CN113049420A - Device and method for realizing tension/compression impact fatigue test based on Hopkinson pull rod - Google Patents
Device and method for realizing tension/compression impact fatigue test based on Hopkinson pull rod Download PDFInfo
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Abstract
The invention relates to a device and a method for realizing a tension/compression impact fatigue test based on a Hopkinson pull rod, belonging to the field of material impact fatigue performance test; the device comprises a reaction mass block, an energy absorber, an energy transfer rod, a positioning pin, a transfer flange, a pulse generator, a vacuum recovery device, an emitting device, a resistance strain gauge, an incident rod, a transmission rod and an energy absorption sleeve; the energy transfer rod, the positioning pin, the incident rod and the transmission rod are coaxially arranged in sequence, and the sample is arranged between the incident rod and the transmission rod; the energy absorber is arranged between the reaction mass block and the energy transfer rod, is connected with the energy transfer rod through the return spring and is used for absorbing energy in the energy transfer rod; the pulse generator and the transmitting device are sleeved on the incident rod and used for generating incident pulses; the energy absorption sleeve is sleeved at the free end of the transmission rod. The invention can quantitatively control and test and display the impact force and the shock wave configuration in real time, and realize high-frequency continuous impact loading and other key technologies.
Description
Technical Field
The invention belongs to the field of material impact fatigue performance testing, and particularly relates to a device and a method for realizing a tension/compression impact fatigue test based on a Hopkinson pull rod.
Background
In the engineering fields of aerospace, transportation, weapon armed and the like, the material is difficult to avoid facing various extreme mechanical environments, wherein impact is one of common serious loading modes. This loading mode tends to have a high impact velocity and short duration, with the load momentarily increasing from 0 to a peak in the order of microseconds to milliseconds. The material is easy to damage under the action of impact loading, and the micro-damage is gradually accumulated and generates micro-cracks and accelerates the crack propagation under repeated impact, so that the material is finally damaged. Unlike conventional static loading, impact fatigue requires consideration of strain rate effects during material loading, and is accompanied by adiabatic temperature rise effects. The plastic flow stress, damage evolution and microstructure evolution of the material are related to the loading strain rate, so that the impact fatigue performance of the material under high strain rate is known, and the fatigue damage and failure of the structural part under the action of repeated impact load are prevented from becoming a hotspot and a difficulty of the research in the engineering field.
The chinese patent publication No. CN110926967A of document 1 discloses a free fall type impact fatigue testing machine, and the specific structure is shown in fig. 7. The testing device mainly comprises a circular wheel driving device 28, a lifting block 29, a circular wheel 30, an L-shaped plate 31, a weight 33, a punch 35 and the like. The lifting block 29 fixed to the circular wheel 30 can perform a circular motion by being driven by the motor of the circular wheel driving device 28. When the lifting block 29 is positioned at the bottommost part of the round wheel 30, the L-shaped plate 31 can be driven to move together, and at the moment, the weight 33 fastened with the L-shaped plate 31 through the connecting rod 32 and the punch 35 are lifted upwards; when the lifting block 29 moves to the top of the circular wheel 30, the lifting block is separated from the L-shaped plate 31, and the L-shaped plate 31, the weight 33 and the punch 35 fall freely under the action of gravity and impact a test sample, so that impact fatigue loading is realized. Although fatigue loading with different impact energy can be realized by adjusting the distance between the punch 35 and the sample or replacing the weight 33 with different weight, the impact loading strain rate which can be realized by the free-fall mode is higherLow (10)1～103S), and the strain rate is not constant during loading; in addition, the shock wave configuration of the equipment cannot be controlled by self, and the shock load and the corresponding deformation borne by the test sample are difficult to measure.
Currently, the Hopkinson rod system is one of the most reliable devices for testing the mechanical response of a material under high strain rate, however, the traditional Hopkinson rod needs a long time to be reloaded after one-time impact loading. In the test of impact fatigue property of material, 10 percent of the test is generally carried out3～105Even higher frequency cyclic loading, the traditional Hopkinson rod is obviously not suitable for impact fatigue loading. Document 2 "M.Isakov, S.Terho, V.Kuokkala.Low-Cycle imaging testing based on an automated split Hopkinson bar device [ C]AIP Conference Proceedings 2309,020021(2020) "provides a test device for realizing compression impact fatigue based on a Hopkinson pressure lever, and the specific structure refers to fig. 8. The device mainly comprises a bullet 37, a transmission rod 38, an incident rod 19, a sample 20, a transmission rod 21 and the like. In the impact fatigue test, the sample 20 is first mounted between the incident rod 19 and the transmission rod 21 and fixed by the sample holder 39 to prevent the sample 20 from falling down by gravity after the completion of one loading. The high pressure gas is then released to drive the bullet 37 to strike the transfer rod 38, creating a pulsed square wave into the entrance rod 19, and upon reaching the interface between the entrance rod 19 and the sample 20, a portion of the tensile pulse is reflected as a compression wave back into the entrance rod 19 and a portion of the tensile pulse loads the sample 20 and enters the transmission rod 21. After loading is complete, the air chamber at the transfer rod 38 is inflated to push the cartridge 37 back into the firing position in preparation for a second firing. The device can realize higher strain rate impact loading, but can only test the pressure-pressure impact fatigue performance of the cylindrical test sample; in order to realize rapid reciprocating impact loading, a variable cross-section transmission rod 38 is designed between the bullet 37 and the incident rod 19. Based on a one-dimensional stress wave theory, the continuous variable cross section can seriously influence the propagation of the stress wave, so that the configuration of the shock wave is difficult to control, and the analysis of a test result is influenced; furthermore, considering that each time the back-and-forth reflection of the impact stress decays to 0, which is usually in the order of milliseconds, the device cannot suppress the load of the sample 20 in the incident rod 19 and the transmission rod 21The uncontrollable stress shock waves inevitably repeatedly load the sample 20 a number of times; although the sample 20 can be well fixed by means of the pneumatic clamping device 40, the transmitted shock wave in the transmission rod 21 easily causes the breakage of the clamping device 40.
