薄壁金属与非金属环形粘接件粘接质量超声检测方法研究

为了解决薄壁金属与非金属环形粘接件粘接质量的常规无损检测方法缺陷定位、定量准确性不高的问题,本文采用超声C扫描成像检测和接触式超声脉冲回波法,通过对环形粘接件人工缺陷对比试块、粘接产品件的检测,以及人工缺陷对比试块的解剖,对薄壁金属与非金属环形粘接件的粘接质量进行了研究.结果表明采用超声C扫描成像检测方法能检出大面积的脱粘缺陷和气孔缺陷,而接触式超声脉冲回波法无法区分粘接界面的缺陷信号,粘接缺陷无法被检出.因此超声C扫描成像检测方法对环形粘接件粘接质量具有良好的检测适用性和可靠性,是评价薄壁金属与非金属环形粘接件粘接质量有效的无损检测方法.     

阻尼材料粘接质量超声检测试验研究

为了研究阻尼材料粘接质量的超声检测方法,用超声透射法和反射法分别检测了一种阻尼材料的5种不同样品,结果表明:超声透射法和反射法能够检测出样品中模拟的夹杂气泡、粘接面开裂、异物夹入等粘接缺陷,对于带空腔结构的阻尼橡胶板,内部的空腔结构和粘接缺陷也都能检测出来。     

金属与非金属粘接质量的声阵列检测方法

目的　研究金属与非金属质量检测的新方法 .方法　通过对粘接结构施加微力、阵列传声器检测、对信号进行处理识别 ,从而完成粘接结构力学性能的无损预报 .结果和结论　提出了一种微声激励、声阵列检测的新的检测方法和总体设计方案 ,该方法可以解决超声检测耦合难、检测速度低、误判漏判率高的问题     

金属与非金属粘接质量的声阵列检测方法

目的 研究金属与非金属质量检测的新方法。方法 通过对粘接结构施加微力、阵列传声器检测、对信号进行处理识别,从而完成粘接结构力学性能的无损预报。结果和结论 提出了一种微声激励、声阵列检测的新的检测方法和总体设计方案,该方法可以解决超声检测耦合难、检测速度低、误判漏判率高的问题。     

基于LFM的橡胶脱粘超声检测方法研究

针对SYS510e型空气弹簧底板的金属橡胶粘接结构橡胶脱粘缺陷超声检测难以辨识问题,提出采用改进的线性调频脉冲代替传统窄脉冲作为超声波激励信号,增大超声检测的信号能量和频谱宽度.在宽频带超声检测的基础上,采用小波包-奇异值分解方法解析超声回波在不同粘接状态、不同频率范围的时频能量分布,提取更稳定、一致性更好的橡胶脱粘辨...     

橡胶/铝合金粘接构件脱粘缺陷非线性超声检测技术研究

为提高橡胶/铝合金粘接构件粘接界面缺陷检测结果的可靠性,解决缺陷定量化表征问题,该文采用非线性超声检测技术对含模拟脱粘缺陷试样进行研究,建立非线性弹簧模型,通过采集模拟脱粘缺陷试样上缺陷处的基波信号和二次谐波信号,获得缺陷非线性系数β值,建立缺陷面积与非线性系数β值关系拟合曲线。对比自然试样中缺陷的非线性超声检测和超声C扫描检测结果,验证非线性超声检测结果可靠,因此非线性超声检测技术是评价橡胶/铝合金粘接构件粘接界面粘接质量的一种可靠方法。     

粘接结构超声信号的小波分解与特征提取

粘接结构因其独特的物理、机械和声学特性在诸多领域具有非常广泛的应用，对于铝合金-橡胶这样一种金属-非金属粘接结构的超声检测信号，本文利用了小波变换的多分辨率分析(时频分析)的方法，有效地提取出了反映多层材料粘接状况的信号特征，该特征提取方法可用在粘接结构的无损检测中。     

