Avtomaticheskaya Svarka (Automatic Welding), #2, 2019, pp. 43-50
Methods of evaluation of increase of fatigue resistance in butt welded joints of low-carbon steels after high-frequency mechanical peening
V. A. Degtyarev
S. Pisarenko Institute for Problems of Strength of the NAS of Ukraine. 2 Timiryazevskaya Str., 01014, Kyiv, Ukraine
There was investigated an effect of modes of high-frequency mechanical peening on increase of fatigue resistance of butt welded joints of steel ST3sp (killed). Different technology of sample preparation for investigation allowed determining that quantitative contribution in rise of fatigue limit of welded joints, residual compression stresses, deformation hardening of surface layer of a groove formed after peening of narrow zone of weld fusion with base metal, and change of stress concentration after mechanical peening makes 57, 37 and 6 %, respectively. It is shown that there is a correlation between the groove depth and depth of plastically deformed layer of material. The procedure was proposed for determination of the fatigue limits of butt welded joints after different modes of peening on groove depth and plastically deformed layer of material, using the experimental data of microhardness measurement as well as the change of amplitude of osculation of working tool in the investigated range. A depth of groove was determined depending on speed of high-frequency mechanical peening and amplitude of working tool oscillation as well as change of sample fatigue limit due to different technology of their manufacture. It is shown that increase of peening speed independent on working tool osculation amplitude promotes decrease of efficiency of improvement of welded joint fatigue resistance and at 0.4 m/min speed the fatigue limit from deformation hardening and total effect of all factors typical for high-frequency mechanical peening rises by 11 and 26 %, respectively. 14 Ref., 3 Tabl., 7 Fig.
welded joint, fatigue limit, groove depth, speed of high-frequency mechanical peening, plastically deformed layer, microhardness
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