Dynamic shear deformation freezing and measuring system and method of monopulse torsion bar

Abstract

The invention relates to the technical field of dynamic mechanical testing, in particular to a dynamic shear deformation freezing and measuring system and method for a monopulse torsion bar, and the system comprises a torsion bar system, a monopulse loading mechanism and a measuring system. The torsion bar system comprises an incident bar and a transmission bar and is used for conducting torsion stress waves and clamping the thin-wall tubular sample; the single pulse loading mechanism absorbs reflected wave energy through cooperation of a wave unloading rod and a one-way coupler, single pulse loading is achieved, and secondary loading is avoided. The movable buckle is arranged on the incident rod and used for accurately adjusting the loading pulse width, and the movable buckle is matched with the one-way couplers and the wave unloading rods on the incident rod and the transmission rod to achieve single-pulse loading control, so that the loading pulse width can be accurately adjusted in the form of a frozen sample after loading. And the thermal-mechanical coupling data in the loading process is synchronously obtained by using the infrared transient temperature measurement detector and the strain rosette, so that a high-precision experimental means is provided for deeply researching the shear band formation, damage evolution and thermoplastic instability mechanism of the material under the high-strain-rate shear load.

Description

Technical Field

[0001] This invention relates to the field of dynamic mechanical testing technology, specifically to a system and method for freezing and measuring the dynamic shear deformation of a single-pulse torsion bar. Background Technology

[0002] The Hopkinson torsion bar is a key experimental apparatus for studying the shear mechanical behavior of engineering materials such as metals, composites, and ceramics under high strain rates. By applying dynamic torsional loads to specimens through the torsion bar system, the dynamic shear stress-strain relationship, strain rate sensitivity, and shear failure characteristics of the materials can be obtained, providing important data support for material design and safety assessment under dynamic loading conditions such as impact, penetration, and explosion.

[0003] However, in traditional Hopkinson torsion bar systems, the torsional wave is transmitted back and forth in the bar until it is consumed, causing the stress wave to reflect back to the specimen after being reflected at the end of the bar. This results in the specimen undergoing multiple loadings, making the final deformation state a cumulative result of multiple loadings. It is difficult to establish a clear correspondence with a specific loading process, and it lacks the ability to measure transient temperatures that are strictly synchronized with the dynamic loading process, making it difficult to obtain reliable thermo-mechanical coupling evolution data.

[0004] Therefore, existing Hopkinson torsion bar systems are difficult to suppress the stress waves that are transmitted back and forth within the bar, resulting in the specimen being loaded multiple times and accumulating shape. Furthermore, it is difficult to establish a clear correspondence with a specific loading process and to perform thermodynamic measurements on the loading of the specimen, thus making it difficult to match the specimen deformation with the thermodynamic information in the loading process. Summary of the Invention

[0005] The purpose of this invention is to provide a dynamic shear deformation freezing and measurement system and method for single-pulse torsion bars, in order to solve the technical problem in the prior art that the stress waves transmitted back and forth in the bar are difficult to suppress, resulting in the accumulation of the specimen after multiple loadings, and it is difficult to establish a clear correspondence with a specific loading process and to perform thermodynamic measurement on the loading of the specimen, thus making it difficult to match the specimen deformation with the thermodynamic information in the loading process.

[0006] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0007] A dynamic shear deformation freezing and measurement system for a single-pulse torsion bar includes:

[0008] A torsion bar system comprising an incident bar and a transmission bar arranged sequentially along the same axis, for applying a dynamic torsional load to a specimen held between the two.

[0009] A single-pulse loading mechanism includes a loading end disposed on the incident rod and a wave-reducing rod disposed at the end of the incident rod and the transmission rod away from the sample. The incident rod and the transmission rod are connected to the wave-reducing rod by a one-way coupler. The one-way coupler is configured to transmit torsional load during the loading phase and allow relative sliding between the torsion rod and the wave-reducing rod after the stress wave passes through, so as to block the reflected wave from returning to the loading incident rod 2 and the transmission rod 3.

