A split Hopkinson bar tensile-compressive system based on electromagnetic coil acceleration

Abstract

This invention discloses a Hopkinson bar tension / compression system based on electromagnetic coil acceleration. The system includes an electromagnetic coil winding, an armature, and a Hopkinson bar. The armature is sleeved outside the incident rod of the Hopkinson bar. The electromagnetic coil winding is disposed outside the armature. When the electromagnetic coil winding is energized, it drives the armature to impact the end of the incident rod furthest from the test sample to perform a Hopkinson bar tension test, or drives the armature to impact the end of the incident rod closest to the test sample to perform a Hopkinson bar compression test. This invention uses an electromagnetic coil winding to drive the armature to accelerate and impact the incident rod, thereby loading a stress wave. Compared to the method of compressed gas, the impact speed at the armature outlet is faster, and the speed of the incident rod can be precisely controlled simply by controlling the magnitude of the current within the electromagnetic coil winding.

Description

Technical Field

[0001] This invention relates to the field of dynamic mechanical property testing technology for materials, and in particular to a Hopkinson bar tension / compression system based on electromagnetic coil acceleration. Background Technology

[0002] In practical engineering applications, the mechanical properties of materials differ significantly under quasi-static and high-speed impact conditions, and the mechanical behavior of materials often varies under different strain rates. In order to meet the design and optimization requirements of material properties, it is essential to accurately and effectively test the dynamic mechanical properties of materials under high strain rates.

[0003] Currently, the split Hopkinson bar technique is widely used in the dynamic mechanical property testing of materials. However, this technique extensively uses compressed gas to accelerate a short bar, which then impacts the incident bar to generate an incident wave. The drawbacks of this method are: low exit velocity and low strain rate; inaccurate relationship between the incident bar velocity and gas pressure; low accuracy of the incident bar velocity; inability to precisely control the sample strain rate; and difficulty in adjusting the incident bar velocity as needed. Summary of the Invention

[0004] The purpose of this invention is to provide a Hopkinson rod tension / compression system based on electromagnetic coil acceleration, so as to provide a Hopkinson rod tension / compression system with high exit speed and precise control of incident rod speed.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a Hopkinson bar tension-compression system based on electromagnetic coil acceleration, the tension-compression system comprising: an electromagnetic coil winding, an armature, and a Hopkinson bar;

[0007] The armature is sleeved outside the incident rod in the Hopkinson rod;

[0008] The electromagnetic coil winding is disposed outside the armature;

[0009] When the electromagnetic coil winding is energized, the armature is driven to strike the end of the incident rod furthest from the test sample to perform a Hopkinson pull rod test, or the armature is driven to strike the end of the incident rod closest to the test sample to perform a Hopkinson compression rod test.

[0010] Optionally, the Hopkinson bar includes: an incident bar, a transmission bar, a buffer, an incident strain gauge, and a transmission strain gauge;

[0011] The incident rod and the transmission rod are coaxially arranged, and the test sample is coaxially connected between the incident rod and the transmission rod;

[0012] The buffer is disposed at the end of the transmission rod away from the test sample;

[0013] The incident strain gauge is disposed inside the incident rod, and the transmission strain gauge is disposed inside the transmission rod.

[0014] Optionally, during the Hopkinson bar test, the test sample is coaxially connected to the incident rod and the transmission rod via a connecting structure; the connecting structure is a thread or a snap-fit.

[0015] During the Hopkinson bar test, the two sides of the test sample are respectively attached to the end face of the incident bar and the end face of the transmission bar, and the attachment surfaces are perpendicular to the axis of the incident bar, the transmission bar and the test sample.

[0016] Optionally, the incident rod includes: a tension baffle, a compression baffle, a metal rod, an electromagnetic protective sleeve, and a vibration damping sleeve;

[0017] The tensile baffle is disposed at the end of the metal rod away from the test sample, and the compression baffle is disposed at the end of the metal rod close to the test sample;

[0018] The electromagnetic protective sleeve is fitted over the outside of the metal rod, and the vibration damping sleeve is positioned outside the electromagnetic protective sleeve.

[0019] Optionally, the electromagnetic protective sleeve is woven in a spiral 45-degree cross pattern.

[0020] Optionally, the incident rod further includes a first limiting spring and a second limiting spring sleeved on the metal rod;

[0021] The first limiting spring is located between one end of the tension baffle and the electromagnetic protective sleeve, and the second limiting spring is located between the other end of the compression baffle and the electromagnetic protective sleeve.

[0022] Optionally, the tension / compression system further includes a pulse power supply module;

[0023] Each coil in the electromagnetic coil winding is connected to the pulse power module.

