共查询到17条相似文献，搜索用时 62 毫秒
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将相变与形变有效结合,开发了中碳钢在马氏体相变状态下的温变形超细晶制备工艺.试验结果表明:淬火态中碳钢快速加热到500～600℃,回火适当时间使其仍保持一定程度的过饱和度,然后快速温变形,通过孪生、位错分解和再结晶等方式实现位错在滑移面上运动形成位错林或位错交滑移,使过饱和铁素体组织快速细化,其晶粒平均尺寸小于1μm;在结构畸变能与形变储能作用下通过应变诱导使碳化物以弥散状的形式在晶界和亚晶界处析出,得到均匀的形变马氏体组织;形变后可通过退火工艺控制碳化物颗粒的析出量、大小及分布,使材料具有最佳的组织结构,即细小铁素体 弥散碳化物,以满足材料综合性能的要求. 相似文献
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将马氏体相变与强塑性变形工艺相耦合,开发了基于等通道角挤压快速制备亚微米级中碳钢工艺。试验采用45号钢,就淬火态在不同回火温度和回火时间条件下进行挤压。试验结果表明,由马氏体相变得到的过饱和铁素体为动态再结晶和应变诱导碳化物析出作了能量和组织准备,并在一定的回火温度下进行等通道角挤压使位错密度快速增加,实现了动态再结晶,形成了细小晶粒,同时应变诱导碳化物从过饱和的铁素体中以弥散形式析出,使亚微米铁素体基体上均匀分布着细小碳化物。这种组织结构具有较高的稳定性,在550℃退火30min后,晶粒尺寸仍保持在1μm以内。 相似文献
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为探明钢中微合金元素(V、Nb)与变形条件对含钒钢形变强化相变的影响规律.为制备含钒超细晶粒钢提供理论依据,通过对含钒钢进行形变强化相变热模拟试验,分析得出V、Nb的影响为:固溶V、Nb不利于形变强化铁素体相变的进行;V(C,N)、V-Nb(C,N)可以在多道次变形中沉淀析出,成为铁素体的异质形核核心,同时析出相对晶界及亚结构的钉扎作用使铁素体晶粒细化.研究表明,多道次变形时,道次间隔时间越短,温度越低,则累积的有效变形量越大,钢的形变强化相变越易进行.含钒钢超细晶铁素体体积分数越大. 相似文献
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《农业装备技术》2017,(4)
将热—力耦合弹塑性有限元方法与微观组织演化模型相集成,通过动态再结晶、亚动态再结晶以及晶粒长大模型相结合,定量分析了镁合金AZ31B在热压缩过程中的晶粒尺寸变化以及再结晶百分数变化。通过AZ31B镁合金圆柱形试样的Gleeble热力模拟试验,获得有限元模拟所需的高温流动应力曲线与再结晶晶粒尺寸,实验数据建立动态再结晶微观组织演化模型,并通过二次开发与有限元模型相集成,通过进行双道次Gleeble热力模拟试验对模拟预测结果进行验证。研究结果表明,部分动态再结晶部分将在压缩道次间发生亚动态再结晶以及晶粒长大,通过模拟得到的数据与实验数据相比较,说明本次模拟是可行的。 相似文献
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不论何种材料,其宏观性能都取决于材料内部显微组织的组成、形态和分布。为此,讨论了Matlab的图形图像处理功能如何应用到农机材料定量金相分析研究中,并通过晶粒度测定和两相合金中第二相颗粒几何尺寸测量两个实例进行了验证。结果表明,采用该软件可以高效、方便地实现定量金相分析功能。 相似文献
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Overland water and salt flows in a set of rice paddies 总被引：1，自引：0，他引：1
E. Playn O. Prez-Coveta A. Martínez-Cob J. Herrero P. García-Navarro B. Latorre P. Brufau J. Garcs 《Agricultural Water Management》2008,95(6):645-658
Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m−1) and an infiltration rate of 5.8 mm day−1. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day−1), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day−1 was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration. 相似文献
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瓦房店市是我国重要的水果生产基地,在国内水果生产领域占有重要地位。随着水果市场化的不断深入,如何满足和适应国内外市场需求成为瓦房店市水果生产的关键问题。从瓦房店市水果生产实际出发,阐述了实施水果生产标准化的必要性,提出了发展水果生产标准化的具体措施。 相似文献
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对引进的谷子新品种金谷子耐旱TG118进行品种比较试验和多点试种。结果表明：该品种抗旱、耐瘠、适应性强,稳产、高产、抗病抗风抗倒伏强,品质优良,粮草兼用,种植简单,省工易管;一般产量在6000kg/hm2以上,比当地主栽品种增产20%以上。最高产量达9450kg/hm2,适于在辽西北地区推广应用。 相似文献
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对《种子法》存在问题的探讨 总被引：1，自引：0，他引：1
李鹏 《农业机械化与电气化》2011,(6):129-130
《种子法》是我国种植业第一部法律。自实施以来,为依法加强种子管理提供了有力的法律支撑,促进我国种子产业发生翻天覆地的变化。但随着依法管理工作的深入和种子产业的快速发展,《种子法》及配套规章的一些问题逐步显现出来。对《种子法》及配套规章存在的问题进行深入分析,对需要进一步补充的章节以及需要调整的内容进行深入探讨,以求更加完善和明确。 相似文献
