A dynamic torsion-tension / compression synchronous combined loading device and loading method

Abstract

A dynamic torsion-tension / compression synchronous combined loading device and loading method, through a delay pulse generator, a torsional wave and a tensile / compressive wave are simultaneously arrived at a sample, and finally a torsion, a tensile / compressive composite dynamic loading is realized. In the application, energy is stored through a rotating torque loading mechanism, and the size of the energy is obtained in real time through a strain flower pasted on a torsional incident rod. After the energy storage is completed, the clamping bolt of the rotating clamping mechanism is clamped to make the broken bolt be broken under tension, so that the energy stored in the energy storage section of the torsional incident rod is transmitted to the sample in the form of a stress wave, the strain flower located on the torsional incident rod can record the waveform of the torsional wave, and the sample is dynamically torsionally loaded when the torsional wave reaches the sample. Through accurate control of the delay time, the torsional wave and the tensile wave can be simultaneously arrived at the sample, and the dynamic tensile-torsion composite loading of the sample is realized. A data collector simultaneously records the stress wave pulse signals on the torsional incident rod and the tensile incident rod.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material impact dynamics experiment, in particular to a loading device and a loading method for testing mechanical properties of materials under the action of dynamic torsion and dynamic tension / compression. BACKGROUND

[0002] Hopkinson bar (also known as Kolsky bar) is an important device for testing the mechanical properties of materials under dynamic loading conditions. Hopkinson bar device is based on one-dimensional elastic stress wave theory, and the test strain rate is usually between 100 s -1 to 10000 s -1 After years of development, Hopkinson bar device has become mature and is widely used to test the mechanical properties of materials under dynamic compression, dynamic tension, dynamic torsion and other conditions.

[0003] The most widely used Hopkinson torsion bar loading method is energy storage type, which was first proposed by W.E.Baker and C.H.Yew in 1966 in the article Strain-rate effects in the propagation of torsion plastic waves. The design idea is to pre-torsion the incident bar part for a certain length to store elastic torsion potential energy, and then release the energy in the form of stress wave in the bar through the sudden release of the clamping device, and finally realize the loading of the bar end sample. Compared with other loading methods (explosive type, pneumatic type), the energy storage type is safer and simpler, and can control the rising edge of the stress wave within 20-40 microseconds. However, the disadvantage is that the release time of the clamping device is not controllable, i.e. the generation time of the torsional stress wave cannot be accurately controlled.

[0004] In recent years, the applicant has carried out a series of researches on Hopkinson bar experimental devices and methods based on electromagnetic loading. In the invention with application number 201810120975.6, a uniaxial bidirectional electromagnetic Hopkinson compression bar and tension bar loading method is disclosed. This loading method uses electromagnetic energy conversion technology to generate stress wave pulses, and the generation of pulses relies on discharge switches. There is no time delay between switch triggering and stress pulse generation, so the time accuracy of the pulse can be easily controlled by the circuit. However, this device cannot realize the combined loading of tension / compression and torsion.

[0005] The deficiencies existing in the prior art mainly include the following two aspects:

[0006] On the one hand, the long generation time of torsional wave leads to too slow and long rising edge of the torsional wave

[0007] A dynamic tension / compression and torsion synchronous combined loading experimental device is proposed in the invention with application number 201510106511.6. The generation of torsional waves in this device relies on the release of hydraulic mechanisms triggered by the controller. The time required for this release process is in the order of hundreds of microseconds or even milliseconds. This will cause two problems: first, in the dynamic tension / compression and torsion synchronous combined loading experimental device, the tensile wave and the torsional wave are transmitted to the test piece from the same side. To achieve the synchronous loading of the two wave columns on the test piece, a long distance is needed between the tensile launching tube and the torsional clamping device to offset the asynchronization between the two wave columns. The overlong incident rod is not conducive to processing and will also affect the propagation of stress waves. Second, due to the uncertainty of mechanical movement time, the two wave columns cannot arrive at the test piece synchronously, which cannot maintain the consistency of the stress state in the test piece, resulting in test failure.

