再制造涂覆层下基体疲劳裂纹的红外热波辨识及表征

Identification and characterization of fatigue cracks in base metal under coating layer is a difficult problem in the field of service safety evaluation of remanufactured parts. The project selected engine crankshaft of heavy-duty vehicles as the research subject. Remanufacturing coating layers will be prepared by high speed arc spraying and supersonic plasma spraying method respectively, and low frequency ultrasonic excitation active infrared heat wave technology is used as evaluation tools. Aim at the perturbation influence on heat generation and heat transmission induced by unsteady characteristics of remanufacturing coating structure, the heat generation mechanism of fatigue crack defects in the substrate under remanufacturing coatings will be explored by low frequency ultrasonic excited method to obtain the master parameters of crack from infrared thermal map, and the conducting law from the structure defects of remanufacturing coatings to the fatigue crack in base metal will be studied to reveal the factors affecting the surface thermal map. At last an identification method of mixed heat wave from coating layer cracks and substrate cracks will be proposed, and at the same time a quantitative model of fatigue crack depth in base metal under remanufacturing coatings will be established to realize the service safety evaluation of remanufacturing parts.

辨识及表征再制造涂覆层下基体疲劳裂纹是再制造零件服役安全评价的重要难题。本项目选定重载发动机关键零件曲轴为研究载体，以高速电弧喷涂和超音速等离子喷涂为再制造涂覆层制备方法，以低频超声主动激励红外热波技术为评价手段，针对再制造涂覆层非稳态结构特征引入的生热与传热的扰动影响，探索低频超声波在再制造毛坯基体疲劳裂纹部位的激励生热机制，获取基体裂纹热波的主控参量；研究再制造涂覆层结构对基体裂纹异常热波的传导规律，揭示涂覆层传热性能对表面热波温度场的影响因素；提出涂覆层裂纹与毛坯基体裂纹混合热波分离的辨识方法，建立再制造毛坯基体疲劳裂纹深度的表征模型，实现再制造涂覆层/基体的服役安全评价。

涂覆层下基体疲劳裂纹辨识及表征是再制造零件质量评价和再制造服役安全评估中面临的重要难题。针对这一难题，本项目采用超声主动激励的红外热成像检测技术，研究了超声波在喷涂层结构中的传播衰减规律，以及喷涂层和基体结构中的裂纹缺陷在超声波激励下的基本生热理论、生热机制和热图特征；揭示了材料中不同深度的点热源、线热源产生的热波向表面传播过程中的干涉效应，以及热波干涉导致的表面热波相位特征变化规律；提出了采用热波相位偏移特征进行再制造涂覆层下基体疲劳裂纹识别的方法，并采用数值模拟和试验手段进行了验证；构建了基于表面热波相位的涂覆层裂纹与基体裂纹热波特征分离方法；实现了再制造涂覆层下基体裂纹缺陷的辨识与表征。项目研究成果有望应用于再制造零件质量评价和再制造服役安全评估实践。