Electromagnetic shaker apparatus for fretting wear system

Abstract

An electromagnetic shaker apparatus includes a body, and a magnetic device housed within the body and configured to provide a static magnetic field. The apparatus further includes an armature, and a solenoid coil mounted on the armature and configured to receive current from a power supply. Interaction between the static magnetic field and the solenoid coil can generate a Lorentz force that causes movement of the armature relative to the body. The apparatus can withstand high temperatures and / or pressures and / or chemical conditions, and can be used in a fretting wear system in testing environments.

Description

TITLE: ELECTROMAGNETIC SHAKER APPARATUS FOR FRETTING WEAR SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Patent Application No. 63 / 533,438 filed on August 18, 2023, the entire contents of which are hereby incorporated herein by reference.FIELD

[0002] The present disclosure relates generally to testing of nuclear reactor components.INTRODUCTION

[0003] The following paragraphs are not an admission that anything discussed in them is prior art or part of the knowledge of the person of ordinary skill in the art.

[0004] Fretting of nuclear components can be a significant factor that limits their lifespan. High temperature fretting wear testing at Canadian Nuclear Labs (CNL) has been conducted on specialized machines, which have required a significant cost to train staff, maintain the equipment, and update procedures. Generally, testing has been conducted on wear specimens of CANDU (Canada Deuterium Uranium) and Pressurized Water Reactors (PWRs) at operating conditions (pressure, temperature, and chemistry), while subjecting them to the level of interaction encountered in service.

[0005] Currently, fretting wear rigs can apply excitation using shaker devices located outside of the pressure boundary through a flexible sleeve, and this seal may not withstand high temperature and pressure commensurate with Light Water Reactor (LWR) operating conditions on the primary side (e.g. nominally 320 °C and 15.5 MPa). This means that test rigs are operated with stagnant liquid within the autoclave, and with a significant temperature gradientfrom the uppermost portion where the fretting wear occurs, down to the bottom where the flexible seal is located.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The drawings included herewith are for illustrating various examples of apparatuses and methods of the present disclosure and are not intended to limit the scope of what is taught in any way.

[0007] Figure 1 is a perspective view of an electromagnetic shaker apparatus according to a first example.

[0008] Figure 2 is an exploded view of the apparatus of Figure 1 .

[0009] Figure 3 is a side view of the apparatus of Figure 1 .

[0010] Figure 4 is a sectional view along line 4-4 in Figure 3.

[0011] Figure 5 is a detailed view of Figure 4.

[0012] Figure 6 is a detailed view of Figure 4.

[0013] Figure 7 is a perspective view of an electromagnetic shaker apparatus according to a second example.

[0014] Figure 8 is an exploded view of the apparatus of Figure 7.

[0015] Figure 9 is a side view of the apparatus of Figure 7.

[0016] Figure 10 is a sectional view along line 10-10 in Figure 9.

[0017] Figure 11 is a detailed view of Figure 10.

[0018] Figure 12 is a detailed view of Figure 10.

[0019] Figure 13 is a schematic view of an example of a fretting wear system.

[0020] Figure 14 is a sectional view of an example of an inertial shaker apparatus.DETAILED DESCRIPTION

[0021] Various apparatuses or methods will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover apparatuses and methods that differ from those described below. The claimed inventions are not limited to apparatuses and methods having all of the features of any one apparatus or method described below, or to features common to multiple or all of the apparatuses or methods described below. It is possible that an apparatus or method described below is not an embodiment of any claimed invention. Any invention disclosed in an apparatus or method described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicant(s), inventor(s) and / or owner(s) do not intend to abandon, disclaim or dedicate to the public any such invention by its disclosure in this document.

[0022] The present disclosure relates to apparatuses for and methods of performing fretting wear tests. In some examples, the apparatus and the method may include an electromagnetic shaker apparatus that can withstand high temperatures and / or pressures and / or chemical conditions present within a nuclear reactor, that can simply be mounted inside the autoclave of the test rig. This can overcome deficiencies of current test rigs, and can provide a more accurate representation of reactor conditions. The fretting wear capability may be extended to Boiling Water Reactor (BWR) conditions in refreshed autoclaves, as well as potentially to advanced reactor environments (e.g. Supercritical Water Reactor [SCWR] and High Temperature Gas Reactor [HTGR]), or other comparable reactors.

