A vibration-damping fastener and method of designing the same

Abstract

The application discloses a damping fastener and a design method thereof. The damping fastener comprises an upper iron piece, a rubber layer and a lower iron piece, and the circumferential side walls of the three are mutually adhered inclined surfaces; the lower iron piece comprises a bottom frame and a surrounding wall extending upward from the bottom frame, the surrounding wall forms a sunken groove, the rubber layer is embedded in the sunken groove, the upper iron piece is embedded in the rubber layer, and the three form a wrapped structure of layer-by-layer embedding from outside to inside; a hollow area is arranged in the middle of the bottom frame, the bottom surface of the rubber layer is exposed from the hollow area and directly abuts against a fastener mounting surface, and the bottom surface of the rubber layer is provided with a plurality of downward protruding load-bearing bosses which directly abut against the fastener mounting surface.

Description

Technical Field

[0001] This application relates to the field of rail transit technology, specifically to a vibration damping fastener with low installation height and its design method. Background Technology

[0002] Vibration damping fasteners have become a core technology for controlling vibration and noise in my country's urban rail transit, and their application is extremely widespread. For example, they are used in sections where rail transit passes under sensitive buildings, residential areas, and cultural heritage sites, effectively reducing the impact of rail transit operations on the surrounding environment.

[0003] With the development and long-term application of vibration damping fastener technology, the types of vibration damping fastener structures in the industry are increasing. However, the installation interfaces and compatible parts of a particular vibration damping fastener are often limited. Furthermore, the installation height of vibration damping fasteners is relatively high, making them incompatible with ordinary fasteners and hindering the retrofitting and replacement of ordinary fasteners on existing lines. During long-term use, some vibration damping fasteners are prone to insufficient stability, with inadequate lateral stiffness and weak pull-out resistance being common issues.

[0004] In the design phase of vibration damping fasteners, finite element simulation is typically used to guide structural design. However, in practice, the accuracy of simulation calculations needs improvement, especially since inaccuracies in rubber hardness can easily lead to significant deviations in the calculation results. Furthermore, structural changes necessitate the reconstruction of the computational model, and blindly experimenting will increase the computational workload. Summary of the Invention

[0005] To address the shortcomings of existing technologies, one aspect of this application aims to provide a vibration damping fastener with a low installation height, and includes its design method. This aims to solve the problem that the installation height of the vibration damping fastener cannot be interchanged with that of ordinary fasteners, while improving the stability of the vibration damping fastener and guiding structural design through more accurate simulation calculations, thereby reducing the computational workload in the design phase.

[0006] According to a first aspect of this application, a low-height vibration-damping fastener is provided, comprising an upper iron component, a middle rubber layer, and a lower iron component. The upper iron component, the rubber layer, and the lower iron component are vulcanized and bonded together, and their circumferential sidewalls are mutually abutting inclined surfaces. The lower iron component includes a bottom frame and a surrounding wall extending upward from the bottom frame. The surrounding wall encloses a recessed groove, and the rubber layer is embedded in the recessed groove. The upper iron component is embedded in the rubber layer, forming a nested enveloping structure from the outside to the inside. The middle of the bottom frame has a hollow area, through which the bottom surface of the rubber layer protrudes and directly abuts against the fastener mounting surface. The bottom surface of the rubber layer has several downwardly protruding bearing bosses that directly abut against the fastener mounting surface. The lower iron piece has a rail spike mounting area at a diagonal position, and the rail spike mounting area has a rail spike mounting hole. The upper iron piece and the outer frame of the rubber layer have a clearance notch at the position corresponding to the rail spike mounting area. The rail spike bolt passes through the rail spike mounting hole and is directly locked to the foundation below the fastener mounting surface.

[0007] Utilizing the aforementioned nested subsidence structure and hollowed-out bottom frame design, the bottom of the fastener is connected to the fastener mounting surface by the outer frame of the lower iron component around its perimeter, while the central part is directly supported by the bottom surface of the rubber layer and its bearing boss. This eliminates the vertical space occupied by the closed bottom plate in the middle of the lower iron component. Simultaneously, the track spike bolts are directly locked into the track spike mounting area of ​​the lower iron component via the avoidance recess without penetrating the upper iron component and rubber layer, effectively reducing the overall installation height of the vibration damping fastener. The circumferential sidewalls of the inclined surface provide shear deformation while simultaneously forming a compressive-shear composite load-bearing path with the compressive deformation of the bearing boss. The nested vulcanized coating structure significantly increases the bonding area between the rubber layer and the iron component, thereby improving the fastener's lateral stability and pull-out resistance.

[0008] In some embodiments, the plurality of bearing bosses include contact bosses and gap bosses; the bottom surface of the contact boss directly abuts against the fastener mounting surface; the thickness of the gap boss is less than the thickness of the contact boss, such that a vertical gap is formed between the bottom surface of the gap boss and the fastener mounting surface, the vertical gap closing when the fastener bears a vertical load reaching a preset value, allowing the gap boss to participate in bearing load to provide secondary stiffness; the thickness of the gap boss is smaller than the thickness of the contact boss.

[0009] By reserving vertical gaps in some of the bosses, the contact bosses can provide a lower primary stiffness under small vertical loads to ensure good vibration reduction. Under large vertical loads, after the gaps close, all the bosses can jointly bear the load to provide higher secondary stiffness and provide safety support, thereby achieving nonlinear stiffness characteristics that take into account both vibration reduction and limit protection.

[0010] In some embodiments, the main body of the rubber layer is a closed frame ring that matches the shape of the sinking groove. A hollow area is formed in the middle of the closed frame ring that is vertically connected to the hollow area. The supporting boss protrudes downward from the bottom edge of the closed frame ring. The supporting bosses are all rectangular bosses, each rectangular boss including a first boss and a second boss. The planar dimension of the first boss is larger than that of the second boss. The first boss is arranged on both sides of the bottom surface of the rubber layer, and the second boss is arranged in a column matrix in the middle of the bottom surface of the rubber layer.

