CN115901501A - Dynamic torsion-stretching/compressing synchronous combined loading device and loading method - Google Patents
Dynamic torsion-stretching/compressing synchronous combined loading device and loading method Download PDFInfo
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Abstract
A dynamic torsion-tension/compression synchronous combined loading device and a loading method are provided, wherein a time delay pulse generator is used for controlling torsion waves and tension/compression waves to simultaneously reach a sample, and finally torsion, tension/compression composite dynamic loading is realized. The energy is stored through the rotating torque loading mechanism, and the energy is obtained in real time through the strain rosettes adhered to the twisted incident rod. After the energy storage is finished, the clamping bolt of the clamping mechanism is rotated to enable the broken bolt to be broken in a tensile mode, so that the energy stored in the energy storage section of the torsion incident rod is transmitted to the direction of the sample in the form of stress waves, the strain waves positioned on the torsion incident rod can record the waveform of the torsion waves, and the torsion waves reach the sample to carry out dynamic torsion loading on the sample. The invention can control the torsional wave and the tensile wave to reach the sample simultaneously by accurately controlling the delay time, thereby realizing the dynamic tension-torsion composite loading of the sample. And the data acquisition unit simultaneously records stress wave pulse signals on the torsion incident rod and the stretching incident rod.
Description
Technical Field
The invention relates to the technical field of material impact dynamics experiments, in particular to a loading device and a loading method for testing mechanical properties of a material under the simultaneous action of dynamic torsion and dynamic tension/compression loads.
Background
Hopkinson bar(also known as Kolsky bars) are important devices for testing the mechanical properties of materials under dynamic loading conditions. The Hopkinson bar device is based on a one-dimensional elastic stress wave theory, and the test strain rate of the Hopkinson bar device is usually 100s -1 To 10000s -1 In between. Through development for many years, the Hopkinson bar device is mature and widely used for testing the mechanical properties of materials in states of dynamic compression, dynamic tension, dynamic torsion and the like.
The currently widely applied Hopkinson torsion bar loading mode is an energy storage type, which is firstly proposed by the term-rate effects in the development of torque plastic waves published in 1966 by W.E.Baker and C.H.Yew, and the design concept is that the length of an incident bar part is pre-twisted, elastic torsion potential energy is stored, then the energy is transmitted in the bar in the form of stress waves through the sudden release of a clamping device, and finally the loading of a bar end sample is realized. Compared with other loading modes (explosive type and pneumatic type), the energy storage type is safer and simpler, and the rising edge of the stress wave can be controlled within 20-40 microseconds. However, this has the disadvantage that the release time of the clamping device is not controlled, i.e. the generation time of the torsional stress wave cannot be precisely controlled.
In recent years, the applicant develops a series of researches on electromagnetic loading-based hopkinson rod experimental devices and methods, wherein a loading method of a single-shaft bidirectional electromagnetic hopkinson pressure rod and a pull rod is disclosed in the invention creation with the application number of 201810120975.6, the loading method utilizes an electromagnetic energy conversion technology to generate stress wave pulses, the generation of the pulses is realized by a discharge switch, and no time delay exists between the triggering of the switch and the generation of the stress pulses, so that the time accuracy of the pulses is easily controlled by a circuit. But the device has no way to achieve combined tension/compression and torsion loading.
The defects in the prior art mainly comprise the following two aspects:
on the one hand, a longer generation time of the torsional wave results in a too slow rising edge of the torsional wave
The invention with the application number of 201510106511.6 provides a dynamic tension/compression and torsion synchronous combined loading experimental device, wherein the generation of torsion waves in the device triggers the release of a hydraulic mechanism by a controller; the time required for this release process is on the order of hundreds of microseconds or even milliseconds. This leads to two problems: firstly, in the dynamic tension/compression and torsion synchronous combined loading experimental device, the tensile wave and the torsion wave are transmitted to the test piece from the same side, so that the synchronous loading of the two trains of waves on the test piece is realized, and a long distance is needed between the tensile transmitting tube and the torsion clamping device to offset the asynchronism between the two trains of waves. And the incident rod is too long, which is not beneficial to processing and can influence the propagation of stress wave. Secondly, due to uncertainty of mechanical motion time, the time for two rows of waves to reach the test piece is asynchronous, the consistency of the internal stress state of the test piece cannot be kept, and the test fails.
On the other hand, although the device in the invention creation of international application No. PCT/CN2020/113154 in the prior art can realize complex stress states such as dynamic impact loading of tension/compression and torsion combination, and accurately control the generation time of the torsional stress wave, the generation of the torsional stress wave involves an electromagnetic release device, the device is high in cost and complex in structure, and the rising edge of the generated torsional wave is relatively slow and long.