[0023] An electrodynamic shaker can operate in manner that is similar to that of an audio speaker. In the device, a coil of copper wire is positioned in a fixed magnetic field, created either by a permanent magnet or by an electromagnet driven by a DC current. If the coil is supplied with AC current at some frequency, then the coil will experience a force (called the Lorentz force),perpendicular to both the applied magnetic field and the direction of the electrical current, that will oscillate at the same frequency. Since the coil and the fixed field electromagnet can consist simply of a copper coil of wire having an overall low resistance (e.g. on the order of a few ohms), it is possible to operate the shaker under water because the drive voltages are much lower than the dielectric breakdown voltage of the water.

[0024] Referring to Figures 1 and 2, an electromagnetic shaker apparatus is shown generally at reference numeral 100. In the example illustrated, the apparatus 100 includes a body 102, a magnetic device 104 housed within the body 102, an armature 106 arranged in the body 102 above the magnetic device 104, and a solenoid coil 108 mounted on the armature 106.

[0025] In the example illustrated, the magnetic device 104 can be configured to provide a static magnetic field, and the solenoid coil 108 can be configured to receive current from a power supply (not shown). Interaction between the static magnetic field and the solenoid coil 108 generates a Lorentz force that in operation causes movement of the armature 106 relative to the body 102.

[0026] More specifically, in the example illustrated, a voltage source is applied to the solenoid coil 108 and current within the coil winding is perpendicular to the direction of the magnetic field in the air gap adjacent to the solenoid coil 108. This creates a vertical Lorentz force (perpendicular both to the coil current and the magnetic field) on the solenoid coil 108 that causes the armature 106 to move / vibrate at the frequency of the external voltage source.

[0027] In some examples, the magnetic device 104 can include a permanent magnet. In some examples, the magnetic device 104 can include a bias coil configured to receive direct current from a power supply.

[0028] Referring to Figures 3 and 4, the body 102 includes a bottom wall 110, and an outer wall 112 extending upwardly from the bottom wall 110. In the example illustrated, the magnetic device 104 is mounted to the bottom wall 110 of the body 102. In the example illustrated, the bottom wall 110 is planar, theouter wall 112 is cylindrical, and the outer wall 112 defines a central axis 114 (Figure 2) that is orthogonal to the bottom wall 110. The magnetic device 104 can be centered relative to the central axis 114. The body 102, particularly the outer wall 112, can be formed of a ferromagnetic material to direct the static magnetic field of the magnetic device 104. In some examples, if the bottom wall 110 is formed of ferromagnetic material, the attractive force of the magnetic device 104 can be sufficient to keep it mounted to the bottom wall 110, without adhesive or fasteners, for example. Also, as illustrated, the bottom wall 110 can include a recessed top surface for keeping the magnetic device 104 seated in its centered position.

[0029] In the example illustrated, the armature 106 includes a radial portion 116, and an axial portion 118 that extends downwardly from the radial portion 116. The radial portion 116 can be centered relative to the central axis 114. In the example illustrated, the axial portion 118 is cylindrical, and the solenoid coil 108 is mounted to the axial portion 118 of the armature 106. In the example illustrated, the solenoid coil 108 is formed of wire wound around an outer surface of the axial portion 118 and extends substantially across a vertical extent thereof. In some examples, the wire can be wound around the axial portion 118 to form the coil 108 without adhesive, which can lack durability in all environments. Ends of the wire may be welded to a tab (not shown) and connected to the power supply.

[0030] Referring to Figure 5, the solenoid coil 108 is offset radially inwardly relative to an inner annular ridge of the outer wall 112 to define a first gap 120. The annular ridge of the outer wall 112 accommodates threaded receipt of a plurality of fasteners 138 and is also designed to concentrate the magnetic field.

