Sharif Digital Repository

Drilling super alloys with a good hole quality and acceptable surface finish is a constant challenge in modern industries dealing with such materials. Ultrasonic assisted drilling is a modern and nonconventional method of drilling which has attracted many researchers attention recently. In this study deep drilling on Inconel 738 LC is done using ultrasonic assisted drilling technique and the results are compared with those of Electro Discharge Machininng or EDM method. The results show that Ultrasonic Assisted Drilling or UAD is an appropriate alternative for EDM of Inconel. The whole process time is decrease dimensional accuracy is improved and surface roughness is decreased significantly.... 

In metal matrix composites, the metal is reinforced with ceramic particles to get appropriate properties for hardness, resistance to fatigue, wear resistance and strength. Aluminum matrix composites have lower density than steels. These kinds of materials are used in military, automotive and aerospace industries due to their high strength to weight ratio and resistance to corrosion and wear. Application development of these materials are limited due to high machining and production costs. High ductility and strength of these materials and also hardness of ceramic particles cause rapid wear of tools and higher roughness of the surface. In this project the effect of ultrasonic vibration of a... 

One of the main problems in human health, both in advanced societies and in growing societies, is a variety of cancers, one of which is brain tumor. One of the non-invasive methods of treating tumors is the use of ultrasound.HIFU (High Intensity Focused Ultrasound) therapy method is known as one of the most advanced surgical techniques in tumor ablation therapy. HIFU are produced and concentrated by powerful transducers. The two main mechanisms in HIFU are mechanical and thermal mechanisms, and the effects of these two mechanisms appear as thermal effects and cavitation. The fundamental mechanism in the HIFU is to absorb ultrasonic waves and to convert them into heat.The purpose of this... 

In the present study, the performance of fly ash-based geopolymer concrete blended with cement as an additional calcium source under exposure to marine, acidic and alkaline environments was evaluated. Three mixtures of fly ash-based geopolymer concrete with different cement ratios (0, 10 & 20%) were prepared and immersed in tap water, seawater, sulfuric acid, and sodium hydroxide solutions for up to one year. Change in the appearance, weight, compressive strength, splitting tensile strength, energy absorption and microstructure of the specimens were evaluated at 1, 3, 6, 9 and 12 months of exposure. Ultrasonic pulse velocity test was also used to determine its relationship with the... 

Today microbubbles are broadly used as ultrasound contrast agents. These bubbles enhance the image resolution of B-mode pictures. Flow focusing in microchannels could provide us the goal of one-size bubbles generation. Microbubbles could use as tracers in Echo_PIV method to determine the velocity profile in main body vessels such as carotid. In this paper we introduce a new production method to fabricate a low-cost microchannel for preparing Microbubble contrast agents (less than 50 microns) by using some surface active agents and a viscosity enhancing material to obtain appropriate Microbubbles with desired life time and stability for any in vitro infusion for velocity measurement. By... 

In Ultrasonic Assisted Machining (UAM) a mechanical vibration is added to the relative motion of the tool and workpiece. The frequency of vibration is typically from 20kHz to 100kHz and the amplitude is in the range of 10 to 20 microns. Experiments show that using this method improves the machining performance. Reduction in machining forces and tool wear and improving the cooling condition are some of the advantages of UAM. In this work, the forces of ultrasonic assisted milling are investigated. Applying thin shear plane theorem provides an acceptable theoretical base with minimum dependence on experimental data to analyze machining forces. To evaluate the model and find the effect of... 

Nowadays, application of ultrasonic wave technology as a novel method of enhancing oil recovery and also gas and oil well stimulation is prevailing. Not only this method is environment friendly, but also it is economic. Although the application of this method is proved to be of outstanding positive influences in field operations. In this study, it is intended to investigate the effect of ultrasonic waves on the rate and final recovery of miscible and immiscible injection of fluids as Enhanced Oil Recovery (EOR) methods by using the Micro model apparatus and Although the effect of the waves on fluid flow through the porous media can be studied. The results of this work are a good guidance to... 

Machining of Aluminum Metal Matrix Composites faces different problems including adhesive wear, large machining forces, chatter, poor surface quality and therefore low geometric accuracy etc. due to the fact that a ductile matrix is supporting brittle particles. On of the methods used to reduce such difficulties is vibration assisted machining in which a 10 to 20 micron displacement stimulation is applied to the workpiece or tool during machining process. The effect of this method on the milling of the Al/Sic composite is studied through two separate experiments including one and two dimentional vibration assisted milling respectively. Milling forces, tool wear and surface quality are... 

This research studies the feasibility of the BK7 optical glass milling process with ultrasonic vibrations. Due to the fragility of glasses, especially optical glasses, machining is very sensitive and complex. For this reason, it is necessary to think for the glass machiners to minimize the defects and failures of the process. So far, efforts have been made to reduce the defects caused by machining on brittle materials, such as increasing the speed of the period, reducing the feed rate of the tool, changing the geometry and the type of tool, the type of process lubrication, etc. In addition, other operations performed to improve the surface of the glass are of better quality, using hybrid or... 

Most of the time there are three different materials in oil wells; Oil, water and gas. Measuring volume percentage and flow of the individual materials (phases) is an important issue, due to their critical role in extraction process control. Measuring tool should be able to measure flow and percentage of each phase in a case that they are separated (in deviated wells due to gravity). In addition, the measurement should be carried on in a high temperature and high pressure environment and in presence of corrosive substances. Most of previous researches on Multi-Phase Flow Meter (or MPFM) led to mechanical methods to measure flow and they usually use electrical impedance or permittivity for... 

