Quality control and fatigue design of friction stir welded joints in aluminum bridge decks

北美的公路管理部门目前面临着巨大而紧迫的桥梁维护成本。最近一份关于桥梁中铝使用的行业报告发现，用于新桥梁和修复项目的轻质桥面板是一个特别有前途的应用领域。随后的一项经济研究得出结论：1）桥面板是一种应用，铝显然具有市场增长潜力，2）搅拌摩擦焊（FSW）是一种变革性技术，可能对铝桥面板的耐久性和经济性产生重大影响。加拿大还没有结构搅拌摩擦焊接接头的设计规范。现有的国际规范（如ISO、AWS）包括基于“最佳做法”的质量控制规定，但尚未与结构性能相关。该项目将由滑铁卢大学（UW）和魁北克大学（UQAC）的研究人员合作进行，目标是为铝桥面板中FSW接头的质量控制（QC）和疲劳设计制定改进的“基于性能”的规范规定。为了实现这一目标，将执行以下任务：1）试样制备和冶金分析; 2）FSW试样的疲劳试验; 3）FSW试验结果的统计和断裂力学分析;以及4）为FSW桥面接头的QC和疲劳设计制定改进的指南。该项目的一个特别新颖的方面将是疲劳测试和分析具有不同质量水平的焊缝（即具有不同严重程度的各种缺陷类型）的计划。该项目将通过获得新知识并将这些知识转化为设计建议，为当前的知识水平做出重大贡献，这将使加拿大工业和从事FSW的研究人员进入该领域的前沿。

Highway authorities in North America are currently faced with significant and pressing bridge maintenance costs. A recent industry report on aluminum use in bridges found light weight decks for new bridges and rehabilitation projects to be an application area with particular promise. A subsequent economic study concluded that: 1) bridge decks are an application where aluminum clearly has a potential for market growth, and 2) friction stir welding (FSW) represents a transformative technology, which could have a significant influence on the durability and economics of aluminum bridge decks. A design code for structural FSW joints does not yet exist in Canada. Existing international codes (e.g. ISO, AWS) include quality control provisions based on "best practice", which have not yet been related to structural performance. This project will be be performed collaboratively by researchers at the University of Waterloo (UW) and Université du Québec à Chicoutimi (UQAC) with the goal of developing improved, "performance-based" code provisions for the quality control (QC) and fatigue design of FSW joints in aluminum bridge decks. To achieve this goal, the following tasks will be performed: 1) specimen preparation and metallurgical analysis; 2) fatigue testing of FSW specimens; 3) statistical and fracture mechanics analysis of FSW test results; and 4) development of improved guidelines for QC and fatigue design of FSW bridge deck joints. A particularly novel aspect of the project will be the plan to fatigue test and analyze welds with varying levels of quality (i.e. various defect types with varying degrees of severity). This project will make a significant contribution to the current state-of-knowledge, which will move the Canadian industry and researchers working on FSW to the leading edge of this field, through the new knowledge acquired and the transformation of this knowledge into design recommendations.