陶瓷涂层与金属基体结合质量的超声检测方法研究

陶瓷材料在耐高温、耐腐蚀、耐磨损等方面具有金属不能比拟的优势,通过在金属基体上涂覆或者粘接陶瓷材料可实现优异的综合性能。陶瓷涂层与金属基体的结合质量影响着其使用性能和安全性,检测陶瓷涂层与金属基体的结合质量具有重要意义。利用超声直入射检测方法研究陶瓷涂层与金属基体的粘接质量,并对获得的信号进行分析,定义了评价粘接质量的结合质量系数,利用该系数可对粘接质量作出合理评估。     

不等厚复合构件相控阵超声脱粘检测技术仿真研究

鉴于不等厚复合构件结构的特殊性,采用传统超声检测技术检测此类构件的粘接质量是非常困难的。采用超声相控阵技术实现界面粘接质量的检测。分析研究了不等厚复合构件脱粘检测的特殊性。建立了相控阵超声换能器的辐射声场模型,基于仿真得到的声场,研究了采用超声相控阵技术检测不等厚复合构件界面脱粘的可行性。仿真结果表明,通过控制相控延时,可使检测声束在检测区域内聚焦到任意位置处,保证在厚度变化的界面处回波信号幅度的一致性,可用于此类构件的界面脱粘检测。     

SH电磁超声换能器优化设计及粘接强度测量

电磁超声换能器(Electromagnetic Acoustic Transducer,EMAT)使用时无需耦合剂，可以便捷地应用于严苛工况下结构的超声检测。但由于EMAT复杂的多物理场换能机理，通常存在换能效率低，接收信号信噪比小等缺点。针对上述问题，文章开展了线圈宽度、线圈间距及磁致伸缩贴片等参数对EMAT换能效率的影响研究，优化设计了SH电磁超声换能器。实验结果表明，一定厚度的磁致伸缩贴片对EMAT的换能效率有较明显的提高。基于SH0导波对界面变化的敏感性，采用优化设计的EMAT激发SH0导波，对固化温度等因素引起的多层铝板弱粘接结构件进行粘接性能的检测，实验测得的粘接强度与结构拉伸强度的变化趋势一致，表明优化后的EMAT可以适用于粘接结构状态的检测。     

细铜棒内部缺陷超声自动检测系统设计

目的　检测细铜棒内部缺陷 .方法　采用组合超声检测法 ,结合多探头数据融合技术 .结果　实现了细铜棒内部缺陷的定性、定量自动检测 .结论　利用组合超声法和数据融合技术可以提高细铜棒的检测精度 .     

新技术在堤坝隐患自动识别系统中的应用

目的　为了对堤坝隐患进行有效的识别 ,本文提出了 3种新技术 ,即堤防隐患雷达探测系统、多传感器探测网络系统及其数据融合技术、红外成像技术在堤坝隐患自动识别系统中的应用 .方法　介绍了这些应用的系统组成、原理以及方案 .结果与结论　通过研究发现这 3种新技术能够用于堤坝隐患自动识别系统中 ,证明了这些方法的有效性 .     

Parametric Design of Fusion Diagrams and Solubility of Phases

Relationships between the fusion diagrams and the thermodynamic characteristics of the phases involved are analyzed using a relatively simple, thermodynamically substantiated equation of salt crystallization isotherms. The dimensionless parameters \(\begin{gathered} {\text{RMn}}_{\text{2}} {\text{O}}_{\text{5}} {\text{ = RMnO}}_{\text{3}} + \frac{1}{3}{\text{RMn}}_{\text{3}} {\text{O}}_{\text{4}} + \frac{1}{3}{\text{O}}_{\text{2}} \hfill \\ \frac{{\Delta G}}{{RT}} \hfill \\ \end{gathered} \) and \(\frac{{\Delta Z_{{\text{AX}}} }}{{RT}}\) are shown to be basic to the thermodynamics of liquid–solid and liquid–liquid phase equilibria. A number of techniques for evaluating thermodynamic constants from fusion diagrams and calculating elements of fusion diagrams from thermodynamic data are described and exemplified by particular systems. The effects of the basic parameters on the solubility of phases and phase equilibria are examined, and critical values of these parameters are determined for the first time. Parametric criteria for liquid immiscibility in salt systems are established.     

