Nanofinishing of flat workpieces using rotational–magnetorheological abrasive flow finishing (R-MRAFF) process

A new finishing process named as “rotational–magnetorheological abrasive flow finishing (R-MRAFF)” has been proposed to enhance the finishing performance of MRAFF process. In this process, a rotation cum reciprocating motion is provided to the polishing medium by a rotating magnetic field and hydraulic unit. By intelligently controlling these two motions, a uniform smooth mirror-like finished surface with improved material removal rate and finishing rate (nanometer per cycle) is achieved for both stainless steel and brass workpieces. From the preliminary experiments, it is found that R-MRAFF process produces better results than MRAFF. Experiments have been planned using design of experiments technique. Analysis of variance is conducted to find out the contribution of each model term affecting percent improvement in surface finish. The optimum finishing conditions are identified from optimization study. The present study shows that the combinations of rotational speed of the magnet and its square term together have the highest contribution to the percentage improvement in surface roughness. Other significant parameters in the order of decreasing percent contribution to the change in surface roughness value are finishing cycles, extrusion pressure, and fluid composition. The best surface finish obtained on stainless steel and brass workpieces with R-MRAFF process are 110 and 50 nm, respectively. From the scanning electron micrographs and atomic force micrographs, it has been observed that the abrasive cutting marks generate cross-hatch pattern on the surface finished by R-MRAFF process.     

Enhanced magnetic abrasive finishing of Ti–6Al–4V using shear thickening fluids additives

The available magnetic field assisted finishing process is considered as the critical stage for improvement of workpiece surface quality. This paper aims to investigate the key quality performance of an enhanced magnetic abrasive finishing in achieving nanolevel finish on Ti–6Al–4V workpieces with initial micrometer surface roughness values. The finishing media, combining the intelligent shear thickening fluids (STFs), carbonyl iron particles and SiC particles, is developed. Finishing experiments for Ti–6Al–4V workpieces are conducted using an established platform, aiming to investigate the effects of varying STFs concentration, working gap, feed rate and spindle rotational speed. It is observed from the experimental results that the developed finishing media is effective for surface finishing comparing to the finishing media without STFs. The surface roughness of 54 nm was achieved from the initial value of 1.17 μm, which improved by over 95%, under the experimental conditions of 0.8 mm working gap, 15000 mm/min feed rate, 900 rpm spindle rotational speed and 15 wt% STFs. Surface observations showed that a smooth surface without obvious scratches was obtained.     

Multi-response optimisation of sintering parameters of Al–Si alloy/fly ash composite using Taguchi method and grey relational analysis

In this paper, an attempt has been made to optimise the sintering process parameters of Al–Si (12%) alloy/fly ash composite using grey relational analysis. Al–Si alloy/fly ash composite was produced using powder metallurgy technique. Al–Si alloy powder was homogenously mixed with various weight percentages of fly ash (5–15 wt.%) and compacted at a pressure ranging from 307 to 512 MPa. The green compacts were sintered at temperatures between 575 and 625°C. Experiments have been performed under different conditions of temperature, fly ash content, and compacting pressure. Taguchi’s L₉ orthogonal array was used to investigate the sintering process parameters. Optimal levels of parameters were identified using grey relational analysis, and significant parameter was determined by analysis of variance. Experimental results indicate that multi-response characteristics such as density and hardness can be improved effectively through grey relational analysis.