[0011] By using the inclined fit between the closed frame ring and the enclosure wall, the rubber layer can form a continuous shear bearing ring in the circumference and fully vulcanize and bond with the sinking groove of the lower iron part; by using the partitioned arrangement of the large protrusions on both sides and the small protrusion matrix in the middle, the stiffness distribution can be made more uniform while ensuring the bearing area.

[0012] In some embodiments, the rail spike mounting area consists of two lugs extending outward from a pair of diagonal positions on the bottom frame. The lugs are integrally formed with the enclosure wall, and the top surface of the lugs constitutes the mounting surface of the rail spike bolt. The rail spike mounting hole is an oblong hole extending laterally. The clearance recess is formed by the outer frame of the upper iron piece and the rubber layer bending inward at the position corresponding to the rail spike mounting area. The clearance recess exposes the rail spike mounting area and the rail spike mounting hole in the top view.

[0013] By integrating the mounting lugs of the road spikes with the enclosure, the fastener structure can be simplified and the structural strength of the road spike installation position can be guaranteed; the oblong holes provide leeway for lateral position adjustment during on-site installation.

[0014] In some embodiments, the upper part of the upper iron member is provided with a spring clip seat, which is used to install the spring clip for clamping the rail; there is a vertical height difference between the top surface of the spring clip seat and the top surface of the rail spike mounting area, so that the spring clip installed on the spring clip seat and the rail spike bolt passing through the rail spike mounting hole can be disassembled independently; this allows the disassembly operations of the spring clip and the rail spike bolt to be independent during the maintenance of the fastener, reducing the difficulty of operation and maintenance.

[0015] In some embodiments, the inclination angle of the circumferential sidewalls of the upper iron member, the rubber layer, and the lower iron member is 30° to 60°; the thickness of the upper iron member is 12mm to 18mm, the thickness of the rubber layer is 8mm to 12mm, the thickness of the lower iron member is 15mm to 20mm, and the overall installation height of the vibration damping fastener is no greater than 40mm; the Shore A hardness of the rubber material of the rubber layer is 55HA to 65HA, and the vertical static stiffness of the vibration damping fastener is 20kN / mm to 26kN / mm; the vertical height difference between the upper surface of the upper iron member and the top surface of the enclosure wall of the lower iron member is no greater than 5mm.

[0016] By selecting the above parameter range, the overall installation height can be controlled within a range interchangeable with ordinary fasteners while ensuring the structural strength and vibration reduction performance of the fastener.

[0017] In some embodiments, when the inclination angle of the circumferential sidewall is 45°, the thickness of the upper iron piece is 15mm, the thickness of the rubber layer is 10mm, the thickness of the lower iron piece is 18mm, the overall installation height of the vibration damping fastener is 37mm, the Shore A hardness of the rubber material is 60HA, the vertical static stiffness of the vibration damping fastener is 23±3kN / mm, the plane dimensions of the first boss are 55mm×30mm, the plane dimensions of the second boss are 35mm×30mm, and the thickness of the bearing boss is 12mm, good lateral stability and pull-out resistance can be obtained under the compression-shear composite bearing mode, while achieving complete interchangeability with ordinary fastener installation interfaces.

[0018] According to an embodiment of this application, a design method for the aforementioned low-installation-height vibration-damping fastener is also provided, comprising the following steps: S1, rubber material hardness verification; S2, establishment of a standard boss stiffness library; S3, rubber layer main body stiffness simulation; S4, load-bearing boss configuration and overall stiffness estimation; S5, overall finite element verification. Through this method, the simulated hardness of the rubber material can be verified first in the vibration-damping fastener structural design to eliminate systematic deviations caused by the selection of MR parameters. Then, a stiffness lookup table for bosses of different sizes can be pre-established, and the rubber layer main body and bosses can be decomposed into parallel spring models for rapid stiffness estimation. This reduces the computational workload caused by repeated reconstruction of the overall finite element model and blind trial and error, while improving the accuracy of simulation prediction.

[0019] In some embodiments, in step S1, for regular rubber blocks with the same planar dimensions and thickness as the bearing boss, static stiffness simulations based on the MR material constitutive model are performed using various nominal hardnesses. Using the static stiffness test data of regular rubber blocks with the same dimensions and nominal hardness as a benchmark, the simulation input hardness corresponding to the consistency between the simulation results and the test results is used as the mapping value of the nominal hardness. Through hardness verification based on test data, simulation deviations caused by directly using nominal hardness to calculate MR parameters can be effectively eliminated, improving the accuracy of subsequent stiffness predictions. In step S3, the tilt angle of the inclined surface is adjusted so that the reference static stiffness of the main body is within the range of 50% to 70% of the target vertical static stiffness.

[0020] In some embodiments, in step S4, a first boss with a relatively large planar dimension is arranged on both sides of the bottom surface of the rubber layer, and a second boss with a relatively small planar dimension is arranged in a matrix in the middle region between the first bosses on both sides. The static stiffness of each boss is selected from the standard boss size-static stiffness lookup table and then calculated in parallel.

[0021] This application has one or a combination of the following beneficial effects: 1. The vibration damping fastener has a recessed structure, with a small height difference between the upper surface of the upper iron part and the upper surface of the lower iron part. Therefore, the installation height of the vibration damping fastener can be reduced, and it can be interchanged with ordinary fasteners, which is convenient for the renovation and upgrading of existing lines.

[0022] 2. The rubber layer structure of the vibration damping fastener has sloping edges on all four sides, allowing for shear deformation. The bottom boss of the rubber layer allows for compression deformation. The combination of these two deformation methods achieves good vibration damping under small deformations and provides good safety support under large deformations. The upper iron part, rubber layer, and lower iron part all have sloping edges on all four sides, effectively increasing the vulcanization bonding surface and improving pull-out resistance.

[0023] 3. The outer frame of the upper iron component has an angle at the bolt mounting position, allowing the bolts to be directly installed on the mounting surface of the lower iron component's bolt mounting area. This reduces the bolt length and ensures consistency with the bolt type of ordinary fasteners. Simultaneously, the height difference between the upper iron component's spring clip seat and the bolt increases the distance between the spring clip and the bolt, enabling separate disassembly of the spring clip and bolt without interference.

