What are load and deflection in a joint?

A bolted joint stretches in response to a given load. Over time, this can cause the bolt to loosen.

Deflection is the motion that occurs in response to the application or removal of a load or a stress. It is the “spring” in a spring. As force is applied to a joint, deflection counteracts the force by absorbing it. The greater the deflection in a joint, the more load and stress it can withstand, which increases the longevity of the joint.

Belleville springs, used singly or stacked in series, increase deflection. Increasing the deflection means a greater load or stress can be applied to the jointed system without significant losses in the original tension of the joint.