【作者】 任方；

【导师】 刘殿魁；

【作者基本信息】 哈尔滨工程大学 ， 固体力学， 2006， 硕士

【摘要】 本文在波动理论和声发射理论的指导下，从撞击荷载作用下的板中应力波传播和声发射检测出发，对板中的缺陷定位、板开孔声发射波散射以及外界物体撞击板时的波动问题进行了较为全面的理论、实验研究和分析研究，建立撞击荷载作用下撞击物质量和速度、撞击点的最大压力的对应关系，为以后的板中波动研究和声发射预警装置提供依据，评价撞击损伤程度提供实验数据。本文就是通过分析接收到的信号波形对板中的波传播问题进行研究。板中波动问题是波动领域一个重要的课题，此项课题的研究关系到无损检测领域中利用声发射技术对材料进行检测的进展，本文从信号检测的角度，进行以下研究工作：1．通过声发射定位实验，针对实验过程中出现问题本文分析了噪声的来源、参数的正确设置、操作的规范性以及如何避免噪声等问题，对定位精度有很大提高。缺陷定位是通过接收波形来实现的，对波形分析、鉴别波形真伪十分重要。2．首先利用复变函数方法对开孔板的波传播问题进行理论上的推导，发现在低频入射波作用下的开孔板的动应力集中在与入射方向垂直的孔边集中系数在1.5左右，随着入射波频率的增加孔洞对波传播过程中的应力集中影响减小。而且入射波是单一频率不考虑频散，又不考虑波的衰减。本次实验利用声发射技术直接接收信号，然后反推入射波。实际的大多金属材料检测中的声发射波的频率一般都在150KHZ左右，是高频入射，因此孔洞在声发射无损检测中的影响不大，这说明在AE检测时，可以不考虑孔洞的影响。3．通过实验和有限元模拟建立声发射信号和撞击物速度、撞击点最大压力的关系，通过信号峰值和撞击点的最大压力及一定质量物体的速度的对应关系，为以后研制声发射预测装置，评价物体撞击后的损伤程度等提供依据。更多还原

【Abstract】 In this paper base on theories of wave motion and acoustic emission orientation of defects in a plate, scattering of AE wave in a plate with a hole and the problem of wave motion while the plate is operated under impact load are full studied from the angles of theory, experimentation and ansysis beginning from the progation of stress wave in a plate and AE testing. The foundation of the connection with mass of object, velocity and the pressure of the impact point provides the basis and experimental data with wave motion, AE forecast equipment and the evaluation of the fatigue strength. In this paper the problem of the progation of wave in a plate is studied by ansysing the wave form receiving from AE.Wave motion in a plate is an importment question for discussion in the field of wave vibration, its study affects the progress of acoustic emission testing in the field of nondestructive testing. The following work are done from the angle of AE signal testing:1. The following problems are ansysized by the acoustic emission orientation of defects experiment: the sources of noises, how to truly set parameter, how to operate standardly and how to avoid sources of noises and so on. The precision of AE orientation is improved. Orientation of defects comes true by receiving wave form, and it is very importment to analyse wave form and distinguish real wave.2. Firstly, the problem of progation of wave in plate with a hole is studied by using the methods of complex function, finding that: the DSCF of plate with a hole in vercital is about 1. 5 under the low frequency incident wave, in this case, the DSCF is smaller when the wave number becomes larger. And the frequency of incident wave is single, not considering dispersion. In this experiment the signal is directly received by AE, then the incident wave is obtained. Actually the frequency of incident wave is about 150KHZ in AE testing of mostly metal materials, so the influence of hole is not large in AE testing. 3. The connection with AE signal, velocity of object, and the pressure of the impact point is built by experiment and finite element method, this provides basis for the exploitation of AE forecast set and the evaluation of the fatigue strength after impacting.更多还原