A modal testing apparatus and method for gravity-stabilized hammering of a trigger

Abstract

The application is a gravity type stable hammer hitting mode test device and method, which comprises a vertical threaded rod, a sensor connected to the threaded rod, a hammer head connected to the sensor, a signal line for signal connection between the sensor and a data collector, a positioning plate on the threaded rod above the sensor, an adjustable counterweight on the threaded rod above the positioning plate to realize different impact forces, a butterfly clamp at one end of a cantilever plate at the top of a main support to hold the threaded rod, a hollow base at the bottom of the main support, the hammer head being located above the base and aligned with the center of the base to ensure that the hammer hitting position is located at the center of the base, a scale plate being provided on one side of the threaded rod at the top of the base to facilitate reading of the corresponding height of the bottom of the hammer head, a hollow anti-double hitting mechanism being provided at the top of the base, the distance from the bottom of the positioning plate to the bottom of the hammer head being equal to the distance from the upper surface of the anti-double hitting mechanism to the bottom of the base inside, and the hammer head being triggered when it contacts the ground to trigger the anti-double hitting mechanism. The device simplifies the operation under the premise of ensuring the accuracy of the test, does not require electromechanical devices, and prolongs the service life.

Description

Technical Field

[0001] This invention relates to a gravity-based stable trigger hammer modal testing device and method, specifically to a gravity-based stable trigger hammer modal testing device and method for structural design and structural health monitoring in the construction industry, belonging to the technical field of vibration modal testing and measurement devices. Background Technology

[0002] Modal testing refers to tests that measure the natural frequencies, damping ratios, mode shapes, and modal masses of a system. In modal testing, the system is subjected to a given excitation, and the response signal is obtained. Then, modal parameter identification methods are applied to obtain the system's modal parameters.

[0003] Modal testing typically employs the impact method, which generates excitation by striking the surface of the object under test with a hammer. This method is fast, convenient, and suitable for on-site measurements. Current technologies usually involve manual hammering or electromechanical control of the hammer.

[0004] Manual hammering requires a high level of experience from the tester. During the hammer activation process, inexperienced testers may struggle to control the force of each strike and cannot ensure the hammer is perpendicular to the impact surface. This often results in unsatisfactory results within a few strikes, significantly increasing the test time and leading to poor repeatability and large errors.

[0005] Using electromechanical devices to achieve hammering, such as CN203519438U, CN110243938A, CN 218066956U, CN104155076A, etc., is costly and dependent on electricity. It requires the test environment to be powered, has poor adaptability to the test environment, and the electromechanical devices are prone to failure and have a short service life. Summary of the Invention

[0006] The present invention proposes a modal testing device and method for gravity-based stable triggering hammer impact, which aims to overcome the above-mentioned shortcomings of the prior art, simplify the operation while ensuring the accuracy of the test, eliminate the need for electromechanical devices, and extend the service life.

[0007] The technical solution of this invention: A modal testing device for gravity-based stable triggering hammer impact, comprising a vertical threaded rod, the bottom end of which is threadedly connected to a top threaded hole on the top of a sensor, and a bottom threaded hole on the bottom of the sensor being threadedly connected to a small screw on the top of the hammer head. A signal line is connected to an external signal line at the top of the sensor, and the sensor is connected to a data acquisition unit via the signal line to output force data. A positioning plate is welded onto the threaded rod above the sensor, and several counterweights are fitted onto the threaded rod above the positioning plate. The size and number of counterweights are variable to achieve different impact forces. A fixing nut is fixed to the threaded rod on the top surface of the topmost counterweight. A cantilever is located at the top of the main support. A butterfly clip is provided at one end of the plate, which holds the upper part of the threaded rod. A hollow base is provided at the bottom of the main support. The hammer head is located above the base and aligned with the center of the base. The threaded rod and hammer head aligned with the center of the base ensure that the hammering position is in the center of the base. A scale plate is provided on one side of the threaded rod at the top of the base. The scale plate is engraved with graduations and height values, which can be easily read to determine the corresponding height of the bottom of the hammer head. A hollow anti-collision mechanism is provided at the top of the base. The outer diameter of the hammer head is smaller than the inner diameter of the anti-collision mechanism, and the outer diameter of the positioning plate is larger than the inner diameter of the anti-collision mechanism. The distance from the bottom of the positioning plate to the bottom of the hammer head is equal to the distance from the upper surface of the anti-collision mechanism to the inner bottom of the base, ensuring that the anti-collision mechanism is triggered exactly when the hammer head contacts the ground.