[0024] Alternatively, the coils in the electromagnetic coil winding can be connected in phase groups, and each group of coils can be connected to the pulse power supply module.

[0025] Optionally, the pulse power module includes a pulse capacitor, a power switch, a host computer control system, and a charger;

[0026] The charger is connected to the pulse capacitor, and the charger is used to charge the pulse capacitor;

[0027] The two ends of the power switch are respectively connected between the pulse capacitor and the electromagnetic coil winding, and the control end of the power switch is connected to the host computer control system.

[0028] The host computer control system is used to control the energizing timing of the coils in the electromagnetic coil winding by controlling the state of the power switch.

[0029] Optionally, multiple coils in the same phase can be connected in series, in parallel, or in a hybrid series-parallel configuration.

[0030] The present invention also provides a Hopkinson bar.

[0031] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0032] This invention discloses a Hopkinson bar tension / compression system based on electromagnetic coil acceleration. The system includes an electromagnetic coil winding, an armature, and a Hopkinson bar. The armature is sleeved outside the incident rod of the Hopkinson bar. The electromagnetic coil winding is disposed outside the armature. When the electromagnetic coil winding is energized, it drives the armature to impact the end of the incident rod furthest from the test sample to perform a Hopkinson bar tension test, or drives the armature to impact the end of the incident rod closest to the test sample to perform a Hopkinson bar compression test. This invention uses an electromagnetic coil winding to drive the armature to accelerate and impact the incident rod, thereby loading a stress wave. Compared to the method of compressed gas, the impact speed at the armature outlet is faster, and the speed of the incident rod can be precisely controlled simply by controlling the magnitude of the current within the electromagnetic coil winding. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A schematic diagram of the structure of the Hopkinson bar tension / compression system based on electromagnetic coil acceleration provided in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the incident rod provided in an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the motion of the Hopkinson lever during the Hopkinson lever test provided in an embodiment of the present invention;

[0037] Figure 4This is a schematic diagram of the motion of the Hopkinson bar during the Hopkinson bar test provided in an embodiment of the present invention;

[0038] Figure 5 A circuit diagram showing the electromagnetic coil windings connected in a single-coil sequential discharge manner according to an embodiment of the present invention;

[0039] Figure 6 This is a circuit diagram showing the electromagnetic coil windings connected in phase groups according to an embodiment of the present invention.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1. Incident rod; 2. Transmission rod; 3. Test sample; 4. Buffer; 5. Incident strain gauge; 6. Transmission strain gauge; 7. Electromagnetic coil winding; 8. Armature; 9. Tension baffle; 10. Compression baffle; 11. Vibration damping sleeve; 12. Electromagnetic protection sleeve. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] The purpose of this invention is to provide a Hopkinson rod tension / compression system based on electromagnetic coil acceleration, so as to provide a Hopkinson rod tension / compression system with high exit speed and precise control of incident rod speed.

[0044] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] This invention provides a Hopkinson bar tension / compression system based on electromagnetic coil acceleration, such as... Figure 1 As shown, the tension-compression system includes: an electromagnetic coil winding 7, an armature 8, and a Hopkinson bar. The Hopkinson bar includes an incident bar 1, a transmission bar 2, a test sample 3, a buffer 4, an incident strain gauge 5, and a transmission strain gauge 6. Figure 2 As shown, the incident rod 1 includes a metal rod ( Figure 2 (Not shown in the image) Tension baffle 9, compression baffle 10, shock-absorbing sleeve 11, electromagnetic protection sleeve 12. The incident rod 1 and the transmission rod 2 are supported by multiple concentric bearings, allowing the incident rod 1 and the transmission rod 2 to slide freely and without damping along the axis.

[0046] The incident rod 1 is made of high-strength impact-resistant material. Near both ends of the incident rod 1, a disc-shaped tension baffle 9 and a compression baffle 10 are fixed, respectively. The diameter of the disc baffle is larger than the diameter of the armature. Between the tension baffle 9 and the compression baffle 10, outside the incident rod 1, from the inside out, are a metal rod, an electromagnetic protective sleeve 12, and a shock-absorbing sleeve 11. The distance between the baffle end face and the electromagnetic coil winding 7 is greater than the length of the armature 8. One end of the incident rod 1 contacts the test sample. The portion of the incident rod 1 located inside the electromagnetic coil winding 7 is wrapped with a sliding electromagnetic protective mesh sleeve, i.e., the electromagnetic protective sleeve 12. Limiting springs (a first limiting spring and a second limiting spring) are located on both sides of the electromagnetic protective mesh sleeve. The electromagnetic protective sleeve 12 is made of a high-permeability, low-density material, specifically woven into a mesh using a 45-degree spiral cross weave. This mesh is fitted onto the surface of the incident rod 1 to form the electromagnetic protective sleeve 12, and is fixed by the limiting springs fitted onto the surface of the incident rod 1. The outer diameter and mass of the incident rod 1 can be arbitrarily changed within the range of the inner diameter of the armature 8. The material and length of the incident rod 1 can also be arbitrarily changed as needed. The diameters of the incident rod 1 and the transmission rod 2 can be arbitrarily changed within the range of the inner diameter of the armature 8.

