Meaning
Conical metal discs designed to be loaded along the axial direction provide a high spring rate in a compact physical volume. A belleville spring washer is commonly placed under the head of a bolt or nut to maintain tension in joints that experience thermal expansion or creep. The washer flattens under load, storing mechanical energy that it releases if the joint thickness changes.
Elastic Recovery
Large dimensional changes that standard flat washers cannot accommodate are common during thermal cycling of power electronics boards. The belleville spring washer maintains continuous clamping force by flexing as the stack expands and contracts, which prevents gaps from forming at the interfaces. This dynamic response is useful in assemblies that combine materials with highly divergent coefficients of thermal expansion.
Load Behavior
The load deflection curve of a conical disc is non-linear and allows for specific forces to be sustained over a wide range of compression. When the belleville spring washer is tightened to its flat position, it acts as a solid washer but retains its spring energy to counter any subsequent relaxation or settlement. This characteristic ensures that electrical terminal connections do not loosen under vibration.
Stress Tolerance
High stress concentrations at the inner and outer diameters require careful material selection and heat treatment during manufacturing to prevent premature cracking under dynamic loads. In applications with limited space, multiple washers are stacked in series to increase total deflection or in parallel to increase the load-carrying capacity of the joint. This flexibility makes the belleville spring washer a standard solution for securing high-current busbars where space is at a premium, as it guarantees that the tension remains within the elastic limits of the assembly throughout its operational life.
