Fracture Modes

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Fracture modes

General information

When deriving the fundamental relationships of fracture mechanics, three different possibilities for material separation at the crack tip (see also: crack) are assumed [1–3], resulting in a distinction between three crack opening modes.

In addition to the term ‘crack opening modes’, the terms ‘crack opening types’, ‘crack types’ and, in English-speaking countries, ‘crack tip opening mode’, ‘crack mode’ or simply ‘mode’ are also commonly used [4].

The term ‘fracture mode’ has also become widely used.

The crack opening types are also presented in the explanation of the term ‘fracture mechanics’ in Figure 1.

A more detailed description of the crack opening types is provided under ‘Crack opening modes’.

Types of crack opening

The basic explanations of the stress state (see also: stress) are always illustrated using the example of crack opening mode I, as this is of particular practical interest and in many cases best reflects the conditions associated with brittle fracture (see: types of fracture) in a real component.

Stress intensity factors for the types of crack opening

The stress intensity factors corresponding to the three crack opening modes (see: fracture mechanics) are designated K_I, K_II and K_III.

Crack opening mode II occurs under pure shear stress in the crack plane. Crack opening mode III plays a role in tensile stress (see also: tensile test) in thin components. While in crack opening modes II and III the crack surfaces mainly slide over each other, in opening mode I the fracture surfaces are moved away from each other, which facilitates the action of corrosive media if present. Crack opening mode III is most amenable to mathematical treatment [4].

See also

• Crack opening modes
• Crack
• Levels of knowledge in fracture mechanics
• Stress
• Fracture mechanics
• Mixed-Mode Crack propagation

References

[1]	Blumenauer, H., Pusch, G.: Bruchmechanik, Grundlagen, Prüfmethoden, Anwendungsgebiete. Deutscher Verlag für Grundstoffindustrie, Leipzig (1973) 1st Edition (see AMK-Library under E 28)
[2]	Anderson, T. L.: Fracture Mechanics. Fundamentals and Applications. 4th Ed., CRC Press Boca Raton (2017), (ISBN 978-0849342608; E-Book ISBN 978-1-3153-7029-3) DOI: https://doi.org/10.1201/9781315370293
[3]	Blumenauer, H., Pusch, G.: Technische Bruchmechanik. Deutscher Verlag für Grundstoffindustrie, Leipzig Stuttgart (1993), (ISBN 3-342-00659-5; see AMK-Library under E 29-3)
[4]	Heckel, K.: Einführung in die technische Anwendung der Bruchmechanik. Carl Hanser, Munich Vienna (1983 ), (ISBN 3-446-13943-5; see AMK-Library under E 30)