Abstract: Considering the increasing industrial applications of metal additive manufacturing, it was important to analyze residual stress caused by forming processes and detect residual stress with ultrasonic nondestructive testing, and in coating structure, the complex distribution of materials made the local acoustic elastic characteristics uncertain, resulting in a certain detection errors. Thus, after analyzing the distribution of materials, the stress inversion model of coating structures was proposed. Firstly, the propagation of ultrasound and related ultrasonic signals was analyzed based on the acoustic elasticity theory in variable distributions of materials and stress. Then, considering the forming processes of different coating structural areas in the plasma spray welding additive processes, the distribution of materials in coating structure was discussed. Analyzing the relationship between the acoustic-elastic characteristics and material distribution in bonding area, the stress inversion model of coating structural areas was presented. Finally, the coating structure samples of base material(C45E4) and coating material(Cu) were designed and prepared by plasma spray welding, the ultrasonic testing with tensile/compressive stress was given. Comparing the testing results and calculation ones, the stress inversion model of coating structure is effective. After discussing the feasibility in stress ultrasonic testing, the proposed method is considered as the potential tool in the quality evaluation and monitoring for coating structures.

Key words: coating structure, ultrasound detection, acousticelastic characteristic, additive manufacturing, material distribution

摘要： 随着金属增材制造工艺的工业化应用，涂层成形过程中残余应力及其超声无损检测技术日益受到重视，但涂层结构中材料复杂分布状态使其局部声弹性特征不确定，导致出现一定的误差。针对这一问题，通过分析涂层结构材料区域分布，提出其应力反演方法。首先，基于声弹性理论，分析不同材料及应力分布下超声传播及信号演化过程。其次，结合等离子喷焊增材工艺中涂层结构不同区域的成形过程，分析涂层结构的材料分布状态，重点讨论结合区域的材料分布规律及其声弹性特征表达，构建涂层结构的应力反演模型。最后，采用等离子喷焊增材工艺，设计并制备基体材料（C45E4）和涂层材料（Cu）的涂层结构试件，开展拉/压应力下的超声检测试验，通过实测值与模型值的比较分析，验证了所提出的涂层结构应力反演模型的有效性，并分析了模型在涂层结构应力检测中的可行性，可将其作为等离子喷焊增材工艺中涂层成形质量评估及状态监测的方法支撑。

关键词: 涂层结构, 超声检测, 声弹性特征, 增材制造, 材料分布