﻿ 东南大学学报(自然科学版)

(西安建筑科技大学土木工程学院, 西安 710000)

Fracture property degradation mechanism and degradation law of corroded steel plates with central cracks under static tension load
Xu Shanhua，Zhang Haijiang，Zhang Zhexun，Wen Yaxin
(School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710000, China)

The corroded steel plates with central cracks were prepared to investigate the fracture property degradation mechanism and degradation law of corroded steel plates using the theory and parameters of fracture mechanics. An empirical model for nominal fracture toughness degradation of corroded steel was established. The results show that corrosion can increase the amplitude of the stress intensity factor(SIF), the intensity of the crack tip field and the displacement field, thus accelerating the propagation of existing cracks. For the non-corrosion model and the general-corrosion model, the SIF value at the crack tip decreases gradually from the model interior to the external surface in the thickness direction. For the pitting-corrosion model, the SIF value at the crack tip increases gradually from the model interior to the pit bottom in the thickness direction. Corrosion makes the J-load curves reach the critical value faster, thus leading to the premature fracture of steel plates earlier. The results of the empirical model of fracture toughness degradation agrees well with those of the fracture tests.

1 断裂试验

2 考虑表面锈蚀损伤的有限元断裂模型

σ=kεn(1)

3 弹性阶段分析

K=(JE/(1-v2))1/2(2)

4 弹塑性阶段分析

J=∫Γ(Wdy-Ti(∂ui)/(∂x)ds)(3)

5 断裂性能退化规律分析

J=Jc(4)

βJ=Jc(5)

γ=1/(β)(6)

J=γJc(7)

γ=γ1γ2(8)

γ1和γ2的计算结果见表2.

γ1={1-3.992(Dave)/(T0)0≤(Dave)/(T0)≤0.1

-0.042+1.327exp(-7.248(Dave)/(T0))

(Dave)/(T0)>0.1(9)

γ2={1-1.424 4Dpit

0≤Dpit≤0.25 mm

0.735-0.069exp(1.112Dpit)

Dpit>0.25 mm(10)

6 结论

1)锈蚀会降低钢板的断裂荷载和断裂位移,使钢板的抗断裂性能发生严重退化.

2)通过对应力强度因子幅值和分布特征的分析可知,锈蚀将增大裂纹扩展的推动力,加速既有裂纹的扩展.点蚀使应力强度因子沿厚度方向的最大值从中心转移至外表面.

3)通过对J积分-荷载曲线的分析可知,锈蚀将导致J积分值更快地达到其临界值,从而导致钢板断裂提前发生.

4)根据模拟结果建立了锈蚀钢材残余名义断裂韧度退化的经验模型.结果表明,锈蚀大大降低了钢材的残余名义断裂韧度,其剩余值与均匀锈蚀深度和点蚀深度有关.