共查询到20条相似文献,搜索用时 78 毫秒
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高波阻抗层下多层低波阻抗层间脱粘的超声检测问题是具有普遍意义又很难解决的检测问题,本文介绍了我们近年来在些方面的一些研究进展,首先从传播特性入手总结出几个有用的特征规律,并结合这些物理特征规律选取相应的信号处理手段,从方法上实现多层界面的脱粘检测,并作了多种技术集成,做出有实际应用价值的检测系统。 相似文献
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粘接界面特性的超声检测与评价既是物理学的前沿问题,又是经济建设和国防安全亟需解决的应用问题。高波阻介质下多层低波阻介质界面脱粘检测、滑移界面检测和粘接强度定量评价是粘接质量检测中遇到的三大难题。本文综述了课题组十余年来在攻坚三大难题方面的研究工作:建立了共振匹配理论,发明了六项关键技术并实现了技术集成,研制出全新概念的超声检测设备,解决了第一个难题;成功研制出横波直探头,用纵横波综合判断方法解决了第二个难题;对第三个难题,建立了粘接界面非线性弹簧模型,为利用非线性声学参量评价粘接界面奠定了理论基础,并探索性地利用统计性方法对粘接强度进行了预测,取得较好效果。 相似文献
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开展了复合材料粘接结构粘接质量的非接触式超声反射特性的仿真与实验研究。首先,建立了水浸环境下纤维增强复合材料(FRP)单层板时域仿真模型,数值分析了不同入射角度下声反射系数频率谱的变化规律,并与已有理论方法进行了对比验证。基于此,建立了含厚胶层的复合材料粘接结构反射特性时域仿真模型,分析了粘接界面弱化程度对超声反射系数频谱特征点的影响规律。基于水浸超声反射特性测量系统,实验萃取了完好粘接状态的FRP粘接结构的超声反射系数频谱,与仿真结果吻合良好。随后,制备了具有不同粘接界面状态特征的FRP粘接结构试样,从实验角度揭示了单/双粘接界面弱化状态与超声反射特性间规律性的偏移特征。基于不同粘接状态与超声反射特性间的规律性分布特征,可为厚胶层复合材料粘接结构的粘接质量评估提供新的研究思路。 相似文献
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Ti扩散铌酸锂光波导特性的热固定技术 总被引:1,自引:1,他引:0
在Ti扩散铌酸锂光波导中,因光致折变效应而导致光波导特性漂移.在光波相干性的导波光学器件中,光致折变效应的影响尤为严重.本文报道了稳定光致折变效应的热固定技术实验结果;并提出在光波导特性的热固定过程中,不是H~+离子起主导作用这一看法. 相似文献
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应用大规模分子动力学方法, 模拟了具有不同原子级粗糙形貌的两种刚性球形探头与弹性平面基体的黏附接触行为. 研究了载荷与真实接触面积、接触界面排斥力与真实接触面积, 以及黏附力与真实接触面积之间的关系. 分子模拟得到的载荷与真实接触面积的关系, 与连续力学接触理论预测很好地定性一致. 无论是原子级光滑探头还是粗糙探头, 黏附接触下的排斥力与真实接触面积的关系, 都与无黏附接触时的规律相一致, 即黏附力对接触行为的影响作用, 可以等效为附加在真实外载荷基础上的虚拟载荷, 将对黏附接触行为的分析转变为无黏附接触分析. 两种探头的黏附力随真实接触面积都呈幂函数形式的增长, 但是, 原子级光滑探头的幂指数大于1, 而原子级粗糙探头的幂指数小于1.