[0031] Referring to Figures 2 and 4, the apparatus 100 includes a top cap 122 secured to the magnetic device 104 and positioned axially intermediate the magnetic device 104 and the radial portion 116 of the armature 106. The top cap 122 can be formed of a ferromagnetic material to direct the static magnetic field of the magnetic device 104. In some examples, the attractiveforce of the magnetic device 104 can be sufficient to keep the top cap 122 secured to the magnetic device 104, without adhesive or fasteners, for example.

[0032] Referring to Figure 5, the top cap 122 is adjacent to the solenoid coil 108 and offset radially inwardly relative to the axial portion 118 to define a second gap 124. The gaps 120, 124, along with spacing between the radial portion 116 of the armature 106 and the top cap 122, permit movement of the armature 106 in operation. In the example illustrated, the top cap 122 is positioned within an axial extent of the axial portion 118 of the armature.

[0033] In the example illustrated, the top cap 122 distributes and concentrates the magnetic field from the magnetic device 104 into the gap 124. Because the Lorentz force is perpendicular to both the magnetic field and the current in the solenoid coil 108, the top cap 122 may be employed to redirect the magnetic field to run radially with respect to the solenoid coil 108 (whose current is running azimuthally). This results in a Lorentz force in the vertical direction to move the armature 106 up and down.

[0034] In the example illustrated, the exemplary apparatus 100 includes a wafer spring 126 for coupling the body 102 and the armature 106. Referring to Figures 2 and 6, the wafer spring 126 includes an inner portion 128 secured to the radial portion 116 of the armature 106 by a threaded axial rod 130 and a nut 132. The armature 106 is arranged below the wafer spring 126, and the radial portion 116 of the armature 106 is shown to include a flange 134 that mates with a bottom surface of the wafer spring 126. In the example illustrated, the flange 134 of the armature 106 defines a threaded aperture through which the axial rod 130 extends.

[0035] In the example illustrated, referring to Figures 2 and 5, the wafer spring 126 includes an outer portion 136 secured to the outer wall 112 of the body 102 by the plurality of fasteners 138 and respective spacers 140. Between the inner and outer portions 128, 136, the wafer spring 126 has a generally open structure to reduce drag.

[0036] With reference to Figures 2 and 6, a bottom end 142 of the axial rod 130 is shown slidably received in a linear bearing element 144 that is mounted within a central aperture 146 of the top cap 122. The linear bearing element 144 can be press fit into the central aperture 146 of the top cap 122. The linear bearing element 144 can permit axial movement of the armature 106 relative to the body 102 while inhibiting radial / lateral movement that could cause rubbing or otherwise damage the components of the apparatus 100. The bottom end 142 and the linear bearing element 144 should be dimensioned suitably to permit the axial movement without too much friction.

[0037] The following dimensions of the apparatus 100 are intended to be illustrative but non-limiting. The body 102 can have an outer diameter of about 1 .500 inches, a height of about 0.910 inches, and a thickness of the outer wall 112 of about 0.500 inches. The magnetic device 104 can have an outer diameter of about 1.100 inches and a height of about 0.625 inches. The armature 106 can have an outer diameter of about 1.170 inches, a height of about 0.325 inches, a thickness of the radial portion 116 of about 0.025 inches, and a thickness of the axial portion 118 of about 0.015 inches. The top cap 122 can have an outer diameter of about 1 .100 inches and a height of about 0.225 inches. The first gap (outer) 120 can be about 0.008 inches, and the second gap (inner) 124 can be about 0.040 inches.

[0038] Referring to Figures 7 and 8, an electromagnetic shaker apparatus is shown generally at reference numeral 200. The apparatus 200 is similar to the apparatus 100, with like features identified by like reference numerals.

[0039] In the example illustrated, the apparatus 200 includes a body 202, a magnetic device 204 housed within the body 202, an armature 206 arranged in the body 202 above the magnetic device 204, and a solenoid coil 208 mounted on the armature 206.

