A multi-layer adjustable screw vibration test tool and a test method thereof

Abstract

This application relates to the field of vibration testing fixture technology, specifically to a multi-layer adjustable screw vibration testing fixture and its testing method. The fixture includes a bottom base, vertical guide posts, a middle support, a top pressure plate, and a buffer structure. The bottom base has mounting holes and horizontal leveling bolts. The middle support is slidably mounted on the vertical guide posts via height-adjusting nuts, allowing for stepless height adjustment and locking. The middle support has a multi-hole array to accommodate screws of different sizes. The top pressure plate is fixed by locking nuts, and a buffer structure is provided between it and the middle support. The testing method includes: installing the leveling fixture, calculating the target height, adjusting and locking the middle support, placing the screw specimen, installing the top pressure plate and compressing the buffer, applying preload by locking, starting the vibration table test, and disassembling and inspecting.

Description

Technical Field

[0001] This application relates to the field of vibration testing fixture technology, and more specifically, to a multi-layer adjustable screw vibration testing fixture and its testing method. Background Technology

[0002] As fundamental components of mechanical connections, screws possess three key attributes: reliability, safety, and economy in fields such as rail transportation, aerospace, automotive manufacturing, and precision machinery. With the rapid development of my country's manufacturing industry, the requirements for screw anti-loosening performance are increasingly stringent. However, traditional vibration testing methods have long been plagued by the "three lows" problem: poor adaptability, difficulty in adjustment, and low versatility. Under vibration environments (such as vehicle movement and equipment operation), screws are prone to loosening, breakage, and stripping. Traditional testing methods typically employ a single vibration table or simple fixtures for vibration testing, and their "single-layer fixing" approach has limited effectiveness.

[0003] In recent years, multi-layer clamps or adjustable fixtures have been gradually applied to vibration testing. However, after fracturing—that is, after clamping—screw specimens are difficult to maintain a stable preload during vibration. Furthermore, different screw specifications require frequent fixture changes, which limits the improvement of production capacity—that is, testing efficiency. Ultrasonic technology has been proven to promote the desorption of coal and rock gas. By analogy, buffer structures have been proven to absorb vibration energy and protect specimens. However, existing buffer structures are mostly single springs or rubber pads, which cannot adapt to vibration conditions with different frequencies and amplitudes. Moreover, they are only applicable to specific screw specifications and cannot be extended to simultaneous testing of multiple specifications. In addition, although manual adjustment of height or level has some effect, it may cause short-term effects such as low adjustment accuracy and long operation time.

[0004] Therefore, there is an urgent need for a screw vibration testing fixture that can achieve multi-layer adjustable, multi-specification adaptability, and effective buffering, so as to make full use of the multi-layer structure as a carrier and utilize the synergistic effect of the height-adjustable nut and the buffer structure to achieve efficient and reliable screw anti-loosening performance testing. Summary of the Invention

[0005] In view of this, in order to solve the above-mentioned problems in the prior art, this application provides a multi-layer adjustable screw vibration testing fixture and its testing method.

[0006] The embodiments of this application are implemented as follows: In a first aspect, this application provides a multi-layer adjustable screw vibration testing fixture, including a bottom base, multiple vertical guide pillars, a middle support, a top pressure plate, and a buffer structure: The bottom base is made of high-strength steel. The bottom of the bottom base has multiple mounting holes for bolting to the vibration table. A horizontal leveling bolt is threaded to each of the four corners of the bottom base. The lower end of the vertical guide post is vertically fixed to the upper surface of the bottom base, and the multiple vertical guide posts are parallel to each other. The four corners of the middle layer bracket are slidably sleeved on the corresponding vertical guide posts via linear bearings. A height adjustment nut is sleeved on the outer side of each vertical guide post. The height adjustment nut is connected to the vertical guide post via fine thread. The lower surface of the middle layer bracket is supported on the upper end face of the height adjustment nut. Rotating the height adjustment nut can adjust the height of the middle layer bracket in the vertical direction and lock it. The top plate has through holes at its four corners and is slidably fitted onto the top of the corresponding vertical guide post through these through holes. Each vertical guide post has a locking nut threadedly connected to its top at the top of the top plate. The lower end of the locking nut presses against the upper surface of the top plate. The top plate has through holes coaxial with each hole at the position corresponding to the multi-hole array. The bottom base, the middle support and the top pressure plate are all machined with a multi-hole array, which consists of multiple through threaded holes or open holes with different diameters, for fixing screw specimens with different nominal diameters; The buffer structure is disposed between the top pressure plate and the middle support. The upper end face of the buffer structure is in contact with the lower surface of the top pressure plate, and the lower end face is in contact with the upper surface of the middle support, for absorbing vibration energy.

