基于声能特征信息镁合金焊接接头腐蚀疲劳断裂行为表征及寿命评定理论研究

Based on the advantages of light-weight, high-strength, recyclable, and rich mineral resources, magnesium alloys have potential application prospects in “the land , the sea, the air and the aerospace” fields, which need lots of traffic carrying equipments. These structures are often under multiple functions, such as fatigue loading and corrosive environment, which greatly contribute to the fracture failure probability and seriously affect the safety applications of magnesium alloy welding structures. This project will introduce the acoustic emission technology into the corrosion fatigue process of magnesium alloy heterogeneous joint, and study the characterization and assessment methods of the corrosion fatigue fracture behavior. The corrosion fatigue micro damage characteristics (micro-area size, damage law, etc.) of magnesium alloy heterogeneous welded joint, which always tested under the together actions of corrosive environment and fatigue loading, will be analyzed by using the micro/nano mechanics method. And the fatigue micro damage fracture mechanism of magnesium alloy heterogeneous welded joint will be illustrated. The characteristics of acoustic emission signals induced by corrosion fatigue damage will be analyzed, it is to explore the laws and characterization method between corrosion fatigue micro damage and acoustic energy evolution. And finally, the constitutive relation between the micro fracture behavior and the acoustic energy evolution of magnesium alloy heterogeneous joint in corrosive environment will be established. The positioning for the corrosion fatigue damage of magnesium alloy welded joint will be realized, and the safety assessment method of corrosion fatigue life of structures with heterogeneous welded joint will be explored. Research results are helpful to enrich and develop the characterization and assessment theories of corrosion fatigue fracture behavior of magnesium alloy welded joint, and have large scientific significance and application value for the safety and reliable use of magnesium alloys welding structures in corrosive environment.

基于轻质高强、易回收利用、资源丰富等优势，镁合金在“陆、海、空、天”等交通运载装备领域具有潜在的应用前景。但这些结构往往承受疲劳载荷与腐蚀环境等多重作用，影响镁合金焊接结构的服役安全。本项目拟将声发射技术引入镁合金非均质接头腐蚀疲劳研究中，对其断裂行为表征及评定方法进行研究。采用微/纳力学方法，分析腐蚀环境与疲劳载荷耦合作用下镁合金非均质焊接接头微观损伤特征（微区尺寸、损伤规律等），阐明镁合金非均质焊接接头腐蚀疲劳微观损伤断裂机理。分析镁合金焊接接头腐蚀疲劳损伤声发射信息特征，探索腐蚀疲劳微观损伤与声能演变规律及表征方法。建立镁合金非均质接头腐蚀介质中微区断裂行为与声能演变本构关系，并对腐蚀疲劳损伤进行定位，探索非均质接头构件腐蚀疲劳寿命安全评定方法。研究成果有利于丰富和发展镁合金焊接接头腐蚀疲劳断裂行为表征及评定理论，对镁合金焊接结构在腐蚀介质中的安全可靠应用具有重要科学意义和应用价值。

镁合金具有密度小、比强度和比刚度高、易回收利用等优势，是最具发展及应用潜力的结构材料之一。而大部分应用结构均为焊接结构，且服役环境复杂多变（需要承受动载及腐蚀环境如海洋等领域），使耐蚀性较差的镁合金材料应用备受考验。本项目采用声发射技术对镁合金及其非均质接头在空气（惰性环境）及腐蚀环境下的疲劳断裂行为进行实时监测，对其疲劳断裂行为微观损伤过程进行了分析表征；对不同环境耦合作用下声发射数据进行了对比分析，探讨了腐蚀环境、非均质接头、交变载荷对镁合金疲劳断裂行为微观组织结构、声发射信号特征的影响；探索了镁合金及其非均质接头腐蚀疲劳断裂过程中声能演变规律，建立了腐蚀疲劳断裂行为微观损伤与声能演变本构关系。并利用腐蚀疲劳微观损伤、声能等特征参数对镁合金及其非均质接头腐蚀疲劳断裂行为进行了声发射评定及定位方法研究。研究成果有利于丰富和发展镁合金焊接接头腐蚀疲劳断裂行为表征及评定理论，对镁合金焊接结构在腐蚀介质中的安全可靠应用具有重要科学意义和应用价值。