Editing Fracture mechanics (section)

==Motivation==
The processes of material manufacture, processing, machining, and forming may introduce flaws in a finished mechanical component. Arising from the manufacturing process, interior and surface flaws are found in all metal structures. Not all such flaws are unstable under service conditions. Fracture mechanics is the analysis of flaws to discover those that are safe (that is, do not grow) and those that are liable to propagate as cracks and so cause [[structural failure|failure]] of the flawed structure. Despite these inherent flaws, it is possible to achieve through [[damage tolerance]] analysis the safe operation of a structure.  Fracture mechanics as a subject for critical study has barely been around for a century and thus is relatively new.<ref name="anderson">{{cite book 
 |title = Fracture Mechanics: Fundamentals and Applications
 |author = T.L. Anderson
 |publisher = CRC Press
 |year = 1995
 |isbn = 978-0849316562}}</ref><ref name="ewalds">{{cite book
 |title = Fracture Mechanics
 |author1 = H.L. Ewalds
 |author2 = R.J.H. Wanhill
 |publisher = Edward Arnold and Delftse Uitgevers Maatschappij
 |year = 1984
 |isbn = 978-0-7131-3515-2}}</ref>

Fracture mechanics should attempt to provide quantitative answers to the following questions:<ref name="ewalds"/>
# What is the strength of the component as a function of crack size?
# What crack size can be tolerated under service loading, i.e. what is the maximum permissible crack size?
# How long does it take for a crack to grow from a certain initial size, for example the minimum detectable crack size, to the maximum permissible crack size?
# What is the service life of a structure when a certain pre-existing flaw size (e.g. a manufacturing defect) is assumed to exist?
# During the period available for crack detection how often should the structure be inspected for cracks?