Ferromagnetic Workpiece Research Articles

Displacement measurement for ferromagnetic materials based on the double-layer parallel-cable-based probe

This paper introduces a magnetic displacement sensor comprising of a double-layer parallel cables (PCs) magnetizer, tunnel magnetoresistance (TMR) sensors and magnetic flux concentrating plates (MFCPs). By utilizing a double-layer PCs magnetizer, the background magnetic field in the TMR sensor’s location can be eliminated, while enhancing the magnetization field of the workpiece. This ensures that the highly sensitive TMR sensors operates within its measurement range. Additionally, the MFCPs concentrate the magnetic field at the TMR sensor location to further improve the displacement measurement sensitivity. After optimizing the geometry and excitation frequency of the probe with FEM, the probe can achieve displacement measurements with 0.1 mm accuracy in the range of 0.5–6.0 mm for ferromagnetic workpieces with linearity of 4.5 % and average relative error under 2.0 %.

Influence of Process Parameters and Initial Surface on Magnetic Abrasive Finishing of Flat Surfaces on CNC Machine Tools

Magnetic abrasive finishing (MAF) shows a high potential for use on computerized numerical control (CNC) machine tools as a standard tool to polish workpieces directly after the milling process. This paper presents a new MAF tool with a single, large permanent magnet and a novel top cover structure for finishing the plain ferromagnetic workpieces. The top cover structure of the MAF tool, combined with an optimized working gap, ensures the effect of mechanical powder compaction, which leads to a significant increase in process capability and surface roughness reduction. The influence of the process parameters such as feed rate, equivalent cutting speed, working gap (including for three grain sizes) and the gap to the magnet was investigated. In addition, the influence of the initial surface after face milling, end milling, ball end milling and grinding on the surface quality after MAF was investigated. Furthermore, three typical surfaces after milling and MAF were analyzed. By magnetic abrasive finishing, a significant surface quality improvement of the initial milled surfaces to roughness values up to Ra = 0.02 µm and Rz = 0.12 µm in one processing step could be achieved.

In-situ Evaluation of Surface Integrity Modifications by means of Barkhausen Noise Measurement

The quality and functionality of machined parts depend on their dimensional tolerance as well as on the mechanical properties of the workpiece rim zone, which are summarized as surface integrity. Thermo-mechanical loads induced by the cutting process into the rim zone often lead to an undesirable workpiece material modification. Over the last decades, many researches focused on the process monitoring of properties of the rim zone, such as the grain size or the residual stress profile. In order to prevent damage to the workpiece material, non-destructive and magnetic measurement methods are to be favored when machining ferromagnetic workpiece materials. Due to its sensitivity to the microstructural properties of ferromagnetic materials, Barkhausen Noise (BHN) measurement offers the potential for in process monitoring. In particular, BHN shows a strong correlation with the residual stress state of the workpiece material and thus the direct obtainment of BHN signals in the cutting process enables the in-situ modelling of residual stress changes in the rim zone.In this paper, two BHN measurement test benches were developed in order to investigate a first correlation between process parameters, measuring conditions and resulting BHN signals when machining quenched and tempered AISI 4140 steel. Furthermore, a first correlation between residual stress states and BHN signals obtained in the orthogonal cutting process is presented.

Modelling of transient behaviour of roughness reduction in ball end magnetorheological finishing process

Ball end magnetorheological finishing (BEMRF) process provides nano level of surface finish for materials which are magnetic as well as non-magnetic in nature. The available literature on this process has been vastly limited to establishing its finishing capabilities on materials of different nature. This research work deals with theoretical investigations into surface roughness reduction in BEMRF process, performance of machining parameters during long time periods and providing their representation in mathematical terms. Starting with the mechanism of abrasive wear in BEMRF process, this work advances to find out prolonged effect of abrasive rubbing on a ferromagnetic workpiece surface. The study finds out a phenomenon termed as transient roughness reduction in which the material removal by abrasive wear in BEMRF process is diminished with time and a particular combination of machining parameters and fluid composition reduce roughness only up to a critical value, beyond which no further reduction is achieved. A mathematical model is developed to depict this transient roughness reduction phenomenon, the model is then experimentally verified and the close proximity of the experimental results with the theoretical ones validates the model and the transient roughness reduction phenomenon in BEMRF process.

