Magnetic Normal Force Research Articles

Deep drawing formability of AZ31 magnesium alloy based on magnetorheological elastomer support

AbstractIn this paper, the flexible support mould is designed by using magnetorheological elastomer (MRE) to assist in the deep‐drawing of magnesium alloys. Based on the magnesium alloy mechanical tensile test and magnetorheological elastomer regular force experiments, the deep‐drawing process of AZ31 magnesium alloy supported by support mould was numerically simulated by finite‐element analysis software ABAQUS. By varying the current input to the excitation coil to change the magnetic induction intensity and thus adjust the magnetic normal force of the magnetorheological elastomer, then using magnetic normal force to complete the auxiliary sheet metal deep‐drawing. The results show that, compared with the unsupported mould, the supported mould can effectively reduce the maximum thinning rate of magnesium alloy on the original basis, thus effectively increasing the ultimate depth of magnesium alloy deep‐drawing. It can replace the original buffer device, effectively solution the problem of pulling and cracking at the bottom of magnesium alloy caused by the original excessive damping force, and improve the yield rate of workpiece.

Accurate Subdomain Model for Computing Magnetic Field of Short Moving-Magnet Linear Motor With Halbach Array

This article presents an accurate analytical model to compute the magnetic field in a short moving-magnet linear motor with any pole and slot combinations. Two kinds of end effects caused by the finite length of the stator and mover are considered. The stator end effect is addressed by an equivalent slotting subdomain based on the subdomain analytical method. The mover end effect is analyzed with a virtual mover consisting of the mover and two additional virtual units. The length of virtual unit is given according to the effective motion stroke and magnetic circuit, and the remanence of permanent magnets in virtual units is specified as zero. A linear motor with 8 poles/6 slots and a Halbach array is used to verify the correctness of the proposed analytical model. Compared with the results from the finite-element analysis and previous subdomain analytical model, the proposed analytical model shows high accuracy on the calculations of the magnetic flux density, cogging force, and normal magnetic force.

Analysis of surface finishing mechanism in a newly developed rotational magnetorheological honing process for its productivity improvement

In modern industries, nano-finishing of a part with high precision and dimensional accuracy is a crucial requirement. The finished surface of an industrial component improves the features such as appearance, resistance to abrasion which guards against wear, corrosion and chemical damages of the surfaces. A permanent magnet based rotational magnetorheological honing (R-MRH) process is developed for improving the productivity of internal surface finishing of the ferromagnetic cylindrical workpieces. In this process, the motion of the cylindrical workpiece is also simultaneously performed in opposite direction of the rotational motion of the magnetorheological honing tool unlike to the existing conventional as well as the magnetorheological honing processes. Finishing the internal surface of the cylindrical workpieces through R-MRH process leads to more saving in power consumption, improvement in productivity and increase in its functional applicability as compared to the existing magnetorheological honing technique. The normal magnetic force acting on the abrasive particle through the magnetic carbonyl iron particles is responsible for the indentation of abrasive onto the finishing surface. As the indented abrasive particle performs relative motion against the finishing surface of the workpiece, the ploughed materials get removed in the form of microchips due to the shear force acting on it. In the present work, workpiece rotation in the opposite direction of the MRH tool rotation results in increased relative speed and number of interacting abrasive particles with the fresh edge. The increased relative speed of the indented active abrasive particles causes a higher rate of wear of ploughed material. This results in a higher production rate and finishing capability. For the developed R-MRH process, a model of surface roughness has been proposed. The developed model has been experimentally validated with the different sets of finishing cycles. The scanning electron microscopy is performed to have a better understanding of finished surface patterns. The theoretically calculated surface roughness and experimentally obtained surface roughness is compared and both the values are found with the agreement within the error of 3.33–5.92%. The present developed R-MRH process is found to be suitable for nano-finishing of the internal surface of cylindrical components in reduced finishing time.

A New Version of Normal Magnetic Force Particles in 3D Heisenberg Space

In this study, we investigate new type of normal magnetic force biharmonic particles associated with a magnetic field $$\mathcal {B}$$ defined on Heisenberg space. Firstly, we consider a moving charged biharmonic particle under the action of a normal force $$\mathbf {N}$$ in the magnetic field $$\mathcal {B}.~$$ Then, we assume that trajectories of the particle associated with the magnetic field $$\mathcal {B}$$ correspond to normal magnetic force ( $$\mathbf {N}_{\mathbf {f}}$$ ) biharmonic particles of magnetic vector field $$\mathcal {B}$$ on 3D Heisenberg space.

