基于特征空间分析的金属蠕变超声检测综合评价参数研究

Creep is one of the main reasons for high temperature metal devices failure in energy and petrochemical industry. Ultrasonic testing has been researched a lot for metal creep inspection, but a suitable creep evaluating parameter balanced between sensitivity and interference-immunity is still not determined. To solve this problem, this project is suggested with the purpose of finding a multi-feature parameter, and establishing a reliable metal creep inspecting method with it. To achieve this goal, a concept of feature space analysis is proposed; a method for creep feature space separating is established. Creep feature space is a feature set only including modulating feature of creep structure in the specimen. Then researching the modulating mechanism from creep structure to ultrasonic inspecting signal, analyzing the correspondence relationship between feature bases and modulating factors, and the transfer model including nonlinear units for ultrasonic signal will be built. Studying optimal fitting method for nonlinear transfer modal, obtaining quantitative mapping relationship between creep feature space and creep status of metal, then a functional relationship from projection vector to creep status will be established. Using creep feature space projection vector as multi-feature parameter, a creep ultrasonic inspecting procedure will be set up. The achievement of this project will promote the development of metal creep ultrasonic testing technique, and lay a foundation for NDE of creep damage in high temperature devices.

蠕变是能源和石化领域高温金属设备发生损伤的主要原因之一，使用超声方法对金属的蠕变状态进行无损评价已成为相关领域的研究热点，但目前尚未提出能够兼顾灵敏度和抗干扰能力的蠕变评价参数。针对此问题，本项目以提出金属蠕变评价的综合特征参数、建立相应的检测技术流程为目标，提出特征空间分析的概念，研究仅包含蠕变组织调制效应的蠕变子特征空间的分离方法；研究蠕变组织对超声信号的调制机理，分析蠕变子特征空间中各特征基对应的调制因素，建立包含非线性环节的超声信号传递模型；研究非线性传递模型的拟合优化方法，获得蠕变子特征空间与蠕变状态的量化映射规律，建立投影矢量与蠕变程度的函数关系；提出以蠕变子特征空间投影矢量为综合特征参数的蠕变超声检测技术流程，促进金属材料蠕变超声检测技术的发展，为解决高温设备蠕变损伤无损评价问题奠定基础。

本项目以研究金属蠕变检测的超声评价方法为目标，开展了相关研究。理论方面，研究了蠕变超声检测的线性模型、非线性模型以及时域和频域模型，整理了不同模型下的敏感参数提取算法；在分级评价特征空间投影法的基础上，分析了特征空间线性化方法，提出了蠕变检测的子特征空间和特征基函数的分离方法和数学表达，形成了基于特征空间投影的敏感参数获取及评价曲线建立方法。实验方面，制作了高温时效试块和蠕变试块，通过检测试验分析了不同参数的检测能力，验证了特征空间投影法提取敏感参数的有效性，实现了对于不同蠕变状态，蠕变与高温时效状态，及高温时效状态的检测，建立了基于特征空间投影的金属材料蠕变超声检测技术流程。