Which of the following statements best describes preload?

Preload refers to the initial tension that is applied to a fastener, such as a bolt or screw, before any external loads or forces are applied. This initial tension is crucial because it helps to maintain the integrity and strength of the joint when subjected to external forces.

When preload is greater than any external forces acting on the joint, it ensures that the fastener remains securely clamped and can effectively resist the influence of those external forces. This is essential for preventing loosening, which can lead to joint failure. In applications where external forces are present—like vibrations or fluctuating loads—having a preload that exceeds these forces helps to maintain safety and structural integrity.

The other statements do not accurately reflect the important role of preload in fastener performance. For instance, stating that preload must be less than external forces would compromise joint stability, while claiming that preload is irrelevant contradicts its critical importance in joint integrity. Additionally, saying that preload must be equal to external forces overlooks the necessity of having sufficient margin to account for potential variations in load, which are common in practical applications.