Magnetorheological Abrasive Flow Finishing Research Articles

Experimental Investigations of Nano Finishing Process on Nickel-Free Austenitic Stainless Steel by Grey Relational and Principal Component Analysis

The nano surface roughness of metallic materials is important in engineering and medical fields for specific applications. Magneto rheological abrasive flow finishing (MRAFF) process was performed on nickel-free austenitic stainless workpieces in order to obtain surface roughness at the nano level and also to forecast the performance of the MRAFF process in terms of responses such as surface roughness (SR) and material removal rate (MRR). These two responses are affected by process factors such as hydraulic pressure, current to the electromagnet, and the number of cycles performed during the machining process. The design of experiments (DOE) was used to determine the contributions of process parameters to output responses. The techniques of grey relational analysis (GRA) and principal component analysis (PCA) were used in these experimental investigations to discover the process factors that minimise the final Ra and maximise MRR. Through the DOE, a minimum SR of 63.24 nm and a maximum MRR of 2.34 mg/sec were obtained on the samples for the combination of 30 bar pressure, 6 A current, and 300 number of cycles.

A study on in-vitro behaviour of stainless steel 316L subjected to rotational magnetorheological abrasive flow finishing process

In Rotational Magnetorheological Abrasive Flow Finishing (R-MRAFF) process, Magnetic Field Intensity (MFI) is the primary factor for the formation of ferrous chains which is responsible for finishing. Changing the pole distance between magnets to achieve a difference in MFI values will alter the strength of the ferrous chains. In this study, three different MFI values such as 0.34, 0.36, and 0.40 Tesla were chosen for finishing on Stainless Steel 316L (SS 316L). Surface wettability, bio-corrosion, and hemocompatibility studies were conducted to investigate the in-vitro behavior of SS 316L. The wettability of the implants changed from hydrophobic (100.92°) to hydrophilic (83.452°) surface as the MFI value increased. Bio-corrosion studies revealed improved corrosion resistance for R-MRAFF process finished samples, with the corrosion rate reduced from 3.693 to 0.967 μm year−1. Hemocompatibility of SS 316L was improved with reduced platelet adhesion when compared to the pristine sample.

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.

Magnetorheological finishing of small gear teeth profiles using novel workpiece fixture

Miniature gears are essential components of transmitting power in tiny motors used in the aviation, automobile, and healthcare sectors etc. Because of the intricacy of its shape, nanofinishing of tiny gear is a tough job. The rotational magnetorheological abrasive flow finishing (R-MRAFF) technique is a new hybrid methodology for the generation of nano-meter range surface finishing. These surfaces reduce friction between integrating parts, extending their life span. In the current study, a model for simulating the impacts of the R-MRAFF technique was developed using finite element (FE) analysis software, namely COMSOL® Multiphysics. The impacts of various process factors on the fluid flow characteristics while finishing the gear component are investigated using magnetostatic fluid flow analysis of magnetorheological polishing fluid (MRPF) in 3D computational domain of new workpiece fixture. To evaluate the forces operating in R-MRAFF technique, a viscosity model for MRP fluid flow around a complicated component (small steel gear) in an outside magnetic field is recognized and simulated. The magnetic field has a major impact on processing effectiveness by controlling the MRPF viscosity. During the polishing of the gear component, the surface finish attained at various places on working surfaces is uniform, which is confirmed by surface characterization of teeth profiles of small gear.

Effect of process parameters on machinability, hemocompatibility and surface integrity of SS 316L using R-MRAFF