Disclosure of Invention
In order to improve the rising edge of a torsional stress wave, simplify a torsional-tensile/compressive combined loading experimental device and simultaneously ensure the synchronism of the torsional stress wave and the tensile/compressive stress wave reaching a sample, the invention provides a dynamic torsional-tensile/compressive synchronous combined loading device and a loading method.
The dynamic torsion-tension/compression synchronous combined loading device provided by the invention comprises a Hopkinson torsion bar loading unit, an electromagnetic Hopkinson tension/compression bar unit, a synchronous control unit and a mechanical test unit. Wherein: the Hopkinson torsion bar loading unit comprises a torsion incident bar, a clamping mechanism and a torque loading mechanism; one end of the torsion incident rod is fixed on the torque loading mechanism and is tightly connected with the torque loading mechanism, and the torsion incident rod is driven to rotate by the torque loading mechanism so as to apply torque. The clamping mechanism is sleeved on the torsion incident rod and clamps the torsion incident rod through the clamping head.
The fracture bolt is in threaded fit with the chuck, and the torsion incident rod is clamped by screwing the clamping bolt and the fracture bolt chuck, so that the torsion incident rod and the chuck do not slide relatively.
One end of a stretching incident rod in the electromagnetic Hopkinson pull/press rod unit is connected with the loading gun. The other end is a cantilever end, and the end surface of the cantilever end corresponds to the end surface of the torsional incident rod; the specimen is positioned between the tensile and torsional incident bars. Three groups of strain flowers are distributed on the outer circumferential surface of the incident rod, wherein the first group of strain flowers and the third group of strain flowers are respectively communicated with the data acquisition unit through data lines; the second group of strain rosettes are communicated with the signal input end of the delay pulse generator of the synchronous control unit through a data line.
The clamping mechanism comprises a clamping mechanism base and a chuck; the clamping head consists of two clamping plates and a fracture bolt, the two clamping plates are parallelly positioned in the clamping mechanism base, and clamping grooves respectively positioned on the inner side surfaces of the two clamping plates correspond to each other; the fracture bolt is arranged at the upper ends of the two clamping plates, and the gap in the middle of the fracture bolt is positioned between the two clamping plates of the clamping mechanism; the clamping bolts are positioned on the two support plates of the clamping mechanism base.
The length of the clamping mechanism and the sample end is 1.5m, and the temperature rise length of the tensile incident rod is 1.5m.
The time precision of the time delay pulse generator is 10ns.
Two tensile strain gauges are symmetrically adhered to the circumference of the position 1/2 of the length of the tensile incident rod; the tensile strain gage is connected to a wheatstone bridge in the data acquisition system.
In the three groups of strain rosettes, each strain rosette consists of two strain gauges which are perpendicular to each other, the angular bisector of the two strain gauges is parallel to the central axis of the incident rod during pasting, and the strain rosettes are respectively pasted in the middle between the torque loading mechanism and the clamping mechanism, at the position of the clamping mechanism, which is 10cm away from the clamping mechanism in the direction of the sample, and in the middle between the clamping mechanism and the sample.
The invention also provides a method for loading by using the dynamic torsion-stretching/compressing synchronous combined loading device, which comprises the following specific processes:
the electromagnetic Hopkinson stretching and loading device, the stretching incident rod, the clamping mechanism, the torque loading mechanism and the torsion incident rod are sequentially arranged on the experiment table. Assembling the torque loading mechanism and the torsion incident rod to enable the torque loading mechanism and the torsion incident rod to be tightly matched, and enabling the torsion rod to freely rotate on the clamping mechanism and the positioning cylinder; the loading gun is assembled with a tensile entrance bar.
The specific method for assembling the loading gun and the stretching incident rod comprises the following steps: one end of the stretching incident rod with external threads sequentially penetrates through the positioning barrel on the experiment table, the central hole of the loading gun and the through hole of the amplifier, and the stretching incident rod is freely matched with the central hole of the loading gun, the through hole of the amplifier and the through hole of the positioning barrel, so that the two incident rods can freely slide before being connected with other devices, and the axes of the two incident rods are on the same horizontal line. The amplifier is penetrated out from one end of the stretching incident rod with external threads, the amplifier is connected with the boss through threads, the loading gun, the amplifier and the boss are tightly attached, and the height of the positioning barrel is adjusted, so that the stretching incident rod, the twisting incident rod and the loading device are positioned on the same horizontal line.
the tensile strain gauge is adhered to the tensile incident rod; when in pasting, two same tensile strain gauges are symmetrically pasted on the circumferential surface at the position of 1/2 of the length of the tensile incident rod; and welding a strain gauge lead on a pin of the tensile strain gauge, and connecting the strain gauge lead into a Wheatstone bridge in a data acquisition system.
