All-electric measurement and control instrumented tensile impact fatigue experiment system

Abstract

The invention provides an all-electric measurement and control instrumented tensile impact fatigue experiment system, and mainly solves the problems that stress wave pulses are transmitted back and forth in a rod, and a cyclic loading test and an automatic test cannot be repeated. According to the invention, the Hopkinson pull rod system, the stress wave riveting gun module, the lead screw dragging device and the comprehensive detection and control device are utilized to realize single-time repeated impact loading of a test piece, control the launching and recovery of a projectile body, realize closed-loop control of loading force, and improve the reliability of the test piece. According to the invention, a single loading impact fatigue function of continuous tensile impact on a sample is realized through the energy absorption and limiting device and the screw rod dragging device, and instrumentation and full automation of an impact tensile fatigue experiment are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of material fatigue performance test experiments, and mainly relates to an instrumented tensile impact fatigue test system with full electrical measurement and control. Background Art

[0002] Various equipment and engineering structures are often subjected to repeated impact loading (also known as impact fatigue) during use. Impact fatigue means that the speed of each loading is high and the deformation rate of the material is high, that is, the impact speed can reach tens of meters per second and the strain rate of the material can reach 10 2 / s. Under high loading rates, equipment and engineering structures usually experience crack initiation, cracking and expansion under impact tensile stress, which eventually lead to failure under high strain rate repeated tensile stress. Therefore, the impact repeated tensile test loading device, i.e., the impact fatigue test system, is an indispensable technical means for designing structures and evaluating material properties.

[0003] The prior art discloses a method for achieving high-speed loading of a riveted joint (cylindrical material), and the device is generally referred to as a "stress wave riveting gun". Figure 1 As shown in the literature: Cao Zengqiang, Tao Hua, She Gongfan, Li Zhiyao, Sheng Xi, Stress wave riveting of large diameter riveting, New Process-New Technology-New Equipment, 1996.2, 27-28 [J]. The device includes a transformer 1, a rectifier silicon stack 2, a capacitor group 3, a vacuum switch 4, a buffer element 5, a primary coil 6, a secondary coil 7, a stress wave modulator 8, and a rivet 9. During the experiment, when the impact compression load is applied to the rivet 9, the transformer 1 is first turned on to charge the capacitor group 3, and when the voltage reaches a predetermined value, the vacuum switch 4 is turned on. When the transient large current passes through the primary coil 6, magnetic induction and eddy current are generated in the secondary coil 7, forming a Lorentz force that in turn acts on the primary coil 6, so that the secondary coil 7 generates an enhanced stress pulse on the stress wave modulator 8, acts on the rivet 9 and compresses and deforms, thereby realizing the impact loading on the rivet 9.

[0004] The prior art discloses an electromagnetic Hopkinson pressure bar loading method. Figure 2As shown, the literature: Wang Yuchen, Liu Xiaoyan, Huang Yiyun, Guan Rui, Jiang Jiafu, Design and Experiment of Hopkinson Rod Electromagnetic Loading System, High Power Laser and Particle Beams, Vol. 34, No. 7, July 2022, 075009-1-6 [J]. The device includes a compression specimen 10, a compression incident rod 11, a compression transmission rod 12, a capacitor group 13, an effective coil 14, an induction coil 15, and a stress wave amplifier 16. This method is based on the traditional Hopkinson compression rod principle, and transforms the impact rod loading into a "stress wave riveting gun" loading. During the experiment, the stress wave amplifier 16 generates an enhanced stress pulse to load the compression specimen 10 along the compression incident rod 11. Strain gauges are attached to the compression incident rod 11 and the compression transmission rod 12 to obtain the impact loading process signal.

[0005] The prior art discloses a pneumatically controlled repeated impact compression loading device system, which can realize repeated impact compression of cylindrical specimens. Figure 3 As shown in the literature: M. Isakov, Cyclic Impact Test with the Hopkinson Bar: Application to Granite, Journal of Dynamic Behavior of Materials (2024) 10: 75–91 [J]. The device includes a high-pressure gas cylinder 17, an impact rod 18, a variable diameter rod 19, a compression specimen 20, a No. 1 strain gauge 21, a compression incident rod 22, a No. 2 strain gauge 23, an energy absorption rod 24, and a pneumatic stopper 25. Figure 3 The following schematic diagram shows the working order of each part when the impact rod moves for one loading. Blue represents low pressure, magenta represents medium pressure, and red represents high pressure. The experimental process is that when the air pressure enters the high-pressure gas cylinder 17, it pushes the impact rod 18 to hit the variable diameter rod 19, generating an impact signal to act on the compression sample 20. The No. 1 strain gauge 21 and the No. 2 strain gauge 23 collect data and serve as pneumatic control signals. The high-pressure gas cylinder 17 and the pneumatic stopper 25 are designed with different variable diameter forms to achieve limit and single impact single loading of the sample. The system can use electromagnetic switch valves and controllers to achieve repeated impact loading.

[0006] The three test methods mentioned above include Figure 1 This "stress wave riveting gun" can achieve impact compression on rivets or specimens, but it cannot display the shock wave configuration, nor can it quantify the impact force. It cannot be directly used as an experimental device for dynamic experimental performance testing of materials. Figure 2 This Hopkinson rod electromagnetic loading system basically meets the experimental device requirements for single impact compression loading, but it belongs to the impact compression mode and does not constitute repeated cyclic loading. Figure 3This cyclic impact compression loading experimental device is for repeated impact loading of the sample. During the impact loading, the stress wave pulse is transmitted back and forth in the rod. Due to the material dispersion and geometric characteristics of the loading rod, the stress wave will continue to decay back and forth. Before the next loading, it is necessary to wait for the repeated transmission of the stress wave to decay. Therefore, it is also necessary to consider preventing the subsequent reflected stress wave pulse from being loaded twice, so as to achieve a single impact loading on the sample.

