CN112782009A - Hopkinson bar experiment system suitable for soft materials - Google Patents
Hopkinson bar experiment system suitable for soft materials Download PDFInfo
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- CN112782009A CN112782009A CN202010654875.9A CN202010654875A CN112782009A CN 112782009 A CN112782009 A CN 112782009A CN 202010654875 A CN202010654875 A CN 202010654875A CN 112782009 A CN112782009 A CN 112782009A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/30—Investigating strength properties of solid materials by application of mechanical stress by applying a single impulsive force, e.g. by falling weight
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/003—Generation of the force
- G01N2203/0042—Pneumatic or hydraulic means
- G01N2203/0044—Pneumatic means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0075—Strain-stress relations or elastic constants
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0098—Tests specified by its name, e.g. Charpy, Brinnel, Mullen
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/025—Geometry of the test
- G01N2203/0252—Monoaxial, i.e. the forces being applied along a single axis of the specimen
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/0641—Indicating or recording means; Sensing means using optical, X-ray, ultraviolet, infrared or similar detectors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0676—Force, weight, load, energy, speed or acceleration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0682—Spatial dimension, e.g. length, area, angle
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- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
The application discloses hopkinson pole experimental system suitable for softwood material, it includes: the collision bullet, the incident rod and the transmission tube are coaxially arranged; a viscoelastic material sample with the dynamic elastic modulus below 10MPa is clamped between the incident rod and the transmission tube, and a waveform shaper for delaying the rising edge of an incident pulse is arranged between the impact bullet and the incident rod; the length of striking bullet is 1.5m just striking bullet adopts the ya keli material preparation, the length of incident rod is 5m just the incident pole adopts the titanium alloy material preparation, the inside cavity of transmission tube just the transmission tube adopts the ya keli material preparation. By the method and the device, the viscoelastic material sample can reach a stress equilibrium state in a dynamic loading process.
Description
Technical Field
The invention relates to a dynamic mechanical property testing technology of materials, in particular to a Hopkinson bar experiment system suitable for soft materials.
Background
The split hopkinson bar experimental technique is mainly based on two basic assumptions. One is a one-dimensional stressThe wave assumption, which is basically true in the case of small rod diameters. The other is the assumption that the stress and strain in the measured sample are uniformly distributed along the length of the sample, which is called uniformity assumption for short. Under the assumption of uniformity, the strain in the sample can be directly determined from the difference in displacement between the two ends of the sample. At the initial stage of stress wave entering the sample from the incident rod, the sample has obvious stress strain steps and gradients, and for realizing the assumption of uniformity, the stress difference between two ends of the sample is required to be gradually reduced to a negligible degree after the added carrier wave is reflected in the sample for multiple times. Under simple approximation, the wave speed of a sine wave is independent of the wavelength and is
Where c is the wave velocity, E is the elastic modulus, ρ is the density, and the wave impedance β of the material is defined as β ═ ρ c, expressed in terms of the wave velocity
Research shows that the wave impedance difference between the sample and the Hopkinson bar material has a remarkable influence on the stress balance speed, namely the smaller the wave impedance difference is, the fewer the stress wave reflection times required by the sample to reach the stress balance are. The sample that traditional disconnect-type hopkinson pole experimental system tested is mostly metal specimen, and hopkinson pole homogeneity assumes very easily to satisfy.
However, in practical applications, due to the material specificity of the sample to be studied, such as a biological soft material, a polymer soft material, etc., the density and the elastic modulus of the material are very small, so that the wave impedance of the material is very low, the wave impedance of the material is very different from that of a rod material, the time for achieving the assumption of stress balance in the loading process of one incident wave in the experiment is long, the traditional hopkinson rod experiment device cannot achieve stress balance in the loading time, and therefore the dynamic mechanical property of the material under a high strain rate cannot be accurately obtained, and the assumption of uniformity of the split hopkinson rod cannot be met.
