• Computers and Concrete
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• v.7 no.4
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• pp.303-315
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• 2010

In this paper, we present a new finite Timoshenko beam element with a model for ultimate load computation of reinforced concrete frames. The proposed model combines the descriptions of the diffuse plastic failure in the beam-column followed by the creation of plastic hinges due to the failure or collapse of the concrete and or the re-bars. A modified multi-scale analysis is performed in order to identify the parameters for stress-resultant-based macro model, which is used to described the behavior of the Timoshenko beam element. The micro-scale is described by using the multi-fiber elements with embedded strain discontinuities in mode 1, which would typically be triggered by bending failure mode. A special attention is paid to the influence of the axial force on the bending moment - rotation response, especially for the columns behavior computation.

• Computers and Concrete
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• v.18 no.5
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• pp.969-982
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• 2016

This paper investigates the compressive fatigue behaviour of polypropylene fibre reinforced self compacting concrete with Granite Sawing Waste (GSW). An experimental programme was conducted to obtain the fatigue lives of fibre reinforced self compacting concrete (FRSCC) at various stress levels. The stress ratio was kept constant as 0.3. Compressive fatigue test was conducted on 60 cubic specimens with 100mm edge length and 0.1% of polypropylene fibres at a frequency of 0.05Hz. The test results indicate that the fatigue lives of concretes containing granite sawing waste follow the double-parameter Weibull distribution. The fatigue strength equations have been developed based on different probabilities of failure.

• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.2
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• pp.9-16
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• 2001

In this paper, general design process for Tracked Fighting Vehicle has been suggested. Stress analysis and optimal design for ply angle of IFV's composite upper hull has been calculated using KMA CIFV and it is contained exploratory development of design process. In this point, this paper applied composite to IFV's upper hull. Finite element mesh has been made using Matlab program, and we have analyzed stress based on the given material properties and ply arrangement. For each load condition, load distribution in plane and failure index are calculated by using Tasi-Hill criterion, which is composite failure criterion and analyzing change of failure index as change of ply angle. Finally, optimal ply angles of upper hull are calculated using KMA CIFV. We can estimate the decrease of weight for IFV's upper hull.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.190-193
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• 2001

ZnO varistors have been widely used to protect power system and electronic system against overvoltages based on their excellent nonlinearity. In order to increase their protection capability, the fracture and protection technologies of arresters have to study according to their applications, namely ImA DC voltage, leakage currents, impulse residual voltages, withstanding capability to impulse surge, and energy absorption capability. ZnO varistors which have nonlinear current-voltage characteristic name a number of failure mechanism when ZnO elements absorb surge energies. Failure mode by thermal stress and Pin hole are among the most common failure mechanism at the high current surge current. In this study, the fracture mechaism of power arresters are introduced and protection technologies are researched. In particular the effect of thermal stress by surge currents to ZnO elements and methods against arc surge energy through withstand structure design of arrester are discussed.

• Journal of Applied Reliability
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• v.14 no.2
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• pp.93-96
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• 2014

RFID (Radio Frequency IDentification) system is recognition technology which can maintain various object's information. Reliability of RFID tags is the most important factor in RFID system. In this paper, we proposed ALT (Accelerated Life Test) method for UHF RFID tags. Temperature and humidity were adopted as stress factors and the accelerated life tests were conducted in three different conditions. We performed failure analysis for identifying failure mechanism and statistical analysis of test data. In the statistical analysis, we employed Inverse Power law for relationship between tag's life and stress. Through the statistical analysis, we proposed acceleration factor for several levels of temperature-humidity. The reliability qualification test plans were also designed for the tag's target reliability.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.110-113
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• 2002

As a preliminary study for the three dimensional failure analysis of composite joints, the three dimensional stress analysis on a pin-loaded unidirectional-fabric hybrid composite joints are performed. The contact and frictions between composite plate and metal bush are considered in the finite element method by NASTRAN. Experiments are conducted to validate the accuracy and feasibility of the finite element technique for 25 specimens with 5 different geometries. The finite element and experimental results show the bush cap induces the unsymmetric deformation, stress distribution, and failure behavior through the thickness. The experiment also shows the failure loads are higher in the joint with bush cap than without it.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.381-384
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• 2000

This paper proposes a method of estimating the lifetime distribution at use condition for constant stress accelerated lift tests when extrinsic failure mode as well as intrinsic one exists. A mixture of two log-normal distributions is introduced to describe these failure modes and it is assumed that a linear relation exists between the location parameter and stress. An estimation procedure using the expectation and maximization algorithm is proposed and a numerical example is given.

• Nuclear Engineering and Technology
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• v.44 no.8
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• pp.961-970
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• 2012

Often, probabilistic fracture mechanics (PFM) approaches have been adopted to quantify the failure probabilities of Ni-base alloy components, especially due to primary water stress corrosion cracking (PWSCC), in a primary piping system of pressurized water reactors. In this paper, the key features of an advanced PFM code, PINEP-PWSCC (Probabilistic INtegrity Evaluation for nuclear Piping-PWSCC) for such purpose, are described. In developing the code, we adopted most recent research results and advanced models in calculation modules such as PWSCC crack initiation and growth models, a performance-based probability of detection (POD) model for Ni-base alloy welds, and so on. To verify the code, the failure probabilities for various Alloy 182 welds locations were evaluated and compared with field experience and other PFM codes. Finally, the effects of pre-existing crack, weld repair, and POD models on failure probability were evaluated to demonstrate the applicability of PINEP-PWSCC.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.132-137
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• 2008

A failure analysis of ammonia converter which suffered hydrogen attack in two years since its initial operating time was presented. It is constructed from 2.25 Cr.1 Mo steel. Analysis showed that the failure on closing seam weld joint was due to local improper post weld heat treatment (PWHT). Improper PWHT can introduce high residual stresses in thick-walled pressure vessel. High residual stress level in weld joint is very prone to hydrogen attack for any components which are operating in hydrogen gas environment. The repair procedures based on the principle to decrease the residual stress then proposed. The repair was controlled very carefully by applying several nondestructive tests in the each stage of repair. To assure the successful of the proposed repair, after one year since repair time, high temperature ultrasonic and TOFD methods were applied on-stream to this equipment in order to evaluate its post repair condition. The two methods showed good results on the repaired area.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.132-135
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• 2009

In order study, experimental stress-strain relationships were achieved for various suctions by triaxial tests. A failure envelop was occurred on a plane in p-q-$\psi$ space, since the level of matric suction is in the small range. It was found that the failure criteria could be defined uniquely by the Bishop stress and were also independent of matric suctions. At the level of small strain, deformation moduli were evaluated according to matric suctions by fitting to Ramberg-Osgood model. It was found that deformation moduli increase as matric suctions increase.