[0007] In summary, in order to solve the problem of repeated impact loading of tensile test, avoid multiple loading of specimens under impact loading and the problem that the instrument cannot be automated, it is necessary to build an instrumented automatic experimental system. Summary of the invention

[0008] In order to overcome the shortcomings of the prior art, the present invention provides an all-electric measurement and control instrumented tensile impact fatigue test system to achieve automation and instrumentation of the tensile impact fatigue system. The Hopkinson pull rod system, stress wave riveting gun module, screw dragger, integrated detection and controller, etc. are used to achieve single repeated impact loading of the specimen, solving the problem of repeated tensile impact loading, avoiding multiple loading of the specimen under impact loading, and the problem that the instrument cannot be automated.

[0009] An all-electric measurement and control instrumented tensile impact fatigue test system includes a pulse emission module, a sample loading module, a screw dragger 41 and a metal screw; the pulse emission module includes a stress wave riveting gun module and a pulse emission control circuit; the sample loading module is a Hopkinson pressure rod; the sample loading module includes a tensile incident rod 48, a tensile transmission rod 42, a dumbbell-shaped sample 46 and a damping module; the damping module includes an energy absorber and limiter 38 and a damping blocker 39; the screw dragger 41 includes a screw drive motor and an LVDT linear displacement differential transformer 40;

[0010] The stress wave riveting gun module includes a buffer element 32, a primary coil 33, a secondary coil 34 and a stress wave modulator 35; the buffer element 32, the primary coil 33 and the secondary coil 34 are all the same hollow cylinders; the stress wave modulator 35 is a cone; the bottom radius of the stress wave modulator 35 is the same as the bottom radius of the secondary coil 34; the stress wave modulator 35 is provided with a through hole along the axial direction; the radius of the through hole is the same as the inner ring radius of the secondary coil 34; based on a bottom surface of the buffer element 32, the primary coil 33, the secondary coil 34 and the stress wave modulator 35 are arranged in sequence; after the buffer element 32, the primary coil 33, the secondary coil 34 and the stress wave modulator 35 are combined, the buffer element 32, the primary coil 33, the secondary coil 34 and the stress wave modulator 35 are coaxial; the through hole is connected with the inner ring of the buffer element 32, the inner ring of the primary coil 33 and the inner ring of the secondary coil 34 to form a through hole; the primary coil 33 is connected to the pulse emission control circuit;

[0011] The pulse emission control circuit includes a transformer 26, a rectifier silicon stack 27, a charging voltage detector 28, a vacuum switch 29, a voltage-time switch 30 and a capacitor group 31; one end of the vacuum switch 29 is connected to the primary coil 33; the other end of the vacuum switch 29 is connected to the charging voltage detector 28; the other end of the charging voltage detector 28 is respectively connected to one end of the rectifier silicon stack 27 and one end of the capacitor group 31; the other end of the rectifier silicon stack 27 is connected to the transformer 26; the other end of the transformer 26 is connected to the voltage-time switch 30; the other end of the capacitor group 31 is respectively connected to the voltage-time switch 30 and the primary coil 33;

[0012] The tensile incident rod 48 is horizontally arranged in the through hole; the end face of the tensile incident rod 48 close to the top of the stress wave modulator 35 is provided with a flange 36; the damping blocker 39 is cylindrical; the damping blocker 39 is fixed on the experimental frame; the energy absorber and stopper 38 is arranged in the damping blocker 39; the energy absorber and stopper 38 is a metal rod; a gap is arranged between the flange 36 and the energy absorber and stopper 38; the length of the gap is △;

[0013] One end of the stretch transmission rod 42 is connected to the dumbbell-shaped sample 46; the other end of the stretch transmission rod 42 is fixedly connected to one end of the metal screw; the other end of the metal screw is fixedly connected to the screw dragger 41; the LVDT linear displacement differential transformer 40 and the screw dragger 41 are both fixed on the experimental frame; after the LVDT linear displacement differential transformer 40, the screw dragger 41 and the sample loading module are installed, the stretch transmission rod 42, the dumbbell-shaped sample 46, the stretch incident rod 48, the metal screw and the energy absorption and limiter 38 are collinear.

[0014] Furthermore, a thread is arranged inside the damping blocker 39; the energy absorber and limiter 38 is fixedly connected to the damping blocker 39 via a thread; after the energy absorber and limiter 38 are arranged inside the damping blocker 39, energy-absorbing material is filled inside the damping blocker 39; the energy absorber and limiter 38 are coaxial.

[0015] Furthermore, the end surface of the tensile incident rod 48 connected to the dumbbell-shaped sample 46 is provided with an incident rod trapezoidal groove 47; the incident rod trapezoidal groove 47 is a quadrangular pyramid; the bottom surface of the incident rod trapezoidal groove 47 with the smallest area is the end surface of the tensile incident rod 48; the bottom surface and one side surface of the incident rod trapezoidal groove 47 with the smallest area are open; the dumbbell-shaped sample 46 is arranged in the incident rod trapezoidal groove 47; one end of the dumbbell-shaped sample 46 is arranged in the incident rod trapezoidal groove 47; the other end of the dumbbell-shaped sample 46 is arranged in the transmission rod trapezoidal groove of the tensile transmission rod 42 The groove 45 is a quadrangular pyramid; the bottom surface of the transmission rod trapezoidal groove 45 with the smallest area is the end surface of the stretched transmission rod 42; the bottom surface and one side surface of the transmission rod trapezoidal groove 45 with the smallest area are open; after the two ends of the dumbbell-shaped sample 46 are respectively placed in the transmission rod trapezoidal groove 45 and the incident rod trapezoidal groove 47, a sample gap is set between the bottom surface of the transmission rod trapezoidal groove 45 with the largest area and the end of the dumbbell-shaped sample 46, and a sample gap is set between the bottom surface of the incident rod trapezoidal groove 47 with the largest area and the end of the dumbbell-shaped sample 46.

