Electromagnetic Hopkinson pressure bar system for square stress wave loading

Abstract

The invention discloses a square stress wave loaded electromagnetic Hopkinson pressure bar system, which comprises an electromagnetic force generation system, and relates to the technical field of dynamic mechanical property testing of materials. According to the square stress wave loaded electromagnetic Hopkinson pressure bar system, half-sine waves can be shaped through the arranged waveform shaping material or structure, and approximate square waves are generated in the incident bar body through the electromagnetic force generation system; stress waves generated by the electromagnetic force generation system can be output to the incident bar body only through the stress wave regulation and control system, and a waveform shaping material or structure which keeps the strength constant in the large deformation process is selected, so that the stress waves with the strength exceeding the set strength of the device are absorbed through large deformation; according to the Hopkinson pressure bar disclosed by the utility model, the square wave is transmitted in the incident bar body, and then a sample is loaded, so that the defect that the sample can only be loaded by using a half-sine wave in a traditional electromagnetic Hopkinson pressure bar is overcome, and a square incident wave similar to that of a traditional pneumatic Hopkinson pressure bar is realized.

Description

Technical Field

[0001] The invention relates to the technical field of dynamic mechanical property testing of materials, in particular to an electromagnetic Hopkinson pressure bar system loaded with square stress waves. Background Art

[0002] The split Hopkinson bar experimental technique is widely used in dynamic mechanical property testing of materials and structures, with a strain rate range of 102 to 104 s-1. This experimental technique sandwiches the sample between the incident bar and the transmission bar, measures the strain signal in the bar through a strain gauge pasted far away from the sample, and obtains the stress, strain and strain rate curves of the measured material through the one-dimensional stress wave propagation theory and the uniform deformation assumption of the sample.

[0003] The existing electromagnetic Hopkinson bar system for square stress wave loading still has the following problems: the traditional pneumatic Hopkinson bar can easily generate square stress waves through the impact of bullets of equal cross-section and the same material, but the time of stress wave generation cannot be accurately controlled, so that multi-axis simultaneous loading cannot be achieved; the electromagnetic Hopkinson bar can accurately control the time of stress wave generation, but the waveform it generates is generally a half-sine wave, and the waveform cannot be controlled, so it is difficult to achieve constant strain rate loading of the tested sample, especially metal samples. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides an electromagnetic Hopkinson pressure bar system loaded with a square stress wave, which solves the problem that the waveform generated by the electromagnetic Hopkinson bar of the existing electromagnetic Hopkinson pressure bar system loaded with a square stress wave is generally a half-sine wave, and the waveform cannot be controlled, making it difficult to achieve constant strain rate loading on the tested samples, especially metal samples.

[0005] To achieve the above objectives, the present invention is implemented by the following technical solutions: an electromagnetic Hopkinson pressure bar system loaded with square stress waves, including an electromagnetic force generating system, an electromagnetic Hopkinson pressure bar system body is arranged on the left side of the electromagnetic force generating system for performance testing, and the electromagnetic Hopkinson pressure bar system body includes:

[0006] A test assembly, arranged on the right side of the electromagnetic force generating system for testing, the test assembly comprising a force transmission shaft body fixedly installed on the right side of the electromagnetic force generating system;

[0007] A stress wave control system is arranged at the right end of the force transmission shaft body for shaping the semi-sine wave. The stress wave control system includes a force transmission shaft boss threadedly installed at the right end of the force transmission shaft body, a waveform shaping material or structure is movably installed on the right side of the force transmission shaft boss, and an incident rod boss is movably installed on the right side of the waveform shaping material or structure.

[0008] Preferably, both sides of the force transmission shaft boss and the incident rod boss are tightly attached to the left and right sides of the corrugated shaping material or structure.

[0009] Preferably, the test assembly also includes an incident rod body threadedly mounted on the right side of the incident rod protrusion, a first strain gauge is bonded to the outer side of the incident rod body, a sample is movably mounted on the right end of the incident rod body, a transmission rod is movably mounted on the right side of the sample, and a second strain gauge is bonded to the outer side of the transmission rod.

