• 한국주조공학회지
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• 제22권5호
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• pp.238-244
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• 2002

Water and oil were completely synthesised with ultrasonic vibration energy irradiation. Pure Pb were added into Al melt during irradiated the ultrasonic vibration energy in 750. And the ultrasonic vibration energy was applied to Al-Pb melt to enhance the miscibility. Microstructural analysis, thermal analysis and X-ray diffraction analysis were carried out to evaluate the effect of the ultrasonic vibration energy on the castability and microstructural reliability. (1) Using the ultrasonic vibration energy irradiation, the complete mixing of water and oil was obtained. (2) The microstructure was refined by the application of ultrasonic vibration energy in Al-Pb alloys. (3) Relatively large Pb particles, $5{\mu}m$ were most distributed alone the grain boundaries with fine Pb particles evenly distributed in the matrix. (4) The solubility of Ph in Al-Pb alloys was increases up to 5% with the application of ultrasonic vibration energy.

• 한국생산제조학회지
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• 제19권3호
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• pp.402-406
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• 2010

Conventionally, the machined surface roughness in nano-second(ns) laser machining is damaged and rough due to thermal effects. To obtain the improved surface finish, the ultrasonic vibration is applied to ns-laser machining. The ultrasonic vibration jig is developed to apply the ultrasonic high precision motion to workpieces. And then the ns-laser machining is conducted to compare the effects of the ultrasonic vibration. The results show that the surface roughness with ultrasonic vibration is smoother than that without the vibration. The phenomenon could be explained as enhancement of heat transfer by ultrasonic vibration.

• 한국기계가공학회지
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• 제11권1호
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• pp.13-19
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• 2012

In this study, ultrasonic vibration tool designed and made by using FEM analysis. And machining test was carried out in various machining conditions using ultrasonic vibration capable CNC machine. For work material, alumina ceramic ($Al_2O_3$) was used while for tool material diamond electroplated grinding wheel was used. To evaluate ultrasonic vibration effect, grinding test was performed with and without ultrasonic vibration in same machining condition. In ultrasonic mode, ultrasonic vibration of 20kHz was generated by HSK 63 ultrasonic actuator. The two grinding speeds, 1.67m/s and 3.35m/s, were applied. On the other hand, grinding forces were measured by KISTLER dynamometer.

• 한국소음진동공학회논문집
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• 제20권11호
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• pp.1078-1088
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• 2010

In order to analyze the quantitative characteristics of acoustic streaming, experimental setup of 3-D stereoscopic PIV(particle imaging velocimetry) was designed and quantitative ultrasonic flow fields in the gap between the ultrasonic vibrator and heat source were measured. Utilizing acoustic streaming induced by ultrasonic vibration, surface temperature drop of cooling object was also measured. The study on smart cooling method by acoustic streaming induced by ultrasonic vibration was performed due to the empirical relations of flow pattern, average flow velocity, different gaps, and enhancement on cooling rates in the gap. Average velocity fields and maximum acoustic streaming velocity in the open gap between the stationary cylindrical heat source and ultrasonic vibrator were experimentally measured at no vibration, resonance, and non-resonance. It was clearly observed that the enhancement of cooling rates existed owing to the acoustic air flow in the gap at resonance and non-resonance induced by ultrasonic vibration. The ultrasonic wave propagating into air in the gap creates steady-state secondary eddy called acoustic streaming which enhances heat transfer from the heat source to encompassing air. The intensity of the acoustic streaming induced by ultrasonic vibration experimentally depended upon the gap between the heat source and ultrasonic vibrator. The ultrasonic vibration at resonance caused the increase of the acoustic streaming velocity and convective heat transfer augmentation when the flow fields by 3D stereoscopic PIV and temperature drop of the heat source were measured experimentally. The acoustic streaming velocity of air enhancement on cooling rates in the gap is maximal when the gap agrees with the multiples of half wavelength of the ultrasonic wave, which is specifically 12 mm.

• 한국기계가공학회지
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• 제13권3호
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• pp.96-102
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• 2014

This study focused on the effects of ultrasonic vibration on a machined surface of Al6061 material in the endmill cutting process. It is known that ultrasonic vibration greatly increases the efficiency of the machining process when cutting or grinding. An ultrasonic vibration table was developed for application to ultrasonic vibration endmill machining experiments.Inthisstudy,the surface roughness and actual depth of the cut measured confirm the effects of ultrasonic vibration. As a result of the experiments, the actual depth of the cut increased during endmill machining when using ultrasonic vibration. The surface roughness was improved with increases in the amplitude of the vibration and the depth of the cut.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.364-367
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• 2008

Finite element model and the basic experimental method have been developed to help the design of the transverse ultrasonic horn for flip-chip bonding. With two types of design the horn performance and ultrasonic characteristics are verified by using laser vibrometer. These analysis and experiment results can be the fundamental data for ultrasonic horn design considering the vibration modes and performance.

