• Journal of Surface Science and Engineering
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• v.50 no.5
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• pp.380-385
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• 2017

Mechanical characteristics of the STS 304 which is heat resistance steel were investigated after artificial aging at $650^{\circ}C$ with 1,000 hours. Tensile test specimens and small test pieces were done artificial aging up to 1,000 hours in the high temperature atmospheric environment. The results present that as the aging time increased, tensile properties were deteriorated. In the case of failure mechanism, the configuration of the fractography presented drastic change from ductile to brittle with aging time. $M_{23}C_6$ carbide leading to the change of the mechanical properties and fracture mode of the aged STS 304 steel continuously precipitated along the grain boundaries of austenite microstructure.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.41 no.1
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• pp.37-43
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• 2009

In this study, the physical properties of base paper for the manufacture of mulching mat for afforestation seedling were investigated. The base paper for mulching mat was prepared by stock conditions of PAE and AKD addition into the screened slurry of KOCC for the strengthening effects of wet tensile and burst strength. The optimum additions of PAE and AKD were considered at 2% and 0.5%, respectively. The accelerated aging by ISO 5630-1 and wet heat aging method under hot water for 2 kinds of commercial mulching and wet strength paper were compared with the base paper prepared for mulching mat manufacture. The accelerated aging test for the base paper prepared for mulching mat manufacture resulted in the same tendency of physical properties as two kinds of commercial products. However, the results of wet heat aging test under hot water indicated that the physical strength for base paper prepared was much higher than others. In addition, the opacity behavior for base paper prepared was enough effects to obstruct weeds growth by isolating transmission of sunlight.

• Journal of the Korean Society for Heat Treatment
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• v.12 no.1
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• pp.21-30
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• 1999

The present study were investigated changes of precipitation behaviour of laves phase in ferrite single phase and ferrite-martensite dual phase and precipitation of laves phase under stress. Hardness changes in ferrite phase appeared two hardness peaks by precipitation of initial fine precipitator and laves phase in 3Mo-0.3Si and 3Mo-0.3Si-C specimens, respectively. Hardness changes in martensite phase of 3Mo-0.3Si-C specimen was lower in the initial stage of aging by carbide precipitation and after this, increased by re-hardening due to precipitation of laves phase. In the ferrite phase, laves phase was mainly precipitated, whereas in the martensite phase, carbide was preferentially formed during the initial stage of aging and with increasing aging time, laves phase and carbide were simultaneously precipitated by precipitation of laves phase at around carbide. In the ferrite-martensite interface, laves phase was mainly precipitated and carbide was mainly formed at boundary of lath martensite than grain boundary. Adding the stress in aging, fine precipitator of inital precipitation of laves phase precipitated in (100) of perpendicular to tensile direction and has grown to only followed<010>direction and also, volume fraction of laves phase increased. Consequently, the stress added was accelerated initial precipitation of laves phase.

• Journal of the Korean Society for Heat Treatment
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• v.12 no.1
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• pp.1-8
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• 1999

This study has investigated the effect of aging treatment on the microstructure and mechanical properties of Mg-6Al-xZn(x = 1.5, 2.5) alloys fabricated by the squeeze casting process. The microstructures of as-squeeze cast were composed of pro-eutectic ${\alpha}$, super saturated ${\alpha}$ and ${\beta}(Mg_{17}Al_{12})$ compound. Aged at both $200^{\circ}C$ and $240^{\circ}C$, Mg-6Al-xZn alloys showed the peak hardness due to the formation of ${\beta}(Mg_{17}Al_{12})$ precipitates. The discontinuous precipitates of the lamella type are predominant at $200^{\circ}C$ aging treatment, while the finely dispersed continuous precipitates were dominant at $240^{\circ}C$ aging treatment. Mg-6Al-xZn alloys fabricated by the squeeze casting process had the better combination of tensile strength and elongation compared to the conventionally cast alloys. As zinc contents increased, the tensile strength was increased by the solid solution strengthening effect of zinc.

• Macromolecular Research
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• v.15 no.4
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• pp.315-323
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• 2007

The present manuscript deals with the prediction of the lifetime of NBR compound based rubber gaskets for use as fuel cells. The material was investigated at 120, 140 and $160^{\circ}C$, with aging times from 3 to 600 h and increasing $H_2SO_4$ concentrations of 5, 6, 7 and 10 vol%. Both material and accelerated acid-heat aging tests were carried out to predict the useful life of the NBR rubber gasket for use as a fuel cell stack. To investigate the effects of acid-heat aging on the performance characteristics of the gaskets, the properties of the NBR rubber, such as crosslink density and elongation at break, were studied. The hardness of the NBR rubber was found to decrease with decreasing acid concentration at both $120\;and\;140^{\circ}C$, but at $160^{\circ}C$, the hardness of the NBR rubber increased abruptly in a very short time at different acid concentrations. The tensile strength and elongation at break were found to decrease with increases in both the $H_2SO_4$ concentration & temperature. The observed experimental results were evaluated using the Arrhenius equation.