Pasting strain flowers on the torsion incident rod; the strain rosette has three groups, each strain rosette consists of two strain gauges which are perpendicular to each other, and when the strain rosette is pasted, the angular bisector of the two strain gauges is parallel to the central axis of the incident rod, and the strain rosettes are respectively pasted in the middle between the torque loading mechanism and the clamping mechanism, between the clamping mechanism and the sample and 10cm away from the clamping mechanism, and in the middle between the clamping mechanism and the sample. And when the strain flowers are pasted, the three groups of strain flowers are respectively connected into a Wheatstone bridge in the delay pulse generator and the data acquisition system.
Step 3, loading and collecting data:
and fixing the sample between the torsion bar incident rod and the stretching incident rod, and fixing two ends of the sample with the torsion bar incident rod and the stretching incident rod respectively through threads. The loading gun was mounted on a laboratory bench.
Installing a broken bolt; rotating a clamping bolt at the bottom of the clamping mechanism to clamp the torsion incident rod by the clamping mechanism, applying torque to the torsion incident rod through a rotation torque loading mechanism, and obtaining the applied torque through strain rosettes; stopping when the voltage signal of the data acquisition system is 30 millivolts
The torsion incident rod is a torsion incident rod energy storage section between the torque loading mechanism and the clamping mechanism. The torsion loading mechanism is rotated to drive the torsion incident rod to rotate, and the torsion incident rod is twisted to generate torsion deformation because the clamping mechanism clamps the torsion incident rod, so that the torsion energy can be stored in the torsion incident rod energy storage section.
And charging a capacitor of the electromagnetic Hopkinson tension loading device. The charging voltage is 800v, and the amplitude of the generated tensile stress wave is 200MPa; the capacitance of the capacitor is 2mf and the pulse width of the generated tensile stress wave is 300 microseconds.
After charging is finished, the pulse delay generator is set to be in a state to be triggered, and the bolt below the clamping mechanism is continuously screwed until the broken bolt is continuously pulled to break, so that torque stored by the torsion incident rod can be instantly released, torsion waves with steep rising edges are generated, and the torsion waves are transmitted to the direction of the sample on the torsion rod.
When the torsional wave reaches the strain rosette position, the torsional strain gauge is deformed, the delay pulse generator is triggered, after the delay pulse generator is subjected to set delay time, the electromagnetic gun of the electromagnetic pull rod is then triggered to discharge, tensile wave which is transmitted to the sample is generated at the end of the pull rod, and the tensile wave and the torsional wave on the torsional incident rod simultaneously reach the sample for loading. The delay time is 180ms and the delay time is,
and completing the loading of the dynamic torsion-stretching/compressing synchronous combined loading device.
The invention adopts a method that a torsional wave signal triggers an electromagnetic Hopkinson tension/compression bar to work so as to generate tensile/compression waves, controls the torsional waves and the tensile/compression waves to reach a sample simultaneously through a time delay pulse generator, and finally realizes the composite dynamic loading of torsion, tension/compression. Compared with the prior art, the invention has the following characteristics:
1. the Hopkinson torsion bar is essentially an energy storage type Hopkinson torsion bar without a transmission rod, a broken bolt is firstly installed during testing, and a torsion incident rod is clamped by a clamping mechanism at a certain distance from a torque loading mechanism; and then, the torque loading mechanism is rotated to store energy, and the energy can be obtained in real time through the strain rosettes stuck on the torsion incident rod. After energy storage is finished, the clamping bolt below the clamping mechanism is rotated to enable the broken bolt to be pulled until the broken bolt is broken at the grooving position, the energy stored in the energy storage section is transmitted to the direction of the sample in the form of stress waves, the strain flowers located on the torsion incident rod can record the waveform of the torsion waves, and the torsion waves reach the sample to carry out dynamic torsion loading on the sample.
2. The electromagnetic Hopkinson tension/compression bar unit is in the prior art, and the electromagnetic Hopkinson tension/compression loading device used in the invention adopts a loading device provided in the invention patent with the application number of 201510956545.4. The amplitude and pulse width of the generated stress wave can be accurately controlled by the charging voltage value and the capacitance value in the circuit.
