• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.485-490
• /
• 2000

The effect of curvature, rotation, variable cross-section can make very complex flow pattern in turbo-machinery such as Pumps, compressors, turbines, In this study of turbulent flow characteristics rotating $90^{\circ}$ curved duct under a Plane rate of strain condition is computationally analyzed. The objective of this study is to understand the complex turbulent flow phenomena in turbo-machinery passage by analyzing the modeled rotating $90^{\circ}$ curved duct flow. RSM(Reynolds Stress Model) was employed for the turbulence modeling of Reynolds stress in momentum equations proposed by Shin(1995). The three dimensional computational code which adopts RSM for trubulence modeling was newly developed for the generalized curvilinear coordinate.

• Journal of the Korea Society for Simulation
• /
• v.30 no.1
• /
• pp.127-137
• /
• 2021

The method of utilizing the strain and vibration values of rails is primarily used to diagnose the condition of wheels and railroad facilities. The dynamic load is measured under the assumption that the strain of the rail and the load of the railroad vehicle are proportional. Wheel condition is measured under the assumption that the magnitude of the defect and the magnitude of the rail vibration are proportional. However, environmental factors affecting the strain and vibration of the rail such as vehicle speed, wheel load, climate, and track conditions are not reflected, many errors occur depending on the measurement conditions. In this study, the effect of track distortion, which is a major indicator of the track condition among the environmental factors that affect the strain and vibration of the rail, on the strain and vibration of the rail, was examined through dynamic simulation. As a measure to reduce the measurement deviation, the effect of securing additional measurement points was analyzed.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.395-400
• /
• 2001

The Split Hopkinson Pressure Bar(SHPB) technique, a special experimental apparatus, has been used to obtain the material behavior under high strain rate loading condition. In this paper, dynamic deformation behaviors of the PMMA under high strain rate tensile loading are determined using SHPB technique.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.04a
• /
• pp.355-360
• /
• 1996

When the operational strains of a structure can not be directly measured in order to predict the life of the structure due to the problem of the attachment, those must be obtained indirectly. Since the displacement and the strain are interrelated, the strain can be predicted from the measured displacement and displacement-strain transformation matrix. The transformation matrix is dependent on the boundary condition, unfortunately, and it is also difficult to know exactly that of the operational system. In this study, for the structure with arbitrary boundary condition under the operation, the approximate method is proposed in order to predict the operational strains using the transformation matrix obtained by using free boundary conditions. And the method is applied to predict the strains of leads of surface mount component under the vibration of the printed circuit board.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.03a
• /
• pp.286-300
• /
• 2006

Nonlinear cross-anisotropic properties of soil is critical for exact numerical simulation. Theoretically, initial cross-anisotropic properties can be evaluated from triaxial tests with bender element tests, and nonlinear cross-anisotropic properties over initial strain level cannot be evaluated from triaxial tests. In this study, a supposed condition among nonlinear cross-anisotropic properties is suggested to calculate nonlinear cross-anisotropic properties from triaxial tests. Maximum strain and incremental strain energy are applied to combine triaxial test results and theoretical normalized shear modulus curve, respectively Based on combined results, nonlinear cross-anisotropic properties are calculated. Numerical simulation for triaxial tests Is carried out to verify the applicability of the supposed condition with calculated cross-anisotropic properties and simplified nonlinear cross-anisotropic model.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.10a
• /
• pp.180-183
• /
• 2004

Superplastic formability depends on flow parameters such as temperature, strain rate, strain and stress, microstructures. Usually, superplastic properties of materials are characterized with using a uni-axial tension testing. However, superplastic sheet is formed under mutiaxial loading condition in most forming practices. In the present study, superplastic characteristics of A15083 alloys were determined with using both a uni-axial and biaxial bulging tests. Specially, cone-type die was used to achieve constant strain rate under constant pressure condition. Even though constant strain rate under a certain pressure was achieved only approximately, a cone-type bulging test was found to be quite beneficial to get a multiaxial formability of superplastic materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.692-695
• /
• 1999

