CN103926138B - Based on Hopkinson strut and tie stress wave generator and the experimental technique of electromagnetic force - Google Patents
Based on Hopkinson strut and tie stress wave generator and the experimental technique of electromagnetic force Download PDFInfo
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Abstract
A kind of Hopkinson strut and tie stress wave generating means based on electromagnetic force and method.Stress wave generating means is by loading rifle and electric power system forms.Electric power system is used for providing instantaneous heavy current to the main coil loading rifle, thus make to produce between main coil and secondary coil strong electromagnetic repulsion due to capacitor discharge time shorter, discharge current is strong, the strong repulsion producing moment between main coil and secondary coil can be made, thus produce strong stress pulse, after tapered amplifier amplifies, export to Hopkinson bar.The present invention makes it be applied to the loading of split hopkinson press bar and pull bar by improving the structure of electromagnetic rivet driver, the loading system of Hopkinson pressure bar and pull bar can be realized on same device simultaneously, have simple to operate, that controllability is strong feature.
Description
Technical field
The present invention relates to stress wave generating means and the method for the dynamic mechanical test of material, be a kind of stress wave generating means based on electromagnetic force and method specifically, described device can as the stress wave input media of separate type Hopkinson pull rod and depression bar.
Background technology
At present, most popular when measuring the mechanical property of material under high strain-rate in material science is exactly split hopkinson press bar technology and pull bar technology.The ultimate principle of this method is: be placed in by short sample between two pull bars or depression bar, by certain mode to incident bar input tensile stress wave or compression stress wave, loads sample.Utilize to be bonded on pull bar or depression bar simultaneously and also carry out recording pulse signal apart from the foil gauge of boom end certain distance.If pull bar or depression bar keep elastic stage, the pulse so in bar will with elastic wave velocity undistorted propagate.The foil gauge be pasted onto like this on pull bar or depression bar just can measure the load course over time acting on rod end.
For Hopkinson pressure bar, the universal way producing incident wave is by air gun by drop bar transmitted at high speed, produces incident pulse with incident bar Impinging coaxial.The shortcoming of this method is: during owing to launching at every turn, the installation site of drop bar in air gun is not quite similar, and the corresponding relation of stroke speed and air pressure is difficult to determine, therefore the amplitude of incident wave cannot be controlled exactly, so need to attempt many experiments just can obtain required rate of strain.Secondly, for the experiment that rate of strain span is excessive, due to the restriction of air gun air pressure, need the length changing drop bar to obtain different rate of strain, rate of strain is higher, and drop bar used is shorter, and the stress wave width produced in experiment is shorter, which limits the range of strain that experiment obtains, and complex operation.The more important thing is, the emission rate due to drop bar has a lower limit, and some lower rate of strain cannot obtain with traditional Hopkinson pressure bar in actual tests, such as 10s
-1rate of strain.Because different experimental system parameters is also different, make the standardization of split hopkinson press bar experimental technique be an international difficult problem always.
For Hopkinson pull rod, currently used general loading technique is: the drop bar of pull bar is made hollow circular-tube, by air gun by impact tube transmitted at high speed, when its motion arrives incident bar end, the boss of impact tube and incident rod end collides generation one row wave of compression and propagates to incident bar boss end, and being reflected into stretching ripple at free end, this stretching ripple is loaded sample by incident bar.But this method for designing has a lot of shortcomings: 1, because drop bar is transmitted into the other end from incident bar one end, so boss on incident bar is to that section of air gun, incident bar is in unsupported free state, and this makes incident bar easily bend; 2, this design limits the length of impacting tube at about 500mm, so the incident wave length produced is about 0.2ms, but for ductile material and the experiment of low strain dynamic rate, needs the incident wave more grown; 3, the replacing of impacting tube is very inconvenient; 4, because the wall thickness of impacting tube limits, need very high air pressure to carry out accelerating impact cylinder.Also have a lot of scholar to propose different mentalities of designing: 1, add a boss in one end of impacting tube to improve the emission rate of impacting tube, but the waveform that this mode produces is no longer regular by boss affects; 2, use empty incident bar, drop bar passes inside incident bar, and this mode makes wave shaping become difficulty.
Because the shape of drop bar is different, the position of air gun is different, and traditional Hopkinson pressure bar and the loading system of pull bar cannot realize on same device.
