A vibration test method

Abstract

The present application relates to a kind of vibration test methods, belong to the technical field of vibration test, solve the problem that the existing vibration test method cannot be tested on large skin composite test piece due to lack of suitable test fixture, affect the structure design and installation reliability verification of product.The vibration test method includes the following steps: step 1: assemble test fixture;Step 2: move test piece to test fixture;Step 3: connect test piece with test fixture;Step 4: tighten the fastening screw of all connecting parts;Step 5: paste sensor on the outer surface of test piece, connect cable to control system;Step 6: control system controls the vibration table system to apply vibration to test piece, and carries out vibration test.The present application realizes the vibration test on large skin composite test piece.

Description

Technical Field

[0001] This invention relates to the field of vibration testing technology, and more particularly to a vibration testing method. Background Technology

[0002] Vibration testing is an important component of product mechanical environment testing and reliability testing. It is a means of simulating the real-world usage environment of a product and an effective method in product design and evaluation. Aerospace products are becoming increasingly longer and faster, resulting in larger product sizes, more complex shapes, and various composite materials used for skinning.

[0003] For a long time, due to the limitations of vibration test fixture structure technology, for test pieces with large and complex skin composite material structures, it is impossible to clamp conventional ring-type test fixtures for vibration testing in order to ensure the effective function of the composite material on the outer surface of the product. Vibration excitation cannot be applied through a vibration table in the laboratory, making it impossible to conduct vibration test assessments on the product, which affects the structural design and installation reliability verification of the product. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a vibration testing method to solve the problem that existing vibration testing methods cannot test and evaluate large skin composite material test pieces due to the lack of suitable test fixtures, which affects the structural design and installation reliability verification of products.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] On one hand, the present invention provides a vibration testing method for conducting vibration tests on skin composite material test specimens, comprising the following steps:

[0007] Step 1: Assemble the test fixture;

[0008] Step 2: Move the test specimen onto the test fixture;

[0009] Step 3: Connect and fix the two sleeves on the left and two sleeves on the right of the test piece to the four bearing mating seats through four bushings, and fine-tune the test piece using the waist-shaped mounting holes on the second connector. After installation, tighten and fix the test piece.

[0010] Step 4: Tighten all the fastening screws at the joints;

[0011] Step 5: Attach the sensor to the outer surface of the test piece and connect the cable to the control system;

[0012] Step 6: The control system controls the vibration table system to apply vibration to the test piece and conduct a vibration test.

[0013] Optionally, step 1 includes the following steps:

[0014] Step 11: Connect the base of the test fixture to the table surface of the vertical vibration table using fastening screws;

[0015] Step 12: Connect the two first connectors and the two second connectors to the base of the test fixture using fastening screws;

[0016] Step 13: Install the 4 bushings into the 4 bearing mating seats and fix them in place.

[0017] Optionally, step 4a is further included between step 4 and step 5: installing protective straps for protecting the test specimen.

[0018] Optionally, step 4a includes the following steps: installing protective straps on the other two hooks on the gantry using fasteners to hold the test piece, and then slightly adjusting the hooks downwards to loosen the straps and move them a certain distance away from the test piece.

[0019] Optionally, the bushing and the bearing mating seat are clearance fit.

[0020] Optionally, both the bushing and the bearing mating seat are made of steel.

[0021] Optionally, step 6 is followed by step 7: removing the sensor from the test piece.

[0022] Optionally, step 8 is included after step 7: removing the fastening screws connected to the test piece and using a hook to lift the test piece to the ground via an elastic suspension device.

[0023] Optionally, step 8 is followed by step 9: removing the vibration test fixture from the vertical vibration table.

[0024] Optionally, the vibration test is conducted using a multi-point maximum value control method in step 6.

[0025] On the other hand, the present invention also provides a vibration testing system for performing the above-mentioned vibration testing method, the vibration testing system including a test fixture.

