وحید فرتاشوند

High-power ultrasonic transducers emit high-frequency waves in a liquid environment, creating intense sound fields that cause the phenomenon of cavitation inside the liquid tank. The explosion of small bubbles, known as cavitation, results from intense sound fields, as well as physical and chemical phenomena. This process is used to remove contamination from the surface of sensitive and complex parts. Determining the acoustic field of the ultrasonic transducer within the tank can assist in identifying the required number of transducers, the optimal distance between them, and the appropriate dimensions of the tank. Given the high cost of experimental tests, the finite element method is a suitable tool for predicting the behavior of the vibrating assembly and determining the ultrasonic acoustic field within the liquid inside the tank. In this research, the resonance frequencies of the vibrating assembly and the acoustic wave propagation field were investigated using COMSOL finite element analysis software. After fabricating the components and assembling the tank, the acoustic field resulting from ultrasonic vibration was measured in different positions of the tank using a high-frequency hydrophone during the experimental test phase. Based on the experimental mapping data and its comparison with the simulation results, both harmonic and superharmonic frequencies were observed simultaneously in the water environment. The consistency between the simulation results and the experimental tests demonstrated that the simulation method is a suitable tool for predicting the behavior of the liquid inside the tank under high-power ultrasonic vibrations.

The 3D printing technology allows the production of parts with complex geometry quickly. However, the printed parts have poor mechanical properties due to the nature of their layers and the presence of defects such as cavities and poor adhesion between the layers. This paper investigates the use of ultrasonic vibrations to improve the mechanical properties of acrylonitrile-butadiene-styrene printed components. Samples were fabricated with standard geometry of tensile test using a desktop 3D FDM printer. Process parameters are layer thickness and infill. Also, the time of ultrasonic imposing was selected as a variable parameter. The thickness of the print layers are 0.15, 0.2, and 0.30 mm, and the infill is 60, 80, and 100%. The design of the experiment was performed by the response level method. Then the uniaxial tensile test was performed on the samples, and the data were analyzed by analysis of variance (ANOVA). The results showed that the application of ultrasonic vibrations significantly improves the tensile strength of printed parts, which is greater in lower thickness. Also, with increasing the infill, the effect of ultrasonic vibrations increases, which can be due to better bonding of the print layers due to ultrasonic vibrations and reducing the number of pores in the low infill values. Therefore, it is found that by applying ultrasonic vibrations to the 3D printed samples, their mechanical properties were improved and could be used in performance evaluation.

Material cutting is one of the most widely used industrial processes, which is always accompanied by challenges. One of these challenges is the ability to cut materials with high elasticity such as rubber or soft and crispy materials such as cake. In order to increase the life of the tool and achieve a suitable and accurate cutting surface and achieve a high cutting speed, the technology of high power ultrasonic vibrations is used in the modern industries of tire and rubber production and food industries. The proper design of the ultrasonic cutting tool, guarantees the proper performance and the tool life. The design and manufacture of ultrasonic cutting horns is complicated due to the influence of various factors on the shape and dimensions of the part. In this article, the effect of the dimensional parameters of the horn design on two important output factors, namely the resonance frequency of longitudinal vibration mode and the uniformity of the vibrations of the front surface of the ultrasonic cutting horn made of titanium alloy, have been investigated and analyzed. The results have shown that by using design improvements in finite element software, it is possible to achieve a cutting horn with a frequency close to the nominal design frequency and with the highest uniformity of the vibration amplitude on the front surface of the horn.

Superimposing high power ultrasonic vibration on metal forming processes changes the mechanical behavior of the material and reduces its flow stress. These phenomena improve the ductility of material and reduce forming forces. To investigate the influence of ultrasonic vibration on various materials, standard compression and tensile tests under ultrasonic vibration could be performed. This research investigates the compression behavior of Ti-6Al-4V alloy under superimposed ultrasonic vibration. For this purpose, a special set-up was designed, fabricated and tested. Ultrasonic vibration is transmitted from the ultrasonic transducer to the booster and then guided by horn (punch) to apply to test sample. Horn geometry, vibrational mode shape and ultrasonic power were selected as input variables. The effect of specimen position in system vibrational mode shape was studied by using different ultrasonic transmitters, which allowed the specimen to place at node and anti-node positions. It is found that ultrasonic vibrations reduced the formability of this alloy. Acoustic hardening phenomena do not observe in this material. Also, flow stress of the material reduced under ultrasonic vibration up to 17.63% which has direct relation to ultrasonic power. In addition, the most efficiency was observed when the specimen placed in the node position.