[0024] 4. The wrapping structure design at both ends of the vibration damping fastener, as well as the vulcanization bonding process, can significantly increase the lateral stability of the vibration damping fastener.

[0025] 5. By adjusting the number, size, and spacing of the bosses at the bottom of the rubber layer, the static stiffness of the fastener can be adjusted; by adjusting the gap between the bosses and the fastener mounting surface, a secondary stiffness effect can be achieved.

[0026] 6. During the design process, verifying the rubber hardness parameters increased the accuracy of finite element simulation calculations. By estimating the static stiffness of the main rubber layer and the boss portion in the early stages, the boss arrangement scheme can be designed more accurately, reducing the workload of finite element simulation calculations. Attached Figure Description

[0027] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a front view of a low-height vibration damping fastener according to an embodiment of this application; Figure 2This is a diagram showing the arrangement of the bottom bosses of a low-installation-height vibration-damping fastener according to an embodiment of this application; Figure 3 This is a perspective structural diagram of the lower iron part of a low-installation-height vibration-damping fastener according to an embodiment of this application; Figure 4 This is a perspective structural view of the rubber body portion of a low-installation-height vibration-damping fastener according to an embodiment of this application; Figure 5 This is a flowchart illustrating a design method for a low-installation-height vibration-damping fastener according to an embodiment of this application.

[0028] Figure label: 1. Upper iron parts 2. Rubber layer 3. Lower iron parts 4 Fastener mounting surface 5. Rails 11 Avoiding the notch 12 spring clip mount 21 Supporting boss 31. Bottom frame 32 walls 33. Submerged trough 35-screw installation area 36 spike mounting holes Detailed Implementation

[0029] The present application will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present application. However, the present application can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present application. Therefore, the scope of protection of the present application should not be limited by the content of this specific embodiment.

[0030] Furthermore, this application uses specific terms to describe embodiments of the application, such as "an embodiment," "one embodiment," and / or "some embodiments," which refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment" or "one embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0031] It is worth noting that although the embodiments described in this application use marine diesel engine test benches as an application scenario to introduce the specific structure of power unit test benches, the multi-layer vibration isolation suspension test bench structure based on this application can also be applied to other rotating machinery or other power equipment testing fields with high requirements for vibration isolation, as long as it is necessary to simulate the top-suspended multi-layer vibration isolation installation condition in the testing of these equipment, reproduce the vibration transmission path of the suspension installation on land, and accurately test the vibration isolation effect.

[0032] It is worth noting that although the vibration damping fasteners and design methods described in this application are for the application scenario of upgrading and transforming ordinary fasteners in urban rail transit subway lines, the vibration damping fasteners and design methods based on this application can also be applied to track fastener systems in other rail transit fields, such as vibration damping fasteners in suburban railways, intercity railways, tram lines, etc., as long as these fastener systems require a reduction in installation height to achieve interchangeability with ordinary fasteners, or require improved stability through compression-shear composite bearing, or require improved simulation design efficiency through hardness verification and parallel spring models.

[0033] The following detailed description of an embodiment of this application, with reference to specific examples, will help those skilled in the art to further understand an embodiment of this application, but does not limit the embodiment of this application in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of an embodiment of this application. These all fall within the protection scope of an embodiment of this application.

[0034] In this application, the term "upper iron component" refers to a metal load-bearing component arranged on the upper part of the vibration damping fastener for supporting the rail and the elastic clip. Its material can be ductile iron, cast steel or other metal materials with sufficient strength, and its form is not limited. For example, it can be plate-shaped, frame-shaped or irregular structure with rail support groove and elastic clip seat.

[0035] In this application, the term "lower iron component" refers to a metal load-bearing component arranged at the bottom of the vibration damping fastener to transfer the load of the upper iron component and rubber layer to the fastener mounting surface. Its material can also be ductile iron, cast steel, or other metal materials. The lower iron component includes a bottom frame extending circumferentially and a surrounding wall extending upward from the bottom frame, but this is not limiting. The bottom frame can also be provided with reinforcing structures such as horizontal ribs and longitudinal ribs as needed.

[0036] In this application, the term "rubber layer" refers to an elastomeric component that is vulcanized and bonded between the upper and lower iron parts, and its material is mainly rubber, but other polymeric elastic materials with similar elastic properties are not excluded.

[0037] In this application, the term "vulcanized bonding" refers to a bonding method in which a rubber layer and a metal part are formed through a vulcanization process. However, this is not limiting, and other processes that can achieve a strong bond between metal and elastomer can also be used.

[0038] In this application, the term "load-bearing boss" refers to a protruding structure that extends downward from the bottom surface of the rubber layer and directly abuts against the fastener mounting surface. Its shape, quantity, and size can be designed according to stiffness requirements.

[0039] In this application, the term "vertical" refers to the direction perpendicular to the fastener mounting surface, i.e., the direction of rail load transmission; the term "circumferential" refers to the circumferential direction around the center of the fastener; the term "longitudinal" refers to the direction extending along the rail; and the term "lateral" refers to the horizontal direction perpendicular to the extension of the rail.

[0040] In this application, the term "MR constitutive model" refers to the Mooney-Rivlin rubber constitutive model, which is a commonly used hyperelastic constitutive model in finite element simulation of rubber materials.

[0041] In this application, the term "tilt angle" refers to the angle between the circumferential sidewalls of the upper iron piece, the rubber layer, and the lower iron piece and the vertical direction.

[0042] like Figures 1 to 4 As shown, in some embodiments, the vibration damping fastener includes an upper iron piece 1, a rubber layer 2, and a lower iron piece 3, which are bonded together by vulcanization, forming a nested enveloping structure from the outside in. The bottom of the fastener has the lower iron piece's outer frame contacting the fastener mounting surface 4 around its perimeter, while the bottom surface of the rubber layer 2 and its supporting boss 21 directly contact the fastener mounting surface 4 in the center. The lower iron piece 3 is a recessed frame structure. The bottom frame 31 includes an outer frame extending circumferentially and horizontal ribs connecting the outer frame. Multiple rectangular hollow areas are formed between the horizontal ribs. The bottom surface of the rubber layer 2 protrudes from the hollow areas and directly abuts against the fastener mounting surface 4; the supporting boss 21 protrudes downward from the hollow areas and directly abuts against the fastener mounting surface 4. The upper iron piece 1 has rail bearing / shoulder structures on both sides of its upper part to laterally limit the rail 5. The upper iron piece 1 also has a spring clip seat 12 for installing the spring clip that clamps the rail. The lower iron piece 3 extends outward at a pair of diagonal positions to form a rail spike mounting area (lug) 35. The upper iron piece 1 and the rubber layer 2 form clearance recesses 11 at corresponding positions. The rail spike bolt passes through the rail spike mounting hole 36 and directly locks the fastener into the foundation below the fastener mounting surface. The rail is placed on the rail bearing surface of the upper iron piece 1.

