ارتعاشات التراسونیک

Ultrasonic vibration assisted drilling is a new technique, and one of the modern and promising processes for drilling metals, especially metal alloys with low machinability. In this paper, a set of laboratory tests is used to investigate the effect of using ultrasonic vibrations on the force required for drilling of the thin aluminum specimens. For this purpose, three aluminum workpieces with different thickness are drilled under three different rotation speeds, and four different penetration rates. The results showed that in two aluminum workpieces, 1 and 1.5 mm, the use of ultrasonic vibrations generally reduced the axial force, but in the 2 mm workpiece, it is impossible to understand a meaningful effect of applying ultrasonic vibrations. In other words, it can be said that adding ultrasonic vibrations with constant amplitude and frequency does not have the same effect on drilling in different conditions, and to reach the most efficient drilling; the characteristics of optimal vibration should be studied.

When two bodies slide on each other the asperities are engaged and friction is created. By superposing ultrasonic vibrations to one of the bodies, the friction force is reduced. This phenomenon is widely used in metal forming and metal cutting. In this research, experimental study of the effect of ultrasonic vibrations has been on sliding friction force in longitudinal direction. For this purpose, set-up was designed and fabricated. The main components of the set-up, including generators, transducers, first engaged body and second engaged body. The Set-up was installed on the machine lathe for investigation of the effect of ultrasonic vibrations on sliding friction force in longitudinal direction. The experiments were performed for eight different performance conditions. Next, the effect of each parameter ultrasonic wave velocity, roughness and material of contact surfaces were studied on the reduction of the friction force due to addition of ultrasonic vibrations. The result show that range of reduction friction force due to addition of ultrasonic vibrations in longitudinal direction is between 40 to 100% for the different performance conditions also friction force significantly reduced by increasing ultrasonic wave velocity so that friction force can be brought to zero by significant increase in ultrasonic wave velocity. The results also show that friction force has a more reduction for the surface has a less roughness. Aluminum-aluminum surfaces can be more reduction friction force from aluminum – steel surfaces.

When two bodies slide on each other, friction is created. By superposing ultrasonic oscillation to one of the bodies, the friction force is reduced. This phenomenon is widely used in metal forming and metal cutting. For the production and transmission of ultrasonic vibrations to a target it is required to use an ultrasonic system the components of which are a generators, a transducers and a horn. Horn constitutes an important part of the Ultrasonic systems. The main task of the horn is to transmit the ultrasonic vibrations and amplify the ultrasonic vibration amplitude at the output. In this study, an Aluminum horn was designed in cylindrical-conical-cylindrical shape geometry and was analyzed by the finite-element method(FEM) using the Abaqus software was manufactured. The resonance frequency obtained in Abaqus was equal to 19976 Hz. The resonance frequency obtained from the generator was equal to 19920 Hz. Hence there is a very good agreement between the experimental result and the FEM simulation. The difference between the finite element simulation results and the experimental ones is less than one percent. Moreover, a horn –workpiece assembly for applying the ultrasonic sliding friction was designed and manufactured. Then the fixture and the tool holder clamp were designed for the vibrating tool so that it can be installed on a milling machine and the friction force measurement is possible while the ultrasonic vibrations are applied.

In tube hydroforming process، due to friction condition، uniform wall thickness، as well as sharp corners may not be achieved. Use of ultrasonic vibration can improve the contact conditions at the tube-die interface. The current work studies the effect of applying ultrasonic vibration on wall thickness and corner radius of hydroformed tubes. By comparing the FEM models of tubes in two cases of with vibration and without vibration، it is possible to investigate the effects of vibration on process. In addition، the finite element analysis، as the modal and harmonic analysis، are used to design a set of ultrasonic tube hydroforming. A simple mechanism introduced in this paper is used to form the tube. The results indicate superimposing ultrasonic vibrations to the process will improve formability and spring back of the، and more uniform tube wall thickness will be achieved.