Electromagnetic Hopkinson pull rod system for realizing square stress wave loading
By introducing a waveform shaping structure and threaded connection into the electromagnetic Hopkinson rod system, the problem that the traditional Hopkinson rod cannot generate square stress waves and accurately control the stress wave time is solved, and constant strain rate loading and convenient maintenance of system components are achieved.
Patent Information
- Application Number
- CN202411555741.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-04
- Publication Date
- 2025-10-17
AI Technical Summary
Traditional electromagnetic Hopkinson bars cannot generate square stress waves, making it difficult to achieve constant strain rate loading of metal specimens, and traditional pneumatic Hopkinson bars cannot accurately control the time when stress waves occur.
An electromagnetic Hopkinson rod system was designed, which includes an electromagnetic force generating system, a force transmission shaft, a force transmission cylinder, a waveform shaping structure and an incident rod. The waveform shaping structure is made of an approximately ideal elastic-plastic material such as honeycomb or foam, and the stress waveform is controlled to be square. Combined with threaded connection, it is easy to disassemble and replace parts.
The loading of square stress waves is realized, which ensures the constant value output of stress waves, facilitates the replacement and maintenance of system components, and improves the loading accuracy and adaptability.
Smart Images
Figure CN120801427A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of dynamic mechanical property testing, in particular to an electromagnetic Hopkinson tension rod system for realizing square stress wave loading. BACKGROUND
[0002] Split Hopkinson bar experiment technology is widely used in dynamic mechanical property testing of materials and structures, and the strain rate range is 102-104s-1. In the experiment technology, a sample is clamped between an incident rod and a transmission rod, a strain signal in the rod is measured through a strain gauge attached to a position far from the sample, and stress, strain and strain rate curves of the measured material are obtained through one-dimensional stress wave propagation theory and a uniform deformation assumption of the sample.
[0003] A traditional pneumatic Hopkinson bar is easily to produce square stress wave through impact of a bullet with the same cross section as the material, but cannot accurately control the time of stress wave generation, so that multi-axial simultaneous loading cannot be realized. An electromagnetic Hopkinson bar can accurately control the time of stress wave generation, but the generated wave is generally a half-sine wave, the wave shape cannot be controlled, and it is difficult to generate a square wave, so that constant strain rate loading on the sample, especially a metal sample, is difficult to realize. SUMMARY
[0004] In view of the deficiencies of the prior art, the present application provides an electromagnetic Hopkinson tension rod system for realizing square stress wave loading, which can avoid the shortcoming that only a half-sine wave can be used to load the sample in a traditional electromagnetic Hopkinson tension rod, and realize similar square incident wave as a traditional pneumatic Hopkinson tension rod.
[0005] To achieve the above object, the present application is implemented by the following technical scheme: an electromagnetic Hopkinson tension rod system for realizing square stress wave loading, comprising an electromagnetic force generating system, the electromagnetic force generating system is connected with a force transmission shaft, the other side of the force transmission shaft is connected with a stress wave control system, the stress wave control system comprises a force transmission cylinder, a wave shaping structure, an incident rod protrusion, one side of the force transmission cylinder is threadedly connected with the force transmission shaft, the other side of the force transmission cylinder is connected with an incident rod, the surface of the incident rod is installed with a strain gauge, the other side of the incident rod away from the force transmission cylinder end is installed with a transmission rod, the inner side of the force transmission cylinder is installed with the wave shaping structure, the incident rod protrusion is threadedly connected with the incident rod, the adjacent ends of the incident rod and the transmission rod are installed with a sample.
[0006] Preferably, the force transmission cylinder is provided with an opening in the center for the incident rod to pass through, and the force transmission cylinder is provided with a thread near the end of the force transmission shaft.
[0007] Preferably, the wave shaping structure is located between the force transmission cylinder and the incident rod protrusion, and the force transmission cylinder and the incident rod protrusion clamp the wave shaping structure.
[0008] Preferably, the stress wave generating end of the electromagnetic force generating system is close to the inside of the force transmission shaft, and the wave shaping structure is composed of an approximately ideal elastic-plastic material or a material such as honeycomb or foam.
[0009] Preferably, the anvil head is conical frustum-shaped and is threadedly connected to the left side of the electromagnetic force generating system.
[0010] Preferably, support frames are installed on the outside of the incident rod and the transmission rod, and mounting grooves are arranged on the lower side edges of the support frames.
[0011] Preferably, auxiliary support frames are installed on the outside of the electromagnetic force generating system and the force transmission cylinder.
[0012] Preferably, an energy absorption device is connected to the end of the electromagnetic force generating system away from the force transmission shaft.
[0013] Beneficial effects
[0014] The application provides an electromagnetic Hopkinson rod system for square stress wave loading.
