Failure of Materials in Service What is Failure? How is it defined?

Failure of Materials in Service

What is Failure?

How is it defined?

Is this failure?

What about this?

Or this?

Familiar Failure

• Conventional tensile failure mode that we are all familiar with.

Brittle Fracture

Ductile Fracture

Failure in Compression

Failure in Torsion

Failure in Bending

Stiff stuff getting bent!

Failure in little bits!

Sneaky failure

Fatigue Failure

Quietly in the hidden places failure

You would not be worrying about this failure at the

time it occurred!

Will you ever fly in a plane again!

Bolting the door after the …..

Expensive can-opener!

A new slant on bird ingestion

Where did that runway go?

Brake failure or pilot error?

Pardon me sir!

This was frozen when I took off!

A watery grave

Why Failure?

All unanticipated mechanical failures must have a cause:

• Designed incorrectly• Manufactured incorrectly• Mis-maintained• Mis-operated

Typical modes of failure

•  tensile, compressive & shear•  bending (buckling)•  distortion, residual loads.•  creep (temperature / stress related)•  thermal shock•  corrosion (including stress corrosion)•  ageing•  wear, fretting• fatigue• And lastly, cracks in the fuselage!