[0007] In one possible implementation, the buffer structure consists of spring washers fitted around the outside of the plurality of vertical guide posts and a solid rubber buffer layer laid on the upper surface of the middle support.

[0008] In one possible implementation, the vertical guide post is a hollow cylindrical steel pipe with a wear-resistant layer on its outer surface, and the mounting hole is an oblong hole with its long axis arranged horizontally to finely adjust the relative horizontal position between the bottom base and the vibration table.

[0009] In one possible implementation, the multi-hole array includes multiple hole groups with different diameters, arranged in a gradually increasing order of hole diameter to accommodate screws of sizes M2, M3, M4, M5, and M6, with at least two holes for each size.

[0010] In one possible implementation, a replaceable buffer pad is sandwiched between the middle support and the top pressure plate, and the buffer pad has clearance holes corresponding to the positions of the multi-hole array.

[0011] In one possible implementation, each of the vertical guide posts is threaded with a locking nut, which is located below the height adjusting nut and fits against its lower end face, and is used to lock the height adjusting nut in place to prevent it from vibrating and loosening.

[0012] In one possible implementation, the upper surface of the middle support is further machined with a V-groove or locating pin hole for positioning the head of the screw specimen, the V-groove or locating pin hole being alternately arranged with some of the holes in the multi-hole array.

[0013] In one possible implementation, each of the vertical guide pillars has a height scale marking engraved axially on its cylindrical surface. The zero position of the height scale marking corresponds to the position when the lower surface of the middle layer support contacts the upper surface of the bottom base, and is used to directly read the lifting distance of the middle layer support.

[0014] In one possible implementation, at least two limiting sleeves of different axial lengths are provided between the bottom base and the middle support, and the limiting sleeves are sleeved on the vertical guide post and located below the height adjusting nut.

[0015] Secondly, this application provides a test method for a multi-layer adjustable screw vibration test fixture, comprising: The bottom base is fixed to the vibration table surface with bolts through the mounting holes, and then the leveling bolts are rotated to make the entire fixture level. Obtain the length parameters of the screw to be tested and the stroke parameters of the vibration table, and calculate the target height value required for the middle layer support based on the length parameters and stroke parameters; Rotate the height adjusting nut while observing the height scale markings on the vertical guide post, adjust the middle layer bracket to the target height value, and then tighten the anti-loosening locking nut to lock it in place; Multiple screw specimens with different nominal diameters were placed into the corresponding holes in the multi-hole array of the middle layer support, with the heads of the screw specimens facing upwards. The top plate is fitted onto the top of the vertical guide post, and the through hole or threaded hole on the top plate is aligned with the head of each screw specimen. Then the top plate is pressed down to compress the buffer structure to a predetermined compression amount. Tighten the locking nut to fix the top plate at the current height, thereby applying an axial preload to the screw specimen; Start the vibration table and conduct the vibration test according to the set vibration frequency, amplitude and test time; After the test, loosen the locking nut and the height adjusting nut in sequence, remove the screw test piece, check for looseness, breakage or stripping, and record the test results.

[0016] The technical solution provided in this application can achieve at least the following beneficial effects: This application provides a multi-layer adjustable screw vibration testing fixture and its testing method. A rigid support frame is constructed through a bottom base and vertical guide columns. Leveling bolts at the four corners enable rapid calibration of the fixture's overall levelness, ensuring uniform transmission of vibration loads. The middle layer support is slidably mounted on the vertical guide columns via linear bearings, and uses a height adjustment nut with fine threads to achieve stepless lifting and locking from 0 to 50 mm. The height adjustment distance can be intuitively read using the height scale markings on the guide columns, significantly improving the adaptability to screws of different lengths and vibration table travel. The multi-hole array on the upper surface of the middle layer support uses M2 to M6 screws. The gradient hole design supports simultaneous fixing of various screw sizes, reducing the frequency of tooling changes; the top pressure plate applies axial preload through the locking nut, and a spring washer and / or rubber buffer layer are placed between it and the middle support, along with replaceable polyurethane or silicone rubber buffer pads, effectively absorbing vibration energy and protecting screws and tooling from impact damage; the anti-loosening locking nut provides double locking for the height adjustment nut, preventing vibration-induced loosening; V-grooves or locating pin holes provide anti-rotation positioning for non-standard screws; the waist-shaped mounting hole supports horizontal fine-tuning, further improving versatility; the limit sleeve provides an alternative to stepped height adjustment.

