复合状态残余应力-塑性变形的电磁无损评价方法研究

Residual stress (RS) and plastic deformation (PD) due to an unexpected giant load such as a large earth quack are serious threats to the structural integrity of nuclear power plant (NPP). Quantitative nondestructive evaluation (NDE) of RS and PD is very important to guarantee the safety of key nuclear structures. As the influence mechanism of RS and PD on the electromagnetic NDE signals is different and the RS and PD are initiated simultaneously in most cases, the conventional NDE method, which evaluates the PD and RS independently, has problem of lacking evaluation accuracy. In order to find the influence principle of PD and RS on the ENDE signals and their interaction mechanism, and to establish a hybrid experimental system to evaluate the PD and RS at the same time, the following studies are proposed in this project: .1) To establish and validate several online and offline electromagnetic NDE testing systems and fabricate test-pieces of typical materials of nuclear power plants for studying the NDE of the hybrid RS and PD state; .2) Introducing hybrid RS and PD states of different level to the test-pieces and to conduct corresponding online ENDE inspections to gather signals for analysis of the interaction pattern of RS and PD on their ENDE signals; .3) Based on the signal fusion of different ENDE methods, to propose and demonstrate ENDE strategy separately for the austenitic stainless steel and the carbon steel to evaluate RS and PD simultaneously, and to validate its feasibility experimentally; .4) By performing RS and PD evaluations with test-pieces of double axial strain state, high temperature condition, and test-piece simulating practical key NPP structures, to demonstrate the validity of the proposed method for practical NDE applications.

强地震等意外载荷导致的残余应力和塑性变形对承压核电管道、容器等关键部件构成严重安全威胁，电磁无损检测方法是对其进行定量评价以确保结构安全的重要手段。残余应力和塑性变形影响电磁无损检测信号机理不同，且两者往往不可分割，对其分别进行评价的已有方法尚需提高精度。为揭示塑性变形和残余应力在电磁无损评价中的相互影响规律，确立塑性变形-残余应力定量电磁无损评价方法，本项目拟开展研究包括：1）建立多种评价残余应力/塑性变形的在线/离线电磁无损检测系统并验证有效性；2）对核电不锈钢/碳素钢试件导入不同塑性变形-残余应力状态并进行相关在线电磁无损检测实验，分析力学参数与检测信号的相关性及塑性变形/残余应力在检测中的相互影响；3）抽取和融合不同检测方法信号，建立残余应力和塑性变形同步定量评价方法，开发验证综合评价系统；4）基于双轴应力、高温环境和核电结构模拟试件，验证所开发系统对实际核电结构无损评价的适用性。

本项目针对强磁性低活化钢和非磁性304奥氏体不锈钢核电结构典型材料，以建立复合状态下残余应力-塑性变形的定量电磁无损评价方法为目标，开展了如下研究：1）建立了复合状态下残余应力-塑性变形电磁无损评价方法和检测系统；2）明确了复合状态下残余应力与塑性变形对电磁无损检测信号的影响规律；3）建立了基于磁检测信号的复合状态残余应力-塑性变形同步评价方法；4）研究了实际环境下塑性变形电磁无损评价方法的适用性。. 经四年研究，全面实现了项目的预期研究目标。取得主要理论和技术成果包括:. 1）实验研究了巴克豪森磁噪声法、增量磁导率法与非线性漏磁法评价低活化钢塑性变形的可行性，开发了融合多磁检测信号的塑性变形/残余应力一体化无损评价方法，实验验证了有效性。. 2）实验研究了变形履历和疲劳损伤对低活化钢塑性变形电磁无损检测方法的影响，发现两者对增量磁导率法与非线性漏磁法检测信号的影响不大，但磁噪声方法对变形履历较为敏感，在复杂工况下可能导致较大误差。. 3）通过微观分析研究了塑性变形对低活化钢电磁无损检测信号的影响机制，发现在同等塑性变形下，密度较小的微观缺陷会增强、而密度较大的微观缺陷会阻碍磁畴壁移动，影响巴克豪森磁噪声信号；而增量磁导率和漏磁信号变化是由于塑性变形导致的磁导率降低所致。. 4）针对非磁性材料304奥氏体不锈钢明确了残余应力/塑性变形复合状态下自然磁化检测信号的变化规律，基于脉冲涡流与自然磁化的离线、在线检测信号，提出和验证了304奥氏体不锈钢复合状态残余应力-塑性变形的同步检测评价方法。. 项目共发表SCI期刊论文37篇，发表国际会议论文30余篇，授权发明专利14项，获软件著作权2项，出版专著3部，获新疆自治区科技进步二等奖（第2位）。在国内外学术交流活跃，作为大会共同主席2016 年成功组织了第7届ICEF、第25届ENDE国际会议召开，培养硕士生8名、博士生3名，其中硕士生5人、博士生2人毕业。