• Nuclear Engineering and Technology
• /
• v.41 no.3
• /
• pp.355-364
• /
• 2009

Circular plates with holes are extensively used in mechanical components. The existence of a hole in a circular plate results in a significant change in the natural frequencies and mode shapes of the structure. Especially if the hole is located eccentrically, the vibration behavior of these structures is expected to deviate significantly from that of a plate with a concentric hole. In addition, if the plate is in contact with or submerged in fluid, the situation is more complex. Therefore, in this study, an analytical method to determine the modal characteristics of a plate submerged in fluid is developed based on the finite Fourier-Bessel series expansion and Rayleigh-Ritz method and is verified by the finite element analysis using a commercial program. Also, the relationship between parameter variations and vibration modes is investigated. These results can be used as guidance for the modal analysis and damage detection of a circular plate with a hole.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.6 no.2
• /
• pp.34-41
• /
• 1997

The objective of this study is to investigate experimentally the frequency characteristics of the hole tones generated by a circular jet of low speed impinging on a plate with a round hole. The experimental results about the sound spectrum and the time wave of the hole tone are presented and discussed in relation with the hole type, the jet velocity and the distance of the nozzle-to-plate with a round hole. From the sound spectrum and time wave measurements, it is found that the hole tone is generated not only by an interaction of convected vortices with a round hole but also by a series of vortex shedding from jets passing through a hole. The hole tones generated by a feedback mechanism consist of many frequency stages and also have a hysteresis phenomenon like an edge tone. But the hole tones generated by a series of vortex shedding have nothing with the stage characteristics. The frequencies of hole tones are influenced by the jet velocity, the distance of the nozzle-to-plate with a round hole and the hole type.

• Nuclear Engineering and Technology
• /
• v.37 no.6
• /
• pp.557-564
• /
• 2005

Air-water countercurrent flow limitation at perforated plates with four holes was investigated in a vertical tank to see the effects of the plate thickness, the number of hole, and the diameter of the hole on the onset of CCFL. The thickness of plates was 1 cm and 4 cm, with a relatively large hole diameter of 5 cm. The collapsed water level formed on the perforated plate and its distribution in the upper plenum were measured. The gas flow rate in the multi-hole plate is relatively higher than one in the single tube because some of holes in the multi-hole plate provide a flow path fur liquid with less air-liquid resistance than in the single tube. The onset of CCFL occurred at nearly the same air flow rate regardless of the plate thickness. The negligible effect of the plate thickness on CCFL means that the flooding is initiated at the top of the plate rather than at its bottom. It turns out that $j_k$ and $K_k$ better fit the data than $H_k$ when hole diameter is greater than 2.86 cm. In our experimental ranges, the collapsed water levels at the onset of CCFL ranged from 7.5 cm to 10.5 cm. There was no three dimensional distribution of water level before and after the onset of CCFL.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.1
• /
• pp.29-37
• /
• 2012

This paper is concerned with the natural vibration characteristics of a rectangular plate with a rectangular hole in contact with the water. The addressed problem was solved by using the Rayleigh-Ritz method combined with the Green function method. This study presents the numerical approach, numerical results and experimental results. In addition, the validity of the approximate formula which mainly depends on the so-called non-dimensionalized added virtual mass incremental factor and the natural mode shape change due to the presence of the water were investigated. Experiments were also carried out to validate theoretical results. The theoretical results are in good agreement with the experimental results. It was found that the effect of a square hole on the natural frequencies of the square plate in contact with water is different from the effect of a square hole on the natural frequencies of the square plate in air and the approximate formula can predict lower natural frequencies in water with a good accuracy.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.6
• /
• pp.681-689
• /
• 2008

This paper is concerned with the free vibration analysis of a circular plate with an eccentric circular hole by the Independent coordinate coupling method(ICCM). It was proved in the previous study that the ICCM can accurately predict the natural frequencies and mode shapes of the annular plates and can also be used for the free vibration analysis of the simply-supported circular plate with an eccentric circular hole. In this study, the clamped and free boundary conditions were considered for the circular plate. The numerical results show that the ICCM can be used effectively for the free vibration problem of circular plate with an eccentric hole compared to the finite element method.