[0017] The test method sequentially performs the following steps: tooling fixation and leveling, target height calculation, middle layer bracket adjustment and locking, screw specimen installation, top layer pressure plate pre-compression buffering, locking and applying pre-tightening force, vibration test and result recording. The logic chain is complete and the input and output are clear.

[0018] This multi-layer adjustable screw vibration testing fixture and its testing method significantly improve the versatility, ease of adjustment, testing efficiency, and repeatability of screw vibration testing through the synergistic effect of the aforementioned structure and method, while reducing test preparation costs and time. It is suitable for testing the anti-loosening performance of screws in multiple fields such as rail transportation, aerospace, and automobile manufacturing. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a front view schematic diagram of a multi-layer adjustable screw vibration testing fixture shown in an exemplary embodiment of this application; Figure 2 This is a schematic diagram of the overall structure of a multi-layer adjustable screw vibration testing fixture shown in an exemplary embodiment of this application; Figure 3 This is a schematic diagram of a test method for a multi-layer adjustable screw vibration test fixture, as illustrated in an exemplary embodiment of this application.

[0021] Figure label: 1. Horizontal leveling bolts; 2. Bottom base; 3. Vertical guide post; 4. Middle layer support; 5. Top layer pressure plate; 6. Buffer structure; 7. Locking nut; 8. Height adjustment nut; 9. Multi-hole array. Detailed Implementation

[0022] To make the objectives, implementation methods and advantages of this application clearer, the exemplary implementation methods of this application will be clearly and completely described below with reference to the accompanying drawings of the exemplary embodiments of this application. Obviously, the exemplary embodiments described are only some embodiments of this application, and not all embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0023] It should be noted that the brief descriptions of terms in this application are only for the convenience of understanding the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise stated, these terms should be understood in their ordinary and common meaning.

[0024] The terms "first," "second," "third," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar or related objects or entities, and do not necessarily imply a specific order or sequence, unless otherwise specified. It should be understood that such terms are interchangeable where appropriate.

[0025] The terms “comprising” and “having”, and any variations thereof, are intended to cover but not exclude inclusion, for example, a product or device that includes a range of components is not necessarily limited to all of the components that are clearly listed, but may include other components that are not clearly listed or that are inherent to such product or device.

[0026] Next, the technical solutions of this application and how they solve the aforementioned technical problems will be described in detail through embodiments and in conjunction with the accompanying drawings. The embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application.

[0027] In one exemplary embodiment, such as Figure 1 and Figure 2As shown, a multi-layer adjustable screw vibration testing fixture is provided. In this embodiment, the testing fixture may include a bottom base 2, multiple vertical guide pillars 3, a middle support 4, a top pressure plate 5, and a buffer structure 6. The bottom base 2 is made of high-strength steel. The bottom of the bottom base 2 has multiple mounting holes for bolt connection with the vibration table. A horizontal leveling bolt 1 is threaded to each of the four corners of the bottom base 2. The lower end of the vertical guide post 3 is vertically fixed to the upper surface of the bottom base 2, and the multiple vertical guide posts 3 are parallel to each other. The four corners of the middle layer bracket 4 are slidably sleeved on the corresponding vertical guide post 3 via linear bearings. A height adjustment nut 8 is sleeved on the outer side of each vertical guide post 3. The height adjustment nut 8 is connected to the vertical guide post 3 by fine thread. The lower surface of the middle layer bracket 4 is supported on the upper end face of the height adjustment nut 8. Rotating the height adjustment nut 8 can adjust the height of the middle layer bracket 4 in the vertical direction and lock it. The top plate 5 has through holes at its four corners and is slidably fitted onto the top of the corresponding vertical guide post 3 through these through holes. Each vertical guide post 3 has a locking nut 7 threadedly connected to its top at the top of the top plate 5. The lower end face of the locking nut 7 presses against the upper surface of the top plate 5. The top plate 5 has through holes coaxial with each hole at the position corresponding to the multi-hole array 9. The bottom base 2, the middle support 4, and the top pressure plate 5 are all machined with a multi-hole array 9. The multi-hole array 9 consists of multiple through threaded holes or open holes with different diameters, which are used to fix screw specimens with different nominal diameters. The buffer structure 6 is disposed between the top pressure plate 5 and the middle support 4. The upper end face of the buffer structure 6 is in contact with the lower surface of the top pressure plate 5, and the lower end face is in contact with the upper surface of the middle support 4, for absorbing vibration energy.