Surface finish at nanometric scale is imperative for biomedical implants made up of stainless steel 316L (SS 316L) and titanium alloy to ensure the biocompatibility. However, such fine finishing is quite difficult to process. A rotational magnetorheological abrasive flow finishing process is used for nano-finishing. Rotational magnetorheological abrasive flow finishing (R-MRAFF) is one of the processes to achieve nano-level finishing. In this present study, a rotating die has been developed to perform the R-MRAFF processes with four rectangular-shaped permanent magnets held at an angle of 90° to one another. A new method for producing a variable magnetic field was investigated in this study by increasing or decreasing the distance between permanent magnets in the rotating die and workpiece fixtures. The increase in the distance between permanent magnets in rotating die and workpiece fixture leads to a decline in the value of material removal rate (MRR) as well as a percentage reduction in surface roughness (%ΔRa). This validates the importance of magnetic field intensity in the R-MRAFF process. A central composite design (CCD) in the response surface methodology (RSM) is employed to study the effect of process parameters on the response variables. The effect of the process parameter was evidenced with the help of the ANOVA technique. Optimization was carried out with constraints of maximizing both output response variables, the optimum MRR and %ΔRa, which were found as 2.02 mg/s and 50.66%. To quantify the effect of surface roughness on hemocompatibility, a platelet adhesion study was investigated. The platelet adhered area starts to decrease with the reduction in the surface roughness from 319 to 167 nm.

An overview of magnetorheological polishing fluid applied in nano-finishing of components

Surface quality is the most crucial factor affecting the product lifespan and performance of any component. Most earlier technologies display accuracy in the micrometre or submicrometre range, surface roughness in the nanometre range, and almost no surface defects in the production of optical, mechanical and electronic parts. Such finishing methods incorporate a magnetic field to control the finishing forces using magnetorheological fluid as the polishing medium. Magnetorheological fluid (MR) consists of ferromagnetic and abrasive particles. It is a type of modern intelligent fluid. An optimum selection of magnetorheological fluid constituents and their volume concentration plays an essential role for the ultra-fine finishing of newly developed engineering products. Rheological characteristics of magnetorheological fluid can change rapidly and effortlessly with the support of an activated magnetic field. Traditional finishing methods are comparatively inferior in finishing complex freeform surfaces, due to the lack of controlling finishing forces and limitations of polishing tool movement over the complex freeform contour of the components. There are different types of processes based on the magnetorheological fluid including magnetorheological finishing, magnetorheological abrasive flow finishing, rotational magnetorheological abrasive flow finishing and ball end magnetorheological finishing. This article discusses the development of different types of magnetorheological-fluid-based finishing processes and their modes of operation. The MR fluid devices developed in the last decade are thoroughly reviewed for their working principles, characteristics and applications. This article also highlights the study of rheological characterization of magnetorheological fluid and its applications in different polishing methods appropriate for finishing various complex freeform components.

CFD analysis of MR fluid applied for finishing of gear in MRAFF process

Small gears are an integral part of the transmission of power and other devices in the small machines which are employed in aerospace, automotive and medical industries etc. Nanofinishing of small gear is a difficult task due to the complexity in its geometry. The modern hybrid approach for the development of nano-scale surface finishing is magnetorheological abrasive flow finishing (MRAFF) method. These surfaces decrease friction among meshing components to improve the their service life. A model for simulating the effects of the MRAFF method was built in the current research study by using FEA based software i.e. (COMSOL® Multiphysics). Computational fluid dynamic (CFD) analysis of MR fluid in the 2D computational domain is conducted to see the effects of different process variables on the fluid flow properties (shear rate, shear stress, velocity profile) while finishing the gear component. To analyze the forces acting in the MRAFF method, a viscosity model for the magnetorheological polishing (MRP) fluid flow around a complex component (small steel gear) in external magnetic field is identified and simulated. The magnetic field significantly affects process efficiency by regulating the MR fluid viscosity. The surface finish achieved at various positions on the workpiece surface is consistent throughout the finishing of the gear component.

Optimization of process parameters in nano-finishing of Co-Cr-Mo alloy knee joint

ABSTRACT Process of obtaining a high surface finish value, say Ra value, with the lowest standard deviation on the freeform surfaces especially on knee joint using the conventional finishing processes is an exigent task. Achieving a throughout uniform surface finish using a process called Rotational Magneto-rheological Abrasive Flow Finishing (R-MRAFF) is found to be a suitable approach with a designed, developed, and fabricated tool as an inverse replica. An inverse replica of femoral as a tool used for finishing where the medium flow is almost constant (minimum possible variation in velocities). To optimize the parameters, an effort has been made for reducing the time and achieving the more consistent surface finish. Total finishing time is reduced from 64.7 h to 2.0 h with a very low standard deviation of the final Ra value range over the surface of femoral. The minimum roughness of 50 nm is obtained which was originally 190.5 nm.

