Research On Honing Magnetorheological Polishing Process And Mechanism On The Inner Surface Of Titanium Alloy Tube

Titanium alloy tubes have become indispensable components in the industrial field due to their excellent comprehensive mechanical properties,corrosion resistance,high specific strength.In order to improve the mechanical performance of titanium alloy tube,the inner surface of titanium alloy tube needs to be polished.However,titanium alloy is a difficult material to be processed,so current processing technologies have some limitations in machining the inner surface of titanium alloy tubes,for example,traditional mechanical processing,abrasive flow machining,electrochemical polishing and magnetic abrasive finishing.In this paper,magnetorheological polishing(MRP)is proposed to improve the inner surface quality of titanium alloy tubes.MRP process is realized relying on the rheological properties of magnetorheological fluid under the external magnetic field.On the application of an external magnetic field,magnetorheological fluid will be stiffened to form a flexible polishing mold and the shape of the polishing mold can be automatically changed in accordance with the shape of workpiece.The deterministic polishing strategy can be realized by controlling the motion trajectory of the polishing mold.At present,MRP process is mainly applied on polishing nonmetallic materials such as optical parts.A few researches are carried out to apply MRP process on machining metallic materials.Finishing the titanium alloy tubes by MRP process not only eliminates the surface defects of the inner surface and ensures smooth transmission of fluid medium,but also fills the gap of MRP process on finishing titanium alloy tubes.In order to finish the inner surface of titanium alloy tube by MRP process,the main research work in this paper is as following:(1)Referring to the experience of designing MRP equipment in domestic and foreign,a honing magnetorheological polishing process was proposed to finish the inner surface of titanium alloy tubes.According to the work requirement of polishing device and design requirement of parts,the standard parts in the polishing device were selected and the nonstandard parts were designed.In accordance with the motion requirement of the MRP device,the corresponding driver was programmed.The MRP device was successfully developed finally.(2)Based on the requirement of magnetic field intensity in polishing process,two kinds of excitation devices combining electromagnet with permanent magnet were proposed.Static magnetic field simulation was carried out using the ANSYS Maxwell software.The effects of polishing head material and the distance of the gap between the inner surface of titanium alloy tube and polishing head on the magnetic field strength of polishing area were studied under different experimental conditions,respectively.Comparing the simulation data,the magnetic field characteristics of the two excitation devices were compared and analyzed.(3)By simulating the composition structure of magnetorheological polishing fluid under the external magnetic field,the polishing force acting on the workpiece surface was analyzed.The pressure model and shear force model acting on the workpiece surface were established.Based on the established polishing force model and the microstructure on workpiece surface,the surface roughness model of workpiece surface was established.(4)The effects of magnetic field intensity,rotational speed of the tube,processing time,types of abrasive particles,volume fraction of abrasive particles,volume fraction of magnetic particles and initial surface roughness of workpiece on polishing performance were investigated by the single factor experiment.The roughness model of workpiece surface was verified through comparing the calculated data with experimental data.