[0015] (1) The electromagnetic Hopkinson rod system for square stress wave loading controls the force passing through the wave shaping system to be approximately constant by setting a wave shaping structure in the system, so as to achieve the purpose of controlling the output desired wave shape.
[0016] (2) The electromagnetic Hopkinson rod system for square stress wave loading sets a threaded connection structure in the system, which facilitates users to disassemble the force transmission shaft, the force transmission cylinder and other structures, and further facilitates users to replace the corresponding components in the system according to the needs. BRIEF DESCRIPTION OF DRAWINGS
[0017] Figure 1 It is a perspective view of the application;
[0018] Figure 2 It is a sectional perspective view of the application;
[0019] Figure 3 It is a partial enlarged view of A in the application; Figure 2
[0020] Figure 4 It is a typical stress wave curve of the electromagnetic Hopkinson rod before shaping in the application;
[0021] Figure 5 It is a typical stress wave curve of the electromagnetic Hopkinson rod after shaping in the application.
[0022] In the figure: 1, electromagnetic force generating system; 2, force transmission shaft; 3, force transmission cylinder; 4, incident rod; 5, strain gauge; 6, sample; 7, transmission rod; 8, wave shaping structure; 9, incident rod protrusion. DETAILED DESCRIPTION
[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.
[0024] As Figures 1-5 shown in the first embodiment: a square stress wave loading electromagnetic Hopkinson rod system, comprising an electromagnetic force generating system 1, the electromagnetic force generating system 1 is connected with a force transmission shaft 2, the electromagnetic force generating system 1 is connected with an energy absorption device away from the force transmission shaft 2 end; the force transmission shaft 2 is connected with a stress wave control system on the other side, the stress wave control system comprises a force transmission cylinder 3, a wave shaping structure 8, an incident rod protrusion 9, one side of the force transmission cylinder 3 is threadedly connected with the force transmission shaft 2, the other side of the force transmission cylinder 3 is connected with an incident rod 4, the surface of the incident rod 4 is installed with a strain gauge 5, the other side of the incident rod 4 is installed with a transmission rod 7 away from the force transmission cylinder 3 end, the inside of the force transmission cylinder 3 is installed with the wave shaping structure 8, the incident rod protrusion 9 is threadedly connected with the incident rod 4, the adjacent ends of the incident rod 4 and the transmission rod 7 are installed with a sample 6;
[0025] The force transmission cylinder 3 is provided with an opening in the center for the incident rod 4 to pass through, and the force transmission cylinder 3 is provided with threads near the force transmission shaft 2 end; the wave shaping structure 8 is located between the force transmission cylinder 3 and the incident rod protrusion 9, and the force transmission cylinder 3 and the incident rod protrusion 9 clamp the wave shaping structure 8; the selection criteria of the wave shaping structure 8: the stress-strain curve shows ideal elastic-plasticity, weak strain hardening ability and weak strain rate effect; typical materials of the wave shaping structure 8: aluminum foam, metal honeycomb, and some aluminum alloys;
[0026] Size calculation of shaping material: ignoring the elastic deformation of the material, the strength thereof is σ s , the cross-sectional area of the waveguide rod is A b , the required stress wave platform strength is σ b , the cross-sectional area of the shaping material is A s , and then the following should be met:
[0027]
[0028] According to the strength of the shaping material, the required cross-sectional area A s can be calculated. Of course, the selection range of A s also needs to be met, and appropriate materials are selected, such as the obtained A sIf the size is too large, a higher strength plastic material needs to be selected.
[0029] In addition, the thickness of the plastic material is designed according to the following principle: the energy exceeding the required stress platform needs to be absorbed by the plastic material during the entire stress pulse time, and the stress generated in the process meets the fluctuation range of the platform stress. For example, aluminum foam and honeycomb absorb excess energy during deformation, but if the energy is too large, they will be compacted, resulting in a significant increase in stress and loss of plastic ability; therefore, a plastic material with sufficient thickness is required to ensure that it is not compacted. The calculation formula is as follows:
[0030]
[0031] Where ε is the cutoff strain of the plastic material to maintain the lateral stress state, i.e. beyond this strain, the strength of the plastic material changes more than the fluctuation range required by the stress platform. d is the initial stress intensity σ I generated by the electromagnetic generator in the rod, and the platform stress σ b is related, and the calculation method is as follows:
[0032] According to the stress wave propagation principle, the compression speed of the plastic material is approximately:
[0033]
[0034] ρc0 is the wave impedance of the rod, which is the product of the density of the rod and the longitudinal wave speed.