Disclosure of Invention
The invention mainly aims to provide a Hopkinson bar experiment system suitable for soft materials, and aims to solve the problems that stress balance cannot be realized when a soft material sample is loaded by a traditional Hopkinson bar experiment device, and dynamic mechanical properties of the material under a high strain rate cannot be accurately obtained.
According to an aspect of an embodiment of the present invention, a hopkinson rod experiment system suitable for soft materials is provided, which includes: the collision bullet, the incident rod and the transmission tube are coaxially arranged; a viscoelastic material sample with the dynamic elastic modulus below 10MPa is clamped between the incident rod and the transmission tube, and a waveform shaper for delaying the rising edge of an incident pulse is arranged between the impact bullet and the incident rod; the length of striking bullet is greater than 1.5m just it adopts acrylic material to make to strike the bullet, the length of incident rod is at least 2 times of the length of striking bullet just the incident rod adopts titanium alloy material preparation, the inside cavity of transmission tube just the transmission tube adopts acrylic material preparation.
Wherein, a protective cover is arranged on the periphery of the viscoelastic material sample; the incidence rod is impacted by the impact bullet and impacts and loads the viscoelastic material sample, and the protective cover collects sample fragments generated after the viscoelastic material sample is damaged.
Through holes corresponding to the diameters of the incident rod and the transmission tube are respectively formed in the two sides of the protective cover, and the incident rod and the transmission tube respectively extend into the protective cover from the through holes to clamp the viscoelastic material sample.
The viscoelastic material sample deformation monitoring device comprises a viscoelastic material sample, a high-speed camera, a protective cover and an observation window, wherein the viscoelastic material sample deformation monitoring device further comprises the high-speed camera, and the protective cover is further provided with the observation window used for shooting the deformation process of the viscoelastic material sample by the high-speed camera.
The size of the wave shaper is 2mm in length, 2mm in width and 1mm in thickness, and the wave shaper is made of rubber materials.
The system further comprises a semiconductor strain gauge for acquiring a transmission signal of the transmission tube and a metal strain gauge for acquiring an incident signal of the incident rod, wherein the sensitivity coefficient of the semiconductor strain gauge is 50-60 times that of the metal strain gauge.
According to another aspect of the embodiments of the present invention, there is also provided a hopkinson rod experiment system, including: a split Hopkinson bar arrangement comprising a coaxially arranged impact bullet, an incident bar and a transmission tube; a viscoelastic material sample is clamped between the incident rod and the transmission tube, and the dynamic elastic modulus of the viscoelastic material sample is below 10 MPa; a waveform shaper for delaying the rising edge of an incident pulse is arranged between the impact bullet and the incident rod; the length of the impact bullet is more than 1.5m, the impact bullet is made of an acrylic material, the length of the incident rod is at least 2 times of the length of the impact bullet, the incident rod is made of a titanium alloy material, the transmission tube is hollow, and the transmission tube is made of an acrylic material; a protective cover arranged at the periphery of the viscoelastic material sample, wherein the protective cover collects sample fragments generated after the viscoelastic material sample is damaged; and the high-speed camera is used for shooting the deformation process of the viscoelastic material sample through an observation window arranged on the protective cover.
Through holes are formed in the two sides of the protective cover respectively, the through holes correspond to the incident rods and the transmission tubes in diameter respectively, and the incident rods and the transmission tubes extend into the protective cover from the through holes respectively to clamp the viscoelastic material sample.
The size of the wave shaper is 2mm in length, 2mm in width and 1mm in thickness, and the wave shaper is made of rubber materials.
