Experimental Study On Micro-Thixotropy Of Sheet Extrusion And Its Ultrasonic Vibration

The technological parameters affecting the forming of thixotropic micro-convex platform in sheet metal extrusion were studied experimentally,and the influence of ultrasonic vibration on the forming of micro-convex platform was studied.Finally,the microstructure of the formed sample was observed.The main research contents of this subject are as follows:1.The experimental devices of micro-thixoforming in sheet metal extrusion and ultrasonic vibration sheet metal extrusion were built respectively.In micro thixotropic forming of sheet metal extrusion,temperature control system,heating system,cooling system and control of experimental forming accuracy should be considered in the experimental device.The design and cooling of horn are the most important factors in the micro thixotropy of ultrasonic vibration sheet metal extrusion.2.Orthogonal experiments were designed to study the effects of sheet metal thickness,forming speed,forming temperature and downward pressure on thixoforming height of micro-convex platform in sheet metal extrusion.It was found that defects such as outer convex hull and top convex hull appeared in macro-solid sheet metal extrusion were reduced in this experiment,and their theoretical explanation was given.Finally,the Ring Upsetting theory was applied to explain the similar defects in the experiment.The scale effect of sheet metal thickness is explained.3.Ultrasound vibration was introduced into micro thixoforming of sheet metal extrusion.The effects of different power applied at the same forming stage and the same power applied at different forming stages on the forming force and height of micro-convex were studied.The difference of forming height of the convex platform caused by ultrasonic vibration in the front and back stages is explained theoretically.4.The microstructures of different parts of the specimens after orthogonal test and ultrasonic vibration were analyzed and compared.The flow law of materials during micro thixoforming was discussed preliminarily,and the influence of ultrasonic vibration on the evolution of microstructures was found.