佛山输卵管输卵管堵塞怎么办课件

Magnetic Materials Seminar,Presented by: International Magnaproducts, Inc.,Agenda,I. Brief Intro to IMI II. History of Permanent Magnet Materials III. Overview of Magnetic Terms IV. Basic Physics and Fundamentals V. Material Characteristics,VI. Testing Methods VII. Magnetizing Methods VIII. Conclusion IX. Questions,International Magnaproducts, Inc.,Created by Don Coleman in 1982 Locations Valparaiso, IN Broomfield, CO Warehouse Facilities 30,000 sq. ft. Primary Materials Bonded Magnets Ceramics Alnico Sintered NdFeB (licensed) SmCo Ferrite Compounds Magnetizers, Demagnetizers, Test Equipment,Value-Added Services,Quality Control and Testing Warehousing Magnetizing and Demagnetizing Powder Processing Technical Support Engineering/Design Support,IMI, Contd,Primary Customers Eastman Kodak Seagate Ametek Fisher & Paykel MPC General Motors Hamlin Woodward Inc Strattec (Briggs&Stratton),Delphi Automotive Honeywell Microswitch Hi-Stat BEI Kimco General Electric Lear Corporation Breed Automotive Cherry Electrical,History of Permanent Magnets,MK Steel,Alnico,Ferrites,SmCo 1-5,SmCo 2-17,NdFeB,Basic Physics and Fundamentals,Magnetic Version of Kirchofs Voltage Law Sum of all MMF (Hl) drops around a closed circuit is equal to the current enclosed (Ni) (also known as Amperes Law) Static gap problem: HmLm + HFeIFe + HgIg = 0 Since HFe = OmHmLm = HgIg Magnetic Version of Ketchoffs Current Law Flux (Uo=BA) entering any cross section of spave is equal to the flux leaving it. Static gap problem: BmAm = BgAg (=BFeAFe),Hysteresis Graphs,Two Basic Types Useful to Designers: Normal demag curve - Used by the designer to calculate the flux density in the air gap or the flux in aparticular portion of the magnetic circuit. Intrinsic demag curve - Used by the designer to evaluate the effect of any demagnetization influence on the magnet in its magnetic circuit.,Properties that can be found from these curves: Residual flux density Intrinsic coercive force Normal coercive force Normal energy product,Calculations of Load Lines,Def: This is the relationship between B in the magnet and H in the magnet, as dictated by the magnetic circuit. Since M in the air gap is zero, Bg = 0 Hg Subsituting BmAm = HgAh Solving and subsituting: BmAm = - HmLmAgNg Dividing by 0AmHm: BmI0Hm = -lmAgIAmLg,How to Read a Hysteresis Loop of a Permanent Magnet,Basic Magnetic Quantities,B (Magnetic Induction): Defined by the force moving on a charge F = qov x B (general) Magnetic Dipoles: Origin - Current loop m=iA Atom m=gJB Potential Energy - U = -mB Torque: = m X B The magnetic moment is defined as j = 0m, in which case J and H appear in the energy and torque equations.,Magnetic Quantities, Contd,M (magnetization): Def - Dipole moment per unit volume J = Bi = 0m(Magnetic polarization) H (magnetic field strength): H=1/ B(B-M) Br (Remanence): Def - The induction remaining after a saturation magnetizing field is reduced to zero (internal) Since H = 0, Br = Bir iHc (Intrinsic Coercivity): Def - the negative field required to reduce Bi to zero, after the application of a saturating magnetizing field. Differentiates permanent magnets from other magnets.,Magnetic Quantities, Contd,Hc (Coercivity): Def - The negative magnetic field required to reduce b to zero, after application of saturating magnetizing field. (BH)Max: Def Maximum product of (BdHd) which can be obtained on the demagnetization curve. Incdicates the energy that a magnetic material can supply to an external magnetic circuit when operation at any point on its demagnetization curve. Rev. Temp. Coeff: A number which describes the change in a magnetic property with a change in temperature. It is usually expressed as the percentage change per unit of temperature. Both Br & Hc affected. Curie Temp.: The transition temperature above which a material loses its permant magnet properties. Due to metallurgical change in material.,Magnetic Quantities, Contd,Irreversible Temp. Loss: Irreversible changes in the magnetic state can be caused by spontaneous reversals of magnetization in individual Weiss domains brought about by thermally induced fluctuations in the internal magnetic field. Reversible Changes: Temperature fluctuations also result in reversible changes in the magnetic flux density in the permanent magnet.,Magnetic Quantities, Contd,MMPA Def: A permanent magnet is a body that is capable of maintaining a magnetic field at other than cryogenic temperature with no expenditure of power. What does this mean? Even in the case of low coercivity of Alnico magnets, the flux density loss over many, many years amounts to only a few percent. Irreversible and reversible losses of magnetic properties,Types of Magnetic Materials,Not Ordered Diamagnetic Atoms have no permanent magnetic moment, only induce moment(Faradys Law) Small negative magnetization at normal H (10kOe) Paramagnetic Atoms have no permanent magnetic moment, no interatomic interaction Small positive magnetization at nomal H (10kOe),Magnetic Materials, cont.,Magnetically Ordered Antiferromagnetic Atoms have permanent moment, strong interatomic interaction Two equal and opposite sublattices, spontaneous magnetization is zero Small positive magnetization at normal