稀土超磁致伸缩换能器的研制及其在桥梁检测中的应用

稀土超磁致伸缩材料是在磁场的作用下能产生巨大伸缩变形的一种新型功能材料，它的应用越来越受到广泛的关注，针对目前大型工程质量检测对声波无损评价系统震源的新要求，研制了稀土超磁致伸缩换能器，该换能器以大功率稀土超磁致伸缩材料作能量转换部件，具有能量集中、发射声波传播距离远、发射频率适中，容易与采集系统集成而实现自动检测控制，显著提高工作效率．最后以某桥梁声波CT无损评价为例说明其广泛的应用。     

智能控制复合相干电火花震源技术研究

针对已有电火花震源产品地层分辨率和地层穿透深度不能兼顾的问题,提出了一种新的电火花震源技术--智能控制复合相干电火花震源系统.该震源系统包含六个组成部分,由嵌入式智能集成芯片实现智能控制.该系统在双震源模式下可以交替发射两种不同能量的地震信号,在一次探测中同时获得浅层的高分辨率地震资料和较深层的地震资料,提高勘探质量和效率;此外,该震源还可以相干激发,改善震源子波品质,提高震源的地层分辨率.     

延时叠加震源激发地震波能量的研究

根据弹性波动理论,分析了装药爆炸时冲击波转换成地震波的能量关系,对多级小药量垂向延时震源地震波能量叠加的原理进行了研究,建立了简化模型.试验结果表明,垂向延时叠加震源可在保证一定的信噪比的前提下,提高地震波的主频率,是高分辨率地震勘探的较理想的激发震源.     

大坝CT技术研究进展

大坝CT检测具有能快速无损地探测大坝内部较深部位隐患的优点,相关研究工作越来越受到重视。论文对分别基于检测弹性波、电磁波和电阻率分布来实现的三种大坝CT技术进行了简介,重点对目前认为较为成熟的声波大坝CT技术从可行性、原理、硬件设置、软件技术等方面总结了其研究进展。对声波大坝CT技术研究中存在的关键问题和今后的发展趋势进行了讨论。     

高精度分布式面波地震仪

针对基于折射波或反射波法的传统地震仪存在对波阻抗差异较小的地下介质的分辨率较低的问题,设计一种高精度分布式面波地震仪。利用数字检波器对人工震源产生的面波信号进行采集,实现具有大动态范围、宽频带响应的面波检波阵列的设计。研制基于FPFA的地震信号采集节点,实现强干扰背景下地震信号的纯数字滤波与采集。此外,通过4G模块实现数据的无线传输和控制,从而提高探测效率。现场测试表明:在某高层建筑地基施工现场,仪器可实现对地震面波信号的高精度阵列采集,其探测反演结果与直接打钻结果基本一致,可有效验证其面波探测功能。     

利用弹性波频率进行地质勘探的思考

弹性波频率勘探是近年发展起来的一种新的浅层地球物理勘探方法,具有简便、快速、经济、分辨率高、成果直观、适用场地小等优点,已在许多领域得到应用,并取得了良好的应用效果。通过对弹性波频率勘探技术的发展概况、探测原理、主要特点及其野外测试方法进行深入思考,能够有效地了解其应用范围及目前存在的问题,使之更好地用于地质勘探之中。     

地下爆炸应力波分段有限元正演技术研究

为解决地下爆炸应力波跨时间、空间和应变率尺度正演难题,本文提出了一种分段有限元正演技术。该技术将求解区域划分为爆炸震源区和弹性响应区,在爆炸震源区采用动力有限元方法,在弹性响应区采用普通有限元方法,不同段界面之间采用节点位移的连续性为边界条件。本文从理论上说明了分段有限元正演思想的合理性,给出了该技术的具体实施步骤,并通过对比模拟研究验证了分段有限元正演技术在用于模拟爆炸应力波传播方面的正确性和有效性。     

