Fatigue (material)
Videos
Page
In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts of the fracture surface. The crack will continue to grow until it reaches a critical size, which occurs when the stress intensity factor of the crack exceeds the fracture toughness of the material, producing rapid propagation and typically complete fracture of the structure.
Fracture surface of an aluminium crank arm from a bicycle. The dark area (due to oil, dirt and fretting) is a slow growth fatigue crack and may contain striations. The bright area is caused by sudden fracture.
Micrographs showing how surface fatigue cracks grow as material is further cycled. From Ewing & Humfrey, 1903
Fracture surface in a glass rod showing beach marks surrounding the initiation site.
Example of a HFMI treated steel highway bridge to avoid fatigue along the weld transition.
Structural integrity and failure
Videos
Page
Structural integrity and failure is an aspect of engineering that deals with the ability of a structure to support a designed structural load without breaking and includes the study of past structural failures in order to prevent failures in future designs.
Collapsed barn at Hörsne, Gotland, Sweden
The Pyramid at Meidum was the second built by the Egyptians around 2600 BC. It suffered from many structural defects, causing it to collapse during construction and leaving the inner core standing in a pile of rubble, which provided one of the earliest known lessons in large-scale building.
Building collapse due to snow weight
The Dee bridge after its collapse