Laser ultrasonic is a novel method for measuring sheet parameters. In this technique an intense pulse is irradiated to the target which instantaneously vaporizes the surface layer into the high temperature and high pressure plasma. Expansion of plasma produces shock wave that propagates through the surface. Mechanical properties of target can be calculated by measuring and analyzing produced shock wave. In this project wave propagation is simulated using finite element and numerical-computation methods. The numerical-computation simulation was performed using lamb wave equations. ANSYS software was employed for finite element simulation. The results corroborate each other. Next, simulation... 

Ultrasonic wave attenuation is an effective descriptor of distributed damage in inhomogeneous materials. Methods developed to measure wave attenuation have the potential to provide an in-site evaluation of existing concrete structures insofar as they are accurate and time-efficient. In this study, material classification and distributed damage evaluation were investigated based on the sinusoidal modeling of the response from the through-transmission ultrasonic tests on polymer concrete specimens. The response signal was modeled as single or the sum of damping sinusoids. Due to the inhomogeneous nature of concrete materials, model parameters may vary from one specimen to another. Therefore,... 

Ultrasonically assisted machining process has been introduced as an effective solution to improve machining quality of mechanical parts. This study aims to reduce the drilling induced delamination to increase mechanical properties of CFRP laminates. Delamination decreases the strength of laminates under static and dynamic loads. Drilling parameters (feed and spindle speed) and ultrasonic vibrations amplitude are chosen as design experiment factors. Taguchi design of experiments method is used to study the effect of input factors on drilling thrust force, delamination factor and residual strength of drilled laminates. Input factors are in three levels and Taguchi L9 array is utilized. To... 

Pipelines are the preferred means for transporting of liquid or gas phase materials. The economy of many countries is extremely dependent upon a large network of pipelines systems to transport and distribute the nation’s energy resources. Damages to the pipe structure may cause leakage and result in economic losses or even loss of life. Developing methods for detecting the anomalies and damages to the structure before they lead to catastrophic events is vital. Multiple pipeline misadventures over the past several years have resulted in hundreds of fatalities and billions of dollars in property damages. These accidents demonstrate that the current monitoring methods are not sufficient... 

Delamination is a major problem in drilling of fiber-reinforced composite materials. Thrust force is an important factor leading to propagation of delamination during drilling process. One of effective methods to reduce machining forces is application of ultrasonic vibrations. In this study ultrasonic assisted drilling is applied to reduce thrust force in drilling of GFRP laminates. In order to conduct experiments a setup is designed and fabricated to apply both vibrations and rotation to drill bits. Using Taguchi method, a set of experiments is conducted with feed rate, spindle speed, point angle and ultrasonic vibration amplitude as control factors. The results show that applying... 

The precise measurement of fluid flow in different fields of the industry is vitally important. In addition, due to enormous hydrocarbon reservoirs, Iran is the biggest owner of gas reservoirs in the world and exact measurement of fluids is of considerable importance to consumption or export. Ultrasonic flowmeters that are the most useful ones of them consist of three elements made of piezoelectric, impedance matching layer and backing material. In this study, on the contrary to former backing materials which usually use of titanium, tungsten, and aluminum oxide as a composite Filler, for the first time, tungsten oxide is used. In order to do this, composite samples were built of tungsten... 

In the oil industry, a better understanding of the well condition leads to improve the management and increase the oil production. Production logging tools is a set of tools for measuring different parameters such as density, diameter and flow in oil and gas wells. These tools are considered among high-tech tools in the oil industry. The reason is that they should work in harsh conditions, i.e. high temperature about 170 ° C and pressure around 15000 psi, and at the same time give an accurate measurement of the quantity. Current production-logging tools measure the fluid velocity and the diameter of an oil well by individual mechanical tools, and the density by a radioactive densitometer. ... 

Deriving the shape, area, volume, and orientation of a defect from the ultrasonic nondestructive testing images of the oil pipelines, paves the way for the estimation of its severity. This paper describes the design and implementation of an automatic structure which can move an ultrasonic probe over the surface of a test sample, while preserving the distance, i.e. stand-off, between them, whatever the shape of the surface might be. The fixed stand-off is implemented, closing a feedback loop with a distance meter sensor. Also an integrated software environment is developed for the control of the table, data acquisition, data processing and displaying the results. After acquiring the... 

Carbon Nanotube webs exhibit interesting properties when used as thermo-acoustic projectors. This work studies thermo-acoustic phenomena of these sound sources both in near and far field regions. Our three-dimensional simulation and experimental data show pressure waves are highly affected by dimensions of sound sources in near field due to interference effects. Although pressure amplitude increases with increasing frequencies, maximum pressure amplitude reached in lower frequencies may become larger than its maximum amount at higher frequencies because of interference effects. Measurement of different surface area sources shows generation of sound waves in far field is independent of... 

Resonance acoustic spectroscopy (RAS) is one of the techniques used for monitoring the production quality and evaluation of mechanical properties of cylindrical components, due to their non-destructivity, high precision and quickness.
In this technique, the resonance effects are caused by the excitation of eigenvibrations of structure by an incident acoustic wave located in far-field. The resonance spectroscopy (isolation and identification of the resonance features) is performed on the far-field scattered pressure field which contains valuable information about the characteristics of the target. Appropriate exploitation of these resonance informations from the theoretical model and...