[0043] Figure 2The bottom view of the vibration damping fastener shows that there are 13 bearing bosses 21 on the bottom surface of the rubber layer, including 4 first bosses (2 on each side / end, 55mm×30mm in planar size, vertical rectangle, with the long side along the longitudinal direction) located in the upper left and lower right areas of the rectangular fastener frame, and 9 second bosses (35mm×30mm in planar size) arranged in a 3x3 matrix in the middle. All bosses are 12mm thick. The spike mounting holes 36 are waist-shaped holes extending laterally, located at the lower left and upper right corners respectively. The outer frame of the rubber layer bends inward at the position corresponding to the spike mounting area to form an S-shaped clearance notch 11, which fully exposes the spike mounting area and spike mounting holes in the top view.

[0044] Figure 3 The three-dimensional structure of the lower iron component 3 is shown. The lower iron component includes a bottom frame and a surrounding wall. The surrounding wall extends upward from the bottom frame to form a fastener side slope and encloses a recessed groove. Two rail spike mounting lugs 35 (i.e. rail spike mounting areas) extend outward from a pair of diagonal positions of the bottom frame. The lugs are integrally formed with the surrounding wall. The top surface of the lugs has a waist-shaped rail spike mounting hole 36. The top surface of the lugs constitutes the mounting surface of the rail spike bolt.

[0045] Figure 4 The three-dimensional structure of the rubber body is shown. The main body of the rubber layer 2 is a closed frame ring that matches the shape of the sinkhole. The outer frame has a bend at the diagonal position to avoid the bend, so as to expose the rail spike mounting lug of the lower iron part.

[0046] Figure 5 The flowchart shows the design method of vibration damping fasteners, which includes six steps performed in sequence: checking the hardness of rubber materials → simulating the static stiffness of standard rubber blocks → simulating the main body of the fastener rubber layer → configuring the static stiffness of the fastener rubber boss and obtaining the overall static stiffness of the fastener → setting the secondary stiffness of the fastener rubber boss (if necessary) → checking the static stiffness of the fastener.

[0047] The vibration damping fastener first includes a lower iron member 3, which serves as the lower load-bearing foundation. The lower iron member 3 includes a bottom frame 31 and a surrounding wall 32. The bottom frame 31 extends circumferentially to form an outer frame, and the surrounding wall 32 extends upward from the bottom frame 31, enclosing a recessed groove 33 to accommodate the rubber layer 2 and the upper iron member 1. The bottom frame 31 includes a circumferentially extending outer frame and horizontal ribs connecting the outer frame to maintain structural rigidity. A through-hole area is formed in the middle of the bottom frame 31 between the horizontal ribs, allowing the bottom surface of the rubber layer embedded in the recessed groove to be directly exposed and abut against the fastener mounting surface 4. The bottom of the fastener is contacted around the bottom perimeter by the bottom frame's outer frame, and the bottom of the fastener is contacted at the center by the bottom surface of the rubber layer and its load-bearing protrusions. The bottom frame's outer frame is preferably arranged around the bottom perimeter, but this is not limiting; the specific arrangement of the bottom frame's outer frame and the horizontal ribs can be designed according to structural strength requirements.

[0048] Two road spike mounting lugs 35 (i.e., road spike mounting areas) extend outward from a pair of diagonal positions on the base frame 31. These lugs are integrally formed with the enclosure wall 32, and the top surface of the lugs is approximately flush with the top surface of the enclosure wall, forming the mounting surface for the road spike bolts. Each lug has a laterally extending, oblong road spike mounting hole 36 for the road spike bolt to pass through. The long axis of the oblong hole extends laterally, providing lateral adjustment allowance during on-site installation. It is understood that the shape of the road spike mounting hole is not limited to oblong; this application does not exclude the use of circular holes or other shapes.

[0049] In a preferred embodiment, the thickness of the lower iron member 3 (i.e., the vertical height from the bottom surface of the base frame to the top surface of the enclosure) is 15 mm to 20 mm, preferably 18 mm; the inclination angle of the enclosure (i.e., the angle between the inner side of the enclosure and the vertical) is 30° to 60°, preferably 45°. The material of the lower iron member is preferably ductile iron, formed by casting, but this is not limiting.

[0050] Rubber layer 2 is arranged within the sinkhole 33 of the lower iron component 3 and is bonded to the lower iron component 3 and the upper iron component 1 together through a vulcanization process. The main body of rubber layer 2 is a closed frame-shaped ring (such as a ring matching the shape of the sinkhole 33) Figure 4 The closed frame ring shown forms a hollow area in the middle that runs vertically through the hollow area of ​​the bottom frame, so as to avoid obscuring the hollow area.

[0051] The circumferential sidewall of rubber layer 2 fits and matches the sidewalls of the lower iron component 32 and the upper iron component 1, forming a continuous inclined mating surface. This inclined mating surface mainly undergoes shear deformation when the fastener bears vertical loads, constituting a shear bearing part. During the vulcanization process, this inclined mating surface also provides a large vulcanization bonding area, which is beneficial to improving the bonding strength and pull-out resistance between the rubber and the metal component.