Analysis of finishing forces and surface finish during magnetorheological abrasive flow finishing of asymmetric workpieces

Magnetorheological abrasive flow finishing (MRAFF) is an advanced hybrid process for producing ultrafine finished surfaces. Such surfaces reduce frictional forces and thereby minimize wear and tear to increase functional lifetime of the components. In the present research work, a model has been developed for simulating the results of MRAFF process. First, magnetic field is simulated and then a detailed study on the rheology of the magnetorheological polishing (MRP) fluid is conducted to develop a viscosity model for the flow of non-Newtonian shear thinning fluid. To calculate the forces acting in the process of material removal, the flow of MRP fluid around an asymmetric workpiece (knee joint) in a spatially varying magnetic field is simulated. Finishing forces exerted by the abrasive particles on the workpiece surface are analysed to develop a model for predicting surface roughness. A methodology has been proposed to evolve a variable correction factor to determine active abrasive particles at different locations on the workpiece surface for accurate simulation of surface finish operation. It is found that the magnetic field greatly influences the process performance by governing the viscosity of the MRP fluid and the distribution of the abrasive particles in the medium. During finishing of an asymmetric workpiece, the surface finish obtained at different locations on the workpiece surface is different. The developed model is capable to predict final surface finish within the acceptable accuracy when compared with the experimental results.

Abrasive Machining Techniques for Biomedical Device Applications

Abrasive machining and finishing processes are techniques of material removal that are introduced in order to cut workpiece materials with the nominal mechanical and thermal residual stresses. These processes utilize continuous material removal by abrasive medium that can be in forms of water, abrasive particles or a mixture of these two. The benefit of eliminating excessive mechanical cutting force results in enhanced cutting of brittle or soft materials. On the other hand, removal of thermal cutting source provides a capability of cutting plastics and diminished the chances of thermal cracking in workpiece. Abrasive finishing processes have been introduced as complementary to abrasive cutting techniques in order to increase the precision and surface quality of manufactured parts. The most common of these techniques are water jet machining (WJM), abrasive jet machining (AJM), abrasive water jet machining (AWJM) and magnetic abrasive machining processes such as magnetic abrasive finishing (MAF), magneto-rheological abrasive finishing (MRF) and magneto-rheological abrasive flow finishing (MRAFF).

Differential finishing of freeform surfaces (knee joint) using R-MRAFF process and negative replica of workpiece as a fixture

ABSTRACTIt is difficult and challenging to achieve uniform nanoscale surface finish in the contact zone, particularly on freeform (or sculptured) surfaces having different curvatures at different locations. Femoral (or, Knee joint component) is one of such biomedical freeform component which has complex profile along its curvature. Surface conditions of a femoral decide the life of the implant and they play a crucial role in its functionality. The variation in surface roughness of the femoral should be minimum in the contact zone. For this purpose, a special tooling is being proposed for rotational magnetorheological abrasive flow finishing (R-MRAFF) process. A negative replica of the workpiece (knee joint) as a tool (or a fixture) is used so that the medium flow velocity in the fluid flow channel is almost constant (or minimum possible variations) along the medium flow direction. It is able to do differential finishing also along the curvature. In addition, pulsating magnetic field has been used to generate vibrations in the medium in the finishing zone so that the possibility of fresh abrasive particles interacting with the surface of femoral is high. The surface finish has been achieved ranging from 26 nm to 62 nm using the proposed finishing technique and negative replica of the workpiece (femoral) as a fixture.

