• Composites Research
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• v.18 no.1
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• pp.1-9
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• 2005

A methodology is presented for the failure prediction of composite single-lap bonded joints considering both of composite adherend failure and bondline failure. An elastic-perfectly plastic model of adhesive and a delamination failure criterion are used in the methodology. The failure predictions have been performed using finite element method and the proposed methodology. The failure prediction results such as failure mode and strength have very good agreements with the test results of joint specimens with various bonding methods and parameters. The influence of variations in the effective strength (that is, adhesion performance) and plastic behavior of adhesive on the failure characteristics of composite bonded Joints are investigated numerically. The numerical results show that optimal joint strength is archived when adhesive and delamination failure occur in the same time.

• Nuclear Engineering and Technology
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• v.19 no.4
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• pp.233-241
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• 1987

Difficulties are encountered when the behavior of complex systems (i.e., fuel failure probability) that have unreliable deterministic models is predicted. For more realistic prediction of the behavior of complex systems with limited observational data, the present study was undertaken to devise an approach of combining predictions from the deterministic model and actual observational data. Predictions by this method of combining are inferred to be of higher reliability than separate predictions made by either model taken independently. A systematic method of hierarchical pattern discovery based on the method developed in the SPEAR was used for systematic search of weighting factors and pattern boundaries for the present method. A sample calculation was performed for prediction of CANDU fuel failures that had occurred due to power ramp during refuelling process. It was demonstrated by this sample calculation that there exists a region of feature space in which fuel failure probability from the PROFIT model nearly agree with that from observational data.

• Journal of Korea Water Resources Association
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• v.42 no.6
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• pp.457-464
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• 2009

This paper proposes methodologies for analyzing the accuracy of the proportional hazards model in predicting consecutive break times of water mains and estimating the time interval for economical water main replacement. By using the survival functions that are based on the proportional hazards models a criterion for the prediction of the consecutive pipe breaks is determined so that the prediction errors are minimized. The criterion to predict pipe break times are determined as the survival probability of 0.70 and only the models for the third through the seventh break are analyzed to be reliable for predicting break times for the case study pipes. Subsequently, the criterion and the estimated lower and upper bound survival functions of consecutive breaks are used in predicting the lower and upper bounds of the 95% confidence interval of future break times of an example water main. Two General Pipe Break Prediction Models(GPBMs) are estimated for an example pipe using the two series of recorded and predicted lower and upper bound break times. The threshold break rate is coupled with the two GPBMs and solved for time to obtain the economical replacement time interval.

• Composites Research
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• v.21 no.4
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• pp.22-28
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• 2008

The composite joint has become an important research area because the structural efficiency of a structure with a joint is determined by its joints rather than by its basic structure since the joints are often the weakest areas in composite structures. In this paper, the strengths of adhesive joints consisting of metal and composites were predicted and tested by the maximum strain theory and damage zone theory. Nonlinear finite element analyses of adhesive Joints considering the material nonlinearity of the adhesive layer were performed. From the tests and analyses, the strengths of the adhesive joints could be predicted to within 22.2% using the damage zone ratio.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.936-938
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• 2017

In this paper, the progressive failure analysis of a bolted composite joint which is used in combustion tubes of projectiles and weapon systems is performed. Hashin's failure criterion is considered as fiber tensile failure mode, fiber compressive failure mode, matrix tensile failure mode, and matrix compressive failure mode for this analysis. And this criterion is used to make user subroutine, UMAT. Through the progressive failure analysis we predicted failure strength and compared failure strength with specimen test result.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.506-513
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• 1992

본 연구에서는 복합재 구조물에 대하여 유한요소해석법에 현상학적 모델인 전 단지연해석을 도입하여 강성저하와 모재파손을 예측하고 변형률을 매개변수로 한 Wei- bull 함수를 섬유파손해석에 도입하여 초기파손후의 거동을 묘사하고자 한다. 그리 고 면내전단하중이 작용하는 경우에 대해 전단지연해석을 수행할 수 있도록 모델링을 확장했다. 모재균열의 존재로 인한 단층의 강성변화는 실험으로 측정이 불가능하므 로 유한요소해석을 수행하여 비교하였다. 이 모델로부터 전단강성의 저하를 평가하 는 방법을 사용하였으며, 모재파손의 밀도 예측도 평균변형률 개념으로 전단효과를 고 려할 수 있도록 수정하였다. 그리고 초기파손후의 거동을 점진적으로 해석하기 위해 비선형 유한요소프그램을 작성하고, 상기의 모델을 도입하여 초기파손후의 거동을 보 다 정확히 묘사할 수 있는 방법을 제시하고 예로서 평시편에 대해 해석하고 실험치 및 타방법의 결과와 비교하였다.

• Plant Journal
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• v.15 no.2
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• pp.56-61
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• 2019

In this study, the failure analysis of the internal tube occurred in the high pressure feedwater heater for power generation boiler of 500 MW supercritical pressure coal fired power plant was investigated. I suggested a prediction model that can diagnose internal tube failure by changing the position of level control valve on the shell side and the suction flow rate of the boiler feedwater pump. The suggested prediction model is demonstrated through additional cases of feedwater system unbalance. The simultaneous comparison of the shell side level control valve position and the suction flow rate of the boiler feedwater pump compared to the normal operating state value, even in the case of the high pressure feedwater heater for the power boiler, It can be a powerful prediction diagnosis.

• Composites Research
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• v.13 no.1
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• pp.33-39
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• 2000

A numerical approach for predicting the ultimate strength of laminate composites has been studied using the Weibull distribution of the strengths of lamina plies. The probabilistic initial failure strengths of laminates were calculated using Tsai-Hill failure criterion. The ultimate strength of the laminate composites has been predicted using progressive failure analysis. The experimental results show that the strength prediction based on the Weibull distribution of ply strength reasonably agrees well with the experimentals better than equal strength assumption.

• International Journal of Highway Engineering
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• v.4 no.2 s.12
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• pp.9-18
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• 2002

The main distresses that influence pavement performance are rutting, fatigue cracking, and longitudinal roughness. Thus, it is important to analyze the factors that affect these three distresses, and to develop prediction models. In this paper, three distress prediction models were developed using DataPave program which stores data from a wide variety of pavement sections In the United States. Also, sensitivity studies were conducted to evaluate how the input variables impact on the distresses. The result of sensitivity study for the prediction model of rutting showed that asphalt content, air void, and optimum moisture content of subgrade were the major factors that affect rutting. The output of sensitivity study for the prediction model of fatigue cracking revealed that asphalt consistency, asphalt content, and air void were the most influential variables. The prediction model of longitudinal roughness indicated asphalt consistency, #200 passing percent of subgrade aggregate, and asphalt content were the factors that affect longitudinal roughness.

• Applied Biological Chemistry
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• v.38 no.4
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• pp.325-329
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• 1995

Changes in the physical properties of soybean curd upon the processing conditions such as coagulant concentration, heating temperature and molding pressure were determined by using a failure stress and residual delay time of ultrasonic wave(5 MHz). Maximum failure stress of Tofu was obtained at the 0.3% $CaCl_2$ coagulant concentration, $95^{\circ}C$ heating temperature and greater molding pressure, respectively, whereas the delay time is inverse proportion to the failure stress value. The results of the multiple regression analysis with factorial design showed that the model equation consisted with delay time and processing conditions gave the good prediction of the Tofu failure stress.