[0008] On the other hand, the device in the invention with international application number PCT / CN2020 / 113154 of the prior art can realize dynamic impact loading of complex stress states such as tension / compression and torsion combination, and accurately control the generation time of torsional stress waves. However, the generation of torsional stress waves involves electromagnetic release devices, which are expensive and complex in structure, and the rising edge of the generated torsional wave is slow and long. SUMMARY

[0009] In order to improve the rising edge of the torsional stress wave, simplify the torsional-tension / compression combined loading experimental device and ensure the synchronization of the torsional stress wave and the tension / compression stress wave to the test sample, the present invention proposes a dynamic torsional-tension / compression synchronous combined loading device and loading method.

[0010] The dynamic torsional-tension / compression synchronous combined loading device proposed by the present invention comprises a Hopkinson torsion rod loading unit, an electromagnetic Hopkinson tension / compression rod unit, a synchronous control unit and a mechanical test unit. Among them: the Hopkinson torsion rod loading unit comprises a torsional incident rod, a clamping mechanism and a torque loading mechanism; one end of the torsional incident rod is fixed on the torque loading mechanism and they are closely connected, and the torque loading mechanism drives the torsional incident rod to rotate to apply torque. The clamping mechanism is sleeved on the torsional incident rod, and the torsional incident rod is clamped by the chuck.

[0011] The broken bolt and the chuck are matched by threads, and the torsional incident rod is clamped by tightening the clamping bolt and the broken bolt chuck, so that the torsional incident rod and the chuck do not slide relative to each other.

[0012] One end of the tensile incident rod in the electromagnetic Hopkinson tensile / compressive rod unit is connected with the loading gun, and the other end is a cantilever end, the end face of which corresponds to the end face of the torsional incident rod; the sample is located 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 the data collector through data lines; the second group of strain flowers is communicated with the signal input end of the delay pulse generator of the synchronous control unit through a data line.

[0013] The clamping mechanism comprises a clamping mechanism base and a chuck; the chuck is composed of two clamping plates and a fracture bolt, the two clamping plates are located in the clamping mechanism base in parallel, and the clamping grooves respectively located on the inner surfaces of the two clamping plates correspond to each other; the fracture bolt is installed at the upper ends of the two clamping plates, and the notch in the middle of the fracture bolt is located in the middle of the two clamping plates of the clamping mechanism; the clamping bolt is located on the two supporting plates of the clamping mechanism base.

[0014] The length of the clamping mechanism and the sample end is 1.5 m, and the length of the tensile incident rod for heating is 1.5 m.

[0015] The time accuracy of the delay pulse generator is 10 ns.

[0016] Two tensile strain gauges are symmetrically pasted at 1 / 2 of the length of the tensile incident rod; the tensile strain gauges are connected to the Wheatstone bridge in the data acquisition system.

[0017] Each strain gauge in the three groups of strain gauges is composed of two perpendicular strain gauges, the angle bisector of the two strain gauges is parallel to the central axis of the incident rod when pasted, and is respectively pasted in the middle between the torque loading mechanism and the clamping mechanism, 10 cm away from the clamping mechanism in the direction of the clamping mechanism to the sample, and the middle between the clamping mechanism and the sample.

[0018] The application also provides a loading method using the dynamic torsion-tensile / compressive synchronous combined loading device, and the specific process is as follows:

[0019] Step 1, arrange the equipment:

[0020] The electromagnetic Hopkinson tensile loading device, the tensile incident rod, the clamping mechanism, the torque loading mechanism and the torsional incident rod are sequentially installed on the experiment table. The torque loading mechanism and the torsional incident rod are assembled to tightly fit each other, and the torsional rod is freely rotated on the clamping mechanism and the positioning cylinder; the loading gun and the tensile incident rod are assembled.

[0021] The specific method of assembling the loading gun with the stretching incident rod is as follows: the stretching incident rod with external thread is sequentially inserted through the positioning cylinder on the experimental 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 cylinder, so that the two incident rods can freely slide before being connected with other devices and the shafts are on the same horizontal line. The stretching incident rod with external thread is inserted out of the amplifier and is connected with the boss through thread, and the loading gun, the amplifier and the boss are tightly attached. The height of the positioning cylinder is adjusted so that the stretching incident rod, the torsion incident rod and the loading device are on the same horizontal line.

