• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.3
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• pp.368-375
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• 2012

Durability performance evaluation of automotive components is very important and time consuming task. In this paper, to reduce vehicle component development time and cost virtual testing simulation technology is used to evaluate durability performance of a passenger car front aluminum sub-frame. Multibody dynamics based vehicle model and virtual test simulation model of a half car road simulator are validated by comparisons between rig test results and simulation results. Durability life prediction of the sub-frame is carried out using the model with road load data of proving ground which can evaluate accelerated durability life. We found that the durability performance of the sub-frame is sufficient and it can be predicted within short time compared to rig test time.

• Journal of The Korean Society of Grassland and Forage Science
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• v.37 no.1
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• pp.80-91
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• 2017

The objective of this study was to select a model showing high-levels of interpretability which is high in R-squared value in terms of predicting the yield in the mixed pasture using the factors of fertilization, seeding rate and years after pasture establishment in steps, as well as the climate as a basic factor. The processes of constructing the yield prediction model for the mixed pasture were performed in the sequence of data collection (forage and climatic data), preparation, analysis, and model construction. Through this process, six models were constructed after considering climatic variables, fertilization management, seeding rates, and periods after pasture establishment years in steps, thereafter the optimum model was selected through considering the coincidence of the models to the forage production theories. As a result, Model VI (R squared = 53.8%) including climatic variables, fertilization amount, seeding rates, and periods after pasture establishment was considered as the optimum yield prediction model for mixed pastures in South Korea. The interpretability of independent variables in the model were decreased in the sequence of climatic variables(24.5%), fertilization amount(17.8%), seeding rates(10.7%), and periods after pasture establishment(0.8%). However, it is necessary to investigate the reasons of positive correlation between dry matter yield and days of summer depression (DSD) by considering cultivated locations and using other cumulative temperature related variables instead of DSD. Meanwhile the another research about the optimum levels of fertilization amounts and seeding rates is required using the quadratic term due to the certain value-centered distribution of these two variables.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.5
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• pp.874-882
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• 2001

The static and fatigue tests have been carried out to verify the validity of a generalized residual strength degradation model. And a new method of parameter determination in the model is verified experimentally to account for the effect of tension-compression fatigue loading of spheroidal graphite cast iron. It is shown that the correlation between the experimental results and the theoretical prediction on the statistical distribution of fatigue life by using the proposed method is very reasonable. Furthermore, it is found that the correlation between the theoretical prediction and the experimental results of fatigue life in case of tension-tension fatigue data in composite material appears to be reasonable. Therefore, the proposed method is more adjustable in the determination of the parameter than maximum likelihood method and minimization technique.

• Proceedings of the Korean Reliability Society Conference
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• 2000.04a
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• pp.213-222
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• 2000

In present study, a stochastic model is developed for the low cycle fatigue life prediction and reliability assessment of 316L stainless steel under variable multiaxial loading. In the proposed model, fatigue phenomenon is considered as a Markov process, and damage vector and reliability are defined on every plane. Any low cycle fatigue damage evaluating method can be included in the proposed model. The model enables calculation of statistical reliability and crack initiation direction under variable multiaxial loading, which are generally not available. In present study, a critical plane method proposed by Kandil et al., maximum tensile strain range, and von Mises equivalent strain range are used to calculate fatigue damage. When the critical plane method is chosen, the effect of multiple critical planes is also included in the proposed model. Maximum tensile strain and von Mises strain methods are used for the demonstration of the generality of the proposed model. The material properties and the stochastic model parameters are obtained from uniaxial tests only. The stochastic model made of the parameters obtained from the uniaxial tests is applied to the life prediction and reliability assessment of 316L stainless steel under variable multiaxial loading. The predicted results show good accordance with experimental results.

• Journal of the Korea Safety Management & Science
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• v.17 no.2
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• pp.241-247
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• 2015

The purpose of the warranty data analysis can be classified into two categories. Two goals is a failure cause analysis and life prediction analysis. In this paper first, we applied multivariate analysis method that can be estimated in consideration of various factors on the failure cause warranty data. In particular, we apply the Tree model and Cox model. The advantage of the Tree is easy to interpret this result as compared to other models. In addition Cox model can quantitatively express the risk. Second, this paper proposed a multivariate life prediction model (AFT) considering a variety of factors. By applying the actual warranty data confirmed the usability.

