Fastener or Foe: When Fasteners Get Blamed For Failing

When a component fails in service or during assembly, it becomes the prime suspect for its own failure. When there are hundreds, thousands, or tens of thousands of the same type of part on a machine, there are many opportunities for failure. Such is the case with threaded fasteners. Advancements in strength, coatings, and assembly techniques have made threaded fasteners more versatile and useful than ever in the assembly of machines but have also created high profile cases of fastener failures from the unforeseen consequences of some of these advancements (the dreaded hydrogen embrittlement being the most obvious of these). Highly visible and catastrophic fastener failures got enough attention to inspire the Fastener Quality Act of 1990, which has had a significant impact on the industry since. However, as any good failure analyst knows, things aren’t always as simple as they seem. Improper design of bolted joints, insufficient tightening strategies, harsh use environments, and other issues can cause a perfectly good fastener to fail in spite of having been produced to specification. Here we’ll focus on tracking down and addressing some of those issues and propose some signs to watch for when performing failure analysis work on fastener failures.