• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.6
• /
• pp.1087-1094
• /
• 2010

We have developed a cylindrical multi-terminal capacitive-conductive sensor that could be attached to the internal surface of cooling system pipe to evaluate capacitance and conductivity of heat transfer fluid. It was used as measuring system to diagnose insulating condition, by which was kept a insulating resistance of inner stack and at the same time was cooled electrochemical heat of reaction of FCEV(fuel cell electric vehicle) stack that used a compressed hydrogen gas reacting with oxygen in accordance with variation on thermal degradation of nonconductive heat transfer fluid. Also to assess diagnosis characteristics of heat transfer fluid, i.e. coolant, we have performed accelerated aging test using developed sensor attached to cooling system. Consequently, it was measured dielectric and electric resistance of coolant to estimate and analyse for dielectric properties by degradation condition.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.3
• /
• pp.855-864
• /
• 2013

The dynamic characteristics of natural rubber bearings, which are used as isolator, are dependent on the main rubber's dynamic behaviors and nonlinear properties. Rubber materials tend to undergo an aging process under the influence of mechanical or environmental factors, so they inevitably end up facing damage. A main cause of aging like this is known to be oxidization, which occurs through the heat of reaction at high temperatures. Accordingly, in this study an accelerated thermal aging test was carried out in order to compare the characteristic values of the bearings before and after thermal aging occurs. As a result of this experiment, it was found that a thermal aging phenomenon could have some effects on shear stiffness, energy absorption, and equivalent damping coefficients of the bearings. Furthermore, a deterioration in the dynamic properties of the natural rubber bearings caused by the thermal aging was applied to an actual bridge and then the effects of such thermal aging on the seismic performance of the bridge were also compared and analyzed based on numerical analysis. As a result of this analysis, it was found that the changes in the basic properties of the natural rubber bearings caused by the thermal aging bring only a minor effect on the seismic performance of bridges.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.2A
• /
• pp.109-116
• /
• 2012

The dynamic properties of lead rubber bearings, which are used as isolator, are dependent on the main rubber's dynamic behaviors and nonlinear qualities. Rubber materials tend to undergo an aging process under the influence of mechanical or environmental factors, so they can end up inevitably facing damage. A main cause of such aging is known to be oxidization, which occurs through the heat of reaction at high temperatures. Accordingly, in this study an accelerated thermal aging test was carried out in order to compare the characteristic values of the bearings with each other before and after thermal aging occurs. As a result of this experiment, it was found that a thermal aging phenomenon could have an effect on shear stiffness, energy absorption, and equivalent damping coefficients. Furthermore, a decline in the dynamic properties of the lead rubber bearings by means of the thermal aging process was applied to an actual bridge and the effects of such thermal aging on the seismic performance of the bridge were also compared and analyzed based on numerical analysis. As a result of this analysis, it was found that the changes in the basic properties of the lead rubber bearings have a minor effect on the seismic performance of bridges.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.34 no.2
• /
• pp.119-127
• /
• 2014

An epoxy coating applied to the concrete surface of a containment building deteriorates in hazardous environments such as those containing radiation, heat, and moisture. Unlike metals, the epoxy coating on a concrete liner absorbs and discharges moisture during the degradations process, so it has a different density and volume during service. In this study, acoustic impedance was adopted for characterizing the degradation of a glass-reinforced epoxy coating using the acoustic reflection coefficient (reflectance) on a rough epoxy coating. For estimating the acoustic reflectance on a wavy epoxy coating surface, a probabilistic model was developed to represent the multiple irregular reflections of the acoustic wave from the wavy surface on the basis of the simulated annealing technique. A number of epoxy-coated concrete specimens were prepared and exposed to accelerated aging conditions to induce an artificial aging degradation in them. The acoustic impedance of the degraded epoxy coating was estimated successfully by minimizing the error between a waveform calculated from the mathematical model and a waveform measured from the surface of the rough coating.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.923-931
• /
• 2008

Coupling rubber pad are important components in railway vehicles. It can be used for reduce shock, vibration and noise. Simple tension, equi-biaxial tension and pure shear test were performed to acquire the coefficient of rubber material which were Mooney-Rivlin and Ogden model. The finite element analysis was executed to evaluate the behavior of deformation and stress distribution by using the commercial finite element analysis code. Useful life evaluation are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, useful life prediction of rubber pad for railway vehicle were experimentally investigated. Accelerated heat-aging test for rubber material were carried. Compression set results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.65 no.4
• /
• pp.45-52
• /
• 2023