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About 30 years have passed since the Government of Egypt embarked on implementing a series of large scale drainage projects. At present, about 3.8 million acres have been provided with drainage systems on the basis of systematic pre-drainage investigations and designs. The target is to provide drains in approximately 6.4 million acres in the Nile Valley and Delta.The implementation of the subsurface drainage system is carried out by the public sector and private contractors under direct supervision of governmental regional departments. The implementation process depends on many factors related to the drainage material, machinery, manpower, site requirements, farmers and organizations involved. Problems and constraints are sometimes challenging, however, the annual rate of implementation has gradually increased to 170,000 acre/year.This paper discusses the different aspects involved in the implementation process of drainage systems. The development in materials, machinery and construction technologies will be reviewed. Institutional and management factors are going to be also considered. 相似文献
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在新世纪,面对机遇和挑战,党的十六大把“社会更加和谐”作为全面建设更高水平的小康社会的一个重要目标。中国人素有社会和谐的理想;西方人自古也向往社会和谐;借鉴东西方两种和谐社会思想的经验、教训,构建社会主义和谐社会理论。 相似文献
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Gunter Wriedt Marijn van der Velde Alberto Aloe Fayçal Bouraoui 《Agricultural Water Management》2009,96(5):771-789
We present a pan-European irrigation map based on regional European statistics, a European land use map and a global irrigation map. The map provides spatial information on the distribution of irrigated areas per crop type which allows determining irrigated areas at the level of spatial modelling units. The map is a requirement for a European scale assessment of the impacts of irrigated agriculture on water resources based on spatially distributed modelling of crop growth and water balance. The irrigation map was compiled in a two step procedure. First, irrigated areas were distributed to potentially irrigated crops at a regional level (European statistical regions NUTS3), combining Farm Structure Survey (FSS) data on irrigated area, crop-specific irrigated area for crops whenever available, and total crop area. Second, crop-specific irrigated area was distributed within each statistical region based on the crop distribution given in our land use map. A global map of irrigated areas with a 5′ resolution was used to further constrain the distribution within each NUTS3 based on the density of irrigated areas. The constrained distribution of irrigated areas as taken from statistics to a high resolution dataset enables us to estimate irrigated areas for various spatial entities, including administrative, natural and artificial units, providing a reasonable input scenario for large-scale distributed modelling applications. The dataset bridges a gap between global datasets and detailed regional data on the distribution of irrigated areas and provides information for various assessments and modelling applications. 相似文献
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在介绍粉质仪和拉伸仪结构和原理的基础上,探讨了粉质曲线中吸水率、形成时间、稳定时间、弱化度和评价值等指标与面粉品质的关系,以及如何根据拉伸曲线中面团最大拉伸阻力、延伸度和拉伸曲线面积等指标来评价面团品质,并结合生产实际,概述了粉质仪和拉伸仪在面粉生产中的作用。 相似文献
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车辆ABS控制算法的研究及探讨 总被引：1，自引：0，他引：1
对现代汽车的ABS控制算法作了一些简单的介绍,同时指出了它们的一些缺陷,相应地提出了几种对ABS的其它控制方法并加以探讨,其中着重论述了ABS门限值控制算法中参考车速的确定方法和基于附着系数的控制算法。 相似文献