• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.2
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• pp.81-88
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• 2014

Synthetic products such as casting tape and splints are rapidly replacing conventional plaster casts to treat orthopedic patients. Most synthetic products are produced through a polymerization process with related chemical agents. In this study, the effect of the process parameters on the residual NCO content within a prepolymer for casting tape and the hardening temperature for casting tape were experimentally evaluated. In order to verify the effects of the process parameters, an experimental method was adopted. From an S/N ratio analysis, optimal parameter combinations were determined to produce a pre-polymer with a suitable residual NCO content and alower hardening temperature. Prediction models for the NCO content and the hardening temperature were developed and confirmed.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.5
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• pp.319-329
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• 2016

The Eradi Quake System (EQS) is a seismic isolation bearing system designed to minimize forces and displacements experienced by structures subjected to ground motion. The EQS dissipates seismic energy through friction of Poly Tetra Fluoro Ethylene (PTFE) disk pad. In general, a force-displacement relationship of EQS has post yield stiffness hardening during large inelastic displacement. In this study, seismic responses of seismically isolated nuclear power plant (NPP) subjected to design basis earthquake (DBE) and beyond design basis earthquakes (150% DBE and 167% DBE) are compared considering the post yield stiffness hardening effect of EQS. From the results, it can be observed that if the post-yield stiffness hardening effect of EQS is increased, the displacement response of EQS is reduced, and the acceleration and shear responses of containment structures of NPP is increased.

• Structural Engineering and Mechanics
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• v.5 no.6
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• pp.755-765
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• 1997

Within the framework of anisotropic combined viscoplastic hardening formulation, accounting macroscopically for residual stress as well as texture development at finite deformations of metals, simple shear analyses for the simulation of fixed-end torsion experiments for ${\alpha}$-Fe, Al and Cu at different strain rates are reviewed with an emphasis on the role of constitutive spins. Complicated responses of the axial stresses with monotonically increasing shear deformations can be successfully described by the capacity of orthotropic hardening part, featuring tensile axial stresses either smooth or oscillatory. Temperature effect on the responses of axial stresses for Cu is investigated in relation to the distortion and orientation of yield surface. The flexibility of this combined hardening model in the simulation of finite inelastic strains is discussed with reference to the variations of constitutive spins depending upon strain rates and temperatures.

• Structural Engineering and Mechanics
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• v.38 no.2
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• pp.231-247
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• 2011

This study introduces a new load increment method for the ductile reinforced concrete (RC) frame structures by including strain-hardening effects. The proposed method is a nonlinear static analysis technique employed for RC frame structures subjected to constant gravity loads and monotonically increasing lateral loads. The material nonlinearity in RC structural elements is considered by adopting plastic hinge concept which is extended by including the strain hardening as well as interaction between bending moment and axial force. Geometric non-linearity, known as second order effect, is implemented to the method as well.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.5
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• pp.813-823
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• 2023

In this study, microstructure, hardening layer hardness, and case depth were evaluated after induction hardening(IH) of base metal specimen(BM) treated with annealing and quenching-tempering specimen(QT) treated with quenching and tempering. The microstructure after IH was significantly influenced by the microstructure before IH and the induction coil heating movement speed, but the effect of the induction frequency was very small. The hardness of the hardened layer at an induction coil heating movement speed of 15 mm/s or less was more influenced by the microstructure before IH than the induction coil travel speed and induction frequency. The induction coil travel speed has the significantly effect on the case depth, the induction frequency has effect and the microstructure before IH has a small effect.

• Korean Security Journal
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• no.56
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• pp.9-30
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• 2018

Crime prevention strategies are introduced to reduce the loss caused by crimes, and Target hardening against domestic burglary attacks is broadly accepted as one of such physical security strategies. In terms of business and home security, target hardening is one of the suite of protective measures that are included in crime prevention through environmental design(CPTED). This can include ensuring all doors and windows are sourced and fitted in such a way that they can resist forcible and surreptitious from the attack of intruder. Target hardening with certified security doors, security windows and secure locks are revealed to be much more effective to deter burglary attacks than other security devices, such as CCTV, lightings and alarms which have largely psychological and indirect impact. A pilot program of target hardening utilizing certified security window and locks was carried out in Ansan city, South Korea in 2016. This study is based on the quasi-experimental design of this program for a residential area. The researchers tried to verify the crime displacement effect of the target hardening program and the diffusion effects of crime prevention benefits by analysing the crime statistics. The evaluation utilized WDQ(Weighted Displacement Quotient) technique to analyze whether the crime displacement occurred, compared the crime statistics of the experimental area with that of buffer zone and controlled areas. The result showed that the target hardening program was significantly effective in crime prevention. The number of burglary in the experimental site with target hardening intervention reduced by 100%, although the areas without the intervention showed reduction in the burglary. The crime displacement was not found at all, and the number of burlary at the buffer zone also reduced significantly.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.207.2-207
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• 2003

• Journal of Mechanical Science and Technology
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• v.17 no.4
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• pp.477-483
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• 2003

An independent kinematic hardening material model in which the reverse yielding point is defined by the Bauschinger effect factor (BEF) , has been defined for stainless steel SUS 304. The material model and the BEF are obtained experimentally and represented mathematically as continuous functions of effective plastic strain. The material model has been incorporated in a non-linear stress analysis for the prediction of reverse yielding in thick-walled cylinders during the autofrettage process of these vessels. Residual stress distributions of the independent kinematic hardening material model at the onset of reverse yielding are compared with residual stresses of an isotropic hardening model showing the significant effect of the BEF on reverse yielding predictions. Critical pressures of direct and reverse yielding are obtained for the most commonly used cylinders and a range of permissible internal pressures for an efficient autofrettaged process is recommended.

• Journal of the Korean GEO-environmental Society
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• v.24 no.5
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• pp.21-28
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• 2023

In this paper, an experimental study was conducted to present the properties of rapid hardening composite mat, and a numerical analysis was carried out to analyze the slope protection effect of the mats based on ground conditions, rainfall, slope gradient and soil height. As a result, the application of rapid hardening composite mat increased the slope safety factor in all conditions, and the increase rate of safety factor showed an average of 40% increase both in dry and rainy seasons. Through these research findings, the protective effect of the rapid hardening composite mat on sloping surfaces has been proven, and it is suggested that the rapid hardening composite mat is suitable for application in areas where slope failure or collapse is expected.

• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.203-210
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• 2011

Bake hardening steels have to resist strain aging to prevent the yield strength increment and stretcher strain during press process and to enhance the bake hardenability during baking process after painting. The bake hardening steels need to control the solute carbon and the solute nitrogen to improve the bake hardenability. Ti and/or Nb alloying for nitride and carbide precipitation and low carbon content below 0.003% are used to solve strain aging and formability problem for automotive materials. However, in the present study, the effect of micro-precipitation of copper sulfide on the bake hardenability and fatigue properties of extremely low carbon steel has been investigated. The bake hardenability of Cu-alloyed bake hardening (Cu-BH) steel was slightly higher (5 MPa) than that of Nb-alloyed bake hardening (Nb-BH) steel, but the fatigue limit of Cu-BH steel was far higher (45 MPa) than that of Nb-BH steel. All samples showed the ductile fracture behavior and some samples revealed distinct fatigue stages, such as crack initiation, stable crack growth and unstable crack growth.