利用弹性波频率进行地质勘探的思考

弹性波频率勘探是近年发展起来的一种新的浅层地球物理勘探方法,具有简便、快速、经济、分辨率高、成果直观、适用场地小等优点,已在许多领域得到应用,并取得良好的应用效果。通过对弹性波频率勘探技术的发展概况、探测原理、主要特点及其野外测试方法进行深入思考,能够有效地了解其应用范围及目前存在的问题,使之更好地用于地质勘探之中。     

激光热弹激发超声的有限元数值模拟

1引言 由于激光超声具有非接触激发,能一次同时在样品中激发多种模式超声波和激光激发的超声波频带宽等特点,在无损检测领域得到越来越广泛的应用.当激光能量较低,未引起材料的熔融时,激光超声的激发机理是热弹机制激发.这一物理过程不仅包括瞬态热传导,而且包括瞬态弹性波的激发和在有限空间的传播.     

弹性波在锚杆锚固体系中传播规律的研究

通过理论分析，研究了波在锚杆体内波动能量的外泄特征，研究了弹性波在锚杆、岩土介质及其耦合体系中的传播规律，得到了波在锚固体系中的衰减规律及传播机制．为锚杆锚固质量的无损检测提供了重要的理论依据．     

埋地管道漏损检测的声传播特性研究

地下管道漏损的准确定位问题一直是困扰世界范围内供水系统和市政建设的难题。管道漏损不仅会浪费大量的资源,而且还会造成严重的事故以及环境污染。针对埋地管道这样一个典型的土-管-液三相耦合问题,将管道周围土壤做弹性体考虑,对弹性介质中充液管道的声传播特性进行了解析研究。推导了低频域周向波数n=0的轴对称管道振动耦合方程,通过数值方法分别得到了流体波(s=1)和壳体压缩波(s=2)的复波数解。结果显示,管外土介质会使管道流体波波数减少(也即加快波的传播速度),而对壳体压缩波的传播影响较小。由于管-土作用产生的能量辐射,在整个研究频段s=1波和s=2波都有较大的衰减。研究结果可为埋地管道漏损的精确检测提供理论支持。     

应用于热声机械的声波平面传递装置

应用于热声机械的声波平面传递装置,由柔性部分和刚性片部分组成.通过引入柔性结构,将传递声波所必需的弹性部分和惯性部分分开,实现刚性片的平面运动,从而达到声波的平面传递.依据弹性部分的不同形式,声波平面传递装置有3种形式:弹性膜型、折环型和弹性环型.将这种装置应用于热声机械中,可以大大改善热声系统中声波传递的性能,拓展热...     

Weight‐adjusted discontinuous Galerkin methods: Matrix‐valued weights and elastic wave propagation in heterogeneous media

Weight‐adjusted inner products are easily invertible approximations to weighted L² inner products. These approximations can be paired with a discontinuous Galerkin (DG) discretization to produce a time‐domain method for wave propagation which is low storage, energy stable, and high‐order accurate for arbitrary heterogeneous media and curvilinear meshes. In this work, we extend weight‐adjusted DG methods to the case of matrix‐valued weights, with the linear elastic wave equation as an application. We present a DG formulation of the symmetric form of the linear elastic wave equation, with upwind‐like dissipation incorporated through simple penalty fluxes. A semidiscrete convergence analysis is given, and numerical results confirm the stability and high‐order accuracy of weight‐adjusted DG for several problems in elastic wave propagation.     

火炮身管超声导波频散特性及传感器配置

超声导波检测技术具有检测距离远、效率高的优点,适用于检测火炮身管等圆管类结构,具有突出的军事应用价值和前景。首先对圆管超声导波理论进行推导,并对身管损伤的几种常见类型进行分析研究。采用数值计算的方法绘制频散曲线,通过分析其频散特性对导波检测频率进行优选,初步得到了最佳的检测频率范围;其次着重对传感器种类选择、数量及分布方式与导波传播特性的关系进行研究。实验表明,导波检测的最佳频率范围为0～300 kHz,且导波弯曲模态一般不宜作为检测模态;传感器数量的增加不仅增强了激励信号的强度,还有效抑制了身管中导波的频散。     

