Fatigue Failures of Fasteners: Optical Metallography and SEM Fractography

Fatigue of Threaded Fasteners

ADVANCED MATERIALS & PROCESSES • AUGUST 2014 18 F asteners play a critical role in engineered structures as a method of nonpermanent joining for the aerospace, infrastructure, civil, automotive, energy generation/distribution, and many other industries. Fastener failures can lead to disastrous consequences and substantial financial losses. One of the most common fastener failure modes is fatigu...

The Metallography of Impact Fatigue

Electromagnetic Detection of Fatigue Cracks under Protruding Head Ferromagnetic Fasteners

The detection of fatigue cracks under installed fasteners has been a major goal of the aging aircraft NDE community. The Sliding Probe, Magneto-Optic Imager, Rotating Self-Nulling Probe, Low Frequency Eddy Current Array, and Eddyscan systems are among the instruments developed for this inspection. It has been verified that the detection of fatigue cracks under flush head aluminum and titanium f...

Color Metallography

Fig. 2 Microstructure of as-cast Au22%Al showing the “purple plague,” AuAl2 intermetallic (reddish), surrounded by the Al-AuAl2 eutectic after polishing to a 1 lm finish. Magnification bar is 50 lm long. Fig. 1 Microstructure of a porous high-carbon steel powder metallurgy specimen infiltrated with copper showing the natural color of the copper, which is easier to see when the steel has been ti...

Bending Fatigue Failures of Compressor Valve Reeds

Bending fatigue failures OI cantilever type suction valve reeds occurred under operating conditions in a semi-hermetic refrigerant compressor during field trials. The finite element method (FEM) was applied to predict both the static and dynamic displacements and the resultant stresses of the reeds. The dynamic stresses in the location of the fracture exceeded the fatigue limit of the reed stee...