[0016] Furthermore, the length of the energy absorber and stopper 38 is greater than the wavelength of the stress wave generated by the system.

[0017] Furthermore, the length △ of the gap is calculated in advance according to the stretched impact waveform.

[0018] Furthermore, a gap photodetector 37 is disposed directly above the gap.

[0019] Furthermore, a No. 1 strain gauge 43 is disposed on the stretching transmission rod 42 ; and a No. 2 strain gauge 49 is disposed on the stretching incident rod 48 .

[0020] Furthermore, the instrumented tensile impact fatigue test system with all-electric measurement and control includes an automatic control module and a data acquisition module; the automatic control module includes a comprehensive detection and controller 50 and a peak detector 53; the comprehensive detection and controller 50 is a computer; the comprehensive detection and controller 50 is respectively connected to the screw dragger 41, the voltage-time switch 30, the gap photoelectric detector 37, the charging voltage detector 28 and the vacuum switch 29; the peak detector 53 is connected to the LVDT linear displacement differential transformer 40; used to control the experimental system, through the electrical signal control After loading, the transmission rod and the sample are reset to ensure single loading of the sample; the data acquisition module includes an ultra-dynamic strain gauge 54, a peak detector 53, a voltage comparator 52 and a PID regulator 51; the No. 1 strain gauge 43 is connected to the ultra-dynamic strain gauge 54; the No. 2 strain gauge 49 is connected to the ultra-dynamic strain gauge 54; the ultra-dynamic strain gauge 54, the peak detector 53, the voltage comparator 52 and the PID regulator 51 are all connected to the comprehensive detection and controller 50; the collected data is used to collect impact force waveform, amplitude, displacement value, number of impacts and frequency data in real time;.

[0021] Furthermore, a rubber sleeve 44 is provided on the stretching incident rod 48 to prevent the sample from falling.

[0022] Furthermore, the primary coil 33 and the secondary coil 34 are both wire windings; the material of the stress wave modulator 35 is steel; the material of the buffer element 32 is a polymer material and steel, and the polymer material is coated inside the steel; the energy absorbing material is plasticine or lead.

[0023] Furthermore, the energy absorber and stopper 38, the stretch transmission rod 42 and the stretch incident rod 48 are made of titanium alloy or aluminum alloy.

[0024] The beneficial effects of the present invention are:

[0025] 1) The present invention proposes a high strain rate impact tensile fatigue test system with full electric drive, detection and control, which realizes the instrumentation and full automation of impact tensile fatigue test;

[0026] 2) The present invention adopts a hook-type tensile specimen, the specimen is connected to the end of the slotted loading rod, and the single loading impact fatigue function of the specimen is achieved by continuous tensile impact through energy absorption and limiter 38 and screw dragger 41;

[0027] 3) The present invention designs a closed-loop control of impact fatigue, including closed-loop control of impact force and displacement, to achieve stable amplitude of impact force and displacement during impact fatigue;

[0028] 4) The present invention adopts a large current electro-magnetic "stress wave riveting gun" to generate a semi-sine impact tensile pulse with high impact energy and large impact force. By detecting the electrical signals of force and displacement during the impact fatigue process, the sample loading is displayed and controlled in real time, achieving fast electrical measurement and control response, high synchronization and good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of stress wave riveting of large diameter riveting proposed in Background Art Reference 1;

[0030] Figure 2 It is the design and experimental schematic diagram of the Hopkinson rod electromagnetic loading system in the background technology reference 2;

[0031] Figure 3 is a schematic diagram of a cyclic impact compression loading experimental system in Background Art Reference 3;

[0032] Figure 4 It is a schematic diagram of an instrumented tensile impact fatigue test system with full electrical measurement and control;

[0033] Figure 5 Schematic diagram of the trapezoidal groove of the transmission rod and the trapezoidal groove of the incident rod;

[0034] Explanation of reference numerals: 1-transformer; 2-rectifier silicon stack; 3-capacitor group; 4-vacuum switch; 5-buffer element; 6-primary coil; 7-secondary coil; 8-stress wave modulator; 9-rivet; 10-compression specimen; 11-compression incident rod; 12-compression transmission rod; 13-capacitor group; 14-effective coil; 15-induction coil; 16-stress wave amplifier; 17-high-pressure gas cylinder; 18-impact rod; 19-diameter reducing rod; 20-compression specimen; 21-No. 1 strain gauge; 22-compression incident rod; 23-No. 2 strain gauge; 24-energy absorption rod; 25-pneumatic stopper; 26-transformer; 27-rectifier silicon stack; 28-charging voltage detector; 29-vacuum switch; 30 -voltage-time switch; 31-capacitor group; 32-buffer element; 33-primary coil; 34-secondary coil; 35-stress wave modulator; 36-flange; 37-gap photoelectric detector; 38-energy absorber and limiter; 39-damping blocker; 40-LVDT linear displacement differential transformer; 41-screw dragger; 42-stretching transmission rod; 43-No. 1 strain gauge; 44-rubber sleeve; 45-transmission rod trapezoidal groove; 46-dumbbell-shaped specimen; 47-incident rod trapezoidal groove; 48-stretching incident rod; 49-No. 2 strain gauge; 50-integrated detection and controller; 51-PID regulator; 52-voltage comparator; 53-peak detector; 54-ultra-dynamic strain gauge. DETAILED DESCRIPTION

[0035] The technical solution adopted by the present invention is:

[0036] An all-electric measurement and control instrumented tensile impact fatigue test system includes a pulse emission module, a sample loading module, an automatic control module and a data acquisition module;