Fracture toughness behavior of weldments with mis-matched properties at elevated temperature

High temperature fracture toughness tests were performed on welded specimens of 1Cr-1Mo-14 V steel with different levels of mismatch between the base metal and the weld metal and the cracks lying along the fusion line. A wide range of fracture toughness values were obtained for weldments, as opposed to a unique value of J_IC and a unique J-R curve typically obtained for homogeneous materials. Detailed observations of the crack path within the weldments were made to understand the wide scatter in the fracture toughness behavior. The yield strength mismatch between the base metal and the weld metal was found to directly influence the stable crack path, and hence the fracture toughness behavior. The denomination of ‘apparent fracture toughness’ was used to describe the variability of the fracture toughness in the weld region due to microstructure and mechanical property gradients. The apparent fracture toughness exhibited a minima at a fixed distance from the fusion line for a specific weld. The relative position of the fatigue precrack with respect to the fusion line and the region of low fracture toughness was also shown to influence the measured fracture toughness behavior of the specimen. A frame-work is provided for representing the weld fracture toughness behavior and the associated variability due to microstructural gradients. This revised version was published online in August 2006 with corrections to the Cover Date.     

Relationship between crystallization temperature and melting temperature in crystalline materials

The ratio of the absolute temperature at which the homogeneous nucleation rate or the crystal growth rate is maximum (T _cmax) to the absolute melting temperature (T _m) is analysed by two parameters: one is the ratio of the activation energy for migration (E) and the heat of fusion (H _m), the other is the ratio of mean molar surface energy and H _m. In analysing the crystallization data for a large number of crystalline materials such as metals and inorganic, organic and polymeric materials, the ratios and E/H _m show roughly constant values for a given type of material. The constancy of the two parameters will then give rise to a constant value ofT _cmax/T _m.     

Ni,Fe对Al90TM5Ce5非晶合金稳定性的影响

本文研究了Al90 Fe5Ce5和A190 Ni5Ce5非晶合金及预峰在晶化过程和时效过程中的稳定性。Al90Fe5Ce5非晶合金的晶化开始温度TX 和时效稳定性比Al90 Ni5Ce5非晶合金高。Al90 Fe5Ce5非晶合金预峰所对应的化学短程序结构的稳定性较高 ,而Al90 Ni5Ce5非晶合金预峰所对应的化学短程序结构的稳定性差 ,甚至通过常温时效消失。非晶合金的稳定性与预峰所对应的化学短程序结构的稳定性有密切关系     

C6A4MS与C11A7.CaF2的共存与转化关系研究

本文详细研究了C6 A4 MS与C11 A7.CaF2的共存与转化条件。结果表明：C11 A7.CaF2含量较高时能够抑制C6 A4 MS的形成，含量较低时则能与C6 A4 MS共存；升高温度能够消除C11 A7.CaF2对C6 A4 MS的形成的影响；C11 A7.CaF2能与合成矿物C6 A4 MS共存。，The coexistence and transformation condition between C6 A4 MS and C11 A7 . CaF2 is studied in detail in this paper. The results shows that C11 A7 . CaF2 can restrain the formation of C6 A4 MS when in higher content, but It can coexist with C6 A4 MS when its concentration is lower. Increasing temperature can avoid the effect of C11 A7 . CaF2 on the formation of C6 A4 MS. C11 A7 . CaF2 can coexist with syntheitical mineral C6 A4 MS.     

