• Bulletin of the Korean Chemical Society
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• 제18권8호
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• pp.886-889
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• 1997

The crystal structure and optical properties of copper nanoparticles, prepared in fused silica by ion-implantation and subsequent heat-treatment, were characterized by X-ray, TEM, linear absorption, and degenerate four-wave mixing (DFWM) technique. The X-ray data show fcc lattice structure of the nanocrystals and their size was measured as 8-20 nanometer by high resolution TEM. Using DFWM, the third-order nonlinear optical coefficient of the Cu-SiO2 thin films was measured as 0.4-1.1×10-8 esu in the surface plasmon resonance absorption region (540-570 nm).

• 비파괴검사학회지
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• 제37권2호
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• pp.115-121
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• 2017

The nonlinear ultrasonic technique is a potential nondestructive method to evaluate material degradation, in which the ultrasonic nonlinearity parameter is usually measured. The ultrasonic nonlinearity parameter is defined by the elastic nonlinearity coefficients of the nonlinear Hooke's equation. Therefore, even though the ultrasonic nonlinearity parameter is not equal to the elastic nonlinearity parameter, they have a close relationship. However, there has been no experimental verification of the relationship between the ultrasonic and elastic nonlinearity parameters. In this study, the relationship is experimentally verified for a heat-treated aluminum alloy. Specimens of the aluminum alloy were heat-treated at $300^{\circ}C$ for different periods of time (0, 1, 2, 5, 10, 20, and 50 h). The relative ultrasonic nonlinearity parameter of each specimen was then measured, and the elastic nonlinearity parameter was determined by fitting the stress-strain curve obtained from a tensile test to the 5th-order-polynomial nonlinear Hooke's equation. The results showed that the variations in these parameters were in good agreement with each other.

• Asian-Australasian Journal of Animal Sciences
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• 제2권2호
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• pp.99-102
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• 1989

The level of serum alkaline phosphatase activity was determined in 7 Japanese Black steers at different ages. The isoenzyme activity of non-bone origin was estimated using a heat-inactivation technique. The activity of serum alkaline phosphatase (SALP, K-A unit) decreased as age (AGE, mo.) increased: SALP = 14.15 - 0.17 (${\pm}\;0.03$) AGE, r = -0.81, P<0.01, $S.E.\;{\pm}\;0.28$. The variation of the activity was greater in younger age than the older. The temperature of $58^{\circ}C$ for the treatment of heat inactivation of bovine serum appeared to be suitable. The percentage of heat inactivated enzyme activity negatively correlated with age and positively with the level of serum alkaline phosphatase activity. The activity of SALP of non-bone origin was inferred to stay at about constant level irrespective of age and that of bone origin decreased with age.

• 한국해양공학회지
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• 제15권3호
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• pp.81-86
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• 2001

Ultrasonic travel-times obtained with the LCR ultrasonic technique have shown an ability to distinguish among three aluminum plates. The 244$\times$150mm thick, but differ in heat treatment. One is fully annealed, the second is quenched and then tempered, and the third is heat-treated to T651 plate, as received plate. Travel-times were obtained at four locations on each side of all plates. The data for both sides of each plate clearly are in very close agreement except location 1 of each plate. In order to show travel-time variation throughout the plate areas, the average travel-time for both sides of each plate were calculated. For Plate 1, the travel-time data were the highest and the data of Plate, the travel-time data were the highest and the data of Plate 2 were upper than Plate 3. Finally, the residual stresses for each plate were measured by X-ray diffraction method. The results showed a good relation. These preliminary results indicate that the LCR Ultrasonic Technique may be not only further developed for use in quality control in the manufacture of rolled aluminum plates but also industry.

• 한국자동차공학회논문집
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• 제13권6호
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• pp.128-134
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• 2005

In order to fabricate the aluminum alloys with good drawability, the textures evolution of the AA5182 sheets after rolling and annealing was studied. The measurement of the deformation textures was carried out for the sheets which were cold rolled with high reduction ratio by using the symmetric roll. In addition, the change of the recrystallization texture was investigated after heat-treatments of the rolled sheets with various heat treatment conditions. Rolling without lubrication and subsequent annealing led to the formation of favorable $rot-C_{ND}\;\{001\}<110>\;and\;{\gamma}-fiber ND//<111>$ textures in AA5182 sheets. From the results, the ${\gamma}$-fiber ND//<111> component well evolved during rolling at highest reduction ratio (over $90\%$, l/d parameter of 6.77). Among shear deformation textures, the ${\gamma}$-fiber ND//<111> was not rotated in holding time of $180\~7,200$ seconds at $350^{\circ}C$. The Monte-Carlo technique was used and could be representatively simulated these textures evolution during recrystallization.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2000년도 특별강연 및 추계학술발표대회 개요집
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• pp.260-263
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• 2000

A methodology is developed and many used to evaluate the response sensitivity of the thermal systems to variations in their design parameters. Technique for computing the sensitivity of temperature distributions to changes in processing parameters needed for deciding the more effective laser input parameters for laser surface hardening treatment are considered. In this study, a state equation governing the heat flow in laser surface treatment is analyzed using a three-dimensional finite element method and sensitivity data of the processing parameter obtained using a direct differentiation method applied for sensitivity analysis. The interesting processing parameter is taken as the laser scan velocity and characteristic beam radius( $r_{b}$) of the sensitivity of the temperature T versus v and $r_{b}$ is analyzed. And these sensitivity results obtained in another parameters are fixed condition. To verifying the numerical analysis results, hardened layer dimensions (width and depth) of the numerical analysis compared with the results of an experimental data.ata.