The sixties in 20th century, Boeing Co. was for solving common riveted joint Problems existing, to be taken the lead in beginning one's study Electromagnetic riveting technology, and applied for the patent of thump electromagnetic riveting device in nineteen sixty-eight by people such as HuberASchmitt.Within 1986, ZievePeter succeeds in developing low voltage electromagnetic riveted joint, solves high pressure and is riveted on riveting quality and applies aspect Problems existing, thus Electromagnetic riveting technology is comparatively fast developed.Electromagnetic riveting technology is applied in Boeing, the manufacture of Air Passenger series aircraft.Nowadays, low voltage electromagnetic riveting technology is full-fledged, and the size of rivet force and duration can obtain more accurate control.The know-why of electromagnetic rivet driver is: between discharge coil and workpiece, add a coil and Stress-amplifier.The moment that discharge switch is closed, by fast-changing dash current in main coil, around coil, produce high-intensity magnetic field.The secondary coil be coupled with main coil produces induction current under strong magnetic field action, and then produces eddy current magnetism, and two magnetic field interactions produce eddy current repulsion, and reach rivet by amplifier, and rivet is shaped.The very high frequency of eddy current power, propagates with the form of stress wave in amplifier and rivet, therefore electromagnetic riveting also claims stress wave to rivet.Air gun in traditional split hopkinson press bar and drop bar is replaced if the principle of electromagnetic rivet driver be applied in split hopkinson press bar, produced by electromagnetic repulsion force and directly produce stress wave, the standardization of split hopkinson press bar experimental technique will be made to become possibility.And the loading of low strain dynamic rate can be carried out with sufficiently long stress pulse to sample, realize the low strain dynamic rate that some traditional Hopkinson bars cannot realize.Northwestern Polytechnical University is propose a kind of split hopkinson press bar device loaded based on electromagnetic force in the innovation and creation of 201410161610.X at application number, and this experimental provision is by directly applying to Hopkinson pressure bar experiment device by electromagnetic rivet driver device thus realizing loading the dynamic compression of sample.But more wish in reality to use same charger, both can realize compression-loaded, and can tensile loads be realized again.
Summary of the invention
Be difficult to control for overcoming the incident wave amplitude existed in prior art, complex operation and range of strain limit and cannot realize the deficiency of some low strain dynamic rates experiment, and Tension and Compression charger cannot be unified shortcoming, the present invention proposes a kind of Hopkinson strut and tie stress wave generating means based on electromagnetic force and method.
The described Hopkinson strut and tie stress wave generator based on electromagnetic force comprises power supply, capacitor charger and loading rifle.Described capacitor charger adopts the power pack of existing electromagnetic rivetter, and is connected with the electrode line loading rifle by the positive pole output line of the output of described capacitor charger, and negative pole output line connects with the negative line loading rifle.Load rifle and comprise stretching head, insulation course, loading rifle housing, main coil, secondary coil and compressing head.Stretching head is positioned at described loading rifle housing and is arranged on this loading rifle shell one end; Locating shaft on this stretching head is also positioned at and loads rifle housing and with to load rifle housing coaxial.Main coil, compressing head, two insulation courses and two secondary coils are all sleeved on the locating shaft on described stretching head, and compressing head is positioned at the loading rifle housing other end.Two insulation courses are fitted with the inside surface of described stretching head or compressing head respectively; Two secondary coils lay respectively at inside described each insulation course; The via hole of two external connectors of main coil is had at the circumferential surface loading rifle housing the same side.The external peripheral surface of stretching head and the external peripheral surface of compressing head all coordinate with the internal surface gaps loading rifle housing.
The circumferential surface of stretching head one end is made up of isometrical section and cone section; The axial length of described isometrical section: the axial length=1:1 of cone section.Isometrical section of described stretching head is stress wave receiver section, and the cone section of described stretching head is that stress wave amplifies reflection end.The largest diameter of stress wave receiver section, and the locating shaft axially protruded is had at the end face center of stress wave receiver section; The center that stress wave amplifies reflection end is plane, defines the minimum diameter of stretching head at this place.The diameter of described stretching head stress wave receiving end: stress wave amplifies the ratio=12:1 at the minimum diameter place of reflection end.The tapering that described stress wave amplifies the cone section of reflection end is 30 ゜;
The circumferential surface of compressing head one end is made up of isometrical section and cone section; The axial length of described isometrical section: the axial length=1:1 of cone section.In the present embodiment, isometrical section of compressing head is 25mm with the axial length of cone section.The end face of isometrical section is plane, is stress wave receiving end; The circumferential surface of cone section is that stress wave amplifies end; The coupling shaft axially protruded is had at the center of this conical surface.Have for connecting into the internal thread penetrating bar in described coupling shaft termination.Described stress wave amplifies holds the tapering for the conical surface to be 30 ゜.The maximum gauge of described compressing head: the ratio=12:1 of the minimum diameter at conical surface place.The endoporus of compressing head coordinates with the locating shaft of stretching head, and clearance fit between the two.
The present invention also proposes a kind of experimental technique of the Hopkinson strut and tie stress wave generator based on electromagnetic force, comprises Hopkinson compression experiment and Hopkinson stretching experiment.The experimentation of the described Hopkinson strut and tie stress wave generator based on electromagnetic force is:
Step 1. is arranged equipment.
Sequentially be arranged on coaxial according to a conventional method to loading rifle, incident bar and transmission bar on experiment table, and described incident bar and transmission bar are only moved freely at axis direction.Load the one end at the compressing head place of rifle near incident bar.A sample is arranged between incident bar and transmission bar, and make sample and incident bar and transmission bar coaxial.
