Examination of fatigue crack driving force parameter
Most of the previous parameters that utilized as a crack driving force were established in modifying the parameter Kop in Elber's effective SIF range ΔKeff(=Kmax−Kop). However, the parameters that replaced the traditional parameter Kop were based on different measurements or theoretical calculations, so it is difficult to distinguish their differences. This paper focuses on the physical meaning of compliance changes caused by plastic deformation at the crack tip; the tests were carried out under different amplitude loading for structural steel. Based on these test results, differences of several parameter ΔKeff in literature are analysed and an improved two-parameter driving force ΔKdrive(=(Kmax)n(ΔK∧)1-n) has been proposed. Experimental data for several different types of materials taken from literature were used in the analyses. Presented results indicate that the ΔKdrive parameter was equally effective or better than ΔK(=Kmax−Kmin), ΔKeff(=Kmax−Kop) and ΔK*(= (Kmax)α(ΔK+)1−α) in correlating and predicting the R-ratio effects on fatigue crack growth rate.
Document Type: Research Article
Affiliations: 1: College of Mechanical Engineering, Zhejiang University of Technology, Zhaohui District No. 6, Hangzhou, Zhejiang 310032, China 2: Department of Structural Engineering, Faculty of Engineering, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki, 852-8521, Japan
Publication date: 01 September 2008