• 대한기계학회논문집A
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• 제36권3호
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• pp.319-324
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• 2012

이산화탄소에 대한 규제가 강화되면서 환경 보호를 위하여 차량의 경량화를 요구하고 있다. 이를 위하여 다른 재질, 두께 및 강도를 갖는 소재를 맞춤 블랭크로 제조하여 활용하는 TWB 기술과 오스테나이트 변태온도 이상으로 승온, 스탬핑 ��칭하는 핫스탬핑용 보론강을 이용한 열간 성형 기술을 접목함으로써 경량화 및 고안전성을 확보할 수 있다. 따라서 본 연구에서는 레이저 용접된 보론 강판의 열처리 온도를 달리하여 다이��칭 조건에 따른 기계적 특성을 조사하였다. 레이저 용접한 보론 강판을 다이 ��칭한 후 인장 시험한 결과, 최대인장강도 1454 MPa, 연신율은 6 %로 나타났으며, 이것은 용접하지 않은 모재 열처리재 인장강도, 1522 MPa의 95.5 %이다. 이 값은 핫스탬핑용 보론강 용접재의 실용적인 데이터로 활용될 수 있을 것이다.

• 한국생산제조학회지
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• 제23권1호
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• pp.48-55
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• 2014

Many techniques are available for destructive and nondestructive measurement of mechanical hardness. The ultrasonic method could be widely applicable as a nondestructive technique. Many studies have examined how changes in the mechanical hardness affect the longitudinal velocity of ultrasonic waves. This approach aims to estimate the overall velocity variations in specimens. However, proper nondestructive examination techniques are needed as effective tools for analyzing the effects of heat treatment on the surface of the specimens. Therefore, in this study, the effect on the hardness of piston rods was nondestructively measured using surface ultrasonic waves. The hardness after heat treatment was investigated at various depths in the specimens, and the velocity of the surface ultrasonic waves was measured with respect to the hardness of the piston rods. In addition, finite element method simulations were performed to confirm the behavior of the waves.

• 열처리공학회지
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• 제9권4호
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• pp.289-299
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• 1996

This study has been performed to investigate into some effects of power density and traverse speed of laser beam on the microstructure, hardness and residual stress of AISI 4140 treated by laser surface hardening technique. Optical micrograph has shown that large martensite and a small amount of retained austenite in outermost surface layer and fine lath martensite in inner surface hardened layer are formed under the condition of a given power density and traverse speed. Hardness measurements have revealed that as the power density increases at a given 2.0m/min of the traverse speed, the maximum hardness values of outermost surface hardened layer is increased from Hv=635 to Hv=670. X-ray analysis for residual stress has exhibited that low compressive residual stress values are obtained in center point of the cress section of surface hardened layer with in mid point between the edge and the center point, about 1.5mm from the center point, due simply to a difference in self-quenching rate. It has been shown that the higher the power density at a given traverse speed and the olwer the traverse speed at a given power density, the more the compressive residual stress values are increased due to an increase in the input heat of laser beam.

• 대한기계학회논문집A
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• 제35권4호
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• pp.383-391
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• 2011

최근 차체 경량화를 위한 여러 가지 방법 가운데 고온에서 가공하여 성형성을 확보하고, 이후 열처리를 통하여 고강도를 가질 수 있는 프레스 열간 성형 및 핫스탬핑 기술이 각광을 받고 있으며, 이에 따라 핫스탬핑용 재료인 보론 첨가 강판의 수요도 늘어나고 있는 추세이다. 본 연구에서는 핫스탬핑용보론 첨가 강판의 우수한 경화능을 보이는 임계 최적 열처리 조건을 파악하고자, Al+Si 코팅이 된 보론강판을 각기 다른 온도로 열처리하여 수냉 조건에 따른 기계적 특성 및 조직을 관찰하였다. 또한, 이 결과를 토대로 선별된 기계적 특성이 우수한 보론강 시험편과 일반 냉연 강판인 SPRC 340과 SPRC 590 2종류의 상대재를 활용하여 특정 점용접 조건에서 용접을 실시하고, 보론강 및 상대재의 기계적 특성 변화에 따른 용접 후의 기계적 특성 및 조직, 그리고 코팅층 유무에 따른 특성 변화를 연구하였다.