Modelling of transient behaviour of roughness reduction in ball end magnetorheological finishing process

Ball end magnetorheological finishing (BEMRF) process provides nano level of surface finish for materials which are magnetic as well as non-magnetic in nature. The available literature on this process has been vastly limited to establishing its finishing capabilities on materials of different nature. This research work deals with theoretical investigations into surface roughness reduction in BEMRF process, performance of machining parameters during long time periods and providing their representation in mathematical terms. Starting with the mechanism of abrasive wear in BEMRF process, this work advances to find out prolonged effect of abrasive rubbing on a ferromagnetic workpiece surface. The study finds out a phenomenon termed as transient roughness reduction in which the material removal by abrasive wear in BEMRF process is diminished with time and a particular combination of machining parameters and fluid composition reduce roughness only up to a critical value, beyond which no further reduction is achieved. A mathematical model is developed to depict this transient roughness reduction phenomenon, the model is then experimentally verified and the close proximity of the experimental results with the theoretical ones validates the model and the transient roughness reduction phenomenon in BEMRF process.

Coupled thermo-electromagnetic model of a new robotic high-frequency local induction heat treatment system for large steel components

A new robotic high-frequency local induction heat treatment system is studied. The system is designed to perform on-site local heat treatment on large steel components such as hydropower turbine runner. A flat spiral coil is moved by a robot arm over the area to treat. A fast numerical model is developed to predict the temperature distribution and system settings. Several numerical strategies are proposed to minimize the computation time. The model combines an equivalent circuit with thermal finite elements and the electromagnetic mutual impedance method. A simple approach based on the concept of complex permeability is proposed to model hysteresis losses. The computed power losses in the RLC circuit and the temperature field in flat paramagnetic and ferromagnetic workpieces are compared with experimental measurements. Results confirm the accuracy of the coupled thermo-electromagnetic model.

Analysis of the surface roughness for novel magnetorheological finishing of a typical blind hole workpiece

In modern high-performance machinery, parts which are highly finished and dimensionally accurate play a vital role. Surface finish enhances characteristics like wear, corrosion, pitting, and oxidation resistance of the surfaces. A novel magnetorheological polishing process using permanent magnets is developed to finish the internal cylindrical and bottom surfaces of the blind hole cylindrical workpiece. The process is capable of finishing the internal cylindrical and flat bottom surfaces of tubular and nontubular-shaped blind hole workpiece. Finishing of blind hole surfaces finds extensive application in dies and automotive components such as automobile actuators, cylinder body, valve seats, etc. In this study, two different tools for finishing the internal and flat bottom surfaces of blind hole cylindrical workpiece have been developed. The causal factor for material removal in the form of microchips is abrasive wear. The present study focuses on the calculation of forces acting on abrasive particles and mathematical modeling and simulation of the surface roughness. The performance of both newly developed tools for finishing the cylindrical blind hole mild steel workpiece is evaluated. After 275 finishing cycles, the Ra values improved by 55.2% in the internal cylindrical ferromagnetic workpiece and by 53.33% after 75,000 cycles on the flat surface of ferromagnetic blind hole workpiece. The theoretical and experimental values of the surface roughness are found to be consistent. The experimental surface roughness values of blind hole internal cylindrical surfaces are within 6.26% of the theoretical values, whereas in finishing the blind hole bottom surface it is found within 7.9% of the theoretical values.

