A beam structure vibration fatigue device

Abstract

The present invention relates to a beam structure vibration fatigue device, comprising a beam specimen, a beam end clamping seat, a vibration platform, a vibration motor, a vibration isolation spring, and a base. One end of the beam specimen is mounted on the beam end clamping seat or both ends of the beam specimen are mounted on the beam end clamping seat, the beam end clamping seat is mounted on the vibration platform, the vibration motor is mounted on the vibration platform, the output shaft of the vibration motor is equipped with an eccentric block, and the vibration isolation spring supports the vibration platform, one end of which is connected to the base, and the other end is connected to the vibration platform. Under the action of the excitation force, the vibration platform of the present invention and the accessories mounted thereon will undergo forced vibration. The beam specimen and the beam end clamping seat will vibrate along with the vibration platform. Since the ends of the beam specimen are fixed, the vibration deformation part thereof is not connected to the vibration platform, the vibration deformation of the beam specimen does not affect the vibration of the vibration platform, and the generated vibration waveform has a small degree of distortion. In addition, the present invention can realize fatigue tests of cantilever beams, simply supported beams, and beams fixed at both ends through a single device.

Description

Technical Field

[0001] The invention relates to the field of fatigue testing machines, and in particular to a beam structure vibration fatigue device. Background Art

[0002] Beam structures are widely used in aerospace, energy and power, machinery and construction, etc., such as helicopter rotors, bridge crane main beams, elastic foundation beams, vibrating screen load-bearing beams, etc. Most beam structures are often subjected to alternating stress during operation and use, and fatigue cracks are easily formed. Under the action of dynamic shear load, these cracks will continue to expand and lead to fractures, which may affect the stable operation of production or even induce disasters. For example, in early 1981, the "Kierland" platform in the North Sea oil field in Europe was destroyed. The cause of the accident was that the crossbeam bearing hole cracked due to fatigue under the alternating stress of the waves. According to statistics, structural failure and fracture accidents caused by fatigue cracks account for more than 70% to 80% of the total fracture accidents. Therefore, studying the causes of fatigue fracture of beam structures has very important practical significance and theoretical value for accurately formulating the service life and maintenance cycle and reducing the occurrence of fatigue accidents.

[0003] The existing fatigue testing machine products mainly include electro-hydraulic servo fatigue testing machines and electromagnetic resonance high-frequency fatigue testing machines. These two types of fatigue testing machines cannot achieve symmetrical bending periodic loading of beam specimens. In order to conduct fatigue tests on beam specimens or plate specimens, some scholars have prepared fatigue testing devices for cracked beams, cracked plates and cracked blades. For example, in March 1997, a paper titled "High resolution crack growth measurements in vibrating beams" was published in the journal "FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES" Volume 20, Issue 7. The paper disclosed a vibration fatigue testing device for cracked beams, which mainly includes a sensing coil, an actuating coil, a laser sensor, a feedback control loop and a current amplifier, and the cracked beam specimen is driven to vibrate by electromagnetics. The article "Mechanical Properties and Tests of Cracked Plates under Dynamic Environment" published in the supplement of Volume 19 of the journal "Mechanical Science and Technology" in September 2000 disclosed a vibration fatigue test device for cracked plates, which includes a rotating fatigue test machine, an eccentric wheel, a pulley, a wire rope, a spring, a connector and a test piece. During the test, the eccentric wheel is driven by the rotating fatigue test machine to apply a vibration load to the thin plate through the spring. In June 2006, Zhejiang University's master's thesis "Vibration Fatigue Test of Steam Turbine Blades and Development of Its Automatic Control System" disclosed a vibration fatigue test machine, which includes an eccentric wheel, an eccentric wheel shaft, a sliding column, a steam turbine blade, and a proximity switch sensing area. The eccentric wheel is driven to rotate by a driving motor. By adjusting the upper and lower bolts of the wheel, the position of the shaft on the wheel surface can be changed, thereby realizing the eccentric rotation of the wheel, and the adjustment range is 0 to 10 mm. The sliding column is connected between the eccentric wheel and the blade, converting the periodic motion of the eccentric wheel into the up and down vibration of the blade. In 2009, the journal "Structural Strength Research" published a paper titled "Analysis of Aircraft Horizontal Tail Vibration Fatigue Test". The test device includes a vibrator, a sensor, a counterweight, a horizontal tail and a rigid base. The horizontal tail shaft is fixed on the rigid base and the fatigue test is performed by excitation with a vibrator. However, the vibration fatigue test takes a long time and the vibrator cannot bear it, so it often needs to be stopped for rest regularly.