[0026] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0027] (1) Existing vibration testing methods typically employ ring-type test fixtures. However, these fixtures cause wear to the composite material on the outer surface of the test piece during vibration testing, rendering the composite material ineffective. The vibration testing method of this invention uses a novel four-point connection type test fixture instead of a ring-type fixture. Specifically, it involves setting a first connector and a second connector, with one end connected to the outer surface of the test piece and the other end connected to the base. The base is then connected to the test bench, thus transmitting the vibration from the vibration table to the test piece and meeting the clamping requirements for large skin composite material test pieces.

[0028] (2) By setting the mounting holes on the first connector and the second connector that connect to the base as waist-shaped holes, the present invention facilitates the adjustment of the mounting positions of the first connector and the second connector on the base, making the installation more flexible.

[0029] (3) The present invention sets the second mounting hole on the upright plate of the second connector as an oblong hole to facilitate fine adjustment of the test piece. After the test piece is in place, the test piece is then clamped and fixed.

[0030] (4) By setting the thickness of the main body of the bearing adapter seat to gradually increase from one side to the other, the present invention enables the bearing mating seat to better adapt to the outer surface of the test piece, making the connection between the bearing mating seat and the test piece more secure.

[0031] (5) By providing a reinforcing member between the raised side of the base and the raised surface on the base, the present invention can enhance the load-bearing capacity of the base and improve the safety of the test.

[0032] (6) By setting an additional protective strap and setting the protective strap to not bear force under normal circumstances and only bear force in case of accidents, the present invention achieves the effect of not affecting the normal conduct of modal testing and preventing the test piece from falling accidentally, thus effectively improving the safety of modal testing.

[0033] (7) By providing a limiting part on the hook, the present invention can prevent the elastic hanging device from sliding on the hook after it is hung on the hook, thus greatly improving the stability of the elastic hanging device on the hook.

[0034] (8) Compared with the ring-type test fixture, the four-point socket structure of the present invention effectively reduces the mass of the test fixture and improves the resonance frequency.

[0035] (9) The present invention uses an elastic suspension device, equipped with an elastic rubber rope group, to offset the self-weight of the test piece and the test fixture, ensuring that the test piece is in a free-free boundary condition during the vibration test.

[0036] (10) This invention can be widely applied to vibration testing in aerospace, electronics, weaponry, instrumentation and other fields.

[0037] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages will become apparent from the description or may be learned by practicing the invention. Attached Figure Description

[0038] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0039] Figure 1 This is a schematic diagram of the assembly of the test fixture of the present invention;

[0040] Figure 2 This is an assembly schematic diagram of the test fixture of the present invention from another perspective;

[0041] Figure 3 This is a top view of the first connector of the present invention;

[0042] Figure 4 This is a front view of the first connector of the present invention;

[0043] Figure 5 This is a front view of the second connector of the present invention;

[0044] Figure 6 This is a front view of the bearing mating seat of the present invention;

[0045] Figure 7 This is a left view of the bearing mating seat of the present invention;

[0046] Figure 8 This is a schematic diagram of the structure for conducting vibration tests using the vibration testing system of the present invention.

[0047] Figure label:

[0048] 1-First connecting piece; 2-Second connecting piece; 3-Base; 4-Bearing mating seat; 5-Base; 6-Upright plate; 7-First mounting hole; 8-Connecting hole; 9-Second mounting hole; 10-Main body; 11-Shaft sleeve; 12-Through hole; 13-Groove; 14-Protrusion; 15-Reinforcing member; 16-Test piece; 17-Vibration table system; 18-Test fixture; 19-Sensor; 20-Elastic hanging device; 21-Gantry frame; 22-Hook; 23-Industrial control computer; 24-Control system; 25-Test strap; 26-Protective strap; α-Inclination angle. Detailed Implementation

[0049] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0050] In order to simulate the vibration environment of the product structure under real working conditions, a vibration test fixture that can be installed is designed according to the product's shape and structural characteristics. Single vibration table excitation and multi-point maximum value vibration control are key technologies for conducting mechanical environment tests on complex structures of large skin composite materials, which are of great significance for assessing product reliability.