Numerical solution to the solidification of aluminium in the presence of various fibres

In an attempt to understand the experimentally observed solidification microstructures in metal matrix composites, the influence of SiC, graphite and alumina fibres on the solidification of aluminium has been studied numerically. Irregular geometries of the composite material were mapped into simple rectangles through numerical conformal mapping techniques to analyse the influence of a single fibre or a row of fibres on a unidirectionally advancing planar solid-liquid interface. The fibres were assumed to be circular in cross-section and the direction of the interface movement was perpendicular to the length of the fibres. The study showed that for fibres with lower thermal conductivity than aluminium, the interface first goes through acceleration as it approaches and ascends the fibre and then deceleration as it descends the fibre. The acceleration and deceleration phenomena of the interface increases as the thermal conductivity ratio of fibre to liquid aluminium decreases. With low thermal conductivity ratios (K _f/K _L1), the interface is orthogonal to the fibre surface. When the conductivity of the fibre is lower than that of the melt, the interface becomes convex facing the fibre; this mode would lead to pushing of the fibre ahead if it was free to move, as has been experimentally observed in cast microstructures of metal matrix composites. The temperature versus solidification time plots of two points, one in the fibre and the other in aluminium, show that the fibre with a conductivity lower than the matrix is at a temperature higher than the melt; the temperature difference between the two points increases with increasing solidification rate for all the positions of the interface before it touches the fibre. The three-fibre study shows that as the number of fibres increases, the curvature of the interface increases upon approaching the subsequent fibres. The relationship between these numerical computations and experimental observations has been discussed.Nomenclature a reference length = diameter of the fibre - h - K thermal conductivity; in Equation 4 it is defined as K = (K + K _f)/2 for the common boundary between fibre and the freezing medium. For all the rest of the points K = K in Equation 4 - L latent heat of fusion - r non-dimensional variable in radial direction - S non-dimensional distance travelled by the interface - Ste Stefan number = - T non-dimensional temperature - t non-dimensional time - x a non-dimensional spatial coordinate of physical plane - y a non-dimensional spatial coordinate of physical plane - thermal diffusivity - non-dimensional axial coordinate of the mapped plane - non-dimensional vertical coordinate of the mapped plane - a polar coordinate - l liquid - m melting - s solid - O constant wall temperature - i initial - f fibre - * dimensional variables     

关于用多项式的单调序列逼近

本文证明,如果f∈C[0,1]不是多项式,则有n次多项式Pn(x)与Qn(x)使得在[0,1]上Qn(x)相似文献   

Modelling a Plunging Breaking Solitary Wave with Eddy-Viscosity Turbulent SPH Models

Breaking waves can run up at the shoreline, inundating coastal regions and causing large property damage and loss of life. In order to proceed to the design of sea defence structures and estimate the possible damage resulting from sea submersion due to a tsunami for instance, it is thus crucial to understand these phenomena. However, due to the mathematical difficulties caused by the complexities of the fluid motion associated with breaking wave, a fully theoretical approach is not possible. Thus most of the investigations regarding breaking waves are experimental and numerical. Some methods were recently developed to perform such simulations, among them Volume Of Fluids (VOF) and Lagrangian methods. In this paper, the gridfree Smoothed Particle Hydrodynamics (SPH) is used. SPH is preferencially used in CFD to simulate complex flows with one or several convoluted free surfaces. Indeed, this type of flows would require distorted meshes with Eulerian finite difference methods or very fine meshes with VOF. The ability of SPH to reproduce a plunging breaking solitary wave and to simulate the different stages of its process is herein investigated. Since breaking waves are characterised by high distorsion, turbulence modelling plays a crucial role in such simulations. Therefore, the turbulence models developed by the authors and presented in earlier publications [\relax \begingroup \catcode `\ 12\relax \catcode `\\12\relax \catcode `\$12\relax \catcode `\&12\relax \catcode `\#12\relax \catcode `\^12\relax \catcode `\_12\relax \catcode `\%12\relax \catcode `\~12\relax \endgroup \relax \cite *{dv_ri:2006}] are here applied. The results, compared to experiments, are on the whole satisfactory, specially the simulation of the splashup phenomenon. Moreover, it is shown that turbulence modelling has a strong influence on the quality of the results.