Design and development of ultrasonic assisted-rotational magnetorheological abrasive flow finishing (UA-RMRAFF) process

The rotational-magnetorheological abrasive flow finishing (R-MRAFF) process, as one of the derivatives of the abrasive flow finishing (AFF) process, has a high potential for surface modification. However, the R-MRAFF process is a major challenge in terms of finishing time. The present study aims to propose ultrasonic vibration has been proposed as a technical solution to deal with the technological challenges of the R-MRAFF process. A new finishing method called the ultrasonic assisted-rotational magnetorheological abrasive flow finishing (UA-RMRAFF) process has been developed for the first time in which ultrasonic vibrations are applied to the workpiece perpendicular to the magnetorheological polishing (MRP) fluid flow direction. For this purpose, the workpiece was first kept in dynamic condition. Then, an ultrasonic horn was designed using the finite element method (FEM) to apply maximum amplitude to the workpiece. To evaluate the finishing efficiency of the UA-RMRAFF process, experiments were conducted on the internal finishing of Al2024 tubes at different finishing times for investigating and observing its effect on surface roughness (Ra) and material removal (MR). In addition, a comparative study was performed between the UA-RMRAFF and R-MRAFF processes in terms of % change in Ra (%ΔRa) and % improvement in MR. Experimental findings illustrate that the UA-RMRAFF process provides a uniform and fine surface finish without surface defects such as a mirror up to the range of 25.5 nm, in addition to increasing MR. Based on the results of the comparative study, the UA-RMRAFF process performs surface modification faster than that of the R-MRAFF process. While confirming these findings, the morphological and topographic analysis of the surface of the finished samples emphasizes that the main difference between the UA-RMRAFF and R-MRAFF processes is in the sinusoidal motion path of abrasive particles on the workpiece surface asperities, which clearly shows the effect of ultrasonic vibrations.