[0051] Example 1

[0052] A specific embodiment of the present invention discloses a vibration testing method for conducting vibration tests on large composite material skin test specimens. The test specimen is specifically an aerospace product with a length of over 6 meters, a large volume, and a weight of over 500 kg. The vibration testing method includes the following steps:

[0053] Step 1: Assemble the test fixture of Example 1, including the following steps:

[0054] Step 11: Connect the base of the test fixture to the table surface of the vertical vibration table using fastening screws.

[0055] Step 12: Connect the two first connectors and the two second connectors to the base of the test fixture using fastening screws. The four first mounting holes on the bases of the first and second connectors are oblong holes. Do not tighten the fastening screws yet, as they are used to adjust the installation position.

[0056] Step 13: The bearing mating seats consist of four square steel seats, and the bushings consist of four circular steel rings. Insert the four bushings into the four bearing mating seats, securing them with a clearance fit. Install the bearing mating seats with the bushings onto the two first connecting pieces and the two second connecting pieces, tilting them upwards at a 3° angle, and secure them with fastening screws. The second connecting pieces have four oblong mounting holes for adjusting the installation position.

[0057] Step 2: Move the test piece onto the test fixture.

[0058] The test piece is held in place by a test strap and connected to an elastic suspension device by fasteners. The hook on the gantry is moved to lift the test piece onto the test fixture on the vertical vibration table.

[0059] Step 3: Secure the two left and two right sleeves of the test piece to the four bearing seats using four bushings. Fine-tune the test piece using the oblong mounting holes on the second connector. Once in place, tighten the test piece securely. The elastic suspension device counteracts the weight of the test piece and the test fixture, ensuring the test piece operates under free-free boundary conditions during vibration testing.

[0060] Step 4: Tighten all the fastening screws at the joints.

[0061] Step 5: Install protective straps on the other two hooks on the gantry using fasteners. Select protective positions in front of and behind the test piece to hold it. Slightly adjust the hooks downwards to loosen the straps, leaving them 20mm away from the test piece. These straps are used to protect the test piece during the test.

[0062] Step 6: Attach the sensor to the outer surface of the test specimen and connect the cable to the control system. The preferred location for attaching the sensor is a relatively rigid part of the test specimen.

[0063] Step 7: The control system applies vibration to the test piece according to the specified test conditions using the vibration table system, achieving the expected vibration response. The control system uses an SD controller, and the test files are configured according to the test conditions.

[0064] The vibration test employs a multi-point maximum value control method, selecting the front, middle, and rear sections of the test specimen with the strongest stiffness as vibration control points. A control system sends an excitation signal to the vertical vibration table, causing the table to vibrate accordingly. This vibration is transmitted to the test specimen through the test fixture, ensuring the response of the control points at the front, middle, and rear sections meets the test requirements.

[0065] Step 8: Remove the sensors from the test specimen after the vibration test.

[0066] Step 9: Remove the fastening screws connecting the test piece and use a hook to lift the test piece to the ground via the elastic suspension device.

[0067] Step 10: Remove the vibration test fixture from the vertical vibration table and lift it to the ground using a crane hook.

[0068] Example 2

[0069] Another specific embodiment of the present invention discloses a vibration testing fixture for clamping skin composite material test specimens in the vibration testing method of Embodiment 1, such as... Figure 1 and Figure 2 As shown, the vibration test fixture includes a first connector 1, a second connector 2, a base 3, and a bearing mating seat 4.

[0070] One end of the first connector 1 and the second connector 2 are fixedly connected to the base 3, and the other end is fixedly connected to the outer surface of the test piece through the bearing mating seat 4.

[0071] like Figure 2 As shown, the first connector 1 includes a base 5 and an upright plate 6 that protrudes outward from the middle of the base.

[0072] like Figure 3 As shown, the base 5 is provided with a first mounting hole 7 to fix the first connector 2 and the base 3 together by means of fasteners.

