Papers by Keyword: Ultrasonic

Abstract: The disturbances of vapor bubble to a laser beam in the underwater laser machinig process importantly limits the material removal rate and cut quality obtained. This issue is more essential for the laser micromachining process that a precise and small trench cut is highly needed. In this study, the ultrasound was used to energize and break up the bubble while the laser beam was performing a cut in water. Silicon was used as a work sample in this study as its significant usage in many micro-components. An ultrasonic transducer was located nearby the workpiece in an attempt to vibrate surrounding water. The results revealed that an increase in ultrasonic power increased the width and depth of cut channel. In addition, the workpiece surface obtained after the ablation was clean as similar to that performed by the ultrasonic cleaning. This combination of laser machining and ultrasonic cleaning processes can be another effective approach to cut thermal sensitive materials and also small components whose thermal damage and deposition of cut debris can be harmful to their functionality after laser ablation.

Abstract: Matching layers of acoustic impedance are intensively studied in ultrasonic transducers for the efficiency of wave transmission. Large impedance mismatch between the active element of piezo and parent material in long range ultrasonic is also expected to have the similar affects on the ratio of the transmitted and reflected waves which can cause high reflection at the interface that result acoustic wave ringing and indicate low transmitted energy for inspection over large areas. This simulation study present analysis of Lamb wave propagation through a single matching layer from a piezoelectric transducers. It explains transmitted waves into aluminum plate using different materials of matching plates at thickness of quarter wavelength. Four matching plates with close to the computed value of acoustic impedance had been used in FEM simulations to study effect of the matching layers on the transmitted Lamb wave in aluminum plate. The results indicated slightly different phenomenon of multiple wave reflections from the transmitted S0 and A0 modes at boundary of the matching layer.

Abstract: Complicated Lamb wave propagation in structures can cause a misinterpretation in defect location and sizing during nondestructive inspections. A visualization of Lamb wave interactions with oval defects was carried out in our study to investigate the phenomenon of fundamental Lamb wave interaction around defect by using a reduced model of plate in ABAQUS. The visualized wave propagations with oval shape of through defects in plates demonstrated different patterns of wave interactions for the symmetric and anti-symmetric modes. The results also visualized the mode conversions around defects which converted from the incident waves. The visualized changes on the wave structures due to wave interaction with defects is important to increase our understanding on the guided wave propagation and reduce misinterpretation in nondestructive inspection when using the wave modes during inspection on large structures.

Abstract: There is a growing demand for light and radar absorbing materials in both commercial and military purposes. In this paper, microwave properties of polimer based composites containing multiwalled carbon nanotubes used as fillers have been analyzed. The multiwall carbon nanotubes used in the composite were about 9.4 nm in diameter. The results show that the ultrasonic treatment modifies the dielectric properties of the composite. Both real and imaginary permittivity of composites is 2 times more than ordinary example after sonicating for 3 minutes.

Abstract: Considering environmental protection, the application of waste tire is getting thorough and extensive. Basing on the previous research results, the variation principle of ultrasonic velocity and attenuation in concrete with age, the author carries out the application research on predicting 28-daycompressive strength of crumb rubber concrete during early age. Through the regression analysis between the 2-7days ultrasonic parameters (velocity v and/or attenuation A) and the 28-day compressive strength of crumb rubber concrete, it is found that the correlative coefficient is greater than 0.90 and the relative square deviation is less than 15%. So it is practically reasonable to predict 28-day compressive strength of crumb rubber concrete by pre-established regression curves.

Abstract: A simple method was achieved to develop a coating of silver nanoparticles on paper using ultrasonic radiation. Silver nanoparticles were prepared by the chemical reduction method using triethylene glycol as a reducing agent. UV-Vis spectrometry was used to characterize the synthesized silver nanoparticles in solution. The coated papers were characterized the surface features by scanning electron microscopy (SEM) and energy dispersive spectrum (EDS). The particle size distribution was 78 – 311 nm in diameter depending on ultrasonication time. The coated papers revealed the most effective in the antibacterial activity against both Staphylococcus aureus ATCC 25923^Tand Escherichia coli ATCC 25922^T.

Abstract: The dyeing of cotton fabrics using Excoecaria bicolor (Excoecaria cochinchinensis Lour.) as a natural dye has been studied in both conventional and ultrasonic techniques. Excoecaria bicolor leaves were extracted by various extracting procedures, using different solvents. The extractability of dye from natural origin using power ultrasonic was also evaluated in comparison with conventional heating. The results of dye extraction indicate that power ultrasonic is rather effective than conventional heating at low temperature and short time. The color of each dyed material was investigated in terms of the CIELab (L*, a* and b*) values.

Abstract: This paper briefly describes the principle of the ultrasonic single point incremental forming of the sheet metal. In which we established the finite element model and finished the finite simulation with ABAQUS. According to the simulation result, we analyzed the influence law of vibration frequency of the axis on the distribution of the stress and strain of the sheet metal, the thickness, and the axial force in the process of ultrasonic single point incremental forming of the sheet metal. The result shows that the influence on the stress and thickness of the sheet metal is minimal, and the influence on the strain follows the law of cosines in which the strain is minimum when the vibration frequency is equal to 15kHZ.The influence on the axial force is that when the frequency is f=0kHz～40kHz the axial force decreases with the increase of the frequency. However, the axial force increased dramatically with the increase of the frequency when the frequency is above 40kHz.

Abstract: This paper present a study of the 2 dimensional ultrasonic vibration assisted micro-milling (UVAM) focused on the tool motion shape and tool trajectory. The cutting characteristics in 2 dimensional are in view by considering the trajectory of the amplitude of vibration towards tool locus into the workpiece during the tool rotation are explore in depth. The vibration platform travel in X_f direction known as a feedrate movement, thus the X and Y axis vibration generate simultaneously through the workpiece surfaces. Amplitude value acting on X and Y axis proposed a major effect as it will effectively change the shape of tool trajectory between oval and eclipse. This investigation found the major advantages of UVAM is come from the alternating cycle’s gap phenomena between tool and workpiece. The reduction of prediction of cutting force and the thinning chip thickness formations has been observe during the investigation. The theoretical finding will be discussing the potential to extended tool life, surface roughness and material removal rate in the conclusion for future research plan.

Abstract: This study presents new machining types of advanced materials. Super alloys, ceramics and fiber reinforced plastics started being used on a large scale in the last period, this making necessary the development of new machines and machining processes. This paper describes different methods of ultrasonic machining and makes a comparison between them. By ultrasonic machining can be understood a process that involves axial vibrations with a high frequency and low amplitude, for improving the machining conditions like chip flute removal, tool wear and temperature reducing. In this paper, are presented three different ultrasonic machining methods. In the first one, the cutting process is made by abrasive slurry inserted between the tool and the workpiece, in the second one is made by a rotating diamond-brazed tool and in the last one is made by a special drill. This paper aims to study the current status in this field in order to make a research program through collaboration between the Technical University of Cluj-Napoca and the tool company Gühring KG by which to develop ultrasonic drilling.