[0010] The measurement system includes an infrared transient temperature sensor and strain gauges disposed on the incident rod and the transmission rod. The measurement system acquires the temperature of the sample in real time through the infrared transient temperature sensor and acquires the shear strain of the incident rod and the transmission rod in real time through the strain gauges.

[0011] When the torque applied to the incident rod at the loading end is released instantaneously, the unloading rod absorbs the reflected wave energy to freeze the deformation morphology of the sample after being subjected to a single torsional pulse wave. At the same time, the measurement system synchronously collects strain, stress and temperature data through the strain rosette and the infrared transient temperature detector to form thermo-mechanical coupling information, providing data for the formation of shear bands, damage evolution and instability mechanism of materials under high strain rate shear load.

[0012] Furthermore, the specimen is a thin-walled tubular structure, so that its gauge length region is in an approximately simple shear strain state during torsion.

[0013] As a preferred embodiment of the present invention, a movable buckle is provided on the incident rod, the loading end is disposed away from the sample, and the movable buckle is disposed between the loading end and the sample;

[0014] The movable latch is configured to move and lock between the loading end and the thin-walled tubular specimen to adjust the length of the torque storage zone of the incident rod between the loading end and the movable latch, thereby controlling the loading pulse width and the target shear strain.

[0015] Furthermore, the movable latch is configured to release instantaneously to trigger the torque stored in the torque energy storage area to form a single torsional pulse wave.

[0016] In a preferred embodiment of the present invention, the wall thickness and outer diameter of the sample satisfy the following:

[0017] ;

[0018] in, For wall thickness, It is the outer diameter.

[0019] As a preferred embodiment of the present invention, the unidirectional coupler includes a transition structure fitted on the end of the incident rod, the end of the transmission rod, and the end of the wave-removing rod. The transition structure includes a positive connection part, a negative connection part, and a slider.

[0020] The positive connection is configured to allow the complete transmission of torsional waves in a predetermined direction. When a reflected wave in the opposite direction is transmitted to the negative connection, the slider is driven to move to disconnect the connection between the positive and negative connections, thus isolating the reflected wave within the wave-relief rod.

[0021] As a preferred embodiment of the present invention, a first strain rose is provided on the area of ​​the incident rod between the movable buckle and the sample and / or on the transmission rod, for connecting a dynamic strain gauge to measure the incident wave and transmitted wave signals.

[0022] A second strain gauge is provided on the torque storage area of ​​the incident rod located between the loading end and the movable buckle, for connecting a static strain gauge to measure the magnitude of the preloaded torque;

[0023] The amplitude of the incident torsional wave and the loading strain rate of the specimen are controlled by measuring and adjusting the magnitude of the preloaded torque.

[0024] As a preferred embodiment of the present invention, the movable buckle includes a clamp sleeved on the incident rod, a momentary bolt for locking the clamp at a designated position on the incident rod, and a fastening nut.

[0025] A scale is provided on the adjacent support frame of the incident rod to mark the axial position of the movable buckle.

[0026] As a preferred embodiment of the present invention, the measurement system further includes:

[0027] A dynamic data acquisition system, which is connected to the first strain rose via a dynamic strain gauge, is used to acquire and process torsional load waveform data in real time;

[0028] The static data acquisition system is connected to the second strain rosette via a static strain gauge and is used to measure a preset shear strain rate.

[0029] As a preferred embodiment of the present invention, the measurement system further includes a parabolic mirror, which is used to focus the infrared radiation from the sample surface onto the infrared transient temperature detector, and the infrared transient temperature detector is positioned facing the sample surface.

[0030] The infrared transient temperature detector is triggered synchronously with the dynamic data acquisition system to synchronously record the temperature rise of the sample surface during single-pulse loading.

