Wear 261 (2006) 856–866 Modeling and simulation of surface roughness in magnetorheological abrasive ﬂow ﬁnishing (MRAFF) process Sunil Jha, V.K. Jain ∗ Department of Mechanical Engineering, IIT Kanpur 208016, India Received 1 September 2005; received in revised form 5 January 2006; accepted 24 January 2006 Available online 20 March 2006 Abstract Magnetorheological abrasive ﬂow ﬁnishing (MRAFF) process was developed for super ﬁnishing of internal geometries of hard materials. This process relies for its performance on magnetorheological effect exhibited by carbonyl iron particles along with abrasive particles in non-magnetic viscoplastic base medium. The extent of ﬁnishing action depends on radial and tangential forces coming on abrasive particles due to carbonyl iron particles (CIPs) arranged in columnar structure in the presence of external magnetic ﬁeld. Experiments were conducted on stainless steel work pieces with different combinations of CIP and SiC particles in MRP-ﬂuid for same volume concentration. CIP chain structure and surface roughness evaluation model have been proposed. Magnitudes of the forces on abrasive particles were then calculated and change in surface roughness was computed using the model developed to simulate ﬁnal surface roughness. © 2006 Elsevier B.V. All rights reserved. Keywords: MRF; Magnetorheological polishing ﬂuid; MRAFF; Precision ﬁnishing 1. Introduction The ultra precision ﬁnishing technologies have grown rapidly over recent years, and have tremendous impact on the develop- ment of new products and materials. With the advent of these new materials, manufacturing engineers are facing challenge of machining and ﬁnishing these materials to meet their functional requirements. The available traditional and advanced ﬁnishing processes alone are incapable of producing desired surface char- acteristics on complex geometries, and in exercising in-process control on ﬁnishing action. Abrasive ﬂow machining (AFM) [1] process was developed to ﬁnish internal complex geometries by allowing abrasive laden polymeric medium to ﬂow over it under pressure. The abrading forces in AFM process are function of viscosity of viscoelastic polymeric base medium, which is very difﬁcult to control during operation. This lacks determinism in the control of ﬁnishing action. In another process developed for automated lens ﬁnishing, magnetorheological ﬁnishing (MRF) [2], external magnetic ﬁeld is used to control the rheological ∗ Corresponding author. Tel.: +91 512 2597916; fax: +91 512 2597408. E-mail address: vkjain@iitk.ac.in (V.K. Jain). properties of polishing medium, hence adds determinism in con- trolling surface topography being generated during ﬁnishing. The present applications of MRF process are limited to ﬂat, spherical and aspherical surfaces due to dwelling of work piece in the moving magnetorheological polishing (MRP)-ﬂuid rib- bon. To meet the ﬁnishing requirements of different geometries and incorporating better in-process control of ﬁnishing forces, a hybrid process by combining AFM and MRF was developed [3], and named as magnetorheological abrasive ﬂow ﬁnishing (MRAFF). A hydraulically powered MRAFF experimental setup was designed and fabricated to conduct ﬁnishing experiments. A study was made to understand the effect of magnetic ﬁeld strength on reduction in surface roughness (R a ), and the results were reported elsewhere [3]. The role of magnetic ﬁeld strength on decrease in surface roughness value was clearly observed. After preliminary study, the ﬁnishing performance of MRAFF process is found to be mainly dependent on MRP-ﬂuid compo- sition for the same magnetic ﬁeld strength, extrusion pressure and number of ﬁnishing cycles. MRP-ﬂuid composition is one of the key process parameters affecting ﬁnal surface roughness in MRAFF process due to its role in ﬂuid structure formation; hence it is taken up as a main factor for the present study. In this study the effect of size of silicon carbide (SiC) abrasives and 0043-1648/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2006.01.043