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1.
钢-混凝土结构是土木工程中的一种常用结构形式,钢与混凝土粘接处可能出现弱粘接甚至完全脱粘的缺陷,严重影响结构的安全性。该文提出利用空气耦合超声导波衰减的方法实现钢-混凝土结构粘接状态的非接触无损检测方法,分析不同厚度粘接界面对超声导波衰减的影响。基于全局矩阵技术对钢-混凝土结构求解理论频散方程和衰减曲线,得到界面层不同粘接条件下的理论参数及衰减特性。建立不同粘接条件的有限元模型,定量分析不同模态对粘接缺陷的检测敏感度。研究界面层厚度分别为1 mm和2 mm两种情况下S0能量的衰减情况。研究结果表明:S0模态可有效判断粘接结构的粘接状态,对于同一界面层厚度,随着界面粘接条件变弱,S0最大幅值与A0最大幅值比不断增大;不同厚度同一粘接条件下,2 mm相较于1 mm该值更大。该方法在钢-混凝土结构粘接界面缺陷的检测方面具有良好的应用价值和发展前景。  相似文献   

2.
针对多层异种金属粘接结构中粘接强度的超声检测与表征困难的问题,采用线性弹簧模型和等效弹性模量模型来分别表征界面粘附强度和内聚强度,推导了超声体波斜入射N层粘接结构的反射与透射系数表达式。通过在不同入射面和入射声波模式等条件下,同时连续改变两种参数来系统研究粘接层界面粘附强度与内聚强度变化对超声波反射与透射特性的影响关系,确定了能够敏感表征粘接强度的超声参量,为粘接强度的无损检测与评价提供理论依据。  相似文献   

3.
为了解粘接结构中胶粘涂层的粘弹特性,进而评价粘接质量,对半无限金属基底-胶粘涂层结构涂层中的类Rayleigh波传播特性进行了研究。从粘弹的基本理论出发,通过Laplace-Henkel变换技术建立起类Rayleigh波的频率方程,将粘接涂层视为Kelvin体计算并分析了其粘弹模量对波的频散及衰减关系的影响。理论计算发现粘弹体的粘滞项对频散低阶模式影响不大,但随着粘滞的增大对高阶模式可产生影响。同时粘滞还影响各阶模式波的衰减,特别是Sezawa模式对衰减较Saw模式更为敏感,在某些结构中还会出现局部的极小值现象,结果表明:对粘涂层结构涂层中类Rayleigh波传播特性的研究可为粘弹模量的定量评估及粘接质量的评价提供一定的理论方法。  相似文献   

4.
刘婧  徐卫疆  胡文祥 《物理学报》2016,65(7):74301-074301
在用超声波谐振对粘接材料的粘接强度进行无损评估时, 不同模式对粘接强度的敏感程度受到众多因素和参数的影响, 对检测结果的可靠性至关重要. 基于多层介质中声传播和界面弱粘接边界条件的理论模型, 将一个上下非对称的金属-粘接剂-金属三层结构的平面波反射系数函数中的谐振模式看作是上下铝金属层各自的Lamb波频散模式通过夹心粘接剂层相互耦合后叠加组成. 改变影响结构粘接强度的因素, 即粘接剂的性能参数(声阻抗、密度、厚度)和界面切向劲度系数kt来分析三层结构谐振模式耦合方式的变化,得出结论: 粘接结构粘接性能的变化基本上不改变与被粘铝层相关的固有部分的Lamb波模式, 而它们的耦合模式则在谐振频率上产生平移并会与固有模式进行交换和替代; 不同参数的变化引起的模式演变有各自的规律, 大多可彼此区分.  相似文献   