[0004] According to the excitation method, the main excitation methods of fatigue testing machines are: exciter excitation, inertial excitation and electromagnetic excitation. Fatigue test devices with exciter excitation and inertial excitation belong to mechanical excitation. In order to transmit the excitation force to the specimen, the power transmission output end must be connected to the specimen, and the specimen and the excitation source are mechanically connected. In order to transmit power, power transmission also requires the establishment of a mechanical transmission system, and the transmission system is often complex in structure. In addition, the excitation source, the mechanical transmission system and the specimen together constitute a vibration system. When conducting a specimen fatigue test, the excitation source transmits power through the mechanical transmission component to achieve vibration deformation of the specimen. However, since the specimen is also the execution end of the mechanical transmission system, there is an interaction force between the specimen and the mechanical transmission system, and the vibration deformation of the specimen will affect the output waveform and accuracy of the mechanical transmission system. At this time, the vibration of the specimen will affect the power transmission, so the waveform distortion is serious and the device structure is complex. Since the electromagnetic force can be directly obtained, no transmission component is required, and the vibration of the specimen does not affect the output of the excitation source, so the output waveform distortion is small. However, the electromagnetic fatigue test system is limited by inherent magnetic saturation, is greatly affected by the power supply voltage, the maximum output exciting force is limited, and the low-frequency performance is poor.

[0005] In addition, for the beam structure fatigue test system with exciter excitation and inertial excitation, in order to transmit a larger amplitude, the beam specimen is generally designed as a cantilever beam structure, and the end of the mechanical transmission is often directly connected to one end of the cantilever beam. The biggest feature of this fatigue testing machine is that it can obtain a larger amplitude. However, due to the limitation of the structural shape, it is often designed to only complete the fatigue test of a single cantilever beam structure, and it cannot easily change the constraint mode for fatigue tests of beam structures with other constraint types, such as simply supported beams and beams fixed at both ends. In other words, at present, the structural form of the existing beam structure fatigue test device can generally only complete the fatigue test of a single cantilever beam structure, and it is not possible to use one device to complete vibration fatigue tests of multiple types of beam structures.

[0006] In engineering practice, according to the type of beam constraints, beam structures can be divided into cantilever beams, simply supported beams, and beams with two ends fixed. For example, wind turbine blades are considered cantilever beam structures, bridge crane main beams are considered simply supported beam structures, and vibrating screen load-bearing beams are considered fixed beam structures. It can be seen that according to the constraint method, beam structures are not limited to cantilever beam structures, but also include simply supported beams and beams with two ends fixed. Therefore, it is of great practical significance to improve the function of equipment to simultaneously realize fatigue test devices for cantilever beams, simply supported beams, and beams with two ends fixed through a fatigue device. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a beam structure vibration fatigue device which has a small output vibration waveform distortion and can simultaneously complete fatigue tests of a cantilever beam, a simply supported beam, and a beam fixed at both ends.

[0008] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a beam structure vibration fatigue device, including a beam specimen, a beam end clamping seat, a vibration platform, a vibration motor, a vibration isolation spring, and a base, one end of the beam specimen is installed on the beam end clamping seat or both ends of the beam specimen are installed on the beam end clamping seat, the beam end clamping seat is installed on the vibration platform, the vibration motor is installed on the vibration platform, the output shaft of the vibration motor is equipped with an eccentric block, the vibration isolation spring supports the vibration platform, one end is connected to the base, and the other end is connected to the vibration platform, the beam end clamping seat includes a beam end fixed clamping seat and a beam end rotatable clamping seat.

[0009] Furthermore, in order to test the fatigue characteristics of a beam with one end fixed and the other end hinged, the top and bottom surfaces of one end of the beam specimen are provided with an arc groove, and the top and bottom surfaces of the other end are planes, the end of the beam specimen with the arc groove is mounted on a rotatable clamping seat at the beam end, and the other end of the beam specimen is mounted on a fixed clamping seat at the beam end, and the rotatable clamping seat at the beam end and the fixed clamping seat at the beam end are relatively mounted on the vibration platform; the rotatable clamping seat at the beam end includes an upper clamping block, a lower clamping block and a support, the lower clamping block and the support are fixedly connected by screws, the upper clamping block and the lower clamping block are fixedly connected by screws, and the bottom surface of the upper clamping block and the top surface of the lower clamping block are fixedly connected by screws. A long strip protrusion is provided on the top of the protrusion, and the top of the protrusion is an arc-shaped head. The shape of the arc-shaped head matches the arc-shaped groove of the beam specimen. The long strip protrusion of the upper clamp is pressed in the arc-shaped groove on the top surface of the beam specimen, and the long strip protrusion of the lower clamp is pressed in the arc-shaped groove on the bottom surface of the beam specimen; the beam end fixed clamping seat includes an upper clamp, a lower clamp and a support seat, the lower clamp and the support seat are connected by screws, the upper clamp and the lower clamp are connected by screws, and a long strip protrusion is provided in the middle of the upper clamp and the lower clamp, and the end face of the long strip protrusion is a plane, the long strip protrusion of the upper clamp is pressed on the top plane of the beam specimen, and the protrusion of the lower clamp is pressed on the bottom plane of the beam specimen.

[0010] In order to test the fatigue characteristics of a beam fixed at both ends, the top and bottom surfaces of one end of the beam specimen are planes, and the top and bottom surfaces of the other end are also planes. Both ends of the beam specimen are installed on beam end fixing clamping seats, the two beam end fixing clamping seats have the same structural shape, and are relatively installed on the vibration platform; the beam end fixing clamping seat includes an upper chuck, a lower chuck and a support seat, the lower chuck and the support seat are connected by screws, the upper chuck and the lower chuck are connected by screws, and a long strip protrusion is provided in the middle of the upper chuck and the lower chuck, the end faces of the long strip protrusion are planes, the long strip protrusion of the upper chuck is pressed on the top plane of the beam specimen, and the protrusion of the lower chuck is pressed on the bottom plane of the beam specimen.