[0010] Preferably, the left and right sides of the sample are both in close contact with the opposite sides of the incident rod body and the transmission rod.

[0011] Preferably, the support assembly comprises a guide ring movably mounted on the outer sides of the force transmission shaft boss and the incident rod boss, and a support member is fixedly mounted on the outer side of the guide ring.

[0012] Preferably, the inner side of the guide ring is in close contact with the outer sides of the force transmission shaft boss and the incident rod boss.

[0013] Preferably, the support assembly also includes two first support frames movably mounted on the outside of the incident rod body, and the front sides of the two first support frames are both threadedly mounted with first screws, and the outer sides of the transmission rod are movably mounted with two second support frames, and the front sides of the two second support frames are both threadedly mounted with second screws.

[0014] Preferably, the rear ends of the first screws are threaded through the front sides of the two first support frames and are closely attached to the outer side of the incident rod body, and the rear ends of the second screws are threaded through the front sides of the two second support frames and are closely attached to the outer side of the transmission rod.

[0015] Beneficial Effects

[0016] The present invention provides an electromagnetic Hopkinson pressure bar system loaded with square stress waves. Compared with the prior art, it has the following beneficial effects:

[0017] 1. The electromagnetic Hopkinson bar system loaded with square stress waves can shape the half-sine wave by setting a waveform shaping material or structure, and generate an approximate square wave in the incident bar body through the electromagnetic force generating system, thereby making it possible to load the sample at a constant strain rate. The stress wave generated by the electromagnetic force generating system needs to be output to the incident bar body through the stress wave control system. A waveform shaping material or structure that maintains constant strength during large deformation is selected, so that the stress wave exceeding the strength set by the device is eliminated through large deformation, thereby propagating an approximate square wave in the incident bar body, and then loading the sample, avoiding the disadvantage that only half-sine waves can be used to load the sample in the traditional electromagnetic Hopkinson bar, and realizing a square incident wave similar to the traditional pneumatic Hopkinson bar.

[0018] 2. The electromagnetic Hopkinson pressure bar system loaded with square stress waves can improve the stability of the device by setting a guide ring, a first support frame and a second support frame. During installation, the first screw is rotated to fix the position of the incident rod body through the first support frame, and then the transmission rod is placed on the inner side of the second support frame. Then, the sample is placed between the incident rod body and the transmission rod. At this time, the first screw is rotated to fix the position of the incident rod body and the sample through the two first support frames, thereby improving the stability and accuracy of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the plane appearance of the present invention;

[0020] Figure 2 It is a schematic diagram of the plane appearance of the test assembly of the present invention;

[0021] Figure 3 It is a schematic diagram of the planar appearance of the support assembly of the present invention;

[0022] Figure 4 It is a schematic diagram of a typical curve of electromagnetic Hopkinson bar stress wave before shaping of the present invention;

[0023] Figure 5 It is a schematic diagram of the stress wave curve obtained after shaping of the present invention.

[0024] In the figure: 1-electromagnetic force generating system, 2-electromagnetic Hopkinson pressure bar system body, 21-test assembly, 211-force transmission shaft body, 212-incident rod body, 213-first strain gauge, 214-sample, 215-second strain gauge, 216-transmission rod, 22-stress wave regulation system, 221-force transmission shaft boss, 222-wave-shaping material or structure, 223-incident rod boss, 23-support assembly, 231-support member, 232-guide ring, 233-first support frame, 234-first screw, 235-second support frame, 236-second screw. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention provides two technical solutions:

[0027] Figure 1-Figure 5The first embodiment is shown: the electromagnetic Hopkinson pressure bar system loaded with square stress wave includes an electromagnetic force generating system 1, and an electromagnetic Hopkinson pressure bar system body 2 is arranged on the left side of the electromagnetic force generating system 1 for performance testing. The electromagnetic Hopkinson pressure bar system body 2 includes:

[0028] A test assembly 21 is arranged on the right side of the electromagnetic force generating system 1 for testing, and the test assembly 21 includes a force transmission shaft body 211 fixedly installed on the right side of the electromagnetic force generating system 1;

[0029] The stress wave control system 22 is arranged at the right end of the force transmission shaft body 211 for shaping the half-sine wave. The stress wave control system 22 includes a force transmission shaft boss 221 threadedly installed at the right end of the force transmission shaft body 211. A waveform shaping material or structure 222 is movably installed on the right side of the force transmission shaft boss 221. An incident rod boss 223 is movably installed on the right side of the waveform shaping material or structure 222. Both sides of the force transmission shaft boss 221 and the incident rod boss 223 are tightly attached to the left and right sides of the waveform shaping material or structure 222, and can be fixed by the incident rod boss 223 and the force transmission shaft boss 221. The position of the waveform shaping material or structure 222 is clamped. The waveform shaping material or structure 222 is a material that is approximately an ideal elastic-plastic material or a shaping segment on a stress-strain curve such as a honeycomb or foam, so as to control the force passing through the waveform shaping system to be approximately constant. Other waveform shaping materials or structures 222 can also be selected according to needs to achieve the purpose of controlling the output of the desired waveform. The selection criteria of the waveform shaping material or structure 222 should consider that the stress-strain curve is ideal elastic-plastic, weak strain hardening ability, and weak strain rate effect. The shaping material size calculation: Ignore the elastic deformation of the material, and its strength is σ s , the cross-sectional area of ​​the waveguide rod is A b , the required stress wave platform strength σ b , cross-sectional area A of the corrugated material or structure 222 s , then it should satisfy:

[0030]

[0031] According to the strength of the wave-shaped material or structure 222, the required cross-sectional area A can be calculated. s Of course, A s The selection range is to select a suitable waveform shaping material or structure 222, such as the obtained A s If the size is too large, it is necessary to select a stronger corrugated shaping material or structure 222.

[0032] In addition, the thickness design criteria of the corrugated shaping material or structure 222 are: during the entire stress pulse time, the energy exceeding the required stress platform needs to be absorbed by the corrugated shaping material or structure 222, and the stress generated in this process meets the fluctuation range of the platform stress. For example, foam aluminum and honeycomb absorb excess energy during deformation, but if the energy is too large, it will be compacted, resulting in a significant increase in stress; therefore, a corrugated shaping material or structure 222 of sufficient thickness is required to ensure that it is not compacted. The calculation formula is as follows:

[0033]

[0034] Wherein, ε is the cut-off strain for the waveform shaping material or structure 222 to maintain the transverse stress state, that is, beyond this strain, the strength change of the waveform shaping material or structure 222 exceeds the fluctuation range that the stress platform needs to satisfy. d is related to the initial stress intensity σ generated in the rod by the electromagnetic force generating system 1 i and platform stress σ b The calculation method is as follows:

[0035] According to the stress wave propagation principle, the compression speed of the wave-shaped material or structure 222 is approximately:

[0036]

[0037] ρc0 is the wave impedance of the rod, and is the product of the rod density and the longitudinal wave velocity.

[0038] The compressed thickness of the corrugated shaping material or structure 222 can be obtained by integration:

[0039]

[0040] That is, twice the difference in area between the stress wave in the unshaped rod and the stress wave after shaping around the time axis divided by the wave impedance. The test assembly 21 also includes an incident rod body 212 threadedly mounted on the right side of the incident rod boss 223, a first strain gauge 213 is bonded to the outer side of the incident rod body 212, a sample 214 is movably mounted on the right end of the incident rod body 212, a transmission rod 216 is movably mounted on the right side of the sample 214, a second strain gauge 215 is bonded to the outer side of the transmission rod 216, and the left and right sides of the sample 214 are tightly attached to the opposite sides of the incident rod body 212 and the transmission rod 216, and the waveform shaping material or structure 222 is an approximately ideal elastic-plastic material or a platform on the stress-strain curve such as honeycomb, foam, etc., so as to control the force passing through the waveform shaping system to be approximately constant. Other waveform shaping materials or structures 222 can also be selected according to needs to achieve the purpose of controlling the output of a desired waveform.

