A spring washer creates tension and prevents loosening in a bolted joint by utilizing its unique design to provide additional friction and resistance. Here’s how it works:
Spring-Like Shape
Spring washers have a curved or conical shape, such as the helical shape of a split washer or the wave-like design of a wave washer. This shape gives the washer a spring-like characteristic that can compress under load and then return to its original shape when the load is removed.
When a bolt or screw is tightened, the spring washer gets compressed and exerts a continuous force (tension) between the nut and the bolted surface, creating a more secure connection.
Maintaining Tension in the Joint
The spring washer's tension compensates for any loosening that may occur due to vibrations, thermal expansion, or material settling. By maintaining tension, the washer ensures that the fastener remains securely in place.
Even if the components in the joint slightly move, the spring washer's compressed shape allows it to "push back" and maintain pressure on the fastener, helping to resist loosening.
Increased Friction
As the washer compresses, it also increases the friction between the fastener head or nut and the surface of the material being fastened. This additional friction further helps to prevent the fastener from turning or backing out under vibration or dynamic loads.
The edges of certain spring washers, like split washers, can dig into the surface of the material and the underside of the fastener, increasing the resistance to rotation.
Energy Absorption and Vibration Dampening
The spring action of the washer allows it to absorb small amounts of movement and vibration in the joint. This helps to dampen vibration, reducing the risk of the fastener loosening over time.
The washer acts like a buffer that accommodates slight shifts in the joint while still keeping the fastener tight.
Compensation for Thermal Expansion and Contraction
In environments where temperature changes cause materials to expand or contract, a spring washer can accommodate these dimensional changes. By maintaining pressure during expansion or contraction, the washer helps keep the fastener tight despite temperature fluctuations.
Preventing Relaxation of the Joint
Over time, bolted joints can experience "relaxation," where the clamping force decreases due to factors like material creep or settling. The continuous tension from the spring washer can counteract this loss of clamping force, ensuring the joint remains secure.
Limitations
While spring washers are effective in many applications, they may not be suitable for joints requiring extremely high tension or for high-stress environments where more advanced locking mechanisms are necessary. For these situations, additional locking methods like locking nuts or adhesive thread lockers may be required.