Disclosure of Invention
The technical problem to be solved is as follows:
in order to avoid the defects of the prior art, the invention provides a device and a method for realizing a tension/compression impact fatigue test based on a Hopkinson pull rod, which effectively solve the problems of low impact loading strain rate and single loading mode in the prior art, can quantitatively control and test and display impact force and shock wave configuration in real time, and realize high-frequency continuous impact loading and other key technologies.
The technical scheme of the invention is as follows: the utility model provides a device based on Hopkinson pull rod realizes drawing/presses impact fatigue test which characterized in that: the device comprises a pulse generation system, a pulse transmission absorption system, a pulse generator recovery system and a sample, wherein all the systems are coaxially arranged and axially fixed on an experiment platform in parallel;
the pulse generation system comprises a reaction mass block 1, a gun barrel 11, a pulse generator 12, a rear-end laser sensor 13 and a transmitting device 16; the reaction mass block 1 and the launching device 16 are fixed on the experiment platform through a support, the gun barrel 11 is coaxially arranged on one side of the launching device 16 facing the reaction mass block 1, and the pulse generator 12 is arranged in the gun barrel 11; the rear-end laser sensor 13 is arranged on one side of the gun barrel 11 close to the launching device 16 and is in circuit series connection with the launching device 16;
the pulse transmission absorption system comprises an energy absorber 2, a back-push spring 3, a limiting snap ring 4, a back-push top plate 5, a back-push snap ring 6, an energy transmission rod 7, a positioning pin 8, a transmission flange 9, a resistance strain gauge 18, an incident rod 19, a transmission rod 21 and an energy absorption sleeve 22, wherein the energy absorber 2, the energy transmission rod 7, the positioning pin 8, the transmission flange 9, the incident rod 19 and the transmission rod 21 are coaxially arranged on an experiment platform through a support; the incident rod 19 and the transmission rod 21 are straight rods with equal diameters and provided with resistance strain gauges 18; a first transmission flange is coaxially arranged at one end of the incident rod 19 facing the reaction mass block 1, the other end of the incident rod coaxially penetrates through the pulse generator 12 and the emitting device 16 in sequence, is coaxially connected with one end of the sample 20, can axially slide relative to the pulse generator 12 and the emitting device 16, and is provided with an incident rod limiting clamp 17 at the joint of the emitting device 16 and the incident rod 19 for limiting the movement of the incident rod 19 in the loading direction; one end of the transmission rod 21 is coaxially connected with the other end of the sample 20, the other end of the transmission rod is coaxially provided with a second transmission flange, and the energy absorption sleeve 22 is sleeved on the energy absorption sleeve 22 and is in contact with the second transmission flange; the energy transfer rod 7 is coaxially arranged outside the first transfer flange through a positioning pin 8; the limiting snap ring 4 and the push-back snap ring 6 are coaxially sleeved on the energy transfer rod 7 and used for ensuring that the energy transfer rod 7 quickly returns to a position before impact and keeping an accurate reserved distance between the energy transfer rod 7 and the transfer flange 9; the back pushing piece 5 is arranged between the limiting snap ring 4 and the back pushing snap ring 6; the energy absorber 2 is a sleeve structure with one closed end, the open end faces the energy transmission rod 7, and is connected with the back pushing plate 5 through the back pushing spring 3 and used for absorbing energy in the energy transmission rod 7;
the pulse generator recovery system comprises a front-end laser sensor 10 and a vacuum recovery device 15; the front end laser sensor 10 is arranged on the gun barrel 11, the transmitting and receiving probes of the front end laser sensor are respectively arranged on the upper side and the lower side of the first transmission flange, and the laser is ensured not to be shielded by the incident rod 19; the vacuum recovery device 15 is arranged on one side of the gun barrel 11 close to the launching device 16, the front-end laser sensor 10 is in series circuit connection with the vacuum recovery device 15, when the laser is shielded by the pulse generator 12, the voltage can be changed, and then the vacuum recovery device 15 is triggered to work.
The further technical scheme of the invention is as follows: and a pin hole is formed in the center of the end face of the first transmission flange and used for installing the positioning pin 8.
The further technical scheme of the invention is as follows: the pulse generator 12 obtains the added carrier wave of different pulse configurations, which are triangular, square, half sine or bilinear waves, by changing the geometry.
The further technical scheme of the invention is as follows: the pulse generator 12 is able to obtain different pulse amplitudes by varying the speed.
The further technical scheme of the invention is as follows: the device also comprises a limit pin 14, wherein the limit pin 14 is arranged between the rear-end laser generator 13 and the emission device 16, and the high-speed recovery pulse generator 12 is prevented from crashing the emission device 16.
