Anti-fatigue hexagonal bolt

Abstract

The utility model discloses a kind of anti-fatigue hexagon bolts, belong to fastener technical field.The bolt includes bolt head, light rod part and screw thread part.The light rod part is equipped with annular accommodating groove, and its inside is embedded with composite damper;The damper is composed of rigid framework ring and the flexible damper body covered outside, annular cavity filled with non-newtonian fluid or high-viscosity silicone grease is equipped in flexible damper body, and its outer surface protrudes from light rod part.In addition, bolt head and light rod part are connected by the composite circular arc transition zone formed by multiple tangent circular arcs between them.The utility model actively consumes vibration energy by the multistage buffering effect of damper, and effectively reduces stress concentration in combination with composite circular arc transition zone, to significantly improve the anti-fatigue performance and service life of bolt under harsh working conditions such as frequent vibration, large load change, with higher reliability.

Description

Technical Field

[0001] This utility model relates to the field of fastener technology, specifically to a fastening bolt suitable for use under high-frequency vibration and alternating load conditions, and more particularly to a fatigue-resistant hexagonal bolt with a multi-level buffer damping structure and a composite arc transition in the high-stress zone. Background Technology

[0002] Hex bolts, as one of the most commonly used fasteners, are widely used in critical connection parts of wind power generation equipment, heavy vehicles, rail transportation, aircraft structures, and industrial machinery. In these applications, bolts not only need to withstand static preload but also operate under harsh environments with frequent changes in vibration, impact, and load amplitude over extended periods. Under such dynamic loads, the main failure mode of bolts is fatigue fracture, and fatigue cracks typically initiate in areas of highest stress concentration, such as the transition zone between the bolt head and the smooth shank, and the thread termination.

[0003] In the prior art, the following measures are usually taken to improve the fatigue resistance of bolts: 1. Increase the radius of the transition fillet: This is the most common method, which reduces the stress concentration factor by using a larger single arc radius. However, this method is limited by the structural space of the connected parts (such as the space for a wrench), and the fillet radius cannot be increased indefinitely, thus limiting its improvement in fatigue resistance.

[0004] 2. Using a rolling process: Rolling the threads and transition fillets creates a work-hardened layer and residual compressive stress on the surface, thereby inhibiting the initiation of fatigue cracks. While effective, this method requires high precision in the process, and the residual stress may relax under long-term high temperatures or overloads.

[0005] 3. Structural optimization design: such as designing load-reducing grooves. However, this type of design often only optimizes the geometry and fails to fundamentally solve the problem of continuous impact of vibration energy on the bolts. The dynamic load generated by vibration will continuously aggravate fatigue damage in stress concentration areas.

[0006] In summary, traditional methods primarily focus on optimizing the geometry of the bolt body to "resist" stress concentration, which is a passive protection approach. Their ability to dissipate continuous high-frequency energy impacts introduced by external vibration sources is limited. Single structural optimizations often reach their upper limit in improving fatigue life when facing complex and variable dynamic loads, making it difficult to meet the long-life requirements of industries with extremely high reliability demands, such as wind power generation. Existing bolt structures themselves do not possess the function of actively absorbing and dissipating vibration energy, and therefore cannot fundamentally reduce the dangerous loads acting on the bolts. Summary of the Invention

[0007] To overcome the aforementioned deficiencies of the prior art, this utility model aims to provide a multi-stage buffer-type fatigue-resistant hexagonal bolt. This bolt, through a composite damper structure and a composite arc transition design, achieves an organic combination of passive structural fatigue resistance and active damping vibration reduction, significantly improving its service life and reliability under harsh working conditions such as frequent vibration and large load variations.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A fatigue-resistant hexagonal bolt includes a bolt head, a smooth shank, and a threaded portion. The smooth shank has at least one annular receiving groove in its radial direction. A composite damper is embedded in the annular receiving groove. The composite damper includes a rigid skeleton ring and a flexible damping body covering the rigid skeleton ring. The composite damper is interference-fitted with the smooth shank. The flexible damping body has a closed annular cavity inside, and the outer circumferential surface of the flexible damping body protrudes beyond the outer circumferential surface of the smooth shank in its natural state.

[0009] Preferably, the annular cavity is filled with an adhesive, which is a non-Newtonian fluid or a high-viscosity silicone grease.

[0010] Preferably, the cross-sectional shape of the annular cavity is elliptical or circular, and its cavity wall thickness is uneven, forming at least one thin-walled buffer area. The thin-walled buffer area is located in the area where the flexible damping body is expected to have the greatest contact pressure with the wall of the connector hole.

