Glossary of Failure Terms
Angel hair effect
The growth of tin-whiskers, which are hair-like crystalline structures, are known to cause short circuits in electronic components.
Cavitation erosion or damage
The process of surface deterioration and surface material loss due to the generation of vapour or gas pockets inside the flow of liquid.
Commonly found in ball or roller bearings, contact fatigue is where the motion of the rolling parts causes a shear stress in the curved surfaces resulting in surface cracking and pitting.
Surfaces can be protected against corrosion by the application of specialist coatings and, where appropriate, the induction of residual compressive stresses.
Initiation and propagation of cracks can be prevented or controlled by the tailored application of sustainable residual compressive stresses.
Foreign object damage
Where a component is damaged by external forces such as metal fragments, stones and debris.
Surfaces rub and fine abrasive oxides form which score the surface, which can lead to fretting fatigue which can be minimised by the protection of the base material through coatings and/or alteration of the mating surface contact points and deep residual compressive stresses.
The adhesion of opposing surfaces when in contact between two mating metal surfaces.
High temperatures can be created during the grinding process creating harmful tensile stresses.
Shot peening disrupts the grain boundary network at the metal surface, thus removing the pathway for the corrodant to travel, avoiding any intergranular attack.
Macro and micro pitting
Where two surfaces roll and slide in contact with each other, such as in rollers or gears which leads to a fatigue related loss of material in the surface
Stress corrosion cracking
Usually a failure in higher strength alloys caused by cracking under combined action of corrosion and static tensile stress, either external (applied) or internal (residual). The removal of surface tensile stresses or reduction below threshold levels can eliminate stress corrosion cracking.
This can be reduced by improving friction characteristics and increasing mating hardness.
Heat generated by the welding process will often produce tensile stresses which contribute to poor fatigue characteristics