• Title/Summary/Keyword: hardening zone

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A Study on Hardening Zone by Vacuum Consolidation Drainage Method (진공압밀 배수공법에 의한 Hardening Zone에 대한 연구)

  • Chung, Youn-In;Kim, Hee-Joong;Chang, Chun-Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.8 no.3
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    • pp.197-205
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    • 2004
  • The relationships were studied between the range of hardening zone and the intensity of vacuum pressure in case of applying vacuum consolidation drainage method for soil improvement. A testing apparatus was made to measure the range of hardening zone varying the water content and the intensity of vacuum pressure for 3 different the highly compressible dredged clays(Gwangyang, Busan and Mokpo). In case of applying high vacuum pressure, the hardening zone is not spreaded as compared to low vacuum pressure because of the clogging of drainage and developed hardening zone near the drainage.

A Study on the Effect of Beam Mode on the Size of Hardened Zone in Laser Surface Hardening (레이저 표면경화처리에서 빔의 형태가 경화층 크기에 미치는 영향에 관한 연구)

  • Kim, J.W.
    • Journal of the Korean Society for Precision Engineering
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    • v.10 no.4
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    • pp.64-72
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    • 1993
  • Analytical models for the prediction of the size of hardened zone in laser surface hardening are presented. The models are based on the solutions to the problem of three-dimensional heat flow in plates with infinite thickness. The validity of the model was tested on medium carbon steel for Gaussian mode of beam. Then the model for rectagular beam was used for the predicition of the size of hardened zone on various hardening process parameters. From the calculation results it appeared that the size and shape of the hardened zone are strongly dependent on process parameters such as beam mode, beam size, and traverse speed.

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Characteristics of Hardening Zone by Suction Pressure in Suction Drain Method (석션드레인 공법에서 적용 부압에 따른 Hardening Zone의 특성)

  • Han, Sang-Jae;Kim, Ki-Nyun;Kim, Soo-Sam
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.2C
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    • pp.75-81
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    • 2008
  • In this study, a series of laboratory column test on Suction Drain Method which is one of the way to make an soft ground improvement were conducted in order to investigate the effect of the Hardening Zones and the ratio of improvements depending on periods of the improvements and various applied suction pressures. On this occasion, the experimental conditions are followings; in the case of the periods of effectiveness, 4 days, 8 days, 12 days, 16 days, 20 days and in the case of the applied pressures of the Suction are -20 kPa, -40 kPa, -60 kPa and -80 kPa were carried out. As a result of test, settlement increased with suction pressure and duration increase, and gradually converged. Also, as comparing permeability decrease ratio with which calculated back from water content and numerically predicted using Hansbo's radial consolidation theory, measured value was almost coincide with predicted value when permeability decrease ratio was assumed as 2~3. Furthermore, the hardening zone was appeared within 7~8 cm of whole radial (25 cm).

레이저 표면경화처리에서 빔의 형태에 따른 경화층 크기에 관한 연구

  • 김재웅
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1993.04b
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    • pp.13-17
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    • 1993
  • Analytical models for the prediction of the size of hardened zone in laser surface hardening are presented. The models are based on the solutions to the problem of three-dimensional heat flow in plates with infinite thickness. The validity of the model was tested on medium carbon steel for Gaaussian mode of beam. Then the model for rectangular beam was used for the prediction of the size of harened zone on various hardening process parameters. From the calculation results it appeared that the size and shape of the hardened zone are strongly dependent on process parameters suchas beam mode, beam size, and traverse speed.

Surface Hardening Characteristics of SK5 Steel by Pulsed YAG LASER (YAG 레이저에 의한 SK5 표면경화 특성)

  • 강형식;문종현;전태옥;박홍식
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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    • pp.921-924
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    • 1995
  • Case hardening behavior of carbon tool steel(SK5) was investigated after pulsed YAG laser irradiation. In the case od beam passes,martensite formed in the melt zone and in former pearlite regions of the austenitization zone exhibits vary high Vickers hardness values. The molten depth and width decrease as the beam power density increase. The influence of depth and width of color painted specimen was also investigated. The molten zone of the black painted specimen was the largest. The were loss of the black painted specimen was smaller than any other painted or raw material.