[0052] The bottom surface of rubber layer 2 protrudes from the hollowed-out area of ​​the lower iron frame 31 and directly abuts against the fastener mounting surface 4. The bottom surface of rubber layer 2 (i.e., the bottom edge of the closed frame ring) protrudes downward to form several load-bearing bosses 21. The load-bearing bosses 21 directly abut against the fastener mounting surface 4 and undergo compressive deformation under vertical load, forming a compression load-bearing part. The shear load-bearing part and the compression load-bearing part together constitute the vertical load-bearing path of the vibration damping fastener, forming a combined compression and shear load-bearing mode. The bottom frame around the bottom of the fastener, together with the rubber bottom surface and the load-bearing bosses in the middle, form a zoned load-bearing structure of "stable contact with the bottom by the metal outer frame + elastic load-bearing in the middle of the rubber".

[0053] In a preferred embodiment, the bearing bosses 21 are all rectangular bosses, including a first boss 211 with a relatively large planar dimension and a second boss 212 with a relatively small planar dimension. There are four first bosses, arranged on both sides of the bottom surface of the rubber layer, two on each side (located in the upper left and lower right areas of the rectangular fastener frame, respectively), with a planar dimension of 55mm × 30mm; there are nine second bosses, arranged in a 3x3 matrix in the middle area of ​​the bottom surface of the rubber layer, with a planar dimension of 35mm × 30mm; a total of 13 bearing bosses 21, each with a thickness of 12mm. It can be understood that the number, size, and arrangement of the bosses are not limited to the specific values ​​mentioned above, and can be adjusted according to the target stiffness requirements.

[0054] In embodiments requiring secondary stiffness, some of the load-bearing bosses serve as gap bosses, with a thickness less than that of the other contact bosses. For example, two first bosses near the inner side of the fastener and three second bosses in the middle are selected as gap bosses, reducing their thickness from 12mm to 9mm, creating a 3mm vertical gap between their bottom surface and the fastener mounting surface. The vertical gap is preferably between 2mm and 4mm, corresponding to a thickness difference of 2mm to 4mm between the gap bosses and the contact bosses.

[0055] The Shore A hardness of the rubber material in rubber layer 2 is preferably 55HA to 65HA, particularly 60HA. The thickness of the rubber layer (i.e., the vertical thickness at the inclined sidewall) is 8mm to 12mm, preferably 10mm.

[0056] The outer frame of the rubber layer 2 forms an inwardly angled relief notch 11 at the position of the corresponding lower iron rail spike mounting lug 35. This relief notch exposes the rail spike mounting lug 35 and rail spike mounting hole 36 in the top view, preventing the rubber layer from covering the rail spike mounting area and affecting the installation of the rail spike bolt.

[0057] The upper iron component 1 is embedded inside the rubber layer 2, and its outer wall fits and matches the inner side of the rubber layer, and is also an inclined surface, so that the nested inclined surfaces of the three components are continuously matched. As a component that directly supports the rail, the upper iron component 1 has rail support / shoulder structures on both sides of its upper surface to limit the lateral movement of the rail. The upper iron component 1 is also provided with a spring clip seat 12 for installing the spring clip that clamps the rail.

[0058] The outer frame of the upper iron piece 1 also has a clearance notch at the position corresponding to the rail spike mounting lug 35 of the lower iron piece (consistent with the clearance notch position of the rubber layer) to avoid obstructing the rail spike mounting lug. There is a vertical height difference between the top surface of the spring clip seat 12 and the top surface of the rail spike mounting lug 35, so that the installation position of the spring clip and the installation position of the rail spike bolt are vertically staggered, so that the spring clip and the rail spike bolt can be disassembled independently without interfering with each other during maintenance.

[0059] In a preferred embodiment, the thickness of the upper iron member 1 is 12mm to 18mm, preferably 15mm; the vertical height difference between the upper surface of the upper iron member and the top surface of the lower iron member enclosure 32 is no more than 5mm, so that the overall installation height of the vibration damping fastener can be reduced to a range that matches that of ordinary fasteners. Under the preferred parameter combination, the overall installation height of the vibration damping fastener (the vertical distance from the fastener mounting surface to the highest point of the fastener) is 37mm, not more than 40mm, which allows for interchangeability of the installation interface with ordinary fasteners. The upper iron member is preferably made of ductile iron and is formed by casting.

[0060] like Figure 1 As shown, in the assembled state, the rail is placed on the rail bearing surface of the upper iron piece 1, and the elastic clip is installed on the elastic clip seat 12 to fasten the rail; the lower iron piece 3 contacts the fastener mounting surface 4 through the outer frame of the bottom frame, and the bottom surface of the rubber layer 2 and its bearing boss 21 directly abut against the fastener mounting surface 4 from the hollow area of ​​the bottom frame; the rail spike bolt passes through the rail spike mounting hole 36 from the clearance notch and is directly locked to the foundation below the fastener mounting surface (such as the embedded sleeve in the sleeper or track slab).

[0061] The inventors have creatively discovered that a key reason why existing vibration damping fasteners have a high installation height and are difficult to interchange with ordinary fasteners is that the lower iron component uses a closed, single-plate structure. The bottom surface of the rubber layer is covered by a closed base plate, and the force must be indirectly transmitted to the mounting surface through the lower iron component's base plate. This increases the thickness of the base plate and the vertical space required for the spike to penetrate the upper iron component / rubber layer. In this embodiment, the lower frame is hollowed out, allowing the bottom surface of the rubber layer to directly contact the ground and bear the load, eliminating the vertical space occupied by the closed base plate in the middle of the lower iron component. At the same time, the avoidance recess design between the upper iron component and the outer frame of the rubber layer allows the spike bolt to be directly locked to the spike mounting lug of the lower iron component without penetrating the upper iron component and the rubber layer, thereby reducing the required length of the spike and the reserved height for the spike penetration path. The synergistic effect of these two structural aspects allows the overall installation height of the vibration damping fastener to be reduced to the 37mm level, making it interchangeable with ordinary fasteners and facilitating the retrofitting and upgrading of ordinary fasteners on existing lines.

[0062] On the other hand, all three circumferential sidewalls are mutually fitted inclined surfaces. Under vertical loads, the inclined rubber sidewalls undergo shear deformation, while the bottom bearing bosses undergo compressive deformation. The two deformation modes combine: during small deformations, shear deformation provides lower stiffness to ensure good vibration isolation; during large deformations, the shear stiffness of the rubber sidewalls increases, while the compression of the bosses provides higher support stiffness, forming a nonlinear load-bearing characteristic of compression and shear, balancing vibration reduction and safety support. The nested vulcanized wrapping structure also effectively increases the bonding area between the rubber and metal parts, improving pull-out resistance and lateral stability.