[0040] In the example illustrated, the magnetic device 204 can be configured to provide a static magnetic field, and the solenoid coil 208 can be configured to receive current from a power supply (not shown). Interactionbetween the static magnetic field and the solenoid coil 208 generates a Lorentz force that in operation causes movement of the armature 206 relative to the body 202.

[0041] More specifically, in the example illustrated, a voltage source is applied to the solenoid coil 208 and current within the coil winding is perpendicular to the direction of the magnetic field in the air gap adjacent to the solenoid coil 208. This creates a vertical Lorentz force (perpendicular both to the coil current and the magnetic field) on the solenoid coil 208 that causes the armature 206 to move / vibrate at the frequency of the external voltage source.

[0042] In some examples, the magnetic device 204 can include a permanent magnet. In some examples, the magnetic device 204 can include a bias coil configured to receive direct current from a power supply.

[0043] In the example illustrated, the apparatus 200 includes a terminal block 248 and an adapter 250 to connect the apparatus 200 to an external voltage source (not shown). The adapter 250 can be fastened to the body 202, and the terminal block 248 can be fastened to the adapter 250.

[0044] Referring to Figures 9 and 10, the body 202 includes a bottom wall 210, and an outer wall 212 extending upwardly from the bottom wall 210. In the example illustrated, the magnetic device 204 is mounted to the bottom wall 210 of the body 202. In the example illustrated, the bottom wall 210 is planar and includes a central mounting and assembly hole 252 and lateral holes 254 that permit fluid to escape the bottom of the apparatus 200 when it is shut down and drained. In the example illustrated, the outer wall 212 is cylindrical, and the outer wall 212 defines a central axis 214 (Figure 8) that is orthogonal to the bottom wall 210. The magnetic device 204 can be centered relative to the central axis 214. The body 202, particularly the outer wall 212, can be formed of a ferromagnetic material to direct the static magnetic field of the magnetic device 204. In some examples, if the bottom wall 210 is formed of ferromagnetic material, the attractive force of the magnetic device 204 can be sufficient to keep it mounted to the bottom wall 210, without adhesive or fasteners, for example. Also, as illustrated, the bottom wall 210 can include arecessed top surface for keeping the magnetic device 204 seated in its centered position.

[0045] In the example illustrated, the armature 206 includes a radial portion 216, and an axial portion 218 that extends downwardly from the radial portion 216. The radial portion 216 can be centered relative to the central axis 214, and is shown to include a plurality of perforations arranged in an array to reduce drag. In the example illustrated, the axial portion 218 is cylindrical, and the solenoid coil 208 is mounted to the axial portion 218 of the armature 206. In the example illustrated, the solenoid coil 208 is formed of wire wound around an outer surface of the axial portion 218 and extends substantially across a vertical extent thereof, retained between outwardly extending upper and lower lips. In some examples, the wire can be wound around the axial portion 218 to form the coil 208 without adhesive, which can lack durability in all environments. Ends of the wire may be welded to a tab (not shown) and connected to the power supply.

[0046] Referring to Figure 11 , the solenoid coil 208 is offset radially inwardly relative to an inner annular ridge of the outer wall 212 to define a first gap 220. The annular ridge of the outer wall 212 accommodates threaded receipt of a plurality of fasteners 238 and is also designed to concentrate the magnetic field.

[0047] Referring to Figures 8 and 10, the apparatus 200 includes a top cap 222 secured to the magnetic device 204 and positioned axially intermediate the magnetic device 204 and the radial portion 216 of the armature 206. The top cap 222 can be formed of a ferromagnetic material to direct the static magnetic field of the magnetic device 204. In some examples, the attractive force of the magnetic device 204 can be sufficient to keep the top cap 222 secured to the magnetic device 204, without adhesive or fasteners, for example. Also, as illustrated, the top cap 222 can include a recessed bottom surface for keeping it seated in its position on the magnetic device 204.

[0048] Referring to Figure 11 , the top cap 222 is adjacent to the solenoid coil 208 and offset radially inwardly relative to the axial portion 218 to define asecond gap 224. The gaps 220, 224, along with spacing between the radial portion 216 of the armature 206 and the top cap 222, permit movement of the armature 206 in operation. In the example illustrated, the top cap 222 is positioned within an axial extent of the axial portion 218 of the armature.

