• Computers and Concrete
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• 제20권1호
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• pp.99-110
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• 2017

Service life assessments which do not include the synergy between mechanical and environmental loading are neglecting a factor that can have a significant impact on structural safety and durability assessment. The degradation of concrete structure is a result of the combined effect of environmental and mechanical factors. In order to make service life design realistic it is necessary to consider both of these factors acting simultaneously. This paper deals with the advanced modelling of concrete carbonation and chloride ingress into concrete using stochastic 1D and 2D models. Widely accepted models incorporated into the new fib Model Code 2010 are extended to include factors that reflect the coupled effects of mechanical and environmental loads on the durability and reliability of reinforced concrete structures. An example of cooling tower degradation by carbonation and an example of a bended reinforced concrete beam kept for several years in salt fog are numerically studied to show the capability of the stochastic approach. The modelled degradation measures are compared with experimental results, leading to good agreement.

• 대한기계학회논문집A
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• 제25권5호
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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.

• 한국염색가공학회지
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• 제29권3호
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• pp.155-161
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• 2017

In CPB(Cold-Pad-Batch) dyeing, the rubber of the padder roll is influenced by the heat, chemical and mechanical influences and thus aging of the padder roll rubber occurs. This study presents an accelerated thermal aging test of the CPB padder roll rubber with strong alkali conditions. Using Arrhenius formula of the various property values for the various aging temperatures($80^{\circ}C$, $90^{\circ}C$, $100^{\circ}C$) of the padder roll, the accelerated life predictions could be calculated. The threshold value of the property was set at different values. The hardness was set at the point where 5% degradation occurs based on the actual use conditions, and the tensile strength was set at the point where 50% degradation occurs based on the general life prediction standards. From the results of the different physical properties at differing temperatures, the Arrhenius plot could be obtained. Through the usage of the Arrhenius Equation, significant duration expectation could be predicted, and the chemical aging behavior of the CPB padder roll could be found at the arbitrary and actual temperatures.

• 산업공학
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• 제12권3호
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• pp.448-457
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• 1999

Accelerated degradation is concerned with models and data analyses for degradation of product performance over time at overstress and design conditions. Although there have been numerous studies with accelerated degradation theory in reliability, very few actually apply to parametric statistical analyses. This paper shows how to analyze degradation data, provides tests for how well the assumptions hold. Reel sensors, a sort of photointerrupters in home VCR, hive been tested, and least-square analyses are used to illustrate our approach. Tests for linearity of the performance-time relationship, dependence of the lognormal distribution, and the standard deviation on time are performed. The mean life of tested sensors is assessed at about 414,000 hours, and the Arrhenius activation energy of this reaction is concluded to be 0.39 eV as results.

• 한국안전학회지
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• 제25권1호
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• pp.22-26
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• 2010

Material degradation should be considered to assess integrity and residual life of high temperature equipments. However, the property data reflecting degradation are not sufficient for practical use. In this study, mechanical properties of 1Cr-1Mo-0.25V casting steel generally used for turbine casing were measured and variation of microstructure was observed. Degradation was simulated by isothermal heat treatment.

• 한국전기전자재료학회논문지
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• 제17권12호
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• pp.1289-1295
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• 2004

In this paper, degradation in field-aged PV modules including degradation of interconnect, discoloration of encapsulant and hot spot have been observed and analyzed. From the results, photovoltaic module installed for 6 years shows around 16 % drop of electrical properties due to the interconnect degradation and PV module passed 18 years has been found to drop of around 20 % mainly by the encapsulant discoloration. Furthermore the difference between low and high temperature of PV array at hot spot goes up to 3$0^{\circ}C$ and it leads to interconnect degradation. On the other hands, the temperature difference was observed to be around 15$^{\circ}C$ at the encapsulant discoloration spot of PV array.

• 한국세라믹학회지
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• 제49권1호
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• pp.48-55
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• 2012

Degradation of performance and life time of a functional material or device thereof is induced, to a great extent, by mass transfer in the material that is driven by various thermodynamic forces imposed intentionally or accidentally during its operation or service. The forces are any gradient of intensive thermodynamic variables, component chemical potentials, electrical potential, temperature, stresses, and the like. This paper reviews electric-field induced degradation phenomena in ionic solid compounds including insulation resistance degradation, crystal shift, microstructural alterations, compositional unmixing, and compound decomposition. Their inner workings are also discussed qualitatively.

• 한국안전학회지
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• 제15권4호
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• pp.8-14
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• 2000

The remaining life estimation for the aged components in power plants as well as chemical plants are very important because mechanical properties of the components are degraded with time of service exposure in the high temperature. Since it is difficult to take specimens from the operating components to evaluate mechanical properties of components, accelerated aging technique are needed to estimate and analyse the material degradation. In the this study, test materials with 4 different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C$. And tensile test, $k_{IC}$ test, hardness test and Scanning Electron Microscope analysis were performed in order to evaluate the degradation of 1Cr-1Mo-0.25V steels.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.28-32
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• 2004

In this paper, degradation in field-aged PV modules including degradation of interconnect, discoloration of encapsulant and hot spot have been observed and analyzed. From the results, photovoltaic module installed for 6 years shows around 16% drop of electrical properties due to the interconnect degradation and PV module passed 18 years has been found to drop of around 20% mainly by the encapsulant discoloration. Furthermore the difference between low and high temperature of PV array at hot spot goes up to $30^{\circ}C$ and it leads to interconnect degradation. On the other hands, the temperature difference was observed to be around $15^{\circ}C$ at the encapsulant discoloration spot of PV array.

• 생명과학회지
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• 제23권12호
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• pp.1420-1427
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• 2013

이전에 새로운 아세틸알긴산 아세틸분해효소(acetylalginate esterase, AcAlgE)를 Sphingomonas sp. MJ-3 균주로부터 클로닝하고 특성을 보고한 바 있다. 본 연구에서는 Pseudomonas aeruginosa로부터 얻은 아세틸알긴산을 분해하는데 미치는 MJ-3 AcAlgE와 KS-408 알긴산 분해효소의 상승효과를 고-자기장 $^1H$-NMR과 peptide column을 장착한 FPLC를 이용하여 조사하였다. 알긴산 분해효소 coupled assay 법으로 측정한 결과 AcAlgE 효소는 산가수 분해하여 얻은 저분자 아세틸알긴산을 분해하는 것보다 고분자 아세틸알긴산을 분해하는 경우 낮은 활성을 보였다. 아세틸알긴산을 알긴산 분해효소로 분해하는 경우 먼저 AcAlgE로 아세틸알긴산의 아세틸기를 분해하여 제거한 후에야 KS-408 알긴산 분해효소의 활성이 높은 것으로 나타났다. 이러한 결과는 재조합 AcAlgE는 알긴산 분해효소에 의한 아세틸알긴산의 분해효과를 상승시킨다는 사실을 보여준다.