基于临界距离理论的弧形切口疲劳寿命研究

陈卓异; 杨宇; 李传习; 曾振海; 曾剑波

doi:10.13206/j.gjgs21062201

基于临界距离理论的弧形切口疲劳寿命研究

doi: 10.13206/j.gjgs21062201

长沙理工大学桥梁工程安全控制教育部重点实验室, 长沙 410114

基金项目:

国家自然科学基金项目（51708047，51778069）；湖南省自然科学基金项目（2019JJ50670）；重点学科创新性项目（18ZDXK11）；湖南省教育厅优秀青年项目（19B013）；湖南省研究生科研创新项目（CX20200847）。

详细信息

作者简介:
陈卓异,男,1985年出生,博士,副教授。

通讯作者:
李传习,男,1963年出生,博士,教授,lichuanxi2@163.com。

中图分类号: U441.4
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- 被引次数: 0
出版历程
- 收稿日期: 2021-06-22
- 网络出版日期: 2022-01-11

Fatigue Life Study for Floorbeam Cutout Using the Theory of Critical Distances

Key Laboratory of Bridge Engineering Safety Control by Department of Education, Changsha University of Science & Technology, Changsha 410114, China

摘要

摘要: 正交异性钢桥面板因其自重轻、极限承载力大、适用范围广等优点而广泛应用于土木工程，但其疲劳问题严重，钢箱梁横隔板弧形切口的抗疲劳设计仍是难点。为有效预测此典型疲劳易损细节的疲劳寿命，采用ABAQUS有限元分析软件，建立了三种弧形切口疲劳试件的有限元简化模型，通过对三种不同弧形切口半径的试件模型在拉伸荷载50 kN下的有限元求解，分别得到各自主应力云图。可知：切口处第一主应力随切口半径增大而减小，半径从10 mm增至20 mm时，第一主应力从319.8 MPa减至253.7 MPa，减幅66.1 MPa；半径从20 mm增至30 mm时，第一主应力从253.7 MPa减至225.6 MPa，减幅28.1 MPa，较之前变平缓。再引入临界距离理论分析了弧形切口应力集中区域的特征应力，采用点法与线法进行特征应力计算。利用ABAQUS自最大主应力峰值处按最高应力梯度方向设置路径，提取各点第一主应力及其所在点距最大主应力峰值的距离。在热点路径上，最大主应力与距离呈反比关系；在1.2倍临界距离范围内，切口半径越小，应力水平越高；在2倍临界距离以外的区域，切口半径20 mm与切口半径30 mm的最大主应力曲线呈靠拢趋势，表明此时切口已不再是影响应力水平的关键因素，从而得到了临界距离、裂纹扩展门槛值等关键参数。结合材料疲劳极限与FE-safe寿命结果建立了三种切口构件的疲劳寿命预测模型，开展了横隔板弧形切口节段试件的疲劳试验，验证了简化模型的准确性，研究了不同切口半径对试件疲劳寿命影响的规律。
结果表明：1）钢箱梁横隔板弧形切口处基于点法的应力预测值比线法的应力预测值高7%~13%，点法的疲劳寿命预测值比线法的疲劳寿命预测值基本低50%以上；点法预测值比线法预测值更加保守；2）所提出的钢箱梁横隔板弧形切口疲劳预测模型精度较高，与节段模型疲劳试验结果误差在20%以内；3）无论采用点法还是线法，计算所得的特征应力都随切口半径增大而减小，疲劳寿命都随切口半径增大而增长，钢箱梁横隔板弧形切口设计时，适当提高切口半径有利于结构疲劳寿命的提升；4）由于疲劳试件采用的都是光滑的弧形切口试件，对于含初始缺陷的构件，其采用临界距离理论评估疲劳寿命的计算模型有待进一步研究。
- 正交异性桥面板 /
- 钢箱梁 /
- 横隔板 /
- 临界距离理论 /
- 弧形切口 /
- 疲劳寿命预测
Abstract: Orthotropic steel bridge deck is widely used in civil engineering because of its light weight, high ultimate bearing capacity and wide application range. But its fatigue problem is serious. Steel box girder of diaphragm plate arc incision anti-fatigue design is still a difficulty, to effectively predict the fatigue life of the typical fatigue vulnerability details, using ABAQUS finite element analysis software, set up three kinds of fatigue specimen the simplified finite element model of arc incision, through three different radius arc incision specimen under tensile load of 50 kN finite element model, the independent stress nephograms were obtained respectively. It can be seen that the first principal stress at the notch decreases with the increase of the notch radius. When the radius increases from 10 mm to 20 mm, the first principal stress decreases from 319.8 MPa to 253.7 MPa, with a reduction of 66.1 MPa. When the radius increases from 20 mm to 30 mm, the first principal stress decreases from 253.7 MPa to 225.6 MPa, with a decrease of 28.1 MPa, which becomes gentle compared with before. Then the critical distance theory is introduced to analyze the characteristic stress in the stress concentration area of curved notch, and the point method and line method are used to calculate the characteristic stress. ABAQUS was used to set the path from the maximum principal stress peak according to the direction of the highest stress gradient to extract the first principal stress at each point and the distance between the point and the maximum principal stress peak. On the hot spot path, the maximum principal stress is inversely proportional to the distance. Within the critical distance of 1.2 times, the smaller the notch radius, the higher the stress level; In the region beyond 2 times the critical distance, the maximum principal stress curves of the notch radius of 20 mm and 30 mm show a close trend, indicating that the notch is no longer the key factor affecting the stress level. Thus, key parameters such as the critical distance and the threshold value of crack growth are obtained. Combined with the results of fatigue limit and FE-safe life, the fatigue life prediction models of three notched members were established. The accuracy of the simplified model was verified by the fatigue tests of the diaphragmcurved notch segments. The influence of different notch radius on the fatigue life of the specimens was studied.
The results show that:1) the predicted stress value based on the point method is 7%~13% higher than that based on the line method, and the predicted fatigue life value based on the point method is more than 50% lower than that based on the line method at the arc notch of the steel box girder diaphragm. The point method is more conservative than the line method; 2) the fatigue prediction model of the steel box girder diaphragm arc notch proposed in this paper has a high accuracy, and the error between it and the fatigue test results of the section model is basically within the range of 20%; 3) no matter using point method or line method, the calculated characteristic stress decreases with the increase of notch radius, the fatigue life increases with the increase of notch radius, the fatigue life of steel box girders can be improved by increasing the radius of the curved notch; 4) the fatigue specimens used in this paper are all smooth curved notch specimens. For the components with initial defects, the calculation model of fatigue life evaluation using critical distance theory needs to be further studied.
- orthotropic steel bridge deck /
- steel box girder /
- transverse diaphragm /
- the theory of critical distances /
- floorbeam cutout /
- fatigue life prediction

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参考文献(16)

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