The Rheological Regularity And Mechanism Of Ultrasonic Spinning Study

When spinning ultra thin-walled cylinders, If the force is too big it will cause the work piece defects such as cracking, upheaval, wrinkle and tear. The method of overcoming the defects is to reduce the axial pressure of the rotating wheel and to reduce tangential stress. Studies show that ultrasound can reduce the deforming force of the material. Study the mechanism of ultrasound on the material plastic forming is great significance for promoting the application of ultrasonic plastic processing.Using the ABAQUS simulation of ultrasound extrusion and conventional extrusion, study found that ultrasound extrusion molding force acting on work pieces in a pulsed manner. The average force of ultrasonic extrusion is less than about50%of the conventional extrusion. When the extrusion pressure is the same, the material deformation volume of the ultrasonic extrusion nearly doubled.Using ANSYS analysis modal of ladder-type horn, The results showed that the longitudinal vibration frequency is20574Hz,The resonant frequency of the horn is20073Hz, deviation of simulation value and actual value is only2.5%. Using the same method, the frequency of longitudinal vibration of the tool head is20431Hz.Designed and produced a test rig of ultrasonic vibration extrusion. Test for conventional extrusion and ultrasonic extrusion of7050aluminum alloy and C-276nickel-base alloy specimens. Found that the deformation volume of ultrasonic extrusion is increased two times more than that of conventional extrusion. Ultrasound makes the material "softening" and reduces the material forming force. The essence of "soften" is due to the decrease of young’s modulus. Under the same conditions, the greater amplitude, the more deformation volume.Combining the theory of phonon, the metal plastic deformation mechanism and lattice vibration theory to study the driving mechanism of the ultrasonic vibration on the rheology of materials. Studies have shown that the ultrasonic vibration in the crystal slip plane stimulate high-energy short-wave phonon, Phonon propagation to high density dislocations grain boundary of deformation zone. Lead to the transition of the atomic kinetic energy and potential energy. Finally, it transforms into plastic deformation. If the chance of pulse slip is equally likely, the transfer of energy is proportional to pulse frequency in unit time.The paper have designed an ultrasound spinning bench and have done the experiment of conventional spinning and ultrasonic spinning on LY12aluminum alloy tube body. The results show that ultrasound spinning is more conducive to the plastic flow of the material. This process can also improve the surface quality. Ultrasound spinning can reduce the spin pressure. Using the ultrasound spinning process can obtain the same amount of deformation as the ordinary spinning with smaller rotary pressure.The results of this paper are important for the spinning of ultra thin-walled cylinder. It provides a theoretical and methodological guidance for the design of the ultrasound spinning process systems. The problem of spinning of thin-wall tube is expected to be resolved.