The pulse width of an incident pulse is increased by using the long bullet with low wave speed, the rising edge of the incident pulse is delayed by using the waveform shaper suitable for dynamic loading of the viscoelastic material sample, the loading time of the incident wave is further prolonged, and sufficient time is provided for the stress wave to reflect back and forth in the sample, so that the viscoelastic material sample reaches a stress balance state in the dynamic loading process; in addition, by using the hollow transmission tube with low elastic modulus, the weak transmission signal of the viscoelastic material in the dynamic loading process can be accurately measured, and the problem that the transmission signal is difficult to collect is solved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
FIG. 1 is a schematic diagram of a Hopkinson bar experiment system according to an embodiment of the present invention;
fig. 2 is a schematic diagram of the shaping effect of a wave shaper of multiple materials according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention and the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The technical solutions provided by the embodiments of the present invention are described in detail below with reference to the accompanying drawings.
The split Hopkinson bar experiment technology is one of the most common methods for measuring the dynamic mechanical property of a material under high strain rate at present, and the device mainly comprises an air chamber, a bullet, an incident bar, a transmission tube, an energy absorption device and a data acquisition system. The basic principle of the hopkinson bar method is: the sample is placed between the incident rod and the transmission tube, the bullet is pushed by high-pressure gas to impact the incident rod at a certain speed, compression stress waves are generated in the incident rod (pulse signals are measured by a strain gauge attached to the incident rod), and the sample is loaded. Meanwhile, due to the fact that wave impedance between the incident rod and the sample is not matched, part of incident waves can be reflected to the incident rod and measured through the strain gauge attached to the incident rod, and the other part of stress waves can penetrate through the sample to reach the transmission tube and are measured through the strain gauge on the transmission tube. And carrying out data processing on the measured incident wave, reflected wave and transmitted wave to obtain the stress-strain relationship of the material, and obtaining the dynamic mechanical property of the material under high strain rate.
From one-dimensional stress wave theory, it is known that the duration of a right-going stress pulse in an incident rod is equal to the time for a wave to go back and forth once inside a bullet, so the length of the bullet and the wave velocity determine the pulse width of the stress wave. In addition, for particularly soft sample materials, there is no guarantee that the sample material will meet the split hopkinson bar uniformity assumption.
According to an embodiment of the present invention, there is provided a hopkinson rod experiment system suitable for soft materials, as shown in fig. 1, the system including: the device comprises a split Hopkinson bar (SHPB) experimental device, a high-speed camera and a protective cover. Wherein, disconnect-type hopkinson pole experimental apparatus mainly includes: the device comprises a gas cylinder (not shown in the figure), a gas chamber 1, a bullet emission cavity 2, a bullet 3, an incidence rod 9, a transmission tube 14, an energy absorber 15 and a data acquisition system, wherein the device is arranged on an experiment platform 16 except the data acquisition system, the experiment platform 16 is provided with a supporting seat 7 for supporting the incidence rod and the transmission tube, and the energy absorber 15 is arranged at the tail end of the transmission tube 14 and used for absorbing residual energy transmitted by the transmission tube and preventing the transmission tube from further sliding to play a role in buffering.
Wherein, the bullet (or called as an impact bullet) 3 is arranged in the bullet shooting cavity 2, the axes of the bullet 3, the incident rod 9 and the transmission tube 14 are kept on the same straight line, the viscoelastic material sample 10 is clamped between the incident rod 9 and the transmission tube 14, and the incident rod 9 and the transmission tube 14 dynamically load the viscoelastic material sample 10. In the embodiment of the present application, the viscoelastic material sample may be referred to as a soft material sample, and is a soft material such as a polymer, a low-density foam, or a bio-soft material, which has extremely low wave impedance and extremely weak transmission signal. Generally, the dynamic elastic modulus of the viscoelastic material sample in the present application is on the order of 10MPa or less.
From one-dimensional stress wave theory knowledge, it is known that the right-hand (in the orientation of fig. 1) stress pulse duration in an incident rod is equal to the time for a wave to go back and forth once inside a bullet. The embodiment of the application selects long bullets, for example, the length of the bullets is larger than 1.5m, the bullet material is a low-wave-speed acrylic (PMMA) material, the pulse width of incident waves is increased to the maximum extent, and sufficient time is provided for the sample to reach stress balance.
