The effect of the R value on the number of delay cycles following an overload

✍ Scribed by S. Ishihara; A.J. McEvily; T. Goshima; S. Nishino; M. Sato

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 691 KB
• Volume: 30
• Category: Article
• ISSN: 0142-1123
• DOI: 10.1016/j.ijfatigue.2008.02.011

✦ Synopsis

a b s t r a c t Compact tension (CT) specimens, 6 mm thick, of the aluminum alloy 6061-T6 were subjected to 100-300% overloads at R values ranging from 0.1 to 0.9. Both experimental and analytical results show that the delay phenomenon is found at all R values. For a given overload ratio, the number of delay cycles, N d , at high R values was found to be specimen-type dependent. In tests using compact specimens, N d increased with R, whereas in tests using center-cracked specimens N d decreased with R. Over the complete range of R values, the delay phenomenon is shown to be caused by overload-induced crack closure.