Modelling of surface roughness in a new magnetorheological honing process for internal finishing of cylindrical workpieces

A new magnetorheological honing (MRH) process has been developed for internal surface finishing of cylindrical workpieces with different diameters. The process makes use of the tool with radial polarized curved permanent magnet strips and a smart magnetorheological (MR) polishing fluid for finishing the internal surface of the cylindrical workpieces. The MRH tool has the uniqueness that its radial curved permanent magnets can move inwards or outwards just like a honing tool so that the different diametric sizes of the internal surface of the cylindrical components can be finished. In the present work, a mathematical model has been developed for predicting the change in surface roughness while finishing the internal surface of ferromagnetic cylindrical workpieces. An analytical approach is adopted to evaluate the magnitude of magnetic flux density at different points in the working gap where MR polishing fluid is present. While finishing the internal surface of ferromagnetic cylindrical workpieces, a magnetic field is also contributed in the working gap due to the effect of iron particles (present in the MR polishing fluid) and the ferromagnetic cylindrical workpiece. The present developed mathematical model evaluates the magnitude of magnetic flux density in the working gap by also considering the contribution of the magnetic effect of iron particles and the ferromagnetic cylindrical workpiece. Theoretically calculated magnetic flux density distribution in the working gap is validated with the experimentally and also through finite element (FE) analysis using Maxwell Ansoft V13 software. With the evaluated values of magnetic flux density at various points in the working gap, the magnetic normal force exerting over the active silicon carbide (SiC) particle has been evaluated. The computed magnetic normal force exerting over the active SiC particle is utilized to calculate the removal of material in terms of decrease in surface roughness values with various finishing cycles. Also, the developed mathematical model for the present MRH process has been validated by performing the experimentations with same parameters and conditions as selected in modeling for the different number of finishing cycles. Results acquired from the mathematical model are found in close relation to the results obtained from experimentations with the maximum percentage error of 8.06% and least of 1.03%. The developed mathematical model for MRH process can be used to predict the process's finishing performance for various ferromagnetic cylindrical workpieces which can make it useful for industries.

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.

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.

Experimental study and empirical modelling of magnetic abrasive finishing on ferromagnetic and non-ferromagnetic materials

Magnetic abrasive finishing is one of the advanced finishing processes where in the iron (Fe) particles form a flexible matrix in which the abrasives are trapped when magnetic field is applied. In the present paper, the magnetic flux densities (MFD) are measured at various distances from the outer surface to centre on ferromagnetic and non–ferromagnetic materials with approximately same hardness. MFD is about three times higher on ferromagnetic compared to non–ferromagnetic workpiece. Complete experimental study is carried out and empirically modelled. Best final Ra value about 20 nm and 60 nm is achieved on ferromagnetic and non–ferromagnetic stainless steel, respectively. With increase in abrasive mesh size and decrease in working gap, percentage change in Ra (%ΔRa) increases. Online measurement of forces is done using indigenously developed ring type dynamometer. Normal magnetic force is much higher in case of ferromagnetic than non–ferromagnetic workpiece material but no significant change is found in tangential cutting force.

ABRASIVE-BASED NANO-FINISHING TECHNIQUES: AN OVERVIEW

The surface finishing techniques can be divided into two categories: traditional and advanced. To overcome some of the problems of traditional finishing techniques, hybridized processes have been evolved by the researchers. Some of the advanced finishing processes that have been reviewed are abrasive flow machining (AFM), magnetorheological finishing (MRF), magnetorheological abrasive flow finishing (MRAFF), magnetic abrasive finishing (MAF), chemo mechanical polishing (CMP), etc. Most of these processes have been developed in the recent past and they can be employed to produce optical, mechanical, and electronic components with micrometer or sub-micrometer form accuracy and surface roughness within nanometer range with hardly any surface defects. However for large size flat components, MAF seems to be the most suitable finishing process. In MAF, DC power supply is given to the electromagnet hence intermixing of ferromagnetic abrasive particles during the process does not take place and the worn out cutting edges keep interacting with the workpiece surface. As a result, the finishing rate is quite low. The use of pulsed DC power supply to the electromagnet results in pulsating flexible magnetic abrasive brush (P-FMAB), which substantially enhances the finishing rate. The on-line measurement of the forces has helped in understanding the mechanism of material removal during Static-FMAB (S-FMAB) and Pulsating-FMAB. The magnitude of normal magnetic force (originating indentations) in P-FMAB has been found to be dynamic in nature and substantially high in magnitude as compared to S-FMAB.

