Multi-pole magnetorheological shear thickening polishing on inner surface of aluminum alloy slender tubes

The aluminum alloys slender tubes with high surface quality are required to improve the components performance. The inner surface polishing of slender tubes becomes a challenge because of the machining space limitation. In this work, a multi-pole magnetorheological shear thickening polishing (MP-MSTP) method, combining the dual excitation of magnetorheological principles and shear thickening behavior, is proposed for aluminum alloy slender tubes polishing. The magnetic field generator was designed integrating four cylindrical Nd-Fe-B radial magnetic poles. The magnetic flux density is investigated in the polishing zone based on finite element analysis (FEA) and experimental measurements. Mathematical modeling of material removal rate (MRR) was established based on single abrasive particle. The feasibility of the MP-MSTP method for aluminum alloy slender tube was verified by computational fluid dynamics (CFD) simulation analysis and experimental measurements. Polishing experiments were carried out on the inner surface of aluminum alloy slender tubes to investigate the effect of various processing parameters on surface roughness, including carbonyl iron particles (CIPs) and silicon carbide (SiC) abrasive particle sizes, working gap and workpiece rotational speed. The surface roughness was reduced to 155 nm from the initial 480 nm under the optimal polishing parameters. A smooth surface without micro-convex peaks and deep scratches was obtained after 50 min polishing based on ultra-depth-of-field microscope and SEM observation.