• Advanced Composite Materials
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• 제18권1호
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• pp.43-59
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• 2009

The current study assessed the effect of a bolt hole on tensile fatigue properties of CFRP laminates. Two specimens, i.e. $[(0/90)_3]S$, $[(0/45/90/-45)_2]_S$, were analyzed using a finite element method and were experimentally tested for cases, both with and without a hole, whose diameter corresponded to 0.12 times the specimen width. Delamination positions predicted by a 3-dimensional static finite element analysis were matched well to those observed by an ultrasonic imaging system in the middle of fatigue test. A hole whose diameter corresponds to 0.12 times the specimen width caused the fatigue strength to decrease by 9% and 11% under 5 Hz loading frequency, and by 22% and 25% under 10 Hz loading frequency for $[(0/90)_3]_S$ and $[(0/45/90/-45)_2]_S$, respectively. Because the decrease in sectional area due to the hole was normalized in calculation of the tensile strength, a stress concentration around the hole is believed to induce the strength degradation of fatigue specimens. From the finite element analyses, the stress concentration factor around a hole was expected as 8.8 and 9.5 for $[(0/90)_3]_S$ and $[(0/45/90/-45)_2]_S$, respectively.

• 한국안전학회지
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• 제21권1호
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• pp.96-104
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• 2006

This study is to find out how the sawdust-mixed RC beam with holes acts compared to two case of normal one with sawdust without hole, without sawdust. variables are ED3H1, ED3H2, ED3H1UB, ED3H2L, ED5H1, ED5H1UB, ED5H2, ED5H2L, Normal with sawdust PLA without sawdust. All sand, aggregate, cement are in accordance with KS. mixing design is also in accordance with KS and done at D remicon company in order to decrease any error in mixing manually. ED3H1 showed 7tone of maximum load capacity having only minor tensile deformation around hole, compared to the center of the beam. ED5H2L showed almost same shape of tensile strain between hole area and center of two beam length, while having 9.5 tone load capacity, incase of two holes being in the longitudinal axis. But ED5H2 in case of two holes being in same forcing direction showed 8.4tone of load capacity while having minor tensile chape around hole and normal tensile shape in the center of beam length. Two diameter 3cm hole in longitudinal axis give more effective behavior than the other case, practically. Capacity decrease between 5cm and 3cm in eccentric position form the longitudinal axis is less than percents. There is minor capacity difference between hole diameter 3cm hole, but 13tone difference of load capacity between hole diameter 5cm.

• 한국기계가공학회지
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• 제19권6호
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• pp.49-54
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• 2020

The purpose of this study is to investigate the effects of the change in the spindle speed and the feed rate on the diameter change of a hole using a boring cutter for the internal boring process of AL6061-T4 alloys. The experimental results are quantitatively analyzed by applying the factor analysis and the response surface analysis of the experimental design method. The tendency of the diameter change according to the change in the spindle speed and feed level is also evaluated. During the internal boring process of AL6061-T4 alloys, the main factor affecting the diameter change is the spindle speed in which the diameter decreases as the number of revolutions increases. In addition, the diameter tends to increase as the feed is increased; however, as the number of spindle revolutions increases, the influence of the feed decreases.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.185-192
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• 1999

It had found that, as a result of cross-hole tonic logging test, concrete was not filled partially within the bottom 2.0 m of the large diameter (Ø= 2,500mm) rock socketed pile, MP20-P11(socket diameter (Ø= 2,200mm), which was a pile among piles group supporting a pier of Kwangan Grand Bridge. The pile was repaired by the combined cement grout injected through the pipes for the cross-hole sonic logging test and the bore holes for core samples. A month after the cement grouting, repairing was checked by coring and cross-hole sonic logging then 3 times of grouting and 2 times of coring were, in turns, peformed, then repairing was completed successfully. The vertical compressive capacity of the repaired large diameter socketed pile was evaluated by several formulas and software ROCKET, and was more conservative than design load (1,882 ton) of MP20-P11. It is expected that, in the case of the battered socketed piles, it could be more reasonable to analyze the behaviors of a battered pile using 3-D model. A 3-D analysis will be peformed in the future study.