The further technical scheme of the invention is as follows: the sample 20 is cylindrical or plate-shaped, the cylindrical sample is respectively connected with the incident rod 19 and the transmission rod 21 in a threaded connection mode, and the plate-shaped sample is respectively fixedly connected with the incident rod 19 and the transmission rod 21 through processing pin holes.
The further technical scheme of the invention is as follows: resistance strain gauges 18 are symmetrically pasted on the positions, one meter away from the sample 20, of the outer peripheral surface of the incident rod 19, and the resistance strain gauges 18 are also symmetrically pasted on the outer peripheral surface of the middle part of the transmission rod 21; the symmetrically posted resistance strain gauges 18 are connected into a circuit in a half-bridge mode of a Wheatstone bridge, and pulse signals are collected through a super-dynamic strain gauge and a collector.
A method for realizing pull-pull impact fatigue loading based on a device for realizing a pull/press impact fatigue test by a Hopkinson pull rod is characterized by comprising the following specific steps:
the method comprises the following steps: firstly, fixing the incident rod 19 along the loading direction by a locking limit hoop 17, and then pushing the pulse generator 12 to one end of the transmitting device 16; then, the distance between the first transmission flange on the incident rod 19 and the energy transmission rod 7 is accurately controlled through a plug gauge, and the energy transmission rod 7 is separated from the transmission flange 9 on the incident rod 19 by the reserved accurate distance;
step two: the front-end laser sensor 10 and the rear-end laser sensor 13 are sequentially started, under the drive of the emitting device 16, the pulse generator 12 impacts the first transmission flange at a set speed, tensile pulses are generated in the incident rod 19 and are transmitted to the sample 20, after the tensile pulses are loaded on the sample, part of the tensile pulses are transmitted into the transmission rod 21, and part of the tensile pulses are reflected back to the incident rod 19 in the form of compression waves; the whole stretching pulse generated by the pulse generator 12 completely enters the incident rod 19, the reserved precise distance is closed, and the right end part of the energy transfer rod 7 is contacted with the left end part of the transfer flange 9;
step three: the reflected compression wave is transmitted into the energy transfer rod 7 and is reflected as a tensile wave at the free end of the energy transfer rod 7, and because the contact surface of the energy transfer rod 7 and the transfer flange 9 can not transfer tensile load, the reflected pulse is captured by the energy transfer rod 7, so that the energy transfer rod 7 is far away from the first transfer flange, and the reflected pulse is absorbed by the energy absorber 2, so that no loading pulse exists in the incident rod 19;
meanwhile, the pulse transmitted into the transmission rod 21 through the sample 20 is captured by the energy absorption sleeve 22 at the free end of the transmission rod 21, so that the sample 20 is not loaded for multiple times;
step four: after the first impact is finished, the energy transfer rod 7 is far away from the first transfer flange, the reserved distance between the energy transfer rod and the first transfer flange is pulled back to the initial position by the back-push spring 3, when the pulse generator 12 shields the front-end laser sensor 10, the vacuum recovery device 15 is excited to recover the pulse generator 12 to the transmitting device 16 end, and secondary impact is started; the reciprocating launch and recovery pulse generator 12 is thus capable of achieving pull-pull impact fatigue loading.
The further technical scheme of the invention is as follows: in the fourth step, the back pushing plate 5 is connected with the energy absorber 2 through the back pushing spring 3; when the energy transmission rod 7 is far away from the transmission flange 9, the push-back spring 3 is compressed and pushes the push-back snap ring 6 through the push-back top plate 5 to enable the energy transmission rod 7 to be close to the first transmission flange; when the distance between the energy transmission rod 7 and the transmission flange 9 is smaller than the reserved gap, the push-back spring 3 can be stretched, the limiting snap ring 4 pulls the energy transmission rod 7 back to the initial position under the action of the pulling force of the push-back spring 3, the energy transmission rod 7 and the transmission flange 9 can be always kept at the reserved gap position, and repeated single loading is guaranteed.
A method for realizing tension-compression impact fatigue loading based on a device for realizing tension/compression impact fatigue test by a Hopkinson pull rod is characterized by comprising the following specific steps:
the method comprises the following steps: firstly, when tension-compression impact fatigue loading is carried out, the energy absorber 2, the push-back spring 3, the limit snap ring 4, the push-back piece 5 and the push-back snap ring 6 are removed,
step two: fixing the incident rod 19 along the loading direction by using a locking limit clamp 17, and pushing the pulse generator 12 to one end of the transmitting device 16;
step three: the front-end laser sensor 10 and the rear-end laser sensor 13 are sequentially started, the pulse generator 12 impacts a first transmission flange at a set speed under the driving of the transmitting device 16, a part of generated stretching pulses completely enter the incident rod 19 through the first transmission flange and move towards the sample 20, and the other part of compression pulses are transmitted into the energy transmission rod 7 and are transmitted to the reaction mass block 1; the incident pulse is divided into a continuous tensile loading pulse 23 and a compressive loading pulse 26;
step four: when the pulse is transmitted to the reaction mass block 1, the reaction mass block 1 is used as a fixed boundary, the compression pulse is still a compression wave after being reflected on the fixed boundary and enters the transmission flange 9 and the incident rod 19 along the energy transmission rod 7, and the amplitude and the pulse width of the compression pulse 26 are completely the same as those of the tension pulse 23 generated firstly except for different loading modes;
step five: after the first impact is finished, the pulse generator 12 shields the front-end laser sensor 10, the vacuum recovery device 15 is excited to recover the pulse generator 12 to the end of the transmitting device 16, and secondary impact is started; the reciprocating launch and recovery pulser 12 thus achieves tension-compression impact fatigue loading.
