• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.250-253
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• 2000

The fiber orientation in FRP has a great effect on the strength of FRP because the strength of FRP mainly depends on the strength of fiber. Unidirectional FRP made by pultrusion method has comparatively lower compressive strength than tensile strength. Compressive strength of unidirectional FRP may be increased by filament winding layer which has tensile stress when compressive stress was loaded. In this study, compressive strength and stresses of FRP rods were simulated according to the winding orientation of glass fiber. Inner part of FRP was made unidirectionally by pultrusion method and outer part of FRP was made by filament winding method. Simulated value and real evaluated compressive strength were compared to investigate stresses which is prominent to the fracture of FRP. The shear stresses had a great effect on the strength of FRP although the stress of parallel direction of FRP was much higher.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.6
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• pp.109-118
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• 1991

In this study, it is intended to investigate the effect of the grinding conditions such as table feed, down feed, cross feed of residual stress distribution. And this distribution is investigated upon the grinding direction and the its orthogonal direction at ground layers. The material is used carbon steel (SM20C) which usually used to motor axis. And in order to be considered as Bernoulli-Euler beam, the dimension of the specimen is appropriately designed. According as corroiding the ground surface, the residual stress layers are removed and strain which occured on account of unbalance of internal stress is detected by rosette-gate. Through A/D converter and computer, these values are saved and evaluated residual stress by stress-strain relation formula. Finally, these results are diagrammatized with Auto Cad. The results obtained are as follows. As the depth from the ground surface increases in grinding direction and its orthogonal direction, tensile residual stress exists in the surface, and subsequently it becomes compressive residual stress as it goes downward. As the table feed, the cross feed and the down feed increase, maximum residual stress is transformed form the tensile to the compressive.

• Tunnel and Underground Space
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• v.2 no.2
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• pp.224-236
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• 1992

It is very important to determine the thermo-mechanical characteristics of the rock mass surrounding the repository of radioctive waste and the LPG storage cavern. In this study, Hwasoon-Shist. Dado-Tuff adn Chunan-Tonalite were the selected rock types. Temperature dependence of the mechanical properteis such as uniaxial compressive strength, tensile strength, Young's modulus was investigated by measuring the behaviour of these properties due to the variation of temperature. Also, the characteristics of strength and deformation of these rocks were examined through high-temperature triaxial compression tests with varing temperatures and confining pressures. Important results obtained are as follows: In high temperature tests, the uniaxial compressive strength and Yong's modulus of Tonalite showed a sligth increase at a temperature up to 300$^{\circ}C$ and a sharp decrease beyond 300$^{\circ}C$, and the tensile strength showed a linear decrease with increasing heating-temperature. In high-temperature triaxial compression test, both the failure stress and Young's modulus of Tonalite increased with the increase of confining pressure at constant heating-temperature, and the failure stress decreased at 100$^{\circ}C$ but increased at 200$^{\circ}C$ under a constant confining pressure. In low temperature tests, the uniaxial compressive and tensile strengths and Young's modulus of these rocks increased as the cooling-temperature is reduced. Also, the uniaxial compressive and tensile strengths of wet rock specimens are less than those of dry rock specimens.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.9 s.252
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• pp.1110-1115
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• 2006

Cold expansion of fastener holes has been successfully used for many years to impart beneficial compressive residual stresses. Beneficial compressive residual stress of fastener hole that has been cold expanded before is reduced by using of materials for a long time. As a result, fatigue life of material is reduced. So, compressive residual stresses of material have to regenerate by re-cold expansion method. In this paper, it was carried out a finite element analysis about variation of residual stress due to tensile stress and residual stress distribution that was regenerated by re-cold expansion method in the fastener hole. Here, a diversity tensile stress was used. Also, it was performed a finite element analysis according to cold expansion rate of re cold expansion in order to obtain a beneficial compressive residual stress.

