基于累积递增塑性变形的船体裂纹板断裂韧性研究

裂纹尖端张开位移（CTOD）是评估结构材料韧性以及分析低周疲劳破坏引起的裂纹扩展的重要参量。文章结合Dugdale模型，以裂纹尖端累积塑性应变为控制参量，提出了一个循环载荷下含裂纹船体板的CTOD计算模型；利用有限元法模拟了裂纹尖端累积塑性应变、平均应力、裂纹长度等相关因素影响；结合最小二乘法拟合出了基于累积塑性应变、平均应力比以及裂纹长度的两阶多项式。文中基于累积塑性应变的CTOD计算模型为正确评估循环载荷下船体板的累积塑性破坏提供了一种新途径。

Research on the Fracture Toughness for Ship Cracked Plates Based on the Accumulative Increment Plastic Deformation

The crack tip opening displacement (CTOD) is an important parameter to evaluate materi-al fracture toughness and analyze the crack propagation due to low-cycle fatigue damage. An analyt-ical model is presented to determine CTOD for the Ship cracked plates subjected to low-cyclic axial in-plane loadings. Combined with Dugdale’s model, the accumulation plastic deformation at the crack tips is used as controlling parameter to estimate cyclic CTOD for low-cycle failure analysis of the ship central-through cracked plates. The second order polynomial for the normalized CTOD defined as a function of the accumulative plastic strain, the ratio of mean stress to the yield stress, and the crack length is fitted by the least square method. The new accumulative plastic strain based on CTOD estimation presented in this paper provides a new way for low-cycle fatigue analysis, con-sidering accumulative plastic damage for central-through cracked plates under high cyclic loadings.