[0037] The pulse emission module includes a stress wave riveting gun module and a pulse emission control circuit; the stress wave riveting gun module includes a buffer element 32, a primary coil 33, a secondary coil 34 and a stress wave modulator 35; the buffer element 32, the primary coil 33 and the secondary coil 34 are all the same hollow cylinders; the stress wave modulator 35 is a cone; the bottom radius of the stress wave modulator 35 is the same as the bottom radius of the secondary coil 34; the stress wave modulator 35 is provided with a through hole along the axial direction; the through hole The radius of the hole is the same as the inner ring radius of the secondary coil 34; based on a bottom surface of the buffer element 32, the primary coil 33, the secondary coil 34 and the stress wave modulator 35 are arranged in sequence; after the buffer element 32, the primary coil 33, the secondary coil 34 and the stress wave modulator 35 are combined, the buffer element 32, the primary coil 33, the secondary coil 34 and the stress wave modulator 35 are coaxial; the through hole is connected with the inner ring of the buffer element 32, the inner ring of the primary coil 33 and the inner ring of the secondary coil 34 to form a through hole;

[0038] The primary coil 33 is connected to the pulse emission control circuit;

[0039] The pulse emission control circuit includes a transformer 26, a rectifier silicon stack 27, a charging voltage detector 28, a vacuum switch 29, a voltage-time switch 30 and a capacitor group 31; one end of the vacuum switch 29 is connected to the primary coil 33; the other end of the vacuum switch 29 is connected to the charging voltage detector 28; the other end of the charging voltage detector 28 is respectively connected to one end of the rectifier silicon stack 27 and one end of the capacitor group 31; the other end of the rectifier silicon stack 27 is connected to the transformer 26; the other end of the transformer 26 is connected to the voltage-time switch 30; the other end of the capacitor group 31 is respectively connected to the voltage-time switch 30 and the primary coil 33;

[0040] The sample loading module is a Hopkinson pressure rod; the sample loading module includes a tensile incident rod 48, a tensile transmission rod 42, a dumbbell-shaped sample 46, an energy absorber and stopper 38 and a damping blocker 39; the tensile incident rod 48 is horizontally arranged in the through hole; a flange 36 is arranged on the end face of the tensile incident rod 48 close to the top of the stress wave modulator 35; the damping blocker 39 is cylindrical; the damping blocker 39 is fixed on the experimental frame; a thread is arranged in the damping blocker 39; the energy absorber and stopper 38 is arranged in the damping blocker 39; the energy absorber and stopper 38 is fixedly connected to the damping blocker 39 through a thread; after the energy absorber and stopper 38 is arranged in the damping blocker 39, the damping blocker 39 is filled with energy absorbing material; the energy absorbing material is plasticine or lead; the energy absorber and stopper 38 are coaxial;

[0041] Another end face machine of the stretched incident rod 48 is provided with an incident rod trapezoidal groove 47; the incident rod trapezoidal groove 47 is a quadrangular pyramid; the bottom surface of the incident rod trapezoidal groove 47 with the smallest area is the end surface of the stretched incident rod 48; the bottom surface and one side surface of the incident rod trapezoidal groove 47 with the smallest area are open; a dumbbell-shaped sample 46 is provided in the incident rod trapezoidal groove 47; one end of the dumbbell-shaped sample 46 is provided in the incident rod trapezoidal groove 47; the other end of the dumbbell-shaped sample 46 is provided in the transmission rod trapezoidal groove 45 of the stretched transmission rod 42; the transmission rod trapezoidal groove 45 is provided at one end of the stretched transmission rod 42; the other end of the stretched transmission rod 42 is fixedly connected to a metal screw; the metal screw and the screw dragger 4 1 fixed connection; the transmission rod trapezoidal groove 45 is a quadrangular pyramid; the bottom surface with the smallest area of ​​the transmission rod trapezoidal groove 45 is the end surface of the stretched transmission rod 42; the bottom surface and one side surface with the smallest area of ​​the transmission rod trapezoidal groove 45 are open; after the two ends of the dumbbell-shaped sample 46 are respectively placed in the transmission rod trapezoidal groove 45 and the incident rod trapezoidal groove 47, a sample gap is set between the bottom surface with the largest area of ​​the transmission rod trapezoidal groove 45 and the end of the dumbbell-shaped sample 46, and a sample gap is set between the bottom surface with the largest area of ​​the incident rod trapezoidal groove 47 and the end of the dumbbell-shaped sample 46, thereby allowing the dumbbell-shaped sample 46 to have sufficient movement space during compression loading, not constituting a compression mode, and preventing accidental secondary tensile loading.

[0042] The screw dragger 41 includes a screw drive motor and an LVDT linear displacement differential transformer 40; the LVDT linear displacement differential transformer 40 is used for screw motion displacement measurement; the LVDT linear displacement differential transformer 40 and the screw dragger 41 are both fixed on the experimental frame;

[0043] After the LVDT linear displacement differential transformer 40, the screw dragger 41 and the sample loading module are installed, the stretch transmission rod 42, the dumbbell-shaped sample 46, the stretch incident rod 48 and the energy absorber and stopper 38 are in line; a gap is set between the flange 36 and the energy absorber and stopper 38; the length of the gap is △; a gap photoelectric detector 37 is set directly above the gap; the length △ of the gap is calculated in advance according to the stretching impact waveform and is a known quantity;

[0044] The stretch transmission rod 42 is provided with a No. 1 strain gauge 43; the stretch incident rod 48 is provided with a No. 2 strain gauge 49;

[0045] The automatic control module includes an integrated detection and controller 50 and a peak detector 53; the integrated detection and controller 50 is a computer; the integrated detection and controller 50 is respectively connected to the screw dragger 41, the voltage-time switch 30, the gap photoelectric detector 37, the charging voltage detector 28 and the vacuum switch 29; the peak detector 53 is connected to the LVDT linear displacement differential transformer 40; it is used to control the experimental system, reset the transmission rod and the sample after loading through electrical signal control, and ensure single loading of the sample;

