Characteristics of the interface of a laser-quenched steel substrate and chromium electroplate

The interface of a laser-discrete-quenched steel substrate and as-deposited chromium electroplate was investigated by ion beam etching, dissolving-substrate-away and using a Vickers microhardness tester, in an attempt to reveal the mechanism that the service life of the chromium-coated parts is increased by the duplex technique of laser pre-quenching plus chromium post-depositing. The laser quenching of the steel substrate can reduce the steep hardness gradient at the substrate/chromium interface and improve the load-bearing capacity of chromium electroplate. Moreover, the laser quenching prior to plating has an extremely great effect on the morphologies and microstructure of the substrate/chromium interface: there is a transient interlayer at the original substrate/chromium interface while there is not at the laser-quenchedzone/chromium interface; the near-substrate surface microstructure and morphologies of the free-standing chromium electrodeposits, whose substrate was dissolved away with nital 30% in volume, inherit the periodically gradient characteristics of the laser-discrete-quenched substrate surface. (c) 2006 Elsevier B.V. All rights reserved.

Degradation failure features of chromium-plated gun barrels with a laser-discrete-quenched substrate

The effect of substrate laser-discrete quenching on the degradation failure of chromium-plated gun barrels was metallurgically investigated. The results show that substrate laser-discrete quenching changes the failure patterns of chromium coatings during firing, and some periodic through-thickness cracks in the fired chromium coatings are justly located at original substrate zones between two adjacent laser-quenched tracks. Moreover, chromium coatings and the laser-quenched zones on the substrate are simultaneously degraded in microstructure and property during firing. Furthermore, the periodic structure of the laser-discrete-quenched steel (LDQS) substrate near the breech remains after firing, and the hardness of the fired laser-quenched zones is still higher than that of original substrates. The specific failure features were utilized to illustrate the mechanism of the extended service life of chromium-plated gun barrels with the LDQS substrate. (c) 2007 Elsevier B.V All rights reserved.

土壤侵蚀的3个基本动力学过程

简要介绍了土壤侵蚀的基本特征,将土壤侵蚀过程概括为3个基本的动力学过程,即降雨导致的坡面产流过程、表面流对土壤颗粒的剥蚀过程,以及表面流的汇集和输沙过程.进一步对3个基本过程的基本内容和涉及的科学问题进行了分析和概括,并由此讨论了土壤侵蚀动力学研究的发展趋势.

四氧化二氮对卫星漫反射试片氟化镁涂层的污染和侵蚀

利用漫反射率、X射线光电能谱和质谱等测量方法,研究了固态和气态四氧化二氮(N2O4)对漫反射试片氟化镁(MgF2)涂层表面的污染情况.实验表明,固态N2O4对MgF2涂层有严重侵蚀作用,N2O4固粒污染后的涂层表面漫反射率下降了20%～30%.在一定的时间内,气态N2O4对涂层表面的影响显著地依赖它的压力.试片在压力为6.9×104 Pa和200Pa的N2O4蒸气中分别放置10 min,前者厚度为40μm的MgF2涂层基本消失,表面漫反射率下降约20%;后者涂层表面的原子组成和漫反射率变化很小.还给出了MgF2涂层表面N2O4分子吸附摩尔密度,以及与涂层表面碰撞的N2O4分子通过化学吸附过程提取MgF2的几率.

Variation of flexural strength of cement mortar attacked by sulfate ions

Under the environment of seawater, durability of concrete materials is one of the chief factors considered in the design of structures. The decrease of durability of structures is induced by the evolution of micro-damage due to the erosion of chlorine and sulfate ions, which is characterized by the reduction of modulus, strength, and toughness of the material. In this paper, the variation of the flexural strength of cement mortar under sulfate erosion is investigated. The results obtained in present work indicate that the erosion time, concentration of sulfate solution, and water-to-cement ratio will significantly affect the flexural strength. Crown Copyright (c) 2008 Published by Elsevier Ltd. All rights reserved.

Occurrence of spanning of a submarine pipeline with initial embedment

For better understanding the mechanism of the occurrence of pipeline span for a pipeline with initial embedment, physical and numerical methods are adopted in this study. Experimental observations show that there often exist three characteristic phases in the process of the partially embedded pipeline being suspended: (a) local scour around pipe; (b) onset of soil erosion beneath pipe; and (c) complete suspension of pipe. The effects of local scour on the onset of soil erosion beneath the pipe are much less than those of soil seepage failure induced by the pressure drop. Based on the above observations and analyses, the mechanism of the occurrence of pipeline spanning is analyzed numerically in view of soil seepage failure. In the numerical analyses, the current-induced pressure along the soil surface in the vicinity of the pipe (i.e. the pressure drop) is firstly obtained by solving the N-S equations, thereafter the seepage flow in the soil is calculated with the obtained pressure drop as the boundary conditions along the soil surface. Numerical results indicate that the seepage failure (or piping) may occur at the exit of the seepage path when the pressure gradient gets larger than the critical value. The numerical treatment provides a practical tool for evaluating the potentials for the occurrence of pipe span due to the soil seepage failure.