A review on magnetically assisted abrasive finishing and their critical process parameters

Magnetically assisted abrasive finishing (MAAF) processes are the precision material removal processes that have been applied to a large variety of materials from brittle to ductile and from magnetic to non magnetic. The MAAF process relies on a unique “smart fluid”, known as Magnetorheological (MR) fluid. MR fluids are suspensions of micron sized magnetizable particles such as carbonyl iron, dispersed in a non-magnetic carrier medium like silicone oil, mineral oil or water. The MAAF processes overcome the limitation of abrasive flow machining by deterministically control the abrading forces by applying magnetic field around the workpiece. MAAF process is divided into two parts; one is magnetorheological finishing (MRF) and another is magnetorheological abrasive flow finishing (MRAFF). The MRAFF process gives better results as compared to results of MRF because it has additional reciprocating motion of MR fluid. In this article the attempt has been made to review various technical papers related to MRF and MRAFF. The experimental setups, process parameters, MR fluid, modeling & optimization and applications are discussed in this paper. This review article will be useful to academicians, researchers and practitioners as it comprises significant knowledge pertaining to MAAF.

Experimental Investigations into Nano-finishing of Freeform Surfaces Using Negative Replica of the Knee Joint

To achieve high level of surface finish is a difficult task especially in complex shaped components, 3-D components and components with freeform (or sculptured) surfaces. Knee joint is one of such components which has freeform surfaces. Surface finish is very expensive and time consuming operation. Moreover, surface finish of a knee joint plays a crucial role in its functionality and life expectancy. The range of variation of surface roughness value on the different faces is required to be minimum. With these objectives in view, Rotational - magnetorheological abrasive flow finishing (R-MRAFF) process is being proposed with special tooling to achieve the above said objectives.To have uniform (or minimum variation) surface roughness values on all the four faces, a negative replica of the knee joint has been fabricated as a fixture so that the medium flow velocity is approximately constant throughout the length of the joint. Secondly, pulsating magnetic field is used to create vibrations in the abrasive particles so that the probability of new abrasive particles interacting with the knee joint surface, is high.

Prediction of Surface Roughness in Magneto Rheological Abrasive Flow Finishing Process by Artificial Neural Networks and Regression Analysis

In this study, to predict the surface roughness of stainless steel-304 in Magneto rheological Abrasive flow finishing (MRAFF) process, an artificial neural network (ANN) and regression models have been developed. In this models, the parameters such as hydraulic pressure, current to the electromagnet and number of cycles were taken as variables of the model.Taguchi’s technique has been used for designing the experiments in order to observe the different values of surface roughness . A neural network with feed forward with the help of back propagation was made up of 27 input neurons, 7 hidden neurons and one output neuron. The 6 sets of experiments were randomly selected from orthogonal array for training and residuals were used to analyze the performance. To check the validity of regression model and to determine the significant parameter affecting the surface roughness, Analysis of variance (ANOVA) and F-test were made. The numerical analysis depict that the current to the electromagnet was an paramount parameter on surface roughness.Key words: MRAFF, ANN, Regression analysis

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.

Nano-finishing techniques: a review

The quality of surface is one of the significant parameters which affects the life and functionality of any product. Many products require nano-level surface finish as their functional indispensability. Those processes having flexible finishing tool can be employed for such type of components. These finishing processes can be classified into two categories: with and without magnetic field assistance. The former includes magnetic abrasive finishing, magnetorheological finishing, and allied processes, and the latter includes abrasive flow finishing. This article reports the critical review of mainly three processes: abrasive flow finishing, magnetorheological finishing, and magnetorheological abrasive flow finishing. In this article, the issues that need attention of the researchers have been categorically mentioned. This article provides a comprehensive literature review of magnetorheological finishing process in terms of rheological characterization of magnetorheological fluid, experimental investigation, theoretical analysis, and applications. This article deals with various advancements in abrasive flow finishing and hybrid processes. The developments in magnetorheological abrasive flow finishing and its allied processes have been discussed in detail. By suitable modification of magnetorheological abrasive flow finishing process, it can achieve surface finish up to nano-meter on different materials such as brass, aluminium, stainless steel, and silicon-nitride.

