Q345qD对接焊缝疲劳性能及断裂机理试验研究

发布时间：2018-05-26 00:02

本文选题：桥梁钢 + 对接焊缝　；参考：《工业建筑》2017年11期

【摘要】：为了对钢桥焊接细节进行疲劳寿命评估,分别采用标准圆棒试件和沙漏型光滑试件进行静力拉伸试验和成组轴向拉伸疲劳试验,引入存活率和置信度得到了具有概率水平保证的安全疲劳寿命曲线,并针对焊接接头疲劳寿命离散性较大的现象,进行微观层面的硬度测试和疲劳断口电镜扫描试验,研究焊缝试件过早萌生疲劳裂纹的微观机理。试验结果表明:Q345qD对接焊缝的疲劳性能较好,随应力水平下降疲劳寿命显著提高,并给出了寿命随应力水平变化的拟合式;本批次Q345qD对接焊缝疲劳强度远远超过相同构造的规范取值,持久疲劳极限在S_(max)=260 MPa附近;焊接热输入对焊缝组织有较大影响,热影响区硬度波动明显,组织不均匀和焊接缺陷是导致低应力水平过早疲劳断裂的主要原因。
[Abstract]:In order to evaluate the fatigue life of steel bridge welding details, the static tensile test and group axial tensile fatigue test were carried out using standard round bar specimen and hourglass smooth specimen, respectively. The safety fatigue life curve with probability level is obtained by introducing the survival rate and confidence degree. The microhardness test and the fatigue fracture electron microscope scanning test are carried out in view of the large dispersion of fatigue life of welded joints. The microscopic mechanism of premature initiation of fatigue cracks in weld specimens was studied. The test results show that the fatigue performance of the butt weld seam of: Q345qD is better, and the fatigue life of the butt weld decreases significantly with the stress level, and the fitting formula of the fatigue life with the change of the stress level is given. The fatigue strength of the Q345qD butt weld is far higher than the code of the same structure, the durable fatigue limit is near S_(max)=260 MPa, the welding heat input has a great influence on the weld microstructure, and the hardness of the HAZ fluctuates obviously. The unevenness of microstructure and welding defects are the main causes of premature fatigue fracture at low stress level.
【作者单位】：重庆大学土木工程学院;清华大学土木工程系土木工程安全与耐久教育部重点实验室;
【基金】：国家自然科学基金项目(51378289);国家自然科学基金项目(51678339) 高等学校博士学科点专项科研基金项目(20130002110085)
【分类号】：U441;U445.583

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