[0049] In the example illustrated, the top cap 222 distributes and concentrates the magnetic field from the magnetic device 204 into the gap 224. Because the Lorentz force is perpendicular to both the magnetic field and the current in the solenoid coil 208, the top cap 222 may be employed to redirect the magnetic field to run radially with respect to the solenoid coil 208 (whose current is running azimuthally). This results in a Lorentz force in the vertical direction to move the armature 206 up and down.

[0050] In the example illustrated, the exemplary apparatus 200 includes two wafer springs 226 for coupling the body 202 and the armature 206. Referring to Figures 8 and 12, the wafer springs 226 each include an inner portion 228 secured to the radial portion 216 of the armature 206 by an axial fastener 256 and an adapter 258 (along with a spacer and washers). As illustrated, the fastener 256 and the adapter 258 can be threaded together. The armature 206 is arranged below the wafer springs 226, and the radial portion 216 of the armature 206 is shown to include a flange 234 that mates with a bottom surface of the lower wafer spring 226. In the example illustrated, the flange 234 of the armature 206 defines an aperture through which the axial fastener 256 extends, with a head of the fastener engaging the bottom surface of the radial portion 216 immediately surrounding the aperture. The head of the axial fastener 256 is shown disposed within a central aperture 246 of the top cap 222 with clearance to permit movement.

[0051] In the example illustrated, referring to Figures 8 and 11 , the wafer springs 226 each include an outer portion 236 secured to the outer wall 212 of the body 202 by the plurality of fasteners 238 and respective spacers 240. Between the inner and outer portions 228, 236, the wafer springs 226 have a generally open structure to reduce drag.

[0052] The two wafer springs 226 can cooperate to resist sideways movement because they are flexible in the vertical axis but rigid side-to-side. In use, this can promote translation of the adapter 258 vertically, with minimal side-to-side movement.

[0053] The following dimensions of the apparatus 200 are intended to be illustrative but non-limiting. The body 202 can have an outer diameter of about 2.450 inches, a height of about 0.975 inches, and a thickness of the outer wall 212 of about 0.150 inches. The magnetic device 204 can have an outer diameter of about 1.820 inches and a height of about 0.635 inches. The armature 206 can have an outer diameter of about 1.965 inches, a height of about 0.385 inches, a thickness of the radial portion 216 of about 0.025 inches, and a thickness of the axial portion 218 of about 0.015 inches. The top cap 222 can have an outer diameter of about 1.830 inches and a height of about 0.240 inches. The first gap (outer) 220 can be about 0.017 inches, and the second gap (inner) 224 can be about 0.015 inches.

[0054] It should be appreciated that the apparatuses 100, 200 can be relatively compact and yet powerful for their size, and also capable of withstanding 320 °C or more, and immersion in water or steam.

[0055] Referring to Figure 13, a fretting wear system is shown generally at reference numeral 300. In the example illustrated, the system 300 includes two of the shaker apparatuses 100, 200, which are mounted perpendicularly in order to excite the target in multiple dimensions. In this configuration, complex fretting wear motion such as impact fretting or simple reciprocating fretting may be implemented. In other examples, one, three, or more of the shaker apparatus can be employed in a fretting wear system.

[0056] Although partially obscured from view, in the example illustrated, two other shaker apparatuses are provided on the other side of the system in a mirror image arrangement. The shaker 100 and its counterpart below can be coordinated to receive a first input signal. The shaker 200 and its counterpart below can also be coordinated with a second input signal. In some examples,the input signals can be independent of each other and uncorrelated to promote random vibration.

[0057] In the example illustrated, each apparatus is coupled to a probe target 302 by a transversely flexible stinger 304, which transfers movement to the probe target 302. Displacement probes 306 can be used to monitor movement of the probe target 302. In some examples, the displacement probe can include an eddy current sensor. In some examples, the displacement probe can include a capacitive sensor and / or an ultrasonic sensor.