[0046] The data acquisition module includes an ultra-dynamic strain gauge 54, a peak detector 53, a voltage comparator 52 and a PID regulator 51; the No. 1 strain gauge 43 is connected to the ultra-dynamic strain gauge 54; the No. 2 strain gauge 49 is connected to the ultra-dynamic strain gauge 54; the ultra-dynamic strain gauge 54, the peak detector 53, the voltage comparator 52 and the PID regulator 51 are all connected to the comprehensive detection and controller 50; the collected data is used to collect the impact force waveform, amplitude, displacement value, impact number and frequency data in real time;

[0047] A rubber sleeve 44 is provided on the stretching incident rod 48 to prevent the sample from falling;

[0048] The buffer element 32 is made of polymer material and steel, and the polymer material is coated inside the steel;

[0049] The primary coil 33 and the secondary coil 34 are both wire windings;

[0050] The material of the stress wave modulator 35 is steel;

[0051] The length of the energy absorber and stopper 38 is greater than the wavelength of the stress wave generated by the system;

[0052] The energy absorber and stopper 38 , the stretch transmission rod 42 and the stretch incident rod 48 are made of titanium alloy or aluminum alloy.

[0053] The present invention is based on the principle of traditional high strain rate direct tension Hopkinson rod, and transforms the stress wave modulator 8 of the stress wave riveting gun module in the prior art 1 into a coaxial hollow mode, allowing the non-magnetic Hopkinson incident rod to pass through, achieving high energy and high impact force, having an idealized semi-sinusoidal impact force waveform, and can be controlled by a computer.

[0054] The solid cones of the primary coil 33, the secondary coil 34 and the stress wave modulator 35 in the stress wave riveting gun module are changed into coaxial circular holes with an inner diameter of 14.1 mm, and a round straight rod with a diameter of 14 mm and a length of 1400 mm is used as the tensile incident rod 48, with a flange 36 with a thickness of 5 mm and an outer diameter of 24 mm left at one end. After the tensile incident rod 48 passes through the coaxial circular hole, the flange 36 contacts the cone head end of the "stress wave riveting device". In order to avoid electromagnetic influence, the rod is made of non-magnetic material, such as titanium alloy, so that the impact pulse generated by the "stress wave riveting device" directly acts on the flange 36 of the tensile incident rod 48, generating a tensile pulse in the tensile incident rod 48.

[0055] The dumbbell-shaped specimen is hooked and connected with a tensile incident rod and a transmission rod with a slot to withstand tensile loading instead of compressive loading; an energy absorber and limiter is set at the end of the incident rod flange to limit the deformation of the incident rod loading, and the loading rod end with a slot is connected with the hooked tensile specimen to achieve single single pulse impact loading; an electric lead screw with a displacement measurement LVDT is arranged at the end of the transmission rod to achieve the reset of the transmission rod after loading, so as to control the displacement during the impact fatigue process.

[0056] In order to achieve single impact and single loading and prevent accidental secondary tensile loading, the tensile specimen is designed as a dumbbell-shaped specimen 46. The two ends of the specimen are similar to trapezoidal or wedge-shaped bodies without threads. The connection between the tensile incident rod 48 and the tensile transmission rod 42 and the specimen is changed to a hook form, and the incident rod trapezoidal groove 47 and the transmission rod trapezoidal groove 45 are used to connect with the specimen. A gap is left at the bottom of the rod hook slot to allow the dumbbell-shaped specimen 46 to have enough movement space during compression loading and not constitute a compression mode. In order to prevent the specimen from sliding out of the notch during impact fatigue, an elastic rubber sleeve 44 is installed at the end of the trapezoidal notch rod for protection, such as Figure 5 shown.

[0057] Outside the flange 36 of the stretching incident rod 48, a solid rod with a diameter of 14 mm and a length of about 400 mm is set. The material is the same as that of the stretching incident rod 48, and it serves as the energy absorber and limiter 38. It is connected to the damping blocker 39 using threads and locked with a self-locking pin. When the stretching loading pulse is reflected as a stretching pulse for the second time in the stretching incident rod 48, there is no gap △ between the flange 36 and the energy absorber and limiter 38. Therefore, when the secondary stretching pulse enters the energy absorber and limiter 38, the stretching incident rod 48 has no secondary stretching loading pulse.

[0058] A lead screw dragger 41 is provided at the end of the stretching transmission rod 42, and is equipped with an LVDT linear displacement differential transformer 40 for measuring the lead screw displacement. The lead screw dragger 41 allows the lead screw to freely extend and move toward the sample direction, and drags the stretching transmission rod 42 to move in the opposite direction of the sample under electrical control, so that the sample is tightly combined with the stretching incident rod 48 and the stretching transmission rod 42 to withstand the stretching impact load.

[0059] In order to achieve single loading, the stress wave riveting gun module generates a tensile pulse in the tensile incident rod 48. The rod and the sample tend to move to the right end in a unified manner. When the tensile pulse is reflected at the free end to form a compression pulse, it is transmitted to the flange 36 and then reflected to form a tensile pulse. The originally reserved gap △ disappears, causing the stress wave pulse of the tensile incident rod 48 to move to the right to be transmitted to the energy absorber and limiter 38 through the flange 36, that is, the tensile incident rod 48 has no secondary tensile loading pulse.

[0060] The primary impact load is transmitted to the shorter tensile transmission rod 42, and the stress wave is transmitted back and forth in the rod, causing the rod to move toward the sample, resulting in the sample being out of contact with the rod hook and not being subjected to the secondary tensile load.

