ISSN: 1945-7553
Page Count: 6

Detecting Overload from Strain Information during Fatigue Crack Propagation under Negative Stress Ratio

Makabe, Chobin
Professor, Graduate Student, and Lecturer, University of the Ryukyus, 1 Nishihara,Okinawa

Purnowidodo, Anindito
Professor, Graduate Student, and Lecturer, University of the Ryukyus, 1 Nishihara,Okinawa

Sueyoshi, Toshiyasu
Professor, Graduate Student, and Lecturer, University of the Ryukyus, 1 Nishihara,Okinawa

Utsunomiya, Takao
Professor, Shibaura Institute of Technology, Tokyo,

(Received 6 February 2003; accepted 9 July 2003)

Abstract

In the present study, a detection method of an overload application during stress cycles under constant amplitude was investigated. Also, the effect of the tensile overload was shown at three stress ratios: R = 0, -1, and -1.5, to understand the effects of R on crack propagation after an overload. At the baseline of R = 0, after the overload, retardation in the crack propagation was observed, and the crack growth rate decreased. However, in the case of R = -1.5, the fatigue crack growth rate actually accelerated after the tensile overload. The detection of that crack propagation behavior was attempted through the information of the strain waveform h; h = ε_y + 1.2λ_x, where ε_x and ε_y are the local strains at the specimen axis, and λ is the strain range ratio Δε_y/Δε_x. The waveform shape of h was changed after the overloading. Also, the application of the overload could be detected by the variation of the strain range ratio λ. Especially, the present method is useful for cases of the crack propagation stage under negative R conditions.

Keywords:
fatigue, crack propagation, overload, stress ratio, strain waveform

Paper ID: JTE11853
DOI: 10.1520/JTE11853
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