LNGタンカー用9%Ni鋼タンク材の疲労き裂伝ぱ特性

概要

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The authors carried out the experimental and analytical investigations for the purpose of finding out the method of estimating the fatigue crack propagation life and the increment of crack length due to fatigue crack propagation for the surface cracked 9% Ni-steel plate. In the first place, fatigue crack propagation tests were carried out on center through notched specimens of plate, forged, welded material, and for 4 kinds of surface notched specimens, similar tests were also conducted. From these test results, they cleaqred the following matters such as, law of fatigue crack propagation, surface crack length when surface crack was through the plate thickness, crack length when the crack length at front surface was nearly identical to one at back surface, the method to estimate the fatigue crack propagation of surface cracked, plate, etc. Next, using the above method, they investigated the fatigue crack propagation life and the increments of crack length due to fatigue crack propagation for three high stressed regions in spherical tank of LNG carriers.