弹性波三维散射快速多极子间接边界元法求解

边界元方法对于无限域中弹性波散射求解具有独特优势,但求解矩阵的非对称稠密特征极大限制了该方法在大规模实际工程中的应用。为此,基于单层位势理论,结合快速多极子展开技术,通过对球面压缩波和剪切波势函数的泰勒级数展开,建立一种新的快速多极间接边界元方法,以实现大规模弹性波三维散射的精确高效模拟。算例分析表明所提方法能够大幅度降低计算时间和存储量,可在目前普通计算机上快速实现上百万自由度弹性波三维散射问题的快速精确求解。最后以全空间椭球形孔洞群对平面P波、SV波的散射为例,揭示了三维孔洞群周围稳态位移场和应力场的若干分布规律。该文方法对低无量纲频率（ka<5.0）的大规模多体散射问题尤为适合。     

Reflection and refraction of plane waves at interface between two piezoelectric media

This paper analyses reflection and refraction of plane waves at a perfect interface between two anisotropic piezoelectric media. The equations of elastic waves, quasi-static electric field, and constitutive relationships for the piezoelectric media are derived. A solution based on the inhomogeneous wave theory is developed to address the inconsistency between the numbers of independent wave modes in the media and the numbers of interfacial boundary conditions to obtain accurate reflection and refraction coefficients in case of strong piezoelectric media, where all the elastic and electric continuity conditions across the interface are satisfied simultaneously. The study shows that there exist independent and zero energy wave modes satisfying the general Snell’s law and propagating along the interface for any incident wave angle. These waves can be treated as pseudo surface waves. It is further found that all the reflection/refraction waves including the pseudo surface waves obey the energy conservation law at the interface boundary. In addition, the analysis also reveals that the reflection and refraction elastic waves can turn into pseudo surface waves at some critical incident angles.     

A Blasting SourcesBased Approach to Inspection of Faults in Dam

An approach to inspection of incipient faults in dams by nondestructive testing is a so far emerging inspection technology in the world. In this paper, inspection principles, system integrity and key items for the new blasting sourcebased technology for inspection of incipient faults in dams, different from common nondestructive testing, are presented, following briefing experiences in dam inspection by elastic wave CT in recent years. Specific procedures and goals for further spreading and application as well as conclusion are introduced finally.     

Interaction of shear waves with a griffith crack situated in an infinitely long elastic strip

This paper deals with the propagation of shear waves in a wave guide which is in the form of an infinite elastic strip with free lateral surfaces. This strip contains a Griffith crack. An integral transform method is used to find the solution of the equation of motion from the linear theory for a homogeneous, isotropic elastic material. This method reduces the problem into an integral equation. It has been observed that only shear waves with frequencies less than a parameter-value, depending on the width of the wave guide, can propagate. The integral equation is solved numerically for a range of values of wave frequency and the width of the strip. These solutions are used to calculate the dynamic stress intensity factor, displacement on the surface of the crack and crack energy. The results are shown graphically.     

Elastic wave and energy propagation in angled beams

This investigation comprises an experimental and numerical study of elastic wave propagation in angled beams. Axial impact by two strikers of different lengths was applied to three steel beams, each bent to incorporate a “V” section of different angle in the middle. Finite element simulation using ABAQUS was employed to examine details of the elastic waves generated in the impact tests. The numerical results correlated well with experimental data, and computational simulation was utilized to analyse the propagation of energy associated with the elastic waves. This demonstrated that after several reflections from and transmission across the bends energy is progressively smeared throughout the entire beam and does not concentrate at any particular segment; the bulk of the energy is conveyed via flexural waves. Numerical simulation of wave propagation in a beam with a single angle was also undertaken to study the energy associated with waves reflected from and transmitted across the bend, and how these are affected by the bend angle. The effects of input pulse duration, beam thickness and beam material properties on energy reflection and transmission at a bend are also discussed; this leads to the conclusion that when a longitudinal pulse of a particular frequency impinges on a bend, the ratio between its wavelength and the beam thickness governs the energy reflected from and transmitted across the bend. Moreover, the bend junction geometry (curvature) is found to have a significant influence on the energy reflected and transmitted, especially for obtuse bend angles.