The Development Of An Ultrasonic Vibration Rolling Device And Experimental Study For Titanium Alloy

Titanium alloy is the ideal aviation structural materialsbecause of its high specific strength and excellent corrosion resistance.However,titanium alloy parts are more sensitive to surface damage and defects than structural steels,stainless steels and superalloys.According to statistics,titanium alloy workpiece accident occurred about 25% is due to surface quality caused.And The rolling processing makes the work piece surface plastic flow with specific pressure,the peak ofmicroscopic surface fills into the valley to improve the surface qualityof work piece.But the ordinary rolling process is easy to form a hardened layer on the surface of the workpiece,and the layer phenomenon takes place between the internal matrix material and surface layer,easy to cause the surface layer off.Combining ultrasonic machining technology with ordinary rolling can not only enhance the effect of rolling reinforcement,but also solve the layer phenomenon of workpiece surface.In this paper,the ultrasonic vibration rolling device was designed and manufactured by using PZFlex finite element software firstly.Then,the influence regularity of different process parameters on the microstructure and mechanical properties of TC4 titanium alloy was studied by using the rolling device.This paper mainly completed the following work:1.Firstly,according to the basic theory of mechanical vibration,the structure and size of the ultrasonic vibrator are calculated based on the one-dimensional longitudinal vibration equation under the resonance condition,and the corresponding stress and velocity distribution are analyzed.Then,using the finite element software PZFlex in the field of acoustic propagation,the transient dynamics analysis and simulation of the designed ultrasonic transducer are carried out by using the time domain transient analysis method.Simulation results show that the first order resonant frequency meets the design requirements and is in good agreement with the theoretical design.And its steady-state response,vibration displacement and crosssection position are analyzed.According to the theoretical calculation and simulation results,the corresponding piezoelectric ultrasonic vibrator are manufactured and the actual resonant frequency is measured by frequency resomance analyzer.The vibration of the end face is measured by Doppler vibrometer.The results show that the simulation results and the actual measurement value is in a good agreement.2.Using the ultrasonic vibrator which was designed and manufactured,the clamp is designed and manufactured to match the traditional CNC lathe saddle with the vibrator,and the ultrasonic rolling system is built in the lathe.Different process parameters were employed in this paper to experiment on the outer surface of TC4 titanium alloy shaft by traditional tolling and ultrasonic rolling respectively.The XJP-3A metallographic microscope and the Agilent Technologies Inc G200 nanoindentation tester were used to observe the microstructure and nanoindentation of the workpiece surface respectively.The mechanical properties of the surface material were tested.3.The results of metallographic observation show that the grain refinement of the surface of the sample after rolling is obvious.The effect on metal materials of TC4 surface layer by ultrasonic rolling is more obvious than that of the ordinary rolling.Finally,the mechanical properties of the surface of the test specimen were tested by nanoindentation technique.The results show that the elastic modulus increase with the increase of the surface distance from the surface to the internal distance,and the elastic modulus increase with the increase of the number of times.At the same time,compared with the ordinary rolling,the elastic modulus value and the depth of the effect are obviously larger and the scope of action is wider.