[0047] The end of the transmission rod 2 furthest from the sample is coaxially connected to the buffer 4, which serves to buffer the high-speed sliding of the transmission rod and protect the overall safety of the system.

[0048] In this embodiment of the invention, the electromagnetic coil winding 7 is a large-diameter hollow electromagnetic coil accelerator.

[0049] Driven by the electromagnetic coil accelerator, the armature 8 moves at high speed to the left or right along the axis and then strikes the tensile baffle 9 and the compression baffle 10 respectively, causing the incident rod 1 to move at high speed to the left or right. This subjects the adjacent test sample 3 to compressive or tensile impact, correspondingly loading compressive or tensile stress waves. The incident strain gauge 5 and the transmitted strain gauge 6 installed on the incident rod 1 and the transmission rod 2 are used to collect the stress waves and obtain the dynamic stress-strain curves of the material to evaluate the dynamic mechanical properties of the material. Specifically:

[0050] like Figure 3 As shown, during the Hopkinson bar test, the test sample 3 is coaxially and tightly fixed to the incident rod 1 and the transmission rod 2 via a threaded or snap-fit ​​connection structure. Driven by the electromagnetic coil accelerator, the armature 8 moves at high speed to the left along the axis and then impacts the tension baffle 9, causing the incident rod 1 to move to the left at high speed. This subjects the adjacent fixed test sample 3 and the transmission rod 2 to tensile impact. The incident strain gauge 5 and the transmission strain gauge 6 mounted on the incident rod 1 and the transmission rod 2 are used to collect stress waves and obtain the dynamic tensile stress-strain curves of the material to measure its dynamic tensile mechanical properties.

[0051] like Figure 4As shown, during the Hopkinson bar compression test, the two sides of the test sample 3 are smooth planes, respectively in contact with the incident bar 1 and the transmission bar 2, with the contact surfaces perpendicular to the axis. Driven by the electromagnetic coil accelerator, the armature 8 moves at high speed to the right along the axis and then impacts the compression baffle 10, causing the incident bar 1 to move at high speed to the right as a whole. This causes the adjacent test sample 3 and the transmission bar 2 to be subjected to compressive impact. The incident strain gauge 5 and the transmission strain gauge 6 mounted on the incident bar 1 and the transmission bar 2 are used to collect stress waves and obtain the dynamic compressive stress-strain curves of the material to measure its dynamic compressive mechanical properties.

[0052] This embodiment of the invention also includes a pulse power supply module, which comprises a pulse power supply, a power switch, a host computer control system, and a charger. In this embodiment, the charger is a high-power, high-voltage charger, the power switch is a high-voltage switch, and the pulse power supply is a pulse capacitor. The high-voltage switch is connected between the pulse power supply and the electromagnetic coil winding 7, and the host computer control system can control the high-voltage switch to be on or off. In this embodiment, "power supply" refers to the pulse power supply, and "power supply module" refers to the pulse power supply module.

[0053] The electromagnetic coil winding 7 is connected to a pulse power supply. The pulse excitation generates an Ampere force to drive the armature 8 to accelerate. The electromagnetic field can be adjusted by changing the polarity of the pulse power supply, the coil discharge sequence, and the initial position of the armature, thereby achieving the adjustment and control of the armature's left or right movement direction.

[0054] The connection between the electromagnetic coil winding 7 and the pulse power supply can be such that each coil is connected to a separate power supply, i.e., synchronous triggering, such as... Figure 5 As shown; alternatively, the power supply can be connected in phase groups, i.e., asynchronous triggering, such as... Figure 6 As shown, the circuit topology connected in groups can be series, parallel, or a hybrid series-parallel structure. When the first connection method is used, the armature movement direction is changed by altering the triggering sequence of the pulse power supply connected to each coil; when the second connection method is used, the same purpose is achieved by changing the phase sequence.

