Fatigue threshold and low-rate crack propagation properties for structural steels in 3 Pct sodium chloride aqueous solution |
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Authors: | Saburo Matsuoka Hiroyuki Masuda Masuo Shimodaira |
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Affiliation: | (1) Environmental Performance Division, Japan;(2) Failure Physics Division, National Research Institute for Metals, 2-3-12 Nakameguro, 153 Meguro-ku, Tokyo, Japan |
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Abstract: | The fatigue threshold and low-rate crack propagation properties for a carbon steel, two high-strength steels, and two stainless
steels were investigated in a 3 pct sodium chloride aqueous solution at frequencies between 0.03 and 30 Hz. Tests were conducted
in a manner designed to avoid crack closure. Under freely corroding conditions, the effective values of the threshold stress
intensity factor range, ΔKth,eff, were lower than in air for all of the steels. In particular, the ΔKth,eff values for the carbon and high-strength steels were almost equal to the theoretical ΔKth value of about 1 MPa m1/2 calculated on the basis of the dislocation emission from the crack tip. At a given ΔK level higher than the threshold, the
fatigue crack propagation rates accelerated with decreasing frequency for all of the steels. Under cathodic protection, the
threshold and fatigue crack propagation properties were coincident with those in air regardless of material and frequency.
The observed fatigue crack propagation behavior in a 3 pct NaCl solution was closely related to the corrosion reaction of
the bare surface formed at the crack tip during each loading cycle. |
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