Improved design of magnetorheological honing tool based on finite element analysis and experimental examination of its performance

The magnetorheological honing (MRH) tool is an advanced finishing tool which is designed and developed to superfinish internal cylindrical surfaces. It uses magnetorheological polishing fluid consisting of carbonyl iron particles and cutting-edge silicon carbide abrasives in viscous fluid medium. The MRH tool with retained polishing fluid is rotated and reciprocated inside a cylindrical workpiece within the gap between the outer surface of the MRH tool and the inner surface of the cylindrical workpiece called the working gap. Due to the relative motion between abrasives (gripped by carbonyl iron particles chains) and the workpiece’s inner surface, finishing action takes place over the inner surface of the cylindrical workpiece. In this paper, two different designs of the MRH tool are designed with the same parameters based on finite element (FE) analysis using Ansoft Maxwell. The FE analysis results in more magnitude and uniformity of magnetic flux density in the working gap for the improved design of the MRH tool. Due to this effect, the abrasives are more strongly held with uniform strength which results in comparatively significant uniform finishing of the internal surface of the cylindrical workpiece. After confirmation of higher and uniform magnetic flux density on the improved MRH tool surface from FE analysis, two designs of the MRH tool are then fabricated with the same dimensions as taken in magnetic simulation. Experimentations have been performed with the fabricated finishing tools over the inner surface of cylindrical ferromagnetic workpiece of mild steel. The MRH tool with improved design results in uniform and more reduction in value of surface roughness with the same finishing time and process parameters as compared to the first proposed design. This confirms the enhancement in the finishing capability and better usefulness of the improved design of the MRH tool.

Development of magnetorheological fluid-based process for finishing of ferromagnetic cylindrical workpiece

ABSTRACTA magnetorheological fluid-based process is developed for the internal surface finishing of ferromagnetic cylindrical workpiece. The existing finishing processes based on magnetorheological fluid are not equipped to finish the internal ferromagnetic cylindrical surface significantly as it obtained higher magnetic flux density than the MR polishing fluid. At present, magnetorheological fluid-based finishing tools are designed to ensure the maximum magnetic flux density always present on the outer finishing tool core surface as compared to internal surface of ferromagnetic cylindrical workpiece surface. To validate this present principal idea, the magnetostatic finite element analysis has been performed on the newly designed finishing tools. The preliminary experiments have also been conducted to evaluate the finishing performance with the two newly designed finishing tools. The percentage reduction in surface roughness (Ra) values with I-shaped tool core is found as 65–78% after 150 min of finishing, whereas, with rectangular shaped tool core is found as 78–81% after 90 min of finishing. The results clearly revealed that the present finishing tool with rectangular shaped core is more suitable for uniform significant finishing of ferromagnetic cylindrical internal workpiece than the I-shaped core. The developed process can be useful in finishing of cylindrical mold and dies, hydraulic cylinder, barrel for injection molding, etc.

Reprint of ‘‘Modeling of surface roughness in ball end magnetorheological finishing (BEMRF) process’’

A new precision finishing process called the ball end magnetorheological finishing (BEMRF) process was developed for super finishing of complex 3D surfaces. This process is based on magnetorheological polishing (MRP) fluid whose rheological behaviour varies with the magnitude of the applied magnetic field. The magnetically energized MRP fluid is used at the tip of a rotating tool to finish workpiece of different materials and shapes. The MRP fluid is a mixture of abrasives and magnetizable carbonyl iron particles (CIP) in a carrier medium. To improve the in-depth understanding of the BEMRF process, this work deals with the theoretical investigations into modeling of surface roughness and mechanism of material removal associated with ferromagnetic workpiece. Since it is very difficult to understand the complex structure of the magnetically energized MRP fluid during finishing operation, microstructure of the constituents of the MRP fluid has been proposed. A theoretical model of magnetically induced normal and shear forces acting on the abrasive is also proposed in the present study. Based on these forces, the material removal process and wear behaviour during finishing operation have been analyzed. While the normal force model explains the penetration of abrasives into the workpiece surface, the shear force model aids in the understanding of three body wear mechanism between the abrasives and the workpiece surface. A mathematical model has been developed to evaluate the surface roughness. Using the developed model, the theoretical value of surface roughness is computed. The close agreement of theoretical and experimental results validates the proposed model.

