Three Modes of Fracture

I’m working on a series explaining Fracture Mechanics. Please be patient.

Years ago I ran the Fracture Mechanics Lab at Pratt&Whitney. (We make jet engines and rocket engines.) From time to time I gave a brief overview of F/M for Managers. Here is an updated version.  Among the topics will be the discussion of some recurring catastrophic failures – failures attributed to not learning the lessons of Fracture Mechanics the first time around, and thus suffering a similar loss a generation later.


Three Fracture Modes

There are three fundamental modes of fracture, and more that are mixtures of them described by their “mixity.”

Mode I fracture is simple crack-opening,
where the crack faces are pulled apart.


Mode II fracture is crack face sliding (in-plane shear).


Mode III fracture is crack face tearing
(out-of-plane shear).