[0031] To address the aforementioned technical problems, the present invention further provides the following technical solution:

[0032] A method for freezing and measuring dynamic shear deformation using the above-mentioned single-pulse torsion bar includes the following steps:

[0033] Step 100: Install the thin-walled tubular sample between the incident rod and the transmission rod, calculate the required loading pulse width based on the target shear strain, and adjust and lock the axial position of the movable latch on the incident rod accordingly.

[0034] Step 200: Apply pre-torque through the loading end, store it in the incident rod segment between the loading end and the movable buckle, and trigger the movable buckle to release instantaneously, generating a single torsional pulse wave to load the sample. At the same time, synchronously collect torsional load waveform data and transient temperature data of the sample surface. Among them, after the stress wave is transmitted to the unloading rod through the unidirectional coupler, the reflected wave is isolated, and the deformation state of the sample under the target shear strain is frozen.

[0035] Step 300: Characterize the microstructure of the deformed and frozen sample, and perform correlation analysis between the characterization results and the synchronously acquired mechanical and temperature data.

[0036] In a preferred embodiment of the present invention, in step 100, the formula for determining and adjusting the torsional pulse width is as follows:

[0037] ;

[0038] in, To load the pulse width, The distance between the movable latch and the loading end. The torsional wave velocity of the rod.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] This invention achieves single-pulse loading control by setting a movable buckle on the incident rod and cooperating with a unidirectional coupler and a wave-reducing rod on the incident rod and the transmission rod, so as to freeze the morphology of the sample after loading. Furthermore, it utilizes an infrared transient temperature detector and a strain rosette to simultaneously obtain thermo-mechanical coupling data during the loading process, providing a high-precision experimental means for in-depth research on the shear band formation, damage evolution, and thermoplastic instability mechanism of materials under high strain rate shear loads. Attached Figure Description

[0041] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0042] Figure 1 A schematic diagram of the dynamic shear deformation freezing and measurement system for a single-pulse torsion bar provided in an embodiment of the present invention;

[0043] Figure 2 A schematic diagram of the unidirectional coupler part of the dynamic shear deformation freezing and measurement system for a single-pulse torsion bar provided in an embodiment of the present invention;

[0044] Figure 3 A schematic diagram of the movable latching part of the dynamic shear deformation freezing and measurement system for a single-pulse torsion bar provided in an embodiment of the present invention;

[0045] Figure 4 A schematic diagram of the sample portion structure of the dynamic shear deformation freezing and measurement system for a single-pulse torsion bar provided in an embodiment of the present invention;

[0046] Figure 5 A schematic diagram comparing the multi-pulse and single-pulse effects of the dynamic shear deformation freezing and measurement system for a single-pulse torsion bar provided in an embodiment of the present invention.

[0047] Figure 6 This is a schematic diagram of pulse width control for a dynamic shear deformation freezing and measurement system for a single-pulse torsion bar provided in an embodiment of the present invention.

[0048] The labels in the diagram represent the following:

[0049] 1-Unloading rod; 2-Incident rod; 3-Transmission rod; 4-One-way coupler; 5-Loading end; 6-Modible buckle; 7-Temperature measuring bracket; 8-Parabolic mirror; 9-Infrared transient temperature detector;

[0050] 10-Base; 11-Base support; 12-Clamping end; 13-Specimen; 14-First strain rosette; 15-Second strain rosette; 16-Positive connection; 17-Negative connection; 18-Slider; 19-Clamping head;

[0051] 20 - Instantaneous break bolt; 21 - Fastening nut. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Example 1:

[0054] like Figure 1 As shown, this invention provides a dynamic shear deformation freezing and measurement system for a single-pulse torsion bar, primarily used to study the formation of shear bands, damage evolution, and thermo-mechanical coupling instability mechanisms of materials under high strain rate shear loads. This system can precisely "freeze" the deformation state of the material after a single torsional pulse loading, and simultaneously acquire stress, strain, and transient temperature rise data.

[0055] The system mainly consists of three parts: a torsion bar system, a single-pulse loading mechanism, and a measurement system.