Step 2. pastes foil gauge.
Conventional method is adopted to paste 2 foil gauges respectively at incident bar or transmission bar, and access data acquisition system that foil gauge is gone between; During described foil gauge of arranging lead-in wire, described each foil gauge lead-in wire must be distributed with the axis being parallel of incident bar or transmission bar, then draw perpendicular to axis direction bending at a right angle, make foil gauge lead-in wire linear state access data collector
Step 3. loading experiment and data acquisition.
When carrying out Hopkinson compression experiment, by stretching head pull-out along loading gun axis line pull-out, make the distance L between stretching head and main coil
1for 30mm.The stress wave of compressing head is amplified end be connected with the incident bar of Hopkinson pressure bar; After capacitor charger charging, make capacitor charger to the main coil electric discharge loading rifle, electromagnetic repulsion force is produced between compressing head and main coil, described electromagnetic repulsion force shows as compression stress wave in compressing head inside and forms incident wave after being amplified by compressing head, this incident wave imports the incident bar of Hopkinson pressure bar into, when this incident wave reaches incident bar and sample contacts face, because wave impedance is not mated, a part for this incident wave is reflected, reflection wave is formed in incident bar, another part is then transmitted in transmission bar by sample, forms transmitted wave.The shape of described reflection wave and transmitted wave and amplitude are determined by sample material character.Incident wave and reflection wave signal are recorded by the foil gauge be pasted onto on incident bar by data acquisition unit, are recorded by the signal of transmitted wave by being pasted onto the foil gauge on transmission bar.Utilize reflection wave and the transmitted wave signal of data acquisition unit record, obtained the dynamic compressing stress strain curve of test specimen by a ripple method.
When carrying out Hopkinson stretching experiment, adjustment stretching head, makes this stretching head and main coil be adjacent to, and makes the through hole of locating shaft through compressing head of stretching head, the locating shaft of stretching head is connected with the incident bar of Hopkinson pull rod by screw thread, the distance L of adjustment compressing head and main coil
2for 30mm.After capacitor charger charging, this capacitor charger is to the main coil electric discharge loading rifle, electromagnetic repulsion force is produced between stretching head and main coil, described electromagnetic repulsion force shows as compression stress wave in stretching head inside, described compression stress wave is exaggerated in stretching head, and be reflected into stretching ripple at the small end of stretching head and form the incident wave of Hopkinson pull rod, this incident wave imports the incident bar of Hopkinson pull rod into, when this incident wave reaches incident bar and sample contacts face, because wave impedance is not mated, a part for this incident wave is reflected, reflection wave is formed in incident bar, another part is then transmitted in transmission bar by sample, form transmitted wave.The shape of described reflection wave and transmitted wave and amplitude are determined by sample material character.Incident wave and reflection wave signal are recorded by the foil gauge be pasted onto on incident bar by data acquisition unit, are recorded by the signal of transmitted wave by being pasted onto the foil gauge on transmission bar.Utilize reflection wave and the transmitted wave signal of data acquisition unit record, obtained the dynamic tensile stress-strain diagram of material by a ripple method.
In the present invention, stress wave generating means is by loading rifle and electric power system forms.Electric power system is used for providing instantaneous heavy current to the main coil loading rifle, thus makes to produce strong electromagnetic repulsion between main coil and secondary coil.Load rifle to be made up of main coil, compressing head and stretching head, be used for producing electromagnetic repulsion force, and convert electromagnetic repulsion force to stress wave, after tapered amplifier amplifies, export to Hopkinson bar.
The present invention directly produces stress wave by electromagnetic repulsion force, and in loading rifle, have a main coil and two secondary coils, main coil and rifle body are fixed, and are positioned at the interlude of rifle body, and there is through hole at main coil center, are used for locating with compressing head or stretching head; Two secondary coils are copper disk, and be respectively connected a tapered amplifier, are used for respectively producing wave of compression and stretching ripple, are called compressing head and stretching head, and close with main coil.Main coil and compressing head and stretching head coaxial, its right alignment to be coordinated with the through hole of main coil by stretching head and the locating shaft of compressing head to be determined.When compressing head is installed, the small end of conical head is near the incident bar of Hopkinson pressure bar; When stretching head is installed, the small end of conical head is away from the incident bar of Hopkinson pull rod, and its locating shaft is through the through hole of main coil, and is threaded connection at the incident bar of the other end and Hopkinson pull rod.During experiment, strong variable-current is passed through main coil, the high-intensity magnetic field that main coil can change, the high-intensity magnetic field of change can produce induction current in secondary coil, the induced field direction that induction current produces is contrary with the magnetic direction of main coil, so produce electromagnetic repulsion force between main coil and secondary line level circle, this electromagnetic repulsion force shows as compression stress wave in secondary coil, this compression stress wave is amplified by circular cone, if compressing head is connected by threaded coaxial with the incident bar of Hopkinson pressure bar, compression stress wave then in compressing head directly imports the incident bar of Hopkinson pressure bar into, just can carry out compression test to material, if stretching head is connected by threaded coaxial with the incident bar of Hopkinson pull rod, then the wave of compression of stretching head inside becomes the stretching ripple of constant amplitude after the reflection of conical head small end, and change the direction of propagation, imported into the incident bar of Hopkinson pull rod by the locating shaft of stretching head, just can carry out dynamic tensile loading to material.Therefore this device both can carry out compression experiment to material, can carry out stretching experiment again.