This study was conducted to examine the possibility of use as a structural material for ginseng cultivation facilities of recycled plastics. In order to determine the possibility that recycled plastic can replace timber used as a structural material for ginseng cultivation facilities, the specimens collected by elapsed time were compared with timber through bending tests. In addition, in order to analyze the effect of external environmental conditions on recycled plastic products, bending test was conducted with the specimens that had completed weathering test and accelerated heat aging test respectively. As a result, the bending strength of recycled plastic specimens with the elapsed time of 360 days was lower than that of timber. But bending strength of recycled plastic specimens exceeded the design allowable stress standard set by the Korea design standard (MOLIT, 2016). There was no degradation in quality of recycled plastic due to the external environment, and it was found that there would be no problem even if it was used as a structural material for ginseng cultivation facilities.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.33 no.8
• /
• pp.739-744
• /
• 2009

Rail-pad is an important and readily replaceable component of a railway track, as it is the elastic layer between the rail and the sleeper. Characteristics and useful lifetime prediction of rail-pad was very important in design procedure to assure the safety and reliability. In this paper, the degradation of rail pad properties as a function of their in-service life is studied with a view of developing a technique for predicting the optimum period of track maintenance with regard to pad replacement. In order to investigate the useful lifetime, the accelerate test were carried out. Accelerated test results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot. By using the acceleration test, several useful lifetime prediction for rail-pads were proposed.

• Elastomers and Composites
• /
• v.47 no.1
• /
• pp.9-17
• /
• 2012

Herein, life time prediction based on the deterioration of physical properties of chloroprene rubber (CR)aged by heat and seawater was performed. CR samples were experienced an accelerated test at $80^{\circ}C$, $100^{\circ}C$, $120^{\circ}C$ for heat aging, and $40^{\circ}C$, $60^{\circ}C$, $80^{\circ}C$ for seawater aging for 20,000 hrs. The change in tensile strength, maximum elongation,hardness was measured. As a result, the decrease in elongation was a major factor causing failure. The life time estimated using an Arrhenius model was 125 years at $23^{\circ}C$ for thermal aging and 9 years at $23^{\circ}C$ for seawater aging. SEM and elemental analysis reveal that cracks were generated and the content of oxygen was increased for CR agined by seawater. FT-IR spectrum shows the new C-O and C = O bonds were generated by the chemical reaction with seawater. Also, the glass transtion temperature was increased and the thermal decomposition was decreased by seawater aging.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.59 no.3
• /
• pp.230-238
• /
• 2014

The purpose of this study was to develop the cost-effective and efficiency seed longevity prediction method of rice (Oryza sativa L.) germplasm for viability monitoring. To find an optimum predicting method for rice seed longevity at genebank, an accelerated ageing (AA) test, a controlled deterioration (CD) test and a dry-heat treatment (DHT) were conducted to the four groups of rice germplasm based on ecotype, such as Indica, Japonica, Javanica and Tongil type. Among the three artificial aging treatments, the dry-heat treatment of 36 hours at $90^{\circ}C$ is suggested as a routine predictive test method of rice germplasm longevity at a genebank. The distribution of germination rate on 3,066 accessions which conserved 26.5 years at $4^{\circ}C$ showed similar trend with the result of distribution by dry-heat treatment at $90^{\circ}C$ on 36 hours using 106 accessions of rice selected samples which composed four ecotype groups. The results show that the dry-heat treatment affect not only predicting the rice seed longevity but also determining effective interval for monitoring germination of rice germplasm in genebanks.

• Elastomers and Composites
• /
• v.47 no.3
• /
• pp.254-258
• /
• 2012

Material characteristics and the prediction of life time of polyacrylic rubber (ACM) for automotive engine gasket were studied. Two kinds of ACM rubber compounds, having chlorine cure-site and carboxyl cure-site, were made with optimum formulations and the properties of each materials were examined. As a test results for the thermal properties and compression set, which are very important in the application for the automotive engine gasket, the compound using ACM with carboxyl cure-site was evaluated as having a better characteristics than that of ACM with chlorine cure-site. Arrhenius relationship based on time-temperature superposition principle (TTSP) was obtained through the accelerated heat aging test to predict the useful life-time for the compound using ACM with carboxyl cure-site.