This paper proposes an estimation method for crack tip opening displacement (CTOD) in laser welds. The theoretical model for CTOD estimation developed by Dugdale and Bilby et al. (DBCS model) was used for laser-welded plates. The yield stress of the laser weld metal and narrow hard zone width affected the CTOD, and the correction of yield stress by using the DBCS model to obtain a suitable CTOD estimation was investigated. To apply the DBCS model to CTOD estimation for laser welds, an equivalent yield stress concept was proposed. The equivalent yield stress was affected by the strength mismatch ratio and hard zone width, because the yield stress of the laser weld metal decreases with the constraint loss caused by the plastic deformation that occurred in the base metal. The predicted CTOD from the value of applied load obtained using the proposed estimation method agrees well with experimental critical CTODs for laser welds of both 780 and 520 MPa class structural steel.

中文翻译：

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激光焊缝CTOD估算方法的数值研究

本文提出了一种激光焊接裂纹尖端开口位移（CTOD）的估算方法。Dugdale和Bilby等人开发的CTOD估算理论模型。（DBCS模型）用于激光焊接板。激光焊接金属的屈服应力和较窄的硬质区宽度影响CTOD，并研究了使用DBCS模型校正屈服应力以获得合适的CTOD估计值的方法。为了将DBCS模型应用于激光焊接的CTOD估算，提出了等效的屈服应力概念。当量屈服应力受强度失配率和硬区宽度的影响，因为激光焊接金属的屈服应力随着母材中塑性变形引起的约束损耗而降低。