[0008] Preferably, the anti-interlocking mechanism includes a hinge support at the top edge of the base, a displacement amplifying rod rotatably connected to the hinge support with a limiting ring at one end near the base, and a steering rope at the other end of the displacement amplifying rod. The steering rope passes through several fixed pulleys mounted on a fixed plate at the bottom of the main support and is connected to a pin at the other end. The pin is inserted into a pin hole on the side of the blocking ring. The blocking ring is welded to the main support on one side of the fixed plate. The inner side of the blocking ring opposite the pin hole is rotatably connected to one end of a control bar via a control hinge. The other end of the control bar is supported on the other end of the pin. The middle of the steering rope is connected to one end of the control rope, and the other end of the control rope is fixed to the bottom surface of the spring base plate. The spring base plate is supported on the control bar. The top surface of the spring base plate is connected to the bottom end of a compression spring. The top end of the compression spring is fixed to the bottom surface of the upper baffle. The upper baffle is fixed to the main support. The diameter of the spring base plate and the compression spring is smaller than the inner diameter of the blocking ring. When the hammer head contacts the ground, the limiting ring displaces downward. This displacement is amplified by the hinge support and the displacement amplification rod, causing the steering rope to pull out the pin. Subsequently, the control bar falls and the elastic potential energy of the compressed spring is released. The spring base plate displaces downward, causing the control rope to move upward in the opposite direction, thus lifting the hammer head off the ground and preventing secondary impacts.

[0009] A test method for a gravity-based stable triggered hammer modal testing device includes:

[0010] Before testing, connect the sensor signal line, tighten the sensor to the threaded rod, tighten the hammer head to the sensor, select an appropriate weight according to the required impact force, install the weight on the positioning plate of the threaded rod with a fixing nut, and then clamp the threaded rod to the end of the cantilever plate with a butterfly clamp. At the same time, record the scale position on the scale plate corresponding to the bottom of the hammer head.

[0011] During testing, the butterfly clamp is released, and the hammer falls freely under gravity. Upon reaching the bottom of the base, it strikes, simultaneously triggering the anti-double-hit mechanism to lift the hammer off the ground and prevent secondary impacts. The principle is that the positioning plate contacts the limiting ring, causing it to displace downwards. This displacement is amplified several times upwards by the displacement amplification rod. Through the fixed pulley and steering rope, this upward displacement is converted into a horizontal displacement, causing the steering rope to pull out the pin. The instant the pin is pulled out, the control bar rotates downwards, releasing the elastic potential energy of the compressed spring and causing the spring base plate to displace downwards. Subsequently, the control rope tightens, and the reverse control steering rope, through the displacement amplification rod, drives the limiting ring upwards, lifting the hammer off the ground, thus preventing double-hit. This force transmission process is completed instantaneously.

[0012] Advantages of this invention: 1) It can ensure that the hammer head is perpendicular to the surface being hammered by making the hammer head fall freely;

[0013] 2) Secondary double-hit can be avoided by using a limiting plate and limiting strip structure;

[0014] 3) The hammering force is adjustable through the use of different replaceable counterweights;

[0015] 4) Stable output of hammering force is achieved by visually ensuring that the bottom of the hammer head is at the same height on the scale plate with each hammer blow. Attached Figure Description

[0016] Figure 1 This is a flowchart of the test method for the modal test device of the gravity-based stable triggering hammer impact according to the present invention.

[0017] Figure 2 This is a schematic diagram of the modal testing device for gravity-based stable triggering hammer impact according to the present invention.

[0018] Figure 3 yes Figure 2 A schematic diagram of the structure of the central defense chain mechanism.

[0019] Figure 4 yes Figure 3 A bottom view showing details of the bottom of the medium compression spring.

