金属小径管损伤电磁超声导波检测的高效混合仿真方法及导波换能器可行性研究

A Hybrid Method for Efficient Simulation and Feasibility Study of Guided-wave Electromagnetic Acoustic Transducers for Inspection of Metallic Tubes with Small Diameters

金属小径管广泛应用于航空航天、化工等工程领域关键结构中,对其进行定期无损检测至关重要。作为一种先进电磁无损检测方法,电磁超声导波检测在金属小径管损伤定量评估中具有优势。目前,金属管道缺陷电磁超声导波检测的仿真主要采用有限元等数值模拟方法,涉及电磁场和结构场计算。然而,电磁超声导波检测通常采用激励电流的频率为几百千赫兹,在管道中激发的涡流趋肤深度极小,导致仿真需大量网格进行求解域剖分以确保仿真精度,检测信号计算时间较长。鉴于此,提出一种集成解析法和有限元法的金属小径管缺陷电磁超声导波检测混合仿真方法,采用解析法求解电磁场相关场量,将所求洛伦兹力导入有限元仿真中求解结构场,实现电磁场量和结构场量的快速计算,高效求取检测信号,对金属小径管缺陷定位时,精度高达约98%。在通过全有限元仿真验证所提混合仿真方法正确性的基础上,结合系列仿真和试验研究,对所提导波换能器激发的超声导波模态进行了识别,对该换能器在金属小径管损伤检测和定位方面进行了可行性验证。

Small-diameter metallic tubes(SMTs) are widely employed in key structures of such engineering fields as aerospace, chemical, etc. It is indispensable to periodically inspect SMTs by using nondestructive evaluation techniques. Guided-wave electromagnetic acoustic transduction(GW-EMAT) is advantageous in evaluation of SMTs. The numerical simulation methods such as finite element modelling(FEM) are preferable for GW-EMAT simulations, and the field computation regarding electromagnetics and structural mechanics is involved. However, the frequency of the excitation current of GW-EMAT is several hundred kilo-Hertz, thus the penetration depth of eddy currents induced within the tube is small, which results in the extremely dense mesh for discretizing the solution region and a large amount of time for calculating testing signals. In light of this, a hybrid method integrating the analytical modelling with FEM for efficient simulation of GW-EMAT for inspection of SMTs is proposed. The electromagnetic field is solved by analytical method, and then the lorentz force is imported into the FEM simulation to solve the structural field. Fast computation regarding field quantities of electromagnetics and structural mechanics is realized with the efficient calculation of testing signals, and the accuracy is up to 98%. The proposed method is verified via full-FEM. Following this, through simulations and experiments the modes of the guided waves generated by the proposed GW-EMAT probe are identified, whilst the feasibility of the proposed probe in detection and localization of defects in SMTs is confirmed.