• Journal of Information Technology Services
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• v.17 no.1
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• pp.91-103
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• 2018

This study developed a prediction model using machine learning technology and predicted the success of health consulting by using life log data generated through u-Health service. The model index of the Random Forest model was the highest using. As a result of analyzing the Random Forest model, blood pressure was the most influential factor in the success or failure of metabolic syndrome in the subjects of u-Health service, followed by triglycerides, body weight, blood sugar, high cholesterol, and medication appear. muscular, basal metabolic rate and high-density lipoprotein cholesterol were increased; waist circumference, Blood sugar and triglyceride were decreased. Further, biometrics and health behavior improved. After nine months of u-health services, the number of subjects with four or more factors for metabolic syndrome decreased by 28.6%; 3.7% of regular drinkers stopped drinking; 23.2% of subjects who rarely exercised began to exercise twice a week or more; and 20.0% of smokers stopped smoking. If the predictive model developed in this study is linked with CBR, it can be used as case study data of CBR with high probability of success in the prediction model to improve the compliance of the subject and to improve the qualitative effect of counseling for the improvement of the metabolic syndrome.

• Journal of Applied Reliability
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• v.7 no.4
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• pp.163-172
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• 2007

Phenomenon, such as hardening, cracking or breaking etc.. of PVC tape for wiring harness by aging were detected on driven automobile in field. Hardening or cracking of PVC tape were confirmed decline of elongation by surrounding stress. The accelerated heat aging test was carried out applying temperature most important factor of aging, and then deduced an equation of useful life using arrhenius model. Prediction method of useful life of PVC tape was developed using miner rule calculating damage value by thermal energy classified temperature by matching deduced equation of useful life and measured temperature value on driven automobile in field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.3
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• pp.832-842
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• 1996

Fatigue life prediction and fatigue behavior of circular notched carbon fiber reinforced plastic laminates are presented. Point and average stress criteria by Whitney and Nuismer are generalized to fatigue fracture criteria for notched laminates. Residual strength degradation model and the assumptions on the stress redistribution are introduced during the derivation of prediction equations. S-N curve, Basquin's relation, and H and H's FLPE1 are chosen for evaluation of residual strength of unnotched laminates and six prediction equations are derived. Experiments are performed using Graphite/Epoxy laminates whose fiber orientation is $[0$^\circ$/+45$^\circ$/-45$^\circ$/90$^\circ$]s. Presented prediction equations are reasonably close to experimental data and proposed appoach is found to be suitable to predict fatigue life of notched composite laminates.

• The Journal of Korean Academic Society of Nursing Education
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• v.18 no.2
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• pp.312-322
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• 2012

Objectives: The purpose of this study was to investigate the factors related to adjustment of college for nursing students and to develop a collective model for successful prediction and concrete paths of the factors. Methods: Data collection was conducted from May 19th 2010 to Jun 4th 2010. Five hundred thirty-one questionnaires were used for data analysis after distributing 560 sheets to senior students in 8 different locations. Data was analyzed with SPSS 18.0 Win program and AMOS 18.0. Results: Mother attachment does not have a direct effect on adjustment to college life but does effect psychological well-being and coping, which indirect adjustment to college life. In addition, the more psychological well-being and coping usage frequency, and the less stress of clinical practice, the higher score of adjustment to college life. According to the results, explanatory power of the model for the college nursing students' adjustment was 62.0%. Conclusions: To improve adjustment to college life, it is recommended to have a direct method of developing psychological well-being and coping improvement program to improve mother attachment. The research is meaningful in a sense that it explains the cause and effect relationship between adjustment to college life and relevant variables to predict comprehensive dimensional explanation of adjustment of college life for nursing students.

• Journal of Applied Reliability
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• v.9 no.2
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• pp.71-80
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• 2009

This paper discusses the service life prediction methods for CFRP bar for concrete reinforcement using accelerated degradation tests. The relationship between performance degradation and the rate of a failure-causing chemical reaction is assumed for the temperature accelerated degradation tests. Methods of obtaining acceleration factors and predicting service life of the CFRP bar using the degradation model are presented.