Fracture mechanics
The fracture mechanics deals with the failure of cracked components or the propagation of cracks under static and dynamic loads up to the break . It contains elements of materials science , elastostatics and plastomechanics .
Basics
Crack and break
All fracture mechanics concepts have in common that an already existing defect ( crack ) in the component is assumed. This can arise as a result of the manufacturing process as blowholes , inclusions , stress cracks or the like, or it can only be formed during use, e.g. B. with cyclical loading . The damage mechanics deals with the emergence and spread of these micro-cracks of up to 1 mm in length. On the basis of assumptions about the geometry and stress of this flaw, a toughness measure is used to formulate conditions under which impermissible crack growth and even fracture (by exceeding the breaking strength ) occur. The reliability of the classical strength calculation should thus be increased. The fracture toughness of a material is a measure of the ease with which cracks form and enlarge in this material.
Systematics of fractions
- Brittle fracture (also separating fracture)
- Fatigue fracture (also fatigue fracture)
- Deformation fracture (also ductile fracture)
Fracture Mechanics Concepts
The following fracture mechanics concepts are known:
- Linear-elastic fracture mechanics (LEBM, particularly suitable for brittle materials)
- Flow rupture mechanics (FBM, particularly suitable for ductile materials)
history
The British engineer Alan Arnold Griffith investigated the influence of superficial scratches on stability and developed a theory of fracture, in particular a fracture criterion of brittle fracture .
In the 1930s and 40s there was an accumulation of catastrophic damage from brittle fracture to large welded steel structures such as ships and bridges . From the investigation of this damage, an independent discipline developed whose subject matter is the behavior of cracked bodies.
Fracture mechanics experienced rapid further development in the 1970s , particularly in connection with the design of nuclear components.
Today's models allow the sinking of the Titanic to be reconstructed as the failure of a wrongly alloyed steel.
With the software AFGROW , the previous versions of which were programmed from the beginning of the 1980s, a tool is available for calculating fracture mechanics and crack propagation within the framework of stability studies of metallic materials.
literature
- TL Anderson: Fracture Mechanics; Fundamentals and Applications . CRC Press, Boca Raton 2004, ISBN 978-0-8493-1656-2 .
- D. Gross, Th. Seelig: fracture mechanics with an introduction to micromechanics . 4th edition. Springer, Berlin 2007, ISBN 978-3-540-37113-7 .
Web links
- Fundamentals and applications of fracture mechanics (PDF) accessed on September 13, 2018
- Fundamentals of fracture mechanics (PDF) accessed on September 13, 2018
- Does the application of fracture mechanics make sense (PDF) accessed on September 13, 2018
- Plasticity and fracture mechanics (PDF) accessed on September 13, 2018
- Fracture Mechanics (PDF) accessed on September 13, 2018
Individual evidence
- ^ AA Griffith: The Phenomena of Rupture and Flow in Solids . In: Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences . tape 221 , no. 582-593 , January 1, 1921, ISSN 1364-503X , p. 163–198 , doi : 10.1098 / rsta.1921.0006 ( royalsocietypublishing.org [accessed March 31, 2016]).