[0022] Step 2, paste the strain gauge:

[0023] The stretching incident rod is pasted with the stretching strain gauge. When pasting, two identical stretching strain gauges are symmetrically pasted on the circumferential surface of the stretching incident rod at 1 / 2 of the length of the stretching incident rod. The strain gauge lead is welded on the pin of the stretching strain gauge, and the strain gauge lead is connected to the Wheatstone bridge in the data acquisition system.

[0024] The torsion incident rod is pasted with strain flowers. The strain flowers have three groups, and each strain flower is composed of two perpendicular strain gauges. When pasting, the angle bisector of the two strain gauges is parallel to the central axis of the incident rod, and is pasted at the middle between the torque loading mechanism and the clamping mechanism, 10 cm away from the clamping mechanism and the sample, and the middle between the clamping mechanism and the sample. When pasting the strain flowers, the three groups of strain flowers are respectively connected to the delay pulse generator and the Wheatstone bridge in the data acquisition system.

[0025] Step 3, load and collect data:

[0026] The sample is fixed between the torsion rod incident rod and the stretching incident rod, and the two ends of the sample are respectively fixed with the torsion rod incident rod and the stretching incident rod through thread. The loading gun is installed on the experimental table.

[0027] Install the fracture bolt; rotate the clamping bolt at the bottom of the clamping mechanism to clamp the torsion incident rod. The torque loading mechanism is rotated to apply torque to the torsion incident rod, and the applied torque is obtained through the strain flowers. When the voltage signal of the data acquisition system is 30 millivolts, stop

[0028] The torsion incident rod between the torque loading mechanism and the clamping mechanism is the energy storage section of the torsion incident rod. The torque loading mechanism is rotated to rotate the torsion incident rod. Since the clamping mechanism has clamped the torsion incident rod, the torsion incident rod produces torsional deformation, and the torque energy is stored in the energy storage section of the torsion incident rod.

[0029] Charging the capacitor of the electromagnetic Hopkinson tensile loading device. The charging voltage is 800v, and the amplitude of the tensile stress wave generated is 200MPa; the capacitance of the capacitor is 2mf, and the pulse width of the tensile stress wave generated is 300 microseconds.

[0030] After the charging is completed, the pulse delay generator is set to a standby trigger state, and the bolt below the clamping mechanism is continuously screwed until the broken bolt is continuously tensioned to break, so that the torque stored in the torsional incident rod can be released instantaneously, and a torsional wave with a steep rising edge is generated, which propagates on the torsional rod to the sample direction.

[0031] When the torsional wave reaches the strain flower position, the torsional strain gauge is deformed, the delay pulse generator is triggered, and after a set delay time, the electromagnetic gun of the electromagnetic tensile rod is discharged in turn, generating a tensile wave propagating to the sample at the end of the tensile rod, and the tensile wave and the torsional wave on the torsional incident rod arrive at the sample at the same time for loading. The delay time is 180ms,

[0032] At this point, the dynamic torsional-tensile / compression synchronous combined loading device is completed.

[0033] The application adopts a method of triggering the electromagnetic Hopkinson tensile / compression rod to generate a tensile / compression wave by a torsional wave signal, and controls the torsional wave and the tensile / compression wave to arrive at the sample at the same time through a delay pulse generator, so as to finally realize the torsional-tensile / compression composite dynamic loading. Compared with the prior art, the application has the following characteristics:

[0034] 1. The Hopkinson torsional rod is essentially a storage type Hopkinson torsional rod without a transmission rod. During the test, the broken bolt is installed, and the torsional incident rod is clamped by the clamping mechanism at a certain distance from the torque loading mechanism. Then, the torque loading mechanism is rotated to store energy, and the size of the energy can be obtained in real time by the strain gauge pasted on the torsional incident rod. After the energy storage is completed, the clamping bolt below the clamping mechanism is rotated to tension the broken bolt until it breaks at the slotted portion. Thereafter, the energy stored in the energy storage section is transmitted to the sample in the form of a stress wave. The strain gauge on the torsional incident rod can record the waveform of the torsional wave, and the torsional wave reaches the sample to perform dynamic torsional loading.

[0035] 2. The electromagnetic Hopkinson tensile / compression rod unit is a prior art. The electromagnetic Hopkinson tensile / compression loading device used in the application adopts the loading device proposed in the invention patent with the application number 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.

