• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.937-944
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• 2013

This paper describes an improved model that can be used for configuring a non-contact pneumatic head to handle a large sheet of glass. The cylindrical head model is of a large size (70 mm). It operates on vortex flow, which can simultaneously generate suction and repulsion over the flat object's surface. The head allows for the minimal non-contact lifting of objects weighing over 3N by using reference conditions (working pressure and head dimensions). Additionally, a functional flow-guide is applied for inducing a developing tangential vortex flow to increase suction and repulsion to the reference head. The cylindrical flow-guide is associated with relatively low tangential velocity. The improved model generates greater lifting force than the reference model, as verified experimentally.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.214-219
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• 2002

As the tangential flow inside the clearance of tribe elements such as bearings and seals is increased as the shaft speed increases, the system stability will be decreased due to the increment of the instability parameter. To reduce the tangential flow inside the clearance of the balance sleeve, anti-swirl injection mechanism is applied. The balance sleeve is used in resisting the axial force induced by impeller in high pressure multi-stage pump. In this paper, total three cases are experimentally investigated; original balance steeve, anti-swirl injection balance steeve with 0 axial degree and anti-swirl injection balance sleeve with 30 axial degree. Experiments are focused in the comparison of vibration level and leakage flow rate. The results clearly shows that the anti-swirl injection balance sleeve with 0 axial degree improves the vibration characteristics. However, the anti-swirl injection balance sleeve with 30 degree aggravates the vibration characteristics. In the standpoint of leakage performance, both anti-swirl injection balance sleeves show the better result than the original balance sleeve.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.8
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• pp.632-638
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• 2002

As the tangential flow inside the clearance of tribo elements such as bearings and seals is increased as the shaft speed increases, the system stability will be decreased due to the increment of the instability parameter. To reduce the tangential flow inside the clearance of the balance sleeve, anti-swirl injection mechanism is applied. The balance sleeve is used in resisting the axial force induced by impeller in high pressure multi-stage pump. In this paper, total three cases are experimentally investigated; original balance sleeve, anti-swirl injection balance sleeve with 0 axial degree and anti-swirl injection balance sleeve with 30 axial degree. Experiments are focused in the comparison of vibration level and leakage flow rate. The results clearly shows that the anti-swirl injection balance sleeve with 0 axial degree improves the vibration characteristics. However, the anti-swirl injection balance sleeve with 30 degree aggravates the vibration characteristics. In the standpoint of leakage performance, both anti-swirl injection balance sleeves show the better result than the original balance sleeve.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.4
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• pp.673-678
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• 1997

Stress wave propagations in an elastic half space to a normal point force of ramp type in time are analyzed. The governing equations are transformed by applying the Laplace and Hankel transforms with respect to time and radial distance. The inversion of Laplace transforms are performed by employing the Cagniard-de Hoop method, where the Rayleigh waves at surface are obtained by including the residue terms. The stress waves computed at the location very cose to the surface are shown to be almost identical to the surface waves obtained by the residue method except the Rayleigh wavefront. It is found that at the surface, the stresses are dominated by the Rayleigh waves, whose amplitudes increase linearly with time when time is very large. It is also found that in the interior part, the radial stress has a logarithmic singularity at the shear wavefront, while tangential stress shows no singularity.

• Journal of Korean Society of Steel Construction
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• v.17 no.6 s.79
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• pp.699-705
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• 2005

This paper investigates critical loads of tapered cantilever columns with a tip mass, subjected to a follower force. The linearly tapered solid rectangular cross-sections are adopted as the column taper. The differential equation governing free vibrations of such columns, also called Beck's columns, is derived using the Bernoulli-Euler beam theory. Both divergence and flutter critical loads are calculated from the load-frequency curves that are obtained by solving the differential equation. The critical loads are presented as functions of various non-dimensional system parameters, namely, the taper type, the subtangential parameter, and the mass ratio.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.1010-1017
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• 2013

