Library of Failures

Bearing Rolling Contact Fatigue

A rolling element bearing exhibiting rolling contact fatigue (RCF) spalling of the working surfaces.

Ball Plate Cracking

Cracked, martensitic (hardened) grey cast iron ‘ball plate’ used to shape ball bearings.

316L Process Pipe Corrosion

Three weeks after installation, 316L pipework started to leak from pinhole defects. These were predominantly located at welds that exhibited high temperature oxidation (heat tints) at the heat affected zones. Those welds that did not exhibit such oxidation were unaffected.

Overheated Bearing Shells

The white-metal-coated steel bearing shells on a crankshaft had failed during testing. Examination revealed that the core of the bearing had a ferrite and pearlite microstructure, but in some areas the working surface has been transformed to bainite.

Overload Cracking of Gear

The gear flanks exhibited large amounts of deformation and wear consistent with high loads during service. Cross-sectional examination of the teeth showed multiple brittle or staged cracks to have propagated from the flank surface though the edge of the case, with dominant cracks opening up in the latter stages of the failure.

Quench Cracking of Forging

A forging was found to be cracked at inspection by using magnetic particle inspection.

Reverse Engineering of 1960s Locomotive Component

A bell housing used on a 1960’s locomotive required remanufacturing and the original component, that was beyond economical repair.

Staged Overload of Threaded Component

Visual examination of the fracture revealed the initiation portion to be at nominally 45°, which is typical of shear.

Torsional Overload of Crankshaft Spline

The fracture surface was relatively flat and displayed radial arced markings on the majority of the fracture surface.

Torsional Overload of Threaded Shaft

A threaded shaft had fractured at an end face of a nut. The shaft had failed by torsional overload and evidence of twisting of the bolt section was observed on microexamination of cross-sections.

Fracture of Aluminium Component Due to a Casting Defect

Examination of the fracture at low magnification revealed a change in fracture surface colour and form for approximately two thirds of the surface area.

Degradation of Kolsterising Coating and associated damage

Examination revealed that the surfaces of the seized eye and boss had degraded by a fretting mechanism with the resulting deposits having caused seizure of the joint.

Casting Defect in Cast Steel flange

The crack propagation was consistent with the opening (and joining up) of pre-existing interdendritic shrinkage cracks.

Casting Defect in Copper Alloy

Tapping Tee joints used in water pipe applications had been found to leak from a pin hole defect after installation in service.

Stress Corrosion Cracking of a Copper Alloy Component

A copper alloy component had cracked in service and the cracks exhibited a degree of ‘yawning’ (opening) indicative of the presence of tensile stress.

Torsional Overload of Lifting Chain

Fractured chain used in service to lift a skip used inside a grit-blasting chamber. The chain consisted of 10mm links with a C-hook, an ‘egg link’, and an eye.