Visual Testing (VT) Practice Exam

Which location is the least common for fastener failure?

1. in the head to shank fillet

2. throughout the first thread inside the nut on threaded fasteners

3. in the mid grip

4. at the transition from the thread to the shank

The correct answer is: in the mid grip

The mid grip is considered the least common location for fastener failure due to the distribution of forces and the design of fasteners. In a typical fastener, such as a bolt or screw, the areas under the most stress are often at the beginning of the threads, the head, or the transition zones where geometry changes significantly, such as from the threaded part to the shank. The mid grip or the shank portion is generally subjected to different types of loads compared to the threaded areas or the components nearest the head. Consequently, while this region does experience some stress, it tends to be less severe than in the areas where the threads engage or where there are stress concentrations due to geometric transitions. Given these mechanical properties and load distributions, failures are less likely to occur in that section compared to the more critical areas. This understanding of fastener mechanics highlights why mid grip is the least common location for failure.