Advantageous effects
The invention has the beneficial effects that:
(1) for the impact force and shock wave configuration control, the impact force and shock wave configuration control is realized by changing the characteristics of the pulse generator 12, when the pulse generator 12 impacts the first transmission flange 9 at different speeds, different impact force loads can be realized on the test sample; with different geometry of the sleeve as the pulse generator 12, different shockwave configurations may be produced, as shown in FIG. 2. Meanwhile, the pulse generator 12 and the transfer flange 9 adopt a non-stress concentration design to avoid the damage and deformation caused by impact from influencing the geometric configuration of the carrier wave; (2) for the impact measurement and control performance, the strain on the incident rod 19 and the transmission rod 21 is tested through the resistance strain gauge 18, and the impact force waveform, the deformation displacement and the like are quantitatively displayed based on the one-dimensional stress wave theory; (3) for high-frequency continuous impact, the traditional single emission is changed into repeated emission, an automatic control system is added, and the high-pressure gas emission device 16 and the vacuum recovery device 15 are controlled by a pneumatic and electromechanical integrated computer to control the emission and recovery stroke, time, speed and the like of the pulse generator 12 so as to realize the automatic suction and the automatic emission of the pulse generator 12; (4) for single loading in the impact process, reflected waves are captured through the cooperation of the transmission flange 9, the positioning pin 8, the energy transmission rod 7 and the energy absorber 2, so that secondary or even multiple repeated loading of the sample by subsequent carrier waves with uncontrollable stress is inhibited, as shown in fig. 4; (5) for combined tension-compression loading, a series of incident pulses that are firstly stretched and then compressed are generated based on the fundamental laws of reflection and superposition of stress waves at the boundary through cooperation between the transfer flange 9, the energy transfer rod 7 and the reaction mass block 1, as shown in fig. 6.
Compared with the prior art in document 1, the device realizes fatigue loading based on the Hopkinson pull rod through a pulse generator 12 and an incident rod 19 in a high-speed impact mode, and compared with the traditional free-fall mode, the impact loading strain rate is higher (10)2～104S); the sample required by fatigue loading realized in a free falling mode is usually a plate with the size exceeding millimeter magnitude, the material loss is large, the irregular propagation structure effect of stress waves in the plate is obvious, and the difference of loading pulses at different positions is obvious; the relationship between the geometric shape, the mass density and the speed of the pulse generator 12 and the impact pulse (the configuration of the impact wave, the amplitude of the loading stress and the pulse width) can be obtained through a one-dimensional stress wave propagation theory, and the accurate regulation and control are realized; for the impact measurement and control performance, the impact force, the sample deformation and other mechanical responses can be obtained by real-time signal calculation of the resistance strain gauges 18 on the incident rod 19 and the transmission rod 21 in the device.
Compared with the document 2 in the background art, the energy transmission rod 7, the incident rod 19 and the transmission rod 21 for transmitting the stress wave in the device have no complicated section change, and complicated interface reflection can not occur, so that the integrity of the elastic stress wave in the transmission process can be ensured; the device disclosed by the document 2 cannot inhibit uncontrollable reflected waves from repeatedly loading a sample in each loading process, and a single pulse loading test technology (the principle is shown in fig. 3) of the device disclosed by the invention through the energy absorber 2, the energy transfer rod 7, the positioning pin 8, the transfer flange 9, the pulse generator 12 and the incident rod 19 can avoid the uncontrollable reflected waves from secondarily or even repeatedly loading the sample, and the test result is shown in fig. 4, so that the impact fatigue performance of the material can be more reliably obtained; the device disclosed by the document 2 can only realize the pressure-pressure impact fatigue loading on a cylindrical sample, the device disclosed by the invention utilizes the law of reflection of stress waves on the end face to modulate pulses with different loading modes through the reaction mass block 1, the energy transfer rod 7, the positioning pin 8, the transfer flange 9, the pulse generator 12 and the incident rod 19 (the principle is shown in figure 5), and the test result is shown in figure 6. The device can be used for testing the tensile-tensile and tensile-compressive impact fatigue performance of cylindrical and plate-shaped samples, and widens the sample form and the loading mode of the impact stress state.
Drawings
Fig. 1 is a schematic structural diagram of a device for realizing tension/compression impact fatigue based on a Hopkinson tension bar.
Fig. 2 shows different shock wave configurations generated by different pulse generators 12 striking the transfer flange 9.
FIG. 3 is a schematic diagram of the device of the present invention for tensile-tensile impact fatigue loading.
Fig. 4 shows a single tensile-loaded incident wave 23 obtained by suppressing the second tensile plus carrier wave 25 by the device of the present invention, thereby implementing the tensile-tensile impact fatigue performance test.
FIG. 5 is a schematic diagram of the device of the present invention for tension-compression impact fatigue loading.
FIG. 6 is a series of continuous tension-compression loading incident waves obtained by the device of the present invention to achieve the tension-compression impact fatigue performance test.
Fig. 7 is a schematic view of the free fall type impact fatigue test apparatus proposed in reference 1.