3. The synchronous control part is mainly realized by a time delay pulse generator, the working principle of the instrument is that after voltage information of a strain gauge on a torsion incident rod is received, the signal is output to a discharge switch of an electromagnetic Hopkinson tension/compression loading device after time delay of a certain time, tension/compression stress waves are generated, and the tension/compression waves and the torsion waves can be controlled to reach a sample simultaneously by accurate setting of the time delay.
The invention aims to solve a key technical problem by triggering the electromagnetic Hopkinson tension/compression bar discharge by using a torsional wave signal to realize synchronous loading. In order to realize that the torsional wave and the tensile/compressive wave simultaneously reach the sample for loading, the prerequisite condition is to satisfy a time condition relation, namely the time for the torsional wave signal to reach the sample from the trigger position is longer than the sum of the time for the electromagnetic Hopkinson tensile/compressive loading device to generate the tensile/compressive wave and the time for the tensile/compressive wave to propagate on the tensile/compressive incident rod, namely the relation is satisfied:
wherein L is n Is the distance from the strain rosette connected with the time-delay pulse generator on the torsion incident rod to the sample, L l Is the total length of the electromagnetic pull/press injection rod, T is the working time of the electromagnetic Hopkinson pull/compression loading device, and the working time comprises the time of the processes of closing a discharge switch, discharging and the like, C n And C l The wave velocities at which the torsional and tensile/compressive waves, respectively, propagated in the rod, were tested, typically by optimizing the circuit and varying the rod length so that the left side of the equation was larger than the right side. The loading is done by setting the delay time t of the delay pulse generator so that the right side of the equation plus t equals the left side of the equation, so that the torsional wave and the tension/compression wave arrive at the sample just at the same time.
4. The mechanical testing part, in particular the measurement of strain, is also distinguished by the different propagation patterns of stress waves on the torsion incident rod and the tension/compression incident rod. The strain measurement on the torsional incident rod adopts strain gauge measurement, namely two groups of torsional strain gauges which are perpendicular to each other and form an angle of 45 degrees with the axial direction of the rod. The strain measurement on the tensile/compressive incident rod adopts a pair of strain gauges, and the strain grids of the strain gauges are parallel to the axis.
5. The key of the sample design part is to solve the connection problem between the sample and the loading rod under the combined action of tension/compression and torsion. At present, a thin-wall cylindrical dynamic torsion sample is mostly connected with a torsion rod in an adhesive mode, and the design can be used during dynamic torsion-compression loading; but because the tensile strength of the adhesive connection is low, degumming can occur during the test to cause the failure of the test, so the connection mode of the dynamic tensile sample and the rod mainly adopts the threaded connection and the clamp connection. By combining the characteristics of the two loading modes, the invention designs a thin-wall sample for dynamic tension-torsion combined loading, and the thin-wall sample is connected with the torsion incident rod and the stretching incident rod in a threaded connection mode.
The threaded connection is specifically as follows: when the sample is processed, the surface of the part connected with the rod is processed with external threads, and the outer diameter of the external threads is smaller than the diameter of the rod. And when the rod end is machined, machining internal threads inside the grooves. The sample clamping is to screw the sample into the middle of the two rods. It should be noted that after the sample is installed, the rotation direction of the torsion incidence rod during operation should be the sample tightening direction, otherwise, the torsion cannot be applied, and the opposite rotation directions of the threads on the two sides of the sample gauge length section are required.
Fig. 3 shows signals of the stretching pulse and the twisting pulse collected by the data collector in the experiment, the trapezoidal wave is the twisting incident wave, and the sine wave is the stretching incident wave, so that the rising edges of the two rows of waves are overlapped, the loading synchronism is ensured, and the twisting incident wave has a steep rising edge.
Drawings
FIG. 1 is a schematic diagram of the structure of the apparatus of the present invention.
FIG. 2 is a schematic structural view of a torsion specimen; wherein fig. 2base:Sub>A isbase:Sub>A front view and fig. 2b isbase:Sub>A view from directionbase:Sub>A-base:Sub>A of fig. 2base:Sub>A.
Fig. 3 is a pulse signal collected by the data collector.
FIG. 4 is a schematic view of the clamping mechanism; wherein fig. 4a is a front view and fig. 4b is a right side view of fig. 4 a.
