Q690高强钢及其焊接构件的疲劳性能

陈韡; 钟国辉

doi:10.13206/j.gjgS24050104

Q690高强钢及其焊接构件的疲劳性能

doi: 10.13206/j.gjgS24050104

陈韡^1,2,
钟国辉^1,2, ,

1. 香港理工大学土木与环境工程学院, 香港 999077;
2. 香港理工大学国家钢结构工程技术研究中心香港分中心, 香港 999077

基金项目:

国家钢结构工程技术研究中心香港分中心项目(1-BBY3)。

详细信息

作者简介:
陈韡,硕士研究生,主要从事钢结构研究。

通讯作者:
钟国辉,博士,教授,主要从事钢结构与钢-混凝土组合结构研究,kwok-fai.chung@polyu.edu.hk。

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出版历程
- 收稿日期: 2024-05-01
- 网络出版日期: 2024-06-22
- 刊出日期: 2024-05-22

Fatigue Performance Study on Q690 High Strength Steels and Their Welded Sections

Wei Chen^1,2,
Kwok-Fai Chung^{1,2
, ,}

1. Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong 999077, China;
2. Chinese National Engineering Research Centre for Steel Construction (Hong Kong Branch), The Hong Kong Polytechnic University, Hong Kong 999077, China

摘要

摘要: 高强钢指屈服强度f_y不小于460 MPa的钢材,因其良好的材料性能已被逐步应用于建筑和桥梁中。与普通强度钢材相比,高强钢具有更高的屈服强度,可以减小构件的尺寸,且较薄的钢板厚度可以减少焊接工作量、提高焊接质量,从而避免厚板带来的焊接问题。疲劳损伤一直以来是桥梁结构最为关键的服役问题之一,在国内外现行的结构设计规范中并没有包含针对高强钢材疲劳性能的设计标准。对Q690高强钢及其焊接件的疲劳性能进行了系统性的试验研究,确定Q690高强钢及其焊后的疲劳强度,以推进Q690高强钢在实际工程中的应用。首先对Q690高强钢及其焊接件的标准试件进行单调拉伸试验,确定其材料性能,在Q690焊接件进行试验前对试件进行了腐蚀处理,目的是更为直观地在试验中观察到焊材、热影响区和母材的分布,试验确定颈缩发生的位置为热影响区。根据单调拉伸试验得到的材料力学性能确定了多级疲劳荷载,并对Q690高强钢及焊接光滑圆棒试件进行系列高周-低应变疲劳试验,确定了Q690高强钢母材及其焊接试件的疲劳寿命,并根据试验值拟合出疲劳曲线(S-N曲线)。疲劳试验得到Q690焊接件的疲劳极限为420.0 MPa,Q690母材的疲劳极限为668.8 MPa,结果表明Q690高强钢焊后疲劳极限有明显降低,但Q690高强钢母材及其焊接试件的疲劳极限均远远高于欧洲规范的设计值(母材:118 MPa,焊接件:82.5 MPa)。对Q690焊接试件进行了硬度试验,确定其沿纵向的硬度分布,发现焊材区的硬度最高约为328 HV,在热影响区有明显的软化现象,硬度为240 HV,说明Q690高强钢焊后硬度差异较大。对疲劳破坏后的Q690焊接件断口试件进行了腐蚀试验,发现疲劳裂纹起源于焊材区而非热影响区。并且对断口试件进行了扫描式电子显微镜观察,在疲劳断面发现非金属夹杂物。根据电镜观察的结果,分析了疲劳断口的微观现象,确定疲劳裂纹源及扩展过程,得到初始缺陷是影响Q690焊接件疲劳性能关键因素的结论。
- 高强钢 /
- 焊接接头 /
- 疲劳性能
Abstract: High strength steel with nominal yield strength, f_y, no smaller than 460 MPa has been progressively applied in buildings and bridges due to its good material properties. Compared with normal strength steel, high strength steels have higher yield strength which may reduce the size and dimension of members. In addition, the thinner steel plates may help avoid welding problems associated with thick steel plates as reducing the amount of welding work and improving the welding quality. Fatigue damage is one of the most critical service problems of steel bridge structures. There is no special design standard for fatigue performance of high strength steels in the current design code. This paper presents an experimental investigation on fatigue performance of Q690 high strength steels and their welded sections to determine the fatigue strength, so as to promoto the application of Q690 high strength steel in practical engineering. The monotonic tensile tests were carried out on Q690 high strength steels and their welded sections to examine the material properties. The welded section was etched before test to distinguish the position of base metal, heat affected zone and welded metal during testing, and determined the position of necking was heat affected zone. The various applied loadings of fatigue tests were determined according to the mechanical properties examined in the tensile test, and a series of high-cycle-low-strain cyclic tests on smooth cylindrical coupons had been conducted to determine the S-N curves for Q690 high strength steels and their welded sections. The fatigue limit of Q690 welded sections is 420 MPa, and that of base plate is 668. 8 MPa. It means that the fatigue performance of Q690 welded sections is worse than that of Q690 base plate, while the fatigue resistance of both the Q690 base plate and their welded sections are significantly larger than those given in Eurocode (base plate: 118 MPa, welded section: 82.5 MPa). The hardness test was conducted on the Q690 welded section to determine its hardness distribution along the longitudinal direction. It is found that the weld metal exhibits the larger hardness value as 328 HV, while the softening was identified in the heat affected zone with a hardness of 240 HV, which indicated that the hardness distribution of Q690 welded section is uneven and the difference is significant. Based on the results of etching tests and SEM observations on the fracture surfaces under fatigue loadings, it is found that the crack initiated at the fusion zone rather than the heat affected zone. What’s more, non-metallic inclusions have been identified in the fracture surfaces of Q690 welded sections, it means that the initial imperfections may be a critical parameter affecting the fatigue performance of Q690 welded sections.
- high strength steel /
- welded section /
- fatigue performance

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参考文献(10)

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