Fig. 8 is a schematic diagram of an apparatus for performing a compression-compression impact fatigue test based on a Hopkinson compression bar as proposed in reference 2.
Description of reference numerals: 1-reaction mass, 2-energy absorber, 3-pushback spring, 4-limit snap ring, 5-pushback piece, 6-pushback snap ring, 7-energy transfer rod, 8-positioning pin, 9-transfer flange, 10-front laser sensor, 11-barrel, 12-pulse generator, 13-rear laser sensor, 14-limit pin, 15-vacuum recovery device, 16-launching device, 17-locking limit clamp, 18-resistance strain gauge, 19-incident rod, 20-sample, 21-transmission rod, 22-energy absorption sleeve, 23-tensile incident wave, 24-reflected wave, 25-suppressed secondary tensile plus carrier wave, 26-compressive incident wave, 27-ball screw drive, 28-round wheel driving device, 29-lifting block, 30-round wheel, 31-L-shaped plate, 32-connecting rod, 33-weight, 34-bearing plate, 35-punch, 36-ball screw, 37-bullet, 38-transfer rod, 39-sample clamp and 40-pneumatic clamping device.
Detailed Description
The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.
The device for realizing the tension/compression impact fatigue test based on the Hopkinson pull rod is used for testing the impact fatigue performance of cylindrical and plate-shaped samples. The structure of the device of the invention is shown in figure 1, and can be divided into a pulse generation system, a pulse transmission system, a pulse generator recovery system and a sample. The pulse generation system mainly comprises a reaction mass block 1, an energy transfer rod 7, a positioning pin 8, a transfer flange 9, a gun barrel 11, a pulse generator 12, a rear-end laser sensor 13, an emitting device 16, an incident rod limiting clamp 17 and the like; the pulse transmission system mainly comprises an energy transmission rod 7, a positioning pin 8, a transmission flange 9, a resistance strain gauge 18, an incident rod 19, a transmission rod 21 and an energy absorption sleeve 22; the pulse generator recovery system consists of a front-end laser sensor 10, a pulse generator 12, a limit pin 14 and a vacuum recovery device 15.
As shown in fig. 1, the sleeve-type pulse generator 12 is mounted on the incident rod 19 and can freely slide on the incident rod 19, the pulse generator 12 with different materials, lengths and shapes is selected according to the loading pulse configuration, stress amplitude and pulse width specifically required in the impact fatigue performance test, and fig. 2 shows the loading pulses of triangular wave, square wave, half sine wave and the like generated by the pulse generator 12 with different lengths and shapes. Resistance strain gauges 18 are symmetrically pasted at the position, about 20 meters away from the sample, on the surface of the incident rod 19, and the two resistance strain gauges 18 are connected with a super-dynamic strain gauge in a half-bridge Wheatstone bridge mode and used for measuring pulse signals on the incident rod 19. The end of the incident rod 19 far away from the sample 20 is provided with a transfer flange 9, the transfer flange 9 and the incident rod 19 are integrated, and the pulse generator 12 is driven by the emitting device 16 to impact the transfer flange 9 at a high speed and generate a loading pulse in the incident rod 19 to be transmitted to the sample 20. An energy transmission rod 7 is arranged on the left side of the transmission flange 9, and the energy transmission rod 7 can be used for absorbing residual energy after the sample 20 is loaded in the incident rod 19 or modulating loading pulse. The middle of the transmission flange 9 is connected with the middle of the energy transmission rod 7 through a positioning pin 8, and the positioning pin 8 can ensure the coaxiality of the transmission flange 9 and the energy transmission rod 7 and also can accurately control the distance between the transmission flange 9 and the energy transmission rod 7. The energy absorber 2 is installed at the left side of the energy transmission rod 7 to absorb the energy in the energy transmission rod 7, as shown in fig. 3, the distance between the transmission flange 9 and the energy transmission rod 7 (the distance can be determined according to the length of the pulse generator 12 and the pulse stress amplitude) is controlled to enable the reflected wave 24 returning from the sample 20 after the loading is completed to be transmitted into the energy absorption rod 7 and finally absorbed by the energy absorber 2, the pulse signal collected by the resistance strain gauge 18 is shown in fig. 4, and the second row of suppressed tensile waves 25 avoids the uncontrollable reflected pulse from loading the sample 20 twice or even multiple times. The energy absorber 2 can be replaced by the reaction mass 1 to modulate the pulse, as shown in fig. 5, the reaction mass 1, the energy transmission rod 7 and the transmission flange 9 are always tightly attached, when the pulse generator 12 impacts the transmission flange 9, a part of the pulse is transmitted to the sample 20 in the incident rod 19 in the form of tensile wave 23, and the other part of the pulse is transmitted to the left by the energy transmission rod 7 in the form of compression wave and is still transmitted to the sample 20 in the incident rod 19 in the form of compression wave after being reflected by the reaction mass 1. The modulated incident wave is loaded on the sample in a form of stretching and compressing, and the incident pulse collected by the resistance strain gauge 18 on the incident rod 19 is shown in fig. 6. The right side of the sample 20 is connected with a transmission rod 21, a resistance strain gauge 18 and an incidence rod 19 are adhered to the middle of the transmission rod 21 and are consistent, a transmission flange 9 is machined on the right side of the transmission rod 21, and an energy absorption sleeve 22 is installed on the outer side of the transmission rod 21 and used for capturing transmission waves after the sample 20 is loaded so as to prevent the sample 20 from being loaded twice or even for multiple times by uncontrollable pulses.
