Experimental Study And Performance Prediction Of Ultrasonic Vibration Extrusion

Ultrasonic vibration extrusion processing technology as a new type of surface strengthening technology,has received the attention of domestic and foreign experts and scholar.On the basis of the ordinary extrusion processing,ultrasonic vibration is added to make the high frequency vibration,under the effect of extrusion pressure,the extrusion tool and rotating parts are against each other so that the surface of the material produced a cold hardening,improved the surface roughness and surface hardness and extended the service life of mechanical parts.In this paper,we used 45 steel as the sample material,through the orthogonal experiment method and piezoelectric ceramic transducer,self-designed extrusion head and horn,and CNC machine set up with ultrasonic vibration extrusion system,which all above used to test the experiments.The results of the experiment studied the effects of ultrasonic extrusion process parameters such like spindle speed,feed speed,extrusion pressure,amplitude extrusion tool head and extrusion times on the surface roughness and hardness enhancement.The microstructure of the machined surface was observed and analyzed,and the internal mechanism of ultrasonic vibration extrusion strengthening was obtained.Based on the theory of support vector machine,the nonlinear model of ultrasonic extrusion is established to find out the parameters which influence most of ultrasonic vibration.Through the experimental study of ultrasonic vibration,45 steel parts surface had plastic deformation,the microstructure changes,the grain is elongated,refinement phenomenon was found,the gap between the grains becomes smaller;The surface roughness of the parts is greatly reduced,the surface gloss is better,and the hardness of the surface is also improved.According to the analysis of the orthogonal experiment,the max influence of strengthening process is the extrusion force applied to the workpiece,the feeding speed of the extrusion tool and the number of times of ultrasonic strengthening is also has a large influence,butthe spindle speed and the amplitude of the tool has a relatively small impact to the processing.According to the theory of support vector machine(SVM),it can be concluded that the surface roughness of the parts decreases with the increase of the pressing force,and increases with the increase of the feed rate.The hardness of the surface of the part will increase due to the increase of the pressing force,butwith the increase of the number of extrusion,the trend will be first increased and then unchanged.Ultrasonic vibration extrusion processing technology can effectively reduce the surface roughness and hardness of shaft parts,but different process parameters have different effects on ultrasonic extrusion,during the ultrasonic vibration extrusion processing,we must according to the different Materials and requirements,select the appropriate process parameters to improve the mechanical properties of parts surface and extend its service life.