[0056] The torsion bar system is the main load-bearing and loading frame for the test. It includes an incident bar 2 and a transmission bar 3, precisely aligned sequentially along the same horizontal axis and mounted on the base 10. The specimen 13 is tightly clamped by clamping ends 12 at the opposite ends of the incident bar 2 and the transmission bar 3. The incident bar 2 and the transmission bar 3 typically possess high elastic modulus and good waveguide properties to ensure that the stress wave waveform remains undistorted as it propagates within the bars. The incident bar 2 transmits the torsional load generated by the loading mechanism to the specimen 13 in the form of a stress wave; the transmission bar 3 receives and transmits the stress wave transmitted from the deformed specimen 13.

[0057] The single-pulse loading mechanism is used to generate a single, controllable torsional pulse. Its main components include a loading end 5 located at the end of the incident rod 2 furthest from the sample 13, a movable latch 6 that can move and lock along the axial direction of the incident rod 2, and a wave-relief rod 1 located at the other end of the incident rod 2 and the transmission rod 3. The ends of the incident rod 2 and the transmission rod 3 are connected to the wave-relief rod 1 via a one-way coupler 4. Both the wave-relief rod 1 and the transmission rod 3 are mounted on the base 10 via a base bracket 11.

[0058] The loading end 5 can be a torque loading head fixed to the end of the incident rod 2 away from the sample 13, which can apply a stable pre-torsional torque manually or hydraulically.

[0059] The movable latch 6 is fitted onto the incident rod 2, located between the loading end 5 and the sample 13. It primarily functions as a mechanical "switch" that can be released instantaneously. During the loading preparation phase, the movable latch 6 is locked onto the base 10, and after a pre-torsional torque is applied to the incident rod 2, it clamps the incident rod 2 to a predetermined axial position, dividing the incident rod 2 into two sections: a "torque storage zone" located between the loading end 5 and the movable latch 6, and a "waveguide zone" located between the movable latch 6 and the sample 13.

[0060] The length of the torque storage zone can be changed by adjusting the axial position of the movable latch 6. According to the formula (in, To load the pulse width, To achieve precise control of the incident torsional pulse wave width (the wave velocity of the torsional wave in the rod), when a pre-torque is applied through the loading end 5, the torque energy is stored in the rod segment within the torque storage zone due to the locking of the movable latch 6, causing it to undergo shear elastic deformation. Upon triggering, the movable latch 6 is instantaneously released, and the elastic strain energy stored in the storage zone is released instantaneously, forming a single torsional pulse wave that propagates towards the sample 13.

[0061] The wave unloading rod 1 and the unidirectional coupler 4 together constitute the "wave absorption and isolation" unit. The unidirectional coupler 4 is a key component, configured with directional selective wave transmission characteristics. During the loading stage, the incident wave or transmitted wave (mainly the main pulse driving the deformation of the sample 13 in this system) from the direction of the sample 13 can be transmitted to the wave unloading rod 1 with almost no loss through the unidirectional coupler 4.

[0062] When the stress wave is reflected at the free end of the unloading rod 1 to form a reflected wave and propagates back, the one-way coupler 4 can sense this reverse propagating wave and trigger the internal mechanism, causing the connection between the torsion bar (incident rod 2 / transmission rod 3) and the unloading rod 1 to slip (mechanically "disconnected" or "slipped"), thereby isolating the reflected wave within the unloading rod 1 and preventing it from returning to the specimen 13 and the incident rod 2, thus avoiding secondary loading of the reflected wave. This process absorbs the energy of the reflected wave, so that after the specimen 13 has undergone a single main pulse loading, it is no longer subject to secondary loading or interference from subsequent reflected waves, and its deformation state is "frozen" at the target strain value.