In the figure: 1. twisting the incident rod; 2. breaking the bolt; 3. a clamping mechanism; 4. clamping the bolt; 5. straining flowers; 6. a data acquisition unit; 7. sampling; 8. a delay pulse generator; 9. stretching the strain gauge; 10. stretching the incident rod; 11. loading a gun; 12. stretching the boss of the incident rod; 13. a torque loading mechanism; 14. a chuck; 15. a fixture base.
Detailed Description
The embodiment is a torsion-tension/compression synchronous combined loading device based on a Hopkinson bar experiment technology, and the torsion-tension/compression synchronous combined loading device comprises a Hopkinson torsion bar loading unit, an electromagnetic Hopkinson tension/compression bar unit, a synchronous control unit and a mechanical test unit. Wherein:
the Hopkinson torsion bar loading unit comprises a torsion incident bar 1, a clamping mechanism 3 and a torque loading mechanism 13;
the torque loading mechanism adopts the prior art, the torque loading mechanism is a speed reducer, and the model of the speed reducer adopted in the embodiment is WPSEDKS100-1/20-A. The proximal end of the torsion incident rod 1 is fixed to a torque loading mechanism, and the torsion incident rod and the torque loading mechanism are tightly connected, and the torsion incident rod is driven to rotate by the torque loading mechanism so as to apply torque.
The clamping mechanism 3 is sleeved on the torsion incident rod 1, and the torsion incident rod 1 is clamped by the clamping head 14.
The fracture bolt 2 is arranged on two clamping plates of the clamping head 14, and the torsional incident rod 1 is clamped by screwing the clamping bolt 4 and the fracture bolt 2 and the clamping head 14, so that the torsional incident rod 1 and the clamping head 14 do not slide relatively.
The electromagnetic Hopkinson pull/pressure bar unit is the prior art, and the technical scheme is disclosed in the invention patent ZL 201510956545.4; the electromagnetic Hopkinson tension loading device disclosed in the patent of the invention comprises a tension incident rod 10 and an electromagnetic Hopkinson tension loading device.
The electromagnetic Hopkinson tension loading device is composed of a power supply, a capacitor, a discharge switch, a loading gun shell, a main coil, a positioning cylinder, a secondary coil and an insulating layer. The generation process of the stretching wave is as follows: the power supply charges the capacitor first, and enters a state to be triggered after being fully charged. And tightening a clamping bolt of the clamping mechanism to enable the broken bolt to be continuously pulled until the broken bolt is broken, generating a torsional wave and transmitting the torsional wave to the direction of the sample, generating deformation of the strain when the torsional stress wave is transmitted to a strain position in the rod, converting a strain signal into a voltage signal and transmitting the voltage signal into the delay pulse generator, triggering the electromagnetic tension loading device after the delay pulse generator passes through the set delay time, closing the discharge switch, and discharging the capacitor at the moment. At the moment when the discharge switch is closed, a strong magnetic field is generated around the coil through rapidly changing impact current in the main coil, a secondary coil coupled with the main coil generates induced current under the action of the strong magnetic field, then an eddy magnetic field is generated, eddy repulsion force is generated by interaction of the two magnetic fields and can be transmitted to the boss through the amplifier, compression wave generated by the boss is transmitted to the right end of the boss and then is converted into tensile wave through reflection, and the tensile wave is transmitted to the sample direction to carry out tensile loading.
The torsion incident rod and the electromagnetic stretching incident rod are made of aluminum alloy with the diameter of 25mm, the length from the clamping mechanism to the sample end is 1.5m, and the length of the stretching incident rod is 1.5m.
The synchronization control unit comprises a delay pulse generator 8. The model of the delay generator is DG645 digital delay generator, the time precision is 10ns, and the experimental requirement of the invention is met. The signal input end of the delay generator is connected with the strain gauge, and the signal output end of the delay generator is connected with a discharge switch of the tension wave loading gun. The tension-torsion loading device has the function of accurately controlling the time of the tension wave loading gun for generating the tension wave, so that the torsion wave and the tension wave can simultaneously reach the sample, and the tension-torsion loading of the sample is completed, so that the dynamic mechanical property of the material of the sample in a complex stress state is obtained.
The mechanical testing unit comprises a strain gage 5, a tensile strain gage 9 and a data acquisition unit 6. The strain gage 5, the tensile strain gage 9 and the data collector 6 all adopt the prior art. And taking the axis of the stretching incident rod as a symmetry axis on the circumference of the half length of the stretching incident rod, symmetrically sticking two identical stretching strain gauges to the surface of the stretching incident rod, welding a lead wire of the strain gauge on a pin of the strain gauge, and connecting the lead wire of the strain gauge into a Wheatstone bridge in a data acquisition system. And connecting the strain rosette into a Wheatstone bridge in the data acquisition system according to the operation. The strain rosette comprises three groups of strain rosettes, each strain rosette comprises two strain gauges which are perpendicular to each other, the angular bisector of the two strain gauges is parallel to the central axis of the incident rod when the strain rosettes are pasted in the middle between the torque loading mechanism and the clamping mechanism, the position, with the distance being 10cm, of the clamping mechanism from the clamping mechanism to the sample direction, and the middle between the clamping mechanism and the sample.
