Experimental Study of Microstructure Evolution during Tempering of Quenched Steel and Its Application

LARGE-SIZED FORGINGS are usually intensivelyquenched to obtain the desired microstructuredistribution,high strength and hardness.Becauseresidual stresses are high in quenched large-sizedforgings,tempering processes follow quenchingprocesses to reduce the residual stress and obtain goodmechanical properties.Several differentmicrostructures are generated in quenched steelforgings,such as martensite,bainite and retainedaustenite.Modeling of microstructure evolution inquenched steel during …     

Effect of ball milling process on the microstructure of titanium-nanohydroxyapatite composite powder

Titaninm-nanohydroxyapatite （Ti-nHA） composite powders, composed of titanium with 10 vol.% and 20 vol.% of nano-hydroxyapatite, were milled in a planetary ball mill using alcohol media to avoid excessive heat. XRD and SEM were performed for characterization of the microstructure, and the homogeneity of Ti/HA nanocomposite powder was evaluated by EPMA with prolonged ball milling time. The results show that under the condition of wet milling, the grain size of Ti-nHA composite powders is decreased with the increase in ball milling time and the amount of the addition of nHA. While for milling of 30 h, the nanocomposite powder with free structure, which consists of the nano-hydroxyapatite （nHA） particles and titanium （Ti） phase, is obtained. Three stages of milling can be observed from the dement mapping of Ti, Ca, and P by EPMA; meanwhile, it is found that the nHA would be more homogenously distributed after milling for 30 h.     

A THERMODYNAMIC INVESTIGATION ON SPINODAL DECOMPOSITION BOUNDARY IN Cu－Ti ALLOYS

ＡＴＨＥＲＭＯＤＹＮＡＭＩＣＩＮＶＥＳＴＩＧＡＴＩＯＮＯＮＳＰＩＮＯＤＡＬＤＥＣＯＭＰＯＳＩＴＩＯＮＢＯＵＮＤＡＲＹＩＮＣｕ－ＴｉＡＬＬＯＹＳ￥ＷｅｉＹｉｎｇｈｕｉ；ＷａｎｇＸｉａｏｔｉａｎ（ＩｎｓｔｉｔｕｔｅｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎ...     

AN APPLICATION OF SPI TECHNIQUE FOR STUDING STRA DISTRIBUTION AT CRACK TIP

A computerized digital speckle-interferometry(SPI)system has been set up to determinethe in-plane distribution of displacement and strain at crack tip of CF specimens.Theprinciple and the experimental method of this technique are described in detail.Theeffect of corrosion factors on plastic deformation at crack tip in CF process has beenexamined by comparing the near-tip strain fields of steel A537 before and after hydrogencharging,and of pure copper before and after applying an anodic current in 3.5% NaCl.The results shows that the clasic finite element mathematical models are not suitable todescribe the near-tip deformation under the experimental conditions.Hydrogen chargingmade the crack tip plasticity decreased for steel A537 and the anodic dissolution enhancethe near tip deformation of pure copper specimen.     

Poyang Lake basin: a successful, large-scale integrated basin management model for developing countries

Protection of water environment while developing socio-economy is a challenging task for lake regions of many developing countries. Poyang Lake is the largest fresh water lake in China, with its total drainage area of 160,000 km2. In spite of rapid development of socio-economy in Poyang Lake region in the past several decades, water in Poyang Lake is of good quality and is known as the "last pot of clear water" of the Yangtze River Basin in China. In this paper, the reasons of "last pot of clear water" of Poyang Lake were analysed to demonstrate how economic development and environmental protection can be coordinated. There are three main reasons for contributing to this coordinated development: 1) the unique geomorphologic features of Poyang Lake and the short water residence time; 2) the matching of the basin physical boundary with the administrative boundary; and 3) the implementation of "Mountain-River-Lake Program" (MRL), with the ecosystem concept of "mountain as source, river as connection flow, and lake as storage". In addition, a series of actions have been taken to coordinate development, utilisation, management and protection in the Poyang Lake basin. Our key experiences are: considering all basin components when focusing on lake environment protection is a guiding principle; raising the living standard of people through implementation of various eco-economic projects or models in the basin is the most important strategy; preventing soil and water erosion is critical for protecting water sources; and establishing an effective governance mechanism for basin management is essential. This successful, large-scale basin management model can be extended to any basin or lake regions of developing countries where both environmental protection and economic development are needed and coordinated.     

