突合せ溶接継手の疲れき裂発生点に関する一考察

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The pulsating tensile fatigue tests have been carried out on the butt welded specimens using a Vibrophore fatigue testing machine. The microscopic examintion of these specimens has revealed the presence of small notches or grooves which have a sharp root radius and exist mostly at the periphery of the deposited metal near the welded toe. In any case, fatigue crack is initiated at these notches which are exceedingly small, not more than 0.03mm in root radius and less than 0.1mm in depth. In case of fatigue cracking at the periphery of the deposited metal, the smaller the root radius and the deeper the notch, the shorter becomes the fatigue life. Therefore fatigue strength increases as the periphery of the deposited metal becomes very smooth and the root radius of the nocthes becomes large, even if an undercut may be present. The fact that the fatigue strengths of welded materials with different static strengths show nearly similar values can be explained by the presence of such a sharp notch and not by the marcoscopic notch effect. Besides the marcoscopic stress concentration due to the geometrical effect of the welded toe, another microscopic stress concentration caused by these small notches has been confirmed, and such notches influence the fatigue strength of welded specimen. A conspicuous improvement of the fatigue strength of the welded joints can be attained if the welded toe and the periphery of the deposited metal in the vicinity of the toe are smoothed by some method of welding or post treatment after welding.
社団法人溶接学会の論文
1968-11-25

突合せ溶接継手の疲れき裂発生点に関する一考察

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