Fatigue crack growth: mode I cycles with periodic mode II loading
2008 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 30, no 5, 931-941 p.Article in journal (Refereed) Published
The influence of periodic Mode II loading on Mode I fatigue crack growth is studied using a new type of loading device. The average rate of crack growth is found to be governed mainly by four parameters; Delta K-I and the Mode I R-ratio, the magnitude of the Mode II load and the Mode II period, M (M = number of Mode I load cycles per Mode II load). The Mode 11 load has to be large enough to create residual tangential displacements of the crack faces otherwise no effect occurs at all. Two mechanisms are found, Mode II-induced crack closure that reduces the crack propagation rate (long range) and a mechanism that increases the growth rate temporarily at every Mode I I load (short-range). For a specific Mode I load and Mode I I magnitude, it is possible to find a minimum crack growth rate for a certain Mode II period, M-opt. At high R-ratios the Mode II-induced closure mechanism disappears, but the temporary increase in growth rate at every Mode II load is still active. A semi-analytical model for the average crack growth rate during sequential Mode I and Mode II loading is presented.
Place, publisher, year, edition, pages
2008. Vol. 30, no 5, 931-941 p.
sequential mixed mode I, II loading, crack closure, fatigue crack growth
IdentifiersURN: urn:nbn:se:kth:diva-8983DOI: 10.1016/j.ijfatigue.2007.06.004ISI: 000254687400015ScopusID: 2-s2.0-38949215022OAI: oai:DiVA.org:kth-8983DiVA: diva2:14505
QC 20101004. Tidigare version publicerad som Report 400, KTH Solid Mechanics.2006-01-162006-01-162010-10-04Bibliographically approved