摘要
残余应力诱发开裂问题仍是限制大型构件激光熔化沉积工业化应用的一大瓶颈。因此,探究激光熔化沉积大型复杂构件残余应力的演化规律,以及残余应力诱发裂纹萌生和扩展的微观组织相关性具有重要意义。通过对大型钛合金构件开裂断口形貌分析及宏观热-力耦合有限元计算,首次发现激光熔化沉积过程独特的热应力三阶段非对称循环加载模式,即稳定循环-突增加载阶段、非线性循环加载阶段及线性循环加载阶段。以热-力耦合计算得到的残余应力为输入,采用耦合损伤的晶体塑性计算研究了3种热应力加载模式对激光熔化沉积特有的网篮组织的破坏程度,发现线性循环加载模式对网篮组织破坏性最大,稳定循环-突增加载模式破坏性次之,非线性循环加载模式破坏性最小。这种热应力加载模式、断口形貌及微观组织分析进一步表明,残余应力诱发开裂现象是由过大的热应力累积、零件的几何特征、热应力加载模式及成形缺陷等多因素协同控制的,而非单一因素影响,这也为从适时消除应力、优化零件结构及工艺参数、减少和抑制缺陷产生等方面系统化控制开裂问题提供了方向。
Residual stress induced cracking is still a bottleneck restricting the industrial application of laser melting deposition for large structures.Therefore,it is very important to explore the evolution law of residual stress and the microstructure correlation of residual stress–induced crack initiation and propagation in the process of laser melting deposition manufacturing of large components.Based on the fracture morphology analysis of large titanium alloy components and the macroscopic thermal-force coupling finite element calculation,the unique three-stage asymmetric cyclic loading mode of thermal stress during laser melting deposition is first found,namely,the stable cycle–burst loading stage,the nonlinear cyclic loading stage and the linear cyclic loading stage.The damage degree of three thermal stress loading modes on the unique basket structure of laser melting deposition is studied using coupled damage crystal plasticity simulation,and it is found that the linear cyclic loading mode is the most destructive,followed by the stable cycle–burst loading mode,and the nonlinear cyclic loading mode is the least destructive.This thermal stress loading mode,fracture morphology and microstructure analysis further show that the residual stress-induced cracking phenomenon is controlled by multiple factors such as excessive stress accumulation,geometric characteristics of parts,thermal stress loading mode and forming defects,rather than a single factor.It also provides a direction for systematic control of cracking from the aspects of timely stress relief,optimization of parts structure and process parameters,and reduction and suppression of defects.
作者
谢勇
张文奇
武致军
严振宇
彭深沉
黄鹏
郭宁
周庆军
XIE Yong;ZHANG Wenqi;WU Zhijun;YAN Zhenyu;PENG Shenchen;HUANG Peng;GUO Ning;ZHOU Qingjun(Capital Aerospace Machinery Co.,Ltd.,Beijing 100076,China;Qilu University of Technology(Shandong Academy of Sciences),Jinan 250353,China;Shandong Institute of Mechanical Design and Research,Jinan 250031,China)
出处
《航空制造技术》
CSCD
北大核心
2024年第15期55-64,共10页
Aeronautical Manufacturing Technology
基金
国家重点研发计划(2022YFB4602205)
国家自然科学基金(52105370)。
关键词
激光熔化沉积
TC11钛合金
残余应力
裂纹扩展
晶体塑性
Laser melting deposition
TC11 titanium alloy
Residual stress
Crack propagation
Crystal plasticity
