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为提高镁合金焊接接头的超高周疲劳寿命及其安全可靠性,采用机械打磨除去MB8镁合金焊接接头余高,利用超声疲劳试验机来探究MB8镁合金焊接接头超高周疲劳性能。结果表明:MB8镁合金焊接接头的S-N曲线在2.0×10~8周左右时会出现平台,说明其存在疲劳极限;当疲劳寿命小于2.0×10~8周,S-N曲线呈连续下降趋势,疲劳寿命随着载荷的降低而增加;疲劳失效试样都断裂在试样的中间焊缝部位,疲劳断口可以分成疲劳源区,柱状晶扩展区、过渡扩展区、粗晶扩展区、瞬断区5个区域。
In order to improve the ultrahigh cycle fatigue life and safety of the welded joint of magnesium alloy, mechanical grinding was used to remove the excess height of the welded joint of MB8 magnesium alloy. The ultrasonic fatigue testing machine was used to explore the ultrahigh cycle fatigue behavior of MB8 magnesium alloy welded joint. The results show that the SN curve of MB8 magnesium alloy welded joint will appear at 2.0 × 10-8 weeks, which shows the existence of fatigue limit. When the fatigue life is less than 2.0 × 10-8 weeks, the SN curve shows a continuous downward trend and the fatigue life With the decrease of load, fatigue failure specimens are all fractured in the middle part of the weld. The fatigue fracture can be divided into five zones: fatigue source zone, columnar zone expansion zone, transitional expansion zone, coarse grain expansion zone and instantaneous zone area.