项目名称： 考虑极低周疲劳效应的焊接钢材延性断裂模型及评价分析方法研究

项目编号： No.51508205

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 建筑环境与结构工程学科

项目作者： 康澜

作者单位： 华南理工大学

项目金额： 20万元

中文摘要： 极低周疲劳导致的延性断裂是厚壁钢结构的主要破坏形式之一，然而目前对其损伤机理认识尚不充分，还没有统一有效的评价分析方法。本项目拟通过往复荷载试验和扫描电镜分析，探索往复荷载参数对钢材延性断裂性能的影响规律；基于微观塑性损伤理论和前期研发的单调拉伸条件下的三阶段-两参数延性断裂模型，建立能够准确预测钢材在往复荷载条件下延性裂缝起裂、扩展以及最后破坏的全过程数值模型；采用焊缝以及热影响区的缺口断裂试验和有限元数值模拟分析，掌握焊缝和热影响区的往复延性断裂性能，并验证数值模型的可信度。本研究拟实现耦合延性断裂模型从单调拉伸条件到往复荷载条件的扩展，对阐明焊接钢结构在极低周疲劳作用下的破坏规律具有重要科学意义，为准确高效预测焊接钢结构大震过程中的往复延性断裂性能提供科学依据。

中文关键词： 焊接钢材；延性断裂模型；极低周疲劳；往复荷载；评价方法

英文摘要： Ductile fracture due to extremely low cycle fatigue is one of main failure modes for thick-walled welded steel structures. However, its damage mechanism is not completely investigated, and an effective and unified evaluation method is not developed until now. Firstly, due to the cyclic ductile fracture tests and observation with scanning electron micrograph, the effects of cyclic load parameters on ductile fracture behavior of structural steels are investigated. Secondly, a cyclic ductile fracture model is presented based on micro-plasticity damage theory and three-stage and two-parameter ductile fracture model under monotonic loading, which is proposed in the applicant's previous study. Through this model, ductile crack initiation, propagation and final failure under extremely low cycle fatigue loading can be simulated effectively and accurately. Besides, the ductile fracture tests of specimens notched in weldment or heat affected zone (HAZ) and finite element analysis for these tests are carried out, in order to investigate the cyclic ductile fracture behavior of weld and HAZ, and to demonstrate the capability and feasibility of the proposed model to predict ductile fracture under cyclic loading. This study extends the ductile fracture model from monotonic loading to extremely low cycle fatigue loading, and is useful for developing fracture-resistant design provisions and for evaluating structural performance under extreme loads such as strong earthquakes, especially for the thick-walled welded steel structures.

英文关键词： welded steel;ductile fracture model;extremely low cycle fatigue;cyclic loading;evaluation method