What does failure mean in mechanical engineering

In technical mechanics, stress means the effect on the interior of a body or material that is caused by external stress. Various types of stress can be responsible for this. Mechanical stress triggers the creation of mechanical stresses.

A distinction is made between the types of stress:

a) Stress from mechanical influences (static / dynamic)
b) Exposure to environmental influences (e.g. moisture, heat, chemical reactions)

Component failure due to load & stress

The strength theory * makes a very differentiated distinction between component failure that occurs due to loads. If a failure of the material is caused by a one-off strong overstressing, it is a so-called force fracture. In the field of technical mechanics, the term fatigue (materials science) is understood to mean the alternating stress that lasts over a longer period of time well below the yield point (failure limit), which ultimately leads to failure of the material.
This means that both the duration of exposure and the level of exposure - i.e. the intensity - play a decisive role.