[0058] In the example illustrated, a test piece 308 (e.g. tube specimen) is coupled to the probe target 302, and a static target 310 (e.g. support specimen) is arranged below and adjacent to the test piece, located on an instrument platform 312. Movement of the test piece by the apparatuses wears the test piece against the static target.

[0059] In the example illustrated, the system 300 includes force transducers 314 connected to the instrument platform 312. In some examples, the force and displacement sensors can be used to provide real-time measurements of the position of the test piece and the work rate that arises from fretting. This can allow for greater control of the experiment and interpretation of the results.

[0060] Furthermore, in some examples, the relatively short distance between the apparatuses and the test piece can allow for a mechanically simple design enabling larger forces and / or higher frequency (on the order of kHz) to be imparted to the tubes. This can also allow for good control of specific wear patterns and vibrational modes imparted to the tubes, which can be explored during experiments.

[0061] The following is a description of the design and material selection for the coils 108, 208 and the magnetic device 104, 204, which is intended to be illustrative but non-limiting.

[0062] The target 320 °C operating temperature offers a unique problem for the insulation of the wire that forms the coils. In some examples, ceramiccoated pure nickel wire, or nickel-coated copper wire (e.g. Kulgrid™) can be used to create the solenoid coil. However, other wire types and / or insulation methods (e.g. mica tape, and / or fiberglass) may be used depending on the requirements of the apparatus. For operation at higher temperatures, a solenoid coil formed of high temperature wire may be required.

[0063] In some specific examples, the solenoid coil can be formed of 26 turns of high-temperature wire (e.g. Ceramawire N-30™ All Nickel [Nickel 205]) in two layers (i.e. a total of 52 wire turns). The wire outer diameter can be 0.011”.

[0064] In examples with a permanent magnet as the magnetic device, the choice of material can depend on three criteria: Residual Flux Density (Br), Coercive Force (He), and maximum operating temperature. The first relates to the overall strength of the magnet, and the second describes the propensity of the magnet to become demagnetized in the presence of an applied magnetic field. Though little can be done about these two parameters, the third is an important consideration, as magnets can lose their strength and can even demagnetize at elevated temperatures.

[0065] Two potential materials for use as the permanent magnet and their properties are listed below in Table 1 . As shown below, a samarium-cobalt (SmCo) magnet can be comparatively weaker than alnico and can operate at lower temperatures. However, the alnico magnet can be vulnerable to demagnetization in the presence of stray magnetic fields. In some examples, the body of the apparatus may provide adequate shielding from external magnetic fields, and alnico magnets can be implemented. In some examples, a combination of magnet materials may be possible, with a view to retaining properties of each magnet type.Table 1. Permanent magnet materials

[0066] For the joining of components, most glues, adhesives, epoxies, may not be permitted in the autoclave environment due to the risk of chemical contamination. In some examples, as mentioned above, the body, the magnetic device and the top cap can be maintained together by magnetic force and without the use of adhesives or fasteners. In some examples, as mentioned above, the coil can be secured to the armature without adhesives. In some examples, the coil can be bonded to the armature using a ceramic cement. In some examples, other methods for bonding the coil to the armature (or other components) may be used. In some examples, a metallic ring may be heated such that its thermal expansion increases its diameter and is then inserted around the coil and armature. As the ring cools, its diameter contracts and holds the coil in place.

[0067] The description above relates to generally to modal shakers that are well suited for use in an autoclave. In other examples, teachings of the present disclosure can be applied to an inertial high temperature shaker that can be used in a helium oven, for example, or other high temperature environments.

[0068] Referring to Figure 14, an inertial shaker apparatus is shown generally at reference numeral 400. The materials for the apparatus 400 can be selected such that it can operate in a high temperature environment.

[0069] The apparatus 400 includes a high temperature permanent magnet (e.g. alnico or samarium-cobalt) 402, which can provide magnetic field at high temperature, and can be magnetized in the vertical direction. The magnet 402 may be a disk or an annulus. The latter can lower the mass of themoving magnet, which may allow for higher frequency operation than if a diskshaped magnet was used.