[0061] After the stress wave is transmitted back and forth between the two rods, the screw dragger 41, under the electric drive instruction, drags the stretch transmission rod 42, the dumbbell-shaped sample 46 and the stretch incident rod 48 into close contact to meet the next impact loading, and continues to repeat this process, which is the impact fatigue loading cycle.

[0062] The strain signals of the transmission rod and the incident rod are collected, and the strain signals are amplified by the dynamic strain gauge. At the same time, the signals pass through the peak detector and the voltage comparator: During the impact fatigue loading cycle, the tensile force acting on the sample will change due to the decrease in the damage stiffness of the sample. At this time, the comparator outputs the signal to the comprehensive detection and controller, and the closed-loop adjustment of the capacitor charging voltage of the stress wave enhancement cone head is carried out, thereby adjusting the loading load and realizing closed-loop control to maintain a stable impact force amplitude.

[0063] The measured signals of the No. 1 strain gauge 43 and the No. 2 strain gauge 49 are respectively introduced into the super dynamic strain gauge 54, the peak detector 53 and the voltage comparator 52 for comparison with the predetermined value. If the amplitude of the impact force signal of the tensile incident rod 48 or the tensile transmission rod 42 decreases, the voltage is adjusted through the voltage comparator 52 and the PID regulator 51. At this time, the comprehensive detection and controller 50 outputs a command signal to adjust the voltage-time switch 30 of the "stress wave riveting device". The higher the increased voltage signal, the longer the time relay switch is closed and charged, so that the required voltage of the capacitor bank 31 can reach a higher level. When the vacuum switch 29 is controlled to be turned on, the impact loading pulse amplitude of the closed loop correction is generated in the tensile transmission rod 42. During the experiment, the gap △ between the flange 36 and the energy absorber and stopper 38 is detected by the gap photoelectric detector 37. If there is a change, the comprehensive detection and controller 50 issues an indication and warning.

[0064] Maintaining the impact displacement: During the impact fatigue process, in order to monitor the displacement change of the sample, or to perform an impact fatigue test of the tensile displacement, the screw dragger 41 is equipped with an LVDT linear displacement differential transformer 40 to output a displacement signal. This signal is converted from AC to DC and peak value detected, and sent to a comparator for comparison with a predetermined displacement value. If the amplitude changes during loading, the comparator outputs an increase or decrease difference to the PID regulator 51, and then to the comprehensive detection and controller 50. This controller outputs a voltage-time switch 30 that controls the "stress wave riveting device" to control the charging time so that the capacitor bank 31 is charged to the required voltage, thereby achieving a closed-loop displacement control method.

[0065] To realize the display and indication of impact force, impact waveform and impact number: drag the strain gauge detection signal on the stretching transmission rod 42 and the stretching incident rod 48 to introduce it into the comprehensive detection and controller 50. The comprehensive detection and controller 50 has waveform display, peak value and impact number counting and display functions. At the same time, the impact number can be preset, and the experiment will be stopped when the preset number of times is reached.

[0066] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0067] Reference Figure 4 ,

[0068] 1) A stress wave riveting gun module is used as a source of high strain rate impact tensile pulses. The buffer element 32, the primary coil 33, the secondary coil 34 and the stress wave modulator 35 are integrally made into a gun head with a 14.1 mm coaxial through hole on the central axis. The outer diameter of the cone head end of the stress wave modulator 35 is 24 mm. The stress wave riveting gun module can generate a peak force of 10 kN and a stress wave pulse width of no more than 200 μs.

[0069] 2) The standard rod loading method of the traditional direct tensile Hopkinson rod is used for reference and modified. A tensile incident rod 48 with a diameter of 14 mm and a length of 1400 mm is made of titanium alloy. One end of the rod is made into a flange 36 with a thickness of 5 mm and an outer diameter of 24 mm, and the other end is made into a groove with a width of 8 mm and a depth of 10 mm. The rod end face is a trapezoidal notch that can hook the tensile specimen; the tensile transmission rod 42 has a diameter of 14 mm and a length of 1000 mm. The rod end slot is the same as the tensile incident rod 48, and the other end is left with a M5 threaded hole with a depth of 15 mm; and another energy absorber and stopper 38 with a diameter of 14 mm and a length of 600 mm is made, with an M14 thread left at one end of the rod. The titanium alloy materials of these rods are non-magnetic. In addition, the specimen for high strain rate impact tensile fatigue needs to be made into a dumbbell-shaped specimen 46, that is, the diameter of the central rectangular section of the specimen is 5 mm, or it is a plate-shaped with a width of 5 mm. The two ends of the specimen are made into a trapezoidal shape and hooked and connected to the trapezoidal grooves of the tensile incident rod 48 and the tensile transmission rod 42. A rubber sleeve 44 is covered on the hook groove part to prevent the specimen from slipping out of the rod groove when being stretched.

[0070] 3) On a horizontal heavy-duty support with a table width of 200 mm and a length of 3500 mm, follow the Figure 4 The layout of the stress wave riveting gun module, the tensile incident rod 48, the dumbbell-shaped specimen 46, the tensile transmission rod 42 and the energy absorber and stopper 38 are installed on the same axis. The flange 36 of the tensile incident rod 48 is in close contact with the cone head end of the stress wave modulator 35, and a △ gap is left with the energy absorber and stopper 38. This gap can be calculated in advance according to the required tensile impact waveform and is a known quantity. The end where the M14 thread of the energy absorber and stopper 38 is located is thread-locked with a damping blocker 39. The thread cannot be loosened during the impact test, and the damping blocker 39 is fixedly connected to the overall frame. The other end of the tensile transmission rod 42 is connected to the screw dragger 41 through an M5 metal screw. The dragger is equipped with a screw drive motor and an LVDT linear displacement differential transformer 40 for measuring the screw motion displacement.