[0011] Preferably, the lower bearing surface of the bolt head is connected to the smooth rod portion via a composite circular arc transition zone.

[0012] Preferably, the cross-sectional profile of the composite circular arc transition zone is formed by smoothly connecting at least two tangent circular arcs with different radii.

[0013] Compared with the prior art, this utility model has the following advantages: 1. Combining active and passive protection with advanced fatigue resistance mechanism: This invention goes beyond simple structural optimization. The composite damper constitutes an "active" vibration reduction system, efficiently converting and dissipating harmful vibrational mechanical energy through the elastic deformation of the flexible damper and the viscous shear of the internal cavity fluid, thus reducing the amplitude of the dynamic load acting on the bolt at its source. Simultaneously, the composite arc transition zone acts as a "passive" strengthening structure, minimizing stress concentration in critical areas of the bolt body. The synergistic effect of both achieves a comprehensive solution, with fatigue resistance far exceeding that of a single technical solution.

[0014] 2. Multi-stage buffering, superior performance: The composite damper itself constitutes a multi-stage buffering mechanism. The first stage is the elastic deformation of the flexible damping body; the second stage is the fluid damping effect generated by the internal cavity under pressure (especially when filled with non-Newtonian fluid). The viscosity of non-Newtonian fluid increases dramatically under impact, providing extremely large damping force instantaneously, making it particularly suitable for impact-resistant conditions. This multi-stage mechanism gives the bolt excellent adaptability to vibrations of different frequencies and amplitudes.

[0015] 3. Targeted design for high reliability: By designing a non-uniform wall thickness to form a "thin-walled buffer zone," the buffering effect can be concentrated at the circumferential position where the force is greatest, maximizing efficiency. The rigid skeleton ring design ensures a reliable connection between the damper and the bolt body, preventing loosening under long-term vibration and improving the durability of the entire system.

[0016] 4. Compact structure and easy implementation: All improvements are integrated within the standard geometry of the bolt itself, without requiring changes to the matching nut and connected parts. Installation and use are no different from ordinary bolts, facilitating widespread adoption. Furthermore, this structure is ideally suited for standardized mass production. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure; Figure 2 This is a magnified view of point A; Figure 3 This is a magnified view of point B.

[0018] In the diagram: 1- Bolt head; 2-Smooth rod; 3-Threaded part; 4-Composite arc transition zone; 5-Annular receiving groove; 6-Composite damper; 61-Rigid skeleton ring; 62-Flexible damping body; 63-Annular cavity; 64-Adhesive; 65-Thin-walled buffer area; Detailed Implementation

[0019] The structure of this utility model will now be fully described in conjunction with specific embodiments so that those skilled in the art can fully understand and implement it.

[0020] like Figures 1 to 3 As shown, this utility model discloses a fatigue-resistant hexagonal bolt, the main structure of which includes a bolt head 1, a smooth shank 2, and a threaded portion 3. The bolt material can be high-strength alloy steel, and it undergoes quenching and tempering heat treatment to obtain the required strength and toughness.

[0021] The core improvement of this embodiment lies in the fact that an annular receiving groove 5 is machined radially on the optical rod portion 2. A composite damper 6 is tightly assembled within this annular receiving groove 5.

[0022] See Figure 2The enlarged view shows that the composite damper 6 consists of two parts: a rigid skeleton ring 61 and a flexible damping body 62. The rigid skeleton ring 61 can be made of metal (such as anodized aluminum alloy or stainless steel) or high-strength engineering plastic (such as polyetheretherketone, PEEK). The composite damper 6 is pressed into the groove by an interference fit to ensure that it will not loosen or shift during bolt use.

[0023] The flexible damping body 62 is completely wrapped around the outer periphery of the rigid skeleton ring 61 through compression molding or secondary injection molding. The material of the flexible damping body 62 can be a polymer with high elasticity, good damping characteristics and aging resistance, such as nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR) or polyurethane (PU). In its natural state, the outer peripheral surface of the flexible damping body 62 protrudes from the outer circumferential surface of the smooth rod portion 2, forming a certain interference fit to ensure that the damping body can maintain continuous and tight contact with the hole wall after the bolt is installed into the connecting hole.

[0024] The flexible damping body 62 has a closed annular cavity 63 formed inside. This cavity 63 is integrally formed during the damper manufacturing process, and its interior is a sealed space.

