Development of Fracture Control Methodology for Threaded Fasteners in the Space Program
SourceHigh-strength threaded fasteners are used in many critical applications in aer- ospace hardware. This paper outlines a fracture control methodology that can be applied to prevent their structural failure due to the presence and/or propagation of crack-like defects. In cases where the failure of a single fastener would result in a catastrophic failure, fracture control is usually implemented either by nondestructive inspection followed by a fracture me- chanics analysis of life or by a proof test approach. Special nondestructive techniques are usually required for flaw detection at thread roots. This paper discusses the procedures necessary for determining probability of detection values for threaded fasteners, including methods of fabricating threaded fatigue crack specimens and the statistical methods used to reduce reliability data.