Symmetrical force balance type high frequency impact device

Abstract

The application discloses a symmetrical force balance type high-frequency impact device and belongs to the technical field of mechanical performance testing. The device comprises a base, a test piece mounting table 2 located in the middle, a first impact assembly 3 and a second impact assembly 4 symmetrically distributed on both sides and a control system. The two impact assemblies are driven by linear driving units 31, the axes are collinear and the actions are synchronous. When working, the impact hammer heads 33 on both sides simultaneously accelerate to impact the test piece towards the center or simultaneously retreat in the reverse direction. The symmetrical action makes the reaction forces generated by the impact cancel each other out in the system, greatly reducing the vibration interference on the base and the foundation. The application adopts a voice coil motor or a linear motor to drive, can realize high-frequency and high-acceleration impact loading and is especially suitable for vibration fatigue and impact life test of contact net parts, and has the advantages of compact structure, high test precision and good self stability.

Description

Technical Field

[0001] This invention belongs to the technical field of mechanical performance testing equipment, specifically relating to a symmetrical force-balanced high-frequency impact device that utilizes the principle of momentum conservation to eliminate base vibration and is used for testing the impact resistance and fatigue performance of components. This invention is particularly suitable for high-frequency fretting wear and impact fatigue testing of electrified railway contact network components (such as droppers, positioners, cantilever support insulators, connecting clamps, etc.). Background Technology

[0002] With the rapid development of high-speed railway technology and the continuous increase in train speeds, the mechanical environment subjected to the overhead contact system is becoming increasingly harsh. Overhead contact system components must not only withstand static or quasi-static loads such as strong winds and icing, but also the severe impacts and high-frequency vibrations generated by the pantograph passing over at high frequencies. Therefore, realistically simulating these high-frequency impact conditions in a laboratory environment is crucial for ensuring railway safety.

[0003] Existing impact testing equipment mainly suffers from the following technical bottlenecks:

[0004] Severe vibration and noise pollution: Traditional drop-type or single-sided pneumatic piston-type impact tables generate enormous unidirectional impact reaction forces during operation. This not only produces unbearable industrial noise but also causes severe vibration of the test bench base. To secure the equipment, it is often necessary to excavate a foundation and pour several tons of concrete vibration isolation blocks, resulting in extremely high installation costs and making it impossible to deploy in ordinary floor laboratories.

[0005] Low frequency response: Due to the limitations of gas compressibility and valve response speed, pneumatic mechanisms can usually only achieve low-frequency impacts below 30Hz, making it difficult to simulate the fretting wear conditions of 100Hz or even higher frequencies generated when a train passes by at speeds above 300km / h on overhead contact line components.

[0006] Poor waveform control accuracy: The mechanical impact of the cam cannot arbitrarily change the impact waveform (such as sine wave, triangle wave, random wave), and mechanical wear causes the test accuracy to decrease over time, resulting in poor data repeatability.

[0007] Data distortion caused by eccentric loading: Unilateral impact will cause the specimen to generate a deflection torque at the moment of force application, resulting in uneven force on the specimen fixture. This will cause the test results to fail to reflect the impact resistance of the material itself, and may even cause the fixture to fail before the specimen.

[0008] Therefore, there is an urgent need to develop an impact testing device that can self-balance impact reaction force, requires no special foundation, and can achieve high-frequency precise loading. Summary of the Invention

[0009] The purpose of this invention is to provide a symmetrical force-balanced high-frequency impact device, which eliminates base vibration by using the momentum cancellation principle through bidirectional symmetrical drive and precise synchronous control, and realizes high-frequency and high-precision impact testing.

[0010] To achieve the above objectives, the present invention provides a symmetrical force-balanced high-frequency impact device, characterized in that it comprises: a base 1; a specimen mounting platform 2 disposed in the middle of the base 1 for fixing the specimen 100 to be tested; a first impact component 3 and a second impact component 4 symmetrically disposed on both sides of the specimen mounting platform 2; and a control system 5 for controlling the synchronous movement of the first impact component 3 and the second impact component 4; each of the first impact component 3 and the second impact component 4 includes a linear drive unit 31, a transmission shaft 32, and an impact hammer 33 located at the end of the transmission shaft; the impact axes of the first impact component 3 and the second impact component 4 are collinear and symmetrical about the central plane of the specimen mounting platform 2; the control system 5 controls the first impact component 3 and the second impact component 4 to reciprocate towards the specimen mounting platform 2 at the same frequency and phase, so that the impact hammers 33 on both sides simultaneously impact the specimen 100 to be tested or simultaneously reverse, using symmetrical reaction forces to counteract the horizontal vibrations received by the base 1.