Shadow geometry maps for alias-free shadows

Shadow maps sample scene visibility in the light source space and offer an efficient solution to generate hard shadows.However,they suffer from aliasing artifacts because of discretization errors,inadequate resolution and projection distortion.In this paper,we propose the shadow geometry map method,where a shadow depth map is augmented by storing geometry information about scenes.This leads to a new shadowrendering algorithm that combines a supersampling filter,a geometry-aware reconstruction kernel and an irregular sampling filter.Our method produces high quality alias-free and subpixel supersampling shadow rendering and retains the simplicity and the efficiency of shadow maps.We show that the algorithm pipeline is efficiently parallelized using current programmable graphics hardware and that our method is capable of generating high quality hard shadows.     

解放闸灌域水资源供需趋势分析及综合利用配置思路

文章对内蒙古河套灌区解放闸灌域的水资源现状、开发利用情况及需水量进行了分析和预测,对灌域近年水资源综合利用提出了初步配置思路。     

边界元插值法在含水层参数连续性问题中的应用

对于含水层参数连续性问题,传统的参数分区法会带来较大的计算误差,且其计算过程也较为繁琐。本文提出了一种新算法——边界元插值法,即在区域内对含水层压力传导系数采用二维反距离加权插值法、边界元上采用一维线性插值法,推导出边界积分方程的解析解,从而在整个区域上达到参数的连续性和可微性。将该方法与传统的有限差分法和边界元分区法同时应用于华北平原衡水试验场。计算结果表明:边界元插值法的计算结果与观测值的拟合误差在±3%以内,其精确度要略高于传统的边界元分区法和有限差分法,且计算过程较为简单。边界元插值法基本能够有效地处理含水层参数的连续性问题。     

高压切割喷嘴冲击磨损的数值分析

以复用矿井含煤颗粒的水对高压切割喷嘴的磨损物理问题为研究对象,采用计算流体力学理论进行数值计算,分析讨论了质量浓度为10、15、20、25、30、40 mg/L条件下速度、剪应力、磨损的分布以及变化关系。计算、分析结果表明:磨损主要发生在出口部位和锥体的后半部份,入口部份和锥体前半部份磨损较小;入口部位、锥体部位磨损量、剪应力随质量浓度增加变化较小;出口部位磨损量在质量浓度为10～20 mg/L减小较快,超过20 mg/L后变化不大;出口部位流体速度、磨损量、剪应力与质量浓度间存在对应关系。煤粒入口速度与混合物速度相同、锥体部位煤粒流体速度低于锥体部位混合物速度(平均值)约79.4%;煤粒出口部位速度随质量浓度的增大而呈现先增加后减小的趋势,速度最大值发生在浓度20 mg/L。     

椭圆管外流动熵产及放热系数的数值分析

以椭圆管加热水流动为研究对象,对椭圆管加热水流动系统进行了二维数值模拟。通过联立求解流体力学基本方程和熵产方程,获得了熵产、放热系数与雷诺数和纵、横向间距的变化关系。数值分析结果表明:熵产主要发生在管壁表面附近,而在系统内部区域熵产较小,可以忽略;熵产随雷诺数的增大而增大,随纵、横向间距增加而减小,熵产与雷诺数、纵、横向间距存在对应关系,纵、横向间距宜在1.75～2.0间;在相同的雷诺数值时,熵产、放热系数沿流动方向呈现单调减小的趋势;不同的雷诺数值,熵产、放热系数不同,单调减小的趋势相同。放热系数随Re的增大而增大,且与雷诺数存在对应关系。纵向总放热系数随纵、横向间距增大而减小,且存在对应关系。