Abstract: A system for sensing and controlling concentration of magnetic particles in magnetorheological fluid comprising a wire coil and an AC voltage generator that, when energized, creates a magnetic flux field including a fringing field. When the fringing field extends through the magnetorheological fluid, the impedance in the circuit is proportional to the concentration of magnetic particles. A reference wire coil identical to the sensing wire coil is connected therewith. A demodulator is connected to each of the coils sends an impedance difference signal to a feedback controller connected to controllable dispensing apparatus for adding a calculated amount of replenishing fluid to the magnetorheological fluid. The system may be incorporated into an integrated fluid management module having apparatus for receiving and replenishing spent magnetorheological fluid and a sensor system in accordance with the present invention for use in a magnetorheological finishing system having a carrier wheel.

Abstract: A system for magnetorheological finishing of a substrate. An integrated fluid management module (IFMM) provides dynamic control of the rheological fluid properties of the MR fluid on a conventional MR finishing apparatus, and dispensing of the fluid to the wheel. A magnetically shielded chamber charged with MR fluid is in contact with the carrier wheel. A transverse line removes the spent MR fluid from the wheel as the ribbon leaves the work zone. Replenishment fluid is added to the chamber via a dripper, and preferably an electric mixer agitates MR fluid in the chamber. A grooved magnetically-shielded insert at the exit of the chamber forms a polishing ribbon on the carrier wheel as the wheel is turned. A sensor sensitive to concentration of magnetic particles provides a signal for control of MR fluid properties, particularly, water content in the MR fluid. Means is provided for cooling fluid within the chamber.

Abstract: A system for sensing and controlling concentration of magnetic particles in magnetorheological fluid comprising a wire coil and an AC voltage generator that, when energized, creates a magnetic flux field including a fringing field. When the fringing field extends through the magnetorheological fluid, the impedance in the circuit is proportional to the concentration of magnetic particles. A reference wire coil identical to the sensing wire coil is connected therewith. A demodulator is connected to each of the coils sends an impedance difference signal to a feedback controller connected to controllable dispensing apparatus for adding a calculated amount of replenishing fluid to the magnetorheological fluid. The system may be incorporated into an integrated fluid management module having apparatus for receiving and replenishing spent magnetorheological fluid and a sensor system in accordance with the present invention for use in a magnetorheological finishing system having a carrier wheel.

Abstract: A system for magnetorheological finishing of a substrate. An integrated fluid management module (IFMM) provides dynamic control of the rheological fluid properties of the MR fluid on a conventional MR finishing apparatus, and dispensing of the fluid to the wheel. A magnetically shielded chamber charged with MR fluid is in contact with the carrier wheel. A transverse line removes the spent MR fluid from the wheel as the ribbon leaves the work zone. Replenishment fluid is added to the chamber via a dripper, and preferably an electric mixer agitates MR fluid in the chamber. A grooved magnetically-shielded insert at the exit of the chamber forms a polishing ribbon on the carrier wheel as the wheel is turned. A sensor sensitive to concentration of magnetic particles provides a signal for control of MR fluid properties, particularly, water content in the MR fluid. Means is provided for cooling fluid within the chamber.

Abstract: A system for determining magnetic permeability of a material. Two electrical inductors formed as primary and secondary concentric coils share a common magnetic core space. A first AC voltage applied to the primary coil creates a magnetic flux in the core proportional to the magnetic permeability of the material. The magnetic flux induces an AC voltage in the secondary coil indicative of the apparent magnetic permeability of the sample. The apparent permeability is corrected for conductivity by imposing a second AC voltage and resistor in series across first and second electrodes disposed in the material. When the material is a magnetorheological fluid, the magnetic permeability is proportional to the concentration of magnetic particles in the sample and can be back-calculated from the amplitude of the secondary voltage signal.

Abstract: A system for determining magnetic permeability of a material. Two electrical inductors formed as primary and secondary concentric coils share a common magnetic core space. A first AC voltage applied to the primary coil creates a magnetic flux in the core proportional to the magnetic permeability of the material. The magnetic flux induces an AC voltage in the secondary coil indicative of the apparent magnetic permeability of the sample. The apparent permeability is corrected for conductivity by imposing a second AC voltage and resistor in series across first and second electrodes disposed in the material. When the material is a magnetorheological fluid, the magnetic permeability is proportional to the concentration of magnetic particles in the sample and can be back-calculated from the amplitude of the secondary voltage signal.

Abstract: A system for determining the magnetic permeability of a material is provided. Two electrical inductors formed as primary and secondary concentric coils share a common magnetic core space. An AC voltage applied to the primary coil creates a magnetic flux in the core proportional to the magnetic permeability of a sample of the material positioned within the core space. The magnetic flux induces an AC voltage in the secondary coil indicative of the sample magnetic permeability. When the material is a magnetorheological fluid, the magnetic permeability is proportional to the concentration of magnetic particles in the sample and can be back-calculated from the amplitude of the secondary voltage signal. Sensitivity and resolution can be increased by using two identical sets of coils wherein a reference material forms a core for the primary set and the MR fluid sample forms a core for the secondary set.

Abstract: A system for determining the magnetic permeability of a material is provided. Two electrical inductors formed as primary and secondary concentric coils share a common magnetic core space. An AC voltage applied to the primary coil creates a magnetic flux in the core proportional to the magnetic permeability of a sample of the material positioned within the core space. The magnetic flux induces an AC voltage in the secondary coil indicative of the sample magnetic permeability. When the material is a magnetorheological fluid, the magnetic permeability is proportional to the concentration of magnetic particles in the sample and can be back-calculated from the amplitude of the secondary voltage signal. Sensitivity and resolution can be increased by using two identical sets of coils wherein a reference material forms a core for the primary set and the MR fluid sample forms a core for the secondary set.