[0028] In one embodiment, the multi-layer adjustable screw vibration testing fixture is mainly used to simulate actual vibration conditions in fields such as rail transportation, aerospace, and automobile manufacturing, and to conduct vibration impact tests on screw fasteners to test their anti-loosening performance.

[0029] The bottom base 2 is made of high-strength steel to ensure sufficient rigidity and vibration resistance. The bottom base 2 is a rectangular flat plate structure with multiple mounting holes on its bottom for bolt connection with the vibration table. In this embodiment, there are four mounting holes, located near the four corners of the base. A horizontal leveling bolt 1 is threaded to each of the four corners of the bottom base 2. The horizontal leveling bolt 1 passes through the threaded through holes at the four corners of the base, and its lower end can contact the vibration table surface or support plane. By rotating the bolt, the height of the four corners of the base can be finely adjusted, thereby adjusting the levelness of the entire fixture.

[0030] The number of vertical guide posts 3 is at least two, and in this embodiment, four are preferred. They are respectively vertically fixed to the four corners of the upper surface of the bottom base 2. The lower end of the vertical guide post 3 can be firmly fixed to the bottom base 2 by interference fit, welding or threaded connection. The vertical guide posts 3 are parallel to each other to ensure that the middle layer support 4 and the top layer pressure plate 5 can be raised and lowered smoothly.

[0031] The middle support 4 is a rectangular plate with linear bearings installed at its four corners. These bearings slide onto the corresponding vertical guide posts 3, reducing sliding friction and ensuring smooth lifting. Each vertical guide post 3 has a height adjustment nut 8 on its outer side, connected to the vertical guide post 3 via a fine-pitch thread. The fine-pitch thread has the advantages of good self-locking and high adjustment accuracy. The lower surface of the middle support 4 is directly supported on the upper surface of the height adjustment nut 8. When the height adjustment nut 8 is rotated, the nut moves up and down along the vertical guide post 3, thereby driving the middle support 4 to lift synchronously. After rotation stops, the thread friction between the nut and the guide post locks the height position.

[0032] The top plate 5 is also a rectangular plate with through holes at its four corners. It is slidably fitted onto the top of the corresponding vertical guide post 3 through these through holes. Each vertical guide post 3 has a locking nut 7 threaded to its top. The lower end of the locking nut 7 presses against the upper surface of the top plate 5. The top plate 5 has through holes coaxial with each hole at the position of the multi-hole array 9 of the middle support 4. The diameter of the through holes in the top plate 5 is larger than the diameter of the screw head so that the screw head can pass through.

[0033] The upper surfaces of the bottom base 2, the middle support 4, and the top pressure plate 5 are machined with a multi-hole array 9. The multi-hole array 9 consists of multiple through threaded holes or open holes with different diameters, which are used to fix screw specimens with different nominal diameters. For example, for tests that need to simulate the tightening state of bolts, the multi-hole array 9 can be set as threaded holes, and the screws can be screwed in directly; for tests that need to simulate through bolts or screws with nuts, the multi-hole array 9 can be set as open holes, and the screws are fixed with nuts at the lower end after passing through the open holes.

[0034] The buffer structure 6 is disposed between the top pressure plate 5 and the middle support 4. The upper end face of the buffer structure 6 contacts the lower surface of the top pressure plate 5, and the lower end face contacts the upper surface of the middle support 4. Its function is to absorb part of the vibration energy during the vibration test, reduce the impact damage to the screw specimen and the tooling itself, and at the same time avoid rigid collision between the top pressure plate 5 and the middle support 4. In this embodiment, the buffer structure 6 can be a compression spring sleeved on the outside of each vertical guide post 3, or it can be an elastic pad laid between the two plates.

[0035] In one embodiment, buffer structure 6 has two specific implementations, which can be used individually or in combination.

[0036] Method 1: The buffer structure 6 is a spring washer fitted on the outside of each vertical guide post 3. Each vertical guide post 3 is fitted with one or more helical compression springs. The springs are located between the middle support 4 and the top pressure plate 5. When the top pressure plate 5 is locked downwards, the springs are compressed, generating elastic preload. During vibration, the elastic deformation of the springs can absorb and release vibration energy, effectively reducing the impact.