[0063] The measurement system is used to simultaneously acquire mechanical and thermal data. The mechanical measurement component includes strain gauges (or strain flowers) attached to the incident rod 2 and the transmission rod 3. Specifically:

[0064] A set of first strain rosettes 14 are attached to the waveguide region of the incident rod 2 (between the movable latch 6 and the specimen 13) and the transmission rod 3, respectively. These are connected to a dynamic strain gauge for real-time, high-frequency measurement of the shear strain signals of the incident torsional pulse wave and the transmitted torsional pulse wave. According to the one-dimensional elastic stress wave theory, the torque and rotation angle difference at both ends of the specimen can be calculated from these signals, thereby obtaining the shear stress-shear strain response of the specimen. A second strain rosette 15 is attached to the torque storage region of the incident rod 2 (between the loading end 5 and the movable latch 6). It is connected to a static strain gauge for measuring the static shear strain of the rod segment during the preloading stage, thereby accurately calculating and calibrating the stored torque value. This torque value directly determines the amplitude of the incident pulse wave and the initial loading strain rate of the specimen.

[0065] The core of the thermal measurement section is the infrared transient temperature detector 9. To measure the minute surface temperature rise of the sample 13 during its microsecond-level dynamic deformation with high sensitivity, the system is typically equipped with a parabolic mirror 8. Both the parabolic mirror 8 and the infrared transient temperature detector 9 are fixed to the base 10 via a temperature measuring bracket 7 and positioned above the sample 13. The parabolic mirror 8 efficiently focuses the infrared radiation emitted from the gauge length of the sample 13 onto the sensitive element of the infrared transient temperature detector 9, significantly improving the signal-to-noise ratio and spatial resolution of the temperature measurement. The acquisition by the infrared transient temperature detector 9 and the dynamic strain gauge is synchronously activated by the same trigger signal, ensuring a strict correspondence between the mechanical and temperature data at every moment, forming time-synchronized thermo-mechanical coupling information.

[0066] Among them, such as Figure 4 As shown, sample 13 is designed as a thin-walled tubular structure (preferably resembling a thin-walled wheel-like structure). Its wall thickness... With outer diameter The ratio satisfies: This design ensures that the stress state within the gauge length of specimen 13 under torsional load closely approximates an ideal simple shear state. The shear stress is uniformly distributed along the wall thickness, avoiding interference from complex stress states such as bending, thus providing a guarantee for studying the pure shear mechanical behavior of the material. Specifically, the shear strain on the cross-section of specimen 13 is uniformly distributed radially, and there is an approximately linear relationship between the torsional angles at both ends of specimen 13 and the shear strain of the cross-section of specimen 13, thereby obtaining a simple shear strain state, which facilitates shear failure analysis and instability identification.

[0067] Based on the above-mentioned dynamic shear deformation freezing and measurement system for a single-pulse torsion bar, a method for freezing and measuring material deformation is provided, including the following steps:

[0068] Step 100: Install the thin-walled tubular sample between the incident rod and the transmission rod, calculate the required loading pulse width based on the target shear strain, and adjust and lock the axial position of the movable latch on the incident rod accordingly.

[0069] Step 200: Apply pre-torque through the loading end, store it in the incident rod segment between the loading end and the movable buckle, and trigger the movable buckle to release instantaneously, generating a single torsional pulse wave to load the sample. At the same time, synchronously collect torsional load waveform data and transient temperature data of the sample surface. Among them, after the stress wave is transmitted to the unloading rod through the unidirectional coupler, the reflected wave is isolated, and the deformation state of the sample under the target shear strain is frozen.

[0070] Step 300: Characterize the microstructure of the deformed and frozen sample, and perform correlation analysis between the characterization results and the synchronously acquired mechanical and temperature data.

[0071] In a preferred embodiment of the present invention, in step 100, the formula for determining and adjusting the torsional pulse width is as follows:

[0072] ;

[0073] in, To load the pulse width, The distance between the movable latch and the loading end. For torsional wave speed

[0074] Specifically:

[0075] Install thin-walled tube specimen 13. Calculate the required loading pulse width based on the target shear strain rate and total strain. According to the formula Calculate the required length of the torque storage region Then, the movable latch 6 is moved to the corresponding position along the scale on the incident rod 2 and locked and fixed on the base 10.