The embodiment further provides a method for loading by using the dynamic torsion-tension/compression synchronous combined loading device, which specifically comprises the following steps:
the electromagnetic Hopkinson stretching and loading device, the stretching incident rod, the clamping mechanism, the torque loading mechanism and the torsion incident rod are sequentially arranged on the experiment table. And assembling the torque loading mechanism and the torsion incident rod to enable the torque loading mechanism and the torsion incident rod to be tightly matched and enable the torsion rod to freely rotate on the clamping mechanism and the positioning cylinder.
Assembling a loading gun and a stretching incident rod, wherein the specific method comprises the following steps: one end of the stretching incident rod with external threads sequentially penetrates through the positioning barrel on the experiment table, the central hole of the loading gun and the through hole of the amplifier, and the stretching incident rod is freely matched with the central hole of the loading gun, the through hole of the amplifier and the through hole of the positioning barrel, so that the two incident rods can freely slide before being connected with other devices, and the axes of the two incident rods are on the same horizontal line. The amplifier is penetrated out from one end of the stretching incident rod with external threads, the amplifier is connected with the boss through threads, the loading gun, the amplifier and the boss are tightly attached, and the height of the positioning barrel is adjusted, so that the stretching incident rod, the twisting incident rod and the loading device are positioned on the same horizontal line.
in this embodiment, strain information of the twisted incident rod is measured by the strain gauge, and strain information of the stretched incident rod is measured by the tensile strain gauge having a specification of 1000 Ω.
When the incident rod is stretched and the tensile strain gauge is pasted, symmetrically pasting two identical tensile strain gauges on the circumferential surface at the position of 1/2 of the length of the incident rod; and welding a strain gauge lead on a pin of the tensile strain gauge, and connecting the strain gauge lead into a Wheatstone bridge in a data acquisition system.
In the three groups of strain rosettes, each strain rosette consists of two strain gauges which are perpendicular to each other, and when the strain rosettes are pasted, the angular bisector of the two strain gauges is parallel to the central axis of the incident rod, and the strain rosettes are respectively pasted in the middle between the torque loading mechanism and the clamping mechanism, between the clamping mechanism and the sample and 10cm away from the clamping mechanism, and in the middle between the clamping mechanism and the sample.
Step 3, loading and collecting data:
fix the sample between torsion bar incident rod and the tensile incident rod to make the both ends of this sample pass through the thread tightening with this torsion bar incident rod and tensile incident rod respectively, make the relative two poles of sample no motion, install the loading rifle on the laboratory bench.
Screwing the broken bolt into the clamping mechanism from the upper part of the clamping mechanism, so that a gap of the broken bolt falls between two chucks of the clamping mechanism; and rotating a clamping bolt at the bottom of the clamping mechanism to clamp and twist the incident rod by the clamping mechanism. The rotating torque loading mechanism applies torque to the torsion incident rod, and the torque is measured through strain patterns on the energy storage section of the torsion incident rod. The part of the torsion incident rod between the torque loading mechanism and the clamping mechanism is the torsion incident rod energy storage section. The torsion incident rod is driven to rotate by rotating the torque loading mechanism, and the torsion incident rod is twisted and deformed because the clamping mechanism clamps the torsion incident rod, so that the torque can be stored in the torsion incident rod between the clamping mechanism and the torque loading mechanism, namely the torsion incident rod is a torsion incident rod energy storage section between the torque loading mechanism and the clamping mechanism.
And charging a capacitor of the electromagnetic Hopkinson tension loading device. The charging voltage is 800v, and the amplitude of the generated tensile stress wave is 200MPa; the capacitance of the capacitor is 2mf and the pulse width of the generated tensile stress wave is 300 microseconds.
After charging is finished, the pulse delay generator is set to be in a state to be triggered, and the clamping bolt below the clamping mechanism is continuously screwed, so that the broken bolt is continuously pulled until being broken.