[0037] Method 2: The buffer structure 6 is a whole piece of rubber buffer layer laid on the upper surface of the middle layer support 4. The rubber buffer layer can be made of natural rubber or nitrile rubber. The rubber layer is directly pasted or fixed to the upper surface of the middle layer support 4 by positioning pins. The lower surface of the top layer pressure plate 5 is directly pressed on the rubber layer. The rubber layer has good damping characteristics and can significantly attenuate the transmission of high frequency vibration.

[0038] In practical applications, spring washers can also be used in combination with rubber buffer layers: holes are made in the rubber layer corresponding to the guide post positions, and spring washers are fitted onto the guide post and press down on the rubber layer. This embodiment is the preferred combination to achieve the best vibration reduction effect.

[0039] In one embodiment, the vertical guide post 3 is a hollow cylindrical steel pipe. The hollow structure significantly reduces the overall weight of the tooling while ensuring bending stiffness, making it easy to handle and install. The outer surface of the vertical guide post 3 is provided with a wear-resistant layer, which can be hard chrome plating or nitriding. The wear-resistant layer can reduce wear when the linear bearing slides and extend the tooling life.

[0040] The mounting holes are oblong holes, with their long axis pointing horizontally. In this embodiment, the four mounting holes at the bottom of the base 2 are all oblong holes, with their long axis pointing to either the long side or the short side of the base. Alternatively, they can be designed according to the mounting hole distribution of the vibration table. The oblong holes allow the fixture to be finely adjusted in a certain range in the horizontal direction relative to the vibration table surface, thereby adapting to the installation position alignment of different vibration tables or different test requirements and improving the versatility of the fixture.

[0041] In one embodiment, the multi-hole array 9 includes multiple hole groups with different diameters. Each hole group is arranged in a gradual manner according to the order of hole diameter from small to large. For example, M2, M3, M4, M5, and M6 threaded holes or smooth holes are arranged sequentially from one side of the middle layer bracket 4 to the other side. There are at least two holes of each specification so as to conduct parallel tests of multiple screws of the same specification at the same time.

[0042] In this embodiment, the middle layer support 4 is a rectangular plate with five rows of holes along its length. The first row has two M2 holes, the second row has two M3 holes, the third row has two M4 holes, the fourth row has two M5 holes, and the fifth row has two M6 holes. The center distance between each hole is not less than 15mm to avoid interference between screws during testing. The gradual arrangement allows operators to quickly identify the corresponding specification positions and reduces the number of tooling changes.

[0043] In addition, to accommodate a wider range of screw sizes, the multi-hole array 9 can also include larger holes such as M8 and M10, or add imperial thread holes such as 1 / 4 inch and 5 / 16 inch, depending on the user's specific needs.

[0044] In one embodiment, a replaceable buffer pad is added between the middle support 4 and the top pressure plate 5.

[0045] The buffer pad is independent of the buffer structure 6 and can be used in combination. The buffer pad is a polyurethane pad or a silicone rubber pad. The buffer pad has clearance holes corresponding to the positions of the multi-hole array 9. The diameter of the clearance holes is slightly larger than the outer diameter of the screw head to ensure that the screw head can pass through the pad without being squeezed.

[0046] The advantages of replaceable buffer pads are: pads made of different materials have different damping characteristics and compression rebound rates, allowing users to select appropriate pads based on the frequency, amplitude, and sensitivity of the screw material in the vibration test. For example, a harder polyurethane pad can be used for high-frequency, low-amplitude tests, while a softer silicone rubber pad can be used for low-frequency, high-amplitude tests. Furthermore, when the pad ages or is damaged, it can be directly removed and replaced without replacing the entire fixture.

[0047] In one embodiment, a locking nut 7 is threaded onto each vertical guide post 3. The locking nut 7 is located below the height adjusting nut 8, and its upper end face is in contact with the lower end face of the height adjusting nut 8. After the height adjusting nut 8 is rotated to the target position, the locking nut 7 is tightened upwards so that the two nuts are against each other. By using the double-nut locking principle, the height adjusting nut 8 is effectively prevented from loosening on its own during strong vibration, thereby ensuring that the height position of the middle support 4 remains unchanged throughout the entire test cycle.