[0036] 3. The synchronous control part mainly relies on a delay pulse generator. After receiving the voltage information of the strain gauge on the torsional incident rod, the instrument delays for a certain time and then outputs the signal to the discharge switch of the electromagnetic Hopkinson tensile / compression loading device to generate tensile / compression stress wave. The accurate setting of the delay time can control the tensile / compression wave and the torsional wave to reach the sample at the same time.

[0037] The key technical problem to be solved by the present application is to trigger the discharge of the electromagnetic Hopkinson tensile / compression rod by the torsional wave signal to realize synchronous loading. In order to realize the loading of the torsional wave and the tensile / compression wave at the same time, the prerequisite is to meet the time condition relationship, that is, the time from the triggering position of the torsional wave signal to the sample should be greater than the time of the tensile / compression wave generated by the electromagnetic Hopkinson tensile / compression loading device and the time of the tensile / compression wave propagating on the tensile / compression incident rod, that is, to meet the relationship:

[0038]

[0039] Wherein, L n is the distance from the strain gauge on the torsional incident rod connected with the delay pulse generator to the sample, L l is the total length of the electromagnetic tensile / compression incident rod, T is the working time of the electromagnetic Hopkinson tensile / compression loading device, which includes the time of the discharge switch attraction and discharge process, C n and C l are the wave velocities of the torsional wave and the tensile / compression wave propagating in the rod respectively. During the test, the left side of the equation is usually greater than the right side by optimizing the circuit and changing the rod length. By setting the delay time t of the delay pulse generator, the right side of the equation plus t is equal to the left side of the equation, so that the torsional wave and the tensile / compression wave reach the sample at the same time for loading.

[0040] 4. The mechanical test part. Specifically, because the propagation forms of the stress wave on the torsional incident rod and the tensile / compression incident rod are different, the strain measurement is also different. The strain measurement on the torsional incident rod adopts strain gauge measurement, that is, two groups of torsional strain gauges perpendicular to each other and at 45 degrees to the axis direction of the rod. The strain measurement on the tensile / compression incident rod adopts a pair of strain gauges, and the strain grid direction of the strain gauge is parallel to the axis.

[0041] 5、The sample design part, key is to solve the connection problem between the sample and the loading rod under the combined action of stretching / compression and torsion. At present, the dynamic torsion sample is mostly thin-walled cylindrical and connected with the torsion rod by gluing, which can be used in dynamic torsion-compression loading; however, due to the low tensile strength of the gluing connection, the sample may be delaminated during the test, resulting in test failure, therefore, the connection mode of the dynamic tensile sample and the rod is mainly screw connection and clamp connection. According to the characteristics of the above two loading modes, the present application designs a thin-walled sample for dynamic tensile-torsion combined loading, and connects the sample with the torsion incident rod and the tensile incident rod by screw connection.

[0042] The screw connection is specifically that, during sample processing, external threads are processed on the surface of the part connected with the rod, and the outer diameter is smaller than the diameter of the rod. During rod end processing, internal threads are processed inside the slot. The sample clamping is to screw the sample into the middle of the two rods. It is worth noting that after the sample is installed, the direction of rotation of the torsion incident rod during operation should be the tightening direction of the sample, otherwise the torque cannot be applied, which requires that the screw rotation directions of the threads on the two sides of the sample gauge section are opposite.

[0043] As shown in Figure 3 The tensile pulse and torsion pulse signals collected by the data collector in the experiment, the trapezoidal wave is the torsion incident wave, and the sine wave is the tensile incident wave. It can be seen that the rising edges of the two wave trains coincide, ensuring the synchronization of the loading, and the torsion incident wave has a steep rising edge. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 The figure is a structural schematic diagram of the device of the present application.

[0045] Figure 2 The figure is a structural schematic diagram of the torsion sample; wherein, Figure 2 a is the front view, Figure 2 b is Figure 2 the right view of a.

[0046] Figure 3 The figure is the pulse signal collected by the data collector.

[0047] Figure 4 The figure is a structural schematic diagram of the clamping mechanism; wherein, Figure 4 a is the front view, Figure 4 b is Figure 4 the right view of a.