• Korean Journal of Metals and Materials
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• v.46 no.5
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• pp.283-288
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• 2008

We observed the in-situ stress behavior of Cu and Ag thin films during deposition using a thermal evaporation method. Multi-beam curvature measurement system was used to monitor the evolution of in-situ stress in Cu and Ag thin films on 100 Si(100) substrates. The measured curvature was converted to film stress using Stoney formula. To investigate the effects of the deposition rates on the stress evolution in Cu and Ag thin films, Cu and Ag films were deposited at rates ranging from 0.1 to $3.0{\AA}/s$ for Cu and from 0.5 to $4.0{\AA}/s$ for Ag. Both Cu and Ag films showed a unique three stress stages, such as 'initial compressive', 'a tensile maximum' and followed by 'incremental compressive' stress. For both Cu and Ag films, there is no remarkable effect of deposition rate on the thickness and average stress at the tensile maximum. There is, however, a definite decrease in the incremental compressive stress with increasing deposition rate.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.132-139
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• 1997

The strengthening mechanism of short fiber or whisker reinforced metal matrix composites has been studied by a continuum mechanics treatment utilizing finite element analysis (FEM). To assess the tensile and compressive constitutive responses, a constraint-unconstraint comparative study based on stree-strain hysteresis loop has been performed. For analysis procedures, the aligned axisymmetric single fiber model and the stress grouping technique have been implemented to evaluate the domain-based field quantities. Results indicated that the development of significant triaxial stresses within the matrix both for the tensile and compressive loading, due to the constraint imposed by reinforcements, provides and important contribution to strengthening. It was also found that fiber stresses are not only sensitive to the fiber/fiber interaction effects but also substantially contribute to the composite strengthening both for the tensile and compressive loading.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1690-1692
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• 2000

The principle of crimping connection is to produce a compressive connection force between terminal and cores(wire conductor). Compressive connection force is produced by pushing each other on that stress(crimping force) of barrel by restored elastic strain after plastic deformation and the expansion force of cores' elastic stress. And resistance and tension force between terminal and cores are determined according to the condition of compressive connection force. In this study, we've found out that the adaptive height which has maximum tensile force by measuring a tensile force with a height of terminal.

• Korean Journal of Materials Research
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• v.1 no.1
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• pp.46-53
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• 1991

The stress of PSG (Phosphosilicate glass), USG (Undoped-silicate grass) and SiN films, which are mainly used as passivation layers in semiconductor memory devices, deposited by CVD methods has been studied as a function of film thickness and holding time in air. The stress of the PSG film or the USG film is increased in tensile state with increasing film thickness. On the other hand the stress level of the SiN film in compressive stress does not change as film thickness changes. The stress of PSG film shows the drastic change from the tensile stress to the compressive stress after the film is left 2 days in air. FTIR spectra indicated that the stress variation was due to the penetration of water molecule. It looks possible to recover the stress of about $2.5{\times}{10^9}dyne/cm^2$ by annealing treatment at $300^{\circ}C$ for 20min. The total stress of multi-layered films having the PSG film is determined mainly by the stress variation of PSG layer with holding time. The total stress of multi-layered film appears to have a functional relationship with the stress in the thickness of each film. The resistance against stress-migration of sputtered Al line increases with increasing the tensile stress for the PSG film or the USG film.

• The korean journal of orthodontics
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• v.26 no.3
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• pp.291-299
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• 1996

Orthodontic force is a mechanical stress controlling both of tooth movement and skeletal growth. The mechanical stress stimulate bone cells that may exert some influence on bone remodeling. The purpose of this study was to evaluate the difference in cellular activity depending on mechanical stresses such as compressive and tensile force by determining the alkaline phosphatase(ALP) activity. A clonal osteogenic cell line MC3T3-E1 was seeded into a 24-well plate($2{\times}10^4/well$). At the confluent phase, a continuous compressive hydrostatic pressure($25g/cm^2$, $300g/cm^2$) and continuous tensile hydrostatic pressure($-25g/cm^2$, $-300g/cm^2$) were applied for 4, 6, 10, 14, 18, 20 days respectively by a diaphgragm pump. At the end of the stimulation period, cell layers were prepared for ALP activity assay. The ALP activity of the compressive group increased more than that of the tensile group at same force magnitude, whereas the cells responded to a similar pattern regardless of the type of mechanical stress The ALP activity of the compressive and tensile group turned into the level of the control group as the length of time increased. These results indicated that a mechanical stress may be more effective on cellular activity during active cellular proliferation and differentiation periods. The time to achieve maximum ALP activity was delayed as the mechanical stress increased in both the compressive and the tensile group. Accordingly, the magnitude of the stress rather than the type of mechanical stress may have more influence on cellular activity.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.787-795
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• 2003

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as seismic loading are required to provide appropriate safety assessment to these mechanical structures. The Split Hopkinson Pressure Bar (SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate loading conditions. In this paper, dynamic deformation behaviors of the aluminum alloys such as A12024-T4, A1606 IT-6 and A17075-T6 under both high strain rate compressive and tensile loading conditions are determined using the SHPB technique.