Abstract: An arcuate, preferably cylindrical, magnetic shunt bar supports a plurality of pin magnets having alternate north and south orientations, defining a ring-shaped array of magnets of alternating orientation. The magnet free ends opposite the shunt bar are positioned to conform closely to the shape of a surface to be sealed, forming a narrow gap therebetween containing a multi-polar magnetic field extending beyond the free ends in a direction substantially orthogonal to the surface. The axes of the magnets may be disposed at any desired angular orientation to the surface. Magnetorheological fluid (MRF) in the gap is magnetically stiffened and held as a dynamic seal. The arrangement is useful as a shaft seal, wherein the seal surface passes axially through the array, and also as a wiper for MRF from a carrier surface wherein the surface passes by the array.

Abstract: An arcuate, preferably cylindrical, magnetic shunt bar supports a plurality of pin magnets having alternate north and south orientations, defining a ring-shaped array of magnets of alternating orientation. The magnet free ends opposite the shunt bar are positioned to conform closely to the shape of a surface to be sealed, forming a narrow gap therebetween containing a multi-polar magnetic field extending beyond the free ends in a direction substantially orthogonal to the surface. The axes of the magnets may be disposed at any desired angular orientation to the surface. Magnetorheological fluid (MRF) in the gap is magnetically stiffened and held as a dynamic seal. The arrangement is useful as a shaft seal, wherein the seal surface passes axially through the array, and also as a wiper for MRF from a carrier surface wherein the surface passes by the array.

Abstract: Jet-induced finishing of a substrate surface includes means for covering the surface with an abrasive liquid slurry and means for impinging a jet of fluid, either a gas or a liquid, against the slurry to create a high-shear work zone on the substrate surface whereby portions of the substrate are lifted and removed to alter the shape of the surface towards a predetermined shape and/or smoothness. The surface may be covered as by cascading a flowing layer of slurry over it or by impinging slurry onto the work zone or by immersing the substrate in a pool of the slurry. A nozzle for dispensing the jet fluid is precisely located at a predetermined distance and angle from the surface to be finished. A coarse removal function is provided by disposing the nozzle tip at a first distance from the substrate surface, and a fine removal function is provided by disposing the nozzle closer to the substrate surface.

Abstract: Jet-induced finishing of a substrate surface includes means for covering the surface with an abrasive liquid slurry and means for impinging a jet of fluid, either a gas or a liquid, against the slurry to create a high-shear work zone on the substrate surface whereby portions of the substrate are lifted and removed to alter the shape of the surface towards a predetermined shape and/or smoothness. The surface may be covered as by cascading a flowing layer of slurry over it or by impinging slurry onto the work zone or by immersing the substrate in a pool of the slurry. A nozzle for dispensing the jet fluid is precisely located at a predetermined distance and angle from the surface to be finished. A coarse removal function is provided by disposing the nozzle tip at a first distance from the substrate surface, and a fine removal function is provided by disposing the nozzle closer to the substrate surface.

Abstract: A magnetic wiper for removing magnetorheological fluid from a carrier surface includes a horseshoe magnet having north and south polepieces elongated in a first direction orthogonal to a second direction of magnetic flux in the magnet. The polepieces are generally parallel at their free ends in the first direction and are preferably arcuate such that the inner polepiece forms a trough for receiving magnetorheological fluid removed from the carrier surface and conveying it to an exit tube. The free ends are shaped to conform closely to the shape of the carrier surface, forming a narrow gap therebetween containing a magnetic fringing field extending beyond the free ends.

Abstract: A magnetic wiper for removing magnetorheological fluid from a carrier surface includes a horseshoe magnet having north and south polepieces elongated in a first direction orthogonal to a second direction of magnetic flux in the magnet. The polepieces are generally parallel at their free ends in the first direction and are preferably arcuate such that the inner polepiece forms a trough for receiving magnetorheological fluid removed from the carrier surface and conveying it to an exit tube. The free ends are shaped to conform closely to the shape of the carrier surface, forming a narrow gap therebetween containing a magnetic fringing field extending beyond the free ends.

Abstract: A magnetic wiper for removing magnetorheological fluid from a carrier surface includes a horseshoe magnet having north and south polepieces elongated in a first direction orthogonal to a second direction of magnetic flux in the magnet. The polepieces are generally parallel at their free ends in the first direction and are preferably arcuate such that the inner polepiece forms a trough for receiving magnetorheological fluid removed from the carrier surface and conveying it to an exit tube. The free ends are shaped to conform closely to the shape of the carrier surface, forming a narrow gap therebetween containing a magnetic fringing field extending beyond the free ends.

Abstract: A fluid having magnetorheological (MR) properties and including a finely-divided abrasive material is directed through a non-ferromagnetic nozzle disposed axially of the helical windings of an electric solenoid. The MR fluid may contain magnetosoft or magnetosolid particles or mixtures thereof. A magnetic field created by the solenoid orients and aligns the magnetic moments of the particles to form fibrils thereby stiffening the flowing MR fluid which, when ejected from the nozzle, defines a highly-collimated jet. Collimation of the MR material persists for a significant time outside the magnetic field, permitting use of the abrasive jet to shape and/or polish the surface of a workpiece at some distance from the nozzle. The jet is directed into a shroud against a workpiece mounted for multiple-axis rotation and displacement to meet predetermined material removal needs for shaping. The solenoid may be similarly mounted to also move the jet over the surface of the workpiece.