[0063] In addition, since the rail spike bolts are directly installed on the rail spike mounting lugs of the lower iron parts, the length of the rail spike bolts can be shortened, making them consistent with the rail spike bolt models of ordinary fasteners; at the same time, the vertical height difference between the elastic clip seat and the rail spike mounting lugs increases the distance between the elastic clip and the rail spike bolts, so that the elastic clip and the rail spike bolts do not interfere with each other during disassembly and maintenance.

[0064] Figure 5 The flowchart shows the design method of vibration damping fasteners, which includes six steps performed in sequence: checking the hardness of rubber materials → simulating the static stiffness of standard rubber blocks → simulating the main body of the fastener rubber layer → configuring the static stiffness of the fastener rubber boss and obtaining the overall static stiffness of the fastener → setting the secondary stiffness of the fastener rubber boss (if necessary) → checking the static stiffness of the fastener.

[0065] The inventors noted that after the structure of the vibration damping fastener is determined, its vertical static stiffness is mainly determined by the shear stiffness of the rubber layer sidewall and the compressive stiffness of the bottom bearing boss. The deformation of these two parts is relatively independent and can be approximated as a parallel spring system.

[0066] According to the principle of parallel spring stiffness, when multiple springs are connected in parallel, the total stiffness of the system is equal to the sum of the stiffnesses of each individual spring:

[0067] Wherein, Kbody represents the equivalent shear stiffness of the main body of the rubber layer (i.e., the closed frame-shaped ring without bosses and its inclined sidewalls) under vertical load. Let m be the equivalent stiffness of the j-th bearing boss under vertical compression, and m be the total number of bearing bosses.

[0068] For a fastener with secondary stiffness, the number of contact bosses is m1, the number of clearance bosses is m2 (m1+m2=m), and the clearance is δ. During the small load stage (vertical displacement less than δ), the clearance bosses do not participate in load bearing; at this time, the primary stiffness is:

[0069] When the vertical displacement reaches δ, the bottom surface of the clearance boss contacts the fastener mounting surface and begins to bear load, at which point it enters the secondary stiffness stage:

[0070] Since each boss is a rectangular rubber block of regular size, its compressive stiffness is... A standard boss size-static stiffness lookup table (see Table 2 below) can be established by performing finite element simulations on regular rubber blocks of different sizes and thicknesses beforehand. During design, the corresponding stiffness values ​​can be directly obtained from the table and combined, without the need to rebuild the overall finite element model for each boss arrangement scheme. The shear stiffness Kbody of the main body of the rubber layer is mainly provided by the inclined sidewalls. For the main body shape under the same inclination angle, only one finite element simulation is needed to obtain the reference value.

[0071] Furthermore, the inventors discovered that the tilt angle has a significant impact on the Kbody: the larger the tilt angle (the steeper the sidewall), the smaller the shear deformation component, the larger the compression component, and the higher the main body stiffness; the smaller the tilt angle, the larger the shear deformation component, and the lower the main body stiffness. By reasonably selecting the tilt angle (preferably making the Kbody within the range of 50% to 70% of the target total stiffness), a reasonable adjustment margin can be left for the stiffness configuration of the boss.

[0072] As can be seen from the above parallel model, one embodiment of this application can quickly estimate the overall static stiffness and guide the design of the boss arrangement scheme without relying on repeated iterations of the overall finite element method by "basicizing the shear stiffness of the main body + looking up the table of the compressive stiffness of the boss + combining the two in parallel", thereby significantly reducing the amount of calculation work in the design stage.

[0073] refer to Figure 5 As shown, the design method for the above-mentioned low-installation-height vibration-damping fasteners may include the following steps: Checking the hardness of rubber materials In the design process, static stiffness tests and simulations were first conducted on regular rubber blocks to verify the rubber hardness parameters. Regular rubber block samples with dimensions of 55mm×30mm×12mm and 35mm×30mm×12mm were prepared, with a nominal hardness of 60HA. Simulation input hardnesses of 40HA, 45HA, 50HA, 55HA, 60HA, and 65HA were used for the regular rubber blocks of the above dimensions. The Mooney-Rivlin constitutive model parameters C10 and C01 were calculated from the hardness, and the static stiffness simulation results were compared with those of regular rubber blocks of the same size and with a nominal hardness of 60HA. The experimental results show that the static stiffness of the 55mm×30mm×12mm rubber block is 0.94 kN / mm, and the static stiffness of the 35mm×30mm×12mm rubber block is 0.60 kN / mm.

[0074] Table 1 Comparison of simulation and experimental results of static stiffness of regular rubber blocks (unit: kN / mm)

[0075] Comparing the simulation results with experimental data reveals that when the simulation input hardness is 40HA (corresponding to MR parameters C10=0.2261, C01=0.0565), the simulated stiffness of the 35mm boss (0.61kN / mm) matches well with the experimental value of 0.60kN / mm, and the simulated stiffness of the 55mm boss (0.92kN / mm) matches well with the experimental value of 0.94kN / mm. Therefore, for rubber materials with a nominal hardness of 60HA, 40HA should be used as the input hardness in the simulation calculation. This verification relationship provides an accurate material parameter basis for the subsequent establishment of a standard boss stiffness library and overall stiffness simulation.

[0076] Simulation of the main body of the fastener rubber layer

[0077] Using the verified MR parameters corresponding to 40HA, static stiffness simulation calculations were performed on regular rubber boss models with different planar dimensions and different thicknesses (12mm and 9mm). A standard boss size-static stiffness lookup table was obtained, and the results are listed in Table 2.

[0078] Table 2. Simulation results of static stiffness of regular rubber blocks of different sizes (unit: kN / mm)

[0079] The aforementioned stiffness library covers boss thicknesses ranging from 10mm to 14mm (including two typical thicknesses of 9mm and 12mm) and planar dimensions ranging from 30mm to 60mm to 25mm to 35mm, which can meet the needs of conventional boss selection.