[0048] In the figure: 1. Torsion incident rod; 2. Broken bolt; 3. Clamping mechanism; 4. Clamping bolt; 5. Strain rosette; 6. Data collector; 7. Sample; 8. Delayed pulse generator; 9. Tensile strain gauge; 10. Tensile incident rod; 11. Loading gun; 12. Tensile incident rod boss; 13. Torque loading mechanism; 14. Chuck; 15. Clamping mechanism base. Detailed Implementation

[0049] This embodiment is a torsion-tension / compression synchronous composite loading device based on Hopkinson bar testing technology, including a Hopkinson torsion bar loading unit, an electromagnetic Hopkinson tension / compression bar unit, a synchronous control unit, and a mechanical testing unit. Wherein:

[0050] The Hopkinson torsion bar loading unit includes a torsion incident bar 1, a clamping mechanism 3, and a torque loading mechanism 13;

[0051] The torque loading mechanism adopts existing technology, namely a speed reducer. In this embodiment, the speed reducer model is WPSEDKS100-1 / 20-A. The proximal end of the torsion incident rod 1 is fixed to the torque loading mechanism and the two are tightly connected. The torque loading mechanism drives the torsion incident rod to rotate in order to apply torque.

[0052] The clamping mechanism 3 is mounted on the torsion incident rod 1 and clamps the torsion incident rod 1 through the chuck 14.

[0053] The fracture bolt 2 is mounted on the two clamping plates of the clamping head 14. By tightening the clamping bolt 4 and the clamping head 14 of the fracture bolt 2, the torsion incident rod 1 is clamped, so that there is no relative sliding between the torsion incident rod 1 and the clamping head 14.

[0054] The electromagnetic Hopkinson tension / compression bar unit is prior art, and this technical solution is disclosed in invention patent ZL201510956545.4; the electromagnetic Hopkinson tensile loading device disclosed in this invention patent includes a tensile incident bar 10 and an electromagnetic Hopkinson tensile loading device.

[0055] The electromagnetic Hopkinson tensile loading device consists of a power supply, a capacitor, a discharge switch, a loading gun housing, a main coil, a positioning cylinder, a secondary coil, and an insulating layer. The tensile wave generation process is as follows: The power supply first charges the capacitor, and after it is fully charged, it enters a ready-to-trigger state. Tightening the clamping bolts of the clamping mechanism causes the broken bolt to be continuously stretched until it breaks. At this time, a torsional wave is generated and propagates towards the sample. When the torsional stress wave reaches the strain rosette position in the rod, the strain rosette deforms, and the strain signal is converted into a voltage signal and transmitted to the delayed pulse generator. After a set delay time, the delayed pulse generator triggers the electromagnetic tensile loading device, and the discharge switch closes, at which point the capacitor discharges. At the instant the discharge switch closes, a rapidly changing impact current in the main coil generates a strong magnetic field around the coil. The secondary coil coupled to the main coil generates an induced current under the influence of the strong magnetic field, which in turn generates an eddy current magnetic field. The interaction of the two magnetic fields generates an eddy current repulsion force, which is transmitted to the boss through an amplifier. The compression wave generated by the boss reaches the right end of the boss and is reflected into a tensile wave, which propagates towards the sample to perform tensile loading.

[0056] The torsion incident rod and the electromagnetic tensile incident rod are both made of aluminum alloy with a diameter of 25 mm, wherein the length of the clamping mechanism to the sample end is 1.5 m, and the length of the tensile incident rod is 1.5 m.

[0057] The synchronous control unit comprises a delay pulse generator 8. The delay generator is a DG645 digital delay generator with a time accuracy of 10 ns, which meets the experimental requirements of the present application. The signal input end of the delay generator is connected to the strain gauge, and the signal output end is connected to the discharge switch of the tensile wave loading gun. Its function is to accurately control the time when the tensile wave loading gun generates the tensile wave, so that the torsional wave and the tensile wave reach the sample at the same time, thereby completing the tensile-torsional loading of the sample to obtain the dynamic mechanical properties of the material of the sample under complex stress state.