Identifying piezoelectric defects and ultrasonic transducers failure based on electromechanical impedance is one of the methods to assess their health. In a healthy piezoelectric, the electromechanical impedance is determined based on the piezoelectric properties, shape and size. In order to identify and predict the failure of piezoelectric, in this paper, a practical and effective method for evaluating the quality and health of piezoelectric used in high power ultrasonic transducers is presented. The basis of this procedure is to study the change in electric impedance characteristics of the piezoelectric disc, which can be measured according to the standard. This method can be used by researchers and manufacturers of piezoelectric. The results of experimental tests have shown that by analyzing the impedance diagram of piezoelectric, it is possible to identify faults and defects in them; even before they are visible to the naked eye. It is also possible to compare the quality of different piezoelectric manufacturers and to evaluate the performance of a healthy worked piezoceramic compared to a new component.

Ultrasonic suspension can be used for a wider range of particles due to its independence from the material and its properties, For the possibility of suspension, and has a high potential for the transfer and movement of particles in a controlled manner. Suspension and separation of particles are due to acoustic force. Two parameters namely acoustic contrast factor and volume of particle are more effective in magnitude of this force. The first determines the direction of particle movement towards the node or antinode and increasing the volume of particles causes to increase acoustic force and thus increasing the velocity of particles in the fluid medium. In this paper, simulations were performed by solving the equations of wave and acoustic pressure in a fluid medium and tracking particles in the fluid flow from the inlet. Then, using the simulation results, a laboratory set-up was designed and fabricated. According to results, a good agreement was observed between the simulation and experiment data. Polystyrene and ABS particles were suspended in water and the velocity of larger particles increased.

Ultrasonic welding as a new technology in many industries has replaced the usual methods of joining such as welding, brazing, sewing and etc. In this technology, ultrasonic energy is generated by the ultrasonic transducer and transmitted to the joining area through the booster and horn. Ultrasonic energy is dissipated and absorbed in the joining area and generates heat. Simultaneous application of static force / pressure and heat causes the involved parts to join with each other. In this process, various parameters such as power, frequency, static force / pressure, time, material and shape of parts and etc affect the joining properties and the resulting sample. In this paper, with the aim of acquainting researchers with the principles and applications of this technology, scientific and industrial research in the field of ultrasonic welding has been reviewed. Due to the major application and different effective mechanisms, this paper is divided into two main parts of metal welding and plastic welding. Considering the importance and application of the subject, the principles and methods of applying ultrasonic vibrations, different mechanisms of ultrasonic, the parameters of the ultrasonic welding process and the important applications of this technology have been studied. Finally, a perspective on the application of high power ultrasonic vibrations in new manufacturing and joining technologies in the future of the industry is presented.

Hot pressing of metal powders is used in production of parts for similar properties to wrought materials. Since residual porosity, inhomogeneous properties, dimensional and geometrical instability and therefore reduction in mechanical strength are the main problems in powder metallurgy components which are due to friction between powder particle interfaces and powder compact and die walls. Because of this, access to parts with high density and homogeneous structure is the great object in powder metallurgy. One of the remedies can be employment of ultrasonic vibrations which is thought to result in increased rates of densification and therefore higher efficiency of the process in increase of part density and strength. To evaluate this solution, this paper deals with the effects of high power longitudinal ultrasonic vibrations on the densification of AA1100 aluminum and Ti-6Al-4V titanium alloy powder under constant applied stress and different temperatures. The effects of powder type and process temperature on the densification behavior and ultrasonic efficiency are discussed. For experimental tests, setup of ultrasonic assisted hot pressing of powders were designed and fabricated. The results show that applying ultrasonic vibrations leads to obtaining higher relative density. In addition, it is found that the effect of ultrasonic vibrations is greater for Ti-6Al-4V powders. However, the temperature has different effects on the ultrasonic vibrations efficiency in two types of powders.

Metal forming is a conventional manufacturing process that a material with simple form is subjected to plastic deformation and emerged to industrial end products. Reduction of forming forces and improving of products quality have been a promising object for investigators and artisans. To accede this purpose, primary methods such as increasing material temperature and modern methods such as use of high power low amplitude ultrasonic vibrations were introduced. In ultrasonic assisted forming, high power ultrasonic transducer produces low amplitude high frequency mechanical vibrations which transmitted to material subjected to deformation and contacting surfaces of tool/workpiece. Results show reduction of forming forces and tool wear as well as improving surface integrity and dimensional stability that lead to increasing production rate and process efficiency. By regarding to importance and capability of ultrasonic assisted metal forming, this paper is concerned with application of ultrasonic vibration on metal forming processes. To this purpose, fundamental and mechanisms of application of high power ultrasonic were introduces and discussed. Also, industrial future of this technology as well as its advantages, range of application and its restriction were mentioned.