In various aspects of production and daily life, bolt connections often include a washer. However, the necessity and purpose of washers in these connections can sometimes be unclear. This article explores the design of bolt connections and discusses when and why washers are used.
When Flat Washers are Necessary for Bolt Connections
Flat washers play a significant role in fastening systems, offering various benefits and being employed in several scenarios to achieve specific outcomes.
1. Surface Protection during Frequent Disassembly
Flat washers are used to protect the surfaces of connected components during frequent disassembly. By placing a flat washer at the position of the nut or bolt head, the risk of surface damage is mitigated, particularly for precision-machined surfaces.
2. Meeting Friction Coefficient Requirements
In some cases, flat washers are used to meet precise friction coefficient requirements without separate testing. For instance, wind turbine bolt connections often use combination washers. In such situations, all components, including bolts, nuts, and washers, are provided by the same manufacturer, ensuring consistent friction coefficients between the nuts and washers. The supplier must also test and ensure that the torque coefficients meet technical requirements.
3. Reducing Pressure on Connected Components
When bolt strength is relatively high and the allowable stress in connected components is low, flat washers are essential. This is particularly relevant in the context of the growing demand for lightweight automotive structures. By adding flat washers, the pressure on the bearing surfaces of connected components is reduced, preventing yielding and permanent plastic deformation.
4. Pressure Distribution and Sealing
Flat washers are valuable when pressure distribution and sealing are required. Increasing the washer size enlarges the stress distribution diameter and ensures effective sealing between connected surfaces. This is crucial in applications where airtight or watertight seals are necessary.
5. Compensating for Positional Tolerance Deviations
In automotive manufacturing, where stamping and welding processes are prevalent, the positional tolerance of holes may not align perfectly. In such cases, larger hole diameters are used, and flat washers are added to compensate for positional tolerance deviations. This ensures proper alignment and a secure connection.
6. Ease of Installation Adjustment
For ease of installation adjustment, long holes are sometimes created in control arm brackets or control tables. In such instances, thick flat washers or specialized washers may be used to allow for adjustments within a certain range.
Why Spring Washers are Used for Anti-Loosening
spring washers also known as lock washers, are primarily employed to increase the friction force between nuts and bolts, thereby preventing loosening caused by equipment vibrations.
However, it is important to note that spring washers are not suitable for all situations. They are more commonly used in structures with minor impact loads or in less critical applications where anti-loosening requirements are not stringent. In cases where a single loose nut does not pose significant risks, spring washers can provide sufficient protection against loosening.
Nevertheless, it is crucial to consider the limitations and implications of using spring washers. In high-preload force applications or connections where reliability is critical, it is not recommended to rely solely on spring washers. Moreover, when important contact surfaces must be protected from damage, it is necessary to incorporate flat washers along with spring washers. Under dynamic loads, spring washers may have reduced effectiveness in high-strength bolt connections.
Conclusion
Washers play a vital role in bolt connections, providing benefits such as pressure reduction, increased friction, sealing, shock absorption, and fixation. While washers may not always be necessary, the use of flat washers or spring washers is often determined by specific requirements and design considerations. It is essential to carefully evaluate the demands of each connection and choose the appropriate washer type to ensure secure and reliable fastening. By understanding the necessity and purpose of washers, we can optimize bolt connections and enhance their overall performance and longevity.