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21.
Theoretical analyses for the single fibre pull-out and push-out models under monotonic loading are given which are based on a shear-lag analysis in a fracture mechanics approach considering non-constant friction at the debonded interface as a result of fibre Poisson contraction (or expansion). The solutions allow the determination of typical fibre/matrix interfacial properties such as the interfacial fracture toughness, Gic, the coefficient of friction, μ, and the residual clamping stress, q0. Under cyclic loading the interfacial properties are expected to degrade as a result of repetitive abrasion, and a power law function is assumed between μ and the number of elapsed cycles, N. However, Gic is assumed to be unaffected and a fracture mechanics based debond criterion is derived for the relationship between the external applied stress, the debond length and the reduced friction coefficient for both fibre pull-out and fibre push-out. In addition, the relative displacements between the free fibre end and the matrix top are obtained for cyclic fatigue when the fibre is loaded and unloaded. A relationship obtained for the protrusion (or intrusion) length in fibre pull-out (or push-out) experiments allows the severity of the interface frictional degradation to be evaluated and characterised. Similarities and differences in the frictional degradation behaviour between fibre pull-out and push-out are also identified. 相似文献
22.
多孔粒状铵油炸药在边坡预裂爆破中的应用 总被引:3,自引:0,他引:3
通过工程实践,介绍了利用多孔粒状铵油炸药进行边坡预裂爆破的设计原理及施工工艺。该技术能确保预裂爆破质量。简化施工工序,大幅度降低爆破成本。技术经济指标优越。 相似文献
23.
A. Cravino P. Leriche O. Alvêque S. Roquet J. Roncali 《Advanced materials (Deerfield Beach, Fla.)》2006,18(22)
The cover image illustrates the dual photovoltaic and electroluminescence function of a single‐layer device based on a thienylenevinylene–triphenylamine with internal charge transfer (ICT), as reported by Cravino, Roncali, and co‐workers on p. 3033. The material forms an organic glass with isotropic electronic properties while ICT leads simultaneously to an extension of the photoresponse to the red and to an increase of the open circuit voltage. The use of an additional layer of C60 further improves the photovoltaic. Images of the sun and moon courtesy NASA/JPL–Caltech. 相似文献
24.
S. H. Ahmad 《Polymer International》1992,28(4):291-294
Measurement of the flow stress of high density polyethylene (HDPE) and nylon 66 at strain rates of 103 s?1 using a split Hopkinson pressure bar technique is discussed. The flow stress at a strain of 10% has been determined for both polymers at 20°C. The intrinsic errors involved in this technique are briefly reviewed. The results indicate that the flow stress of HDPE and nylon 66 were 50MPa and 150MPa, respectively, at strain rates of about 103s?1. 相似文献
25.
26.
Per Axel Clausen 《Indoor air》1993,3(4):269-275
A waterborne paint was applied to tin plated steel sheets with three different film thicknesses. The emission of volatile and semivolaile organic compounds ((S) VOCs) from the samples was measured in small climatic chambers under standard conditions over a two-week period. The purpose of the study was to evaluate the effect of the film thickness on the emission rate decay. First order decay models, including sink effects for the high boiling (S) VOCs, were fitted to the concentration versus time data. The results showed that the first order rate constants decrease with increasing film thickness. In uddition, the results indicated that the emissions of the (S)VOCs in the waterborne paint film seemed to be controlled by evaporation. The thicknesses of paint films used in climatic chamber tests to estimate emission rates for product compurison or emission prediction must be known in order to prevent erroneous conclusions 相似文献
27.
28.
G.Y. Sha F.C. Jiang D. Wang D.K. Liu and R.T.Department of Mechanical Engineering Harbin Engineering University Harbin ChinaShenyang National Laboratory for Materials Science Institute of Metal Research The Chinese Academy of Sciences Shenyang China 《金属学报(英文版)》2002,15(6):556-560
An experimental-numerical method for measuring dynamic crack propagating velocities under stress wave loading is established in this paper. The experiments of the three-point bend specimen are done on the improved Hopkinson bar. Deflection of loading point, dynamic load and instantaneous crack length are measured, then crack propagating velocities are calculated. Experiments on 40Cr steel show that the results given by this method have a good agreement with that obtained by the resistance fracture gage method. Therefore this method is feasible for measuring crack propagating velocities under high loading rate and will have wide application. 相似文献
29.
Fenton试剂处理苯酚和甲醛废水的研究 总被引:5,自引:0,他引:5
用H2O2同Fe^2 结合的Fenton试剂处理有机废水是一种经典的催化氧化法,这种方法适合于处理废水中高浓度、难降解的有机物质。主要研究了Fenton试剂处理含苯酚和甲醛有机废水样的反应机理和影响因素,试验结果表明:废水中苯酚和甲醛的去除率均可达到95%以上,COD去除率达到85%以上,表明用Fenton法处理含苯酚和甲醛的有机废水是一种非常有效的方法。 相似文献
30.
Degree of crosslinking and mechanical properties of crosslinked poly(vinyl alcohol) beads for use in solid-phase organic synthesis 总被引:1,自引:0,他引:1
The limited swellability in polar media of the commonly used polystyrene/divinylbenzene (PS-DVB) support materials for solid-phase organic synthesis has led to the development of novel, highly swellable hydrophilic gels designed for use in aqueous or polar media. Poly(vinyl alcohol) beads crosslinked with epichlorohydrin (PVA-EP) were prepared by a two-step inverse-suspension polymerization method. While it is known that the morphology of the resulting beads can be controlled by the ratio of EP versus PVA as well as by the pre-crosslinking time, the actual degree of crosslinking of the beads and their mechanical properties remain unknown. It is therefore the purpose of this study to evaluate the actual degree of crosslinking of beads prepared with different quantities of crosslinker in the feed by spectroscopic (Raman, nuclear magnetic resonance) and chemical (functional group loading) methods. The mechanical properties of these swollen PVA-EP beads will be evaluated by single-bead unconfined compression in solvents such as water, N,N-dimethylformamide (DMF), and tetrahydrofuran (THF) and compared to model PS-DVB beads commonly used for solid phase synthesis. 相似文献