[0025] Further configuration: The annular cavity 63 is filled with an adhesive 64. Here, "adhesive" mainly refers to a fluid or semi-fluid substance with high viscosity properties; its function is not only filling but, more importantly, providing viscous damping. Preferred fillers are non-Newtonian fluids (such as shear-thickening fluid STF) or high-viscosity silicone grease. The filling process can be completed after the damping body has been vulcanized and molded, by injection through a micro-injection hole followed by sealing, or by pre-placing the damping material in the mold before molding.

[0026] When the bolt is subjected to vibration, the deformation of the flexible damper 62 compresses the annular cavity 63, forcing the internal binder 64 to undergo intense shear flow. If the filler is a non-Newtonian fluid, its viscosity will increase sharply under high-speed shear, generating significant damping force, thereby efficiently converting vibration energy into heat dissipation.

[0027] To further optimize the buffering performance, the cross-sectional shape of the annular cavity 63 can be designed as elliptical or circular. More importantly, its cavity wall thickness is designed to be non-uniform, thereby forming at least one thin-walled buffer region 65. The location of the thin-walled buffer region 65 is designed to be in the area where the flexible damper 62 is expected to exert the greatest contact pressure with the connector hole wall. In practical applications, this region can be determined according to the main load direction during bolt service. For example, for bolts subjected to bending loads in a fixed direction, the thin-walled region 65 can be placed in the circumferential position corresponding to that load direction. When a vibration load is transmitted, the thin-walled region 65, due to its lower stiffness, will preferentially generate greater deformation, more effectively stimulating the damping effect of the binder 64 within the cavity 63, achieving targeted buffering.

[0028] Further configuration: The lower bearing surface of the bolt head 1 is connected to the smooth shank 2 by a composite arc transition zone 4. This transition zone 4 is machined by precision grinding or cold heading, replacing the traditional single-radius fillet.

[0029] The cross-sectional profile of the composite arc transition zone 4 is formed by the smooth connection of at least two tangent arcs with different radii. In a specific example, two tangent arcs can be used: one arc with a larger radius (e.g., R1 = 0.20d, where d is the diameter of the smooth rod) is close to the smooth rod portion 2, and the other arc with a smaller radius (e.g., R2 = 0.08d) is close to the lower bearing surface of the bolt head 1. These two arcs have a common tangent at the connection point, ensuring a smooth transition of the profile without sharp points or corners, thereby greatly reducing the stress concentration factor in this critical area.

[0030] In a vibrating environment, the bolt of this invention achieves active vibration reduction through the composite damper 6: vibration energy is transferred to the flexible damper 62 through the hole wall, and its deformation and the shear flow of the binder 64 in the internal cavity 63 work together to consume a large amount of energy. Simultaneously, the bolt body structure optimized by the composite arc transition zone 4 can more effectively resist residual loads and suppress the initiation of fatigue cracks. The synergistic effect of active damping and passive structural optimization significantly improves the fatigue resistance of the bolt.

[0031] The above embodiments are only a few specific implementations of this utility model. Any changes and improvements made by those skilled in the art to the details under the guidance of the concept of this utility model should be included within the protection scope of this utility model.

Claims

1. A fatigue-resistant hexagonal bolt, comprising a bolt head (1), a smooth shank (2), and a threaded portion (3), characterized in that: The smooth rod portion (2) has at least one annular receiving groove (5) in its radial direction; a composite damper (6) is embedded in the annular receiving groove (5); the composite damper (6) includes a rigid skeleton ring (61) and a flexible damping body (62) covering the rigid skeleton ring (61); the composite damper (6) is interference-fitted with the smooth rod portion (2); the interior of the flexible damping body (62) is provided with a closed annular cavity (63), and the outer circumferential surface of the flexible damping body (62) protrudes from the outer circumferential surface of the smooth rod portion (2) in its natural state.

2. The fatigue-resistant hexagonal bolt according to claim 1, characterized in that: The annular cavity (63) is filled with an adhesive (64), which is a non-Newtonian fluid or a high-viscosity silicone grease.

3. The fatigue-resistant hexagonal bolt according to claim 2, characterized in that: The cross-sectional shape of the annular cavity (63) is elliptical or circular, and its cavity wall thickness is uneven, forming at least one thin-walled buffer area (65). The thin-walled buffer area (65) is located in the area where the flexible damping body (62) is expected to have the greatest contact pressure with the wall of the connector hole.

4. The fatigue-resistant hexagonal bolt according to claim 1, characterized in that: The lower bearing surface of the bolt head (1) is connected to the smooth rod part (2) through a composite arc transition zone (4).

5. The fatigue-resistant hexagonal bolt according to claim 4, characterized in that: The cross-sectional profile of the composite circular arc transition zone (4) is formed by smoothly connecting at least two tangent circular arcs with different radii.

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