Development And Experimental Study Of Longitudinal Bending Resonance Cutting System Based For Zirconia Ceramics

Currently,there is an increasing demand for precision devices in various fields such as medical treatment,mechanical processing,military equipment,acoustics,etc.To meet the functional requirements in special environments,many new materials and composite materials have emerged.For example,zirconia ceramics can maintain their original properties in environments with large temperature differences and are necessary in electronics,medicine,engine materials,mechanical parts,etc.,as they are less prone to bending deformation under large bending moments.However,conventional machining methods such as cutting this composite material can easily lead to defects such as tool breakage,rough surfaces,burrs,and workpiece damage.Therefore,more ultrasonic machining systems have been developed to meet the forming and processing requirements of new materials as well as those with special surface requirements.Through the analysis of existing ultrasonic machining modes and devices,the development of two-dimensional composite vibration machining systems is the most extensive.It has made significant improvements over single-direction vibration,achieving better precision,and compared to three-dimensional vibration modes,it is easier to achieve and control tool output trajectory.Therefore,the research in this article mainly focuses on the development of a longitudinal and bending composite twodimensional ultrasonic cutting device that can be easily implemented and control the output trajectory.The research work in this article:（1）Firstly,design the variable amplitude rod in the longitudinal-bending composite resonance device.Determine that the variable amplitude rod is a composite type with a conical section through longitudinal vibration characteristic analysis and calculate the dimensions of each stage.Study the bending vibration characteristics of the variable amplitude rod from the perspective of acoustic wave conversion and mechanics,and then analyze the conversion mechanism from longitudinal vibration to bending vibration.Based on the conversion mechanism,improve the structure of the conical section of the variable amplitude rod,and design the size and shape of the spiral groove on the conical section to achieve a large conversion rate and output the maximum bending vibration amplitude,thus realizing the output of the elliptical trajectory.（2）Secondly,design the transducer based on the determined dimensions of the variable amplitude rod.Determine the dimensions,shapes,and arrangements of each part of the transducer by analyzing its piezoelectric performance and solving the vibration equation.Combine the variable amplitude rod and the transducer to design a single excitation longitudinal-bending resonance ultrasonic processing device,and conduct simulation analysis on the structure to verify that the structure can generate longitudinal and bending vibration modes under the given frequency of 20 k Hz,and then resonate.Simulate the output amplitudes along the y-axis and z-axis at the end of the structure under the actual piezoelectric output sinusoidal signal conditions.The results show that the maximum amplitude along the y-axis is 19.604 μm,and the maximum amplitude along the z-axis is 6.9875 μm.The ratio of longitudinal and bending vibration amplitudes is 2.6,and the maximum amplitudes in both directions are reached at 20 k Hz,indicating that a two-dimensional elliptical trajectory of longitudinal-bending composite can be output at an excitation frequency of 20 k Hz.Finally,further verification is carried out by simulating the actual tool tip motion trajectory during processing using transient dynamics analysis.（3）After preliminary design of the longitudinal-bending composite vibration device,the structure needs to be optimized by selecting the factors that have a decisive effect on the output performance of the structure: helix angle,groove depth,and groove width.The range of values for these three variables is set,and the influence of each variable on the longitudinal-bending resonance frequency,longitudinal and bending vibration amplitudes at the output end,and the ratio of the deformation of the two types of deformation is explored one by one.The improved dimensions of the groove structure are determined to be a helix angle of 60 mm,a groove depth of 2.5 mm,and a groove width of 3.606 mm.The optimized structure is then simulated for longitudinal-bending composite vibration,and the results show that the resonance frequency is closer to 20 k Hz,the difference between the longitudinal and bending vibration frequencies is reduced from 148 Hz before optimization to 76 Hz after optimization,the ratio of the longitudinal and bending vibration amplitudes is improved from 2.7 to 2.19,and the output elliptical motion trajectory is closer to a standard ellipse,indicating significant optimization effects.（4）A machining device is used to build an experimental platform for longitudinalbending composite resonance cutting of zirconia ceramics,and three experimental variables are set,namely spindle speed,feed rate,and tool front angle,with surface roughness as the experimental objective.A three-factor and five-level orthogonal experimental design is established,and range analysis is conducted on the experimental results.The three variables are ranked in order of their impact on the experimental objective: feed rate > tool front angle > spindle speed,and the optimal parameter combination is determined to be a spindle speed of 100 r/min,a feed rate of 0.015 mm/r,and a tool front angle of 7°.Finally,analysis of the surface morphology of 25 experimental groups confirms that the machining accuracy achieved by this longitudinalbending composite resonance cutting device is two to three times higher than that of conventional cutting,with the highest level reaching 120 nm,indicating that the design of the longitudinal-bending composite resonance cutting device can effectively solve the machining problems of difficult-to-machine materials such as ZrO₂ ceramics.