Vaseline is coated on two end faces, close to the sample, of the incident rod 9 and the transmission tube 14 to eliminate the friction effect of the sample, and the sample 10 is prevented from forming a drum shape in the loading process to cause stress imbalance. In order to prevent the incident wave and the reflected wave part that the foil gage was gathered on the incident rod from offsetting, this application embodiment adopts longer incident rod, and the length of incident rod is 2 times of the length of bullet at least, and the length of incident rod can be 5m for example. The incident rod is made of high-strength titanium alloy, the metal strain gauge is attached to the outer wall of the position of the incident rod 1/2, the strain gauge is connected with the bridge box, the bridge box is connected with the oscilloscope, and the incident signal and the reflected signal are output to provide data for subsequent experimental analysis. The viscoelastic material has low wave impedance and weak transmission signal, and the stress in the sample is directly related to the transmission signal measured on the transmission tube.
In order to solve the problem that the transmission signal is difficult to acquire, PMMA with low elastic modulus is selected as the material of the transmission tube, the elastic modulus is about 4GPa, and compared with an aluminum alloy material (the elastic modulus is calculated by 70 GPa), the amplitude of the transmission signal is improved by 17.5 times. In order to reduce the cross-sectional area of the transmission tube on the basis of matching with the diameter of the incident rod, the transmission tube is a hollow tube, and the amplitude of a transmission signal is improved to a certain extent; and then a semiconductor strain gauge with a higher sensitivity coefficient (the sensitivity coefficient of the semiconductor strain gauge is 50-60 times of that of the metal strain gauge) is combined, so that a weak transmission signal of the viscoelastic material can be accurately acquired.
According to an embodiment of the application, the system further comprises a wave shaper 4, a boss 5 and a stop 6. Wherein, the limiting device 6 can be a rigid limiting device fixed on the experiment platform 16, the rigid limiting device 6 has a through hole, the diameter of the through hole is slightly larger than the diameter of the incident rod 9, so that the incident rod 9 can pass through the through hole. And, there is boss 5 (or called flange) in the striking end of incident rod 9 and bullet 3, boss 5 can be integrated with incident rod 9. The boss 5 has a diameter larger than that of the through-hole. The entrance rod 9 can be moved a predetermined distance by the boss 5 and the rigid stopper 6. In addition, according to the thickness dimension of the test sample measured before the experiment, the distance between the boss 5 and the rigid limiting device 6 is controlled, and different loading strains of the viscoelastic material test sample 10 can be obtained.
In the present embodiment, a wave shaper 4 is also provided at the impact end of the boss 5. The waveform shaper is used for filtering and shaping the generated incident wave. The viscoelastic material sample 10 is soft and low in strength, so that the wave shaper 4 can be made of a limited number of materials. If no waveform shaper is arranged in the dynamic experiment loading process, the loading pulse is uneven due to high-frequency oscillation, and the calculated mechanical property error of the material is larger; and the incident pulse is rectangular, the rising edge is steep, and enough time is not available to enable the stress pulse to reflect back and forth in the viscoelastic material sample for multiple times until stress balance is achieved, so that the assumed conditions of a Hopkinson bar experiment cannot be met. Referring to fig. 2, the commonly used wave shaper material is plasticine, paper, etc., but the shaping effect is unstable because the shape and size of the plasticine are difficult to fix, while the shaping effect of the paper as the shaper of the viscoelastic material is far insufficient for the viscoelastic material to realize a stress equilibrium state in the impact loading process. Through a plurality of experiments and comparisons, the waveform shaper 4 can be made of rubber materials, the waveform shaper 4 can be a rubber sheet with the length of 2mm, the width of 2mm and the thickness of 1mm, so that the rising edge time of a stress wave pulse can be delayed to 240 mu s, and the stress wave has enough time to be reflected back and forth in the viscoelastic material sample 10 until a stress equilibrium state is reached.