[0058] The mechanical test unit comprises a strain gauge 5, a tensile strain gauge 9 and a data acquisition device 6. The strain gauge 5, the tensile strain gauge 9 and the data acquisition device 6 are all existing technologies. Two identical tensile strain gauges are symmetrically pasted on the surface of the tensile incident rod with the axis of the tensile incident rod as the axis of symmetry on the circumference of half the length of the tensile incident rod, strain gauge leads are welded on the pins of the strain gauges, and the strain gauge leads are connected to the Wheatstone bridge in the data acquisition system. The strain gauge is connected to the Wheatstone bridge in the data acquisition system according to the above operation. The strain gauge has three groups, and each strain gauge is composed of two perpendicular strain gauges. When pasting, the angle bisector of the two strain gauges is parallel to the central axis of the incident rod, and is pasted at the middle between the torque loading mechanism and the clamping mechanism, 10 cm away from the clamping mechanism in the direction of the sample, and the middle between the clamping mechanism and the sample.

[0059] The present embodiment also proposes a method for loading by using the dynamic torsional-tensile / compressive synchronous combined loading device, and the specific process is as follows:

[0060] Step 1, arrange the equipment:

[0061] The electromagnetic Hopkinson tensile loading device, the tensile incident rod, the clamping mechanism, the torque loading mechanism and the torsional incident rod are sequentially installed on the experimental table. The torque loading mechanism and the torsional incident rod are assembled to tightly fit each other, and the torsional rod is freely rotated on the clamping mechanism and the positioning cylinder.

[0062] The loading gun is assembled with the tensile incident rod by the following method: the tensile incident rod with external thread is sequentially threaded through the positioning cylinder on the experimental table, the central hole of the loading gun and the through hole of the amplifier, and the tensile incident rod is freely fitted with the central hole of the loading gun, the through hole of the amplifier and the through hole of the positioning cylinder, so that the two incident rods can freely slide before being connected with other devices and the shafts are on the same horizontal line. The end of the tensile incident rod with external thread is threaded out of the amplifier and is connected with the boss through threads, and the loading gun, the amplifier and the boss are tightly attached. The height of the positioning cylinder is adjusted so that the tensile incident rod, the torsional incident rod and the loading device are on the same horizontal line.

[0063] Step 2, paste strain gauges:

[0064] In this embodiment, the strain information of the torsional incident rod is measured by strain gauges, and the strain information in the tensile incident rod is measured by tensile strain gauges with a specification of 1000Ω.

[0065] When the tensile strain gauges are pasted on the tensile incident rod, two identical tensile strain gauges are symmetrically pasted on the circumferential surface of the tensile incident rod at a length of 1 / 2. The strain gauge leads are welded on the leads of the tensile strain gauges, and the strain gauge leads are connected to the Wheatstone bridge in the data acquisition system.

[0066] Each of the three groups of strain gauges is composed of two perpendicular strain gauges, and the angle bisector of the two strain gauges is parallel to the central axis of the incident rod when pasted. The two strain gauges are respectively pasted at the middle between the torque loading mechanism and the clamping mechanism, at the middle between the clamping mechanism and the sample and 10 cm away from the clamping mechanism, and at the middle between the clamping mechanism and the sample.

[0067] Step 3, load and collect data:

[0068] The sample is fixed between the torsional rod incident rod and the tensile incident rod, and the two ends of the sample are respectively fixed with the torsional rod incident rod and the tensile incident rod through threads, so that the sample does not move relative to the two rods. The loading gun is installed on the experimental table.

[0069] The broken bolt is screwed into the upper part of the clamping mechanism, so that the notch of the broken bolt falls between the two clamping heads of the clamping mechanism. The clamping bolt at the bottom of the clamping mechanism is rotated to clamp the torsional incident rod. The torque loading mechanism is rotated to apply torque to the torsional incident rod, and the size of the torque is measured by the strain gauges on the energy storage section of the torsional incident rod. The part of the torsional incident rod between the torque loading mechanism and the clamping mechanism is the energy storage section of the torsional incident rod. The torque loading mechanism is rotated to drive the torsional incident rod to rotate. Since the clamping mechanism has clamped the torsional incident rod, the torsional incident rod produces torsional deformation and stores torque energy in the torsional incident rod between the torque loading mechanism and the clamping mechanism, i.e. the part of the torsional incident rod between the torque loading mechanism and the clamping mechanism is the energy storage section of the torsional incident rod.