[0076] A pre-torque is slowly applied through loading end 5, and the signal of the second strain flower 15 is monitored by a static strain gauge until the torque reaches the preset value. Then, the movable latch 6 is released instantaneously, releasing the elastic strain energy stored in the torque storage region of the incident rod 2, forming a single torsional pulse wave. This pulse wave is applied to the sample 13 through the waveguide region, causing it to undergo high strain rate shear deformation. The pulse wave continues to propagate, enters the unloading rod 1 through the unidirectional coupler 4, and is reflected by its free end, but the reflected wave is isolated by the unidirectional coupler 4. Simultaneously, the dynamic strain gauge and the infrared transient temperature detector 9 are triggered to record the strain waveform on the incident / transmission rod 3 and the transient temperature changes on the surface of the sample 13 throughout the process.

[0077] After loading, the deformation of sample 13 was "frozen". Sample 13 was removed, and the microstructure of the localized deformation regions (such as shear bands) was finely characterized using microscopic analysis techniques such as scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Finally, as... Figure 5 , Figure 6 As shown, the correlation analysis between the microstructural characteristics and the stress-strain curves and temperature rise curves obtained by synchronous measurement reveals the thermoplastic instability mechanism and damage evolution law in the dynamic shear deformation of materials.

[0078] Example 2:

[0079] Based on Example 1, such as Figure 2 As shown, the one-way coupler 4 can be a combination of a mechanical one-way clutch and a waveguide structure. It includes a transition structure fitted onto the end of the incident rod 2 (or the transmission rod 3) and the end of the wave-reducing rod 1. The transition structure contains a positive connection part 16, a negative connection part 17, and a slider 18.

[0080] In the initial state and when the loaded wave (assuming it is a clockwise torsional wave) is introduced, the positive connection part 16 and the negative connection part 17 engage, rigidly coupling the torsion bar (incident bar 2 / transmission bar 3) and the wave-removing bar 1 together, and the torsional wave is almost completely transmitted to the wave-removing bar 1.

[0081] When the reflected wave (counterclockwise torsional wave) generated at the free end of the wave-relief rod 1 returns to the unidirectional coupler 4, the reverse torque acts on the negative connection 17, driving the associated slider 18 to move axially or radially. The movement of the slider 18 forces the positive connection 16 to disengage from the negative connection 17, allowing the torsion bar (incident rod 2 / transmission rod 3) end and the wave-relief rod 1 end to rotate freely relative to each other, i.e., the mechanical connection is broken. At this time, the energy of the reflected wave cannot be transmitted back to the torsion bar system and is effectively isolated within the wave-relief rod 1. The reflected wave reflects back and forth in the wave-relief rod 1 and gradually dissipates due to internal friction.

[0082] Example 3:

[0083] Based on Example 1, such as Figure 3 As shown, the movable latch 6 includes a split clamp 19 that fits onto the incident rod 2. The inner hole of the clamp 19 precisely matches the outer diameter of the incident rod 2, and a radially applied clamping force can securely lock it at any designated position on the incident rod 2. To achieve "instant release," at least one pair of high-strength instantaneous bolts 20 and matching fastening nuts 21 are used to provide the main locking force.

[0084] The instantaneous break bolt 20 has a preset fracture groove. When loading needs to be triggered, an external device applies a lateral impact force to the instantaneous break bolt 20, causing it to break instantaneously at the fracture groove. The clamping force of the chuck 19 on the incident rod 2 is immediately lost, thereby realizing the instantaneous release of the movable latch 6, and the torque in the energy storage area is suddenly released.

[0085] In addition, to facilitate precise position adjustment, a precise scale (or grating ruler) is provided on the adjacent support frame (not shown in the figure) supporting the incident rod 2. The operator can use this to accurately position the movable latch 6 to the calculated length. The corresponding axial position.

[0086] It is worth noting that the present invention generates a single pulse by instantaneously releasing the movable buckle 6, and combines it with the unidirectional coupler 4 to absorb the reflected wave, ensuring that the sample 13 only experiences one main pulse loading, and the deformation state is clearly frozen, which is convenient for subsequent microscopic analysis and avoids the complex superimposed deformation caused by multiple loading in the Hopkinson rod.

