• Structural Engineering and Mechanics
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• v.67 no.2
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• pp.131-142
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• 2018

The perfobond connector, composed of a steel plate with a number of holes, serves as a certain type of shear connector in steel and concrete composite structures. Depending on limits in hole distances and rib heights, various hole shapes including circular-hole and long-hole are alternatives for perfobond connectors. This study presented the results of tests performed on 72 push-out specimens with perfobond connectors. The purpose was to evaluate the shear strength of perfobond connectors with circular-hole and long-hole. The effects of various parameters were investigated, including the hole diameter, the hole length, the hole height, the concrete strength, the existence, diameter and strength of rebar in the hole, the thickness, height and distance of perfobond ribs, and the thickness of concrete slabs. On the basis of 132 push-out test results in references and in this study, an analytical model was proposed by regression analysis to predict the shear strength of perfobond connectors. The proposed equation agreed reasonably well with the experimental results of perfobond connectors with different hole shapes.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.574-578
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• 2003

The objective of this paper is to decide optimal location of pin-hole to minimize stress concenstation around hole in rotating disc. The focus of this investigation is to evaluate the effect of pin-hole for stress distribution around hole using optimum design technic and finite element analysis. Design variables are radial and angular location of pin-hole from center of hole, objective function is maximum stress around hole in rotating disc. We use first order method of optimization technic.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.362-365
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• 2005

The hub hole is usually formed with a flanging process followed by a blanking process of a ]tole. Since the hole is made by blanking, the blanked surface is so rough that the formability in the region is rather poor. The emerging task is to identify the formability of the blanked region in the forming simulation and to relate the criterion to the real forming process by experiments. In this paper, hole expansion tests are carried out with respect to various hole conditions to verify the hole condition effect on the hole expansion ratio. The hole of specimens is made by machining or punching. In the case of punching, two different punching clearances are used for making the hole. From the results of test, fracture mechanism of the hole expansion is explained.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.341-351
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• 2016

In this present work, the effect of hole shapes, orientation and hole arrangements on film cooling effectiveness has been carried out. For this work a flat plate has been considered for the computational model. Computational analysis of film cooling effectiveness using different hole shapes with no streamwise inclination has been carried out. Initially, the model with an inclination of $30^{\circ}$ has been verified with the experimental data. The validation results are well in agreement with the results taken from literature. Five different hole shapes viz. Cylindrical, Elliptic, Triangular, Semi-Cylindrical and Semi-Elliptic have been compared and validated over a wide range of blowing ratios. The blowing ratios ranged from 0.67 to 1.67. Later, orientation of holes have also been varied along with the number of rows and hole arrangements in rows. The performance of film cooling scheme has been given in terms of centerline and laterally averaged adiabatic effectiveness. Semi-elliptic hole utilizes half of the mass flow as in other hole shapes and gives nominal values of effectiveness. The triangular hole geometry shows higher values of effectiveness than other hole geometries. But when compared on the basis of effectiveness and coolant mass consumption, Semi-elliptic hole came out to give best results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.761-764
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• 2002

This paper deals with the stress concentration of the rotating disc in detail. We studied maximum stress of rotating disc with respect to the various parameter of circular hole such as position, size, number of the hole, then the mollified effect of maximum stress due to pin-hole around circular hole, using FEM, the results are as follows: 1. The more the number of circular hole and the further from the center, the maximum equivalent stress reduces. 2. When the pin-hole is located 60$^{\circ}$ from the x-axis, the maximum stress reduces significantly due to the effect of interference.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2475-2482
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• 2002

The measurement of residual stresses by the hole-drilling method has been commonly used to evaluate residual stresses in structural members. In this method, eccentricity can usually occur between the hole center and rosette gage center. In this study, the error due to the hole eccentricity is compensated using the neural network. The neural network has trained training examples of normalized eccentricity, eccentric direction and direction of maximum stress at eccentric case using backpropagation learning process. The trained neural network could compensated the error of measured residual stress in experiments with hole eccentricity. The proposed neural network is very useful for compensation of the error due to hole eccentricity in hole-drilling method.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.412-418
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• 2001

The measurement of residual stresses by the hole-drilling method has been commonly used to evaluate residual stresses in structural members. In this method, eccentricity can usually occur between the hole center and rosette gage center. In this study, the error due to the hole eccentricity is corrected using the neural network. The neural network has trained training examples of normalized eccentricity, eccentric direction and direction of maximum stress at eccentric case using backpropagation learning process. The trained neural network could corrected the error of measured residual stress in experiments with hole eccentricity. The proposed neural network is very useful for correction of the error due to hole eccentricity in hole-drilling method.

• Journal of Power System Engineering
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• v.12 no.5
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• pp.14-19
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• 2008

In order to meet stringent future emission regulations, especially to reduce Particulate Matter (PM) and NOX, stoichiometric diesel combustion technology with a piezo group-hole nozzle injector is being researched for reduction harmful emissions. A new nozzle layout, namely a group-hole nozzle, which has one group of small orifices with a wide spray included angle was investigated to improve the efficiency of stoichiometric diesel combustion. From this point of view, the group-hole nozzle suggested by Dense Co. is an attractive candidate method applicable to stoichiometric diesel combustion. The group-hole nozzle concept is to reduce the injector nozzle hole diameters without sacrificing spray penetration by closely locating two holes. Experimental studies have proven that the spray from group-hole nozzles have similar spray penetration to that of a single hole with equivalent overall nozzle hole area, but the spray drop sizes (SMD) are reduced, aiding vaporization and mixing.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.201-206
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• 2001

The hole-drilling method makes a little hole through the metal surface that has residual stress and measures the relieved stress with a strain gage. It is used widely in measuring the residual stress of surfaces. In this method, the inclined hole is one of the source of error. This paper presents a finite element analysis of influence of the inclined hole for the uniaxial residual stress field. The stress differences between measured and applied residual stress increase proportionally to inclined angle of the hole. The correction equations which easily obtain the residual stress taking account of the inclined angle and direction are derived. The measurement error of stress due to the inclined hole can be reduced to around 1% through this study.

• Transactions of Materials Processing
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• v.30 no.2
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• pp.74-82
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• 2021

Stretch-flangeability, which is the ability of sheet steels to be deformed into complex shapes, is a critical formability property in automobile body parts. In this study, the center-hole for hole expansion test, which is normally used to evaluate the stretch-flangeability of sheet steels, was prepared by both punching and electrical discharge machining (EDM) methods. Hole expansion ratio (HER) of punched hole was far lower than the HER of EDM drilled hole because of damage/crack in hole-edge due to punching process. The effect of hole-edge condition on HER was quantified by mechanical, fractographic and geometric factors. Based on these factors, the empirical equation used to determine HER for various sheet steels was derived using non-linear regression.