| Ceramics and other hard and brittle materials have excellent physical and mechanical properties,but its properties of high hardness and high brittleness make these materials difficult to machine,ultrasonic rotary machining has been proved to be an efficient machining method,which is very suitable for a variety of hard and brittle materials.In this paper,to solve the problems existing in the ultrasonic rotary machining technology,the design of vibration system and the experimental study on zirconia ceramic were carried out.The main research methods and conclusions of this paper are as follows:(1)The appropriate materials are selected for the material according to the special requirements of the components of the vibration system.The structure and the size of each part of the vibration system was designed and determined by one-dimensional longitudinal vibration theory.The three-dimensional model of the vibration system including the sandwich transducer and the two-stage ladder-type horn and the tool was modeled,which is laid for the dynamic analysis.The resonant frequency of the designed vibration system is 40 kHz.(2)The dynamic analysis of the vibration system(modal analysis and harmonic response analysis)is carried out by ANSYS software.The frequency response is optimized by frequency sensitivity method.The resonant frequency,node position and amplitude are main analyzed.The results show that the resonant frequency of vibration system is 40.05 kHz,compared with the theoretical design value,the error is only 0.125%;and one of the node position is in the installation ring position and the other is close to the tool clamping position;the amplitude can reach 6.5μm when the drive voltage is 150 V.Thus,the vibration system can meet the design requirements.(3)An impedance test was conducted using an Agilent impedance analyzer to verify the simulation results for the resonant frequency of the vibration system.The results show that the impedance curve and phase curve of the ultrasonic vibration system are smooth and no clutter,and the resonant frequency is 39.74 kHz.Compared with the simulation results,the error is 0.77%,which accords with the design requirements.(4)The vibration amplitude of the vibration system is tested by using the principle of laser interference.The results show that the ultrasonic amplitude increases with the increase of the resonant voltage in a certain range under the fixed tool length(20mm),which is almost a linear relationship,and the maximum amplitude can reach 8.08μm.The vibration at the installation ring is only 1.87% of the vibration at the end of the tool;and the vibration at the pressure cap is only 3.12% of the vibration of the end of the tool,compared with the vibration system of the single node(the vibration at the pressure cap is 37.5% of the vibration of the end of the tool)narrowed nearly 10 times.The performance of the designed vibration system meets the requirements of the intended design.(5)The ultrasonic energy,the spindle speed and the feed rate were taken as the process parameters of the process experiment.The machining results of the zirconia ceramic materials were carried out with the cutting force and the tool wear as the evaluation indexes.The surface morphology of the tool was observed by laser confocal microscopy to study on the tool wear mechanism in Ultrasonic Rotary Machining.The results show that the ultrasonic machining method can effectively reduce the cutting force and reduce the tool wear compared with the traditional processing method for the zirconia ceramic material.The maximum cutting force tends to increase gradually and then decrease slowly with the increase of the number of processing holes in the process of ultrasonic rotation processing;and the tool wear will increase with the increase of ultrasonic energy,spindle speed and feed rate within a certain range,where the feed rate has the greatest effect on tool wear,followed by the ultrasonic energy and finally the spindle speed;The tool wear mechanism of ultrasonic rotary machining zirconia ceramics mainly includes abrasion wear,abrasive grain crushing and abrasive grain shedding,among which the abrasive grains fall off mainly. |
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