花歯岩の腐食疲労き裂伝播挙動

抄録

Water content in a rock sample has a strong influence on the fatigue crack growth behavior. In order to investigate this effect, corrosion fatigue tests at room temperature were performed on granitic rock samples, containing various degree of saturation.Furthermore, mechanical fatigue crack growth rate in an inert environment was determined to evaluate the effect of water content more quantitatively.Corrosion fatigue crack growth rates can be represented by Paris' law as follows.
da/dN|_CF=D (ΔK) ^m (m=22.5).(1)
where D is a parametric constant depending on environment and frequency, ΔK stress intensity factor range and mconstantd etermined experimentally.Considering the effects of water content and mechanical variables, such as loading frequency and stress ratio, on cyclic crack growth rate, the following empirical relation was obtained.
da/dN|_CF=D (Sr, f) D'(R)(ΔK) ^m.(2)
where D is a function of loading frequency (f) and degree of water saturation (Sr) and D'is a function of stress ratio (R). Taking Walker's model into consideration, equation (2) can be rewritten in terms of effective stress intensity factor range (ΔK_eff).
da/dN|CF=D (Sr, f)(ΔK_eff) ^m.(3)
whereΔK_eff=K_max(1-R)ⁿ (n=0.1)
Mechanical fatigue crack growth rate in the inert environment, where a constant D in eq.(1) shows a constant value D₀ independent of loading frequency, was determined as follows.
da/dN|_inert=D₀ (ΔK_eff)^m (D₀=2.6×10^-7).(4)