| Ultrasonic vibration abrasive flow machining is a method in which the tool head vibrates to drive the abrasive flow field to erode the surface of the workpiece to achieve material removal.A large number of studies have shown that under the influence of ultrasonic disturbance,the abrasive flow will form vortex micelles under the action of pulse and wall extrusion,and finally form turbulent flow with the continuous increase of lateral pressure and shear force.The abrasive near the turbulent vortex is affected by the pulsation of the flow field,which will generate additional pulse speeds in all directions,making the motion law more complicated.In addition,the collision and random motion of the abrasive can react against the turbulent flow and further evolve it.It can be seen that the ultrasonic abrasive flow field has strong randomness,unpredictability and diffusivity.Since the material removal is completed by the grinding action of the abrasive,it is necessary to carry out the motion characteristics of the abrasive flow field under the action of ultrasonic.analyze.Based on the ultrasonic vibration theory,this paper analyzes the machining mechanism of ultrasonic vibration micro-abrasives.In order to improve the machining accuracy and realize micro-machining,a new type of precision ultrasonic test platform is designed.The specific research contents and results are as follows:Based on the basic principle of ultrasonic polishing,the kinetic behaviour of the abrasive in the ultrasonic flow field was analyzed,a numerical model of single abrasive deburring under ideal conditions was established,and the influence of processing parameters on the impact load of the abrasive and the mechanism of burr fracture was discussed.Based on Computational Fluid Dynamics(CFD),the Eulerian two-fluid model was used to simulate the abrasive flow field under ultrasonic vibration.Predict the grinding mechanism of the abrasive on the surface of the sample.The research shows that the abrasive flow field will produce obvious turbulence under ultrasonic disturbance,the pressure of the flow field will pulse with the change of the resonance period,and the volume distribution of the abrasive particles will be affected by the resonance of the tool head,which will affect the polishing intensity.Large axial speed,the impact effect is obvious,and the tangential speed of the abrasive in the edge area is large,which can shear the protrusions on the surface of the sample.With the increase of the machining distance,the kinetic energy of the abrasive decreases continuously,and the grinding strength decreases continuously.From the analysis,it can be inferred that the improvement of the surface quality of the sample is mainly completed by the shearing action of the abrasive.In order to verify the rationality of the simulation results,the ultrasonic excitation abrasive flow orthogonal test was carried out with brass as the test object,and the morphological characteristics and distribution characteristics of the abrasive pits were analyzed by surface profile analysis and Matlab program.The research shows that the machining distance has a strong significance on the abrasive impact characteristics,followed by the machining time.There is an obvious transition zone from the center to the edge of the sample surface,and the abrasive impact effect is continuously weakened,which is basically consistent with the simulation prediction.In order to improve the machining accuracy of the traditional ultrasonic test platform,realize the micro ultrasonic machining,and introduce a compliant mechanism,a new type of precision ultrasonic machining platform is proposed,and the composition and working principle of the device are systematically introduced.Focusing on numerical modeling and simulation analysis of the fine-tuning mechanism,the static and dynamic characteristics of the mechanism are studied,and the sensitivity analysis of the mechanism parameters is carried out through Matlab,which is convenient for subsequent optimization design. |
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