). This paper describes how it is possible to discriminate small flaw indications in threads using the time difference or thread signals(TDTS) by a signal-conditioning technique.

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A Study on the Flaw Evaluation in the Straddle Mount Type Low Pressure Turbine Disc Using Phased Array Ultrasonic Technique (위상 배열 초음파 기법을 이용한 Straddle Mount형 저압 터빈 디스크 결함 평가에 관한 연구)

  • Yang, Seung-Han;Yoon, Byung-Sik;Kim, Yong-Sik
    • Journal of the Korean Society for Nondestructive Testing
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    • v.26 no.4
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    • pp.231-238
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    • 2006
  • Nondestructive examination for low pressure turbine disc in standard nuclear power plant using phased array technique was studied. For this purpose, disc mockups were made and notches were machined in the mockups. Detection and length sizing by different methods are compared. Depth of deep notches could be measured by using AATT(absolute arrival time technique) or RATT(relative arrival time technique) but shallow notches that must be detected in early stage couldn't be measured by these two methods. For this case, notch depth was estimated by using signal response angle range and preyed usefulness.

The Dynamics of Noise and Vibration Engineering Vibrant as ever, for years to come

  • Leuridan, Jan
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2010.05a
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    • pp.47-47
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    • 2010
  • Over the past 20 years, constant progress in noise and vibration (NVH) engineering has enabled to constantly advance quality and comfort of operation and use of really any products - from automobiles to aircraft, to all kinds of industrial vehicles and machines - to the extend that for many products, supreme NVH performance has becomes part of its brand image in the market. At the same time, the product innovation agenda in the automotive, aircraft and really many other industries, has been extended very much in recent years by meeting ever more strict environmental regulations. Like in the automotive industry, the drive towards meeting emission and CO2 targets leads to very much accelerated adoption of new powertrain concepts (downsizing of ICE, hybrid-electrical...), and to new vehicle architectures and the application of new materials to reduce weight, which bring new challenges for not only maintaining but further improving NVH performance. This drives for innovation in NVH engineering, so as to succeed in meeting a product brand performance for NVH, while as the same time satisfying eco-constraints. Product innovation has also become increasingly dependent on the adoption of electronics and software, which drives for new solutions for NVH engineering that can be applied for NVH performance optimization of mechatronic products. Finally, relentless pressure to shorten time to market while maintaining overall product quality and reliability, mandates that the practice and solutions for NVH engineering can be optimally applied in all phases of product development. The presentation will first review the afore trends for product and process innovation, and discuss the challenges they represent for NVH engineering. Next, the presentation discusses new solutions for NVH engineering of products, so as to meet target brand values, while at the same time meeting ever more strict eco constraints, and this within a context of increasing adoption of electronics and controls to drive product innovation. NVH being very much defined by system level performance, these solutions implement the approach of "Model Based System Engineering" to increase the impact of system level analysis for NVH in all phases of product development: - At the Concept Phase, to be able to do business case analysis of new product concepts; to arrive at an optimized and robust product architecture (e.g. to hybrid powertrain lay-out, to optimize fuel economy); to enable target cascading, to subsystem and component level. - In Development Phase, to increase realism and productivity of simulation, so as to frontload virtual validation of components and subsystems and to further reduce reliance on physical testing. - During the final System Testing Phase, to enable subsystem testing by a combination of physical testing and simulation: using simulation models to simulate the final integration context when testing a subsystem, enabling to frontload subsystem testing before final system integration is possible. - To interconnect Mechanical, Electronical and Controls engineering, in all phases of development, by supporting model driven controls engineering (MIL, SIL, HIL). Finally, the presentation reviews examples of how LMS is implementing such new applications for NVH engineering with lead customers in Europe, Asia and US, with demonstrated benefits both in terms of shortening development cycles, and/or enabling a simulation based approach to reduce reliance on physical testing.

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Study on Leak Detection of the Pipeline System by Acoustic Emission (음향방출(音響放出)에 의한 배관계(配管系)의 누출방지(漏出防止)에 관한 연구(硏究))

  • Yoon, D.J.;Kim, C.J.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.7 no.1
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    • pp.7-17
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    • 1987
  • Leak detection testing for the pipeline system was performed by the acoustic emission method. It was found that the detected signal spectrum was influenced by the frequency response of sensors and pressure changes. AE parameters and frequency spectrum distributions were used to analyze the leak signals. The slope rise time of AE parameters were the important factors for distinguishing leak signals. The amplitude of leak signal was more affected by the changes of leak, rate and pressure than those of leak type.

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A Multiobjective Dynamic Programming Model for Sequenetial Testing Strategy Selection (축차검사전략의 선정을 위한 다목적. 동적계획 모형)

  • 최병돈
    • Journal of the Korean Operations Research and Management Science Society
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    • v.18 no.1
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    • pp.55-69
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    • 1993
  • The tests in a battery can be performed in different sequences, and different sequential testing strategies will have exactly the same overall performances for that battery, but at different expected total costs and expected time consumptions. By using a multiobjective dynamic programming model, we are able to find all noninferior testing strategies for a given battery of tests and a stopping rule.

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LIQUID PENETRANT TESTING AT LOW TEMPERATURE (저온에서 행하는 액체침투 탐상방법)

  • Barbier, R.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.3 no.1
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    • pp.26-30
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    • 1983
  • Tests on Liquid Penetrant products normally utilized in the temperature range $10^{\circ}C\;to\;40^{\circ}C$ have shown that the required sensibility can not be obtained at temperatures lower than $10^{\circ}C$ with the penetration and development time usually specified in the operating procedures. It is thus confirmed that $10^{\circ}C$ is the lowest allowable temperature for use of these products. The results obtained with a penetrant and develope. specially formulated for low temperatures (SHERWIN B 305+D100) are satisfactory between $0^{\circ}C\;and\;15^{\circ}C$.

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Application of Accelerated Degradation Testing for VFD (Vacuum Fluorescent Display) (VFD(Vacuum Fluorescent Display) 가속열화시험 응용사례)

  • Bae, Suk-Joo
    • Journal of Applied Reliability
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    • v.5 no.4
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    • pp.413-425
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    • 2005
  • As an alternative to traditional life testing, degradation tests can be effective in assessing product reliability when measurements of degradation leading to failure can be observed. This article presents an accelerated degradation testing for vacuum fluorescent displays (VFDs). The accelerated degradation model is based on Arrhenius-lifetime relationship for cathode temperatures. We compare the results between accelerated degradation test and test at normal use condition. Accelerated degradation test for display devices is observed as an efficient method to warrantee product reliability to customers, as well as a tool to save time and costs.

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Development of Viscous Cabin Mount for Excavator (액체봉입형 Viscous 굴삭기 Cabin Mount 개발)

  • 김원영;전범석;박외경;강하근
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.10a
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    • pp.339-344
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    • 1997
  • Samsung Ltd. has developed a new-type cab mount for specific use on construct ion machinery subjected to strong vibration and multi-directional impact force. These all make it possible to achieve an excellent damping effect over a wide frequency range against large amplitude vibration as well as excellent insulation against small-amplitude vibration. This new mount make lower vibration and noise levels while increasing riding comfort at the same time. Characteristics of Cab mount were optimized through computer simulation, advanced bench testing, ODS testing, and a real equipment offroad testing.

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