[0087] Furthermore, the infrared transient temperature measurement and dynamic strain measurement are strictly synchronized, which can directly obtain the correspondence between the temperature rise and stress-strain evolution of localized regions (such as shear bands) during deformation, providing key data for establishing constitutive models.

[0088] Furthermore, by adjusting the position of the movable latch to control the pulse width (thereby controlling the total strain) and by adjusting the pre-torque to control the amplitude (thereby controlling the strain rate), flexible and precise design of the loading history is achieved.

[0089] Furthermore, the thin-walled tubular specimen 13 ensured a stress state of approximately simple shear, allowing the research conclusions to focus more on the shear mechanical behavior of the material itself.

[0090] In summary, this invention, through the combination of "movable latch pulse width control" and "unidirectional coupler waveform isolation," has for the first time achieved a one-to-one correspondence between "single-pulse loading process—unique strain path—frozen morphology" in dynamic torsion testing. This not only accurately obtains frozen morphologies corresponding to different shear strain levels without secondary loading interference, but also simultaneously acquires reliable thermo-mechanical coupling data during the process. This provides a high-precision experimental method for in-depth research on shear band formation, damage evolution, and thermoplastic instability mechanisms of materials under high strain rate shear loads.

[0091] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A dynamic shear deformation freezing and measurement system for a single-pulse torsion bar, characterized in that, include: A torsion bar system comprising an incident bar (2) and a transmission bar (3) arranged sequentially along the same axis, for applying a dynamic torsional load to a specimen (13) held between the two; A single-pulse loading mechanism includes a loading end (5) disposed on the incident rod (2) and a wave-reducing rod (1) disposed at the end of the incident rod (2) and the transmission rod (3) away from the sample (13). The incident rod (2) and the transmission rod (3) are connected to the wave-reducing rod (1) by a one-way coupler (4). The one-way coupler (4) is configured to transmit torsional load during the loading phase and allow relative sliding between the torsion bar and the wave-reducing rod after the stress wave passes through, so as to block the reflected wave from returning to the loading incident rod (2) and the transmission rod (3). The measurement system includes an infrared transient temperature detector (9) and strain gauges set on the incident rod (2) and the transmission rod (3). The measurement system collects the temperature of the sample (13) in real time through the infrared transient temperature detector (9) and collects the shear strain of the incident rod (2) and the transmission rod (3) in real time through the strain gauges. When the torque applied to the incident rod (2) at the loading end (5) is released instantaneously, the unloading rod (1) absorbs the reflected wave energy to freeze the deformation morphology of the sample (13) after being subjected to a single torsional pulse wave. At the same time, the measurement system synchronously collects strain, stress and temperature data through the strain rosette and the infrared transient temperature detector (9) to form thermo-mechanical coupling information, providing data for the shear band formation, damage evolution and instability mechanism of materials under high strain rate shear load. Furthermore, the specimen (13) is a thin-walled tubular structure, so that its gauge length region is in an approximately simple shear strain state during the torsion process.

2. The dynamic shear deformation freezing and measurement system for a single-pulse torsion bar according to claim 1, characterized in that, A movable buckle (6) is provided on the incident rod (2), the loading end (5) is located away from the sample (13), and the movable buckle (6) is located between the loading end (5) and the sample (13). The movable latch (6) is configured to move and lock between the loading end (5) and the thin-walled tubular specimen (13) to adjust the length of the torque storage zone of the incident rod (2) between the loading end (5) and the movable latch (6), and to control the loading pulse width and target shear strain. Furthermore, the movable latch (6) is configured to release instantaneously to trigger the torque stored in the torque energy storage area to form a single torsional pulse wave.

3. The dynamic shear deformation freezing and measurement system for a single-pulse torsion bar according to claim 1, characterized in that, The wall thickness and outer diameter of the sample (13) satisfy the following: ； in, For wall thickness, It is the outer diameter.

