The “twin-crack” model and the T-criterion in predicting dynamic instability for asymmetric cracks

✍ Scribed by P.S. Theocaris; N.P. Andrianopoulos; S.K. Kourkoulis

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 907 KB
• Volume: 43
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(92)90117-w

✦ Synopsis

The phenomenon of directional instability of running cracks is studied by means of a "twincrack" model. The running single crack tip is simulated by a cloud of microcracks under the form of hackles with random lengths and orientations, which, finally, are reduced into a flat front with two dominant microbranches at their corners. A suitable fracture criterion is applied in its double geometry in order to predict the future behaviour of this pattern. The predictions obtained agree well with existing experimental evidence concerning branching angles and give strong indications that other instability phenomena (such as curving, kinking and arrest) could be approached through the same model. It is finally concluded that directional instability is governed by two groups of factors, deterministic (macroscopic) and stochastic (microscopic), and, thus, the existence of sharp critical instability conditions seems not to be natural.