[0041] The half-sine wave can be shaped by the waveform shaping material or structure 222, and an approximate square wave is generated in the incident rod body 212 through the electromagnetic force generating system 1, thereby making it possible to load the sample 214 at a constant strain rate. The stress wave generated by the electromagnetic force generating system 1 needs to pass through the stress wave control system 22 before it can be output to the incident rod body 212. A waveform shaping material or structure 222 that maintains constant strength during large deformation is selected, so that stress waves exceeding the strength set by the device are eliminated through large deformation, thereby propagating an approximate square wave in the incident rod body 212, and then loading the sample 214, thereby avoiding the disadvantage of the traditional electromagnetic Hopkinson tension rod that only a half-sine wave can be used to load the sample 214, and realizing a square incident wave similar to the traditional pneumatic Hopkinson compression rod.

[0042] Figure 1-Figure 3 A second embodiment is shown, which is mainly different from the first embodiment in that: the support assembly 23 includes a guide ring 232 movably mounted on the outside of the force transmission shaft boss 221 and the incident rod boss 223, the outside of the guide ring 232 is fixedly mounted with a support member 231, the inner side of the guide ring 232 is tightly attached to the outside of the force transmission shaft boss 221 and the incident rod boss 223, and the positions of the force transmission shaft boss 221 and the incident rod boss 223 can be limited by the two guide rings 232, the support assembly 23 also includes two first support frames 233 movably mounted on the outside of the incident rod body 212, and the front sides of the two first support frames 233 are both threadedly mounted with first screws 2 34. Two second support frames 235 are movably installed on the outer side of the transmission rod 216. The front sides of the two second support frames 235 are threadedly installed with second screws 236. The rear ends of the first screws 234 are threadedly penetrated through the front sides of the two first support frames 233 and are tightly attached to the outer side of the incident rod body 212. The first screws 234 can be rotated to fix the position of the incident rod body 212 through the two first support frames 233. The rear ends of the second screws 236 are threadedly penetrated through the front sides of the two second support frames 235 and are tightly attached to the outer side of the transmission rod 216. The second screws 236 can be rotated to fix the position of the transmission rod 216 through the two second support frames 235.

[0043] The stability of the device can be improved by setting the guide ring 232, the first support frame 233 and the second support frame 235. During installation, the first screw rod 234 is rotated to fix the position of the incident rod body 212 through the first support frame 233, and then the transmission rod 216 is placed on the inner side of the second support frame 235. Then, the sample 214 is placed between the incident rod body 212 and the transmission rod 216. At this time, the first screw rod 234 is rotated to fix the position of the incident rod body 212 and the sample 214 through the two first support frames 233, thereby improving the stability and accuracy of the device.

[0044] Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0045] When in use, the electromagnetic force generating system 1 and the supporting assembly 23 are installed in a suitable position, and then the first screw rod 234 is rotated to fix the position of the incident rod body 212 through the first supporting frame 233, and then the transmission rod 216 is placed on the inner side of the second supporting frame 235, and then the sample 214 is placed between the incident rod body 212 and the transmission rod 216. At this time, the first screw rod 234 is rotated to fix the positions of the incident rod body 212 and the sample 214 through the two first supporting frames 233, and then the corrugated shaping material or structure 222 is placed between the force transmission shaft convex head 221 and the incident rod convex head 223, and then the incident rod convex head 223 is rotated to clamp the corrugated shaping material or structure 22 2, and then the electromagnetic force generating system 1 is turned on to generate an approximate square wave in the incident rod body 212, and the stress wave generated by the electromagnetic force generating system 1 needs to pass through the stress wave control system 22 before it can be output to the incident rod body 212, and a waveform shaping material or structure 222 that maintains constant strength during large deformation is selected, so that the stress wave exceeding the strength set by the device is eliminated through large deformation, thereby propagating an approximate square wave in the incident rod body 212, and then loading the sample 214, avoiding the disadvantage of the traditional electromagnetic Hopkinson tension rod that only half-sine waves can be used to load the sample 214, and realizing a square incident wave similar to the traditional pneumatic Hopkinson compression rod.