[0070] The capacitor of the electromagnetic Hopkinson tensile loading device is charged. The charging voltage is 800v, and the amplitude of the tensile stress wave generated is 200MPa; the capacitance of the capacitor is 2mf, and the pulse width of the tensile stress wave generated is 300 microseconds.

[0071] After the charging is completed, the pulse delay generator is set to be in a standby state, and the clamping screw below the clamping mechanism is continuously tightened, so that the broken bolt is continuously subjected to tension until it is broken.

[0072] After the broken bolt is broken, the chuck cannot continue to clamp the torsional incident rod, so that the torque stored in the torsional incident rod can be released instantaneously, and a torsional wave with a steep rising edge is generated. The torsional wave propagates on the torsional rod to the sample direction. When the torsional wave reaches the strain flower position, the torsional strain gauge is deformed, triggering the delay pulse generator. After the delay time set by the delay pulse generator, the electromagnetic gun of the electromagnetic pull rod is discharged in turn, generating a tensile wave at the end of the pull rod and propagating to the sample. The tensile wave and the torsional wave on the torsional incident rod arrive at the sample at the same time to load. The delay time set in this embodiment is 180ms,

[0073] By accurately controlling the delay time, the torsional wave and the tensile wave can arrive at the sample at the same time in this embodiment, and dynamic tensile-torsional combined loading on the sample is realized. The data acquisition device simultaneously records the stress wave pulse signals on the torsional incident rod and the tensile incident rod, as shown in Figure 3 ​

Claims

1. A dynamic torsion-tension / compression synchronous combined loading device, characterized in that, The system includes a Hopkinson torsion bar loading unit, an electromagnetic Hopkinson tension / compression bar unit, a synchronization control unit, and a mechanical testing unit. 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 to the torque loading mechanism, and the two are tightly connected. The torque loading mechanism drives the torsion incident rod to rotate in order to apply torque. The clamping mechanism is fitted onto the torsion incident rod and clamps the torsion incident rod using chucks. The clamping mechanism includes a clamping mechanism base and a chuck; the chuck consists of two clamping plates and a fracture bolt, the two clamping plates are located parallel to each other inside the clamping mechanism base, and the clamping grooves located on the inner surfaces of the two clamping plates correspond to each other; the fracture bolt is installed at the upper end of the two clamping plates, and the notch in the middle of the fracture bolt is located between the two clamping plates of the clamping mechanism; the clamping bolt is located on two support plates of the clamping mechanism base; On the two clamping plates of the broken bolt mounting clamp, the torsion incident rod is clamped by tightening the clamping bolt and the broken bolt clamp, so that there is no relative slippage between the torsion incident rod and the clamp; One end of the tensile incident rod in the electromagnetic Hopkinson tension / compression rod unit is connected to the loading gun; the other end is a cantilever end, the end face of which corresponds to the end face of the torsional incident rod; the specimen is located between the tensile incident rod and the torsional incident rod; three sets of strain gauges are distributed on the outer circumferential surface of the incident rod, wherein the first set of strain gauges and the third set of strain gauges are respectively connected to the data acquisition unit through data lines; the second set of strain gauges is connected to the signal input terminal of the delay pulse generator of the synchronization control unit through data lines.

2. The dynamic torsion-tension / compression synchronous combined loading device as described in claim 1, characterized in that, The distance between the clamping mechanism and the sample end is 1.5m; the length of the tensile injection rod is 1.5m.

3. The dynamic torsion-tension / compression synchronous combined loading device as described in claim 1, characterized in that, The time accuracy of the delay pulse generator is 10 ns.

