Fully Preventable Fatigue Failure
Steve Reilly
Fully Preventable Fatigue FailureOne of the most frequently seen fastener failures we are asked to analyze involves fully preventable fatigue failure. Today we will review just such a case.
Six fractured, 1/2″ diameter x 5″ long bolts were received for metallurgical failure analysis. The bolts were used in a clamping device to clamp the ends of a flexible vertical conveyor belt. The fractured bolts had been in service for less than three months. In addition to the fractured bolts, two additional bolts that had been in service for four to five years without failure were submitted for comparative analysis. All bolts were reportedly SAE Grade 5 bolts.
The two intact gold boltsh were labeled A1 and A2. The fractured bolts were labeled B1 through B6 for tracking purposes. The client requested that each of the fractures be documented, but no more than three fractured bolts be selected for destructive testing. One bolt is used for each clamping device, and bolts are specified to be tightened to a torque load of 75 ft-lb or 100 ft-lb depending upon the belt size.
Visual Examination (…)
via Fastener Technology International – August/September 2012 : Fully Preventable Fatigue Failure.