A review of static crack arrest concepts

✍ Scribed by E.J. Ripling; P.B. Crosley; S.J. Wiersma

• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 1018 KB
• Volume: 23
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(86)90174-8

✦ Synopsis

The plane-strain crack-arrest fracture toughness Kr, is measured with relatively small specimens that are analyzed by static methods. The large number of studies that have been carried out to determine whether or not this kind of analysis gives an adequate description of K at the end of a run-arrest event are reviewed. and it is shown that the present wide acceptance of Kli, as an invariant material property is justified. Two kinds of data were examined. The first kind consisted of strain, crack velocity and K measurements that were made during a runarrest event. It was found that early in the event the crack velocity ir is high. and over this period the specimen behavior can only be described by a dynamic analysis. As ir decreases, and the crack coasts to an arrest, the specimen behavior is adequately described by a static analysis. (Measurements made by the method of caustics on both metal and epoxy specimens that showed a large crack jump may be an exception to this.) Strain and K oscillations, generally of a small amplitude, do continue up to the time of arrest and for some time thereafter, causing some uncertainty in defining K,;,. To determine whether or not this uncertainty can cause significant errors in measuring KI;,. measurements made under a variety of test conditions were compared. KI. was found to be independent of the manner in which it was measured. and the uncertainty in using a static analysis was far less than the material scatter. It is suggested that the invariance of the statically calculated KI;, may be a result of the tact that oscillations seen in the elastic portion of the specimen are not transmitted through the plastic zone to the crack tip. The importance of a proper treatment of damping in a dynamic analysis is also discussed.