Adiabatic shear localization: occurrence, theories, and applications

节流器内液-固两相流固体颗粒冲蚀数值模拟

建立了考虑颗粒碰撞的颗粒冲蚀计算模型,该数学模型包括:在Eulerian坐标系下求解连续相流场;在Lagrangian坐标系下运用离散颗粒硬球模型求解颗粒碰撞;应用半实验关联式求解颗粒冲蚀速率。对水力加砂压裂施工中节流器内液-固两相流的固体颗粒运动和冲蚀特性进行了数值模拟。计算结果表明,固体颗粒密集于节流器入口到出口的一段狭长区域内,冲蚀速率随流体速度呈指数性变化。颗粒直径越大,冲蚀速率也越大。节流器内冲蚀最严重的位置发生在距离节流器出口上边缘10mm以内的局部区域。

Modeling on Runoff and Sediment Yield in Small Watersheds

The prediction and estimate of water and soil loss is fundamental important for understanding the effect of the spatial heterogeneity of underlying surfaces and preventing ecological environment deterioration. In this paper, a dynamic model of runoff and sediment yield in small watersheds is established. The proposed model includes three components: runoff generation caused by rainfall, soil erosion on hillslopes by overland flow, and runoff concentration and sediment transport on watersheds. Applying the proposed model, the runoff and sediment yield processes in a typical catchment on the loess plateau was estimated, which exhibited a good agreement between predicted results and observation.

Development of arc root attachment in the nozzle of 1 kW N2 and H2-N2 arcjet thrusters

Arc root behavior affects the energy transfer and nozzle erosion in an arcjet thruster. To investigate the development of arc root attachment in 1 kW class N2 and H2-N2 arcjet thrusters from the time of ignition to the stably working condition, a kinetic series of end-on view images of the nozzle obtained by a high-speed video camera was analyzed. The addition of hydrogen leads to higher arc voltage levels and the determining factor for the mode of arc root attachment was found to be the nozzle temperature. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures.

NUMERICAL STUDY OF DAMMANN ARRAY ILLUMINATORS

The numerical solutions of binary-phase (0, tau) gratings for one-dimensional array illuminators up to 32 are presented. Some fabrication errors, which are due to position-quantization errors, phase errors, dilation (or erosion) errors, and the side-slope error, are calculated and show that even-number array illuminators are superior to odd-number array illuminators when these fabrication errors are considered. One (0, tau) binary-phase, 8 x 16 array illuminator made with the wet-chemical-etching method is given in this paper.

Optical intrinsically fuzzy mathematical morphology for gray-scale image processing

Intrinsically fuzzy morphological erosion and dilation are extended to a total of eight operations that have been formulated in terms of a single morphological operation--biased dilation. Based on the spatial coding of a fuzzy variable, a bidirectional projection concept is proposed. Thus, fuzzy logic operations, arithmetic operations, gray-scale dilation, and erosion for the extended intrinsically fuzzy morphological operations can be included in a unified algorithm with only biased dilation and fuzzy logic operations. To execute this image algebra approach we present a cellular two-layer processing architecture that consists of a biased dilation processor and a fuzzy logic processor. (C) 1996 Optical Society of America

Fuzzy reasoning morphological operators and their optical implementation

Fuzzy-reasoning theory is widely used in industrial control. Mathematical morphology is a powerful tool to perform image processing. We apply fuzzy-reasoning theory to morphology and suggest a scheme of fuzzy-reasoning morphology, including fuzzy-reasoning dilation and erosion functions. These functions retain more fine details than the corresponding conventional morphological operators with the same structuring element. An optical implementation has been developed with area-coding and thresholding methods. (C) 1997 Optical Society of America.

FUZZY SOLID SETS FOR MATHEMATICAL MORPHOLOGY AND OPTICAL IMPLEMENTATION

Fuzzy sets in the subject space are transformed to fuzzy solid sets in an increased object space on the basis of the development of the local umbra concept. Further, a counting transform is defined for reconstructing the fuzzy sets from the fuzzy solid sets, and the dilation and erosion operators in mathematical morphology are redefined in the fuzzy solid-set space. The algebraic structures of fuzzy solid sets can lead not only to fuzzy logic but also to arithmetic operations. Thus a fuzzy solid-set image algebra of two image transforms and five set operators is defined that can formulate binary and gray-scale morphological image-processing functions consisting of dilation, erosion, intersection, union, complement, addition, subtraction, and reflection in a unified form. A cellular set-logic array architecture is suggested for executing this image algebra. The optical implementation of the architecture, based on area coding of gray-scale values, is demonstrated. (C) 1995 Optical Society of America

Fuzzy inferring mathematical morphology and optical implementation

Fuzzification is introduced into gray-scale mathematical morphology by using two-input one-output fuzzy rule-based inference systems. The fuzzy inferring dilation or erosion is defined from the approximate reasoning of the two consequences of a dilation or an erosion and an extended rank-order operation. The fuzzy inference systems with numbers of rules and fuzzy membership functions are further reduced to a simple fuzzy system formulated by only an exponential two-input one-output function. Such a one-function fuzzy inference system is able to approach complex fuzzy inference systems by using two specified parameters within it-a proportion to characterize the fuzzy degree and an exponent to depict the nonlinearity in the inferring. The proposed fuzzy inferring morphological operators tend to keep the object details comparable to the structuring element and to smooth the conventional morphological operations. Based on digital area coding of a gray-scale image, incoherently optical correlation for neighboring connection, and optical thresholding for rank-order operations, a fuzzy inference system can be realized optically in parallel. (C) 1996 Society of Photo-Optical Instrumentation Engineers.