[0048] In this embodiment, the anti-loosening locking nut 7 and the height adjusting nut 8 use the same fine thread specification. During installation, the height adjusting nut 8 is first used to coarsely adjust and lock the position, and then the anti-loosening locking nut 7 is tightened to apply the counterforce. After the test, the anti-loosening locking nut 7 is loosened first, and then the height adjusting nut 8 is rotated to disassemble.

[0049] In one embodiment, an auxiliary positioning structure is added to the upper surface of the middle support 4.

[0050] For some non-standard shaped screw specimens, relying solely on the hole positions of the multi-hole array 9 may not provide reliable fixation. Therefore, a V-groove or locating pin hole is machined on the upper surface of the middle layer support 4 to position the screw specimen head. The V-groove is opened along the length or width of the middle layer support 4, with a cross-section of 90° or 120° V-shape, used to place cylindrical or edged screw heads. The V-groove can automatically center and prevent circumferential rotation of the specimen. The locating pin hole is a precision round hole that can cooperate with the pre-set locating pin on the screw specimen to achieve precise angular positioning.

[0051] V-grooves or locating pin holes are alternately arranged with some holes in the multi-hole array 9. That is, each hole has a corresponding V-groove or locating pin hole, so that after each screw specimen is inserted into the hole, its head can be constrained by the V-groove or locating pin at the same time, which further improves the positional stability during the test.

[0052] In one embodiment, each vertical guide post 3 has a height scale marking engraved axially on its cylindrical surface. The scale lines can be laser engraved or chemically etched to ensure clarity and wear resistance. The zero position of the height scale marking corresponds to the position where the lower surface of the middle layer bracket 4 contacts the upper surface of the bottom layer base 2.

[0053] When the user rotates the height adjustment nut 8 to raise the middle support 4, the lifting distance of the middle support 4 can be directly obtained by reading the scale value aligned with the lower edge of the middle support 4 or the lower edge of the linear bearing. No additional measuring tools are required, which greatly improves the adjustment efficiency and is especially suitable for scenarios that require repeated height adjustments or multiple sets of comparative tests.

[0054] In one embodiment, an alternative height adjustment method is provided, in which at least two limiting sleeves of different axial lengths are provided between the bottom base 2 and the middle support 4. The limiting sleeves are fitted onto the vertical guide post 3 and located below the height adjusting nut 8. The limiting sleeves are hollow cylinders with an inner diameter slightly larger than the outer diameter of the vertical guide post 3, allowing them to slide freely.

[0055] When stepless adjustment is not required and only a few fixed height positions are needed, the height adjustment nut 8 can be removed, and a limit sleeve of the corresponding length can be directly selected and placed on the guide post. Then, the lower surface of the middle layer bracket 4 is pressed onto the upper end face of the limit sleeve, and the top layer pressure plate 5 is fixed with the locking nut 7.

[0056] For example, by providing limiting sleeves of three lengths—30mm, 40mm, and 50mm—three stepped heights can be achieved. This solution has a simpler structure, eliminates the issue of threaded loosening, and is suitable for batch repeated testing.

[0057] Corresponding to the aforementioned embodiment of a multi-layer adjustable screw vibration testing fixture, this application also provides an embodiment of a testing method for a multi-layer adjustable screw vibration testing fixture.

[0058] In one exemplary embodiment, such as Figure 3 As shown, the test method for this multi-layer adjustable screw vibration test fixture may include the following steps: Step 100: Fix the bottom base 2 to the vibration table surface with bolts through the mounting holes, and then rotate the leveling bolt 1 to make the entire fixture level. Step 200: Obtain the length parameters of the screw to be tested and the stroke parameters of the vibration table, and calculate the target height value required for the middle layer support 4 based on the length parameters and stroke parameters; Step 300: Rotate the height adjusting nut 8 while observing the height scale markings on the vertical guide post 3, adjust the middle layer bracket 4 to the target height value, and then tighten the anti-loosening locking nut 7 to lock it in place; Step 400: Place multiple screw specimens with different nominal diameters into the corresponding holes in the multi-hole array 9 of the middle layer support 4, with the heads of the screw specimens facing upwards. Step 500: Place the top plate 5 on the top of the vertical guide post 3, align the through hole or threaded hole on the top plate 5 with the head of each screw test piece, and then press the top plate 5 down to compress the buffer structure 6 to a predetermined compression amount. Step 600: Tighten the locking nut 7 to fix the top plate 5 at the current height, thereby applying an axial preload to the screw specimen; Step 700: Start the vibration table and conduct the vibration test according to the set vibration frequency, amplitude and test time; Step 800: After the test, loosen the locking nut 7 and the height adjusting nut 8 in sequence, remove the screw test piece, check its looseness, breakage or disengagement, and record the test results.