H (10kOe) Ferromagnetic Atoms have permanent moment, strong interatomic interaction All atomic moments are coupled parallel, large spontaneous magnetization Very large positive magnetization at normal H (10kOe) Ferrimagnetic Atoms have permanent moment, strong interatomic interaction Two unequal and opposite sublattices, large spontaneous magnetization Large positive magnetization at normal H (10kOe),Diagrams of Magnetic Materials,Domain Wall Movement,The spontaneous alignment of atomic magnetic moments in ferromagnetic materials is generally limited to certain regions known as Weiss domains The transition zones between these regions in which the atomic magnetic moments rotate from one preferred direction into another, are known as Bloch Walls. Initial magnetization Rotational process Saturation Saturation is reached when all magnetic moments are arranged parallel to the external magnetic field. B then increases only proportionally to field strength H.,Initial State,Weak magnetic field applied,Increasing field makes one domain,Material has reached saturation,Domain Wall Movement,Testing Permanent Magnets,Testing, cont.,Typical Methods: Fluxmeter: used for measuring magnetic flux. As the flux changes, a voltage is induced; the resultant current causes the coil of the fluxmeter to be deflected. Gaussmeters: 4 types are rotating magnet, Hall effect, rotating coil, and nuclear magnetic resonance. Measures surface Gauss of permanent magnets MagScan: Real-time magnetic field scan analyzing. Flatbed or rotary scanning machines can be utilized.,Standard Test Methods,Open Circuit test: any method that is used to test a magnet in free space after it has been magnetized. Generated voltage test: Useful to test production magnets and associated magnetic circuits intended for us in DC motors and generators. Pull test: Mechanical text that involves measuring the mechanical force required to pull the pole face of a permanent magnet from a piece of steel or from another magnet when opposite poles are in line. Torque test: Rotational mechanical force required to overcome the force resulting from the magnetic attraction between magnetic poles of two magnets through a specified air gap is measured.,Permanent Magnet Materials,Most Commonly Used Materials AlNiCo Ferrites Samarium Cobalt Neodymium-Iron-Cobalt Bonded Materials Ferrite Neo SmCo,AlNiCo Magnets,Attributes: High flux, high Curie temp., very temperature stable (-.02%/C) Detriments: Difficult to mount, low Hc,Cast and Sintered AlNiCo Processes,Ferrite Materials,Attributes: Low costs, moderately high Hc & Hci, very high electrical resistance, “most flux for bucks. Detriments: Moderately low Curie temp., poor temperature stability (-.2%/C),Ferrite Production Process,SmCo Grades,Attributes: High magnetic characteristics, high Curie temp, very temperature stable, high energy for low volume, can be machined easily to very small sizes. Detriments: High costs, very brittle,SmCo Production,Nd-Fe-B Materials,Attributes: High energy for size, more economical than SmCo, no cobalt, very high Hc and Hci. Detriments: Poor temperature coefficient (-.13%/C), material will oxidize if not coated, low Curie temperature.,Sintering 1030-1100C,Sintered Neodymium-Iron-Boron,Other magnetic materials on the market,MA: (BH)Max = 1.3 5.5 MGOe, Br = 2700-5500G, Hc = 1800-2500 Oe Curie Temp = 300 C, Max. Work Temp = 500 C Attributes: Easily machineable, extremely durable, various mag. patterns Detriments: Very high cost. SmFeN: (BH)Max = 12.9 MGOe, Br = 11.5 kG, Hc = 600-700 Oe Max Work Temp. = 100 C Attributes: Highest mag. Properties of bonded magnets Detriments: Low maximum working temp. = 100 C Formag: (BH)Max = 4.5-6.0 MGOe, Br=11.5 12.5 kG, Hc = 600-700 Oe Curie temp = 640 C, Max Work Temp = 460 C Attributes: Excellent temp. and mechanical strength, no voids or piping Detriments: Rods or pins are main configuration,Compression Molding,Advantages: Good shaping/tolerances Low Tooling Highest (BH)Max Disadvantages: Some tolerance restrictions in one dimension. Not fully 3-D capable Characteristics: (BH)Max = 12, 13 MGOe Br = 7.6, 7.g kG Hc = 5.9, 6 kOe Hci = 10.8, 12 kOe,Calendering Process,Advantages: No tooling Continuous sheet available Low cost process Disadvantages: Almost exclusively ferrite Temp limitations Max. thickness of sheets Characteristics: (BH)Max = up to 1.6 MGOe Br = 2610 g Hc = 2150 Oe Hci = 2650 Oe,Extrusion Molding,Advantages: Excellent for long/continuous product Relatively low tooling cost Mechanical or magnetic alignment Disadvantages: Temperature capability “Profile” or sheet only Max. thickness of sheets Characteristics: (BH)Max = 10.0 MGOe Br = 7.0 kG Hc = 5.7 kOe Hci = 10.8 kOe Max/Min Width = up to 4” wide Max/Min Thick = up to .250”,Injection Molding,Advantages: Excellent shaping/tolerances Utilize all powders Over/Insert - molding Disadvantages: High tooling cost Restricted performance Approx. 35% binder Characteristics: (BH)Max = 2.2 MGOe Br = 3000 G Hc = 2250 Oe Hci = 3300 Oe Max/Min O.D. = up to 6.00”,Rare Earth Characteristics(Inj. Molding),Multi-Component Injection Molding,Multi component injection molding (MCIM) or Co-injection is a manufacturing method by which several non-simil