雷达仿真系统中电磁干扰环境的仿真设计和实施

雷达仿真系统是为检测雷达设备的抗干扰能力以及在各种电磁环境下的工作性能而设计的，包括有源干扰和无源干扰的模拟仿真。本文阐述了无源干扰即杂波的散射模型和仿真过程；从同步脉冲干扰的基本原理出发，阐明在雷达工作环境仿真系统中距离拖引、速度拖引、虚假目标等同步脉冲有源干扰的设计和实施过程；并针对工作在搜索和跟踪交替模式下的相控阵雷达提出自适应综合干扰方式；最后分析并总结了系统仿真时为真实、有效地模拟电磁干扰环境应注意的关键问题。     

New and Improved Tests for Adhesion

Three new methods are discussed for measuring the work G_a, required to detach unit area of an adhering material from a substrate. The first is a simple modification of the Outwater double-torsion test for long rectangular plates, bonded together. This method is suitable for evaluating aluminum-epoxy bonds, for example, or the transverse strength of fibrous composites. The second is a pull-off test for long strips adhering to a rigid surface. It seems suitable for adhesive tapes and laminates. The third is a reconsideration of the “blister” test for films and coatings, in which a circular debond at the interface is made to grow by internal pressure. The relation obtained between pull-off force F for a strip, or blow-off pressure P for a layer, takes the unusual form:

F⁴ (or P⁴) ∞ KG³_a

where K is the tensile stiffness of the detaching layer. This dependence arises from the non-linear (cubic) relation between load or pressure and deflection in these configurations. Nevertheless, the product Fθ, where θ is the angle of detachment of a strip, or Py, where y is the height of a “blister”, give direct measures of the strength of adhesion G_a, independent of the stiffness of the adhering material and of the extent of detachment.     

新旧混凝土界面结合状态研究

研究了在不同的界面干湿状态下，几种常见的修补材料和界面剂对新旧混凝土界面结合强度的影响。运用拉拔强度评价新旧混凝土界面结合状态，并借助显微硬度仪测量界面处的显微硬度值对试验结果进行了验证和分析。结果表明，在界面处于不同的干湿状态时，提高新混凝土的强度可使结合强度略有增大。在修补材料中掺入纤维会明显提高界面结合强度，且聚丙烯纤维要优于碳纤维．使用界面剂后界面干湿程度对界面结合强度影响减小。     

锚杆锚固质量检测方法及应用

对锚杆锚固质量的检测一直为工程界所关注,本文比较了拉拔试验与声波反射检测锚杆锚固质量的方法,介绍了两种方法的基本原理以及相关的技术规定。鉴于拉拔试验方法上的不足,详细阐明了声波检测方法及其基本原理,并列举了应用于某高速公路隧道工程检测锚杆锚固质量检测的例子。     

环境湿度下硅材料表面的黏着与黏滑机理

首先采用湿法刻蚀处理硅110面,得到按一定规律排列的圆形、三角形凹坑修饰硅表面;然后在自行开发的微摩擦黏着实验机上,对光滑硅表面和凹坑修饰硅表面在湿度环境下的黏着和摩擦性能进行了测试,发现经过规则形貌修饰的硅表面可以明显地降低由于毛细作用引起的黏着．摩擦力测试中光滑硅表面在湿度超过70％后有明显的黏滑现象,而经过修饰的硅表面对黏滑有抑制作用．在此基础上,从硅表面液桥形成及断裂的角度探讨了环境湿度对黏着与黏滑的作用机理,建立了球面接触模式下不同湿度下的黏着力（pull-off force）与黏滑峰值力的计算模型与公式,并结合实验结果进一步改善了计算模型．可为控制硅袁面的毛细黏着与黏滑提供模型依据．     

拉开法附着力试验测试结果影响因素的探讨

选择若干种油漆样品和若干种底材,按标准方法进行拉开法附着力试验,对试验结果进行了分析比较,并由此探讨了拉开法附着力试验测试结果的影响因素。结果表明底材越粗糙或越厚测试数据越大,样板与试柱对接与否对试验数据的影响略小,底材越厚越坚硬对测试结果影响越小,胶粘剂的粘结力越强,测试数据越大,拉伸速度对测试结果无明显影响。     

Experimental investigations of mechanical and tribological behaviours for organic and inorganic coatings deposited on mild steel substrate