[0059] In one embodiment, the test method of the multi-layer adjustable screw vibration test fixture is specifically implemented as follows: Install the fixtures and level them: Fix the bottom base 2 to the vibration table surface with bolts through the mounting holes. Do not tighten the bolts completely yet, leaving room for fine adjustment. Then place the level on the middle support 4 or the top pressure plate 5. Rotate the leveling bolts 1 at the four corners of the bottom base 2 and observe the level until the entire fixture is level. Finally, tighten the vibration table connecting bolts.

[0060] Calculate the target height: Obtain the length parameters of the screw to be tested and the stroke parameters of the vibration table. The target height value H required by the middle support 4 usually meets the following: after the screw is installed, a pre-tightening space of 1~2mm is left above its head, and the buffer structure 6 is in a suitable compression after the top pressure plate 5 is pressed down. The calculation formula can be: H = L + H1 + H2, where H1 is the distance from the upper surface of the bottom base 2 to the vibration table surface, and H2 is the pre-tightening gap.

[0061] Adjust the height of the middle support 4: Rotate the height adjusting nut 8 while observing the height scale markings on the vertical guide post 3. Adjust the middle layer bracket 4 to the target height value calculated in step two. After adjustment, tighten the anti-loosening locking nut 7 upwards to ensure it fits tightly against the lower end face of the height adjusting nut 8, achieving double locking.

[0062] Place the screw test piece: Multiple screw specimens with different nominal diameters were placed into the corresponding holes in the multi-hole array 9 of the middle layer support 4. For threaded holes, the screws were screwed in to the appropriate depth. For plain holes, the screws were passed through and pre-tightened with nuts below the bottom layer to ensure that the head of the screw specimen was facing upward and that the head was completely exposed on the upper surface of the middle layer support 4.

[0063] Install the top pressure plate 5 and pre-compress the buffer structure 6: Place the top plate 5 on the top of the vertical guide post 3 and slowly lower it so that the through hole on the top plate 5 is aligned with the head of each screw specimen. Then press the top plate 5 down evenly to compress the buffer structure 6 to the predetermined compression amount. This pre-compression amount can be adjusted according to the intensity of the vibration test.

[0064] Lock the top plate 5: Tighten the locking nut 7 to fix the top plate 5 at the current height. The tightening torque should be moderate, ensuring that the top plate 5 will not loosen during vibration, while also avoiding excessive pressure on the screw head. At this time, the screw specimen is subjected to a downward axial preload from the top plate 5, simulating the actual installation state.

[0065] Perform vibration test: Start the vibration table and conduct a vibration test according to the vibration frequency, amplitude and test time set in the test outline. During the test, the buffer structure 6 of the tooling continuously absorbs vibration energy to protect the screws and tooling.

[0066] Post-test inspection: After the test, turn off the vibration table, loosen the locking nut 7 and the height adjusting nut 8 in sequence, lift the top platen 5 upwards, take out the screw specimen, check whether each screw has loosening, breakage, stripping, thread wear and other failure phenomena, and record the test results. The anti-loosening performance of the screw is evaluated based on the recorded data.

[0067] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially as indicated, these steps are not necessarily executed in the indicated order. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps.

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A multi-layer adjustable screw vibration testing fixture, characterized in that, Includes a bottom base, multiple vertical guide pillars, a middle support structure, a top pressure plate, and a cushioning structure: The bottom base is made of high-strength steel. The bottom of the bottom base has multiple mounting holes for bolting to the vibration table. A horizontal leveling bolt is threaded to each of the four corners of the bottom base. The lower end of the vertical guide post is vertically fixed to the upper surface of the bottom base, and the multiple vertical guide posts are parallel to each other. The four corners of the middle layer bracket are slidably sleeved on the corresponding vertical guide posts via linear bearings. A height adjustment nut is sleeved on the outer side of each vertical guide post. The height adjustment nut is connected to the vertical guide post via fine thread. The lower surface of the middle layer bracket is supported on the upper end face of the height adjustment nut. Rotating the height adjustment nut can adjust the height of the middle layer bracket in the vertical direction and lock it. The top plate has through holes at its four corners and is slidably fitted onto the top of the corresponding vertical guide post through these through holes. Each vertical guide post has a locking nut threadedly connected to its top at the top of the top plate. The lower end of the locking nut presses against the upper surface of the top plate. The top plate has through holes coaxial with each hole at the position corresponding to the multi-hole array. The bottom base, the middle support and the top pressure plate are all machined with a multi-hole array, which consists of multiple through threaded holes or open holes with different diameters, for fixing screw specimens with different nominal diameters; The buffer structure is disposed between the top pressure plate and the middle support. The upper end face of the buffer structure is in contact with the lower surface of the top pressure plate, and the lower end face is in contact with the upper surface of the middle support, for absorbing vibration energy.