[0011] In order to test the fatigue characteristics of the hinged beam at both ends, the top and bottom surfaces of one end of the beam specimen are provided with arc grooves, and the top and bottom surfaces of the other end are also provided with arc grooves. Both ends of the beam specimen are installed on rotatable clamping seats at the beam ends. The rotatable structures of the two beam ends are of the same shape and are relatively installed on the vibration platform; the rotatable clamping seats at the beam ends include an upper clamping block, a lower clamping block and a support. The lower clamping block and the support are fixedly connected by screws, and the upper clamping block and the lower clamping block are fixedly connected by screws. Long strip protrusions are provided in the middle of the bottom surface of the upper clamping block and the top surface of the lower clamping block. The top of the protrusion is an arc head, and the shape of the arc head matches the arc groove of the beam specimen. The long strip protrusion of the upper clamping block is pressed in the arc groove on the top surface of the beam specimen, and the long strip protrusion of the lower clamping block is pressed in the arc groove on the bottom surface of the beam specimen.

[0012] In order to test the fatigue characteristics of the cantilever beam, the top and bottom surfaces of the fixed end of the beam specimen are planes, and the top and bottom surfaces of the other end are also planes. One end of the beam specimen is mounted on the beam end fixed clamping seat, and the other end is not fixed and can vibrate freely. The beam end fixed clamping seat is mounted on the vibration platform; the beam end fixed clamping seat includes an upper clamp, a lower clamp and a support seat, the lower clamp and the support seat are connected by screws, the upper clamp and the lower clamp are connected by screws, and a long strip protrusion is provided in the middle of the upper clamp and the lower clamp, and the end surface of the long strip protrusion is a plane, the long strip protrusion of the upper clamp is pressed on the top plane of the beam specimen, and the protrusion of the lower clamp is pressed on the bottom plane of the beam specimen.

[0013] Preferably, the vibration platform is provided with a side wall protruding from the platform, the beam end fixing clamping seat is a pressure plate, one end or both ends of the beam specimen are installed between the pressure plate and the side wall, and the pressure block is directly fixed on the side wall by screws.

[0014] Furthermore, the vibration motor is a variable frequency speed regulating motor, and the variable frequency speed regulating motor is electrically connected to a frequency converter.

[0015] Preferably, the vibration motor is a single-phase series-excited motor, and the single-phase series-excited motor is electrically connected to a single-phase voltage regulator.

[0016] The beam specimen is equipped with a counterweight block, which includes an upper counterweight block and a lower counterweight block. The upper counterweight block and the lower counterweight block have the same structural shape and size. The upper counterweight block is installed above the beam specimen, and the lower counterweight block is installed below the beam specimen. The upper counterweight block and the lower counterweight block are connected by bolts.

[0017] The beam specimen is provided with a notch.

[0018] The beneficial effects of the present invention are: providing a beam structure vibration fatigue device with low output vibration waveform distortion and capable of simultaneously completing fatigue tests of cantilever beams, simply supported beams, and beams fixed at both ends. The beam structure vibration fatigue device includes a beam specimen, a beam end clamp, a vibration platform, a vibration motor, a vibration isolation spring, and a base. The vibration motor is installed on the vibration platform, and an eccentric block is installed on the output shaft of the vibration motor. When the vibration motor is transported, the eccentric block generates an eccentric excitation force. Under the action of the excitation force, the vibration platform and the accessories mounted thereon will undergo forced vibration. The beam specimen and the beam clamp will vibrate along with the vibration platform.

[0019] Since the beam specimen itself has weight, the beam specimen is subjected to reciprocating inertial excitation force when following the movement of the vibration platform. By adjusting the rotation speed of the vibration motor so that the rotation frequency of the vibration motor is close to or equal to the natural frequency of the beam specimen, the beam specimen will resonate and produce a larger amplitude, thereby improving the working efficiency of the fatigue test and reducing energy consumption. In the fatigue device of the present invention, since the ends of the beam specimen are fixed and the vibrating deformation part thereof is not connected to the vibration platform, the vibration deformation of the beam specimen does not affect the vibration of the vibration platform. In other words, there is no need to provide a transmission component between the vibration deformation of the beam specimen and the vibration platform. In this way, the vibration of the beam specimen has very little effect on the vibration platform. Therefore, the vibration waveform output by the vibration platform is stable. Under the excitation of a stable waveform, the vibration waveform generated by the beam specimen has a small degree of distortion.