• Journal of the Korean Society for Heat Treatment
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• v.20 no.4
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• pp.187-194
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• 2007

A transmission electron microscope (TEM) investigation has been performed on the precipitation of $L2_1$-type $Ni_2AlTi$ phase in B2-ordered NiAl system. The hardness after solution treatment is high in NiAl-Ti alloys suggesting the large contribution of solid solution strengthening in this alloy system. However, the amount of age hardening is not large as compared to the large microstructural variations during aging. At the beginning of aging, the $L2_1$-type $Ni_2AlTi$ precipitates keep a lattice coherency with the NiAl matrix. By longer periods of aging $Ni_2AlTi$ precipitates lose their coherency and change their morphology to the globular ones surrounded by misfit dislocations. Misfit dislocations, which are observed on {100} planes of H-precipitates have the Burgers vector of a <100> with a pure edge type. The lattice misfits of NiAl-$Ni_2AlTi$ system is estimated from the spacings of misfit dislocations to be 1.1% at 1273 K. The lattice misfits decrease with increasing aging temperature in this system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.05a
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• pp.49-51
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• 1988

The heat treatment condition and aging behavior of melt spun amorphous $Fe_{78}B_{13}Si_9$(Metglas 26058-2) were studied with investigating its magnetic properties, i.e., Br, $B_l$, Hc. The optimum heat treatment condition was $400^{\circ}C$, 1 hour under the external field of 200e, and aging was due to the surface oxidation and the appearance of local CSRO (chemical short lange order) with time and temperature. In addition. we investigated the effects of the thickness of the amorphous ribbons on the magnetic properties and aging effect of them.

• Korean Journal of Acupuncture
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• v.30 no.3
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• pp.171-177
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• 2013

Objectives : The purpose of this study is to investigate the mechanism of Cosmetic Acupuncture through reinterpretation of anatomy and physiology. Methods : The causes of wrinkle increases and rapid aging of facial skin were studied and the theoretical system of Cosmetic Acupuncture treatment was analyzed through anatomy and physiology reinterpretation. Results and Conclusions : An increase in wrinkles and rapid aging of facial skin is caused by xerosis. Skin condition represents the condition of subcutaneous muscle. The reason why skin becomes easily dry is the heat produced by craniofacial part. Craniofacial part always generates lot of physiological fever because of the muscles. This physiological fever is produced from the muscles that are responsible for maintaining skull suture, controlling the movement of temporomandibular joint, maintaining head and neck posture. Controlling this fever is the crux of Cosmetic Acupuncture mechanism. These muscles correspond to Foot Taeyang meridian-muscle, Foot Soyang meridian-muscle and Foot Yangmyung meridian-muscle. Cosmetic Acupuncture is effective for preventing facial skin from aging and wrinkle increase by mechanical stimulus on facial muscles, and for controlling craniofacial part meridian-muscle system producing the heat.

• Journal of Power System Engineering
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• v.20 no.5
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• pp.37-45
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• 2016

Exhaust gas recirculation has the advantage of being low-cost and easy to control of NOx emission. Therefore, it is most generally used to reduce NOx emission according to strengthen regulation. In the case of a non-road engine, such as the agricultural engine, since it mainly operate a middle or high-load state, NOx emission is decreased in accordance with the mapping range of the EGR rate, but results in an increase in the particulate matter which is caused to deposit and fouling problem of the EGR system. This problem has become an important issue for maintaining the performance of the engine, as well as emission performance. This study had examined the effects of cooler aging on the performance of heat transfer efficiency and NOx emission in non-road diesel engine. As a result of the EGR cooler aging during 200 hours engine operation, the cooling performance decreased about 25% compared with that of fresh cooler and the NOx emission increased about 14.6% on NRSC(non-road steady cycle) and 20% on NRTC(non-road transient cycle) compared with that of fresh cooler respectively.

• Journal of Korea Foundry Society
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• v.31 no.5
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• pp.262-266
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• 2011

The aim of this study is to investigate aging behavior of A356 alloy for turbo charger part. The specimen was fabricated by investment casting. Solution heat treatment was performed at $525^{\circ}C$ for 8h and followed by aging treated at $160^{\circ}C$, $170^{\circ}C$ for 0.5~20h. And their microstructures and mechanical properties of the aged specimens were analyzed by scanning electron microscope and hardness tester, respectively. All the cast A356 alloy included eutectic Si particles. In the cast A356 alloy, eutectic Si phase mainly was formed along Chinese script phase. Vickers hardness of the cast was improved by aging treatment due to formation of ${\beta}$" phase and ${\beta}$' phase.