[0080] The static stiffness configuration of the rubber boss portion of the fastener is determined, and the overall static stiffness of the fastener is obtained.

[0081] Using the verified MR parameters, a finite element model was established for the main body of the rubber layer without protrusions (i.e., a closed frame ring + 45° inclined sidewalls) to simulate the vertical static stiffness. The baseline stiffness of the main body, Kbody, was found to be 14.12 kN / mm, approximately 61% of the target total stiffness of 23 kN / mm, falling within the preferred range of 50% to 70%. Based on this, four 55mm×30mm×12mm first protrusions and nine 35mm×30mm×12mm second protrusions were selected. From Table 2, the stiffnesses of a single protrusion were found to be 0.92 kN / mm and 0.61 kN / mm, respectively, and combined into: The stiffness of the combined boss, Kboss, is calculated as follows: Kboss = 4 × 0.92 + 9 × 0.61 = 3.68 + 5.49 = 9.17 kN / mm² The estimated overall stiffness of the fastener, Ktotal, is 14.12 + 9.17 = 23.29 kN / mm². The estimated value is close to the target stiffness of 23±3kN / mm, which meets the design requirements.

[0082] Overall finite element verification

[0083] Based on the above boss arrangement scheme, an overall finite element model including the upper iron component, rubber layer, and lower iron component was established. Vertical static stiffness was simulated and verified using the verified MR parameters (40HA corresponds to C10=0.2261, C01=0.0565). The overall static stiffness was found to be 23.70 kN / mm, with a deviation of approximately 3.0% from the target stiffness of 23 kN / mm, which is within the allowable deviation range of ±15%, meeting the target requirements. Compared with the estimated value of 23.29 kN / mm from the parallel model, the deviation is approximately 1.8%, verifying the accuracy of the parallel spring estimation method.

[0084] Secondary stiffness setting for the rubber boss portion of the fastener (if required)

[0085] Based on the above single-stage stiffness scheme, two 55mm×30mm first bosses near the inner side of the fastener and three 35mm×30mm second bosses in the middle are selected as gap bosses, and their thickness is changed from 12mm to 9mm, so that a 3mm vertical gap is formed between their bottom surface and the fastener mounting surface.

[0086] At this point, the gapless bosses (i.e., contact bosses) consist of two 55×30 bosses and six 35×30 bosses, calculated according to the parallel model: The first-order stiffness of the boss, Kboss,1, is calculated as follows: Kboss,1 = 2 × 0.92 + 6 × 0.61 = 1.84 + 3.66 = 5.50 kN / mm² The primary stiffness of the fastener is K1 = 14.12 + 5.50 = 19.62 kN / mm². By paralleling the stiffness of all bosses, the secondary stiffness of the bosses is obtained as Kboss,2Kboss,2=14.25kN / mm, and the secondary stiffness of the fastener is K2K2=14.12+14.25=33.87kN / mm.

[0087] Static stiffness check of fasteners

[0088] A finite element model was established based on the above-mentioned secondary stiffness scheme. The secondary stiffness of the fastener was found to be 34.24 kN / mm through finite element simulation, which is within the target range of 30 kN / mm to 36 kN / mm. The deviation from the estimated value of 33.87 kN / mm by the parallel model is about 1.1%, which is a good match. This further verifies the accuracy of the parallel spring estimation method in the prediction of secondary stiffness.

[0089] Although various embodiments of this application are described in the accompanying drawings with reference to examples of low-installation-height vibration-damping fasteners applied to the renovation of urban rail transit subway lines, it should be understood that the embodiments within the scope of this application can be applied to other track vibration-damping fastener systems or design methods with similar structures and / or functions, such as vibration-damping fastener designs in the rail transit fields of urban rail transit, intercity rail, trams, etc., as long as there is a need to reduce the installation height, improve stability, or increase simulation design efficiency.

[0090] While this application discloses preferred embodiments as described above, it is not intended to limit the scope of this application. Any changes and modifications can be made by those skilled in the art without departing from the spirit and scope of this application. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the content of the technical solution of this application shall fall within the protection scope defined by the claims of this application.

Claims

1. A vibration damping fastener with low installation height, characterized in that, It includes an upper iron part (1), an intermediate rubber layer (2) and a lower iron part (3). The upper iron part (1), the rubber layer (2) and the lower iron part (3) are vulcanized and bonded together. The circumferential sidewalls of the three are inclined surfaces that fit together. The lower iron piece (3) includes a bottom frame (31) and a surrounding wall (32) extending upward from the bottom frame (31). The surrounding wall (32) encloses and forms a recessed groove (33). The rubber layer (2) is embedded in the recessed groove (33). The upper iron piece (1) is embedded in the rubber layer (2). The three form a nested wrapping structure from the outside to the inside. The bottom frame (31) has a hollow area in the middle. The bottom surface of the rubber layer (2) is exposed from the hollow area and directly abuts against the fastener mounting surface (4). The bottom surface of the rubber layer (2) has several downward protruding bearing bosses (21) that directly abut against the fastener mounting surface (4). The lower iron piece (3) is provided with a rail spike mounting area (35), and the rail spike mounting area (35) is provided with a rail spike mounting hole (36), so that the rail spike bolt passes through the rail spike mounting hole (36) and is directly locked to the foundation below the fastener mounting surface (4).

2. The vibration damping fastener with low installation height according to claim 1, characterized in that, The plurality of bearing bosses (21) include contact bosses and gap bosses; the bottom surface of the contact boss directly abuts against the fastener mounting surface (4); the thickness of the gap boss is less than the thickness of the contact boss, so that a vertical gap is formed between the bottom surface of the gap boss and the fastener mounting surface (4), and the vertical gap closes when the fastener bears a vertical load that reaches a preset value, so that the gap boss participates in bearing the load to provide secondary stiffness; the thickness of the gap boss is smaller than the thickness of the contact boss.