5.
采用双高斯脉冲反卷积滤波技术对太赫兹时域波形进行滤波优化,提出一种基于太赫兹时域光谱无损检测的太赫兹反射式层析成像技术,用于分析玻璃纤维蜂窝复合材料的粘接质量.结合玻璃纤维蜂窝复合材料结构的特点,分别在蜂窝上层胶膜和下层胶膜中设计了不同直径的圆形和梯形脱粘缺陷,在此基础上,完成了脱粘缺陷蜂窝结构样品的制作.提出的太赫兹反射式层析成像和B-scan成像方法,适用于玻璃纤维蜂窝复合材料的脱粘缺陷分析.针对反射式层析成像图像对比度差的问题,结合脱粘缺陷处的太赫兹时域波形数据特征,采用缺陷特征时间区域成像优化技术,提高了脱粘缺陷的检测能力和识别准确率,实现了玻璃纤维蜂窝材料的上层脱粘厚度50μm、下层脱粘厚度50μm缺陷的太赫兹无损检测.  相似文献   

6.
多层结构中脱粘缺陷的超声检测方法   总被引:3,自引:1,他引:2       下载免费PDF全文
固体火箭发动机多层装药结构中的脱粘类型、位置和尺寸决定了其对整体安全性能构成的威胁程度。该文研究了多层结构中脱粘缺陷的超声检测方法,通过对不同脱粘缺陷超声脉冲回波的特征分析与统计,实现缺陷的定性、定位和定量。首先,采集含有多类脱粘缺陷的粘接结构的超声脉冲回波信号,分析信号中主能量波包所代表的声程,提取五种声程的波峰时刻和幅值作为特征值,组建已知脱粘类型训练样本并输入至BP神经网络,实现特征值域到类别域的非线性映射,即脱粘类型分类;其次,采用阈值法确定缺陷的界面位置;最后,提出分段线性插值-相关性定量法将待检测缺陷的定量结果缩小到±2 mm以内。该文利用COMSOL有限元仿真和实验操作验证了多层粘接结构中脱粘缺陷的定性、定位和定量方法的可行性和可靠性。  相似文献   

7.
超薄层状复合媒质弱界面深度与声导波   总被引:1,自引:0,他引:1       下载免费PDF全文
张锐  万明习  CAO WEN-WU 《物理学报》2000,49(7):1297-1302
结合推导层状复合媒质各界面刚性联接时声导波频散特性方程的传递矩阵方法,以及滑移界 面边界条件和弱界面“弹簧”模型,分别导出了超薄层状复合媒质中存在不同深度弱界面、滑移界面和脱层情况下声导波的广义频散方程,分析了三种联接界面的深度对低模式声导波频散特性的影响. 关键词: 导波 界面 频散  相似文献   

8.
激光激发粘弹表面波特性分析   总被引:2,自引:0,他引:2  
韩庆邦  钱梦 《声学学报》2007,32(4):338-342
研究了粘弹Rayleigh波的传播特性。基于基本粘弹理论,推导出了粘弹Rayleigh波频散方程及位移表述式,探讨了粘弹模量对波频散特性及衰减特性的影响。发现在小粘滞的情况下,粘弹对相速度的影响不大,波的衰减和粘滞模量近似成正比,同样量级的体变粘滞引起的频散及衰减比切变粘滞要小很多。数值上还计算了粘弹Rayleigh瞬态波形,计算结果与理论预言一致。  相似文献   