The data acquisition system specifically includes a metal strain gauge 8, a semiconductor strain gauge 13, a bridge box 17 (wheatstone bridge), an oscilloscope 19, and a power supply 18. The two metal strain gauges 8 are relatively adhered to the outer wall of the 1/2 position of the incident rod 9, the metal strain gauges 8 are connected with the bridge box 17 through a conducting wire, the bridge box 17 is connected with the oscilloscope 19 through a channel wire, the other interface of the bridge box 17 is connected with the power supply 18 through a conducting wire, and the power supply 18 is connected with a ground wire through a conducting wire. The two semiconductor strain gauges 13 are oppositely stuck on the outer wall of the transmission tube 14 close to the sample end, the semiconductor strain gauges 13 are connected with a bridge box 17 through a conducting wire, the bridge box 17 is connected with an oscilloscope 19 through a channel wire, the other interface of the bridge box 17 is connected with a power supply 18 through a conducting wire, and the power supply 18 is connected with a ground wire through a conducting wire. In the embodiment of the present application, the sensitivity coefficient of the semiconductor strain gauge attached to the transmission tube 14 is much larger than that of the metal strain gauge attached to the incident rod 9, specifically, the sensitivity coefficient of the semiconductor strain gauge is 50-60 times that of the metal strain gauge, for example, the sensitivity coefficient of the metal strain gauge 8 may be 2.22, and the sensitivity coefficient of the semiconductor strain gauge 13 may be 110. By using a semiconductor strain gage with a higher sensitivity coefficient,
a shield 12 is disposed on the periphery of the viscoelastic material sample 10, the shield 12 may be in a rectangular parallelepiped shape, the left and right opposite sides of the shield 12 are respectively provided with an incident rod perforation and a transmission tube perforation having diameters equivalent to those of the incident rod 9 and the transmission tube 14, the incident rod 9 and the transmission tube 14 respectively penetrate into the shield 12 from the incident rod perforation and the transmission tube perforation, and the viscoelastic material sample 10 is held between the incident rod 9 and the transmission tube 14. The protective cover 12 is provided with a transparent observation window facing the viscoelastic material sample 10, and the camera support supports the high-speed camera 11, so that the lens of the high-speed camera is on the same horizontal plane with the sample 10 and faces the sample 10, and the whole deformation process of the sample 10 in the loading process is recorded.
During the experiment, the inflation device is started, the bullet 3 is pressurized, the bullet launching valve is started, the bullet 3 impacts the incident rod 9 to impact and load the viscoelastic material sample 10, the sample deformation process is recorded through the high-speed camera 11, and the sample fragments after impact are collected through the protective cover 12.
The ultra-long Hopkinson bar system is used, the material and the size of the bar piece are improved, the problems that the transmission signal of the viscoelastic material sample is weak and the sample is difficult to reach stress balance are solved, the stress-strain response of the viscoelastic material sample under the dynamic loading with high strain rate is accurately measured, and therefore the dynamic mechanical property test of the viscoelastic material sample is achieved.
In summary, the embodiments according to the present application have at least the following effects:
1. the application can accurately measure weak transmission signals of the viscoelastic material sample in the dynamic loading process by using the hollow transmission tube with low elastic modulus and matching with the semiconductor strain gauge with high sensitivity coefficient, and solves the problem that the transmission signals are difficult to collect;
2. the pulse width of the incident pulse is increased by using the low wave speed and the long bullet, and in addition, the rising edge of the incident pulse is delayed by using the waveform shaper suitable for dynamic loading of the viscoelastic material sample, so that the loading time of the incident wave is further prolonged, sufficient time is provided for the back-and-forth reflection of the stress wave in the sample, and the viscoelastic material sample reaches a stress balance state in the dynamic loading process.
3. This application sets up the cuboid protection casing through using in the sample periphery, can collect the sample piece after the impact for follow-up experiment is observed.