[0020] Figure 5 yes Figure 3 A detailed diagram of the center pin.

[0021] Figure 6 yes Figure 2 A schematic diagram of the structure of the hammerhead.

[0022] Figure 7 yes Figure 2 A perspective view of the sensor structure.

[0023] In the diagram, 1 is the threaded rod, 2 is the counterweight, 3 is the butterfly clamp, 4 is the fixing nut, 5 is the sensor, 6 is the signal line, 7 is the hammer, 8 is the scale plate, 9 is the base, 10 is the cantilever plate, 11 is the positioning plate, 12 is the anti-collision mechanism, 13 is the limit ring, 14 is the hinge support, 15 is the displacement amplification rod, 16 is the steering rope, 17 is the fixed pulley, 18 is the fixing plate, 19 is the control rope, 20 is the pin, 21 is the blocking ring, 22 is the upper baffle, 23 is the compression spring, 24 is the spring base plate, 25 is the control bar, 26 is the control hinge, 27 is the pin port, 28 is the signal line connection port, 29 is the top threaded hole, and 30 is the bottom threaded hole. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to embodiments and specific implementation methods.

[0025] like Figure 2 As shown, a modal testing device for gravity-driven stable triggering hammer impact includes a vertical threaded rod 1. The bottom end of the threaded rod 1 is threadedly connected to the top threaded hole 29 of the sensor 5. The bottom threaded hole 30 of the sensor 5 is threadedly connected to the small screw at the top of the hammer head 7. The signal line connection port 28 at the top of the sensor 5 is connected to an external signal line 6. A positioning plate 11 is welded onto the threaded rod 1 above the sensor 5. Several counterweights 2 are fitted onto the threaded rod 1 above the positioning plate 11. A fixing nut 4 is fixed on the threaded rod 1 on the top surface of the topmost counterweight 2. A butterfly clip 3 is provided at one end of the cantilever plate 10 at the top of the main support. The butterfly clip 3 clamps the upper part of the threaded rod 1. A hollow base 9 is provided at the bottom of the main support. The hammer head 7 is located above the base 9 and aligned with the center of the base 9. A scale plate 8 is provided on one side of the threaded rod 1 at the top of the base 9. A hollow anti-interruption mechanism 12 is provided at the top of the base 9.

[0026] The outer diameter of the hammer head 7 should be smaller than the inner diameter of the anti-interlocking mechanism 12, and the outer diameter of the positioning plate 11 should be larger than the inner diameter of the anti-interlocking mechanism 12.

[0027] The counterweight 2 is fixed to the positioning plate 11 by the fixing nut 4. The size and number of the counterweight 2 are variable to achieve different impact forces. The threaded rod 1 and the hammer head 7, which are aligned with the center of the base 9, ensure that the hammering position is at the center of the base 9. The distance from the bottom of the positioning plate 11 to the bottom of the hammer head 7 is equal to the distance from the upper surface of the anti-collision mechanism 12 to the inner bottom of the base 9, ensuring that the anti-collision mechanism 12 is triggered precisely when the hammer head 7 contacts the ground.

[0028] Hammerhead 7 Figure 6 As shown, the hammer head 7 is replaceable. Depending on the experimental conditions, different types of hammer heads, such as metal hammer heads, PVC (polyvinyl chloride) hammer heads, or rubber hammer heads, can be selected to control the frequency response range of the hammering.

[0029] like Figure 7 As shown, the top threaded hole 29 and the bottom threaded hole 30 are respectively provided at the center of the upper and lower surfaces of the sensor 5. The diameters of the top threaded hole 29 and the bottom threaded hole 30 are the same as the diameter of the threaded rod 1 and the small screw of the hammer head 7, respectively. By tightening the screw, the sensor 5, the threaded rod 1 and the hammer head 7 can be connected to form a whole. The signal line connection port 28 provided on the upper surface of the sensor 5 can be connected to the signal line 6 to connect to the external data acquisition device to output force data.

[0030] The end of the cantilever plate 10 should be aligned vertically with the center of the large ring of the base 9 to ensure the accuracy of the hammering point.

