EFFECTS OF FREQUENCY, STRESS RISING TIME AND STRESS HOLD TIME ON CORROSION FATIGUE CRACK GROWTH BEHAVIOUR OF LOW ALLOY Cr-Mo STEEL.

For da/dN under 3. 5% NaCl solution in low alloy Cr-Mo steel, the experiment were carried out, stress frequency f being controled by stress rise time t//R and stress hold time t//H as well, in order to clear whether da/dN depends on cycle only, or on time only or on both cycle and time. From the results and the analysis, a new experimental formula was obtained for da/dN in terms of f, t//R or t//H non-linearly. A line of considerations as stochastic process is proposed for the significance of the equation of this type, and as a special case da/dN and da/dt in corrosion fatigue (t//H equals 0) are characterized in terms of frequency dependence.