• 한국자동차공학회논문집
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• 제9권3호
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• pp.27-34
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• 2001

This experimental study is to investigate the intermittent spray characteristics of the multi-hole diesel nozzle with a 2-spring nozzle holder. Without changing the total orifice exit area, its hole number varied from 3($d_n=0.42mm$) to 8($d_n$=0.25mm). Through the use of the 2-D PDPA(phase Doppler particle analyzer), the droplet diameter and the velocity of the diesel spray injected intermittently from the multi-hole nozzle into the still ambient were measured. And the calculations of time-resolved diameters, SMD and AMD were made. The results can be summarized as follows. The spray of the multi-hole nozzle consisted of three parts. These are the leading edge, the central part and the trailing edge. And most of droplets produced at the trailing edge of spray. In the spray flow field, the measuring position which represented the intermittent spray characteristics well was near the nozzle tip. But at the downstream of the spray, its characteristics disappeared, and spray behavior showed a quasi steady state regardless of the time evolution of the spray. The overall mean SMD of the spray increased with the spray development, and showed their maximum value near 1.5ms regardless of hole number.

• 한국생산제조학회지
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• 제7권4호
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• pp.56-63
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• 1998

The purpose of this is to analyze experimentally how the change of cutting speed have effects on hole over size of cutting hole, surface roughness of workpiece and roundness during the deep hole machining of SM55C with solid BTA drill using BTA drilling system. Conclusion reached is as follows. (1) The diameter was expanded for 25$\mu$m at the first section and then was reduced 0$\mu$m and 15$\mu$m respectively at the 10m and 20m section comparing to the diameter of tool with respect to the variation of cutting length at 70m/min of cutting speed. 0.15mm/rev of feed. (2) It was proved that roughness was below 8.67$\mu$m for the whole section of cutting length. (3) The roundness has been below 12$\mu$m. Regarding the polygon phenomenon, it has been proved that not only uneven best at 70m/min of cutting speed. 0.15mm/rev of feed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.746-752
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• 2000

A study on discharge characteristics of a rotating discharge hole is very important to enhance the performance of an induction motor which have external forced cooling system. The discharge characteristics of rotating discharge holes are influenced by rotating speed, length-to-diameter ratio, inlet shape of rotor holes, etc. An experimental study on the effect of chamfered inlet edge of rotor inlet part with various depth-to-diameter and inlet chamfered edge angle is conducted. Depth-to-diameter ratios range from 0 to 0.5 and inlet chamfered edge angle range from 0 to 60. As a result, there is an optimal design point of inlet chamfered edge depth. And the inlet edge angle far maximum discharge coefficient is influenced mainly by the rotating speed of discharge holes.

• 한국유체기계학회 논문집
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• 제17권6호
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• pp.115-122
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• 2014

The optimal design of the flow distributor is very important to ensure the structural integrity of the reactor system and their safe operation during some transient or accident conditions. In the present study, we numerically investigated the performance of a flow distributor in tank with different shape factors such as the total number of the holes, the pitch-to-hole diameter ratios (p/d), the diameter of the hole and the area ratios. These data will contribute to a design of the flow distributor.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.530-533
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• 2010

This paper presents numerical analysis and design optimization of various turbine blade cooling techniques with three-dimensional Reynolds-averaged Navier-Stokes(RANS) analysis. The fluid flow and heat transfer have been performed using ANSYS-CFX 11.0. A fan-shaped hole for film-cooling has been carried out to improve film-cooling effectiveness with the radial basis neural network method. The injection angle of hole, lateral expansion angle of hole and ratio of length-to-diameter of the hole are chosen as design variables and spatially averaged film-cooling effectiveness is considered as an objective function which is to be maximized. The impingement jet cooling has been performed to investigate heat transfer characteristic with geometry variables. Distance between jet nozzle exit and impingement plate, inclination of nozzle and aspect ratio of nozzle hole are considered as geometry variables. The area averaged Nusselt number is evaluated each geometry variables. A rotating rectangular channel with staggered array pin-fins has been investigated to increase heat transfer performance ad to decrease friction loss using KRG modeling. Two non-dimensional variables, the ratio of the eight diameter of the pin-fins and ratio of the spacing between the pin-fins to diameter of the pin-fins selected as design variables. A rotating rectangular channel with staggered dimples on opposite walls are formulated numerically to enhance heat transfer performance. The ratio of the dimple depth and dimple diameter are selected as geometry variables.

• 한국표면공학회지
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• 제35권5호
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• pp.295-304
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• 2002

In this study, the effect of the diameter and the number of barrel hole on the total area of barrel hole were calculated and analyzed. And the effects of applied current density, rotational speed of the barrel, size and number of barrel hole, and the volume of plating materials on the distribution of plating thickness were experimented and discussed by the barrel electroplating of the tube type brass specimens in a sulfamate nickel barrel solution. The effect of barrel hole size and barrel hole area on the throwing power was also discussed.