• Industrial Engineering and Management Systems
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• v.9 no.1
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• pp.54-59
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• 2010

A two-plan sampling system is proposed for a failure-censored life testing when the lifetime follows a Weibull distribution with known shape parameter. The proposed sampling system is based on a switching rule, for switching between the tightened and the normal inspection levels when lots are submitted for inspection in the order of production or in some other systematic way. The design parameters of the proposed sampling system are determined by the two-point approach considering the producer's risks and the consumer's at the specified acceptable reliability level and the lot tolerance reliability level, respectively. It has been observed that the proposed system requires only a single failure for the observation.

• International Journal of Reliability and Applications
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• v.3 no.4
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• pp.185-198
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• 2002

In the traditional life testing model, it is assumed that a certain number of identical items are tested under identical condition. This is due to statistical rather than practical considerations. The proportional hazards model can be used to develop a realistic approach to determine the performance of an item. That is also capable of modeling the failure rates of accelerated life testing when the covariates are applied stresses. The proportional hazards model is typically applied for a group of items to assess the importance of factors that may influence the reliability of an item. In this paper we considered the interarrival times of an item rather than the time to first failure for grouped items and provided the availability estimation for the determination of maintenance policy and overhaul time. In order to demonstrate the proposed approach, an example is presented.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.81-85
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• 2004

This paper describes the testing facility to demonstrate the performance of the distribution class circuit breakers and switchgears and the testing methods. The field-test evaluation system consists of two parts. One is the distribution system for simulation of the condition on interruption mode of switches which are installed in the system and tested by the AFG(Artificial Fault Generator) and the thunderbolt generator just like in the real field. The other is a laboratory for confirmation or the important characteristics regarding to the insulation, gas, environment durability of equipment. For the fatal failure mode, a FMEA(Failure Modes and Effects Analysis) technique which is a kind of a structural analysis to consider a counter-plan was emploved.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1945-1947
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• 2005

This study considers find out best accelerated life testing and lifetime prediction of electrolytic capacitors. We proved about relation between failure and deterioration mechanism from last thesis. Beside we performed test that temperature and voltage press higher than allowance specification. Failure distribution acquired from those test. And wiebull function and Minitab program applied to accelerated constant and lifetime by means of calculation. At the result, goodness of fit affect to weibull function and acceleration factor therefore fitting is important factor in reliability testing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.612-617
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• 2000

This paper describes the experience gained from the treatments for prevention of blade failure occurred in the low-pressure turbine. Some cracks due to high cycle fatigue were found at the blades in low-pressure turbines after long time operation. Such failure was mainly caused by the resonance of the blade with the vane passing frequency excitation. If a natural frequency of the blade exists near the excitation frequency, a resonant vibration can occur and leads to a large amount of stress which may cause fatigue failures in turbine blades. To avoid the resonance of the blade, some modifications have been performed and full-scaled mockup testing has been done to confirm the verification for modification. Test result shows that enlarging the span cover is very useful to change the natural frequency of the grouped blades effectively.

• International Journal of Reliability and Applications
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• v.2 no.2
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• pp.81-97
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• 2001

Lifetesting problems have been the subject of investigations for over three decades. Most suggested approaches are markedly different from those used in the related but wider goodness of fit problems. In the current investigation, it is demonstrated that a goodness of fit approach is possible in many lifetesting problems and that It results in simpler procedures that are asymptotically equivalent or better than standard ones. They may also have superior finite sample behavior. Several perennial classes are addressed here. The class of increasing failure rate (IFR) and the class of new better than used (NBU) are addressed first. In addition, we provide testing for a newer and practical class of new better than used in convex ordering (NBUC) due to Cao and Wang (1991). Other classes can be developed similarly and this point is illustrated with the classes of new better than used in expectation (NBUE) and harmonic new better than used in expectation (HNBUE).

• Steel and Composite Structures
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• v.50 no.5
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• pp.531-548
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• 2024

This paper presents an experimental investigation into the progressive collapse behavior of composite steel-concrete frames under various column removal scenarios. This study involves testing two two-bay, two-story composite frames featuring CFST columns and profiled steel decking composite slabs. Two removal scenarios, involving the corner column and middle column, are examined. The paper reports on the overall and local failure modes, vertical force-deformation responses, and strain development observed during testing. Findings indicate that structural failure initiates due to fracture and local buckling of the steel beam. Moreover, the collapse resistance and ductility of the middle column removal scenario surpass those of the corner column removal scenario. Subsequent numerical analysis reveals the significant contribution of the composite slab to collapse resistance and capacity. Additionally, it is found that horizontal boundary conditions notably influence the collapse resistance in the middle column removal scenario only. Finally, the paper proposes a simplified calculation method for collapse resistance, which yields satisfactory predictions.

• Geomechanics and Engineering
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• v.38 no.2
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• pp.157-164
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• 2024

This paper describes the general trends of the stress-strain behavior of Korean weathered soil prior to failure and behavior at failure under triaxial loading. The isotropically consolidated samples were tested in a testing device under monotonic undrained loading. Relative density, effective mean pressure and fine content were the factors varied in the experimental investigation. The test results were analyzed and their behaviors were interpreted within the framework of plasticity constitutive model for a weathered Korean silty sand. Possible physical bases for the proposed forms are discussed. Validation of the applied model using the laboratory results is also given.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.181-186
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• 2003

There are many uncertainties in structural failures or structures, so probabilistic failure cause assessment should be performed in order to consider the uncertainties. However, in many cases of forensic engineering, the failure cause assessments are performed by deterministic approach though number of uncertainties are existed in the failures or structures. Thus, deterministic approach may have possibility for leading to unreasonable and unrealistic failure cause assessment due to ignorance of the uncertainties. Therefore, probabilistic approach is needed to complement the shortcoming of deterministic approach and to perform the more reasonable and realistic failure cause assessment. In this study, reliability-based failure cause assessment (reliability based forensic engineering) is performed, which can incorporate uncertainties in failures and structures. For more practical application, the modified ETA technique is proposed, which automatically generates the defected structural model, performs structural analysis and reliability analysis, and calculates the failure probabilities of the failure events and the occurrence probabilities of the failure scenarios. Also, for more precise reliability analysis, uncertainties are estimated more reasonably by using bayesian approach based on the experimental laboratory testing data in forensic report.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.1 s.244
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• pp.8-17
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• 2006

When subjected to severe shear deformation by ECAP, microstructure of Al2024 becomes extremely refined. To measure the strength of that, small punch(SP) testing method was adopted as a substitute for the conventional uniaxial tensile testing because the size of material processed by ECAP were limited to ${\psi}12\;mm$ in transverse direction. SP tests were performed with specimens in longitudinal and transverse directions of Al2024 ECAP metal. For comparing the strength values with those assessed by SP tests, uniaxial tensile tests were also conducted with specimens in longitudinal direction. Failure surfaces of the tested SP specimens showed that failure mode was shear deformation and Al 2024 ECAP metal has an anisotropy in strength. Thus, conventional equations proposed for assessing the strength characteristics were improper to assess those of Al2024 ECAP metal. In this paper a way of assessing the strength of Al 2024 ECAP metal was proposed and was proven to be effective.