[0035] The integral can obtain the compression thickness of the plastic material:
[0036]
[0037] That is, twice the difference between the stress wave in the unshaped rod and the stress wave after shaping around the time axis, divided by the wave impedance. The stress wave generation end in the electromagnetic force generation system 1 is close to the inside of the force transmission shaft 2, and the wave shaping structure 8 is made of an approximately ideal elastic-plastic material or structure, such as honeycomb, foam, etc. ; Because the plastic section of the wave shaping structure 8 is a platform on the stress-strain curve, the force transmitted through the wave shaping system is approximately constant;
[0038] As shown in the second embodiment shown in Figures 1-3 , the main difference from the first embodiment is:
[0039] The anvil head is conical frustum in shape and is threadedly connected to the force transmission shaft 2 near the left side of the electromagnetic force generating system 1. The support frames are installed on the outer sides of the incident rod 4 and the transmission rod 7, and the installation grooves are arranged on the lower edges of the support frames. The auxiliary support frames are installed on the outer sides of the electromagnetic force generating system 1 and the force transmission cylinder 3. One end of the force transmission cylinder 3 is fixedly connected to the force transmission shaft 2 by screwing, and the other end is provided with a hole in the center of the end face so that the incident rod 4 can pass through the hole. This arrangement facilitates the user to disassemble and replace the force transmission shaft 2, the force transmission cylinder 3, the incident rod 4, the wave shaping structure 8 and the incident rod protrusion 9, and improves the adaptability and precision of the system.
[0040] Meanwhile, the contents not described in detail in the specification are all the prior art known to those skilled in the art, and the model parameters of the various appliances are not specifically limited, and conventional equipment can be used.
[0041] In use, the stress wave generated by the electromagnetic force generating system 1 is transmitted to the incident rod 4 through the force transmission shaft 2, the force transmission cylinder 3, the wave shaping structure 8 and the incident rod protrusion 9, and the strain gauge 5 loads the sample 6. Since the wave shaping structure 8 is a structure similar to an ideal elastic-plastic material or a structure similar to a material such as honeycomb or foam, the plastic shaping section of the stress-strain curve is flat, so that the force transmitted through the wave shaping system is approximately constant, thereby achieving the purpose of controlling the output desired wave shape.
[0042] It should be noted that, in the present document, the terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or equipment.
[0043] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.
Claims
1. An electromagnetic Hopkinson rod system for realizing square stress wave loading, comprising an electromagnetic force generating system (1), characterized in that: The electromagnetic force generating system (1) is connected to a force transmission shaft (2), and the other side of the force transmission shaft (2) is connected to a stress wave control system, and the stress wave control system comprises a force transmission cylinder (3), a waveform shaping structure (8), and an incident rod protrusion (9). One side of the force transmission cylinder (3) is threadedly connected to the force transmission shaft (2), and the other side of the force transmission cylinder (3) is connected to an incident rod (4). A strain gauge (5) is installed on the surface of the incident rod (4), and a transmission rod (7) is installed on the other side of the incident rod (4) away from the end of the force transmission cylinder (3). The waveform shaping structure (8) is installed on the inner side of the force transmission cylinder (3), and the incident rod protrusion (9) is threadedly connected to the incident rod (4). A sample (6) is installed at the adjacent ends of the incident rod (4) and the transmission rod (7).
2. The electromagnetic Hopkinson rod system for realizing square stress wave loading according to claim 1, characterized in that: The center of the force transmission cylinder (3) is provided with an opening for the incident rod (4) to pass through, and the end of the force transmission cylinder (3) close to the force transmission shaft (2) is provided with a thread.
3. The electromagnetic Hopkinson rod system for realizing square stress wave loading according to claim 1, characterized in that: The waveform shaping structure (8) is located between the force transmission cylinder (3) and the incident rod convex head (9), and the force transmission cylinder (3) and the incident rod convex head (9) clamp the waveform shaping structure (8).
4. The electromagnetic Hopkinson rod system for realizing square stress wave loading according to claim 1, characterized in that: The stress wave generating end in the electromagnetic force generating system (1) is close to the inside of the force transmission shaft (2), and the waveform shaping structure (8) is made of an elastic-plastic material.
5. The electromagnetic Hopkinson rod system for realizing square stress wave loading according to claim 1, characterized in that: The force transmission shaft (2) is threadedly connected to an anvil head on the left side close to the electromagnetic force generating system (1), and the anvil head is in the shape of a frustum.
6. The electromagnetic Hopkinson rod system for realizing square stress wave loading according to claim 1, characterized in that: Support frames are installed on the outsides of the incident rod (4) and the transmission rod (7), and mounting grooves are provided on the lower edges of the support frames.
7. The electromagnetic Hopkinson rod system for realizing square stress wave loading according to claim 1, characterized in that: Auxiliary support frames are installed on the outsides of the electromagnetic force generating system (1) and the force transmission cylinder (3).
8. The electromagnetic Hopkinson rod system for realizing square stress wave loading according to claim 1, characterized in that: The electromagnetic force generating system (1) is connected to an energy absorbing device at the end away from the force transmission shaft (2).