ABSTRACT

Surface treatment technologies are constantly evolving. Increasingly, surface functionalisation is of major concern to lighten structures, improve product performance and reduce costs. To fulfil its decorative and protective functions, it is essential that a coating adheres properly to its support. During the last few decades, many new deposition techniques have been developed and more and more tribological and corrosion resistant coatings have been made available. In this context, the present research has focused on two pneumatically sprayed epoxy/polyamide and inorganic silicate coatings which are deposited on the mild steel substrate. First, the main interest in this study is devoted to the analysis of the coating/substrate adhesion strength by using the squaring and pull-off tests. Second, the study has also focused on the analysis of friction and wear behaviours for the two systems of paint coatings under consideration by using a linear reciprocating tribometer under dry sliding condition. Experimental findings have shown that after appropriate surface preparation and degree of cleaning according to the standard ISO 8501-1, selected paint systems composed of organic or inorganic coatings effectively improve the service life of coated steel. Meanwhile, under the same sliding conditions, the wear results have revealed that the organic coatings have a higher anti-wear ability compared to the inorganic coatings. Thus, both organic and inorganic coatings play an important role in protecting the substrate against severe industrial environment. From the squaring and pull-off analyses, it has been deduced that scratch and pull-off behaviours of both coatings have been severely affected by the surface preparation, the number of protective layers and the thickness of coatings. In fact, the best adhesion, friction and wear properties are obtained for the paint system containing organic coatings where the third body is formed on the entire sliding strip in the test.     

Evaluation of Adhesion Improvement of a GFRP Treated with Atmospheric Plasma Torch

The applications (and repair) of glass fiber reinforced epoxy composites are increasing in different industries (wind turbines, boats, chassis of buses, etc.) due to specific strength and low cost. Their major disadvantage is the difficulty to shape complex components. This problem can be solved manufacturing different parts, being adhesively bonded afterwards. This work studies the effect of atmospheric pressure plasma torch compared to grit-blasting to improve adhesion. After surface treating different parts, the changes of wettability and surface energy were measured. Treated samples were bonded with polyurethane and epoxy adhesives, and the quality of the bond was evaluated using pull-off adhesion tests and fracture strength test under cleavage loads. Obtained results allow to select the most adequate treatment in terms of mechanical requirements.     

纤维聚合物水泥砂浆与基体界面粘结性能研究

通过实验研究钢纤维、聚丙烯纤维、碳纤维等三种不同种类纤维和SBR乳液在单掺、复掺时对新拌砂浆与水泥混凝土基体之间界面粘结强度的影响,寻求适合于混凝土结构修补的新材料。在预先处理的基体表面浇筑不同类型的新拌水泥砂浆,在温度为(20±2)℃,湿度为(60±5)RH%的养护室中养护28d后,测试粘结面的粘结强度,通过粘结强度来反映不同种类纤维和乳液单掺、复掺对新旧水泥基体料粘结效果的影响。同时分析了纤维和乳液对新旧水泥基界面粘结性能作用的机理。研究结果表明,掺量为0.1%的碳纤维砂浆以及掺量不小于0.3%的钢纤维砂浆在复掺SBR(styrene-butadiene rubber)乳液的情况下对界面粘结性能作用效果比纤维、乳液单掺情况下均要好,而聚丙烯纤维与乳液复掺效果不明显。不同种类的纤维砂浆在复掺SBR乳液的情况下,均能有效改善新拌纤维砂浆与基体之间界面结性能,且随着乳液掺量的增加作用效果越好。钢纤维聚合物砂浆和碳纤维聚合物砂浆适用于混凝土结构修补。     

Logarithmic decrease of adhesion force with lateral dynamic revealed by an AFM cantilever at different humidities

Adhesion forces between a tipless cantilever and an Au film were determined to investigate the influence of lateral velocity by recording force curves with an atomic force microscope at 20%–90% relative humidities. The sample was moved laterally, forth and back, with a frequency of 0.001–100 Hz and scan distances of 0.8, 8, and 80 μm to achieve a velocity ranging over 7 orders of magnitude. Experimental results show that at low lateral velocities (between 1.6 nm/s and 1–10 μm/s), the adhesion force either increases or decreases or remains stable with the lateral velocity without a certain characteristic trend. However, after a critical velocity, the adhesion force decreases logarithmically with the lateral velocity (between 1–10 and 16,000 μm/s). The decreasing magnitude can be as large as 97.3% of the maximum adhesion force. This decrease is well-explained by the contact time dependence of water bridges formed by capillary condensation.