Image analysis of atmospheric corrosion of field exposure high strength aluminium alloys

The corrosion morphology image acquisition system which can be used in the field was established. In Beijing atmospheric corrosion exposure station, the image acquisition system was used to capture the early stage corrosion morphology of five types of high strength aluminium alloy specimens. After the denoise treatment, wavelet-based image analysis method was applied to decompose the improved images and energies of sub-images were extracted as character information. Based on the variation of image energy values, the corrosion degree of aluminium alloy specimens was qualitatively and quantitatively analyzed. The conclusion was basically identical with the result based on the corrosion weight loss. This method is supposed to be effective to analysis and quantify the corrosion damage from image of field exposure aluminium alloy specimens.     

合金中痕量元素标准物质研制进展

通过对国内外高温合金、铝合金痕量元素标准物质的比较,评述了我国合金中痕量元素标准物质在种类、量值水平及不确定度等方面的进展。     

Repetitive impact exposure and characterization of stress-whitening of an American football helmet outer shell material

Mechanical stress exerted upon impact-modified polycarbonate (PC) and poly(ethylene terephthalate) (PET) blends has been reported to generate microscopic voids via rubber-toughener (RT) particle cavitation which can macroscopically manifest to visibly whiten the material. Previous work has revealed a whitening phenomenon in collegiate American football helmet outer shells after a single season and in helmet-grade plaques following linear impact testing. The purpose of this research was to quantify the effects of repetitive linear drop exposures on the (i) impact performance; (ii) physical and thermal properties; and (iii) surface and tensile mechanical properties of a stress-whitened American football helmet outer shell material. Statistically significant changes in plaque impact performance corresponded to substantial stress-whitening that penetrated up to 40–45% into the plaque thickness and elicited shifts in surface and tensile mechanical properties. Nanoscale microscopy revealed elongation of the PC/PET matrix and delamination at the RT-matrix interface. Thermal property analysis suggested the concomitant occurrence of RT cavitation and strain-induced PET crystallization. Overall, the research identified a battery of diagnostic tools to characterize material property changes of stress-whitening in rubber-toughened helmet outer shell materials.     

Miscanthus stem fragment – Reinforced polypropylene composites: Development of an optimized preparation procedure at small scale and its validation for differentiating genotypes

The production of ligno-cellulosic biomass-based composites requires the development of new methodologies to evaluate the reinforcement potential of a given biomass, such as miscanthus studied in the work. Miscanthus stems from thirteen genotypes were broken into elongated fragments and mixed with polypropylene composites in an internal mixer. The aim is to find the best protocol able to discriminate miscanthus genotypes for their reinforcement capability. The following process parameters were optimized in order to maximize the reinforcement effect of the stem fragment filler: mixing parameters (mixing time, rotor speed and chamber temperature), temperature, fragment content, size and length distributions and coupling agent. The relationship between the process parameters and the mechanical properties of composites were analyzed to evaluate the influence of genotype on reinforcement performance, showing the robustness of the protocol in effectively discriminating genotypes according to their reinforcing capacity.     

Enhanced coercivity in sponge magnets with three dimensionally ordered nanopores

Nanoporous magnets are new promising materials particularly useful in biological assays and ion separations. This letter deals with a simple method for making porous magnets composed of cobalt ferrite, where polymer colloidal spheres were used as sacrificial templates. Compared with the bulk congener the porous cobalt ferrite shows enhancements in coercive field and magnetization, which could be associated with the presence of nanopores ordered three dimensionally. Using the sponge magnet complete removal of magnetic Cu and Fe ions was achieved while partial removal was observed with porous silicate having the same size of nanopores.     