Modeling and simulation of surface roughness in magnetorheological fluid based honing process

A newly magnetorheological fluid based honing process is developed for internal surface finishing of ferromagnetic cylindrical workpiece as existing magnetorheological fluid based finishing processes are not found suitable to finish the ferromagnetic internal surfaces. The performance of the present developed finishing process in terms of reduce wear and improve the functional application of cylindrical components, mainly depends on the normal force acting on abrasive particles due to magnetic behavior of carbonyl iron particles in magnetorheological polishing fluid. Also, it depends on shear force acting on surface by abrasive particles due to translational and rotational motion of tool as similar to the honing operation. For the newly developed finishing process, the modeling of surface roughness with the effect of induced magnetic field and magnetic normal force for different finishing cycles have been proposed. To validate the model and understand the wear mechanism during finishing, the experiments have been performed on the internal surface of cylindrical ferromagnetic workpiece with the three different sets of finishing cycles. The surface roughness of cylindrical workpiece has experimentally measured with Mitutoyo SJ-400 surftest. Also, to understand wear mechanism during finishing, the scanning electron microscopy has been performed. The theoretical calculated values of surface roughness with number of finishing cycles are validated with experimentally obtained surface roughness values for the same number of finishing cycles and conditions. Both were found in close agreement within 5.88%. Thus, the present developed finishing process is found suitable to reduce wear on internal surface of cylindrical components which leads to saving in service, energy consumption, maintenance costs, and improves its functional applications as compared to traditional finishing techniques.

Spot nanofinishing using ball nose magnetorheological solid rotating core tool

The spot nanofinishing of surface plays an important role for improving the surface quality of miniature mechanical, electronics, and optics components. The nano-level finishing of these miniature components is highly demanded in today’s industry to fulfill the operational and functional requirement. The principal innovation of the present work is generating uniform magnetic field at the end of a magnetizable rotating core tool for providing a uniform surface roughness on a spot finishing of precision components. To fulfill this requirement, a ball nose magnetorheological nanofinishing process based on solid rotating core tool is developed. The existing ball end magnetorheological finishing (BEMRF) process uses a rotating core with central hole for flow of polishing fluid at the tool end surface. Due to central hole inside the rotating core, a non-uniform magnetic flux density has been experienced at the tool end surface which may result in non-uniform surface roughness in spot finishing, i.e., on a fixed location without any X-Y-axis linear feed rates. The magnetostatic finite element analysis clearly revealed the uniform magnetic flux density at the end surface of the solid rotating core tool than existing BEMRF tool core having central hole. The experimentation has been carried out for spot finishing on ferromagnetic workpiece surface in order to study the variation in surface roughness values. The present ball nose magnetorheological finishing process with solid rotating core tool produced uniform average surface roughness values as 20 nm from 290 nm after 90 min of spot finishing on the ferromagnetic workpiece surface. The experimental results confirmed the effectiveness of generating uniform magnetic field at the end of a magnetizable rotating core tool for a spot uniform nanofinishing of precision components.

A novel magnetorheological honing process for nano-finishing of variable cylindrical internal surfaces

ABSTRACTA novel magnetorheological honing process is designed and developed for nano-finishing of cylindrical internal surfaces with the help of permanent magnets. The radial movement of magnetic tool surface is adjusted as per the internal diameter of different cylindrical components and make it fixed before start of finishing so that it can maintain constant working gap while perform finishing. The present developed magnetic tool surface always constitutes higher magnetic field than the inner surface of ferromagnetic or non-ferromagnetic cylindrical workpiece. This is an important requirement to finish the internal surface of ferromagnetic or non-ferromagnetic cylindrical components because it ensures MR polishing fluid cannot stick on the workpiece surface while performing the finishing. Hence, present developed process is useful for finishing of ferromagnetic cylindrical molds, dies, hydraulic actuators, etc. for its better functional applications after the conventional honing or grinding process. The internal surface roughness of cylindrical ferromagnetic workpiece is dropped to 90 nm from its initial value of 360 nm in 100 minutes of finishing. Further scanning electron microscopy has also been done to understand the surface characteristics of finished workpiece. The results revealed that the developed magnetorheological honing process is capable to perform nano-finishing of internal surface of the ferromagnetic cylindrical components.