[0020] In addition, since the beam structure vibration fatigue device includes a beam end clamping seat, the beam end clamping seat includes a beam end fixed clamping seat and a beam end rotatable clamping seat. In this way, the beam end clamping seat can be selected at one end or both ends of the beam specimen, thereby forming a beam structure with different constraint types, and fatigue tests of cantilever beams, simply supported beams, and beams fixed at both ends can be carried out. For example, when one end of the beam specimen is clamped on the beam end fixed clamping seat and the other end is free, a cantilever beam structure is formed. When both ends of the beam specimen are clamped on the beam end rotatable clamping seat, a simply supported beam structure is formed. When both ends of the beam specimen are clamped on the beam end fixed clamping seat, two fixed beam structures are formed. Therefore, the present invention can realize fatigue tests of cantilever beams, simply supported beams, and beams fixed at both ends through one device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of Embodiment 1 of the present invention when the beam structure vibration fatigue device is used for fatigue testing of a beam with one end fixed and the other end hinged;

[0022] Figure 2 yes Figure 1 Structural schematic diagram of the middle support joint;

[0023] Figure 3 yes Figure 1 Schematic diagram of the structure after the protective cover is removed from one end of the vibration motor;

[0024] Figure 4 yes Figure 3 Schematic diagram of the eccentric block structure

[0025] Figure 5 yes Figure 1 Schematic diagram of the structure in which the middle beam specimen is installed on the rotatable support seat at the beam end and the fixed clamping seat at the beam end;

[0026] Figure 6 yes Figure 5 Structural schematic diagram of the cross-section of the middle beam specimen;

[0027] Figure 7 yes Figure 1 Schematic diagram of inertial excitation of the vibration motor;

[0028] Figure 8 It is a structural schematic diagram of Embodiment 2 when the beam structure vibration fatigue device of the present invention is used for fatigue testing of a beam fixed at both ends;

[0029] Fig. 9 yes Figure 8 Structural diagram of the installation of the middle beam specimen on the two beam end fixed clamping seats;

[0030] Fig.10 yes Fig. 9 Schematic diagram of the cross-sectional structure of the middle beam specimen;

[0031] Fig.11 It is a structural schematic diagram of the beam structure vibration fatigue device of the present invention used for fatigue test of a beam hinged at both ends in Example 3, in which the beam specimen is installed on rotatable clamping seats at two beam ends;

[0032] Fig.12 yes Fig.11 Structural schematic diagram of the cross-section of the middle beam specimen;

[0033] Fig.13 It is a structural schematic diagram of a fourth embodiment of the beam structure vibration fatigue device of the present invention when used for cantilever beam fatigue test;

[0034] Fig.14 yes Fig.13 Structural schematic diagram of the middle beam specimen installed on the beam end fixing seat;

[0035] Fig.15 yes Fig.14 Top view of the center beam specimen;

[0036] Fig.16 2 is a schematic diagram of the structure of Embodiment 5 of the beam structure vibration fatigue device of the present invention when used for fatigue testing of a cantilever beam with a notch;

[0037] Fig.17 yes Fig.16 Structural schematic diagram of a cantilever beam specimen with a notch installed on a beam end fixing seat;

[0038] Fig.18 yes Fig.17 Top view of the cantilever beam specimen with a notch;

[0039] Fig.19 It is a structural schematic diagram of Embodiment 6 of the beam structure vibration fatigue device of the present invention when used for fatigue testing of a beam fixed at both ends;

[0040] Fig. 20 yes Fig.19 Top view of the center beam specimen; DETAILED DESCRIPTION

[0041] Embodiment 1:

[0042] from Figure 1 It can be seen that the beam structure vibration fatigue device shown in the first embodiment includes a base 1, a support column 11, a vibration isolation spring 2, a vibration platform 3, a support joint 31, a beam end clamp 4, a beam specimen 5, and a vibration motor 6. Four T-shaped support columns 11 are welded on the four corners of the base 1, the vibration isolation spring 2 is a metal spiral column compression spring, the support column 11 is welded to the bottom spring coil of the vibration isolation spring 2, and the top spring coil of the vibration isolation spring 2 is welded to the support joint 31. Combined with the Figure 2 It can be seen that the support joint 31 includes three parts, a disk 312 in the middle, and spring guide columns 311 and support cylinders 313 at both ends. The top spring coil of the support spring 2 passes through the spring guide column 311 and is welded to the bottom surface of the disk 312. The top surface of the support cylinder 313 is welded to the bottom surface of the vibration platform 3. In this way, four vibration isolation springs 2 are used to support the vibration platform 3. The vibration platform 3 is flat in the middle and is surrounded by side walls 32, forming a square frame shape. Two vibration motors 6 are installed on the bottom surface of the vibration platform 3. The vibration motors 6 are variable frequency speed regulation motors. The two variable frequency speed regulation motors are arranged side by side to form a two-axis inertial exciter. In order to adjust the operating frequency of the vibration motor, the variable frequency speed regulation motor is electrically connected to the frequency converter. Combined with Figure 3 and Figure 4 , an eccentric block 61 is mounted on the output shaft of the variable frequency speed regulating motor, and the material of the eccentric block 61 is Q235. The eccentric block 61 includes a semicircular block 611 and a semicircular ring-shaped latch 612. One end of the latch 612 is integrally formed with the semicircular block 611, and the other end is provided with a protruding boss 613, and a through hole is provided on the protruding boss 613. The area enclosed by the semicircular block 611 and the latch 612 is processed with a shaft-clamping hole 614, and the motor output shaft is mounted in the shaft-clamping hole 614. Below the through hole of the protruding boss 613, the semicircular block 611 of the latch 612 is processed with a threaded hole at the corresponding position, and the clamping screw 615 passes through the through hole and is connected with the threaded hole to fix the eccentric block 61 on the output shaft of the vibration motor. For dust prevention and safety, a protective cover 62 is also provided on the variable frequency speed regulating motor. In order to adjust the speed of the vibration motor, the variable frequency speed regulating motor is electrically connected to the frequency converter so that the beam specimen resonates during the test.