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Two Back Stress Hardening Models in Rate Independent Rigid Plasticity (변형률 독립 강소성 구성 방정식에서의 이중 후방 응력 경화 모델)

  • Yun S. J.
    • Transactions of Materials Processing
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    • v.14 no.4 s.76
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    • pp.327-337
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    • 2005
  • In the present work, the two back stress kinematic hardening models are proposed by combining Armstrong-Frederick, Phillips and Ziegler's hardening rules. Simple combination of hardening rules using simple rule of mixtures results in various evolutions of the kinematic hardening parameter. Using the combined hardening models the ultimate back stress fur the present models is also derived. The stress rate is co-rotated with respect to the spin of substructure due to the assumption of kinematic hardening rule in finite deformation regime. The work piece under consideration is assumed to consist of the elastic and the rigid plastic deformation zone. Then, the J2 deformation theory is facilitated to characterize the plastic deformation behavior under various loading conditions. The plastic deformation localization behaviors strongly depend on the constitutive description namely back stress evolution and its hardening parameters. Then, the analysis for Swift's effects under the fixed boundaries in axial directions is carried out using simple shear deformation.

Seismic Overstrength of Low-rised RC Frame in Korea (국내 저층 콘크리트 골조의 초과강도)

  • 이영욱
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1998.10a
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    • pp.28-35
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    • 1998
  • The seismic overstrength factor $\Omega$ is evaluated for 4-story reinforced concrete buildings in Korea(of which seismic intensity is low). The study model is designed according to aseismic guideline research - phase II in Korea. The effect of variation of span length and bay number, dead load is considered, especially including the variation of hardening ration after yielding. And push-over analysis is performed, in which the external and internal frame is connected by rigid-link and the $\Omega$ is calculated using the roof drift ratio at 2%. For Zone I, the mean value of $\Omega$ is ranged form 2.3 to 2.5, For Zone II, from 3.1 to 3.4. For low hardening ratio(3%) after yielding, $\Omega$ has little relations with the number of bay, like as the results of other research. But for 5% hardening ratio, $\Omega$ is increased as the number of bay is increased. Within general gravity-load bound, the variation of D.L. has variation of D. L. has no effect on $\Omega$. And, $\Omega$ is increased as the span length is increased.

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Characteristics of Surface Hardened Press Die Materials by CO2 Laser Beam Irradiation (CO2 레이저 빔 조사에 의한 프레스 금형재료의 표면경화 특성)

  • Yang, Se-Young;Choi, Seong-Dae;Choi, Myeong-Soo;Jun, Jae-Mok
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.1
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    • pp.31-37
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    • 2011
  • Recently, the technology of surface treatment is being more important which affects the material cost reduction and substitution to the expensive material. The material used for the mechanical processing should have not only high intensity, but also strength toughness, wear resistance and corrosion resistance. In order to increase the durability and have better quality of the parts using such kind of tooling material, various kinds of research of the surface hardening through many kinds of heat resources is being done and practically applied. In this study, the characteristics of hardening surface zone for high strength of the press die material through laser beam irradiation are researched. In this study, it is experimentally observed by the status of the surface morphology, tensile strength, the hardness distribution of the base metal and wear condition by the surface hardness pattern by the laser beam based on the process parameters of $CO_2$ laser by using SM45C and STD11 used for press tool. Through this research, the characteristics of surface hardened zone for high strength of the thin metal by laser beam irradiation is done.

Characteristics of Surface Hardening by Laser Power Control in Real Time of Spheroidal Graphite Cast Iron (실시간 출력 제어를 통한 구상흑연 주철의 레이저 표면경화 특성)

  • Kim, Jongdo;Song, Mookeun
    • Laser Solutions
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    • v.18 no.2
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    • pp.1-4
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    • 2015
  • This study is related to the surface hardening treatment to spheroidal graphite cast iron for die by using high power diode laser. Laser device used in this experiment is capable of real-time laser power control. This is because the infrared temperature sensor (two color pyrometer) attached to the optical system measures the surface temperature of specimen and adjusts the laser power in real time. The surface treatment was carried out with the change of heat treatment temperature at the beam travel speed 3 mm/sec. Hardened width and depth was measured and hardened zone was analyzed by micro vickers hardness test in order to research the optimum condition of heat treatment. The changes in microstructure of the hardened zone also was examined. As a result of hardness measurement and observations on microstructure of hardened zone, hardness increased over three times as compared with base metal because the martensite was formed on the matrix structure.

The Characteristics of Ductile Cast Iron Heat-treated by $CO_2$Laser (구상흑연주철의 $CO_2$레이저 표면경화 특성)

  • 정원기;전병철;김재도
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.04a
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    • pp.998-1002
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    • 1997
  • This study has been performed to predict beam absorption with analysis of temperature field by using a FEM in co /sab 2/ laser hardening and to invesrigate into some effects of power density and travel speed of laser beam on the microstructure and hardness of ductile cast iron treated by laser surface hardening technique. Optical micrograph has shown that large martensite and small amount of retained austenite appear in inside hardened zone. Hardness measurement has revealed that the range of maximum hardness value is Hv=415 .+-. 10. The power density increases and the travel speed decreases, the depth of hardened zone increases due to increase of input power density.

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