Corrosion Fatigue Crack Growth under Stress Intensity Factor in Steel.

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Behavior of fatigue crack in 3% salt water is experimentally examined under the condition of controlled stress intensity factor as well as constant load a amplitude. The emphasis is placed on the effects of crack opening load, frequency and test temperature on the crack growth rate.The results obtained are summaraized as folloes;1) Since there is notable effect of wedge action due to the corrosion products on the crack closure, the influence of corrosion of the fatigue crack growth can be seen in much better fashion with the diagram of the crack growth rate da/dN vs. the effective stress internsity factor range than that of da/dN vs. the stress intensity factor range.2) As the stress ratio increase, the wedge action of the corrosion product decreases and the effective stress intensity factor range approaches to the nomonal stress intensity factor range.3) Performing tess under several combinations of load cycle frequencies and water temperatures, it is found that the growth rates in 3% salt water can be almost seven times as large as those in air for some cases. Making use of the above an accelerated test may become possible.