3. The vibration damping fastener with low installation height according to claim 1, characterized in that, The main body of the rubber layer (2) is a closed frame ring that matches the shape of the sinking groove (33). The middle part of the closed frame ring forms a hollow area that is vertically connected to the hollow area. The bearing boss (21) protrudes downward from the bottom edge of the closed frame ring. The bearing boss (21) is a rectangular boss. The rectangular boss includes a first boss and a second boss. The planar dimension of the first boss is larger than that of the second boss. The first boss is arranged on both sides of the bottom surface of the rubber layer (2), and the second boss matrix is ​​arranged in the middle of the bottom surface of the rubber layer (2).

4. The vibration damping fastener with low installation height according to claim 1, characterized in that, The rail spike mounting area (35) consists of two lugs extending outward from a pair of diagonal positions of the bottom frame (31). The lugs are integrally formed with the enclosure wall (32), and the top surface of the lugs constitutes the mounting surface of the rail spike bolt. The rail spike mounting hole (36) is a waist-shaped hole extending laterally. The clearance recess (11) is formed by the outer frame of the upper iron piece (1) and the rubber layer (2) bending inward at the position corresponding to the rail spike mounting area (35). The clearance recess (11) exposes the rail spike mounting area (35) and the rail spike mounting hole (36) in the top view direction.

5. The low-installation-height vibration-damping fastener according to claim 4, characterized in that, The upper part of the upper iron piece (1) is provided with a spring clip seat (12), which is used to install the spring clip for clamping the rail; there is a vertical height difference between the top surface of the spring clip seat (12) and the top surface of the rail spike mounting area (35), so that the spring clip installed on the spring clip seat (12) and the rail spike bolt passing through the rail spike mounting hole (36) can be disassembled independently.

6. The vibration damping fastener with low installation height according to claim 1, characterized in that, The inclination angle of the circumferential sidewalls of the upper iron part (1), the rubber layer (2), and the lower iron part (3) is 30° to 60°; the thickness of the upper iron part (1) is 12mm to 18mm, the thickness of the rubber layer (2) is 8mm to 12mm, the thickness of the lower iron part (3) is 15mm to 20mm, and the overall installation height of the vibration damping fastener is not greater than 40mm; the Shore A hardness of the rubber material of the rubber layer (2) is 55HA to 65HA, and the vertical static stiffness of the vibration damping fastener is 20kN / mm to 26kN / mm; the vertical height difference between the upper surface of the upper iron part (1) and the top surface of the enclosure wall (32) of the lower iron part (3) is not greater than 5mm.

7. The low-installation-height vibration-damping fastener according to claim 6, characterized in that, The inclination angle of the circumferential sidewall is 45°; the thickness of the upper iron part (1) is 15mm, the thickness of the rubber layer (2) is 10mm, the thickness of the lower iron part (3) is 18mm, the overall installation height of the vibration damping fastener is 37mm, so as to be interchangeable with ordinary fasteners; the Shore A hardness of the rubber material of the rubber layer (2) is 60HA, the vertical static stiffness of the vibration damping fastener is 23±3kN / mm; the planar dimensions of the first boss are 55mm×30mm, the planar dimensions of the second boss are 35mm×30mm, and the thickness of the bearing boss (21) is 12mm.

8. A design method for a low-installation-height vibration-damping fastener as described in claim 1, characterized in that, Includes the following steps: S1. Rubber material hardness verification: Prepare regular rubber block samples with various predetermined hardnesses, and conduct vertical static stiffness tests and static stiffness simulation calculations based on the MR material constitutive model on the regular rubber block samples respectively. Compare the simulation results with the test results under the same size and the same nominal hardness to establish the mapping relationship between the nominal hardness of the rubber material used in the rubber layer (2) and the input hardness of the simulation calculation. S2. Establishment of Standard Boss Stiffness Library: Using the MR parameters corresponding to the simulation input hardness verified by S1, static stiffness simulation calculations are performed on regular rubber boss models with different planar dimensions and thicknesses to form a standard boss size-static stiffness lookup table. S3, Rubber layer main body stiffness simulation: Decompose the rubber layer (2) of the vibration damping fastener into the main body part without the bearing boss (21) and the bearing boss (21) part, establish a finite element model for the main body part and perform vertical static stiffness simulation calculation to obtain the main body reference static stiffness, which is provided by the shear deformation of the circumferential inclined surface of the rubber layer (2); S4. Configuration of bearing bosses and estimation of overall stiffness: Each bearing boss in the bearing boss section is regarded as an independent compression spring connected in parallel with the main body. According to the size and thickness of the bearing boss to be designed, the corresponding single boss static stiffness is selected from the standard boss size-static stiffness lookup table. The single boss static stiffness of all bearing bosses is summed in parallel to obtain the combined static stiffness of the bosses. Then, the main body reference static stiffness and the combined static stiffness of the bosses are summed in parallel to obtain the overall estimated static stiffness of the vibration damping fastener. The number, size and arrangement of the bearing bosses (21) are adjusted according to the deviation between the overall estimated static stiffness of the vibration damping fastener and the target static stiffness. S5. Overall Finite Element Verification: Based on the load-bearing boss arrangement scheme determined in S4, establish the overall finite element model of the vibration damping fastener and perform vertical static stiffness simulation verification. If the deviation between the verification result and the target static stiffness exceeds the allowable range, return to S4 to adjust the load-bearing boss arrangement until the verification result meets the target static stiffness requirements.

9. The design method according to claim 8, characterized in that, In S1, for regular rubber blocks with the same planar dimensions and thickness as the bearing boss (21), static stiffness simulation based on the MR material constitutive model is performed using various nominal hardnesses. The static stiffness test data of regular rubber blocks with the same dimensions and nominal hardness are used as a benchmark, and the simulation input hardness corresponding to the consistency between the simulation results and the test results is used as the mapping value of the nominal hardness. In S3, the tilt angle of the inclined surface is adjusted so that the main body reference static stiffness is within 50% to 70% of the target vertical static stiffness. In S5, the allowable deviation range of the overall finite element verification is ±15%.

10. The design method according to claim 8, characterized in that, In S4, a first boss is arranged on both sides of the bottom surface of the rubber layer (2), and a second boss is arranged in a 3-matrix in the middle area between the first bosses on both sides. The static stiffness of each boss is selected from the standard boss size-static stiffness lookup table and then summed in parallel.

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