CN-120577135-B - Separated Hopkinson pull rod device and method for realizing single pulse loading

Abstract

The invention provides a separated Hopkinson pull rod device for realizing single pulse loading, which comprises an incident rod, a transmission rod, an incident wave-catching unit and a stress wave generating unit, wherein the incident wave-catching unit comprises an incident wave-catching sleeve and an absorption rod, one end of the absorption rod is arranged at intervals with an incident rod flange, the other end of the absorption rod is connected with the absorption rod flange, the incident wave-catching sleeve is sleeved outside the absorption rod, the two ends of the incident wave-catching sleeve are respectively attached to the absorption rod flange and the incident rod flange, and a part of compression stress wave generated by the stress wave generating unit is reflected by the incident rod flange to form a tensile stress wave loading sample and then reflected back in a compression wave mode to be absorbed by the incident wave-catching unit. The problem of traditional Hopkinson pole multiple reflection interference is solved, pure monopulse tensile loading is realized, compact structure and high energy utilization rate are applicable to the dynamic mechanical properties test of material.

Inventors

• WANG HUANRAN
• YE SIGEN
• ZHANG ZHEN

Assignees

• 宁波大学

Dates

Publication Date

20260505

Application Date

20250703

Claims (9)

1. 1. The separated Hopkinson pull rod device for realizing single pulse loading is characterized by comprising an incident rod, an incident wave capturing unit and a stress wave generating unit; one end of the incidence rod is connected with the incidence rod flange, and the other end of the incidence rod is used for loading a sample; The incident wave-capturing unit comprises an incident wave-capturing sleeve and an absorption rod, one end of the absorption rod is opposite to the incident rod flange at a certain interval, the other end of the absorption rod is connected with the absorption rod flange, the incident wave-capturing sleeve is sleeved outside the absorption rod, and two ends of the incident wave-capturing sleeve are respectively attached to the absorption rod flange and the incident rod flange; the stress wave generating unit is arranged at one end of the incident rod, which is close to the flange of the incident rod, and is used for forming compression stress waves; The compression stress wave propagates along the flange of the incidence rod, and forms 2 stress waves after reaching the flange terminal, wherein one compression stress wave reaches the flange terminal of the incidence rod and is reflected to form a tensile stress wave which is transmitted along the incidence rod and loads a sample; The compression stress wave transmitted along the incident wave-capturing sleeve reaches the flange of the absorption rod and is transmitted along the flange, after reaching the terminal end of the flange, the compression stress wave is reflected to form a tensile stress wave to be transmitted along the absorption rod, and the absorption rod flange and the absorption rod are separated from the incident wave-capturing sleeve together with the absorption rod, so that the transmission of the subsequent stress wave is blocked; When the tensile stress wave transmitted along the incident rod reaches the connection position of the incident rod and the sample, due to the change of the interface, a part of the tensile stress wave reaches the interface to form a reflected compression wave to return to the incident rod, and a part of the tensile stress wave is transmitted along the sample to load the sample, the reflected compression wave is transmitted to the incident wave-catching sleeve after reversely transmitted along the incident rod to reach the flange terminal of the incident rod, and is reflected by the free end of the incident wave-catching sleeve to form the tensile stress wave, and due to the action of the tensile stress wave, the incident wave-catching sleeve is separated from contact with the flange of the incident rod, the transmission of the subsequent stress wave to the incident rod is blocked, so that the sample is only subjected to the action of one-time tensile wave, and the sample is subjected to single pulse loading.
2. 2. The separated Hopkinson pull rod device for realizing single pulse loading according to claim 1 is characterized by further comprising a transmission rod and a transmission wave-catching unit, wherein the transmission rod and the transmission wave-catching unit are coaxially arranged with an incident rod, one end of the transmission rod is connected with a transmission rod flange, a sample is loaded between the other end of the transmission rod and the incident rod, the transmission wave-catching unit is a transmission wave-catching sleeve sleeved on the outer side of the tail end of the transmission rod and attached to the transmission rod flange, a transmission wave is formed after the sample is loaded by the tensile stress wave and is transmitted along the transmission rod, and a reflection compression wave formed by reflection of the transmission rod flange is absorbed by the transmission wave-catching sleeve, so that the compression of the transmission rod to the sample is avoided.