[0071] 4) The outer surfaces of the tensile incident rod 48 and the tensile transmission rod 42 at half the length are respectively affixed with a No. 2 strain gauge 49 and a No. 1 strain gauge 43. 5AA high-precision strain gauges are used, and two are affixed symmetrically on the outer surfaces of the rods with epoxy glue. These strain gauges are connected in a full-bridge manner and then connected to the ultra-dynamic strain gauge 54, the peak detector 53, the voltage comparator 52, the PID regulator 51 and the comprehensive detection and controller 50. The output of the LVDT linear displacement differential transformer 40 is also introduced into the peak detector 43, the voltage comparator 52, the PID regulator 51 and the comprehensive detection and controller 50. The voltage and charging voltage of the voltage comparator 52, the counter, the force and displacement waveforms, etc. are all displayed on the computer display screen of the comprehensive detection and controller 50.

[0072] 5) A voltage-time switch 30 is installed in the charging circuit part of the stress wave riveting gun module. The voltage of this switch controls the connection circuit, that is, different voltages correspond to different connection times, and a charging voltage detector 28 is also installed.

[0073] Tensile impact fatigue test steps:

[0074] Step 1: See Figure 4 The dumbbell-shaped sample 46 is loaded into the slots of the tensile incident rod 48 and the tensile transmission rod 42, and is sealed with a rubber sleeve 44 to prevent both ends of the sample from slipping out of the slots. The rubber sleeve is non-metallic and elastic, and does not affect the transmission of stress wave signals during the impact process.

[0075] The second step: operate the integrated detection and controller 50 in computer mode to make the screw dragger 41 tighten the stretched transmission rod 42, the dumbbell-shaped sample 46 and the stretched incident rod 48, that is, set a very small tensioning force F in advance in the integrated detection and controller 50 as a criterion for tensioning. At the same time, the LVDT linear displacement differential transformer 40 attached to the screw dragger 41 records the displacement value of tensioning, and clears this value as the zero point of displacement. The displacement value can be displayed in real time in the integrated detection and controller 50.

[0076] Step 3: According to the impact force signal required for the dynamic impact of the sample, it is output to the integrated detection and controller 50, and the size of the gap △ can be calculated. Based on the flange 36 of the stretched incident rod 48, the energy absorber and limiter 38 and the damping blocker 39 are adjusted to lock the block and leave a gap △.

[0077] Step 4: The voltage value of the capacitor group 31 is calculated through the impact force signal input by the comprehensive detection and controller 50 in the previous step. At the same time, the impact frequency is input into the comprehensive detection and controller 50. The waveform real-time display mode can display the waveform of the No. 1 strain gauge 43 and the No. 2 strain gauge 49 and the detection in real time.

[0078] Step 5: The start-up test begins. After the first impact, the voltage comparator 32 and the integrated test and controller 50 compare the signal amplitudes of the No. 1 strain gauge 43 and the No. 2 strain gauge 49 with the preset value. If the conditions are met, the second impact test will be automatically continued according to the input impact frequency requirement; if not, the integrated test and controller 50 will output a command signal to the voltage-time switch 30, convert the voltage into the corresponding charging time, control the change of the charging time of the capacitor group 31, and then obtain the adjusted voltage, and send a command to the integrated test and controller 50 to continue the experiment.

[0079] Step 6: If the sample is broken, the impact displacement and impact force values ​​of protection are given in advance in the integrated detection and controller 50. For example, the deviation can be set to exceed a predetermined value of 50%, and the integrated detection and controller 50 will give a stop command. In addition, when you want to stop the experiment, press the stop button of the integrated detection and controller 50 to stop the experiment.

[0080] During the experiment, the impact force waveform, amplitude, displacement value, impact times, and frequency are all displayed in real time on the integrated detection and controller 50 .

[0081] The above is an impact force closed-loop control fatigue test. The impact displacement closed-loop control test process is the same, except that the force amplitude setting is changed to displacement control mode.

Claims

1. An all-electric measurement and control instrumented tensile impact fatigue test system, characterized by: The invention comprises a pulse emission module, a sample loading module, a screw dragger (41) and a metal screw; the pulse emission module comprises a stress wave riveting gun module and a pulse emission control circuit; the sample loading module is a Hopkinson pressure rod; the sample loading module comprises a tensile incident rod (48), a tensile transmission rod (42), a dumbbell-shaped sample (46) and a damping module; the damping module comprises an energy absorber and limiter (38) and a damping blocker (39); the screw dragger (41) comprises a screw drive motor and an LVDT linear displacement differential transformer (40); the stress wave riveting gun module comprises a buffer element (32), a primary coil (33), a secondary coil (34) and a stress wave modulator (35); the buffer element (32), the primary coil (33), and the secondary coil (34) are all the same hollow cylinders; the stress wave modulator (35) is a cone; the bottom radius of the stress wave modulator (35) is the same as the bottom radius of the secondary coil (34); the stress wave modulator (35) is provided with a through hole along the axial direction; the radius of the through hole is the same as the inner ring radius of the secondary coil (34); based on a bottom surface of the buffer element (32), the primary coil (33), the secondary coil (34) and the stress wave modulator (35) are provided in sequence; after the buffer element (32), the primary coil (33), the secondary coil (34) and the stress wave modulator (35) are combined, the buffer element (32), The primary coil (33), the secondary coil (34) and the stress wave modulator (35) are coaxial; the through hole is connected with the inner ring of the buffer element (32), the inner ring of the primary coil (33) and the inner ring of the secondary coil (34) to form a through hole; the primary coil (33) is connected to the pulse emission control circuit; the stretching incident rod (48) is horizontally arranged in the through hole; the end face of the stretching incident rod (48) close to the top of the stress wave modulator (35) is provided with a flange (36); the damping blocker (39) is cylindrical; the damping blocker (39) is fixed on the experimental frame; the energy absorber and limiter (38) is arranged in the damping blocker (39); the energy absorber and limiter (38) is a metal rod; A gap is set between the flange (36) and the energy absorber and limiter (38); the length of the gap is △; one end of the stretching transmission rod (42) is connected to the dumbbell-shaped sample (46); the other end of the stretching transmission rod (42) is fixedly connected to one end of the metal screw; the other end of the metal screw is fixedly connected to the screw dragger (41); the LVDT linear displacement differential transformer (40) and the screw dragger (41) are both fixed on the experimental frame; after the LVDT linear displacement differential transformer (40), the screw dragger (41) and the sample loading module are installed, the stretching transmission rod (42), the dumbbell-shaped sample (46), the stretching incident rod (48), the metal screw and the energy absorber and limiter (38) are collinear.

