| As a light structural metal,magnesium alloy has the characteristics of high specific strength,good heat dissipation,easy recovery and so on,and has a broad prospect of development.It has been widely used in the fields of aerospace,transportation and electronics.However,magnesium alloys with dense hexagonal crystal structure can only start the base plane slip system at room temperature.resulting in poor plasticity at room temperature.As a new sheet metal forming technology,incremental forming teclhnology can obviously-improve the sheet metal forming limit by replacing traditional one-step forming with successive partial forming.The resistance thermal technology based on PID temperature control can realize the constant control of tool head temperature of incremental forming,realize the research of thermal incremental forming of magnesium alloy plates,and improve the forming performance and quality of magnesium alloy plates,the main research contents of this thesis are as follows:(1)Based platform was introduced based on existing incremental forming PIDtemperature control electric heating equipment,the equipment in the tool head real-time temperature of the PLC program will be collected after comparing with the given temperature output control signals to the high frequency dc power supply,control of high frequency dc power output value so as to control the temperature of the tool head,achieved the purpose of constant temperature heating.thus build the heat resistance temperature control single.point incremental forming experiment platform.(2)The effect of temperature on the forming properties of magnesium alloy sheet was studied by conducting the incremental groove experiment of resistance thermal control temperature,the effects of temperature on the forming height.strain distribution,forming force change and microstructure of the sheet were quantitatively analyzed,the optimum forming temperature range of magnesium alloy sheet was obtained.Through experimental study on the heat resistance control pyramid,the tool head under the temperature 300 ?,feed rate,tool diameter and step size effect on the properties of sheet metal forming,optimizing the process parameters are obtained.The microstructure of the optimized products was analyzed,and the dynamic recrystallization of sheet metal was found by metallographic experiments.(3)Based on response surface method,surface roughness experiments were carried out to study the influence and significance of forming temperature,feed rate,step size and tool diameter on the surface roughness of the workpiece in resistance thermo-controlled incremental forming.As temperature,feed rate,step size and the tool diameter is 150'C respectively,1200mm/min,0.2mm and 10mm,surface quality is better.Based on the orthogonal experiment,the forming precision experiment of square and cone parts was carried out,and the influence and significance of forming temperature,feed rate,tool diameter and step size on the geometric precision of the parts in the process of resistance thermo-controlled incremental forming were studied.Within the scope of the selected parameters,forming temperature,feed rate,step size and the tool diameter is 250?respectively,1000mm/min.0.2mm and 8mm,high geometric accuracy of fabrication.(4)In optimization of forming process parameters on the basis of the magnesium alloy sheet forming limit curves at fracture in incremental sheet forming,based on DIC non-contact strain measuring system,obtained the incremental forming process of the strain distribution law of parts and the strain information of burst point,constructed under 200?,250? and 300? of magnesium alloy sheet forming limit curves at fracture in incremental sheet forming,quantitative research is the forming temperature on the influence of forming limit curves at fracture,and the fracture is verified by experiment the correctness of the forming limit curves at fracture. |
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