9.
新型陶瓷纤维复合材料由短切氧化硅纤维及其胶合物经高温烧结得到的一种轻质多孔材料,材料微观结构特性直接影响着宏观结构特性和功能特性。该类材料的孔隙度分布在84%~95%之间,微观孔径主要集中在100 μm范围内,偶尔有少量纳米孔。陶瓷纤维复合材料以其耐高温、低密度、高比强和抗烧蚀等优异性能在超高声速飞行器外层隔热部件得到应用,但该类材料可能因为制作和装配的工艺水平等因素出现夹杂、孔洞甚至大面积脱粘等现象。由于陶瓷纤维复合材料结构与应用场景的特殊性使得常规的无损检测手段效果不佳,而太赫兹(THz)技术作为一种新兴的无损检测技术,在该类材料的无损检测具有很大的潜力,可与常规检测技术形成互补。针对陶瓷纤维复合材料构件粘接层缺陷检测问题,研究了太赫兹时域信号和太赫兹层析成像方式对缺陷定位方法。基于太赫兹时域光谱(THz-TDS)无损检测技术获取和对比试样中有粘接层缺陷和粘接层完好位置的时域波形的波形峰值和相位差异,并经过反卷积滤波技术对时域波形进行处理,定性分析时域波形与粘接层缺陷特性的关系,宏观判断缺陷存在;通过对太赫兹波段陶瓷纤维复合材料光学参数提取测定太赫兹波段的平均折射率为1.028,进而分析粘接层缺陷的深度和厚度分别为18.4和0.28 mm,与预置缺陷真实深度和厚度相比准确度分别为92%和90%。但由于通过时域信号提取的平均折射率会给粘接层缺陷位置分析造成误差,因此以太赫兹层析成像方式进一步估计缺陷的位置,分析了太赫兹层析成像噪声来源以及对成像质量的影响并采用了双边滤波对层析成像降噪滤波,基于太赫兹层析成像技术建立了位置评估模型,获取了粘接层缺陷的厚度为0.26 mm,较预置缺陷厚度的准确度为96%,有效地完善了太赫兹检测技术对缺陷定位的形式,实现了陶瓷纤维复合材料构件的粘接层缺陷的高精度定位表征。  相似文献   

10.
本文利用建立的多层粘接结构超声无损检测信号的卷积模型,推导出了检测信号的解析表达式,并用同态滤波解卷积方法有效地提取出粘接结构的系统响应,进而由其中界面多次反射响应的位置、幅度和包络等特征参数,实现了脱粘二界面(指空气脱粘)的定征和识别。仿真和实验数据的处理结果表明本文方法对脱粘检测的应用有积极的意义。  相似文献   

11.
Copper metallization on LCP was carried out by means of electroless plating followed by electroplating and the effect of pretreatment on the adhesive strength of the Cu-plated LCP was investigated in detail. Compared with the other etching agents used here, potassium permanganate was found to be the most effective and the optimum etching time is 20 min. With potassium permanganate as the etching agent, the adhesive strength could reach 12.08 MPa, which is much higher than the reported maximum adhesive strength (lower than 8.0 MPa). XPS spectra of LCP film indicated that hydrophilic groups were introduced into the LCP surface by etching, creating a nanometer-scale surface roughness and improving the wettability between copper and LCP. SEM and AFM observations revealed that the distinctly increased adhesive strength could be attributed to the improved wetting and the mechanical interlocking effect. The failure mode of Cu-plated LCP film was found to be dependent on the etching time. When the etching time was short, the failure mode of Cu-plated LCP film was mainly adhesive. As the etching time increased, cohesive failure gradually occurred, causing an adhesive/cohesive mixed failure mode.  相似文献   

12.
《Composite Interfaces》2013,20(7):605-621
The interfacial fracture toughness between semi-crystalline polymers (polyamide/polypropylene) were studied to understand the failure mechanisms at the interface, especially when the interface was reinforced by an in situ compatibilizer. Based on the observation of the interface using scanning electron microscopy and wide angle X-ray spectroscopy, it was revealed that crystalline structure of polypropylene was not affected by the in situ compatibilizer at the interface. The reinforcing mechanism could be qualitatively identified by investigating the evolution of fracture toughness as a function of annealing time and temperature. The adhesion strength increased with the annealing time. Depending on the annealing temperature, the fracture toughness passed a peak value and then reached a plateau after some bonding time. As long as the chain length of the compatibilizer is long enough to form entanglements with the molecules at both bulk sides, the fracture at the interface is decided by the balance between adhesion strength at the interface and cohesive strength in the weak modulus side; the failure locus follows the lower one. Thus, adhesive failure occurred first when the reaction at the interface did not occur long enough to provide high adhesive strength at the interface, but the cohesive failure occurred in the crack propagation side after the adhesive strength value became higher than the cohesive strength value.  相似文献   