Modeling of surface roughness in ball end magnetorheological finishing (BEMRF) process

A new precision finishing process called the ball end magnetorheological finishing (BEMRF) process was developed for super finishing of complex 3D surfaces. This process is based on magnetorheological polishing (MRP) fluid whose rheological behaviour varies with the magnitude of the applied magnetic field. The magnetically energized MRP fluid is used at the tip of a rotating tool to finish workpiece of different materials and shapes. The MRP fluid is a mixture of abrasives and magnetizable carbonyl iron particles (CIP) in a carrier medium. To improve the in-depth understanding of the BEMRF process, this work deals with the theoretical investigations into modeling of surface roughness and mechanism of material removal associated with ferromagnetic workpiece. Since it is very difficult to understand the complex structure of the magnetically energized MRP fluid during finishing operation, microstructure of the constituents of the MRP fluid has been proposed. A theoretical model of magnetically induced normal and shear forces acting on the abrasive is also proposed in the present study. Based on these forces, the material removal process and wear behaviour during finishing operation have been analyzed. While the normal force model explains the penetration of abrasives into the workpiece surface, the shear force model aids in the understanding of three body wear mechanism between the abrasives and the workpiece surface. A mathematical model has been developed to evaluate the surface roughness. Using the developed model, the theoretical value of surface roughness is computed. The close agreement of theoretical and experimental results validates the proposed model.

Development of novel magnetic grippers for use in unstructured robotic workspace

The workability of an industrial robotic system under non-coherent environment has attained commendable potential in recent era owing to the customized design of end-effectors. Magnetic gripping is one such domain that draws research interest, especially when used in unstructured robotic workspace. The present paper delineates the details of the design, modeling, analysis, fabrication paradigms and test results of representative magnetic grippers, including test-pieces and prototype, having provision for augmentation with industrial robot(s). The novelty of the present research lies with the design semantics of the various layouts of the magnetic gripper for a customized operation of lifting ferromagnetic work-pieces from an unstructured heap, made through Finite Element Analysis (FEA) as well as using contact mechanics-based grasp synthesis model. The test grippers were experimented using an indigenous laboratory set-up, working under both structured and unstructured environments. The prototype development of the sensor-instrumented magnetic gripper was made in-line with the test results and its workability under unstructured workspace was tested by deploying the robotic unit in an industrial shop floor.

Analysis of workpiece magnetisation on liquid nugget during resistance spot welding

This paper investigates the effect of workpiece magnetisation on the magnetic flux density and nugget shape during resistance spot welding (RSW) process. To this end, this paper analyses the magnetisation process of ferromagnetic workpieces. The magnetisation was calculated by the equivalent surface current. The effect of magnetisation on the nugget shape was studied for RSW of steel and a specially designed aluminium workpiece. The results show that the magnetisation of ferromagnetic workpieces will increase the dimensions of the weld nugget in the thickness direction. The magnetic flux density induced by workpiece magnetisation and that induced by welding current have the same order of magnitude (10−1 T). This indicates that the magnetisation of ferromagnetic workpiece is an important source of magnetic force acting on liquid nugget. Therefore, it should not be ignored in studying the physics of RSW process, especially for the fluid flow in RSW of ferromagnetic materials.

DESIGN OPTIMIZATION OF A NOVEL MAGNETIC SWITCHABLE DEVICE BASED ON HALBACH ARRAY

The paper deals with the design and optimization of a novel magnetic switchable device based on Halbach array. The magnetic fleld in air gap is adjustable by rotating the center axis of adhesion mechanism so that the magnetic adhesion force is variable, and it is convenient for device to adsorb on and detach from the ferromagnetic workpiece or surface. The magnetic fleld model is established by Fourier series method, and the optimal dimensions of conflguration are obtained by genetic algorithms for best performing design. The magnetic force of novel optimal device is measured, and a good agreement between simulation and measurement is found. The results are compared to the traditional mechanism, and it is shown that the utilization ratio of magnets of novel optimal mechanism is 2.2 times larger than the H-type one with the same usage of magnets, while its consumption of soft iron is only 12.7% of the H-type one.