After the broken bolt is broken, the chuck can not continuously clamp the torsion incident rod, so that the torque stored by the torsion incident rod can be released instantly, and a torsion wave with a steep rising edge is generated and is transmitted to the sample direction on the torsion rod. When the torsional wave reaches the strain rosette position, the torsional strain gauge is deformed, the delay pulse generator is triggered, after the delay pulse generator is subjected to set delay time, the electromagnetic gun of the electromagnetic pull rod is then triggered to discharge, tensile wave which is transmitted to the sample is generated at the end of the pull rod, and the tensile wave and the torsional wave on the torsional incident rod simultaneously reach the sample for loading. The delay time set in this embodiment is 180ms,
in the embodiment, the torsional wave and the tensile wave can be controlled to simultaneously reach the sample by accurately controlling the delay time, so that the dynamic tension-torsion composite loading of the sample is realized. The data acquisition unit records the stress wave pulse signals on the torsion incident rod and the tension incident rod simultaneously, as shown in fig. 3.
Claims (10)
1. A dynamic torsion-stretching/compressing synchronous combined loading device is characterized by comprising a Hopkinson torsion bar loading unit, an electromagnetic Hopkinson tension/compression bar unit, a synchronous control unit and a mechanical test unit; wherein: the Hopkinson torsion bar loading unit comprises a torsion incident rod, a clamping mechanism and a torque loading mechanism; one end of the torsion incident rod is fixed on the torque loading mechanism and is tightly connected with the torsion incident rod, and the torsion incident rod is driven to rotate by the torque loading mechanism so as to apply torque; the clamping mechanism is sleeved on the torsion incident rod and clamps the torsion incident rod through a chuck;
the broken bolt is arranged on the two clamping plates of the clamping head, and the torsional incident rod is clamped by screwing the clamping bolt and the broken bolt clamping head, so that the torsional incident rod and the clamping head do not slide relatively;
one end of a tensile incident rod in the electromagnetic Hopkinson pull/press rod unit is connected with the loading gun; the other end is a cantilever end, and the end surface of the cantilever end corresponds to the end surface of the torsional incident rod; the sample is positioned between the tensile incident rod and the torsional incident rod; three groups of strain flowers are distributed on the outer circumferential surface of the incident rod, wherein the first group of strain flowers and the third group of strain flowers are respectively communicated with a data acquisition unit through data lines; the second group of strain rosettes are communicated with the signal input end of the delay pulse generator of the synchronous control unit through a data line.
2. The dynamic torsion-tension/compression synchronous combined loading device according to claim 1, wherein the clamping mechanism comprises a clamping mechanism base and a chuck; the clamping head consists of two clamping plates and a fracture bolt, the two clamping plates are parallelly positioned in the clamping mechanism base, and clamping grooves respectively positioned on the inner side surfaces of the two clamping plates correspond to each other; the fracture bolt is arranged at the upper ends of the two clamping plates, and the gap in the middle of the fracture bolt is positioned between the two clamping plates of the clamping mechanism; the clamping bolts are positioned on the two support plates of the clamping mechanism base.
3. The dynamic torsion-tension/compression synchronous combined loading device according to claim 1, wherein the distance between the clamping mechanism and the sample end is 1.5m; the length of the stretching incident rod is 1.5m.
4. The dynamic torsion-stretching/compressing synchronous combined loading device according to claim 1, wherein the time precision of the time delay pulse generator is 10ns.
