Some fracture modes in metal fatigue

✍ Scribed by C.M. Gilmore; D.E. Macdonald; W.A. Wood

• Publisher: Elsevier Science
• Year: 1973
• Tongue: English
• Weight: 901 KB
• Volume: 5
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(73)90059-3

✦ Synopsis

Ah&act -This paper describes scanning electron-microscope studies made in an attempt to resolve current confusion in the literature about how fatigue cracks begin. It has been said that they normally grow by a Stage I process of shear, on the grounds that they form along slip bands, which are known to tend to directions of maximum shear. It is found that in fact cracks started by slip do not necessarily follow the Stage I shear rule, but may follow random paths; and that optimum condition for Stage I cracking is indeed absence of slip. Further, it is shown that much of the confusion disappears if a distinction is made between 'plastic' metals, in which cracking in particular conditions can be started by slip, and 'elastic' metals in which cracking is started rather by local inhomogeneous strains and internal stresses and may have little to do with slip.