Two-axial electrodynamic forces generated on a conductive plate by a partially shielded magnet wheel are strongly coupled through the rotational speed of the wheel. To control the spatial position of the plate using magnet wheels, the forces should be handled independently. Thus, three methods are proposed in this paper. First, considering that a relative ratio between two forces is independent of the length of the air-gap from the top of the wheel, it is possible to indirectly control the in-plane position of the plate using only the normal forces. In doing so, the control inputs for in-plane motion are converted into the target positions for out-of-plane motion. Second, the tangential direction of the open area of the shield plate and the rotational speed of the wheel become the new control variables. Third, the absolute magnitude of the open area is varied, instead of rotating the open area. The forces are determined simply by using a linear controller, and the relative ratio between the forces creates a unique wheel speed. The above methods were verified experimentally.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.41-46
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• 2017

Productivity improvement and cost reduction in the aircraft industry have become major industrial objectives, and improving productivity by reducing machining time has become a key focus. When numerical cutting code is created by CAM software, such as CATIA or UG-NX, it is impossible to control machining feed speed using cutting force changes depending on the machining tool path. However, machining an aircraft engine part from difficult material, such as Inconel 718, takes a long time, and tool chipping or breakage often occurs from forcing the machining path too quickly. This study investigated and verified the reliability of the AdvantEdge production module (PM)using cutting power tests. In particular, diffuser and diffuser case parts were considered, comparing cutting power and machining time using AdvantEdge PM and CATIA.

• Journal of Magnetics
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• v.20 no.2
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• pp.186-192
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• 2015

This paper describes the electromagnetic and mechanical characteristics of coaxial magnetic gear (CMG) with a low gear ratio. The analysis models are restricted to a CMG with a gear ratio of less than 2. The electromagnetic characteristics including transmitted torque and iron losses are presented according to the variation of the gear ratio. The pole pairs of high speed rotor are chosen as 6, 8 and 10 by considering the torque capability. As the gear ratio approaches 1, both iron losses on the ferromagnetic materials and eddy current losses on the rotor permanent magnets are increased. The radial and tangential forces on the modulating pieces are calculated using the Maxwell stress tensor. When the maximum force is exerted on the modulating pieces, the mechanical characteristics including stress and deformation are derived by structural analysis. In CMG models with a low gear ratio, the maximum radial force acting on modulating pieces is larger than that in CMG models with a high gear ratio, and the normal stress and normal deformation are increased in a CMG with a low gear ratio. Therefore, modulating pieces should be designed to withstand larger radial forces in CMG with a low gear ratio compared to CMG with a high gear ratio.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.97-103
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• 2018

Force is a crucial element to be measured in various industries, especially the machine tool industry. Mega units of force are required in fields such as the heavy and ship industries. Micro/nano units of force are required for microparticles. The detection of force generates a physical transformation due to the force imposed from the outside, atlrnd electrical voltage signals are obtained from the system. For the detection of force, an octagonal ring load cell based on circular ring theory is designed and produced. To design the octagonal strain ring, theoretical values with data from the ANSYS program are compared to determine the size of the octagonal strain ring. An octagonal strain ring of the chosen size is made with the SCM415 material. The strain gauges are attached to the octagonal strain ring, designed to construct a full Wheatstone bridge. The LabVIEW program is used to measure the data, and strain values are found. With the octagonal ring load cell completed in this way, experiments are conducted by imposing forces on the tangential axis and radial axis. Experiments are performed to verify if the octagonal ring load cell conducts measurements properly, and theoretical values are analyzed to find any differences. The data will later be used in further research to develop a machine-tool dynamometer.

• Journal of Electrical Engineering and Technology
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• v.3 no.1
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• pp.60-67
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• 2008

The vibrations and noise origin in electric material is due to several coupled physical phenomena. The revolving electric machine complete modeling is complex; it does not allow simple parametric machine structure studies for various operation modes. This work presents a simple electromagnetic model which makes possible the machine principal parts flow estimation from flux density. Special interest is given in determining Switched Reluctance Machine (S.R.M) radial acceleration in accordance with the current supply. Our focus will be only on the magnetic origin efforts that are dominating in the S.R.M. The efforts calculation versus the current is presented in the case of a machine with a linearized rate. These efforts are considered as a tangential force producing the torque and a radial force that generates no torque. The application is realized on a 6/4 low power S.R.M type (6 stator teeth and 4 teeth rotor). The mechanical response is substituted in a transfer function. The model takes account of the power supply of the machine, the relation between the current supply and the efforts as well as the vibratory response of the machine to these efforts. Finally, the model is validated by comparison with similar experimental results within the framework of the definite assumptions.