Au基合金电位器材料耐磨特性与显微组织关系的研究

一种新型的由Ａｕ－Ｎｉ－Ｆｅ－Ｃｒ－Ｉｎ－Ｚｒ六元合金绕组材料与Ａｕ－Ｎｉ－Ｉｎ合金表面Ｉｎ＋注入的电刷材料相匹配制成的航空电位器,使用寿命为１×１０６次,达到ＨＢ５６３３－８１规定的一级电位器水平．力学性能研究和微观组织分析表明,电刷材料Ａｕ－Ｎｉ－Ｉｎ合金表面Ｉｎ＋注入可以促使表层生成具有良好润滑性能的Ｉｎ２Ｏ３,这能降低摩擦因数,并且可以使材料的表层组织晶粒细化,晶格畸变,从而提高表层的强度和硬度,改善其摩擦和磨损性能．在绕组材料Ａｕ－Ｎｉ－Ｆｅ－Ｃｒ－Ｉｎ－Ｚｒ六元合金的显微组织中,除有Ａｕ基固溶体和Ｎｉ基固溶体外,还含有Ｎｉ５Ｚｒ新相和具有正交结构的未知相这２种第２相粒子．存在于磨损表面的第２相粒子能够有效地提高绕组材料的抗粘着磨损能力．航空电位器的长使用寿命,是电刷材料和绕组材料的多种抗磨因素综合作用的结果．     

Stress intensity factors for corner cracks at a hole under remote tension

The three-dimensional weight function method recently developed by the authors is used to determine stress intensity factors for two symmetric quarter-elliptical corner cracks at a hole in a wide finite-thickness plate subjected to remote tensile loading. The geometry parameters considered arer/t=0.5, 1, 2;a/c=0.2, 0.5, 1, 2;a/t=0.2, 0.5 withinc/r=2. The results are compared, where possible, with other solutions available in the literature. Generally good agreement is observed. The effect of an approximation of the two-dimensional unflawed stress distribution on the accuracy of stress intensity factors by the weight function method is discussed.     

无水坝抽水蓄能系统高压溶气问题研究

无水坝抽水蓄能系统利用封闭容器内的高压气体构建虚拟水坝,是兼具压缩空气储能和抽水蓄能优点的新型储能系统。但该系统的封闭容器内水和气在高压状态共存有可能造成水中溶气,从而对水轮机造成汽蚀等破坏。本文采用实际气体状态方程及分子动力学模拟方法,研究了宽广的压力、温度范围下气体在水中的溶解及扩散规律,揭示了水中气体溶解量随时间和水深的变化规律。研究结果表明释能结束后保证水-气共容舱内剩余水的高度大于0.5 m时,高压溶气不会对水轮机产生危害,该结论对系统的工程应用及推广具有指导意义。     

Super-thin cloaks mediated by spoof surface plasmons

We demonstrated the possibility of designing super-thin electromagnetic cloaks based on spoof surface plasmon (SSP). Using a metamaterial layer, incident waves can be coupled into SSP efficiently at the air/metamaterial interface. Due to the strong surface confinement of SSP, EM waves are squeezed into and propagate in deep sub-wavelength scales. Implementation of an 8.2 GHz cloak less than 1/50 the cloaking diameter was presented using split ring resonator (SRR). Excellent cloaking effect was verified by simulations. Rather than isolating objects from the background, such cloaks can drastically enhance the field intensity around the cloaked object. This is of particular importance in applications such as weak wave detection and near-field sensing.     

Internal Deformation Measurement and Force Chain Characterization of Mason Sand under Confined Compression using Incremental Digital Volume Correlation

The mechanical behavior of granular materials such as sand is not well understood due to its complex solid/fluid-like behavior. In this paper, Mason sand was investigated to determine the grain-level Young’s modulus and hardness by nanoindentation, and the mesoscale behavior through X-ray tomography of a sample in compression. Mason sand specimen was confined in a polycarbonate tube and compressed in the axial direction at ten axial compressive strains up to -21.8 % while its microstructures were observed. The mesoscale deformations were determined by incremental digital volume correlation of reconstructed volumetric images. A procedure for characterization of internal force chains is developed. The minor principal strains and their principal directions were obtained and used to determine the formation and evolution of force chains.