13.
New superhard coatings based on Ti-Hf-Si-N with good physical and mechanical properties have been fabricated. A comparative analysis of the physical, mechanical, and tribomechanical characteristics of the coatings has been performed. The values of hardness, modulus of elasticity, elastic recovery, adhesive strength, friction coefficient, and wear rate of the coatings have been determined and calculated. The specific features of deformation and fracture of the coatings deposited on a steel substrate during the adhesion tests have been described. It has been shown that the parameters measured during scratching make it possible to distinguish the threshold values of the critical load, which lead to different (cohesive and adhesive) types of failure of the coatings during tribological tests. The stoichiometry for different series of samples with Ti-Hf-Si-N coatings has been determined using Rutherford backscattering, secondary ion mass spectrometry, and energy dispersive microanalysis.  相似文献   

14.
A laser adhesiometer is developed to determine the adhesive and cohesive forces in multilayer materials. The obtained experimental dependences are explained using the laser microexplosion model. The advantages of determining the adhesive and cohesive forces using the laser adhesiometer over other methods are grounded.  相似文献   

15.
Peel test is an efficient method to assess the performance and characteristics of materials such as adhesives and adhesive tapes. Recent experiments evidenced that the measured adhesive strength is closely related to the shear-induced interfacial slippage near the delamination front due to the concomitant Poisson contraction effect of the adhesive. Based on the experimental observations, a theoretical model is presented in this paper to examine the effect of the shear-induced interfacial slippage in the peel test. The influence of the interfacial slippage, represented by the shear displacement in the cohesive zone, on the fracture energy of decohesive zone is analyzed. An implicit expansion method with a Gauss-Chebyshev quadrature scheme is used to derive the solution. It is found that the length of the slippage zone and the receding contact angle of adhesives are the two most significant contributors to the total fracture energy of the decohesive zone. These results demonstrate that the mechanism of interfacial slippage plays a significant role in the adhesion and peeling behaviors of adhesives.  相似文献   

16.
This paper deals with the propagation of ultrasonic guided waves in adhesively bonded lap-shear joints. The topic is relevant to bond inspection by ultrasonic testing. Specifically, the propagation of the lowest-order, antisymmetric a0 mode through the joint is examined. An important aspect is the mode conversion at the boundaries between the single-plate adherents and the multilayer overlap. The a0 strength of transmission is studied for three different bond states in aluminum joints, namely a fully cured adhesive bond, a poorly cured adhesive bond, and a slip bond. Theoretical predictions indicate that the dispersive behavior of the guided waves in the multilayer overlap is highly dependent on bond state. Experimental tests are conducted in lap-shear joints by a hybrid, broadband laser/air-coupled ultrasonic setup in a through-transmission configuration. The Gabor wavelet transform is employed to extract energy transmission coefficients in the 100 kHz 1.4 MHz range for the three different bond states examined. The cross-sectional mode shapes of the guided waves are shown to have a substantial role in the energy transfer through the joint.  相似文献   

17.
《Composite Interfaces》2013,20(2):99-116
The paper describes surface treatment methods to improve adhesion between copper and vinyl ester in glass fiber–vinyl ester composites. Surface treatment methods were developed for commercially available copper that was optimized for epoxies and adhesion performance was compared based on 90° peel strength measurements. Four surface treatments for copper were tested: (i) co-cured Epon/vinyl ester; (ii) fully cured Epon; (iii) epoxy film adhesive; and (iv) γ-MPS silane along with two baseline systems: copper/vinyl ester and copper/epoxy. Measured average peel strengths for the surface treatments were 21%, 101%, 110% and 91% of the baseline copper/vinyl ester system, respectively. Compared to the copper/epoxy system, fully cured Epon, epoxy film adhesive and the silane treatment generated comparable adhesion between copper and vinyl ester. For all samples tested, mixed cohesive/adhesive failure modes were observed. Overall, the surface treatment with the silane coupling agent is the most appropriate method for obtaining comparable and uniform performance compared to copper/glass fiber/epoxy system (FR4 materials).  相似文献   

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