[0043] Combination Figure 5 In this embodiment, one end of the beam specimen is fixed and the other end is rotatable. Figure 6 It can be seen that the top and bottom surfaces of one end of the beam specimen are provided with an arc groove 51, and the top and bottom surfaces of the other end are flat. The beam end clamping seat includes a beam end rotatable clamping seat 41 and a beam end fixed clamping seat 42. The beam end rotatable clamping seat 41 and the beam end fixed clamping seat 42 are relatively installed on the vibration platform 3.

[0044] The rotatable clamping seat 41 at the beam end includes an upper clamping block 411, a lower clamping block 412 and a support 413. The lower clamping block 412 and the support 413 are fixedly connected by four lower countersunk screws 416. The upper clamping block 411 and the lower clamping block 412 are fixedly connected by four upper countersunk screws 417. By loosening the four upper countersunk screws 417, the upper clamping block 411 and the lower clamping block 412 can be separated. A long strip protrusion 414 is provided in the middle of the bottom surface of the upper clamping block 411 and the middle of the top surface of the lower clamping block 412. The top of the long strip protrusion 414 is an arc head 415. The shape of the arc head 415 matches the arc groove 51. The long strip protrusion 414 of the upper clamping block is pressed in the arc groove 51 on the top surface of the beam specimen 5, and the long strip protrusion of the lower clamping block 412 is pressed in the arc groove on the bottom surface of the beam specimen. In this way, due to the matching of the long strip protrusion and the arc groove, the end of the beam test piece 5 can be rotated. The beam test piece 5 and the beam end rotatable clamping seat 41 form a rotatable connection.

[0045] The beam end fixing clamp seat 42 includes an upper clamp 421, a lower clamp 422 and a support seat 423. The lower clamp 422 and the support seat 423 are connected by a lower countersunk screw. The upper clamp 421 and the lower clamp 422 are connected by an upper countersunk screw. A long strip protrusion 424 is provided in the middle of the upper clamp 421 and the lower clamp 422, and the end surface of the long strip protrusion is a plane. The long strip protrusion 424 of the upper clamp is pressed on the top plane of the beam specimen, and the protrusion of the lower clamp is pressed on the bottom plane of the beam specimen. In this way, the beam specimen is fixed on the beam end fixing clamp seat 42 by the pre-tightening force of the upper countersunk screw.

[0046] When this embodiment is used for fatigue testing of a beam with one end fixed and the other end hinged, first loosen the four upper countersunk screws 417 on the beam end rotatable clamping seat 41 and the beam end fixing seat 42, and loosen the upper clamping block 411 and the upper clamping head 421. After the beam specimen 5 is installed at the predetermined position, tighten the upper countersunk screws 417. Then, start the two vibration motors and control the two vibration motors to rotate synchronously and in opposite directions. Figure 7It can be seen that the dual vibration motor drives are arranged in parallel to form a two-axis inertial exciter. By controlling the two vibration motors to rotate synchronously and in opposite directions, the exciting forces generated by their eccentric blocks cancel each other out in the horizontal direction and add a resultant force in the vertical direction. Therefore, the motion trajectory of the vibration table is a straight line along the vertical direction. When the semi-disc eccentric blocks of the two vibration motors rotate, the centrifugal force F generated by the two eccentric blocks, the horizontal force Fx always cancels each other out, and the vertical force Fy always adds to each other. The resulting exciting force 2Fy forces the vibration table to perform reciprocating vibrations in an approximately straight line in the vertical direction. When the centrifugal forces are completely superimposed, the exciting force is maximum, and when the centrifugal forces are completely offset, the exciting force is zero.

[0047] The cyclic rotation of the vibration motor generates a cyclic exciting force in the vertical direction. Under the action of the exciting force, the vibration platform and the components mounted thereon will vibrate in a forced manner. The beam specimen will first follow the vibration platform to perform rigid body motion. Due to its own weight, the beam specimen itself generates a rigid body inertial exciting force. When the speed of the vibration motor is adjusted so that the speed frequency is close to or equal to the natural frequency of the beam specimen, the beam specimen will resonate strongly and generate a large amplitude. Through resonant excitation, the beam specimen can produce a large vibration deformation. Therefore, the working efficiency of the fatigue test can be improved and energy consumption can be reduced. Since the two ends of the beam specimen are fixed, its vibration deformation part is in the middle and is not connected to the vibration platform, and the vibration deformation of the beam specimen does not affect the vibration of the vibration platform. In other words, there is no direct contact between the vibrating part of the beam specimen and the vibration platform. In this way, the vibration of the beam specimen has very little effect on the vibration platform. Therefore, the vibration waveform output by the vibration platform is stable. Under the excitation of a stable waveform, the vibration waveform generated by the beam specimen has a small degree of distortion.

