【作者】 郭新峰；

【导师】 王晓煜；

【作者基本信息】 大连交通大学 ， 机械工程， 2018， 硕士

【摘要】 现阶段的超声导波无损检测大都以Lamb波为主,但Lamb波在传播过程的频散特性和模态转换特性使回波信号的成分更加复杂,提高了数据处理的难度。而低模态的水平剪切波(SH波)由于在传播过程中没有频散特性和模态转换特性,在超声导波无损检测领域表现出巨大的优越性。本课题基于磁致伸缩材料的维德曼效应提出一种激励SH波的换能器模型,应用磁致伸缩材料在适当磁场的作用下发生扭转形变的特性,以磁致伸缩材料为核心元件,向被测板材中激励多方向性的SH波。本文阐述了板中Lamb波和SH波的激励条件和传播特性,说明了磁致伸缩材料的基本特性,尤其是维德曼效应和麦修茨效应的基本原理,对新型磁致伸缩换能器的磁路进行了设计,分析了该换能器激励和接收SH波的工作原理。以一维坐标系的焦耳效应本构方程为基础,在二维坐标系中推导维德曼效应的本构方程,进而计算出表述该新型换能器本构模型的波动方程。用有限元分析的方法对换能器激励SH波的工作过程进行仿真,优化换能器的结构参数,验证该换能器正常工作的可行性。加工制作换能器的实体模型,提出实验目的和实验流程,选择实验仪器并搭建实验台,通过对采集处理过的实验数据进行分析,判断换能器接收到的超声导波的模态,确定该换能器能否成功激励和接收SHO波。通过本课题的研究,计算推导出了磁致伸缩材料维德曼效应的基本原理和本构方程,初步证明了新型换能器实现工作要求的可行性,并通过有限元仿真和实验研究验证了本课题提出的新型换能器确实能够有效激励并接收SHO波。更多还原

【Abstract】 At present,most of the nondestructive examination ways are based on Lamb wave.However,the dispersion characteristics and modal transformation phenomena during the process of propagation lead to the complexity of echo signal,which increases the difficulty of processing the signal.While the low modal of shear horizontal wave(SH wave)has no dispersion characteristics and modal transformation phenomena during propagation.Therefore,the propagation of shear horizontal wave is of great research and application prospects for ultrasonic guided wave nondestructive examination.A model for generating SH waves based on the Wiedemann Effect of magnetostriction is proposed in this paper.Torsional deformation could be generated in magnetostrictive material in a certain magnetic circuit.The transducer whose core element is made of magnetostrictive material could generate multidirectional SH waves for the tested sheets.In this paper,the excitation conditions and propagation characteristics of Lamb waves and SH waves are elaborated.The basic characteristics of magnetostrictive material are explained especially the Wiedemann Effect and the Matteucci Effect.The structure of the new-type magnetostrictive transducer is designed.The working principle of transducer to stimulate and receive SH waves is analyzed.The constitutive equations of Wiedemann Effect in two-dimensional coordinate system are deduced based on the constitutive equations of Joule Effect in one-dimensional coordinate.And then the wave equations which formulate the constitutive model of the transducer are calculated.The working process of transducer to stimulate SH waves is stimulated by finite element method,which aims to optimize the parameters of the transducer’s structure and verify the feasibility of the transducer’s regular work.The entity model of the transducer is manufactured and the experimental purpose and process are put forward,which guides the selection of experimental instruments and the building of the experimental platform.The collected and processed experimental data is analyzed to determine the modes of ultrasonic guided wave signals received by the transducers and ensure whether the transducer could successfully stimulate and receive SHO waves.Through the research of this subject,the basic principle and constitutive equations of Wiedemann Effect of magnetostrictive material is calculated and deduced,which preliminary proves the feasibility of the new-type transducer to stimulate SH waves.The conclusion that the new-type transducer could truly stimulate and receive SHO wave is corroborated with the finite element stimulation and experimental research.更多还原