• Proceedings of the Korea Information Processing Society Conference
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• 2003.05a
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• pp.431-434
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• 2003

본 논문에서는 Linux 운영체제에서의 kernel hardening을 설계한다. 커널 내에서 panic 이 발생할 경우 복구가 가능한 경우에는 정상적인 동작이 될 수 있도록 한다. 이렇게 함으로써 Linux Kernel Hardening 기능은 안정적인 커널의 동작을 보장한다. 본 논문에서 Linux Kernel Hardening을 보장하기 위하여 커널 내 ASSERT(), BUG() 함수를 중심으로 설계를 한다.

• Korean Journal of Materials Research
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• v.30 no.6
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• pp.315-320
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• 2020

This study deals with the yielding behavior and strain aging properties of three bake hardening steels with dual-phase microstructure, fabricated by varying the annealing temperature. Bake hardening and aging tests are performed to examine the correlation of martensite volume fraction with yielding behavior and strain aging properties of the bake hardening steels with dual-phase microstructure. The volume fraction of martensite increases with increasing annealing temperature. Room-temperature tensile test results show that the yielding behavior changes from discontinuous-type to continuous-type with increasing volume fraction of martensite due to higher mobile dislocation density. According to the bake hardening and aging tests, the specimen with the highest fraction of martensite exhibited high bake hardening with low aging index because solute carbon atoms in ferrite and martensite effectively diffuse to dislocations during the bake hardening test, while in the aging test they diffuse at only ferrite due to lower aging temperature.

• Structural Engineering and Mechanics
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• v.56 no.3
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• pp.369-383
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• 2015

In this study, effect of various material hardening models based on Holloman's isotropic, Ziegler's linear kinematic, non-linear kinematic and mixture of the isotropic and nonlinear kinematic hardening laws on springback prediction of titanium alloy (Ti-3Al-2.5V) in a tube rotary draw bending (RDB) process was investigated with presenting the keynotes for a comprehensive step by step ABAQUS simulation. Influence of mandrel on quality of the final product including springback, wall-thinning and cross-section deformation of the tube was investigated, too. Material parameters of the hardening models were obtained based on information of a uniaxial test. In particular, in the case of combined iso-nonlinear kinematic hardening the material constants were calibrated by a simple approach based on half-cycle data instead of several stabilized cycles ones. Moreover, effect of some material and geometrical parameters on springback was carried out. The results showed that using the various hardening laws separately cannot describe the material hardening behavior correctly. Therefore, it is concluded that combining the hardening laws is a good idea to have accurate springback prediction. Totally the results are useful for predicting and controlling springback and cross-section deformation in metal forming processes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.154-157
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• 2008

It is important to know the variations of the mechanical properties in the hydroforming process for the safe and durable design purposes. In this study, strain hardening behavior during hydroforming has been investigated by hydroforming of engine cradle as a model process. The variation of mechanical properties such as local hardness and flow stress were used as an index of strain hardening during respective processes. By using the inter-relationships between hardness-flow stress-effective strain at variable pre-strains, the strain hardening behavior during hydroforming has been successfully analyzed. The comparison of predicted hardness with measured hardness confirmed that the methodology used in this study was feasible and the strain hardening behavior can be quantitatively estimated.

• Journal of the Korean Society for Nondestructive Testing
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• v.11 no.1
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• pp.38-43
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• 1991

The relationship between eddy current response and case hardening depth has been studied on SM40C(KS D-3752) and SCM440(KS D-3711) steels which were surface hardened by high frequency induction hardening. The results obtained in this study were as follows ; 1) Case hardening depth was successfully measured by observing the eddy current impedance changes of each steel. The impedance decreased linearly with increasing case hardening depth. 2) For large impedance gradient between the hardened surface and core metal, the eddy current response was more sensitive to case hardening depth than for low impedance gradient.

• Korean Journal of Materials Research
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• v.11 no.11
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• pp.1001-1005
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• 2001

In this study, the surface of 40Cr steel was hardened by $CO_2$Laser, and then the microstructural transformations and the hardness distributions of the laser surface hardened layer were observed. The experimental results showed the surface hardening layer was consisted of three parts, which is outmost surface layer of needle martensite, middle layer of martensite and remained pearlite, and transitory boundary layer. In hardness distributions, the surface hardeness of the surface hardening layer had Hv 800~1000, that was 2 to 4 times of matrix's hardness. The hardeness distribution of laser hardening layer that of surface layer hardened by general heat treatment.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.118.5-118
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• 2002

To apply induction hardening method to a press die having 3-D free surface, the induction hardening tool moves on a press die above 1～2mm gap with constant velocity. Since the induction hardening process requires its own hardening path for each die, a direct teaching method which generates working path directly guided by operators is more suitable than an offline method using CAD/CAM data. The direct teaching apparatus in this work includes a teaching tool with a force/torque sensor and data processing computer to finally generate robot's Induction hardening program , in direct teaching operation, an operator teaches working path maintaining contact with surface of press die by holding...

• Architectural research
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• v.14 no.4
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• pp.153-161
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• 2012

This paper presents an integrated procedure to predict the temperature and moisture distributions in hardening concrete considering the effects of temperature and aging. The degree of hydration is employed as a fundamental parameter to evaluate hydro-thermal-mechanical properties of hardening concrete. The temperature history and temperature distribution in hardening concrete is evaluated by combining cement hydration model with three-dimensional finite element thermal analysis. On the other hand, the influences of both self-desiccation and moisture diffusion on variation of relative humidity are considered. The self-desiccation is evaluated by using a semi-empirical expression with desorption isotherm and degree of hydration. The moisture diffusivity is expressed as a function of degree of hydration and current relative humidity. The proposed procedure is verified with experimental results and can be used to evaluate the early-age crack of hardening concrete.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.564-569
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• 2008

Strain hardening behavior during hydroforming has been experimentally investigated. The variation of flow stress was used as an index of strain hardening during respective processes and the flow stress was estimated from the correlationship between flow stress and effective strain. The local hardness after hydroformig was also predicted by effective strain. By using the inter-relationships between hardness-flow stress-effective strain at variable pre-strains, the strain hardening behavior during hydroforming has been successfully analyzed. The comparison of predicted hardness with measured hardness confirmed that the methodology used in this study was feasible and the strain hardening behavior can be quantitatively estimated.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.13 no.2
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• pp.67-74
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• 2017

Recently there have been many concerns on structural integrity of nuclear piping under seismic loadings. In terms of failure of nuclear piping due to seismic loadings, an important failure mechanism is low cycle fatigue with large cyclic displacements. To investigate the effects of seismic loading on low cycle fatigue behavior of nuclear piping, the cyclic behavior of materials and nuclear piping needs to be accurately estimated. In this paper, the non-linear finite element (FE) analyses have been carried out to evaluate the effects of three different cyclic hardening models on cyclic behavior of materials and nuclear piping, such as isotropic hardening, kinematic hardening and combined hardening.