5. A method for loading by using the dynamic torsion-tension/compression synchronous combined loading device as claimed in claim 1, which is characterized in that the specific process comprises the following steps:
step 1, arranging equipment:
sequentially installing an electromagnetic Hopkinson tension loading device, a tension incident rod, a clamping mechanism, a torque loading mechanism and a torsion incident rod on an experiment table; assembling the torque loading mechanism and the torsion incident rod to enable the torque loading mechanism and the torsion incident rod to be tightly matched, and enabling the torsion rod to freely rotate on the clamping mechanism and the positioning cylinder; assembling a loading gun and a stretching incident rod;
step 2, pasting a strain gauge:
the pasting strain gauge includes:
sticking a tensile strain gauge on a tensile incident rod; when in pasting, two tensile strain gauges are symmetrically pasted on the circumferential surface at the position of 1/2 of the length of the tensile incident rod; the tensile strain gauge is connected into a Wheatstone bridge in a data acquisition system;
pasting strain flowers on the torsion incident rod; when pasting, the three groups of strain rosettes are respectively connected into a delay pulse generator and a Wheatstone bridge in a data acquisition system;
step 3, loading and collecting data:
fixing a sample between the torsion bar incident rod and the stretching incident rod, and fixing two ends of the sample with the torsion bar incident rod and the stretching incident rod respectively through threads; mounting a loading gun on a laboratory bench;
installing a broken bolt; rotating a clamping bolt at the bottom of the clamping mechanism to clamp the torsion incident rod by the clamping mechanism, applying torque to the torsion incident rod through a rotation torque loading mechanism, and obtaining the applied torque through strain rosettes; stopping when the voltage signal of the data acquisition system is 30 millivolts
The torsion incident rod is a torsion incident rod energy storage section between the torque loading mechanism and the clamping mechanism; the torsion loading mechanism is rotated to drive the torsion incident rod to rotate, and the torsion incident rod generates torsion deformation because the clamping mechanism clamps the torsion incident rod, so that the torsion incident rod can be stored in the torsion incident rod energy storage section;
charging a capacitor of the electromagnetic Hopkinson tension loading device; the charging voltage is 800v, and the amplitude of the generated tensile stress wave is 200MPa; the capacitance of the capacitor is 2mf, and the pulse width of the generated tensile stress wave is 300 microseconds; after charging is finished, setting a pulse delay generator to be in a state to be triggered, and continuously screwing a bolt below a clamping mechanism until the broken bolt is continuously broken in a tensile mode, so that torque stored by a torsion incident rod can be released instantly, torsion waves with steep rising edges are generated, and the torsion waves are transmitted to the direction of a sample on the torsion rod;
when the torsional wave reaches the strain rosette position, the torsional strain gauge is deformed, the delay pulse generator is triggered, after the delay pulse generator is subjected to set delay time, an electromagnetic gun of the electromagnetic pull rod is then triggered to discharge, a tensile wave which is transmitted to the sample is generated at the end of the pull rod, and the tensile wave and the torsional wave on the torsional incident rod reach the sample to be loaded at the same time; the delay time is 180ms and the delay time is,
and completing the loading of the dynamic torsion-stretching/compressing synchronous combined loading device.
6. The method for loading according to claim 5, wherein the method for assembling the loading gun with the tensile input rod comprises the following steps: one end of the stretching incident rod with external threads sequentially penetrates through the positioning barrel on the experiment table, the central hole of the loading gun and the through hole of the amplifier, and the stretching incident rod is freely matched with the central hole of the loading gun, the through hole of the amplifier and the through hole of the positioning barrel, so that the two incident rods can freely slide before being connected with other devices, and the axes of the two incident rods are on the same horizontal line; the amplifier is penetrated out of one end of the stretching incidence rod with external threads, the end of the stretching incidence rod with the external threads is connected with the boss through threads, the loading gun, the amplifier and the boss are tightly attached, and the height of the positioning cylinder is adjusted, so that the stretching incidence rod, the twisting incidence rod and the loading device are positioned on the same horizontal line.
7. The method of loading according to claim 5, wherein the strain rosettes have three sets, each strain rosettes consisting of two mutually perpendicular torsional strain gages; when the torsion strain gauge is pasted, the angular bisector of the two torsion strain gauges is parallel to the central axis of the incident rod.
8. The dynamic torsion-tension/compression synchronous combined loading device according to claim 1, wherein the three groups of strain patterns are respectively adhered to the middle between the torque loading mechanism and the clamping mechanism, the position of the clamping mechanism, which is 10cm away from the clamping mechanism towards the sample, and the middle between the clamping mechanism and the sample.
9. The dynamic torsion-stretching/compressing synchronous combined loading device according to claim 1, wherein two pieces of the tensile strain gauge are symmetrically adhered to the circumference of the tensile input rod at 1/2 of the length thereof.
10. The dynamic torsion-tension/compression synchronous combined loading device according to claim 1, wherein each strain rosette in the three groups of strain rosettes is composed of two strain gauges which are perpendicular to each other, and when the strain rosettes are pasted, the angle bisector of the two strain gauges is parallel to the central axis of the incident rod, and the strain rosettes are respectively pasted in the middle between the torque loading mechanism and the clamping mechanism, between the clamping mechanism and the sample and 10cm away from the clamping mechanism, and in the middle between the clamping mechanism and the sample.
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| CN116609168A (en) * | 2023-05-18 | 2023-08-18 | 天津大学 | Composite loading device based on Hopkinson bar |
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| CN116609168A (en) * | 2023-05-18 | 2023-08-18 | 天津大学 | Composite loading device based on Hopkinson bar |
| CN116625848A (en) * | 2023-05-18 | 2023-08-22 | 天津大学 | Composite loading device |
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