高强钢管节点疲劳累积损伤过程分析及疲劳性能研究

Concerning the difference in material behavior between low strength steel and high strength steel and little ready information on the fatigue behavior of CHS (circular hollow section) joints, a study on the fatigue behavior of CHS joints with high strength steel is needed instantly. To satisfy this need, this project, based on a systematic research, investigates the fatigue behavior of CHS joints with high strength steel. Firstly, a systematic experimental investigation of behavior of CHS joints will be conducted. From the tests, damage growth and fatigue damage process, the characteristics of fatigue crack initiation and growth in CHS joints with high strength steel are expected to be obtained. Secondly, a series of material tests for standard specimens will be completed. The datum and essential parameters are used to provide for the study of damage model and analysis method, as well as numerical calculation. Thirdly, Based on continuum damage mechanics (CDM) and fatigue damage tests, a damage evolution mechanics model and a fatigue crack growth rate formula is arranged to be proposed. Fourthly, A FE program system for whole CDM-analysis for fatigue damage of CHS joints with high strength steel will be developed, which provides a new approach to analysis the fatigue life of CHS joints with high strength steel. Lastly, on the basis of the experimental and analytical results, a parametric study will be conducted to investigate the fatigue behavior and life of CHS joints with high strength steel. According to the above researches, a reasonable and feasible analytical method will be presented to predict the fatigue life of CHS joints with high strength steel.

管节点作为钢管结构的重要传力部位，其受力性能备受关注。目前，随着结构在空间尺度、载荷等方面需求的不断增加，高强度钢材也越来越多地运用在钢管结构中。由于高强钢强度高，化学成分与普通强度钢材差别较大，使得高强钢管节点的受力性能成为亟待研究的问题，尤其是高强钢管节点疲劳性能的研究，成果非常匮乏，是一个比较新的领域。本项目通过对高强钢管节点的疲劳性能进行试验研究与理论分析，明确其疲劳破坏机理和裂纹的萌生及扩展特征，分析热点应力集中状态。并基于连续损伤力学理论和钢材疲劳损伤试验，建立符合高强钢管节点疲劳损伤过程的损伤演化模型和裂纹扩展率公式，提出完整的高强钢管节点疲劳损伤全过程的有限元分析方法。依据试验和数值分析结果，研究和评价不同参数条件对疲劳性能和疲劳寿命的影响规律。为高强钢管节点疲劳寿命预测评估提供合理可行的参考方法，为管节点疲劳设计方法的完善以及相关规范的修订提供可靠的试验依据和理论储备。

目前，高强度钢材越来越多地运用在钢管结构中，而管节点作为钢管结构的重要传力部位，其受力性能备受关注。由于高强钢强度高，化学成分与普通强度钢材差别较大，使得高强钢管节点的受力性能成为亟待研究的问题，尤其是高强钢管节点疲劳性能的研究，成果非常匮乏，是一个比较新的领域。本项目采用Q460C高强钢，以T型管节点为研究对象，主要研究了高强钢管节点的疲劳性能以及基于连续损伤力学理论的管节点疲劳累积损伤过程的有限元分析方法。主要内容为通过对T型管节点的疲劳性能进行试验研究与理论分析，明确其疲劳破坏机理，了解其疲劳裂纹发展特征。并基于损伤力学理论和钢材疲劳损伤试验，建立了符合管节点疲劳损伤过程的损伤演化模型。在此基础上，对有限元软件ABAQUS进行了二次开发，完成了损伤力学-有限元方法对高强钢管节点疲劳累积损伤过程的全耦合模拟分析，为探索高强钢管节点的疲劳设计方法提供了试验储备和分析手段。通过试验研究和分析对比发现，随着主管厚度的增加，应力幅较小时试验疲劳寿命与规范计算寿命差异变得显著，并依据试验结果初步提出了适用于6mm到10mm壁厚的Q460C高强钢T型管节点的疲劳设计S-N曲线。