There is provided power supply by the electric discharge of capacitor circle of serving as theme, because capacitor discharge time is shorter, discharge current is strong, can make the strong repulsion producing moment between main coil and secondary coil, thus produce strong stress pulse.As for the charging and discharging control system of capacitor, in electromagnetic rivetter, this technology is very ripe at present, can directly apply.
The incident bar of stretching head or compressing head and Hopkinson bar is threaded connection, and enables the stress wave of output stably import experimental system into.In experimental provision of the present invention, directly produce stress pulse by the electromagnetic repulsion force loaded between main coil in rifle and secondary coil, be input to incident bar, make produced pulse signal can experimentally person needs and control more exactly.
In the present invention, the actual stress wave amplitude produced can be controlled by the charging voltage of electromagnetic riveting device, and the actual stress wave width produced can be controlled by the capacitance of adjustment electromagnetic riveting device.
The present invention makes it be applied to the loading of split hopkinson press bar and pull bar by improving the structure of electromagnetic rivet driver, and the loading system of Hopkinson pressure bar and pull bar can be realized on same device simultaneously.Electromagnetic repulsion force combines with capacitor discharge by the present invention in principle, to replace the air gun in traditional split hopkinson bar system and bullet and directly to produce stress pulse.Adopt traditional Hopkinson bar sample, the loading under expection pulse amplitude and pulse width can be carried out material.Equipment whole system is simple to operate, and controllability is strong.Owing to being controlled by the corresponding Reeb of electromagnetic mode, when the capacitance in capacitor charger is constant, the output stress wave amplitude that same voltage is corresponding is also constant, when charging voltage is constant, the stress wave width that same capacitance is corresponding is also constant, so the accurate control of corresponding Reeb can be realized, experiment reproducible, secondly, owing to being the stress wave being loaded generation by electromagnetism, the width of stress pulse is impacted the restriction of pole length unlike tradition clashes into mode, so test for low strain dynamic rate, the strain ratio tradition Hopkinson bar that the present invention can reach is larger, such as, the present invention can produce the stress wave that pulse width is 0.5ms, if to carry out the compression test under 100s-1 rate of strain to sample with this stress wave, the maximum strain that then sample can reach is 0.05, and for traditional Hopkinson bar, be difficult to reach so low rate of strain, even if this rate of strain can be reached, bullet used is 0.8m, the stress pulse width then produced is 0.32ms, the maximum strain that then sample reaches is 0.032, be starkly lower than the Hopkinson bar that electromagnetism loads.Due to above advantage, apparatus of the present invention and method can realize traditional split hopkinson bar and test be beyond one's reach rate of strain and range of strain, make the standardization of Hopkinson bar experimental technique, and make the experimental provision of pull bar and depression bar realize integration, save the complicacy of equipment and take up an area space.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of the Hopkinson strut and tie stress wave generator based on electromagnetic force;
Fig. 2 is the structural representation of the Hopkinson strut and tie stress wave generator based on electromagnetic force;
Fig. 3 is the inner structure schematic diagram loading rifle, and its middle shell is cut open along symmetrical plane;
Fig. 4 is the structural representation of compressing head;
Fig. 5 is the structural representation of stretching head;
Fig. 6 is compression test schematic diagram;
Fig. 7 is tension test schematic diagram;
Fig. 8 is the location mode of foil gauge lead-in wire;
Fig. 9 is the stress signal that general foil gauge lead mode for cloth measures, wherein abscissa representing time, and unit is s, and ordinate represents stress, and unit is Mpa;
Figure 10 is the stress signal adopting the foil gauge lead mode for cloth in the present invention to measure, and wherein abscissa representing time, unit is s, and ordinate represents stress, and unit is Mpa.Wherein:
1. resistance; 2. transformer; 3. rectifier; 4. electric capacity; 5. electronic switch; 6. load rifle; 7. stretching head; 8. insulation course; 9. housing; 10. main coil; 11. secondary coils; 12. compressing heads; 13. incident bars; 14. samples; 15. transmission bars; 16. foil gauges; 17. data acquisition units; 18. impact dampers; 19. power supplys; 20. capacitor chargers; 21. through holes; 22. screw threads; 23. locating shafts; 24. lead-in wires.
Embodiment
Embodiment one
The present embodiment is a kind of Hopkinson strut and tie stress wave generator based on electromagnetic force, comprises power supply 19, capacitor charger 20 and loads rifle 6.Capacitor charger 20 adopts the power pack of existing electromagnetic rivetter, and is connected with the electrode line loading rifle 6 by the positive pole output line of the output of described capacitor charger 20, and negative pole output line connects with the negative line loading rifle 6.Power supply 19 adopts the three-phase alternating current of 220V.