[0048] Through the above operations, the fatigue test of the beam with one end fixed and the other end hinged is completed. Based on the similarity theory, the test results of this beam structure with one end fixed and the other end hinged can provide a reference for the design of the prototype beam structure.

[0049] Of course, the vibration motor of this embodiment can also be equipped with an eccentric block at each end of the output shaft, wherein one eccentric block can be fixed and the other eccentric block can be adjustable, and the magnitude of the excitation force can be changed by adjusting the angle between the adjustable eccentric block and the fixed eccentric block. When leaving the factory, the angle between the adjustable eccentric block and the fixed eccentric block is 0 degrees. The vibration motor can be directly purchased from outside, such as the YZS vibration motor of Henan Tongtai Machinery Co., Ltd.

[0050] Embodiment 2:

[0051] like Figure 8 As shown, the difference between Example 2 and Example 1 lies in the structural shape and clamping method of the beam specimen, as well as the additional counterweight 7. Fig. 9 It can be seen that the top and bottom surfaces of one end of the beam specimen are planes, and the top and bottom surfaces of the other end are also planes. Fig.10, a central through hole 52 is provided in the middle of the beam specimen 5. In order to increase the inertial excitation force, a counterweight 7 is provided on the beam specimen, and the counterweight includes an upper counterweight 71 and a lower counterweight 72. The upper counterweight 71 and the lower counterweight 72 have the same structure, shape and size. The upper counterweight 71 and the lower counterweight 72 both have five through holes, four of which are located at the four corners and one at the middle. The upper counterweight 71 is installed above the beam specimen 5, and the lower counterweight 72 is installed below the beam specimen. The upper counterweight 71 and the lower counterweight 72 are connected by five bolts. Among them, the bolts at the center position pass through the through holes of the upper counterweight 71, the beam specimen and the lower counterweight 72 in turn. In this embodiment, both ends of the beam specimen are installed on the beam end fixing clamping seat 42. The beam end fixing clamping seat 42 of this embodiment has the same structure and shape as the beam end fixing clamping seat in the first embodiment, which will not be repeated here. Through this clamping method, the beam specimen becomes a fixed-end beam, and the fatigue test of the fixed-end beam specimen can be completed. Fixed-end beams are common in engineering, such as vibrating screen load-bearing beams. Based on similarity theory, the test results of this fixed-end beam structure can provide a reference for the design of engineering prototype beam structures.

[0052] When this embodiment is used for fatigue testing of a beam fixed at both ends, first loosen the upper countersunk screw on the upper clamp 421, install the beam specimen 5 at a predetermined position, and then tighten the upper countersunk screw. Then, start the two vibration motors and control them to rotate synchronously and in opposite directions. Under the driving of the vibration motor, the eccentric block 61 rotates along with the motor. The exciting forces generated by the eccentric block cancel each other out in the horizontal direction, and a combined force is superimposed in the vertical direction to generate exciting forces along the vertical direction of the vibration platform. The cyclic rotation of the vibration motor generates cyclic exciting forces along the vertical direction. Under the action of the exciting force, the vibration platform and the parts mounted thereon will vibrate forcedly. The beam specimen will follow the vibration platform to perform rigid body motion, and will be subject to the inertial exciting force of the beam specimen itself and the inertial exciting effect of the counterweight. After adding the counterweight, the exciting force of the beam specimen can be increased, and the vibration deformation of the beam specimen can be increased. By adjusting the speed of the vibration motor so that the speed frequency is close to or equal to the natural frequency of the beam specimen, the beam specimen will resonate strongly and generate a large amplitude. Through resonant excitation, the beam specimen can produce a large vibration deformation. Therefore, the working efficiency of the fatigue test can be improved and energy consumption can be reduced. Since the two fixed ends of the beam specimen 5 have no lateral deformation, the vibration deformation part is in the middle. The elastic deformation of the beam specimen 5 will not interfere with the vibration of the vibration platform. In other words, the elastic vibration of the beam specimen has little effect on the vibration of the vibration platform. Therefore, the vibration waveform output by the vibration platform is stable and good. Under the excitation of the stable waveform, the vibration waveform of the beam specimen is also very stable, and the waveform distortion is small.

[0053] Embodiment three:

[0054] The difference between Example 3 and Example 1 lies in the beam specimen structure shape and clamping method. Fig.11 and Fig.12 As shown, arc grooves 51 are provided on the top and bottom surfaces of both ends of the beam specimen. The two ends of the beam specimen are respectively mounted on two rotatable clamping seats 41 at the beam ends. The structure of the rotatable clamping seats 41 at the beam ends in this embodiment is the same as the shape of the rotatable clamping seats at the beam ends in Example 1, and will not be repeated here. In this way, the two ends of the beam specimen can rotate slightly, and there is also a slight movement in the horizontal direction, which is similar to the constraint of a simply supported beam structure. Simply supported beam structures are relatively common in engineering. For example, the main beam of a bridge crane is regarded as a simply supported beam structure. Based on the similarity theory, the test results of this type of beam structure with rotatable ends can provide a reference for the design of the engineering prototype beam structure.

