小弟最近读到某篇制造相关的期刊,但读到某一段真的是看不懂文意... 烦请版上强者为小弟解惑 内文如下: In the weld metal with lower strength, as in the case of GTAW joint, since the deformation and the yielding are mainly concentrated in the weld metal zone, the extension of the plastic zone is limited within the weld metal. As soon as the plastic zone reaches the fusion line, plasticity keeps on developing along the interface between the parent material and the weld metal[19]. The triaxial state of stress is high in the weld metal and the relaxation of this stress is poor. The crack driving force needed for crack extension is small, so the fracture toughness of the weld metal with lower strength is not high. On the other hand, if the strength of the weld metal is more or less equal to the base metal, as in the case of FSW joint, the plastic zone can easily extend into the parent material because the deformation and yielding occur in both weld metal and the base metal. The stress relaxation can easily take place in the crack tip region, so more crack driving force is needed for crack extension and the fracture resistance of the weld metal with higher strength is greater than that of the lower strength[20]. This is also one of the reasons for the better fatigue performance of the FSW joint. --

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