Q345qD对接焊缝疲劳性能及断裂机理试验研究  

EXPERIMENTAL RESEARCH ON FATIGUE PERFORMANCE AND FRACTURE MECHANISM OF Q345QD BUTT WELDS

作　　者：贾单锋 王元清[2] 崔佳[1] 廖小伟[2] 顾浩洋 

机构地区：[1]重庆大学土木工程学院,重庆400045 [2]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,北京100084

出　　处：《工业建筑》2017年第11期175-180,共6页Industrial Construction

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)

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。Standard tensile coupon specimens and hourglass specimens were used in tensile tests and axial fatigue tests respectively,aiming to implement fatigue life assessment of weld details in bridge structure.The safe fatigue life curves were obtained owing to the introduction of survival rate and confidence.In consideration of the large discrete of butt welds fatigue life,further researches on fracture microtopography were conducted to analyze the microscopic mechanism of premature fatigue crack initiation in butt welds.The results showed that Q345qD butt welds performed well in fatigue tests,and the fatigue life increased observably with the stress level decreased,and the fitting formula about the variations of life with stress levels was also obtained.For this batch,the fatigue strength far exceeded the values of design code,and the constant amplitude fatigue limit was in the vicinity of Smax= 380 MPa.Welding heat input had a greater impact on the welds,and the heat affected zone the hardness in heat affected zone fluctuates obviously.The inhomogeneity of microstructure and welding defects would lead to premature fatigue fracture at lower stress levels.

关 键 词：桥梁钢 对接焊缝 疲劳性能 安全疲劳寿命曲线 断裂机理 

分 类 号：U441[建筑科学—桥梁与隧道工程] U445.583[交通运输工程—道路与铁道工程]