This paper presents annealing characteristics of CrN thin-film strain gauges, which were deposited on glass by DC reactive magnetron sputtering in an argon-nitrogen atmosphere)Ar-(5-~25%)$N_2$. The physical and electrical characteristics of these films investigated with the thickness range 3500$\AA$ of CrN thin films, annealing temperature (100~30$0^{\circ}C$) and annealing time (24-72hr) . The optimized condition of CrN thin-film strain gauges were thickness range of 3500$\AA$ and annealing condition(30$0^{\circ}C$ , 48hr) in Ar-10%$N_2$ deposition atmosphere. Under optimum conditions, the CrN thin-films for strain gauge is obtained a high resistivity, $\rho$=1147.65$\Omega$cm a low temperature coefficient of 11.17. And change in resistance after annealing for the CrN thin film were quitely linear and stable.

• Korean Journal of Applied Biomechanics
• /
• v.15 no.1
• /
• pp.155-176
• /
• 2005

There is some evidence that one of major factors to produce plantar fasciitis depends on the magnitude of the foot arch strain. The orthotics that can reduce the foot arch strain during locomotion may be effective to prevent or treat plantar fasciitis. Therefore, the purpose of this study was to investigate the effect of control condition and three types of foot orthotics on 3-dimensional foot arch strain that can produce plantar fasciitis during treadmill level and uphill walking and running. Sixteen male subjects are recruited and the arch length and height strain according to three types of foot orthotics with respect to control condition were measured by using two digital video cameras. The first hypothesis which the comfort of foot orthotics would be increased from arch pad, half length orthotics to full length orthotics was mostly accepted. It suggested that the types of the foot orthotics could be properly prescribed according foot regions that is pain or abnormal. The second hypothesis which the foot arch strain can be reduced by foot orthotics during level heel-toe walking and running and the third hypothesis which the foot arch strain can be reduced by foot orthotics during uphill heel-toe walking and running were rejected. The foot arch length and height strain during walking and running showed small and subject-specific characteristics and could not be optimal biomechanical variable to prove the overall comfort. The forth hypothesis which the foot arch strain cannot be reduced by foot orthotics during uphill toe walking and running was accepted. With the foot arch length and height strain during uphill toe walking and running the windlass mechanism suggested by Hicks can be explained successfully and excessive uphill toe walking and running can be one of cause of plantar fasciitis. The dynamic investigation on the foot arch such as walking and running should be carefully observed with integrated insights considering ligaments and foot bones as well as plantar fascia, extrinsic muscles and tendons, and intrinsic muscles and tendons.

• The Korean Journal of Pesticide Science
• /
• v.13 no.4
• /
• pp.262-266
• /
• 2009

Plant growth-promoting rhizobacteria (PGPR) are beneficial native soil bacteria that colonize plant roots and result in increased plant growth. The objective of this study was to determine the plant growth promotion in canola plants by selected PGPR strain 13-1 under low temperature condition. The seed treatment of strain 13-1 was enhanced plant height and root elongation on canola plant at low temperature condition. This result determined that a selected strain of PGPR can enhance plant growth and root propagation under extremely low temperature conditions. Thus, this PGPR strain extends their role on plant growth promotion on canola until low temperature condition for practical applications.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.1
• /
• pp.77-92
• /
• 2003

A set of standard triaxial testing was performed to identify underlying physical processes and inherent limitations in the determination of critical state parameters in sandy soils. The experimental test results showed that the critical state friction angle for a given soil is constant regardless of drainage condition while the critical state line on the e-log p'space is significantly affected by drainage condition mainly because of insufficient strain attained in standard triaxial tests and strain localization effects in udrained tests. It appeared that the best method to determine critical state parameters in laboratory testing is to use homogeneous loose specimens under drained shear condition. In addition, a reference state parameter was suggested to design tests that will avoid dilatancy or strain localization effects in drained tests.