[0031] The counterweight 2 is specifically a ring with a threaded hole in the center. The diameter of the hole is the same as the diameter of the threaded rod 1. The outer diameter of the ring is variable, which can form several counterweights of different sizes and masses. The counterweight 2 can be marked with its own mass. The number of counterweights 2 can be increased or decreased according to the required hammering force.

[0032] The scale plate 8 is engraved with graduations and height values, which makes it easy to read the corresponding height of the bottom of the hammer head 7.

[0033] The anti-combo mechanism 12 includes a hinge support 14 at the top edge of the base 9, a displacement amplifying rod 15 rotatably connected to the hinge support 14 with one end near the base 9 connected to a limiting ring 13, and the other end of the displacement amplifying rod 15 connected to one end of a steering rope 16. The steering rope 16 passes through several fixed pulleys 17 mounted on a fixed plate 18 fixed to the lower part of the main support and has its other end connected to one end of a pin 20. The pin 20 is inserted into a pin opening 27 on the side of a blocking ring 21. The blocking ring 21 is welded to the main support on one side of the fixed plate 18. On the upper side, the inner side of the blocking ring 21 opposite to the pin port 27 is rotatably connected to one end of the control bar 25 through the control hinge 26. The other end of the control bar 25 is supported on the other end of the pin 20. The middle part of the steering rope 16 is connected to one end of the control rope 19. The other end of the control rope 19 is fixed to the bottom surface of the spring base plate 24. The spring base plate 24 is supported on the control bar 25. The top surface of the spring base plate 24 is connected to the bottom end of the compression spring 23. The top end of the compression spring 23 is fixed to the bottom surface of the upper baffle 22. The upper baffle 22 is fixed on the main bracket.

[0034] When the hammer head 7 contacts the ground, the limiting ring 13 is displaced downwards. This displacement is amplified by the hinge support 14 and the displacement amplification rod 15, causing the steering rope 16 to pull out the pin 20. Subsequently, the control bar 25 falls and compresses the elastic potential energy of the spring 23, which is released. The spring base plate 24 moves downwards, causing the control rope 19 to move upwards. The control rope 19 then moves the limiting ring 13 upwards, lifting the hammer head 7 off the ground and preventing secondary impacts.

[0035] During installation, ensure that the diameters of the spring base plate 24 and the compression spring 23 are smaller than the inner diameter of the blocking ring 21. The compression spring should initially be in a compressed state, storing a certain amount of elastic potential energy.

[0036] The control strip 25 is preferably made of iron or aluminum with high hardness, the pin 20 is preferably made of polytetrafluoroethylene with low coefficient of friction, and the inner wall of the pin opening 27 on the blocking ring 21 is preferably lined with mirror stainless steel to ensure that the friction between the pin 20 and the pin opening 27 is small and can be easily pulled out when force is applied.

[0037] The control rope 19 is a branch of the steering rope 16. The end of the control rope 19 is tightly connected to the spring base plate 24. Initially, it is in a relaxed state without force. When the pin 20 is pulled out, it quickly becomes tensile and stressed due to the extension of the compression spring 23.

[0038] Before testing, connect the signal line 6 of sensor 5 and tighten sensor 5 to threaded rod 1. Tighten hammer head 7 to sensor 5. Select a counterweight 2 of appropriate mass according to the required impact force and install it on the positioning plate 11 of threaded rod 1 through fixing nut 4. Then clamp threaded rod 1 to the end of cantilever plate 10 through butterfly clamp 3. At the same time, record the scale position on the scale plate 8 corresponding to the bottom of hammer head 7.

[0039] During testing, the butterfly clip 3 is released, and the hammer 7 falls freely under gravity. When it reaches the bottom of the base 9, it strikes. At the same time, the anti-double-hit mechanism 12 is triggered, lifting the hammer 7 off the ground to prevent secondary double-hit. Specifically, the positioning plate 11 touches the limiting ring 13, causing the limiting ring 13 to move downward. This displacement is amplified several times upward by the displacement amplification rod 15. The upward displacement is then converted into a horizontal displacement by the fixed pulley 17 and the steering rope 16, causing the steering rope 16 to pull out the pin 20. At the moment the pin 20 is pulled out, the control bar 25 rotates downward, and the elastic potential energy of the compressed spring 23 is released, causing the spring base plate 24 to move downward. Then, the control rope 19 tightens, and the reverse control steering rope 16 drives the limiting ring to move upward through the displacement amplification rod 15, lifting the hammer 7 off the ground, thus achieving anti-double-hit. This force transmission process is completed instantaneously.