[0073] In a preferred embodiment, the first mounting hole 7 is an oblong hole, which allows for adjustment of the mounting position of the first connector 1 on the base 3, making installation more flexible.

[0074] Specifically, both the base 5 and the upright plate 6 are flat cuboids, and the width of the upright plate 6 is equal to the width of the base 5.

[0075] To enhance the firmness of the connection between the first connector 1 and the base 3, in this embodiment, there are multiple first mounting holes 7, and these multiple first mounting holes 7 are evenly distributed on both sides of the upright plate 6. For example, there are four first mounting holes.

[0076] like Figure 4 As shown, the upper part of the upright plate 7 is provided with a connecting hole 8 that extends along the thickness direction of the upright plate to connect the test piece with the first connecting piece. Multiple second mounting holes 9 are provided around the connecting hole to securely connect the first connecting piece 1 and the bearing mating seat 4 using fasteners.

[0077] Specifically, both the connecting hole 8 and the second mounting hole 9 are circular holes. The diameter of the second mounting hole 9 is smaller than the diameter of the connecting hole 8.

[0078] like Figure 2 As shown, the structure of the second connector 2 is similar to that of the first connector 1. The difference is that, as... Figure 5 As shown, the second mounting hole on the upright plate of the second connector 2 is a waist-shaped hole, which facilitates fine adjustment of the test piece. After the test piece is in place, the test piece is then clamped and fixed.

[0079] like Figure 6 and Figure 7 As shown, the bearing mating seat 4 includes a main body 10, which is flat and has a square cross-section. A through hole 12, extending along the thickness direction of the main body 10, is located at its center. The through hole 12 corresponds to the connecting hole 8 on the vertical plate 7. The bushing 11 is a hollow cylinder, inserted into the through hole 12 to achieve a fitted and fixed connection with the bearing mating seat 4. Specifically, the bearing mating seat 4 and the bushing 11 have a clearance fit. For example, both the main body and the bushing are made of steel.

[0080] like Figure 7 As shown, in one possible implementation, the thickness of the main body 10 gradually increases from one side to the other, resulting in a certain tilt angle α on the outer surface of the main body 10. For example, the angle α is 3°-5°. This arrangement allows the bearing mating seat to better adapt to the outer surface of the test piece, making the connection between the bearing mating seat and the test piece more secure.

[0081] In addition, the main body 10 is provided with mounting holes for connecting the bearing mating seat 4 with the first connecting member 1 and the second connecting member 2.

[0082] like Figure 1 and Figure 2 As shown, the base 3 is a flat cuboid. One surface of the base 3 has an inwardly recessed circular groove 13, and the opposite surface has an outwardly protruding cylindrical protrusion 14. The groove 13 and the protrusion 14 are connected. The end face of the protrusion 14 has multiple mounting holes to achieve a fixed connection between the test fixture and the vibration table.

[0083] In a preferred embodiment, such as Figure 1 As shown, multiple reinforcing members 15 are provided between the side of the protrusion 14 and the surface of the base 3 where the protrusion is located, to enhance the load-bearing capacity of the base 3 and improve the safety of the test. The multiple reinforcing members 15 are arranged radially around the protrusion.

[0084] Specifically, the reinforcing member 15 is a flat triangular prism with a right-angled triangle cross-section. The two legs of the right-angled triangle are connected to the side of the protrusion and the surface of the base, respectively. The reinforcing member 15 extends from the protrusion 14 to the edge of the base 3.

[0085] In one possible implementation, mounting holes are provided at the four corners of the base 3 to connect the base 3 to the first connector 1 and the second connector 2. For example, the mounting holes at the four corners of the base are oblong holes, corresponding to the oblong holes on the bases of the first connector 1 and the second connector 2.

[0086] Specifically, there are two first connectors 1 and two second connectors 2. The two first connectors and the two second connectors are fixed to the same side of the base 3. For example, the two first connectors are arranged opposite each other along one long side of the base, and the two second connectors are arranged opposite each other along the other long side of the base.