[0011] Furthermore, the linear drive unit 31 is a voice coil motor or an electromagnetic linear motor, the mover of the voice coil motor is rigidly connected to the transmission shaft 32, and the stator is fixed on the base 1.

[0012] Furthermore, a floating damping mechanism is provided between the first impact component 3 and the second impact component 4 and the base 1; the floating damping mechanism includes a guide rail slider and a damping spring assembly, which allows the linear drive unit 31 to generate a small axial displacement when subjected to recoil force in order to absorb high-frequency aftershocks.

[0013] Furthermore, the test piece mounting platform 2 includes a double-sided clamp with two impact surfaces arranged back to back. The test piece 100 is clamped between the two impact surfaces, or the test piece 100 itself constitutes the impact subject.

[0014] Furthermore, the impact hammer head 33 is connected to the drive shaft 32 via a force sensor 7, which collects the impact force signal in real time and feeds it back to the control system 5.

[0015] Furthermore, it also includes a position adjustment mechanism. The first impact component 3 and the second impact component 4 are mounted on the base 1 through the position adjustment mechanism. The position adjustment mechanism is used to adjust the initial distance between the impact hammers 33 on both sides and the specimen mounting platform 2 to accommodate contact wire components of different sizes.

[0016] Furthermore, the linear drive unit 31 is provided with a forced air cooling heat sink, and a temperature sensor is provided inside the heat sink. When the coil temperature exceeds the threshold, the control system 5 reduces the impact frequency.

[0017] Furthermore, the control system 5 is equipped with a phase-locked module (PLL) to monitor and correct the phase difference between the first impact component 3 and the second impact component 4 in real time, ensuring that the phase synchronization error is less than 10 microseconds.

[0018] Furthermore, the front end of the impact hammer 33 is provided with a replaceable impact contact. The material hardness of the impact contact is higher than that of the test piece 100, and the shape of the impact contact is selected from one of planar, hemispherical, or conical.

[0019] Furthermore, the device is used for high-frequency fretting wear and impact fatigue testing of overhead contact line droppers, cantilever support insulators, or positioning clamps in electrified railways.

[0020] The present invention has the following beneficial effects:

[0021] 1) Zero vibration transmission: Based on the principle of conservation of momentum, the reaction force generated by the impact is internalized within the base, and theoretically the dynamic load on the foundation is zero, so the equipment can be placed directly on a regular experimental platform without the need for a special foundation.

[0022] 2) Ultra-high frequency testing capability: It abandons the bulky mechanical linkages and sluggish pneumatic components and adopts a direct drive method, which can easily achieve high frequency impacts above 200Hz, filling the gap in high frequency micro-motion testing equipment for contact wires.

[0023] 3) High test accuracy: Symmetrical loading eliminates the overturning moment of the specimen, ensuring that the specimen is in a pure compression or shear state, and the data is purer and more reliable. Attached Figure Description

[0024] Figure 1 This is a top view of the overall structure of the present invention;

[0025] Figure 2 This is a block diagram of the control system principle of the present invention;

[0026] Figure 3 This is a schematic diagram of the stress state when testing the contact wire droppers in Example 1.

[0027] Reference numerals: 1. Base; 2. Specimen mounting platform; 3. First impact assembly; 4. Second impact assembly; 7. Force sensor; 31. Linear drive unit; 32. Drive shaft; 33. Impact hammer; 100. Specimen to be tested. Detailed Implementation

[0028] The technical solutions will now be clearly, completely, and specifically described with reference to the accompanying drawings of the embodiments of the present invention. The described embodiments are only some embodiments of the present invention, and not all embodiments.

[0029] Example 1: Specific Mechanical Structure and Basic Performance Testing of the Device

[0030] like Figure 1 As shown, the present invention provides a symmetrical force-balanced high-frequency impact device, which mainly consists of a high-rigidity cast iron base 1, a central clamping platform, and two voice coil motor modules that are symmetrically arranged on the left and right.

