几种行之有效的液压系统故障诊断方法

给出了大型装备液压系统故障诊断的一般步骤,列举了直接诊断法、原理诊断法、因果图法等几种实用的故障诊断方法。     

Fuzzy adaptive networks in machining process modeling: surface roughness prediction for turning operations

Due to the complexity of the machine tool structure and the cutting process, the dynamics of machining processes are still not completely understood. This is especially true due to the demand of high-speed machining to increase productivity. In order to model and control these complex processes, new approaches, which can represent complex phenomenon combined with learning ability, are needed. The combined neural–fuzzy approach appears to be ideally suited for this purpose. In this paper, the recently developed fuzzy adaptive network (FAN) is used to model surface roughness in turning operations. The FAN network has both the learning ability of neural network and linguistic representation of complex, not well-understood, vague phenomenon. Furthermore, it can continuously improve the initially obtained rough model based on the daily operating data. To illustrate this approach, a model representing the influences of machining parameters on surface roughness is established and then the model is verified by the use of the results of pilot experiments. Finally, a comparison with the results based on statistical regression is provided.     

Deformation and failure mechanism of nano-composite coatings under nano-indentation

Two nano-composite coatings based on nc-TiC particles in an a-C:H matrix are deposited via closed-field unbalanced reactive magnetron sputtering. The compositions of the coatings are varied by changing the acetylene gas flow during the depositions. A Cr/Cr–Ti/Ti–TiC graded interlayer is introduced between substrate and coating. Electron probe micro-analyses (EPMA) show that the Ti content of the coatings varies between 31.7 and 11.5 at.%. The coatings exhibit a hardness (H) of 20.0 and 15.7 GPa, and a Young's modulus (E) of 229.4 and 136.6 GPa, respectively, as measured through nano-indentations. Cube corner indentations are performed to probe the fracture toughness of the coatings through the determination of critical indentation loads (L_r) at which radial cracks start to propagate. Transmission electron microscopy (TEM) observations and energy-filtered TEM are employed to characterize the coatings nanostructures. The variation in Ti content is accompanied by a variation in TiC particle size and volumetric fraction, as well as a change in the columnar structure of the coatings. A focus ion beam (FIB) slicing technique is employed to prepare samples from nano-indented locations of coated Silicon and stainless steel (SS) substrates. TEM inspection of the FIB sliced samples determines that the most brittle phase in the coating is the C-enriched columnar boundary, and identifies the location of failure within the interlayer. As a consequence of the different nanostructure, the coatings exhibit different elastic recovery properties and toughness.     

Microstructure and properties of TiB/Ti-6Al-4V coatings produced with laser treatments

TiB/Ti-6Al-4V metal-matrix composite (MMC) layers were produced on Ti-6Al-4V substrates by laser cladding. A TiB₂/Ti powder mixture was used as a precursor to obtain a dispersion of TiB needles in the Ti alloy matrix, with the aid of an exothermic reaction between TiB₂ and Ti. A eutectic microstructure was obtained that consisted of an extremely homogeneous dispersion of TiB eutectic needles in the Ti alloy matrix, having a volume fraction as high as 0.33. Also, an equilibrium-like microstructure was found, consisting of a dispersion of both primary and eutectic TiB needles inside the Ti alloy matrix. An analysis of the geometry of the layers was performed and proved successful in determining the percentage of B. Further, it correctly predicted the variation of atomic B content as a function of laser power. The relative wear resistance coefficient, defined as the wear coefficient of the uncoated matrix divided by that of coating, shows an improvement by a factor as high as 1500 for the eutectic microstructure. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana, and appeared on pp. 411–18 of the Proceedings.     

Gas chromatographic thermodynamics on hydration processes of magnesium chloride with low water

1　INTRODUCTIONMagnesiumchlorideisabasicmaterialforchem icalindustry ,andithaswideapplicationsinmetallur gy,architecturalmaterialandtextileindustry .Itisalsoamaterialforfire resistantproducts ,cryogenandcompoundfertilizerproductions[1] .Thefullydehy dratedmagnesiumchlorideisagoodmaterialforelec trolyticmetalmagnesium production .Becausemag nesiumchloridehasastrongadsorptiveability ,itisalsousedasadryingagent .Manysuccessfulworkshavebeendoneonthedehydrationofbischophite[2 10 ] .Butinfact,…     

AB_5型贮氢合金P－C关系的人工神经网络研究

本文利用人工神经网络方法研究了ＡＢ５型贮氢合金的Ｐ－Ｃ曲线、平台宽度和平台压力等，并取得了满意的结果，表明人工神经网络可用于贮氢材料的设计     

Fine grinding of silicon wafers: a mathematical model for the chuck shape

Fine grinding of silicon wafers is a patented technology to manufacture super flat semiconductor wafers cost-effectively. Two papers on fine grinding were previously published in this journal, one discussed its uniqueness and special requirements, and the other presented the results of a designed experimental investigation. As a follow up, this paper presents a study aiming at overcoming one of the technical barriers that have hindered the widespread application of this technology, namely, the difficulty and uncertainty in chuck preparation. Although the chuck shape is critically important in fine grinding, there are no standard procedures for its preparation. Furthermore, the information on the relation between the set-up parameters and the resulting chuck shape is not readily available. In this paper, a mathematical model for the chuck shape is first developed. Then the model is used to predict the relations between the chuck shape and the set-up parameters. Finally, the results of the pilot experiments to verify the model are discussed.     

Oxidation of Si-based ceramics in the presence of alkali halide vapors

Nonoxide silicon-based ceramics owe their oxidation resistance to the formation of a thin silica film that separates the ceramic from oxidizing environments. This silica film can be fluxed by alkali oxides to form low-melting alkali silicate corrosion products that do not provide protection. Alkali chlorides and other halides have sufficiently high vapor pressures that silica fluxing can occur without the formation of a condensed halide salt. The rates of oxidation of Si, SiC, and Si₃N₄ are influenced by the composition of gas mixtures containing these species.     

纳米热喷涂技术的研究现状与展望

介绍了纳米热喷涂结构涂层的组装、涂层结构与性能等方面的研究现状，并展望了纳米热喷涂技术的发展前景。     

含B2O3渣系的热力学计算模型

根据炉渣结构的共存理论和相图，推导了ＣａＯＢ２Ｏ３和ＦｅＯＦｅ２Ｏ３Ｂ２Ｏ３渣系的热力学计算模型。结果表明：（１）理论计算的ＣａＯＢ２Ｏ３渣系的作用浓度ＮＣａＯ及ＮＢ２Ｏ３与实测的活度ａＣａＯ及ａＢ２Ｏ３一致；（２）理论计算的ＦｅＯＦｅ２Ｏ３Ｂ２Ｏ３渣系的氧化能力ＮＦｅｔＯ与实测的炉渣ＦｅｔＯ的活度值相符合。这说明本文提出的热力学计算模型是合理的。