[0087] like Figure 8As shown, the test piece of this invention is a large-scale composite material test piece with a complex structure. The test piece is cylindrical in shape. Two strip-shaped protrusions are provided on opposite sides of the test piece. Each strip-shaped protrusion has two outwardly protruding sleeve posts, which are fitted and fixed to the bushings 11 on the bearing mating seat 4, thereby realizing the connection between the test piece 16 and the test fixture. Specifically, the sleeve posts are metal posts.

[0088] The test fixture in this embodiment is manufactured using the following method:

[0089] Upon receiving the digital model, the material was cut according to the digital model, and the material was 6061-T6.

[0090] Procurement is carried out according to the material cutting list of the process.

[0091] The materials are tested after arriving at the factory.

[0092] After passing the inspection, the following processing steps will be performed:

[0093] Rough machining: CNC machining is performed according to the theoretical dimensions of the digital model, with a single-sided allowance of 3-5mm; rough machining removes excess material.

[0094] After rough machining, artificial aging is performed. During artificial aging, the workpiece is placed in an aging furnace for aging. Artificial aging takes 48 hours and the aging temperature is 150-170 degrees Celsius. The main purpose of artificial aging is to remove stress and prevent deformation.

[0095] After artificial aging, a finishing process is carried out. CNC machining is performed according to the theoretical dimensions of the digital model, and inspection is carried out after finishing.

[0096] After passing the inspection, the next process, final assembly, is carried out. Assembly is performed according to the theoretical numerical model. After the assembly passes the inspection, an inspector will check and issue an inspection report and certificate of conformity.

[0097] Example 3

[0098] Another specific embodiment of the present invention discloses a vibration testing system, such as... Figure 8 As shown, the system includes the test fixture 18, vibration table system 17, sensor 19, elastic suspension device 20 (rubber rope suspension), gantry frame 21, hook 22, industrial computer 23, and control system 24, as described in Embodiment 2. The test fixture 18, vibration table system 17, and sensor 19 are electrically connected to the control system 24, and the control system 24 is electrically connected to the industrial computer 23.

[0099] The vibration table system 17 provides vibration, and the test fixture 18 transmits the vibration from the vibration table system 17 to the test specimen 16. The elastic suspension device 20 suspends the test specimen 16, and the gantry 21 provides support for the elastic suspension device. An industrial computer is used to set the test parameters. The control system controls the vibration table system to apply vibration to the test specimen according to the test parameters set by the industrial computer, achieving the expected vibration response. Sensors collect the vibrations sensed by the test specimen and transmit them to the control system.

[0100] Specifically, the vibration table system includes a vibration table and a support. The vibration table is fixed on the support and fixedly connected to the test fixture, which is fixedly connected to the test piece. Specifically, the vibration table is a vibration table capable of providing vertical vibration.

[0101] One end of the flexible suspension device 20 is connected to the gantry 21, and the other end is connected to the test piece 18.

[0102] In one specific embodiment, the gantry is equipped with a lifting chain, one end of which is equipped with a hook 22, and an elastic hanging device 20 is hung on the hook 22.

[0103] In addition, the vibration testing system of this embodiment also includes a test strap 25 to hold and suspend the test piece on the elastic suspension device.

[0104] Depending on the length of the test specimen, multiple elastic suspension devices are used, and these devices are distributed along the length of the test specimen. This arrangement improves the stability of the suspended test specimen, thereby increasing the accuracy of the vibration test. For example, two elastic suspension devices are used.

[0105] Considering that the test specimen of this invention is a large, complex composite material structure, exceeding 6 meters in length, large in volume, and weighing over 500 kg, an aerospace product, an accidental drop would result in direct damage and incalculable loss. Therefore, in another possible embodiment, such as... Figure 8 As shown, the present invention also includes a structure to prevent the test specimen from accidentally falling, namely, an additional protective strap 26. This protective strap 26 is not connected to the elastic suspension device, but is directly hung on the hook. Under normal circumstances, the protective strap 26 does not bear any load, and only bears load in case of an accident. This does not affect the normal conduct of the modal test, and can prevent the test specimen from falling accidentally, thus effectively improving the safety of the modal test.