[0031] 1) Mechanical Structure: The base 1 is made of QT500-7 ductile iron and integrally cast, with T-slots machined on the surface to facilitate the installation of slide rails. The drive units on both sides are water-cooled voice coil motors with a peak thrust of 2000N. The motor mover is supported by high-precision cross roller guides with an extremely low coefficient of friction (<0.003), ensuring that overheating does not occur during high-frequency motion.

[0032] 2) Heat dissipation design: Considering that high-frequency impacts will generate a lot of heat in the motor coils, this embodiment wraps aluminum alloy heat dissipation fins around the motor and is equipped with a forced air cooling system, with the temperature control threshold set at 70°C.

[0033] 3) Basic performance verification data:

[0034] Balance Test: Under no-load conditions, the impact frequency was set to 50Hz and the acceleration to 10g. The micro-displacement of base 1 was measured using a laser interferometer. Data showed that the amplitude of base 1 in the impact direction was only 1.2μm. In contrast, when one side of the motor was manually cut off (i.e., unilateral impact), the amplitude of base 1 instantly surged to 350μm, accompanied by loud noise. This fully demonstrates the effectiveness of the "symmetrical force balance" design of this invention, with a vibration reduction rate of over 99%.

[0035] Response speed: The control system adopts a sampling rate of 10kHz, and the step response time from issuing the command to the impact head reaching the maximum thrust is only 1.5ms, which meets the requirements of transient impact.

[0036] Example 2: High-cycle fatigue and fretting wear test of overhead contact line droppers

[0037] This embodiment demonstrates the use of this device to conduct accelerated life testing on the integral dropper, a core component of the high-speed rail overhead contact system.

[0038] 1) Test background: When a train passes by, the dropper is subjected to high-frequency tension and compression impacts in the vertical direction. Traditional equipment is difficult to simulate the pantograph excitation frequency of hundreds of times per second.

[0039] 2) Test configuration:

[0040] Fix the dropper wire clamp to the middle specimen mounting platform 2.

[0041] The impact hammers on both sides 33 have been replaced with wear-resistant contacts made of carbon sliding plate material similar to that of a pantograph.

[0042] The control system sets the impact waveform to a sine wave with a frequency of 120Hz (simulating high-order harmonic disturbance at a speed of 350km / h) and the peak impact force to 300N.

[0043] The phase-locked loop (PLL) synchronization module in the control system was activated to monitor the phase difference between the encoders of the two motors in real time.

[0044] 3) Objective test data and beneficial effects:

[0045] Ultra-long service life: The device operated continuously without failure for 72 hours, accumulating 31 million impact cycles. During this period, monitoring with a thermal imager showed that the motor coil temperature remained stable between 58℃ and 62℃, with no overheating shutdowns, proving that the device is suitable for long-term fatigue testing.

[0046] Synchronization accuracy data: Data logs show that during 31 million cycles, the time difference (synchronization error) between the left and right impact contacts on the specimen was consistently controlled within ±8μs (microseconds). This means that the specimen was always subjected to perfect symmetrical compression, without any left-right swaying caused by asynchrony on both sides, ensuring that the wear marks inside the dropper clamp were uniform and reliable.

[0047] Wear Feature Reproduction: After the test, scanning the inside of the clamp with an electron microscope revealed typical fretting wear characteristics, which were highly consistent with the microstructure of the failed component after 3 years of field service. In contrast, the control group tested using traditional low-frequency pneumatic equipment mainly exhibited plastic deformation rather than fretting wear. This demonstrates that the high-frequency characteristics of this invention are crucial for reproducing the actual failure mechanism.

[0048] Example 3: Destructive Impact Test and Safety Verification of Porcelain Insulators

[0049] This embodiment demonstrates the use of this device to perform ultimate failure testing on brittle materials.

[0050] 1) Test configuration:

[0051] The test specimen was a rod-shaped porcelain insulator sample with a diameter of 30 mm.

[0052] The impact mode has been adjusted to "single high-energy impact".

[0053] The impact hammers 33 on both sides were replaced with conical hardened steel heads to concentrate stress.

[0054] 2) Testing process:

[0055] The control system uses a supercapacitor to discharge instantaneously, driving the two motors to accelerate to a relative speed of 3 m / s within 10 milliseconds, instantly shattering the insulator upon impact.

