高强度结构钢焊接节点断裂性能应变时效敏感性研究

Until the repair process of the structure commence, steel of partially damaged high strength steel (HSS) structures would become worse toughness because of strain ageing. Strain ageing effects of steel may significantly influence the structure response in terms of seismic behavior. And the post-earthquake indicate that fracture behavior of beam-to-column connections directly affect the safety of steel structures. Therefore, influence of strain ageing on fracture behavior of welded connections using HSS would be the key question for application of HSS structures in seismic region. In this project, based on the mechanical behavior test results of coupon specimens, effects of strain ageing on HSS and weld material will be analyzed, and constitutive model of materials affected by strain ageing will be established. In addition, based on the tensile test results and finite element analysis(FEA) of notched specimens, parameters of micromechanics-based fracture models for HSS and weld material will be calibrated, and then micromechanics-based fracture models for materials affected by strain ageing will be established. Finally, local welded specimens of beam-to-column connections using HSS will be tested and analyzed, to verify the applicability of micromechanics-based fracture models for connections affected by strain ageing, and obtain the strain ageing effect on fracture behavior of welded connections using HSS. The expected achievement will make researches on strain ageing go further, and provide data and theoretic foundation. It will play an important role in promoting the application of HSS structures.

对于可修复的部分损伤高强钢结构，其钢材在等待修复期间因应变时效效应而脆化，将显著影响修复后高强钢结构的整体抗震性能。过去地震经验表明，梁柱节点的断裂性能直接影响钢结构整体安全性，因此应变时效对高强钢焊接节点断裂性能的影响，是高强钢结构在抗震区应用必将面临的关键问题。本项目采用标准材性试件力学性能试验，分析应变时效对高强钢及其焊缝材料基本力学性能的影响，建立应变时效影响下的材料本构模型；采用平滑缺口试件拉伸试验与有限元模拟，标定各材料微观断裂力学模型所需参数，基于微观机理建立考虑应变时效影响的高强钢断裂力学模型；采用高强钢节点局部焊接试件试验与有限元模拟，验证微观力学模型对应变时效影响节点的断裂预测适用性，并分析高强钢焊接节点断裂性能应变时效敏感性。本项目将应变时效研究从材料层面向结构层面推进，研究成果为完善高强钢焊接节点抗断设计提供数据积累和理论依据，对促进高强钢结构的应用具有重要意义。

本研究在国家自然科学基金（青年）项目“高强度结构钢焊接节点断裂性能应变时效敏感性研究51908306”的资助下进行为期3年的研究工作，基本完成申请书预定的研究任务。研究成果获中国钢结构协会科学技术奖一等奖1项、山东省高校优秀科研成果一等奖1项，申请发明专利1项，成果为两部行业标准的制定提供依据，发表论文相关论文4篇，其中SCI检索3篇，研究成果为应变时效对各级别建筑结构钢母材、热影响区及焊缝金属宏观力学性能和微观力学机理影响方面积累大量基础数据，为受损节点及结构在进行评估时考虑应变时效对修复后受力性能的影响提供依据，对完善受损高强钢焊接节点抗断裂设计与评估、提高受损高性能钢结构建筑安全性评估准确性具有重要意义。项目主要的研究内容及创新点如下：（1）较为全面的掌握高性能结构钢材、热影响区及焊缝熔敷金属材料的基本力学性能随应变时效程度变化的趋势；（2）建立了考虑应变时效影响的各级别高性能钢材及其焊接材料应力-应变本构模型；（3）研究了经不同应变时效影响的结构钢母材、热影响区及焊缝熔敷金属的微观机理变化规律，并标定了各材料的微观断裂力学模型特征参数；（4）通过ABAQUS的用户子程序UVARM，初步建立考虑应变时效影响的高性能钢及其焊缝材料微观断裂预测模型；（5）提出了钢结构应变时效影响程度声发射无损检测方法，并通过建立Q460C钢材声发射信号特征值、时频特征与应变时效之间的关系初步验证该方法可行性；（6）进行了经应变时效影响的受损热轧H型钢梁受弯承载力试验与有限元研究，初步将应变时效影响研究由“材料”层面延伸至“构件”层面。上述研究成果为在役的受损钢结构构件、节点以及结构整体力学性能评估以及修复后安全性评估提供试验和理论依据，有利于进一步推进高强钢结构建筑在地震区的应用。