Fracture mechanics

The fracture mechanics deals with the failure of cracked components or the propagation of cracks under static and dynamic loads up to fracture. It includes elements of materials science, the elastomechanics and plastomechanics.

Basics

Crack and break

Allen fracture mechanics concepts have in common that an existing defect (crack ) is assumed in the component. This may have arisen or similar or only in use, for example be formed under cyclic stress due to the manufacturing process as voids, inclusion, stress cracking. The damage mechanism treats the emergence and spread of these micro- cracks of up to 1 mm in length. Based on assumptions about the geometry and stress this flaw, be formulated with a measure of toughness conditions under which it is to an illegal crack growth up to the break, which exceed the fracture strength comes. The reliability of the classic strength calculation should thus be increased.

Classification of fractures

• Brittle fracture (also brittle fracture )
• Fatigue fracture (also fatigue fracture )
• Ductile fracture (also ductile fracture)

Concepts of fracture mechanics

The following fracture mechanics concepts are known:

• Linear elastic fracture mechanics ( LEFM, especially suitable for brittle materials ) Nominal stress concept

• CTOD concept
• J -integral concept

History

In the 1930s and 40s, there was an accumulation of catastrophic damage caused by brittle fracture of large welded steel structures such as ships and bridges. From the examination of these damages is a separate field of study whose subject is the behavior of cracked body developed.

The fracture mechanics experienced in particular in relation to the interpretation of nuclear components in the 1970s, a rapid development.

Today's models can also be about the sinking of the Titanic as a fracture failure of a wrong alloy steel reconstruct.

With AFGROW a software for fracture mechanics and crack propagation calculations in the context of stability testing of metallic materials available.