Mechanism of material removal in ball end magnetorheological finishing process

Ball end magnetorheological finishing (BEMRF) process was developed for finishing flat and 3D workpiece surfaces. A finishing tool is used to flow pressurized magnetorheological polishing fluid through the center of the rotating tool core and gets stiffened in the form of a magnetically controlled ball end shape at the tip surface of the tool. This forms a polishing spot of controlled size and shape which is used as a finishing medium by guiding it to follow the surface to be finished through computer controlled 3-axes motion. In the present study, an attempt has been made to understand the material removal and surface finishing mechanism in BEMRF process on a ferromagnetic workpiece. Based on experimental observations and force measurements, a mathematical model has been developed for modelling of magnetic field-induced normal force during finishing by BEMRF process. It is very difficult to understand the complex structure of rotating MR-polishing fluid during finishing operation, so a model of magnetic normal force is developed based on certain assumptions. Finished surfaces were also analyzed using scanning electron microscope (SEM) and atomic force microscope (AFM) to understand mechanism of material removal. In order to understand the material removal process and wear behavior during finishing, different modes of abrasive-workpiece interaction have been analyzed with respect to measured magnetic normal forces. The developed mathematical model has been used to predict magnetic normal finishing force and compared with the experimentally obtained results. Both were found in close agreement. The effect of variation in magnetic normal force was also observed experimentally in terms of percentage change in surface roughness during finishing.

Parametric analysis of an improved ball end magnetorheological finishing process

A novel surface finishing method using an improved ball end magnetorheological finishing tool was developed for nanofinishing of flat, as well as three-dimensional workpiece surfaces. An improved magnetorheological finishing tool is the main part of the present finishing process, which has been made up of the central rotating core and stationary electromagnet coil integrated with a copper cooling coil. A magnetically generated ball end finishing spot of magnetorheological polishing fluid was used as a finishing segment at the tip surface of the rotating core. In this research, detailed study through statistical design of the experiments was conducted for nanofinishing of ferromagnetic workpieces by the proposed ball end magnetorheological finishing process. Response surface methodology has been used to plan and analyze the effect of rotational speed of the tool core, magnetizing current and working gap on percentage change in surface roughness. The experimental results were discussed and the best finishing conditions were identified within the experimental range of variables. Analysis of experimental data showed that the percentage change in surface roughness was highly influenced by the working gap, followed by magnetizing current and rotational speed of the tool core. The best surface finish obtained on the ferromagnetic workpieces was as low as 27.6 nm from the initial value of 142.9 nm in 30 min of finishing time. In order to study the finished surface morphology, scanning electron microscopy and atomic force microscopy were also conducted.

Nanofinishing of a typical 3D ferromagnetic workpiece using ball end magnetorheological finishing process

A nanofinishing process using ball end magnetorheological (MR) finishing tool was developed for finishing 3D workpiece surfaces. In this process a ball end shape of MR polishing fluid is generated at the tip surface of the rotating tool which is used as a finishing spot. This paper is focused on surface finishing and performance evaluation of a typical three-dimensional ferromagnetic workpiece using a ball end magnetorheological finishing process. A typical 3D workpiece surfaces were made by milling process at different angles of projection such as flat, 30°, 45° and curve surfaces. The experiments were performed on these typical workpiece surfaces by ball end MR finishing setup to study the effect of number of finishing passes on final surface roughness. The experiments were also performed on a flat ground surface to study the process performance as compared with the milled workpiece surfaces. The finite element analysis has been done to study the distribution of magnetic flux density at tip surface of the tool with an inserted typical 3D workpiece surfaces. When these typical workpiece surfaces were finished by proposed MR finishing process, the surface roughness were reduced as low as 16.6nm, 30.4nm, 71nm and 123.7nm respectively on flat, 30°, 45° and curve surfaces for 60 passes of finishing. The roughness of flat ground surface was reduced as low as 19.7nm for 120min of finishing. The experimental results demonstrated that the newly developed ball end magnetorheological finishing process was effective in finishing typical 3D ferromagnetic workpiece surfaces.