The Out-of-Roundness of the Internal Surfaces of Stainless Steel Tubes Finished by the Rotational–Magnetorheological Abrasive Flow Finishing Process

This article reports the experimental findings about the improvement in out-of-roundness (OOR) of stainless steel tubes finished by Rotational–Magnetorheological Abrasive Flow Finishing (R-MRAFF) process. In this process, a rotating motion is provided to the magnetorheological polishing (MRP) medium by means of a rotating magnetic field, and simultaneously, a reciprocating motion is provided to the polishing medium by a hydraulic unit. By controlling these two motions, nano level uniform smooth mirror like finished surface has been achieved and simultaneously OOR of internal surface of tube is reduced. Experiments are planned according to the central composite rotatable design of response surface methodology based on the selected range of process parameters obtained from the preliminary experiments. Analysis of Variance (ANOVA) is conducted and contribution of each model term affecting OOR improvement is calculated. It has been found that R-MRAFF process potentially reduces roundness error of axisymmetric parts (maximum improvement in OOR=2.04 µm) improving their reliability and wear resistance. The present study shows that, OOR improves with an increase in the rotational speed of the magnet up to an optimum value beyond which the improvement in OOR reduces. From the scanning electron micrographs and atomic force micrographs it has been found that the abrasive cutting marks in R-MRAFF process generate cross-hatch pattern which helps in oil retention in cylindrical workpieces to reduce friction.

Parametric analysis of MR polishing fluid using statistical technique

Magnetorheological abrasive flow finishing (MRAFF) process has been developed for nanofinishing of parts especially for complicated geometry for a wide range of industrial applications. The finishing efficiency and finishing quality of MRAFF process relies mainly on the rheological properties (i.e., yield stress and viscosity) of magnetorheological polishing (MRP) fluid which must be characterised before it is used in any specific application. These properties are responsible for bonding strength of abrasive particles surrounding carbonyl iron particle (CIP) chains. Design of MRP fluid composition and volume ratio has an impact on rheological properties and stability directly. Response surface methodology (RSM) is applied to predict the effect of volume concentration of each component on yield stress and viscosity of MRP fluid.

NANO-FINISHING OF STAINLESS-STEEL TUBES USING ROTATIONAL MAGNETORHEOLOGICAL ABRASIVE FLOW FINISHING PROCESS

A new polishing method called Rotational (R)-Magnetorheological Abrasive Flow Finishing (MRAFF) process has been proposed by rotating a magnetic field applied to the Magnetorheological polishing (MRP) medium in addition to the reciprocating motion provided by the hydraulic unit to finish internal surface of cylindrical stainless steel (non-magnetic) workpiece. By intelligently controlling these two motions uniform smooth mirror-like finished surface in the range of nm has been achieved. For parametric analysis of the process, the experiments have been planned using design of experiments technique and response surface regression analysis is performed to analyze the effects of process parameters on finishing performance. Analysis of Variance (ANOVA) is conducted and contribution of each model term affecting percent improvement in surface finish is calculated. The experimental results are discussed and optimum finishing conditions are identified from optimization study. The present study shows that rotational speed of the magnet has most significant effect on output response (percentage improvement in surface roughness, %ΔR a ). The best surface finish obtained on stainless steel workpiece with R-MRAFF process is 16 nm.

A novel nanofinishing process using magnetorheological abrasive polishing fluid

Magnetorheological Abrasive Flow Finishing (MRAFF) is developed for finishing complex internal geometries up to nanometer level using Magnetorheological polishing (MRP) fluid which comprises of MR-fluid with fine abrasive particles dispersed in it. Experiments were conducted on stainless steel and silicon nitride workpieces using silicon carbide, boron carbide and diamond abrasives. The best surface finish obtained on the stainless steel workpieces with the present set-up configuration is 30 nm. The effect of number of finishing cycles, extrusion pressure and magnetic flux density is studied on change in surface roughness (Ra) value. Capillary magnetorheometer is designed and fabricated for rheological characterisation of MR-polishing fluid. Bingham plastic, Herschel Bulkley and Casson's fluid model are used to fit the obtained data points.