Forces and Failures

There are four types of forces, and each type causes its own failure mode:
Tension-When a material is pulled from either end it will elongate,  and eventually  it will "snap," meaning the material breaks into two pieces.

Compression-When a material is pushed together from opposite sides  there are two possible outcomes. 1) The material can bend, or "buckle" under the force.
2) The material will shift, or "shear," where different parts move in different directions.

Torsion-Twisting the ends of a material in opposite directions will eventually cause  the material to shift passed itself,  meaning the failure method is similar to a compression  failure, in this case it is known as "twist."

Shear-Pushing different parts of material too far in  different directions results in a failure known as "shear."