• Structural Engineering and Mechanics
• /
• v.36 no.6
• /
• pp.669-678
• /
• 2010

In general means, the stress concentration problem of elastic plate with a rectangular hole can be investigated by numerical methods, and only approximative results are derived. This paper deduces an analytical study of the stress concentration due to a rectangular hole in an elastic plate under bending loads. Base on classical elasticity theory and FEM applying the U-transformation technique, the uncoupled governing equations with 3-DOF are established, and the analytical displacement solutions of the finite element equations are derived in series form or double integral form. Therefore, the stress concentration factor can then be discussed easily and conveniently. For the plate subjected to unidirectional bending loads, the non-conforming plate bending element with four nodes and 12-DOF is taken as examples to demonstrate the application of the proposed method. The inner force distribution is obtained. The solutions are adequate for the condition when the hole is far away from the edges and the thin plate subjected to any transverse loadings.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.15 no.1
• /
• pp.1-7
• /
• 2006

A method of the volumetric error measurement and calibration of NC machine tools is studied using an artifact method. In this study, a hole-pate is designed and machined using stainless steel. We tested and applied the hole-plate artifact in a commercial CMM(Coordinate Measuring Machine), after calibration of the hole-plate using a precise CMM. It has been shown that not only the measurement of geometric error components but also the 2D length error calculation in a working volume is available using the hole-pate artifact method. The results of study can also be used in NC machine with touch probe as the same method in CMM.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2002.02a
• /
• pp.260-265
• /
• 2002

In micro hole punching process, it is very difficult to align punch with die hole. Misalignment can cause a falling-on in hole quality and breakage of punch and die. Micro punching using soft die plate without a die hole has a big advantage because it is not necessary to align punch with die hole and to consider die clearance. Soft die plates are made by polymers or hard rubbers which are softer than metals. In this study, several micro punching experiments are conducted. Micro punching test with some materials shows that micro hole punching is feasible with some soft die plates. Through the section shape obtained by mounting and polishing, the punched hole quality is measured and the shapes of burr and dome we studied.

• Structural Engineering and Mechanics
• /
• v.68 no.2
• /
• pp.261-275
• /
• 2018

A comprehensive study was provided to investigate the buckling behavior of the steel plates with and without through-thickness holes subjected to uniaxial compression using ABAQUS. The method was validated by the results reported in the literature. Using the critical stresses, the buckling coefficients ($K_c$) were calculated. The effects of inclusion of material nonlinearity, plate thickness (t), aspect ratio (AR), and initial imperfection on buckling resistance of the plate was studied. Besides, the effects of having the hole in the plate were also studied. The diameter of the hole was normalized by dividing by plate breadth and was given in the form of ${\alpha}$. Results showed that perforating one hole in the center of a plate increases the plate buckling resistance while the having two holes resulted in a decrease in the plate buckling resistance. The effects of hole eccentricity (Ecc) on the buckling resistance of the plate was studied. The position of the hole center was normalized by half of the plate breadth and length in X- and Y-directions, respectively. In this study, four cases of boundary conditions were considered, and the corresponding buckling behavior were studied combined with plate aspect ratio. It was observed that the boundary condition of the case I resulted in the highest buckling resistance. Finally, a comparison was made between the buckling behavior of the uniaxially and biaxially loaded plate. It was revealed that the buckling resistance of a biaxially loaded plate is lower half than half of that of the uniaxially loaded plate.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.812-815
• /
• 2002

This paper deals with the buckling and vibration analysis of plate with a hole. We knew that in this paper, as aspect ratio rises in design parameter, the buckling strength and the natural frequency of laminated composite plate decrease and as diameter of hole for width of plate rises, the buckling strength decrease but the natural frequency increase. Also this paper compared the CFRP laminated composit plate with the hybrid composite plate, and proposed that the hybrid composite plate is stronger than the CFRP composite plate.