| Titanium alloy is widely used in aerospace field because of its excellent comprehensive mechanical properties.However,due to the poor thermal conductivity and high chemical activity of titanium alloy,there are some problems in the process,such as low processing efficiency,serious tool wear and poor surface quality.The circular arc milling cutter has a larger curvature cutting edge,which can effectively increase the cutting width and improve the processing efficiency,but also lead to the increase of cutting force.As an advanced composite technology,ultrasonic assisted milling can realize the intermittent contact between the cutter and the workpiece in the processing,so as to reduce the cutting temperature,reduce the cutting force and improve the processing quality.Therefore,in this paper,the comparative method is used to study the milling force,chip morphology,tool wear,surface quality and so on.The research contents include the following aspects.Firstly,aiming at the machining difficulties of small curvature steep surface of titanium alloy aviation parts,according to the structural characteristics of the circular arc milling cutter,a reasonable grinding process is formulated.The grinding simulation of the circular arc milling cutter is carried out by using NUMROOT simulation software.The circular arc milling cutter is ground by using SAACKE five axis grinder,and the precision detection,coating and passivation of the circular arc milling cutter are carried out.Secondly,the influence of milling parameters on milling force with and without ultrasonic assisted machining is analyzed,and the influence mechanism of two kinds of milling methods on chip shape is analyzed.It is found that the introduction of ultrasonic assisted machining makes the cutting direction change periodically,and the tool chip contact state is greatly improved.Compared with conventional milling,ultrasonic assisted machining makes the cutting direction change.The force is greatly reduced,and the chip removal and breaking performance are better,so that the chip size and deformation are smaller.Then,the wear process,service life and wear mechanism of circular arc milling cutter with and without ultrasonic vibration are analyzed.The results show that compared with the conventional milling,the wear of the front and back face of the circular arc milling cutter is obviously improved,and the wear rate is slow and the tool life is long.In the aspect of wear mechanism,the main wear mechanism of circular arc milling cutter is abrasive wear when ultrasonic vibration is applied,and the main wear mechanism of circular arc milling cutter in conventional milling is adhesive wear.Finally,the variation of surface roughness and surface topography with and without ultrasonic vibration is analyzed.It is found that ultrasonic vibration improves the surface roughness and surface quality most obviously under the conditions of low speed,large cutting width and large feed;different from conventional milling,ultrasonic vibration assisted milling has better surface quality under the time-varying cutting direction and tool path,even when the tool wear is serious. |
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