2. The multi-layer adjustable screw vibration testing fixture as described in claim 1, characterized in that, The buffer structure consists of spring washers fitted on the outside of the multiple vertical guide posts and a whole piece of rubber buffer layer laid on the upper surface of the middle layer support.

3. The multi-layer adjustable screw vibration testing fixture as described in claim 1, characterized in that, The vertical guide column is a hollow cylindrical steel pipe with a wear-resistant layer on its outer surface. The mounting hole is an oblong hole with its long axis arranged horizontally, used to fine-tune the relative horizontal position between the bottom base and the vibration table.

4. The multi-layer adjustable screw vibration testing fixture as described in claim 1, characterized in that, The multi-hole array includes multiple hole groups with different diameters. Each hole group is arranged in a gradual manner according to the hole diameter from small to large, and is adapted to screws of M2, M3, M4, M5 and M6 specifications respectively. Each specification has at least two holes.

5. The multi-layer adjustable screw vibration testing fixture as described in claim 1, characterized in that, A replaceable buffer pad is also sandwiched between the middle layer support and the top layer pressure plate, and the buffer pad has clearance holes corresponding to the positions of the multi-hole array.

6. The multi-layer adjustable screw vibration testing fixture as described in claim 1, characterized in that, Each of the vertical guide posts is threaded with an anti-loosening locking nut, which is located below the height adjusting nut and fits against its lower end face. It is used to lock the height adjusting nut after it is adjusted to the correct position to prevent it from vibrating and loosening.

7. The multi-layer adjustable screw vibration testing fixture as described in claim 1, characterized in that, The upper surface of the middle layer support is also machined with a V-groove or positioning pin hole for positioning the head of the screw specimen, and the V-groove or positioning pin hole is arranged alternately with some of the holes in the multi-hole array.

8. The multi-layer adjustable screw vibration testing fixture as described in claim 1, characterized in that, Each of the vertical guide pillars has a height scale marking engraved along the axial direction on its cylindrical surface. The zero position of the height scale marking corresponds to the position when the lower surface of the middle layer support contacts the upper surface of the bottom base, and is used to directly read the lifting distance of the middle layer support.

9. The multi-layer adjustable screw vibration testing fixture as described in claim 1, characterized in that, At least two limiting sleeves with different axial lengths are provided between the bottom base and the middle support. The limiting sleeves are sleeved on the vertical guide post and located below the height adjusting nut.

10. A test method using the multi-layer adjustable screw vibration test fixture according to any one of claims 1 to 9, characterized in that, include: The bottom base is fixed to the vibration table surface with bolts through the mounting holes, and then the leveling bolts are rotated to make the entire fixture level. Obtain the length parameters of the screw to be tested and the stroke parameters of the vibration table, and calculate the target height value required for the middle layer support based on the length parameters and stroke parameters; Rotate the height adjusting nut while observing the height scale markings on the vertical guide post, adjust the middle layer bracket to the target height value, and then tighten the anti-loosening locking nut to lock it in place; Multiple screw specimens with different nominal diameters were placed into the corresponding holes in the multi-hole array of the middle layer support, with the heads of the screw specimens facing upwards. The top plate is fitted onto the top of the vertical guide post, and the through hole or threaded hole on the top plate is aligned with the head of each screw specimen. Then the top plate is pressed down to compress the buffer structure to a predetermined compression amount. Tighten the locking nut to fix the top plate at the current height, thereby applying an axial preload to the screw specimen; Start the vibration table and conduct the vibration test according to the set vibration frequency, amplitude and test time; After the test, loosen the locking nut and the height adjusting nut in sequence, remove the screw test piece, check for looseness, breakage or stripping, and record the test results.

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