4. A method for loading using the dynamic torsion-tension / compression synchronous combined loading device as described in claim 1, characterized in that, The specific process is as follows: Step 1, Arrange the equipment: Install the electromagnetic Hopkinson tensile loading device, tensile injection rod, clamping mechanism, torque loading mechanism, and torsion injection rod on the experimental platform in sequence; assemble the torque loading mechanism and torsion injection rod to ensure a tight fit between them, and allow the torsion rod to rotate freely on the clamping mechanism and positioning cylinder; assemble the loading gun and tensile injection rod. Step 2, attach the strain gauges: The bonded strain gauge includes: Tensile strain gauges are attached to the tensile incident rod; during attachment, two tensile strain gauges are symmetrically attached to the circumferential surface at 1 / 2 of the length of the tensile incident rod; the tensile strain gauges are connected to the Wheatstone bridge in the data acquisition system; Strain rosettes are attached to the torsional incident rod; during attachment, the three sets of strain rosettes are respectively connected to the delay pulse generator and the Wheatstone bridge in the data acquisition system. Step 3, Load and collect data: The specimen is fixed between the torsion bar and the tension bar, and both ends of the specimen are respectively fixed to the torsion bar and the tension bar by threads; the loading gun is mounted on the test bench; Install the broken bolt; rotate the clamping bolt at the bottom of the clamping mechanism until the clamping mechanism clamps the torsion incident rod, apply torque to the torsion incident rod through the rotation torque loading mechanism, and obtain the applied torque through the strain gauge; stop when the voltage signal of the data acquisition system is 30 millivolts. The torsional incident rod is located between the torque loading mechanism and the clamping mechanism as a torsional incident rod energy storage section. When the torque loading mechanism is rotated, the torsional incident rod is rotated. Since the clamping mechanism has clamped the torsional incident rod, the torsional incident rod undergoes torsional deformation, storing torque energy in the torsional incident rod energy storage section. The capacitor of the electromagnetic Hopkinson tensile loading device is charged; the charging voltage is 800V, and the amplitude of the tensile stress wave is 200MPa; the capacitance of the capacitor is 2mF, and the pulse width of the tensile stress wave is 300 microseconds. After charging is complete, the pulse delay generator is set to the ready-to-trigger state, and the bolts under the clamping mechanism are tightened until the broken bolt breaks under tension, so that the torque stored in the torsion incident rod can be released instantaneously, generating a torsion wave with a steep rising edge, which propagates along the torsion rod toward the sample. When the torsional wave reaches the strain gauge position, it causes deformation of the torsional strain gauge, triggering the delayed pulse generator. After a set delay time, the delayed pulse generator then triggers the electromagnetic gun of the electromagnetic pull rod to discharge, generating a tensile wave at the end of the pull rod that propagates towards the sample. The tensile wave and the torsional wave on the torsional incident rod arrive at the sample simultaneously for loading. The delay time is 180 ms. This completes the loading of the dynamic torsion-tension / compression synchronous combined loading device.

5. The loading method as described in claim 4, characterized in that, The specific method for assembling the loading gun and the tensile incident rod is as follows: the threaded end of the tensile incident rod passes through the positioning cylinder on the experimental table, the center hole of the loading gun, and the through hole of the amplifier in sequence. The tensile incident rod freely engages with the center hole of the loading gun, the through hole of the amplifier, and the through hole of the positioning cylinder, so that the two incident rods can slide freely and their axes are on the same horizontal line before being connected to other devices. The threaded end of the tensile incident rod passes through the amplifier and is connected to the boss by a thread. The loading gun, amplifier, and boss are close together. The height of the positioning cylinder is adjusted so that the tensile incident rod, the torsion incident rod, and the loading device are on the same horizontal line.

6. The loading method as described in claim 4, characterized in that, There are three sets of strain flowers, each consisting of two mutually perpendicular torsional strain gauges; when pasted, the angle bisectors of the two torsional strain gauges are parallel to the central axis of the incident rod.

7. The dynamic torsion-tension / compression synchronous combined loading device as described in claim 1, characterized in that, Three sets of strain gauges are respectively attached in the middle between the torque loading mechanism and the clamping mechanism, 10cm away from the clamping mechanism in the direction of the sample, and in the middle between the clamping mechanism and the sample.

8. The dynamic torsion-tension / compression synchronous combined loading device as described in claim 1, characterized in that, The two tensile strain gauges are symmetrically attached to the circumference at 1 / 2 of the length of the tensile incident rod.

9. The dynamic torsion-tension / compression synchronous combined loading device as described in claim 1, characterized in that, In the three sets of strain rosettes, each strain rosette consists of two mutually perpendicular strain gauges. When pasting, the angle bisectors of the two strain gauges are parallel to the central axis of the incident rod. They are 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, respectively.

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