ANALYSIS OF PERFORMANCE OF PULSATING FLEXIBLE MAGNETIC ABRASIVE BRUSH (P-FMAB)

Direct current magnetic abrasive finishing process provides hardly any stirring effect on static flexible magnetic abrasive brush (S-FMAB). Continuous use of S-FMAB and absence of stirring leads to dullness of abrasive cutting edges resulting in low finishing rate. To overcome this weakness of the process, the FMAB has been made pulsating using pulse direct current (DC) power supply. Empirical models have been developed to study the effects of pulse on-time, and duty cycle on: (i) percent decrease in Ra value , (ii) normal magnetic force, (iii) cutting force, and (iv) force ratio. A correlation between surface finish and magnetizing energy has been evolved. The use of the pulse DC power supply to the electromagnet has enhanced surface finish many folds as compared to the surface finish achieved by the use of DC power supply. This improvement in surface finish seems due to the formation and destruction of FMAB during on-time and off-time of the pulse power supply, respectively.

Experimental investigations into forces acting during a magnetic abrasive finishing process

A magnetic abrasive finishing (MAF) process is the one in which material is removed in such a way that surface finishing and deburring are performed simultaneously with the applied magnetic field in the finishing zone. Knowledge of forces acting during MAF is important to understand the mechanism of material removal. Forces have direct influence on the generation of a finished surface and accuracy of the workpiece. This paper reports the experimental findings about the forces acting during MAF and provides correlation between the surface finish and the forces. The resistance type force transducer (ring dynamometer) has been designed and fabricated. It is used to measure the normal magnetic force component responsible for microindentation into the workpiece and tangential cutting force component producing microchips. The force data have been recorded on-line by making use of virtual instruments (using Lab-View software). It is concluded that forces and change in surface roughness (ΔRa) increase with increase in current to the electromagnet (or magnetic flux density) and decrease in the working gap.

Evaluation of the normal force of a planar actuator

This paper describes a method to compute the normal force between the mover and stator of an electromagnetic planar actuator. The method is based on the Maxwell stress tensor and depends on the resulting magnetic field. The actuator has a mover with two permanent magnets and a ferromagnetic stator covered by two orthogonal armature coils. The mover relies on a suspension system with linear bearings that enable bi-directional motion. When one permanent magnet is located over an excited coil phase, a magnetic propulsion force will act on the mover and that pushes the latter accordingly. A normal magnetic force is an intrinsic effect and determines the mechanical load the suspension system sustains. It represents an attraction force between the permanent magnets and the armature core that may affect the mechanical structure of the actuator and its movement.

Torque and unbalanced magnetic force in a rotational unsymmetric brushless DC motors

The pole-teeth-winding configuration in brushless dc motors determines torque and unbalanced magnetic force which are the resultants of the tangential and the normal magnetic force in a small air gap, respectively. This paper calculated torque and unbalanced magnetic force using FEM, Maxwell stress tensor to investigate the influence of pole-teeth-winding patterns on the performance from two common designs, i.e. the rotational symmetric 12-pole 9-tooth (12P9S) motor and the rotational unsymmetric 8-pole 9-tooth (8P9S) motor, and proposed the rotational unsymmetric 10-pole 9-tooth (10P9S) motor which achieves the high average torque of 12P9S motor and the low cogging torque of 8P9S at the same time. The analyses show that 8P9S and 10P9S motor tend to have less cogging torque because their bigger values of the least common multiple of pole and teeth reduce the cogging torque. The torque efficiency depends on pole-teeth-winding configuration. ABC-winding of 12P9S motor and three consecutive teeth winding of 10P9S motor utilize all six energized coil effectively to produce the high average torque. The normal magnetic force in a rotational unsymmetric design is not balanced and results in unbalanced magnetic force.