In the present embodiment, capacitor charger 20 adopts and is published in the power pack that the patent No. is the electromagnetic rivetter in the patent of 200520079179, in the present embodiment, the electrochemical capacitor of 2000 microfarads that to be 1000 volts of rated capacities by 10 rated voltages be composes in parallel Capacitor banks, described Capacitor banks and electronic switch are arranged in condenser box, by the electric discharge of electronic switch control capacitor group.Control box mainly comprises PLC and control system thereof.Control system forms primarily of simulation control part, digital control part and digital display portion.Wherein simulation control part adopts the TCA785 chip of SIEMENS company.Digital control part exports expansion module EM235 by the serial CPU224 of the S7-200 of Siemens and Siemens's analog input and forms.Charging voltage controls mainly to be realized by the pid control mode of Voltage loop and electric current loop.Digital display portion is mainly by S7-200 series text display TD200 composition.
As shown in Figure 3.Load rifle to be made up of stretching head 7, insulation course 8, loading rifle housing 9, main coil 10, secondary coil 11 and compressing head 12.Described loading rifle housing 9 is carrier, and stretching head 7 is positioned at described loading rifle housing and is arranged on this loading rifle shell one end; Locating shaft on this stretching head is also positioned at and loads rifle housing and coaxial with loading rifle housing, both for the transmission of tensile stress wave, again for the location of main coil 10 and secondary coil 11.
Main coil 10 to be sleeved on the locating shaft on described stretching head and to be positioned at and loads rifle housing stage casing.Compressing head 12 to be sleeved on the locating shaft on described stretching head and to be positioned at and loads the rifle housing other end.The insulation course 8 that two nylon is made is sleeved on the locating shaft on described stretching head, and fit with the inside surface of described stretching head 7 or compressing head 12 respectively, stop the inductive loop produced in secondary coil 11 to import compressing head 12 or stretching head 7 into by described insulation course 8.Two secondary coils 11 are sleeved on the locating shaft on described stretching head, and lay respectively at inside described each insulation course.Have two through holes at the circumferential surface loading rifle housing 9 the same side, two external connectors of main coil 10 are each passed through one of them through hole and are fixed on the outside surface loading rifle housing 9.Positive terminal in two external connectors of described main coil 10 is connected with the positive pole output line of capacitor charger 20, and the anode connector in two external connectors is connected with the negative pole output line of capacitor charger 20.
In the present embodiment, load the nylon manufacture that rifle housing 9 adopts insulating property good.The main coil 10 of this loading rifle adopts wide 25mm, to be wound on xsect be on I-shaped core body to the copper strips of thick 1mm.The external diameter of main coil 10 is identical with the internal diameter loading rifle housing 9, loads after in rifle housing 9, interference engagement between the two when this main coil 10 loads.
Secondary coil 11 has 2, is copper disk, and has axis hole at the center of this secondary coil.
Stretching head 7 is solid of revolution.One end of stretching head 7 is circular block, and this circular block circumferential surface is made up of isometrical section and cone section; The axial length of described isometrical section: axial length=1:1 that cone section is.In the present embodiment, the axial length of isometrical section of described stretching head 7 and the axial length of cone section are 25mm.Isometrical section of described stretching head 7 is stress wave receiver section, and the cone section of described stretching head is that stress wave amplifies reflection end.The largest diameter of stress wave receiver section, and the locating shaft axially protruded is had at the end face center of stress wave receiver section; The center that stress wave amplifies reflection end is plane, defines the minimum diameter of stretching head 7 at this place.The diameter of described stretching head stress wave receiving end: stress wave amplifies the ratio=12:1 at the minimum diameter place of reflection end.The tapering that described stress wave amplifies the cone section of reflection end is 30 ゜; The locating shaft 23 of described stretching head is clearance fit with the through hole of main coil 10.Blind screw hole is processed with, for coordinating with the incident bar 13 of Hopkinson pull rod at the circumferential surface of this locating shaft end.
Compressing head 12 is hollow solid of revolution.The circumferential surface of compressing head one end is made up of isometrical section and cone section; The axial length of described isometrical section: the axial length=1:1 of cone section.In the present embodiment, isometrical section of compressing head is 25mm with the axial length of cone section.The end face of isometrical section is plane, is stress wave receiving end; The circumferential surface of cone section is that stress wave amplifies end; The coupling shaft axially protruded is had at the center of this conical surface.Have for connecting into the internal thread penetrating bar in described coupling shaft termination.Described stress wave amplifies holds the tapering for the conical surface to be 30 ゜.The maximum gauge of described compressing head: the ratio=12:1 of the minimum diameter at conical surface place.The endoporus of compressing head 12 coordinates with the locating shaft of stretching head 7, and clearance fit between the two.
