| Ceramic materials have been widely used in many fields,but due to their high hardness,brittleness,and brittleness,these materials have caused difficulties in processing and higher processing costs.In order to solve this problem,this paper proposes a method of multi-frequency ultrasonic machining,that is,based on ultrasonic machining,introduces a low-frequency vibration through the free mass,and the low-frequency vibration introduced by the free mass with the high-frequency vibration emitted by ultrasonic power?excited by ultrasound transducer complete the cutting together.This processing method can not only solve the shortcomings of high cost and low efficiency of the simple ultrasonic machining to a certain extent,but also can retain the advantage of the ultrasonic processing technology on the small damage of the workpiece,and further improve the processing efficiency,ensuring the processing accuracy and the completeness of the material.In this paper,the advantages of the multi-frequency ultrasonic machining method and related domestic and international research trends of the multi-frequency ultrasonic machining are introduced in detail.A multi-frequency ultrasonic machining drilling process is proposed,a multifrequency ultrasonic machining system is designed,and the multi-frequency ultrasonic machining mechanism and ceramics are analyzed.The mechanism of material removal has theoretically explored the effect of different free masses on the removal rate of ceramic materials,and derived the formula for material removal rate and the factors that affect the material removal rate.This paper first designed a stepped horn with a conical transition.The structural dimensions and parameters of the horn were calculated by analytical method.The CAD part drawing of the horn was drawn and limited in the design of the horn.On the basis of the analysis of the modal analysis and the harmonic response,the modal vibration frequency and modal vibration modes of the horn and the stress distribution curves and longitudinal displacement distribution curves of the horn were obtained.In order to study the effect of free-mass blocks of different shapes and sizes on the efficiency of multi-frequency ultrasonic machining,a multi-frequency ultrasonic machining drill capable of placing spherical and cylindrical free-mass blocks is designed,and this kind of multi-frequency ultrasonic machining drill is performed.The finite element modal analysis and harmonic response analysis show that the vibration frequency of the multi-frequency ultrasonic machining drill decreases with the increase of the length of the extension rod of the drilling rod within a certain range,and the vibration frequency is about 20000 Hz.Then the frequency vibration test and ceramic machining test under different free masses were performed using the processed multi-frequency ultrasonic machining drill.It was concluded that for free masses of the same diameter,the vibration clearance within the vibrating tube is small due to the spherical free masses.The low-frequency frequencies generated by the spherical free masses are higher than the low-frequency frequencies generated by the cylindrical free masses.At the same diameter,the corresponding material removal rate of the spherical free masses is higher than that of the cylindrical free masses.The corresponding material removal rate of spherical free masses increases first and then decreases with the increase of the diameter within a certain range,while the corresponding material removal rate of the cylindrical free masses increases with the increase of the diameter within a certain range.The 6mm-diameter spherical free mass has the highest material removal rate of 123(mg/min),and the non-free mass corresponds to the lowest material removal rate of 23(mg/min). |
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