[0055] Embodiment 4:

[0056] The difference between Example 4 and Example 1 lies in the structural shape and clamping method of the beam specimen, as well as the connection method between the vibration platform and the base. Fig.13 As shown, this embodiment includes a base 1, a vibration isolation spring 2, a vibration platform 3, a beam specimen 5, and a vibration motor 6. The top spring coil of the vibration isolation spring 2 is directly welded to the bottom surface of the vibration platform 3, and the bottom spring coil of the vibration isolation spring 2 is welded to the base 1. The structural shapes of the vibration motor, base, and vibration platform are the same as those in the first embodiment. The structure of the beam end fixed clamping seat 42 is the same as the structural shape of the beam end fixed clamping seat in the first embodiment, and will not be repeated here. The beam end fixed clamping seat 42 is installed on the side wall of the vibration platform, one end of the beam specimen is installed on the beam end fixed clamping seat, and the other end of the beam specimen is free and unconstrained. Combined with Fig.14 It can be seen that a mass block 8 is also provided on the free end of the beam specimen, and the mass block 8 includes an upper mass block 81 and a lower mass block 82. The upper mass block 81 and the lower mass block 82 have the same structure shape and size, and both the upper mass block 81 and the lower mass block 82 have two through holes. Fig.15 , two through holes are also opened on the beam specimen, and the two through holes are arranged along the axial direction of the beam specimen. The upper mass block 81 is installed above the beam specimen, and the lower mass block 82 is installed below the beam specimen. The upper mass block 81 and the lower mass block 82 are connected by two bolts. The bolts pass through the through holes of the upper mass block 81, the beam specimen and the lower mass block 82 in turn. In this way, one end of the beam specimen is fixed and the other end is free, forming a cantilever beam structure. Cantilever beam structures are more common in engineering, such as turbine blades, wind turbine blades and helicopter rotors. In design analysis, these structures are often simplified to cantilever beam structure analysis. Based on similarity theory, the fatigue test results of the cantilever beam structure can provide a reference for the design of the engineering prototype beam structure.

[0057] Embodiment five:

[0058] Depend on Fig.16 , Fig.17 and Fig.18It can be seen that the difference between Example 5 and Example 4 lies in the structural shape of the beam specimen. A notch 54 is opened in the middle of the beam specimen of this embodiment, and the other structural shapes and fixing methods are the same as those of Example 4. In this way, this embodiment can complete the crack growth test of the cantilever beam. The test results provide data support for the design of the cantilever beam structure based on damage tolerance.

[0059] The crack extension test process is divided into two parts. First, the crack is prefabricated. By adjusting the speed of the vibration motor, the speed frequency is close to or equal to the natural frequency of the beam specimen, and the beam specimen will resonate strongly, thereby generating a large amplitude. Due to the stress concentration at the notch, fatigue cracks will form at the notch after a period of time. During the test, the crack length is observed through an industrial inspection video microscope (AOSVI AF216C). When the crack length roughly reaches the prefabrication requirement, the motor stops. Then, the crack length is measured offline through an industrial video microscope, and the fatigue crack prefabrication is completed. The second step is to restart the vibration motor and control the motor speed to make the beam specimen vibrate cyclically under the specified stress. During the test, the crack length is measured online through an industrial inspection video microscope. After the crack expands unstably or expands to a predetermined size, the entire crack extension test time is recorded at the same time. In this way, the crack extension test is completed.

[0060] Embodiment six:

[0061] like Fig.19 As shown, the difference between Example 6 and Example 1 lies in the structure of the beam specimen and the structure of the beam end clamping seat. The top and bottom surfaces of the two ends of the beam specimen are planes, the vibration platform 3 is provided with a side wall 32 protruding from the platform, and the beam end fixing clamping seat is a pressing plate 43, and the two pressing plates have two through holes, and the two ends of the beam specimen also have two holes, and threaded holes are opened at corresponding positions on each side wall. The two ends of the beam specimen are installed between the pressing plate 43 and the side wall 32, and the screws pass through the through holes of the pressing plate and the through holes of the beam specimen in turn, and then are threadedly connected with the threaded holes of the side wall. The beam specimen is directly fixed and installed on the side wall. In this way, the two ends of the beam specimen are directly fixed on the side wall of the vibration platform to form a beam structure with two ends fixed. Of course, this embodiment can also be used for a cantilever beam structure. When fixing, only one end of the beam specimen needs to be fixed to form a cantilever beam structure.

[0062] As can be seen from the above embodiments, the beam structure vibration fatigue device of the present invention can form beam structures of different constraint types by selecting a beam end fixed clamping seat or / and a beam end rotatable clamping seat at one end or both ends of the beam specimen. Therefore, fatigue tests of beam structures such as cantilever beams, simply supported beams, and beams fixed at both ends can be performed.