• Journal of Mechanical Science and Technology
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• 제17권8호
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• pp.1203-1210
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• 2003

Emission of ultrasonic vibration to turbulent flow promotes the turbulence generation due to the resonantly oscillating pressure field and thereby induced cavitation. In addition, ultrasonic vibration is well transmitted through water and not dissipated easily so that the micro-bubbles involved in the fluid induce the gaseous cavitation if the bubbles are resonated with the ultrasonic field. In the present study, we found through LDV measurement that the gaseous cavitation induced by ultrasonic vibration to CO$_2$saturated water flow in the rectangular cross-sectioned straight duct enhances turbulence much more than the case of non-ultrasonic or normal ultrasonic conditions without gaseous cavitation. We also found that the fluctuating velocity component induced by emitting the ultrasonic vibration in normal direction of a rectangular channel flow can be redistributed to stream-wise component by the agitation of gaseous cavitation.

• 구강회복응용과학지
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• 제18권3호
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• pp.225-233
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• 2002

This study was aimed to evaluate the effects of ultrasonic vibration on margin types and cements by comparing bond strength of cemented crown. In this study, margins of each metal die, which were chamfer, shoulder and shoulder with bevel, were prepared using computer milling machine. Specimens were cemented with zinc phosphate cement or resin cement. The specimens were divided by the finish line and cement used, ultrasonic vibration. I made total 84 specimens. All specimens were divided into two groups. One group was not vibrated, the other group was subjected to ultrasonic vibration for 12 minutes. Tensile bond strength was measured using Universial testing machine. The changes of bond strength in groups were statistically analyzed by t-test or One-way ANOVA. The results were as follows : 1. Ultrasonic instrumentation diminished the bond strength of crown cemented with zinc phosphate cement and resin cement after 12 minutes application. 2. In case of zinc phosphate cement, the bond strength of a vibrated group was showed significantly decreased(p<0.05). In vibrated groups with zinc phosphate cement, shoulder with bevel exhibit a significant difference to chamfer and shoulder(p<0.05) 3. Resin cement was more resistant to ultrasonic vibration than zinc phosphate cement and showed no significant differences according to ultrasonic vibration and margin type. In conclusion, These results revealed that zinc phosphate cement was most affected and resin cement was the least affected by ultrasonic vibration. Especially shoulder with bevel design was most affected in zinc phosphate cement groups. we should consider these results and be taken in the application of ultrasonic vibration to any teeth restored with crowns.

• Korea-Australia Rheology Journal
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• 제21권1호
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• pp.17-25
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• 2009

We studied the flow characteristics of the polymer melt in the injection molding process with ultrasonic vibration by using the numerical analysis. To minimize the error between the experimental data and numerical result, we presented a methodology using the design of experiments and the response surface method for reverse engineering. This methodology can be applied to various fields to obtain a valid and accurate numerical analysis. Ultrasonic vibration is generally applied between an extruder and the entrance of a mold for improvement the flow rate in injection molding. In comparison with the general ultrasonic process, the mode shape of the mold must be also considered when the ultrasonic vibration is applied on the mold. The mode shape is defined as the periodic and spatial deformation of the structure owing to the effect of the vibration, and it varies greatly according to vibration conditions such as the forcing frequency. Therefore, we considered new index and found the forcing frequency for obtaining the highest flow rate within the range from 20 to 60 kHz on the basis of the index. Ultimately, we presented the methodology for not only obtaining a valid and accurate numerical analysis, but also for finding the forcing frequency to obtain the highest flow rate in injection molding using ultrasonic vibration.

• 소성∙가공
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• 제25권6호
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• pp.373-378
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• 2016

Recent researches have reported that the superposition of ultrasonic vibrations in metal forming provides beneficial effects such as the reduction of forming load, flow stress and interfacial friction which improves the surface quality of end products. This paper presents experimental investigations on the effects of ultrasonic vibrations in upsetting tests of aluminum. The ultrasonic exciting system consists of piezoelectric transducer and resonator was designed and constructed to superimpose high frequency oscillation on the forming tools. Ultrasonic vibration-assisted upsetting tests were performed for three vibration modes five amplitudes, and the results were compared with those of conventional upsetting tests. The results showed that the superimposition of ultrasonic vibration reduces the upsetting load, and the load reduction is only dependent on the amplitude of the applied vibration regardless of deformation histories and vibration modes.