[0055] The first and second connection methods correspond to single-coil sequential continuous triggering and multi-coil group triggering, respectively. In the multi-coil group triggering mode, the armature can magnetically levitate and self-align. The electromagnetic coil acceleration adopts an electromagnetic traveling wave propulsion mechanism, which levitates and self-aligns the armature through electromagnetic induction flux compression. This avoids the friction and eccentricity problems existing in current electromagnetic acceleration and aerodynamic acceleration. At the same time, the electromagnetic force spatial distribution of the armature is more uniform, the radial drift amplitude of the armature is smaller, and the alignment accuracy is higher.

[0056] The electromagnetic coil winding 7 can be single-phase, two-phase, three-phase, or multi-phase. Taking three-phase as an example, the electromagnetic coil winding 7 is axially arranged from the end furthest from the sample to the end closest to the sample in the phase sequence A1\B1\C1\A2\B2\C2. When compression mode is required, the triggering sequence is A-phase-B-phase-C; when tension mode is required, the triggering sequence is C-phase-B-phase-A. The three-phase current flow path when using the three-phase drive is "positive power supply to A1+ to A1- to A2+ to A2- to negative power supply"; "positive power supply to B1+ to B1- to B2+ to B2- to negative power supply"; "positive power supply to C1+ to C1- to C2+ to C2- to negative power supply".

[0057] The pulse power supply module of this invention uses a pulse power supply to power the electromagnetic coil accelerator and a high-power high-voltage charger to charge the pulse power supply.

[0058] The pulse power supply can use a modular parallel connection of high-voltage capacitor banks. The capacitance and charging voltage can be flexibly adjusted as needed. There is an adjustable resistor in the power supply circuit. The above modules can be combined in various ways, and the speed or kinetic energy of the armature and incident rod can be arbitrarily adjusted.

[0059] The working principle of the Hopkinson rod tension-compression composite system based on electromagnetic coil acceleration provided in this embodiment of the invention is as follows:

[0060] The electromagnetic coil winding 7 is excited by pulse current according to different triggering sequences, thereby generating a changing magnetic field in space. The armature 8, made of conductive material, will generate induced eddy currents in the changing traveling wave magnetic field. According to Ampere's theorem, a conductive object carrying current will be subjected to electromagnetic force in a magnetic field, and the direction of the force follows the right-hand rule. Therefore, according to the above theorem and principle, the armature 8 will be subjected to axial thrust, and the armature 8 will accelerate under the action of axial thrust.

[0061] The force at a point on the surface of an object when it passes through a magnetic field is:

[0062]

[0063] in, The radial magnetic field at a certain current element on the object. It is a tangential current element at a certain point in the object. This represents the axial force experienced by the current element in the magnetic field.

[0064] In one specific implementation, the electromagnetic coil winding 7 adopts an asynchronous triggering method. Each electromagnetic coil accelerator contains six coils, which are axially arranged from the end furthest from the test sample to the end closest to the test sample in the phase sequence A1\B1\C1\A2\B2\C2.

[0065] The triggering sequence is A-phase - B-phase - C-phase. The armature 8 to be accelerated is placed in the electromagnetic coil accelerator, with its initial position fixed. An incident rod 1 is placed along the axis of the electromagnetic coil accelerator and the armature, with a compression baffle 10 and a tension baffle 9 placed at opposite ends of the metal rod in the incident rod 1. The coils of the same phase are connected to a power module (i.e., a pulse power module) according to the series circuit topology described above. The power module uses pulse capacitors for power supply, which are charged using a charger. A high-voltage switch controls the discharge sequence of the pulse capacitors; one high-voltage switch is used for each phase coil circuit, for a total of three high-voltage switches controlling the circuit. After the pulse capacitors are fully charged and reach the set voltage amplitude, the high-voltage switches are triggered to discharge according to the ABC phase sequence. Pulse excitation is applied to the six coils in sequence, with the armature mass set to 5.8 kg, the power module containing a 600 uF capacitor, and the voltage amplitude set to 10 kV. Calculation results show that the armature speed can reach approximately 158 m / s.

[0066] This invention can modify the coil triggering sequence, power supply polarity, initial position, etc., and change the armature movement direction to select impact compression baffle 10 or tension baffle 9. It uses a set of fixing devices to meet both tension and compression working requirements. By adjusting the primary energy scale, capacitance, voltage amplitude and other parameters in the circuit, it can autonomously control the exit speed of the load. The load mass and load exit speed are adjustable. According to actual needs, different diameter incident rods and transmission rods can be replaced within the range of electromagnetic coil accelerator and armature aperture size. It can measure samples of different sizes and can be flexibly adjusted according to usage requirements.