[0063] The beam structure vibration fatigue device of the present invention is not limited to the implementation methods of Example 1, Example 2, Example 3, Example 4 and Example 5. For example, the number of vibration motors is not limited to two, but may be one or four. One vibration motor can drive the vibration platform to vibrate in the horizontal and vertical directions to form a single-axis exciter. When the shaft with the eccentric block rotates, an exciting force in the circumferential direction is usually generated. If the eccentric blocks at both ends of the shaft have different installation phases, an exciting force couple that changes in the circumferential direction will also be generated. Therefore, a multi-axis fatigue test of the beam specimen can be carried out. When four vibration motors are used, a four-axis inertial exciter is formed, which usually produces exciting forces of two frequencies. The vibration motor is not limited to a variable frequency speed regulating motor, but may also be a single-phase series-excited motor. The single-phase series-excited motor is electrically connected to a single-phase voltage regulator, and a vibration fatigue test can also be carried out.

[0064] The present invention is not limited to the above-mentioned embodiments. If various changes or modifications to the present invention do not depart from the spirit and scope of the present invention, and if these changes and modifications fall within the scope of the claims and equivalent technologies of the present invention, the present invention is also intended to include these changes and modifications.

Claims

1. A beam structure vibration fatigue device, characterized in that: It includes a beam specimen, a beam end clamping seat, a vibration platform, a vibration motor, a vibration isolation spring, and a base. Both ends of the beam specimen are installed on the beam end clamping seat, the beam end clamping seat is installed on the vibration platform, the vibration motor is installed on the vibration platform, and the output shaft of the vibration motor is equipped with an eccentric block. The vibration isolation spring supports the vibration platform, one end of which is connected to the base and the other end is connected to the vibration platform. The beam end clamping seat includes a beam end fixed clamping seat and a beam end rotatable clamping seat. The top and bottom surfaces of one end of the beam specimen are provided with arc grooves, and the top and bottom surfaces of the other end are planes; the end of the beam specimen with the arc groove is mounted on a rotatable clamping seat at the beam end, and the other end of the beam specimen is mounted on a fixed clamping seat at the beam end; the rotatable clamping seat at the beam end and the fixed clamping seat at the beam end are relatively mounted on the vibration platform; the rotatable clamping seat at the beam end comprises an upper clamping block, a lower clamping block and a support; the lower clamping block and the support are fixedly connected by screws; the upper clamping block and the lower clamping block are fixedly connected by screws; the bottom surface of the upper clamping block and the middle part of the top surface of the lower clamping block are provided with long strip protrusions, and the top of the protrusions The upper part is an arc-shaped head, the shape of the arc-shaped head matches the arc-shaped groove of the beam specimen, the long strip protrusion of the upper clamping block is pressed into the arc-shaped groove on the top surface of the beam specimen, and the long strip protrusion of the lower clamping block is pressed into the arc-shaped groove on the bottom surface of the beam specimen; the beam end fixed clamping seat includes an upper clamping head, a lower clamping head and a supporting seat, the lower clamping head and the supporting seat are connected by screws, the upper clamping head and the lower clamping head are connected by screws, and a long strip protrusion is provided in the middle of the upper clamping head and the lower clamping head, the end face of the long strip protrusion is a plane, the long strip protrusion of the upper clamping head is pressed on the top plane of the beam specimen, and the protrusion of the lower clamping head is pressed on the bottom plane of the beam specimen; Or the top and bottom surfaces of one end of the beam specimen are provided with an arc groove, and the top and bottom surfaces of the other end are also provided with an arc groove, both ends of the beam specimen are mounted on a rotatable clamping seat at the beam end, the rotatable structures of the two beam ends are of the same shape, and are relatively mounted on the vibration platform; the rotatable clamping seat at the beam end comprises an upper clamping block, a lower clamping block and a support, the lower clamping block and the support are fixedly connected by screws, the upper clamping block and the lower clamping block are fixedly connected by screws, a long strip protrusion is provided in the middle of the bottom surface of the upper clamping block and the top surface of the lower clamping block, the top of the protrusion is an arc head, the shape of the arc head matches the arc groove of the beam specimen, the long strip protrusion of the upper clamping block is pressed in the arc groove on the top surface of the beam specimen, and the long strip protrusion of the lower clamping block is pressed in the arc groove on the bottom surface of the beam specimen; The beam specimen is provided with a notch.

2. The beam structure vibration fatigue device according to claim 1, characterized in that The vibration motor is a variable frequency speed regulating motor, and the variable frequency speed regulating motor is electrically connected to the frequency converter.

3. The beam structure vibration fatigue device according to claim 1, characterized in that The vibration motor is a single-phase series-excited motor, and the single-phase series-excited motor is electrically connected to a single-phase voltage regulator.

4. The beam structure vibration fatigue device according to claim 1, characterized in that The beam specimen is equipped with a counterweight block, which includes an upper counterweight block and a lower counterweight block. The upper counterweight block and the lower counterweight block have the same structural shape and size. The upper counterweight block is installed above the beam specimen, and the lower counterweight block is installed below the beam specimen. The upper counterweight block and the lower counterweight block are connected by bolts.

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