4. The dynamic shear deformation freezing and measurement system for a single-pulse torsion bar according to claim 1, characterized in that, The unidirectional coupler (4) includes a transition structure fitted on the end of the incident rod (2), the end of the transmission rod (3), and the end of the wave-removing rod (1). The transition structure includes a positive connection part (16), a negative connection part (17), and a slider (18). The positive connection (16) is configured to allow the torsional wave in a predetermined direction to be fully transmitted. When the reflected wave in the opposite direction is transmitted to the negative connection (17), the slider (18) is driven to move to disconnect the connection between the positive connection (16) and the negative connection (17) and isolate the reflected wave in the wave-relief rod (1).

5. The dynamic shear deformation freezing and measurement system for a single-pulse torsion bar according to claim 1, characterized in that, A first strain gauge (14) is provided on the area between the movable buckle (6) and the sample (13) of the incident rod (2) and / or on the transmission rod (3) for connecting a dynamic strain gauge to measure the incident wave and transmitted wave signals. A second strain gauge (15) is provided on the torque storage area of ​​the incident rod (2) between the loading end (5) and the movable buckle (6) for connecting a static strain gauge to measure the magnitude of the preloaded torque; The amplitude of the incident torsional wave and the loading strain rate of the specimen (13) are controlled by measuring and adjusting the magnitude of the preloaded torque.

6. The dynamic shear deformation freezing and measurement system for a single-pulse torsion bar according to claim 2, characterized in that, The movable buckle (6) includes a clamp (19) sleeved on the incident rod (2), a break bolt (20) for locking the clamp (19) at a designated position on the incident rod (2), and a fastening nut (21). The adjacent support frame of the incident rod (2) is provided with a scale for calibrating the axial position of the movable buckle.

7. The dynamic shear deformation freezing and measurement system for a single-pulse torsion bar according to claim 4, characterized in that, The measurement system also includes: The dynamic data acquisition system is connected to the first strain gauge (14) via a dynamic strain gauge and is used to acquire and process torsional load waveform data in real time. The static data acquisition system is connected to the second strain gauge (15) via a static strain gauge and is used to measure the preset shear strain rate.

8. The dynamic shear deformation freezing and measurement system for a single-pulse torsion bar according to claim 7, characterized in that, The measurement system also includes a parabolic mirror (8), which is used to focus the infrared radiation from the surface of the sample (13) onto the infrared transient temperature detector (9), and the infrared transient temperature detector (9) is positioned facing the surface of the sample (13). The infrared transient temperature detector (9) is triggered synchronously with the dynamic data acquisition system to synchronously record the temperature rise on the surface of the sample (13) during the single-pulse loading process.

9. A method for freezing and measuring the dynamic shear deformation of a single-pulse torsion bar according to any one of claims 2-8, characterized in that, Includes the following steps: Step 100: Install the thin-walled tubular sample between the incident rod and the transmission rod, calculate the required loading pulse width based on the target shear strain, and adjust and lock the axial position of the movable latch on the incident rod accordingly. Step 200: Apply pre-torque through the loading end, store it in the incident rod segment between the loading end and the movable buckle, and trigger the movable buckle to release instantaneously, generating a single torsional pulse wave to load the sample. At the same time, synchronously collect torsional load waveform data and transient temperature data of the sample surface. Among them, after the stress wave is transmitted to the unloading rod through the unidirectional coupler, the reflected wave is isolated, and the deformation state of the sample under the target shear strain is frozen. Step 300: Characterize the microstructure of the deformed and frozen sample, and perform correlation analysis between the characterization results and the synchronously acquired mechanical and temperature data.

10. The method for precise freezing and synchronous temperature measurement under dynamic shear deformation according to claim 9, characterized in that, In step 100, the formula for determining and adjusting the torsional pulse width is: ； in, To load the pulse width, The distance between the movable latch and the loading end. The torsional wave velocity of the rod.

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