关键词:
接触行为
表面黏附
分子动力学模拟 相似文献
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The paper proposes a general procedure to find the form of the gauge fixing term in the extended BRST quantization of the gauge theories, a difficult problem in the standard approach. Our proposal is based on the many level structure of the extended spaces and leads to a simple form of the gauge fixing term. The abelian 2‐form model is completely analyzed as an example. 相似文献
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随着红外技术的发展,在其光学系统中,锗材料的应用日趋地多。大口径锗材料在应力、均匀性和作为光学零件要求的精度上,对加工者都有一定难度。本文介绍了目前国内口径最大(Φ256mm)的多晶透镜的加工方法。从零件的特点及技术要求到加工工艺、磨具选择、抛光机理等均有叙述及分析。最后,提出进一步改进加工工艺的设想。 相似文献
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Shear-Horizontally (SH) polarized, ultrasonic, guided wave modes are considered in order to infer changes in the adhesive properties at several interfaces located within an adhesive bond joining two metallic plates. Specific aluminium lap-joint samples were produced, with different adhesive properties at up to four interfaces when a glass–epoxy film is inserted into the adhesive bond. EMAT transducers were used to generate and detect the fundamental SH0 mode. This is launched from one plate and detected at the other plate, past the lap joint. Signals are picked up for different propagation paths along each sample, in order to check measurement reproducibility as well as the uniformity of the adhesively bonded zones. Signals measured for four samples are then compared, showing very good sensitivity of the SH0 mode to changes in the interfacial adhesive properties. In addition, a Finite Element-based model is used to simulate the experimental measurements. The model includes adhesive viscoelasticity, as well as spatial distributions of shear springs (with shear stiffness KT) at both metal–adhesive interfaces, and also at the adhesive–film interfaces when these are present. This model is solved in the frequency domain, but temporal excitation and inverse FFT procedure are implemented in order to simulate the measured time traces. Values of the interfacial adhesive parameters, KT, are determined by an optimization process so that best fit is obtained between both sets of measured and numerically predicted waveforms. Such agreement was also possible by adjusting the shear modulus of the adhesive component. This work suggests a promising use of SH-like guided modes for quantifying shear properties at adhesive interfaces, and shows that such waves can be used for inferring adhesive and cohesive properties of bonds separately. Finally, the paper considers improvements that could be made to the process, and its potential for testing the interfacial adhesion of adhesively bonded composite components. 相似文献
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《Current Applied Physics》2014,14(1):118-121
In this paper, we introduce methods which can effectively enhance the adhesion between polyphenylene sulfide (PPS) and bulk Cu. One of the methods involved the thermal evaporation of PPS to form a buffer layer on Cu and the other involved plasma treatment with reactive gases such as O2, H2, and N2 on the PPS buffer layer. The adhesion strength of samples prepared by PPS thin film coating (∼26 MPa) was largely enhanced when compared to that of samples obtained by only etching (∼15 MPa). Among the samples obtained by plasma treatment using various reactive gases, the samples treated using H2 plasma showed the best adhesion strength (of ∼32 MPa) in comparison to the other samples owing to the adhesion between hydrophobic surfaces. 相似文献
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The strength of cell adhesion is important in understanding the cell’s health and in culturing them. Quantitative measurement of cell adhesion strength is a significant challenge in bioengineering research. For this, the present study describes a system that can measure cell adhesion strength using acoustic streaming induced by Lamb waves. Cells are cultured on an ultrasound transducer using a range of preculture and incubation times with phosphate-buffered saline (PBS) just before the measurement. Acoustic streaming is then induced using several Lamb wave intensities, exposing the cells to shear flows and eventually detaching them. By relying upon a median detachment rate of 50 %, the corresponding detachment force, or force of cell adhesion, was determined to be on the order of several nN, consistent with previous reports. The stronger the induced shear flow, the more cells were detached. Further, we employed a preculture time of 8 to 24 h and a PBS incubation time of 0 to 60 min, producing cell adhesion forces that varied from 1.2 to 13 nN. Hence, the developed system can quantify cell adhesion strength over a wide range, possibly offering a fundamental tool for cell-based bioengineering. 相似文献
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Yan-Huai Ding Ping ZhangHu-Ming Ren Qin ZhuoZhong-Mei Yang Xu JiangYong Jiang 《Applied Surface Science》2011,258(3):1077-1081
Surface adhesion properties are important to various applications of graphene-based materials. Atomic force microscopy is powerful to study the adhesion properties of samples by measuring the forces on the colloidal sphere tip as it approaches and retracts from the surface. In this paper we have measured the adhesion force between the colloid probe and the surface of graphene (graphene oxide) nanosheet. The results revealed that the adhesion force on graphene and graphene oxide surface were 66.3 and 170.6 nN, respectively. It was found the adhesion force was mainly determined by the water meniscus, which was related to the surface contact angle of samples. 相似文献