[0067] The Hopkinson rod tension / compression system based on electromagnetic coil acceleration provided in this invention only requires changing the triggering sequence of the coil excitation current to meet both tension and compression requirements with a single fixing device, making operation simple and convenient. Furthermore, the electromagnetic coil acceleration method uses electrical energy as the primary energy source, ensuring safety and controllability. The armature exit speed is higher than traditional acceleration methods, resulting in a higher test strain rate. The armature diameter, loading rod diameter, and armature exit kinetic energy can also be flexibly adjusted according to requirements. Compared with existing traditional technologies, its advantages are:

[0068] (1) The present invention uses electrical energy as the primary energy source, which is safer than the traditional compressed gas method.

[0069] (2) The present invention can meet both tension and compression working requirements with only one set of fixing device.

[0070] (3) The armature outlet impact speed of the present invention is faster, and a higher strain rate can be achieved.

[0071] (4) The present invention can more accurately control and adjust the armature exit speed, with higher precision.

[0072] (5) The outer diameter and mass of the armature of the present invention are adjustable within the range of the accelerator aperture, and the diameters of the incident rod and the transmission rod are adjustable within the range of the inner diameter of the armature.

[0073] (6) The electromagnetic protective sleeve of the present invention can effectively reduce the interference caused by pulsed electromagnetic force on the stress wave of the incident rod.

[0074] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0075] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A split Hopkinson bar tensile-compressive system based on electromagnetic coil acceleration, characterized in that, The tension / compression system includes: an electromagnetic coil winding, an armature, and a Hopkinson bar; The armature is sleeved outside the incident rod in the Hopkinson rod; The electromagnetic coil winding is disposed outside the armature; When the electromagnetic coil winding is energized, the armature is driven to strike the end of the incident rod away from the test sample to perform a Hopkinson pull rod test, or the armature is driven to strike the end of the incident rod close to the test sample to perform a Hopkinson compression rod test. The incident rod includes: a tension baffle, a compression baffle, a metal rod, an electromagnetic protective sleeve, and a vibration damping sleeve; The tensile baffle is disposed at the end of the metal rod away from the test sample, and the compression baffle is disposed at the end of the metal rod close to the test sample; The electromagnetic protective sleeve is fitted over the outside of the metal rod, and the vibration damping sleeve is disposed outside the electromagnetic protective sleeve; The incident rod also includes a first limiting spring and a second limiting spring sleeved on the metal rod; The first limiting spring is located between one end of the tension baffle and the electromagnetic protective sleeve, and the second limiting spring is located between the other end of the compression baffle and the electromagnetic protective sleeve; The tension / compression system also includes a pulse power supply module; Each coil in the electromagnetic coil winding is connected to the pulse power module. Alternatively, the coils in the electromagnetic coil winding can be connected in phase groups, and each group of coils can be connected to the pulse power supply module.

2. The electromagnetic coil acceleration based split Hopkinson bar tensile-compressive system of claim 1, wherein, The Hopkinson bar includes: an incident bar, a transmission bar, a buffer, an incident strain gauge, and a transmission strain gauge; The incident rod and the transmission rod are coaxially arranged, and the test sample is coaxially connected between the incident rod and the transmission rod; The buffer is disposed at the end of the transmission rod away from the test sample; The incident strain gauge is disposed inside the incident rod, and the transmission strain gauge is disposed inside the transmission rod.

3. The Hopkinson rod tension / compression system based on electromagnetic coil acceleration according to claim 2, characterized in that, During the Hopkinson bar test, the test sample is coaxially connected to the incident rod and the transmission rod via a connecting structure; the connecting structure is either threaded or snap-fit. During the Hopkinson bar test, the two sides of the test sample are respectively attached to the end face of the incident bar and the end face of the transmission bar, and the attachment surfaces are perpendicular to the axis of the incident bar, the transmission bar and the test sample.

4. The Hopkinson rod tension / compression system based on electromagnetic coil acceleration according to claim 1, characterized in that, The electromagnetic protection sleeve is woven in a spiral 45-degree cross pattern.

5. The Hopkinson rod tension / compression system based on electromagnetic coil acceleration according to claim 1, characterized in that, The pulse power module includes a pulse capacitor, a power switch, a host computer control system, and a charger. The charger is connected to the pulse capacitor, and the charger is used to charge the pulse capacitor; The two ends of the power switch are respectively connected between the pulse capacitor and the electromagnetic coil winding, and the control end of the power switch is connected to the host computer control system. The host computer control system is used to control the energizing timing of the coils in the electromagnetic coil winding by controlling the state of the power switch.

6. The Hopkinson rod tension / compression system based on electromagnetic coil acceleration according to claim 5, characterized in that, Multiple coils in the same phase can be connected in series, in parallel, or in a mixed series-parallel connection.

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