The first pulse transmission and loading case is described above, and the recovery and reloading solution of the pulse generator 12 is explained in detail below, so as to realize the impact fatigue loading. When the pulse generator 12 impacts the transfer flange 9 for first loading, the front laser sensor 10 at the impact position of the transfer flange 9 is triggered and fed back to the vacuum recovery device 15, and the vacuum recovery device 15 starts to work, so that the pulse generator 12 is rapidly moved to the right to return to the emitting position. A limit pin 14 is arranged at the front end of the transmitting device 16 to prevent the impulse generator 12 moving at high speed from crashing the transmitting device 16. When the pulse generator 12 moves to the position of the limit pin 14 rightwards, the rear-end laser sensor 13 is triggered and fed back to the emitting device 16, and the emitting device 16 drives the pulse generator 12 to impact the transmission flange 9 at a high speed, so that secondary impact loading is realized. The reciprocating impact loading pulse is constant and the interval time is controllable, so that impact fatigue loading is realized.
The following examples are provided to illustrate the specific testing procedures of the present invention.
An incident rod 19, a transmission rod 21 and an energy transfer rod 7 are arranged on an experimental platform, so that the coaxiality of three rods is ensured; tightly attaching the transfer flange 9 on the incident rod 19, the energy transfer rod 7 and the reaction mass block 1, and tightly attaching the transfer flange 9 on the transmission rod 21 and the energy absorption sleeve 22; according to the pulse configuration required by the test, loading a pulse width to select a proper pulse generator 12, sleeving the pulse generator 12 into an incident rod 19 to ensure that the pulse generator 12 can freely slide, and firstly, placing the pulse generator 12 at a limit pin 14 at the front end of a transmitting device 16; both ends of a cylindrical sample 20 are screwed into the incident rod 19 and the transmission rod 21 by screw connection, or a plate-shaped sample 20 with a pin hole at a holding end is connected with the incident rod 19 and the transmission rod 21 by a pin.
And 2, setting parameters of the launching and recovery device.
Setting parameters of a transmitting device 16 according to a loading strain rate required in an impact fatigue performance test, and driving a pulse generator 12 to impact a transfer flange 9 at a fixed speed so as to obtain a proper pulse stress amplitude; according to the fatigue loading frequency requirement, the parameters of the vacuum recovery device 15 are set to adjust the recovery speed of the pulse generator 12.
And 3, starting a pulse generation system to realize impact loading.
Simultaneously, the front-end laser sensor 10 and the rear-end laser sensor 13 are started, the rear-end laser sensor 13 is triggered at first, the transmitting device 16 is started, the pulse generator 12 is driven to impact the transmission flange 9, a part of pulses are transmitted to the sample 20 in the incident rod 19 in the form of tensile waves 23, the other part of pulses are transmitted to the energy transmission rod 7 in the form of compression waves 26 after being reflected by the fixed end face of the reaction mass block 1 and are also transmitted to the sample 20 in the form of compression waves 26 in the incident rod 19, and a column of modulated continuous incident waves can be divided into a form of firstly stretching and then compressing to load the sample 20, as shown in fig. 6;
step 4, recycling and repeated loading
After the first impact loading is finished, the front-end laser sensor 10 at the impact position of the transfer flange 9 is triggered and fed back to the vacuum recovery device 15 to rapidly move the pulse generator 12 to the right to return to the emission position; the back end laser sensor 13 is triggered and step 3 is repeated to achieve the second shock loading. And (4) repeating the step (3) and the step (4), wherein the reciprocating impact loading can realize the impact fatigue performance test of the material.
And 5, acquiring pulse signals and processing data.
The resistance strain gauges 18 are symmetrically attached to the surface of the incident rod 19 at a position one meter away from the sample 20, and the resistance strain gauges 18 are also symmetrically attached to the middle of the transmission rod 21. The symmetrically posted resistance strain gauges 18 are connected into the circuit in a half-bridge manner of a Wheatstone bridge and acquire pulse signals through a super-dynamic strain gauge and a collector. According to the basic principle that one-dimensional elastic stress waves are propagated in the rod and the assumption that the sample is strained along the loading direction and the stress distribution is uniform, the impact load borne by the sample in each impact loading process and the corresponding deformation can be obtained.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.
