How do hexagon flange bolts achieve superior anti-loosening performance in vibrating environments thanks to their flange design?
Publish Time: 2025-09-23
Bolted connections are ubiquitous in modern industrial equipment, from high-speed engines to heavy construction machinery, from rail vehicles to wind turbines. However, these devices face a critical challenge: constant vibration and alternating loads. Under these operating conditions, traditional bolted connections are prone to loosening due to slight relative slippage. This can lead to abnormal noise and reduced precision, or even structural failure or even accidents. Hexagon flange bolts, with their unique structural design, are a highly reliable fastening solution for vibrating environments. Their flange design, in particular, provides superior anti-loosening performance.1. The flange increases the bearing area and reduces surface compressive stressThe most notable feature of hexagon flange bolts is the integrated, widened flange below the bolt head. This design addresses the problem of traditional bolts easily "sag" in soft or thin-walled materials. During the pre-tightening process, the bolt generates a significant axial clamping force, which is transmitted through the bolt head to the surface of the connected component. If the contact area is too small, the pressure per unit area will increase dramatically, leading to localized plastic deformation or fatigue damage in the material, which in turn weakens the clamping force and induces loosening. The flange surface of hexagon flange bolts significantly expands the load-bearing area, evenly distributing the clamping force over a larger area, effectively reducing the compressive stress per unit area. This uniform pressure distribution not only prevents surface collapse of the connected parts but, more importantly, maintains long-term stability of the preload, fundamentally reducing the risk of loosening due to stress relaxation.2. The flange surface provides high friction resistance, inhibiting relative slipThe core mechanism of vibration-induced bolt loosening is that, under the action of alternating external forces, minute reciprocating relative slip occurs between the connected parts or between the threaded pairs. This slip gradually weakens the preload, ultimately leading to complete bolt loosening. The flange surface of hexagon flange bolts is a key line of defense against this phenomenon. When the flange surface contacts the connected parts, it forms a large-diameter frictional contact surface. When the bolt is tightened, this contact surface generates extremely high frictional resistance, effectively inhibiting lateral movement between the connected parts. Even when equipment vibrates during operation, the flange surface acts like a "suction cup" to firmly "grip" the connection surface, preventing a chain reaction of loosening caused by fretting wear. Some high-end hexagon flange bolts also feature serrations or knurling on the flange surface to further increase the friction coefficient, achieving a dual anti-loosening effect of "mechanical locking + friction locking."3. Integrated Construction Prevents Washer Failure and Improves Connection ReliabilityTraditional hexagon bolts often require flat washers for anti-loosening applications to increase the bearing area. However, washers are separate components, subject to problems such as loss, misassembly, displacement, or pressing into the material. Especially during automated assembly or under prolonged vibration, washers can become dislodged or fail, significantly reducing their anti-loosening effectiveness. Hexagon flange bolts integrate the washer function into the bolt body, creating an integrated structure. This design not only simplifies the assembly process and reduces the number of parts, but more importantly, completely eliminates the risk of washer-related failure. The flange surface maintains a consistent coaxial and rigid connection with the bolt head, ensuring consistent anti-loosening performance with every tightening, significantly improving the reliability and maintainability of the connection system.4. Achieving Stable Preload with Torque ControlPreventing loosening requires establishing and maintaining sufficient preload. The flange design of hexagon flange bolts helps reduce "embedding loss" during tightening—preload loss caused by the bolt head or washer pressing into the surface of the connected component. This more evenly distributes pressure and minimizes material deformation, resulting in a higher and more stable effective preload converted into clamping force. Furthermore, the flange provides a larger support surface for the tightening tool, reducing the risk of wrench slippage or damage to the bolt head. This facilitates precise torque control and ensures that every bolt meets the designed preload requirement.In harsh vibration environments, hexagon flange bolts, with their integrated flange design, create a robust anti-loosening barrier through multiple mechanisms, including increased pressure-bearing area, enhanced frictional resistance, suppressed relative slip, and prevented embedding failure. This is not only a structural optimization but also a systematic improvement in connection reliability. From automotive powertrains to rail transit bogies, from industrial robots to wind turbine towers, hexagon flange bolts are becoming an indispensable fastening option in high-vibration and high-dynamic load scenarios due to their excellent anti-loosening performance.