3. 3. The split Hopkinson tie bar apparatus for achieving single pulse loading of claim 2 wherein the stress wave generating unit comprises an impingement tube coaxially sleeved outside the incident beam, the impingement tube being configured to generate the compression stress wave by impingement of the incident beam flange.
4. 4. The split Hopkinson pull rod device for realizing single pulse loading according to claim 2 or 3, wherein an incidence rod strain gauge is arranged at the axial middle position of the incidence rod, and a transmission rod strain gauge is arranged at the transmission rod near the sample end.
5. 5. The split Hopkinson drawbar apparatus for achieving single pulse loading according to claim 4, wherein the incident beam strain gage is a resistive strain gage and the transmission beam strain gage is a semiconductor strain gage.
6. 6. The separated Hopkinson pull rod device for realizing single pulse loading according to claim 2 is characterized in that a threaded hole or a radial through groove is formed in a sample loading end of the incidence rod and a sample loading end of the transmission rod respectively, the threaded hole is used for forming detachable and fixed connection with a threaded end of a cylindrical sample, the radial through groove divides the end part of a rod piece into a first compression part and a second compression part, coaxial round holes and threaded holes are formed in the first compression part and the second compression part to form screw mounting holes, two ends of a lath sample are respectively inserted into the radial through grooves of the rod piece and then are locked through a variable cross section connecting screw, and friction force and mechanical occlusion between the rod piece and the lath sample are enhanced by utilizing the compression effect of the through groove and the extrusion effect of the variable cross section part, so that relative sliding is effectively inhibited.
7. 7. The separated Hopkinson pull rod device for realizing single pulse loading according to claim 3, wherein the density and the elastic modulus of the incident wave-catching sleeve, the absorption rod flange, the incident rod flange, the impact tube and the transmission rod are the same.
8. 8. A single pulse loading method, characterized by using the pull rod assembly of claim 1, comprising the steps of: s1, accessing a strain measurement system through an incident rod strain gauge and a transmission rod strain gauge; S2, coaxially connecting a sample between the incident rod and the transmission rod; s3, driving the impact pipe to impact the flange of the incident rod to generate compression stress waves; s4, absorbing the reflected compression waves on the incident rod through the incident wave-capturing unit to realize single pulse loading; the implementation of the single pulse loading comprises: The compression stress wave propagates along the incident rod flange, and forms 2 stress waves after reaching the flange terminal, wherein one compression stress wave reaches the incident rod flange terminal and is reflected to form a tensile stress wave which is transmitted along the incident rod and loads a sample; The compression stress wave transmitted along the incident wave-capturing sleeve reaches the flange of the absorption rod and is transmitted along the flange, after reaching the terminal end of the flange, the compression stress wave is reflected to form a tensile stress wave to be transmitted along the absorption rod, and the absorption rod flange and the absorption rod are separated from the incident wave-capturing sleeve together with the absorption rod, so that the transmission of the subsequent stress wave is blocked; When the tensile stress wave transmitted along the incident rod reaches the connection position of the incident rod and the sample, due to the change of the interface, a part of the tensile stress wave reaches the interface to form a reflected compression wave to return to the incident rod, and a part of the tensile stress wave is transmitted along the sample to load the sample, the reflected compression wave is transmitted to the incident wave-catching sleeve after reversely transmitted along the incident rod to reach the flange terminal of the incident rod, and is reflected by the free end of the incident wave-catching sleeve to form the tensile stress wave, and due to the action of the tensile stress wave, the incident wave-catching sleeve is separated from contact with the flange of the incident rod, the transmission of the subsequent stress wave to the incident rod is blocked, so that the sample is only subjected to the action of one-time tensile wave, and the sample is subjected to single pulse loading.
9. 9. The loading method of claim 8, wherein the strain measurement system adopts a Wheatstone bridge structure, the incident rod strain gauge and the transmission rod strain gauge are respectively connected into a Wheatstone bridge box, and then output ports of the Wheatstone bridge box are sequentially and electrically connected with the strain amplifier, the digital oscilloscope and the computer.