[0106] Considering that the flexible suspension device may slide on the hook after being hung on it, in a preferred embodiment, a limiting part (not shown in the figure) is provided on the hook. This feature prevents the flexible suspension device from sliding on the hook after being hung on it, greatly improving the stability of the flexible suspension device on the hook.

[0107] Specifically, the limiting part is a protrusion or a groove.

[0108] When the limiting part is a protrusion, there are two protrusions with a gap between them, and one end of the elastic hanging device is stuck in the gap; when the limiting part is a groove, one end of the elastic hanging device falls into the groove.

[0109] Sensor 19 is fixed to the outer surface of the test piece. Specifically, there are multiple sensors, which are distributed on the outer surface of the test piece and connected to the control system.

[0110] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A vibration testing method, characterized in that, The procedure for conducting vibration tests on composite skin specimens includes the following steps: Step 1: Assemble the test fixture; Step 2: Move the test specimen onto the test fixture; Step 3: Connect and fix the two sleeves on the left and two sleeves on the right of the test piece to the four bearing mating seats through four bushings, and fine-tune the test piece using the waist-shaped mounting holes on the second connector. After installation, tighten and fix the test piece. Step 4: Tighten all the fastening screws at the joints; Step 5: Attach the sensor to the outer surface of the test piece and connect the cable to the control system; Step 6: The control system controls the vibration table system to apply vibration to the test piece and conduct the vibration test; The test fixture includes a first connector, a second connector, a base, and a bearing mating seat; One end of the first connector and the second connector are respectively connected to the base, and the other end are respectively connected to the outer surface of the test piece through the bearing mating seat; The first connector includes a base and an upright plate protruding outward from the base; the base is provided with a first mounting hole to fix the first connector and the base together by fasteners; the upper part of the upright plate is provided with a connecting hole that extends along the thickness direction of the upright plate to realize the connection between the test piece and the first connector. The bearing mating seat includes a main body, the thickness of which gradually increases from one side to the other, so that the outer surface of the main body has a certain tilt angle, the tilt angle being 3°-5°; The vibration test fixture is used to clamp skin composite material test pieces during vibration testing. The test pieces are aerospace products with a length of more than 6 meters, a large volume, and a weight of more than 500 kg.

2. The vibration testing method according to claim 1, characterized in that, Step 1 includes the following steps: Step 11: Connect the base of the test fixture to the table surface of the vertical vibration table using fastening screws; Step 12: Connect the two first connectors and the two second connectors to the base of the test fixture using fastening screws; Step 13: Install the 4 bushings into the 4 bearing mating seats and fix them in place.

3. The vibration testing method according to claim 1, characterized in that, Between step 4 and step 5, there is also step 4a: installing protective straps to protect the test specimen.

4. The vibration testing method according to claim 3, characterized in that, Step 4a includes the following steps: Install protective straps on the other two hooks on the gantry using fasteners to hold the test piece, and then slightly adjust the hooks downwards to loosen the straps and move them a certain distance away from the test piece.

5. The vibration testing method according to claim 2, characterized in that, The bushing and the bearing seat are clearance fit.

6. The vibration testing method according to claim 2, characterized in that, Both the bushing and the bearing mating seat are made of steel.

7. The vibration testing method according to claim 1, characterized in that, Step 6 is followed by step 7: removing the sensors from the test piece.

8. The vibration testing method according to claim 7, characterized in that, Step 7 is followed by step 8: removing the fastening screws connected to the test piece and using a hook to lift the test piece to the ground via an elastic suspension device.

9. The vibration testing method according to claim 8, characterized in that, Step 8 is followed by step 9: removing the vibration test fixture from the vertical vibration table.

10. A vibration testing system, characterized in that, The vibration testing system is used to perform the vibration testing method according to any one of claims 1-9, and the vibration testing system includes a test fixture.

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