[0056] 3) Objective test data and beneficial effects:

[0057] Safety data: At the instant the insulator shattered and broke apart, a high-speed camera (2000 frames / second) captured the fragments exhibiting a perfect "ring-shaped radial splash" pattern. This means the fragments primarily dispersed perpendicularly to the impact axis in all directions, without any kinetic energy propelling them axially. This is because the impact momentum from both sides canceled each other out at the center point, resulting in zero net momentum for the fragments. Combined with a transparent polycarbonate ring-shaped protective shield, all fragments were intercepted. Compared to the risk of fragments being ejected like bullets due to a unilateral impact, the safety of this invention is greatly improved.

[0058] Accurate determination of fracture energy: Based on the force-displacement curve fed back by the integral force sensor 7 mounted on the drive shaft 32, the system calculated the average fracture energy absorption of this batch of insulators to be 45.6J, with a standard deviation of only 1.2J. The data dispersion is extremely small (coefficient of variation CV < 3%), far superior to the traditional drop hammer test (usually CV > 10%), indicating that after eliminating the interference of base vibration and off-center load, the test data can better reflect the essential properties of the material.

[0059] In summary, this invention, through the combination of a symmetrical force balance structure and precision electronic control technology, successfully resolves the contradiction between high-frequency impact and base stability, and has extremely high application value in the research and quality inspection of contact network components.

Claims

1. A symmetrical force-balanced high-frequency impact device for high-frequency fretting wear and impact fatigue testing of overhead contact line droppers, cantilever support insulators, or positioning clamps in electrified railways, characterized in that, include: Base (1); The specimen mounting platform (2) is set in the middle of the base (1) to fix the specimen to be tested (100). A first impact assembly (3) and a second impact assembly (4) are symmetrically arranged on both sides of the specimen mounting platform (2). And a control system (5) for controlling the synchronous operation of the first impact component (3) and the second impact component (4); The first impact assembly (3) and the second impact assembly (4) each include a linear drive unit (31), a drive shaft (32) and an impact hammer (33) located at the end of the drive shaft (32); the impact axes of the first impact assembly (3) and the second impact assembly (4) are collinear and symmetrical about the central plane of the specimen mounting platform (2); The linear drive unit (31) is a voice coil motor or an electromagnetic linear motor. The mover of the linear drive unit (31) is rigidly connected to the transmission shaft (32), and the stator of the linear drive unit (31) is fixed on the base (1). A floating damping mechanism is provided between the first impact component (3) and the second impact component (4) and the base (1); the floating damping mechanism includes a guide rail slider and a damping spring assembly, configured to allow the linear drive unit (31) to generate axial displacement when subjected to recoil force in order to absorb high-frequency aftershocks; The control system (5) is equipped with a phase locking module, which is used to monitor and correct the phase difference between the first impact component (3) and the second impact component (4) in real time, so that the phase synchronization error is less than 10 microseconds; The linear drive unit (31) is provided with a forced air cooling heat sink on the outside, and a temperature sensor is provided inside the forced air cooling heat sink. When the coil temperature exceeds the threshold, the control system (5) reduces the impact frequency. The control system (5) controls the first impact component (3) and the second impact component (4) to reciprocate toward the test piece mounting platform (2) at the same frequency and phase, so that the impact hammers (33) on both sides simultaneously impact the test piece (100) or simultaneously retreat in the opposite direction, using symmetrical reaction forces to counteract the horizontal vibration of the base (1).

2. The symmetrical force-balanced high-frequency impact device according to claim 1, characterized in that, The test piece mounting table (2) includes a double-sided clamp with two impact surfaces facing each other, and the test piece (100) is clamped between the two impact surfaces.

3. The symmetrical force-balanced high-frequency impact device according to claim 1, characterized in that, The impact hammer (33) is connected to the drive shaft (32) via a force sensor (7), which is used to collect impact force signals in real time and feed them back to the control system (5).

4. The symmetrical force-balanced high-frequency impact device according to claim 1, characterized in that, It also includes a position adjustment mechanism, on which the first impact component (3) and the second impact component (4) are mounted on the base (1) via the position adjustment mechanism. The position adjustment mechanism is used to adjust the initial distance between the impact hammers (33) on both sides and the specimen mounting platform (2).

5. The symmetrical force-balanced high-frequency impact device according to claim 1, characterized in that, The front end of the impact hammer (33) is provided with a replaceable impact contact. The material hardness of the impact contact is higher than that of the test piece (100), and the shape of the impact contact is selected from one of planar, hemispherical or conical.

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