Power supply 19 in the present embodiment, incident bar 13, transmission bar 15, foil gauge 16, data acquisition unit 17 and impact damper 18 all adopt prior art.And the external thread coordinated with the smaller diameter end of compressing head is processed with in one end of incident bar 13.
The present embodiment also proposed a kind of described experimental technique based on the Hopkinson strut and tie stress wave generator of electromagnetic force.The experimental technique of the described Hopkinson strut and tie stress wave generator based on electromagnetic force comprises Hopkinson compression experiment and Hopkinson stretching experiment.
I detailed process adopting the Hopkinson strut and tie stress wave generator based on electromagnetic force to carry out Hopkinson compression experiment is:
Step 1. is arranged equipment.
Sequentially be arranged on coaxial according to a conventional method to loading rifle 6, incident bar 13 and transmission bar 15 on experiment table, and described incident bar 13 and transmission bar 15 are only moved freely at axis direction.Load the one end at compressing head 12 place of rifle 6 near incident bar 13.A sample 14 is arranged between incident bar 13 and transmission bar 15, and make sample 14 and incident bar 13 and transmission bar 15 coaxial.
Step 2. pastes foil gauge.
The method of attaching of foil gauge adopts prior art, namely the half length place of incident bar 13 or transmission bar 15 circumferentially with described incident bar or transmission bar axis for axis of symmetry, identical for two panels parameter foil gauge symmetry is pasted onto incident bar or transmission bar surface, weld strain sheet lead-in wire 24 on the pin of foil gauge, and by the Wheatstone bridge in described foil gauge lead-in wire access data acquisition system.
Described foil gauge lead-in wire 24 be placed with particular/special requirement, otherwise data acquisition unit 17 can be made to be subject to electromagnetic interference (EMI) and cannot normal acquisition experimental data.If the projection of foil gauge lead-in wire 24 in the plane perpendicular to incident bar or transmission bar axis forms closed-loop path, when then loading rifle 6 electric discharge generation high-intensity magnetic field, the loops that the magnetic field line changed can be formed through foil gauge lead-in wire 24, make the magnetic flux changed in loop, thus formation induction current, interference is produced to data acquisition unit 17, gathered data cannot be used.Solution to this problem is: as shown in Figure 8, described each foil gauge lead-in wire 24 is first made to distribute with the axis being parallel of incident bar or transmission bar, draw perpendicular to axis direction bending at a right angle again, make lead-in wire 24 linear state access data collector 17, induction current would not be produced because of magnetic flux change in lead-in wire like this.As can be seen from Fig. 9 and Figure 10, the general interference of the stress wave signal measured by foil gauge lead mode for cloth is very large, and adopts the interference of the stress wave signal measured by foil gauge lead mode for cloth proposed by the invention to eliminate completely.
Step 3. carries out loading and processing data.
As shown in Figure 6, stretching head 7 is pulled out, make the distance L between stretching head and main coil
1for 30mm.The small end of compressing head 12 is threaded with the incident bar of Hopkinson pressure bar, capacitor charger 20 charging voltage is set to 200V and charges, to be charged complete after, by electronic switch, capacitor charger is discharged to the main coil 10 loading rifle, electromagnetic repulsion force will be produced between compressing head 12 and main coil 10, described electromagnetic repulsion force shows as compression stress wave in compressing head 12 inside and forms incident wave after being amplified by compressing head 12, this incident wave imports the incident bar 13 of Hopkinson pressure bar into, when this incident wave reaches incident bar 13 with sample 14 surface of contact, because wave impedance is not mated, a part for this incident wave is reflected, reflection wave is formed in incident bar 13, another part is then transmitted in transmission bar 15 by sample 14, form transmitted wave.The shape of described reflection wave and transmitted wave and amplitude are determined by sample material character.
Incident wave and reflection wave signal are recorded by the foil gauge 16 be pasted onto on incident bar 13 by data acquisition unit 17, are recorded by the signal of transmitted wave by the foil gauge 16 be pasted onto on transmission bar 15.The reflection wave utilizing data acquisition unit 17 to record and transmitted wave signal, obtain the dynamic compressing stress strain curve of test specimen by a ripple method.
II detailed process adopting the Hopkinson strut and tie stress wave generator based on electromagnetic force to carry out Hopkinson stretching experiment is:
Step 1. is arranged equipment.
By loading rifle 6, incident bar 13 and transmission bar 15 according to a conventional method coaxial order be arranged on experiment table, enable described incident bar 13, transmission bar 15 only move freely at axis direction.Load the one end at compressing head 12 place of rifle 6 near incident bar 13.A sample 14 is arranged between incident bar 13 and transmission bar 15, and make sample 14 and incident bar 13 and transmission bar 15 coaxial.
Step 2. pastes foil gauge.
The method of attaching of foil gauge adopts prior art, namely the half length place of incident bar 13 or transmission bar 15 circumferentially with described incident bar or transmission bar axis for axis of symmetry, identical for two panels parameter foil gauge symmetry is pasted onto incident bar or transmission bar surface, weld strain sheet lead-in wire 24 on the pin of foil gauge, and by the Wheatstone bridge in described foil gauge lead-in wire access data acquisition system.
