Static fatigue

Static fatigue, sometimes referred to as delayed fracture, describes the progressive cracking and eventual failure of materials under a constant, sustained stress.

With static fatigue materials experience damage or failure under stress levels that are lower than their normal ultimate tensile strengths.

[2] The exact details vary with the material type and environmental factors, such as moisture presence[3] and temperature.

[10] Plastic deformation happens when stresses flatten, bend, or twist a material until it cannot return to its original shape.

[13][14] However, accurately assessing a material's true static fatigue life presents challenges, as these tests often require an extended duration and there is significant variability in the results.

Crack growth progression in a glass rod under cyclic stress (denoted by arrows). (1) shows the first crack. The cracks grow in (2) & (3) until the rod breaks in (4).