[0040] All of the components described above are existing technologies, and those skilled in the art can use any model and existing design that can achieve their corresponding functions.

[0041] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A modal testing apparatus for gravity-stabilized hammering of a trigger, characterized by, The utility model relates to a kind of hammering device, including vertical threaded rod (1), threaded rod (1) bottom end is connected with the top threaded hole (29) of sensor (5) top, the bottom threaded hole (30) of sensor (5) bottom is connected with the small screw rod of hammer head 7 top, sensor (5) top signal line connection mouth (28) is connected with signal line (6), sensor (5) is connected with data collector by signal line (6) signal, threaded rod (1) is welded with positioning plate (11) on the top of sensor (5), threaded rod (1) is sleeved with several counterweight blocks (2) on the top of positioning plate (11), the top surface threaded rod (1) of topmost counterweight block (2) is fixed with fixed nut (4), cantilever plate (10) one end is equipped with butterfly clamp (3) in the top of main support, butterfly clamp (3) clamps threaded rod (1) upper portion, main support bottom is equipped with hollow base (9), hammer head (7) is located above base (9) and is aligned with the center of base (9), base (9) top threaded rod (1) one side is equipped with scale plate (8), base (9) top is equipped with hollow anti-bounce mechanism (12), hammer head (7) outer diameter is less than anti-bounce mechanism (12) inner diameter, positioning plate (11) outer diameter is greater than anti-bounce mechanism (12) inner diameter, the distance from the bottom of positioning plate (11) to the bottom of hammer head (7) is equal to the distance from the upper surface of anti-bounce mechanism (12) to the inner bottom of base (9);The anti-bounce mechanism (12) includes hinge support (14) of the edge of base (9) top, displacement amplification rod (15) is rotatably connected with hinge support (14) and is connected with limit ring (13) close to one end of base (9), the other end of displacement amplification rod (15) is connected with one end of steering rope (16), steering rope (16) passes through several fixed pulleys (17) installed on fixed plate (18) fixed in the lower part of main support and is connected with one end of bolt (20), bolt (20) is inserted in bolt mouth (27) in the side of blocking ring (21), blocking ring (21) is welded on the main support of one side of fixed plate (18), the inner side opposite with bolt mouth (27) is rotatably connected with one end of control bar (25) by control hinge (26), the other end of control bar (25) is supported on the other end of bolt (20), the middle of steering rope (16) is connected with one end of control rope (19), the other end of control rope (19) is fixed on the bottom surface of spring bottom plate (24), spring bottom plate (24) is supported on control bar (25), the top surface of spring bottom plate (24) is connected with the bottom end of compression spring (23), the top end of compression spring (23) is fixed on the bottom surface of upper baffle (22), upper baffle (22) is fixed on the main support, the diameter of spring bottom plate (24) and compression spring (23) is less than the inner diameter of blocking ring (21).

2. The test method of claim 1, wherein the test method is characterized by, It includes: Before the test work, connect the signal line (6) of the sensor (5), tighten the sensor (5) with the threaded rod (1), tighten the hammer head (7) with the sensor (5), select the appropriate mass of the counterweight (2) according to the size of the impact force required for the test, install it on the positioning plate (11) of the threaded rod (1) through the fixing nut (4), and then clamp the threaded rod (1) at the end of the cantilever plate (10) through the butterfly clamp (3), and record the scale position on the scale plate (8) corresponding to the bottom of the hammer head (7); When testing, loosen the butterfly clamp (3), the hammer head (7) freely falls under the action of gravity, and hits the bottom of the base (9) at the same time, and the anti-rebound mechanism (12) triggers the hammer head (7) away from the ground to avoid secondary rebound.

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