Claims (9)
1. The utility model provides a device based on Hopkinson pull rod realizes drawing/presses impact fatigue test which characterized in that: the device comprises a pulse generation system, a pulse transmission absorption system, a pulse generator recovery system and a sample, wherein all the systems are coaxially arranged and axially fixed on an experiment platform in parallel;
the pulse generation system comprises a reaction mass block (1), a gun barrel (11), a pulse generator (12), a rear-end laser sensor (13) and a transmitting device (16); the reaction mass block (1) and the launching device (16) are fixed on the experiment platform through a support, the gun barrel (11) is coaxially arranged on one side of the launching device (16) facing the reaction mass block (1), and the pulse generator (12) is arranged in the gun barrel (11); the rear-end laser sensor (13) is arranged on one side of the gun barrel (11) close to the launching device (16) and is connected with the launching device (16) in series;
the pulse transmission absorption system comprises an energy absorber (2), a back-push spring (3), a limiting snap ring (4), a back-push plate (5), a back-push snap ring (6), an energy transmission rod (7), a positioning pin (8), a transmission flange (9), a resistance strain gauge (18), an incident rod (19), a transmission rod (21) and an energy absorption sleeve (22), wherein the energy absorber (2), the energy transmission rod (7), the positioning pin (8), the transmission flange (9), the incident rod (19) and the transmission rod (21) are coaxially arranged on an experiment platform through a support; the incident rod (19) and the transmission rod (21) are straight rods with equal diameters and provided with resistance strain gauges (18); a first transmission flange is coaxially arranged at one end, facing the reaction mass block (1), of the incident rod (19), the other end of the incident rod coaxially penetrates through the pulse generator (12) and the emitting device (16) in sequence and is coaxially connected with one end of the sample (20) and can slide relative to the pulse generator (12) and the emitting device (16) along the axial direction, and the incident rod limiting clamp (17) is arranged at the connecting position of the emitting device (16) and the incident rod (19) and used for limiting the movement of the incident rod (19) along the loading direction; one end of the transmission rod (21) is coaxially connected with the other end of the sample (20), the other end of the transmission rod is coaxially provided with a second transmission flange, and the energy absorption sleeve (22) is sleeved on the energy absorption sleeve (22) and is in contact with the second transmission flange; the energy transfer rod (7) is coaxially arranged on the outer side of the first transfer flange through a positioning pin (8); the limiting snap ring (4) and the push-back snap ring (6) are coaxially sleeved on the energy transfer rod (7) and used for ensuring that the energy transfer rod (7) quickly returns to a position before impact and keeping an accurate reserved distance between the energy transfer rod (7) and the transfer flange (9); the back pushing plate (5) is arranged between the limiting snap ring (4) and the back pushing snap ring (6); the energy absorber (2) is of a sleeve structure with one closed end, the open end faces the energy transmission rod (7), and the energy absorber is connected with the back pushing plate (5) through the back pushing spring (3) and is used for absorbing energy in the energy transmission rod (7);
the pulse generator recovery system comprises a front-end laser sensor (10) and a vacuum recovery device (15); the front end laser sensor (10) is arranged on the gun barrel (11), and the transmitting and receiving probes of the front end laser sensor are respectively arranged on the upper side and the lower side of the first transmission flange and ensure that laser is not shielded by the incident rod (19); the vacuum recovery device (15) is arranged on one side, close to the launching device (16), of the gun barrel (11), the front-end laser sensor (10) is connected with the vacuum recovery device (15) in series through a circuit, when laser is shielded by the pulse generator (12), voltage can be changed, and then the vacuum recovery device (15) is triggered to work.
2. The device for realizing the tension/compression impact fatigue test based on the Hopkinson pull rod according to claim 1, wherein: and a pin hole is formed in the center of the end face of the first transmission flange and used for installing a positioning pin (8).
3. The device for realizing the tension/compression impact fatigue test based on the Hopkinson pull rod according to claim 1, wherein: the pulse generator (12) obtains the added carrier wave of different pulse configurations by changing the geometry, the pulse configurations are triangular waves, square waves, half sine waves or bilinear waves.
4. The device for realizing the tension/compression impact fatigue test based on the Hopkinson pull rod according to claim 1, wherein: the pulse generator (12) is capable of obtaining different pulse amplitudes by varying the speed.
The further technical scheme of the invention is as follows: the high-speed pulse generator is characterized by further comprising a limiting pin (14), wherein the limiting pin (14) is arranged between the rear-end laser generator (13) and the emission device (16), and the emission device (16) is prevented from being damaged by the high-speed recovered pulse generator (12).
5. The device for realizing the tension/compression impact fatigue test based on the Hopkinson pull rod according to claim 1, wherein: the test sample (20) is cylindrical or plate-shaped, the cylindrical test sample is respectively connected with the incident rod (19) and the transmission rod (21) in a threaded connection mode, and the plate-shaped test sample is respectively fixedly connected with the incident rod (19) and the transmission rod (21) through processing pin holes.
6. The device for realizing the tension/compression impact fatigue test based on the Hopkinson pull rod according to claim 1, wherein: resistance strain gauges (18) are symmetrically pasted on the positions, one meter away from the sample (20), of the outer peripheral surface of the incident rod (19), and the resistance strain gauges (18) are also symmetrically pasted on the outer peripheral surface of the middle part of the transmission rod (21); the symmetrically posted resistance strain gauges (18) are connected into a circuit in a half-bridge mode of a Wheatstone bridge, and pulse signals are acquired through a super-dynamic strain gauge and a collector.
