In bolting systems, which of the following can contribute to service-induced discontinuities?

• A. Vibration
• B. Over-tensioning
• C. Corrosion
• D. All of the above

Answer: (D)

Service-induced discontinuities in bolted joints arise when operating conditions alter how the joint carries load, creating gaps, looseness, cracks, or changes in how clamping is shared. Vibration introduces cyclic loads and micro-motions that can loosen threads, wear contact surfaces, and fatigue the joint, leading to irregular load transfer. Over-tensioning pushes materials beyond their elastic range, causing plastic deformation or thread damage that disrupts the uniform clamp and creates changes in the joint’s stiffness and response under service. Corrosion gradually eats away material and weakens contact surfaces, especially at threads and slip paths, reducing preload and enabling pits or cracks that disrupt continuity of the load path. Because any of these factors can produce the desired discontinuities, all of the above can contribute to service-induced discontinuities.