2. The all-electrically controlled instrumented tensile impact fatigue testing system according to claim 1, characterized in that: A thread is provided in the damping blocker (39); the energy absorber and stopper (38) is fixedly connected to the damping blocker (39) via the thread; after the energy absorber and stopper (38) are provided in the damping blocker (39), the damping blocker (39) is filled with energy absorbing material; the energy absorber and stopper (38) are coaxial.

3. The all-electric measurement and control instrumented tensile impact fatigue testing system according to claim 1, characterized in that: The end surface of the tensile incident rod (48) connected to the dumbbell-shaped sample (46) is provided with an incident rod trapezoidal groove (47); the incident rod trapezoidal groove (47) is a quadrangular pyramid; the bottom surface of the incident rod trapezoidal groove (47) with the smallest area is the end surface of the tensile incident rod (48); the bottom surface and one side surface of the incident rod trapezoidal groove (47) with the smallest area are open; the dumbbell-shaped sample (46) is provided in the incident rod trapezoidal groove (47); one end of the dumbbell-shaped sample (46) is provided in the incident rod trapezoidal groove (47); the other end of the dumbbell-shaped sample (46) is provided in the transmission rod trapezoidal groove ( 45); the transmission rod trapezoidal groove (45) is a quadrangular pyramid; the bottom surface with the smallest area of ​​the transmission rod trapezoidal groove (45) is the end surface of the stretched transmission rod (42); the bottom surface with the smallest area of ​​the transmission rod trapezoidal groove (45) and one side surface are open; after the two ends of the dumbbell-shaped sample (46) are respectively placed in the transmission rod trapezoidal groove (45) and the incident rod trapezoidal groove (47), a sample gap is set between the bottom surface with the largest area of ​​the transmission rod trapezoidal groove (45) and the end of the dumbbell-shaped sample (46), and a sample gap is set between the bottom surface with the largest area of ​​the incident rod trapezoidal groove (47) and the end of the dumbbell-shaped sample (46).

4. The all-electric measurement and control instrumented tensile impact fatigue testing system according to claim 1, characterized in that: The length of the energy absorber and stopper (38) is greater than the wavelength of the stress wave generated by the system; the length Δ of the gap is calculated in advance based on the stretched impact waveform.

5. The all-electrically controlled instrumented tensile impact fatigue testing system according to claim 4, characterized in that: The pulse emission control circuit comprises a transformer (26), a rectifier silicon stack (27), a charging voltage detector (28), a vacuum switch (29), a voltage-time switch (30) and a capacitor group (31); one end of the vacuum switch (29) is connected to the primary coil (33); the other end of the vacuum switch (29) is connected to the charging voltage detector (28); the other end of the charging voltage detector (28) is respectively connected to one end of the rectifier silicon stack (27) and one end of the capacitor group (31); the other end of the rectifier silicon stack (27) is connected to the transformer (26); the other end of the transformer (26) is connected to the voltage-time switch (30); and the other end of the capacitor group (31) is respectively connected to the voltage-time switch (30) and the primary coil (33).

6. The all-electrically controlled instrumented tensile impact fatigue testing system according to claim 5, characterized in that: A gap photodetector (37) is provided just above the gap.

7. The all-electric measurement and control instrumented tensile impact fatigue testing system according to claim 6, characterized in that: A No. 1 strain gauge (43) is provided on the stretching transmission rod (42); and a No. 2 strain gauge (49) is provided on the stretching incident rod (48).

8. The all-electrically controlled instrumented tensile impact fatigue testing system according to claim 7, characterized in that: The instrumented tensile impact fatigue test system with full electric measurement and control comprises an automatic control module and a data acquisition module; the automatic control module comprises a comprehensive detection and controller (50) and a peak detector (53); the comprehensive detection and controller (50) is a computer; the comprehensive detection and controller (50) is respectively connected to a screw dragger (41), a voltage-time switch (30), a gap photoelectric detector (37), a charging voltage detector (28) and a vacuum switch (29); the peak detector (53) is connected to an LVDT linear displacement differential transformer (40); the data acquisition module comprises an ultra-dynamic strain gauge (54), a peak detector (53), a voltage comparator (52) and a PID regulator (51); the No. 1 strain gauge (43) is connected to the ultra-dynamic strain gauge (54); the No. 2 strain gauge (49) is connected to the ultra-dynamic strain gauge (54); the ultra-dynamic strain gauge (54), the peak detector (53), the voltage comparator (52) and the PID regulator (51) are all connected to the comprehensive detection and controller (50).

9. The all-electrically controlled instrumented tensile impact fatigue testing system according to claim 8, characterized in that: A rubber sleeve (44) is provided on the stretching incident rod (48) to prevent the sample from falling.

10. The all-electric measurement and control instrumented tensile impact fatigue test system according to claim 1, characterized in that: The primary coil (33) and the secondary coil (34) are both wire windings; the material of the stress wave modulator (35) is steel; the material of the buffer element (32) is a polymer material and steel, and the polymer material is coated inside the steel; the energy absorbing material is plasticine or lead.

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