[0070] In the example illustrated, the apparatus 400 includes a body 404 and top or end caps 406, which provide the means for the magnetic field to form a circuit through two annular gaps. The body 404 is shown to include an outer wall, which is cylindrical with an inner annular ridge at each end, designed to concentrate the magnetic field.

[0071] In the example illustrated, the magnet 402, the body 404 and the top caps 406 are the parts of the inner core of the shaker that is the moving subassembly. The body 404 and the top caps 406 can be formed of a ferromagnetic material to direct the static magnetic field of the magnetic device 402. The magnet can be magnetized with this subassembly in order to maintain a strong magnetic field across the coils. In addition, if the magnet material used is alnico (which has a low coercive force compared to other permanent magnets), this subassembly can prevent demagnetization.

[0072] In the example illustrated, the outer parts of the apparatus 400 include an armature ring 408, two armatures 410, and the two wafer springs 412. These are the fixed parts of the apparatus. The armature ring 408 can be fastened to the base of the fretting wear apparatus using a mounting bracket (not shown).

[0073] In the example illustrated, the armature ring 408 supports the upper and lower armatures 410. The armatures 410 consist of a radial portion and an axial portion. The axial portion secures the two wraps of magnet wire, also called the solenoid coil. The solenoid coil can be formed of wire wound around the axial portion of the armature 410 and it extends through the vertical portion of the annular gap. The wire ends can extend radially outward and can be connected to a common power supply. The two wafer springs 412 can connect the armature 410 and armature ring 408 to the inner core.

[0074] In the example illustrated, the moving parts 402, 404, 406 and the fixed parts 408, 410, 412 may move relative to each other because of the wafersprings 412 are flexible in the up and down direction, but are relatively stiff in the other axes.

[0075] In the example illustrated, the body 404 is held to the magnet 402 by two fasteners, and the magnet 402 has two threaded inserts for this purpose. The top caps 406 can be held to the magnet 402 by magnetic pull force, and a recessed inner surface keeps it centered to the magnet and positions the magnet. In some examples, parts 404 and 406 could be made of cobalt with a higher curie temperature.

[0076] In the example illustrated, the apparatus 400 includes two coils of wire placed in a magnetic field, thereby nominally doubling the force produced when an electrical current is supplied. The coils can be multiple windings in two wraps of high temperature magnet wire situated in an annular gap where the magnetic field is concentrated. In the example illustrated, two wafer springs couple the inner moving parts to the fixed outer parts, which are spaced further apart and this increases the static transverse load carrying capacity of this shaker. Since the wire wraps can be nominally static during operation, there may be less chance for the coil to fail due to vibration-induced fretting wear of the outer insulation that could otherwise lead to a short circuit.

[0077] While the above description provides examples of one or more apparatuses or methods, it will be appreciated that other apparatuses or methods may be within the scope of the accompanying claims.

Claims

CLAIMSWe claim:1 . An electromagnetic shaker apparatus, comprising: a body; a magnetic device housed within the body and configured to provide a static magnetic field; an armature; and a solenoid coil mounted on the armature and configured to receive current from a power supply, wherein interaction between the static magnetic field and the solenoid coil generates a Lorentz force that causes movement of the armature relative to the body.

2. The apparatus of claim 1 , wherein the magnetic device comprises a permanent magnet selected from the group consisting of samarium-cobalt magnet and alnico magnet.

3. The apparatus of claim 1 or 2, wherein the body is formed of a ferromagnetic material to direct the static magnetic field of the magnetic device.

4. The apparatus of any one of claims 1 to 3, wherein the body comprises a bottom wall, the magnetic device is mounted to the bottom wall, and the bottom wall comprises a plurality of holes.

5. The apparatus of any one of claims 1 to 4, wherein the body comprises an outer wall, the outer wall is cylindrical and defines a central axis.

6. The apparatus of claim 5, wherein the armature comprises a radial portion, and an axial portion that extends from the radial portion, the radial portion is centered relative to the central axis, the axial portion is cylindrical, and the solenoid coil is mounted to the axial portion of the armature.