Described foil gauge lead-in wire 24 be placed with particular/special requirement, otherwise data acquisition unit 17 can be made to be subject to electromagnetic interference (EMI) and cannot normal acquisition experimental data.If the projection of foil gauge lead-in wire 24 in the plane perpendicular to incident bar or transmission bar axis forms closed-loop path, when then loading rifle 6 electric discharge generation high-intensity magnetic field, the loops that the magnetic field line changed can be formed through foil gauge lead-in wire 24, make the magnetic flux changed in loop, thus formation induction current, interference is produced to data acquisition unit 17, gathered data cannot be used.Solution to this problem is: as shown in Figure 8, described each foil gauge lead-in wire 24 is first made to distribute with the axis being parallel of incident bar or transmission bar, draw perpendicular to axis direction bending at a right angle again, make lead-in wire 24 linear state access data collector 17, induction current would not be produced because of magnetic flux change in lead-in wire like this.As can be seen from Fig. 9 and Figure 10, the general interference of the stress wave signal measured by foil gauge lead mode for cloth is very large, and adopts the interference of the stress wave signal measured by foil gauge lead mode for cloth proposed by the invention to eliminate completely.
Step 3. carries out loading and image data.
As shown in Figure 7, stretching head 7 is pushed, make the distance between adjustment stretching head and main coil, stretching head is made to be adjacent to main coil, and make the through hole 21 of locating shaft through compressing head 12 of this stretching head, be connected with the incident bar 13 of Hopkinson pull rod by screw thread by the locating shaft 23 of stretching head 7, adjustment compressing head 12 and the distance of main coil 10, make L
2for 30mm.Capacitor charger 20 charging voltage is set to 200V and charges, to be charged complete after, by electronic switch, capacitor charger is discharged to the main coil 10 loading rifle, electromagnetic repulsion force will be produced between stretching head 7 and main coil 10, described electromagnetic repulsion force shows as compression stress wave in stretching head 7 inside, described compression stress wave is exaggerated in stretching head 7, and be reflected into stretching ripple at the small end of stretching head 7 and form the incident wave of Hopkinson pull rod, this incident wave imports the incident bar 13 of Hopkinson pull rod into, when this incident wave reaches incident bar 13 with sample 14 surface of contact, because wave impedance is not mated, a part for this incident wave is reflected, reflection wave is formed in incident bar 13, another part is then transmitted in transmission bar 15 by sample 14, form transmitted wave.The shape of described reflection wave and transmitted wave and amplitude are determined by sample material character.
Incident wave and reflection wave signal are recorded by the foil gauge 16 be pasted onto on incident bar 13 by data acquisition unit 17, are recorded by the signal of transmitted wave by being pasted onto the foil gauge on transmission bar 15.The reflection wave utilizing data acquisition unit 17 to record and transmitted wave signal, obtain the dynamic tensile stress-strain diagram of material by a ripple method.
Claims (6)
1., based on a Hopkinson strut and tie stress wave generator for electromagnetic force, it is characterized in that, comprise power supply, capacitor charger and loading rifle; Described capacitor charger adopts the power pack of existing electromagnetic rivetter, and is connected with the electrode line loading rifle by the positive pole output line of the output of described capacitor charger, and negative pole output line connects with the negative line loading rifle; Load rifle and comprise stretching head, insulation course, loading rifle housing, main coil, secondary coil and compressing head; Stretching head is positioned at described loading rifle housing and is arranged on this loading rifle shell one end; Locating shaft on this stretching head is also positioned at and loads rifle housing and with to load rifle housing coaxial; Main coil, compressing head, two insulation courses and two secondary coils are all sleeved on the locating shaft on described stretching head, and compressing head is positioned at the loading rifle housing other end; Two insulation courses are fitted with the inside surface of described stretching head or compressing head respectively; Two secondary coils lay respectively at inside described each insulation course.
2. as claimed in claim 1 based on the Hopkinson strut and tie stress wave generator of electromagnetic force, it is characterized in that there is the via hole of two external connectors of main coil at the circumferential surface loading rifle housing the same side.
3. as claimed in claim 1 based on the Hopkinson strut and tie stress wave generator of electromagnetic force, it is characterized in that, the external peripheral surface of stretching head and the external peripheral surface of compressing head all coordinate with the internal surface gaps loading rifle housing.
4. as claimed in claim 1 based on the Hopkinson strut and tie stress wave generator of electromagnetic force, it is characterized in that, the circumferential surface of stretching head one end is made up of isometrical section and cone section; The axial length of described isometrical section: the axial length=1:1 of cone section; Isometrical section of described stretching head is stress wave receiver section, and the cone section of described stretching head is that stress wave amplifies reflection end; The largest diameter of stress wave receiver section, and the locating shaft axially protruded is had at the end face center of stress wave receiver section; The center that stress wave amplifies reflection end is plane, defines the minimum diameter of stretching head at this place; The diameter of described stretching head stress wave receiver section: stress wave amplifies the ratio=12:1 at the minimum diameter place of reflection end; The tapering that described stress wave amplifies the cone section of reflection end is 30 ゜.
