• Transactions of the Korean Society of Mechanical Engineers
• /
• v.5 no.2
• /
• pp.110-121
• /
• 1981

In order to study on the fracture behavior and the fracture thoughness of combined structure, the specimens, structural steel (SM28C) and 6:4 brass are annealed for ductility and investigated for the befavior of fracture and the absorbed energy at the variation of the impact velocity. The results obtained by this study are as follows: (1)The maximum load increases with the impact velocity, but in the condition of constant impact velocity it decreases as the ductility increases. (2)The absorbed energy increases with the impact velocity, but in the condition of constant impact velocity it is constant as the ductility increases. (3)In the case of the combined structure of peralite and ferrite, the microcracks initiates and propagates mainly in the ferrite structure intergranular in accompany with the slip, and the slip concentration phenomena occur in the boundary of pearlite structure However, in case of the combined structure of .alpha. and ..betha. phase, the microcracks initiates and propagares mainly in the .alpha. phase intergranularly, and slip concentration phenomena not ocur in the boundary of .betha. phase.

• Journal of the Korean Society of Industry Convergence
• /
• v.9 no.1
• /
• pp.21-27
• /
• 2006

The laminar burning velocity was measured using a spherical combustion bomb with central ignition. Mixtures with equivalence ratio between 0.6 and 1.2, were tested. The computation was carried out for the burning velocity using premix code of Chemkin program under the unburned gas pressure of 0.5bar-30bar and temperature of 300K-700K at ${\Phi}1.0$. The results showed little difference between these two methods. The burning velocity was decreased by increasing the pressure and increased by increasing the temperature. The burning velocity was predicted by using the following equations $$S_L(m/s) = S_{st}(T/300)^{1.85}(P)^{-0.45}$$ $$(0.5bar{\leq}P{\leq}30bar,\;300K{\leq}T{\leq}700K)$$).

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.1
• /
• pp.9-16
• /
• 2002

The particles velocity in the instantaneous flow field and velocity change of particles along the jet centerline for various particle diameter in a circular turbulent impingement jet are investigated by using particle image velocimetry(PIV) and an equation of particle motion simplified by terms of inertia forces, drag and gravitational force. The jet Reynolds number was 3300 and 8700, and glass beads of 30,58 and 100$\mu$m in diameter were used. The PIV results show that the direction and size of velocity depends not only on the number density of particle but also on the particle momentum. The results obtained form calculation suggest that the particle velocity near the first impingement region deviated from local air velocity, which accords well with the PIV results. The rebound height of particle increase with the particle diameter. In the second-impingement, particle velocities increased sluggishly with Re=3300 but particle velocities uniformed with Re=8700 in stagnation region.

• Journal of KSNVE
• /
• v.10 no.2
• /
• pp.221-228
• /
• 2000

In this paper, analytical study is performed to reduce residual vibration in seeking mode of optical pick-up. The conditions for acceleration adn deceleration time in trapezoidal velocity profile to reduce residual vibration are derived for undamped vibration system. To verify the validity of conditiosn two example studies are carried out. Numerical and experimental implementations for flexible arm system attached to moving part show that residual vibration is effectively reduced by calculated velocity profile. In addition, simulation study for optical pick-up reveals that by changing natural frequency to resonance frequency the conditions derived assuming undamped system can be applied to obtain velocity profile for minimum residual energy in damped vibration system.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.11 no.2
• /
• pp.22-31
• /
• 1991

Various types of ultrasonic techniques have been used for the estimation of compressive strength of concrete structures. However, conventional ultrasonic velocity method using only longitudial wave cannot be determined the compressive strength of concrete structures with accuracy. In this paper, by using the introduction of multiple parameter, e. g. velocity of shear wave, velocity of longitudinal wave, attenuation coefficient of shear wave, attenuation coefficient of longitudinal wave, combination condition, age and preservation method, multiple regression analysis method was applied to the determination of compressive strength of concrete structures. The experimental results show that velocity of shear wave can be estimated compressive strength of concrete with more accuracy compared with the velocity of longitudinal wave, accuracy of estimated error range of compressive strength of concrete structures can be enhanced within the range of ${\pm}$10% approximately.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.766-771
• /
• 2005

To compare blasting vibration at blasting construction field in urban area, the vibration level (dB(V)) and vibration velocity (cm/sec) on the ground and the structure of buildings due to the differences of the measuring sites from the blasting source is investigated and the difference between the measured vertical vibration level and the calculated vibration level by using vibration velocity PVS and the correlation between vibration velocity and vibration level and is studied in the thesis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.356-359
• /
• 2007

In this paper, the stability of a rotating cantilever pipe conveying fluid with a crack is investigated by the numerical method. That is, the influences of the rotating angular velocity, mass ratio and crack severity on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating pipe are derived using the Euler beam theory and the Lagrange's equation. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. Generally, the critical flow velocity for flutter is proportional to the angular velocity and the depth of crack. Also, the critical flow velocity and stability maps of the rotating pipe system as a function of mass ratio for the changing each parameter are obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2008.11a
• /
• pp.681-686
• /
• 2008

In this paper, we estimated the degree of pipe thinning by using two accelerometers. It uses measured velocity of flexural wave traveling along the pipes. If the thickness of the wall decreases because of pipe thinning, flexural stiffness of the pipes decreases and accordingly, traveling velocity of flexural wave decreases. Thus, if we install two vibration sensors outside of the pipes and measures traveling velocity of flexural waves regularly, we can estimate and monitor the degree of pipe thinning quickly. In order to test the method we experimented with pipes, and get the result that group velocity varies according to the degree of pipe thinning. It verified this method can be used to monitor the pipe thinning.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.1047-1050
• /
• 2002

In this paper, grinding characteristics of cylindrical plunge grinding in 200m/sec of grinding velocity was investigated by use of vitrified CBN wheel. From the experimental result, it was convinced that grinding power is decreased 2.5times and grinding efficiency is heightened 3times more according to increasing wheel velocity 80m/sec to 200m/sec And also, be expected to improvement of surface roughness and roundness by increasing the wheel velocity.

• Journal of Korean Society of Water and Wastewater
• /
• v.24 no.2
• /
• pp.231-236
• /
• 2010

A compressible media filtration process with synthetic fiber media was studied for combined sewer overflows (CSOs) treatment. Since the operation performance of fiber media filtration was dependent on the pattern of CSOs, the flow rate of CSOs was investigated and it was characterized by a big fluctuation. Thus, in this study, the fiber media filtration process was tested with wide range of filtration velocity. The removal efficiency was proportion to the increase in compressibility. As the filtration velocity was increased, the treatment efficiency was decreased and consequently leveled off when the velocity exceeded 750 $m^3/m^2$/d. An exponential equation was introduced to express the relationship between the removal efficiency and up-flow velocity. At columm test, six repetition of filtration and backwash cycle did not after the filtering velocity under the constant pressure condition.