[0046] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0047] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An electromagnetic Hopkinson bar system loaded with square stress waves, comprising an electromagnetic force generating system (1), characterized in that: An electromagnetic Hopkinson pressure bar system body (2) is arranged on the left side of the electromagnetic force generating system (1) for performance testing. The electromagnetic Hopkinson pressure bar system body (2) comprises: A test assembly (21) is arranged on the right side of the electromagnetic force generating system (1) for testing, and the test assembly (21) comprises a force transmission shaft body (211) fixedly mounted on the right side of the electromagnetic force generating system (1); A stress wave control system (22) is arranged at the right end of the force transmission shaft body (211) and is used for shaping the half-sine wave. The stress wave control system (22) comprises a force transmission shaft boss (221) threadedly mounted on the right end of the force transmission shaft body (211), a waveform shaping material or structure (222) is movably mounted on the right side of the force transmission shaft boss (221), and an incident rod boss (223) is movably mounted on the right side of the waveform shaping material or structure (222); The support assembly (23) is arranged on the outer side of the force transmission shaft boss (221) to improve the stability of the device.

2. The electromagnetic Hopkinson bar system with square stress wave loading according to claim 1, characterized in that: Both sides of the force transmission shaft convex head (221) and the incident rod convex head (223) are closely attached to the left and right sides of the wave-shaped shaping material or structure (222).

3. The electromagnetic Hopkinson bar system with square stress wave loading according to claim 1, characterized in that: The test assembly (21) further comprises an incident rod body (212) threadedly mounted on the right side of the incident rod boss (223); a first strain gauge (213) is bonded to the outer side of the incident rod body (212); a sample (214) is movably mounted on the right end of the incident rod body (212); a transmission rod (216) is movably mounted on the right side of the sample (214); and a second strain gauge (215) is bonded to the outer side of the transmission rod (216).

4. The electromagnetic Hopkinson bar system with square stress wave loading according to claim 3, characterized in that: The left and right sides of the sample (214) are both closely attached to the opposite sides of the incident rod body (212) and the transmission rod (216).

5. The electromagnetic Hopkinson bar system with square stress wave loading according to claim 1, characterized in that: The support assembly (23) comprises a guide ring (232) movably mounted on the outside of the force transmission shaft boss (221) and the incident rod boss (223), and a support member (231) is fixedly mounted on the outside of the guide ring (232).

6. The electromagnetic Hopkinson bar system with square stress wave loading according to claim 5, characterized in that: The inner side of the guide ring (232) is tightly attached to the outer sides of the force transmission shaft convex head (221) and the incident rod convex head (223).

7. The electromagnetic Hopkinson bar system with square stress wave loading according to claim 3, characterized in that: The support assembly (23) further comprises two first support frames (233) movably mounted on the outside of the incident rod body (212), the front sides of the two first support frames (233) being threadedly mounted with a first screw rod (234), and the outer side of the transmission rod (216) being movably mounted with two second support frames (235), the front sides of the two second support frames (235) being threadedly mounted with a second screw rod (236).

8. The electromagnetic Hopkinson bar system with square stress wave loading according to claim 7, characterized in that: The rear ends of the first screw rod (234) are threadedly passed through the front sides of the two first support frames (233) and are closely attached to the outer side of the incident rod body (212), and the rear ends of the second screw rod (236) are threadedly passed through the front sides of the two second support frames (235) and are closely attached to the outer side of the transmission rod (216).

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