5. as claimed in claim 1 based on the Hopkinson strut and tie stress wave generator of electromagnetic force, it is characterized in that, the circumferential surface of compressing head one end is made up of isometrical section and cone section; The axial length of described isometrical section: the axial length=1:1 of cone section; The end face of isometrical section is plane, is stress wave receiving end; The circumferential surface of cone section is that stress wave amplifies end; The coupling shaft axially protruded is had at the center of this cone section conical surface; Have in described coupling shaft termination for connecting into the internal thread penetrating bar; The tapering of the described cone section conical surface is 30 ゜; The maximum gauge of described compressing head: the ratio=12:1 of the minimum diameter at cone section conical surface place; The endoporus of compressing head coordinates with the locating shaft of stretching head, and clearance fit between the two.
6. use the experimental technique based on the Hopkinson strut and tie stress wave generator of electromagnetic force described in claim 1, the experimental technique of the described Hopkinson strut and tie stress wave generator based on electromagnetic force comprises Hopkinson compression experiment and Hopkinson stretching experiment; It is characterized in that, the experimentation of the described Hopkinson strut and tie stress wave generator based on electromagnetic force is:
Step 1. is arranged equipment:
Sequentially be arranged on coaxial according to a conventional method to loading rifle, incident bar and transmission bar on experiment table, and described incident bar and transmission bar are only moved freely at axis direction; Load the one end at the compressing head place of rifle near incident bar; A sample is arranged between incident bar and transmission bar, and make sample and incident bar and transmission bar coaxial;
Step 2. pastes foil gauge:
Conventional method is adopted to paste 2 foil gauges respectively at incident bar or transmission bar, and access data acquisition system that foil gauge is gone between; During described foil gauge of arranging lead-in wire, described each foil gauge lead-in wire must be distributed with the axis being parallel of incident bar or transmission bar, then draw perpendicular to axis direction bending at a right angle, make foil gauge lead-in wire linear state access data collector
Step 3. loading experiment and data acquisition: loading experiment comprises Hopkinson compression experiment and Hopkinson stretching experiment, wherein:
I when carrying out Hopkinson compression experiment, by the distance L between stretching head and main coil
1be adjusted to 30mm; The stress wave of compressing head is amplified end be connected with the incident bar of Hopkinson pressure bar; After capacitor charger charging, make capacitor charger to the main coil electric discharge loading rifle, electromagnetic repulsion force is produced between compressing head and main coil, described electromagnetic repulsion force shows as compression stress wave in compressing head inside and forms incident wave after being amplified by compressing head, this incident wave imports the incident bar of Hopkinson pressure bar into, when this incident wave reaches incident bar and sample contacts face, because wave impedance is not mated, a part for this incident wave is reflected, reflection wave is formed in incident bar, another part is then transmitted in transmission bar by sample, forms transmitted wave; The shape of described reflection wave and transmitted wave and amplitude are determined by sample material character;
Incident wave and reflection wave signal are recorded by the foil gauge be pasted onto on incident bar by data acquisition unit, are recorded by the signal of transmitted wave by being pasted onto the foil gauge on transmission bar; Utilize reflection wave and the transmitted wave signal of data acquisition unit record, obtained the dynamic compressing stress strain curve of test specimen by a ripple method;
II when carrying out Hopkinson stretching experiment, and the distance between adjustment stretching head and main coil, makes stretching head be adjacent to main coil, make the through hole of locating shaft through compressing head of stretching head, the locating shaft of stretching head is connected with the incident bar of Hopkinson pull rod by screw thread, the distance L of adjustment compressing head and main coil
2for 30mm, after capacitor charger charging, this capacitor charger is to the main coil electric discharge loading rifle, electromagnetic repulsion force is produced between stretching head and main coil, described electromagnetic repulsion force shows as compression stress wave in stretching head inside, described compression stress wave is exaggerated in stretching head, and be reflected into stretching ripple at the small end of stretching head and form the incident wave of Hopkinson pull rod, this incident wave imports the incident bar of Hopkinson pull rod into, when this incident wave reaches incident bar and sample contacts face, because wave impedance is not mated, a part for this incident wave is reflected, reflection wave is formed in incident bar, another part is then transmitted in transmission bar by sample, form transmitted wave, the shape of described reflection wave and transmitted wave and amplitude are determined by sample material character, incident wave and reflection wave signal are recorded by the foil gauge be pasted onto on incident bar by data acquisition unit, are recorded by the signal of transmitted wave by being pasted onto the foil gauge on transmission bar, utilize reflection wave and the transmitted wave signal of data acquisition unit record, obtained the dynamic tensile stress-strain diagram of material by a ripple method.
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