In bolting systems, service-induced discontinuities may be produced by which of the following?

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

Answer: (D)

In bolting systems, service-induced discontinuities arise when the joint’s integrity is altered during operation, changing how load is transferred through the connection. Vibration subjects the joint to cyclic loads that can loosen the clamp and initiate fatigue cracks in bolts, threads, or contact surfaces, creating a break in the smooth load path. Over-tensioning pushes the bolt beyond its design preload, causing plastic deformation or thread damage and potentially neck or shear failures, which disrupt the uniform clamping and load distribution. Corrosion erodes material at threads and interfaces, reducing cross-section, promoting crack initiation, and altering contact conditions, all of which undermine the joint’s ability to carry load consistently. Since any of these mechanisms can introduce a discontinuity in how the joint carries load, all of the above is the best answer. In practice, controlling preload, protecting against corrosion, and avoiding excessive tightening help maintain a continuous, reliable load path.