7. A method for realizing tension-tension impact fatigue loading by adopting the device for realizing tension/compression impact fatigue test based on the Hopkinson pull rod of any one of claims 1 to 6, which is characterized by comprising the following specific steps:
the method comprises the following steps: firstly, fixing an incident rod (19) along a loading direction through a locking limit clamp (17), and then pushing a pulse generator (12) to one end of a transmitting device (16); then, the distance between the first transmission flange on the incident rod (19) and the energy transmission rod (7) is accurately controlled through a plug gauge, and the reserved accurate distance separates the energy transmission rod (7) from the transmission flange (9) on the incident rod (19);
step two: the front-end laser sensor (10) and the rear-end laser sensor (13) are sequentially started, under the drive of the emitting device (16), the pulse generator (12) impacts the first transmission flange at a set speed, tensile pulses are generated in the incident rod (19) and transmitted to the sample (20), after the tensile pulses are loaded on the sample, part of the tensile pulses are transmitted into the transmission rod (21), and part of the tensile pulses are reflected back to the incident rod (19) in a compression wave mode; the whole stretching pulse generated by the pulse generator (12) completely enters the incident rod (19), the reserved accurate distance is closed, and the right end part of the energy transfer rod (7) is contacted with the left end part of the transfer flange (9);
step three: the reflected compression wave is transmitted into the energy transfer rod (7) and is reflected to be tensile wave at the free end of the energy transfer rod (7), and because the contact surface of the energy transfer rod (7) and the transfer flange (9) can not transfer tensile load, the reflected pulse is captured by the energy transfer rod (7), so that the energy transfer rod (7) is far away from the first transfer flange, and then the reflected pulse is absorbed by the energy absorber (2), and no loading pulse exists in the incident rod (19);
meanwhile, the pulse transmitted into the transmission rod (21) through the sample (20) is captured by the energy absorption sleeve (22) at the free end of the transmission rod (21) and does not load the sample (20) for multiple times;
step four: after the first impact is finished, the energy transfer rod (7) is far away from the first transfer flange, the reserved distance between the energy transfer rod and the first transfer flange is pulled back to the initial position by the back-push spring (3), when the pulse generator (12) shields the front-end laser sensor (10), the vacuum recovery device (15) is excited to recover the pulse generator (12) to the end of the launching device (16), and secondary impact is started; the reciprocating type launching and recovery pulse generator (12) can realize the tension-tension impact fatigue loading.
8. The method for realizing the tension-tension impact fatigue loading of the device for realizing the tension/compression impact fatigue test based on the Hopkinson tension bar according to claim 7, wherein the method comprises the following steps: in the fourth step, the back pushing plate (5) is connected with the energy absorber (2) through the back pushing spring (3); when the energy transfer rod (7) is far away from the transfer flange (9), the push-back spring (3) is compressed, and the push-back clamping ring (6) is pushed by the push-back top plate (5) to enable the energy transfer rod (7) to be close to the first transfer flange; when the distance between the energy transfer rod (7) and the transfer flange (9) is smaller than the reserved gap, the push-back spring (3) can be stretched, the limiting snap ring (4) pulls the energy transfer rod (7) back to the initial position under the action of the pulling force of the push-back spring (3), the energy transfer rod (7) and the transfer flange (9) can be always kept at the reserved gap position, and repeated single loading is guaranteed.
9. A method for realizing tension-compression impact fatigue loading by adopting the device for realizing tension/compression impact fatigue test based on the Hopkinson pull rod of any one of claims 1 to 6, which is characterized by comprising the following specific steps:
the method comprises the following steps: firstly, removing an energy absorber (2), a push-back spring (3), a limit snap ring (4), a push-back piece (5) and a push-back snap ring (6) when tension-compression impact fatigue loading is carried out;
step two: fixing the incident rod (19) along the loading direction by using a locking limit clamp (17), and pushing the pulse generator (12) to one end of the transmitting device (16);
step three: the front-end laser sensor (10) and the rear-end laser sensor (13) are sequentially started, the pulse generator (12) impacts the first transmission flange at a set speed under the driving of the emitting device (16), a part of generated stretching pulses completely enter the incident rod (19) through the first transmission flange and move towards the sample (20), and the other part of compression pulses are transmitted into the energy transmission rod (7) and are transmitted to the reaction mass block (1); the incident pulse is divided into a continuous tensile loading pulse (23) and a compressive loading pulse (26);
step four: when the pulse is transmitted to the reaction mass block 1, the reaction mass block 1 is used as a fixed boundary, the compression pulse is still a compression wave after being reflected on the fixed boundary and enters a transmission flange (9) and an incident rod (19) along an energy transmission rod (7), and the amplitude and the pulse width of the compression pulse (26) and the firstly generated tension pulse (23) are completely the same except that the loading mode is different;
step five: after the first impact is finished, the pulse generator (12) shields the front-end laser sensor (10), the vacuum recovery device (15) is excited to recover the pulse generator (12) to the end of the transmitting device (16), and the secondary impact is started; the reciprocating type launching and recovery pulse generator (12) can realize tension-compression impact fatigue loading.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113607545A (en) * | 2021-08-17 | 2021-11-05 | 西北工业大学 | Single pulse separation type Hopkinson pull rod experiment device based on electromagnetic force loading |
| CN117686358A (en) * | 2024-02-02 | 2024-03-12 | 煤炭科学研究总院有限公司 | Parameter determination method and device for low-frequency controllable impact physical simulation device |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113607545A (en) * | 2021-08-17 | 2021-11-05 | 西北工业大学 | Single pulse separation type Hopkinson pull rod experiment device based on electromagnetic force loading |
| CN113607545B (en) * | 2021-08-17 | 2024-05-07 | 西北工业大学 | Single pulse separation type Hopkinson pull rod experimental device based on electromagnetic force loading |
| CN117686358A (en) * | 2024-02-02 | 2024-03-12 | 煤炭科学研究总院有限公司 | Parameter determination method and device for low-frequency controllable impact physical simulation device |
| CN117686358B (en) * | 2024-02-02 | 2024-04-05 | 煤炭科学研究总院有限公司 | Parameter determination method and device for low-frequency controllable impact physical simulation device |
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