4. The deformation process of the viscoelastic material sample in dynamic loading is recorded by using the high-speed camera, the deformation states of the sample under different strains are analyzed, and whether the viscoelastic material sample achieves stress balance and uniform deformation in the dynamic loading process is verified.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The above description is only an example of the present invention, and is not intended to limit the present invention, and it is obvious to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (10)
1. The utility model provides a Hopkinson bar experiment system suitable for soft materials which characterized in that includes: the collision bullet, the incident rod and the transmission tube are coaxially arranged; a viscoelastic material sample with the dynamic elastic modulus below 10MPa is clamped between the incident rod and the transmission tube, and a waveform shaper for delaying the rising edge of an incident pulse is arranged between the impact bullet and the incident rod; the length of striking bullet is greater than 1.5m just it adopts acrylic material to make to strike the bullet, the length of incident rod is at least 2 times of the length of striking bullet just the incident rod adopts titanium alloy material preparation, the inside cavity of transmission tube just the transmission tube adopts acrylic material preparation.
2. The system of claim 1, wherein the viscoelastic material sample is provided with a protective cover at its periphery; the incidence rod is impacted by the impact bullet and impacts and loads the viscoelastic material sample, and the protective cover collects sample fragments generated after the viscoelastic material sample is damaged.
3. The system according to claim 2, wherein the two sides of the protective cover are respectively provided with through holes corresponding to the diameters of the incident rod and the transmission tube, and the incident rod and the transmission tube respectively extend into the protective cover from the through holes to clamp the viscoelastic material sample.
4. The system of claim 2, further comprising a high-speed camera, wherein the protective cover is further provided with an observation window for the high-speed camera to photograph a deformation process of the viscoelastic material sample.
5. The system of claim 1, wherein the wave shaper is sized to be 2mm long, 2mm wide and 1mm thick, and is made of a rubber material.
6. The system of claim 1, further comprising a semiconductor strain gauge for acquiring a transmission signal of the transmission tube, and a metal strain gauge for acquiring an incident signal of the incident rod, wherein a sensitivity coefficient of the semiconductor strain gauge is 50-60 times that of the metal strain gauge.
7. The utility model provides a Hopkinson bar experiment system suitable for soft materials which characterized in that includes:
a split Hopkinson bar arrangement comprising a coaxially arranged impact bullet, an incident bar and a transmission tube; a viscoelastic material sample is clamped between the incident rod and the transmission tube, and the dynamic elastic modulus of the viscoelastic material sample is below 10 MPa; a waveform shaper for delaying the rising edge of an incident pulse is arranged between the impact bullet and the incident rod; the length of the impact bullet is more than 1.5m, the impact bullet is made of an acrylic material, the length of the incident rod is at least 2 times of the length of the impact bullet, the incident rod is made of a titanium alloy material, the transmission tube is hollow, and the transmission tube is made of an acrylic material;
a protective cover arranged at the periphery of the viscoelastic material sample, wherein the protective cover collects sample fragments generated after the viscoelastic material sample is damaged;
and the high-speed camera is used for shooting the deformation process of the viscoelastic material sample through an observation window arranged on the protective cover.
8. The system according to claim 7, wherein through holes are respectively formed in two sides of the protective cover, the through holes respectively correspond to the diameters of the incident rod and the transmission tube, and the incident rod and the transmission tube respectively extend into the protective cover from the through holes to clamp the viscoelastic material sample.
9. The system of claim 7, wherein the wave shaper is sized to be 2mm long, 2mm wide and 1mm thick, and is made of a rubber material.
10. The system of claim 7, further comprising a semiconductor strain gauge for acquiring a transmission signal of the transmission tube and a metal strain gauge for acquiring an incident signal of the incident rod, wherein a sensitivity coefficient of the semiconductor strain gauge is 50-60 times that of the metal strain gauge.
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