Description

Separated Hopkinson pull rod device and method for realizing single pulse loading Technical Field The invention relates to the technical field of dynamic mechanical property testing of materials, in particular to a separated Hopkinson pull rod device and method for realizing single pulse loading. Background In the field of testing the high strain rate dynamic tensile mechanical properties of materials, the separation type Hopkinson pull rod (SHTB) technology is a core means for researching the dynamic response of the materials. The traditional SHTB device can reflect back and forth between the incident rod and the transmission rod for many times to form a multi-pulse loading effect through the tensile stress wave generated by the impact of the bullet on the incident rod, and the multi-pulse loading effect can bring great influence to the data precision of the experiment. For example, although the Hopkinson pull rod fatigue test device mentioned in the literature can realize high-frequency loading, the pneumatic system is required to recycle bullets and inhibit reflected waves, and the insufficient absorption efficiency can cause the residual wave energy to be not completely dissipated, so that the secondary or even multiple loading of the sample is caused, and serious deviation of data precision is caused. In the aspect of researching strain induced martensite of a material under a high strain rate, the multi-pulse loading phenomenon existing in the device not only influences the accurate control of the strain quantity of the material, but also makes the corresponding relation between the strain of a test piece and the strain induced phase transformation content difficult to establish, and the difference work of researching the phase transformation content under different strain rates is difficult to develop. In order to solve the problem of the multi-pulse loading effect, the technology of single-momentum trap or double-momentum trap separation type pull rod device is mostly adopted in the field at present, such as a single-momentum trap separation type pull rod device adopted in the patent of the invention (the name of the invention: single-pulse separation type Hopkinson pull rod experimental device based on electromagnetic force loading, the authorized bulletin number is CN 113607545B), but the dynamic passive attaching mode of the absorption rod cannot ensure complete absorption of reflected waves in an incident rod, and generally faces the problem of multiple pulse loading interference in practical application. The existing solution also has the advantages that the deformation of the sample is limited by designing a rigid clamp with a specific size, and the aim of controlling the strain of the sample is achieved although the device is not improved, but the method cannot accurately obtain the stress-strain curve of the sample due to the interference of the clamp, and the use of digital image related technical equipment such as an external high-speed camera or an infrared camera is limited. In summary, the existing improvement technology still has the defects of multi-pulse amplitude residue, accurate control and effective recovery of sample strain and material suitability, and an innovative method for realizing single-pulse loading by a split Hopkinson pull rod device is needed. Disclosure of Invention In view of the above-described shortcomings of the prior art, the present invention provides a split Hopkinson drawbar apparatus that achieves single pulse loading. The separated Hopkinson pull rod device for realizing single pulse loading is characterized by comprising an incidence rod, an incidence wave capturing unit and a stress wave generating unit; One end of the incidence rod is connected with the incidence rod flange, and the other end of the incidence rod is used for holding a sample; The incident wave-capturing unit comprises an incident wave-capturing sleeve and an absorption rod, one end of the absorption rod is opposite to the incident rod flange at a certain interval, the other end of the absorption rod is connected with the absorption rod flange, the incident wave-capturing sleeve is sleeved outside the absorption rod, and two ends of the incident wave-capturing sleeve are respectively attached to the absorption rod flange and the incident rod flange; the stress wave generating unit is arranged at one end of the incident rod, which is close to the flange of the incident rod, and is used for forming compression stress waves; The compression stress wave propagates along the flange of the incidence rod, and forms 2 stress waves after reaching the flange terminal, wherein one compression stress wave reaches the flange terminal of the incidence rod and is reflected to form a tensile stress wave which is transmitted along the incidence rod and loads a sample; The compression stress wave transmitted along the incident wave-capturing sleeve reaches the flange of the absorption rod and is transmitt