7. The apparatus of claim 6, wherein the solenoid coil is offset radially inwardly relative to the outer wall to define a first gap.

8. The apparatus of claim 6 or 7, wherein the solenoid coil is formed of wire wound around the axial portion without adhesive.

9. The apparatus of claim 8, wherein the wire is selected from the group consisting of ceramic coated pure nickel wire and nickel-coated copper wire.

10. The apparatus of claim 6 or 7, wherein the solenoid coil is bonded to the axial portion of the armature with a ceramic cement.11 . The apparatus of any one of claims 6 to 10, wherein the radial portion of the armature comprises a plurality of perforations to reduce drag.

12. The apparatus of any one of claims 6 to 11 , comprising a top cap secured to the magnetic device and formed of a ferromagnetic material to direct the static magnetic field of the magnetic device.

13. The apparatus of claim 12, wherein the top cap is secured to the magnetic device by magnetic pull force, and the top cap comprises a recessed inner surface for positioning the magnet.

14. The apparatus of claim 12 or 13, wherein the top cap is adjacent to the solenoid coil and offset radially inwardly relative to the axial portion to define a second gap.

15. The apparatus of claim 14, wherein the top cap is positioned within an axial extent of the axial portion of the armature.

16. The apparatus of any one of claims 6 to 15, comprising at least one wafer spring coupling the body and the armature, the at least one wafer spring comprising an inner portion secured to the radial portion of the armature, and an outer portion secured to the outer wall of the body.

17. The apparatus of any one of claims 6 to 15, comprising at least one wafer spring coupling the top cap and the armature, the at least one wafer spring comprising an inner portion secured to the top cap, and an outer portion secured to the armature.

18. The apparatus of claim 16 or 17, wherein the at least one wafer spring has a generally open structure to reduce drag.

19. The apparatus of any one of claims 16 to 18, wherein the armature is arranged below the at least one wafer spring.

20. An apparatus, comprising: a body comprising a bottom wall, and a cylindrical outer wall extending upwardly from the bottom wall to define a central axis that is orthogonal to the bottom wall; a permanent magnetic device arranged in the body, mounted to the bottom wall and centered relative to the central axis, the permanent magnetic device selected from the group consisting of samarium-cobalt magnet and alnico magnet; an armature arranged in the body above the permanent magnet device, the armature comprising a radial portion that is centered relative to the central axis, and an axial portion that is cylindrical and extends downwardly from the radial portion; a solenoid coil mounted to the axial portion of the armature, the solenoid coil being offset radially inwardly relative to the outer wall of the body to define a first gap, the solenoid coil being configured to receive current from a power supply; and a top cap secured to the permanent magnet device and positioned axially intermediate the magnetic device and the radial portion of the armature, the top cap being adjacent to the solenoid coil and offset radially inwardly relative to the axial portion of the armature to define a second gap, the top cap being formed of a ferromagnetic material to direct a static magnetic field of the permanent magnet device.

21. An apparatus, comprising: a body comprising a cylindrical outer wall; a permanent magnetic device arranged in the body, the permanent magnetic device selected from the group consisting of samariumcobalt magnet and alnico magnet; first and second armatures arranged on opposing axial sides of the permanent magnet device, each of the armatures comprising a radial portion, and an axial portion that is cylindrical and extends from the radial portion; first and second solenoid coils mounted to the axial portion of the first and second armatures, respectively, each of the solenoid coils being offset radially inwardly relative to the outer wall of the body to define a first gap, each of the solenoid coils being configured to receive current from a power supply; and first and second end caps secured to the opposing axial sides of the permanent magnet device and positioned axially intermediate the magnetic device and the respective radial portion of the armature, each of the end caps being adjacent to the respective solenoid coil and offset radially inwardly relative to the axial portion of the respective armature to define a second gap, wherein the body and each of the end caps are formed of a ferromagnetic material to direct a static magnetic field of the permanent magnet device.

22. A fretting wear system, comprising: a testing environment; and at least one of the apparatus of any one of claims 1 to 21 housed within the high temperature environment, wherein the testing environment is one of an autoclave or a high temperature oven.

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