共查询到20条相似文献，搜索用时 78 毫秒
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通过UG软件建立了悬架结构的三维模型,在此基础上,应用HyperMesh建立了结构的有限元模型;并在ANSYS-Workbench中对其进行了3种极限工况下的静强度校核,验证了结构的强度。通过采用滤波白噪声建立路面时域模型作为动力学仿真的路面输入,在ADAMS软件中,进行动力学分析,得到在该路面输入作用下的载荷时间历程曲线;在N-Code DesignLife软件中,运用线性累计损伤准则对结构进行了疲劳寿命的预测,得到结构在随机载荷下的寿命及损伤分布。此外,通过与企业项目合作,在疲劳试验机下对悬架结构部件做了耐久性台架试验,检验在受到近似随机载荷作用下悬架结构的使用寿命。 相似文献
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土方机械落物保护结构动态仿真及试验 总被引：4，自引：0，他引：4
简述了土方机械落物保护结构的特点及性能要求,建立了落物保护结构受瞬态冲击响应的有限元结构动力学方程并提出了求解算法。以某装载机落物保护结构为例,建立了落物保护结构的非线性有限元模型,讨论了有限元网格划分及载荷施加方法,分析了落物保护结构的主要设计参数对冲击点最大位移及落锤速度和加速度的影响,并给出了更合理的结构。在试验台上对该装载机落物保护结构进行了落物冲击试验,试验结果和仿真结果吻合较好。落物保护结构的动态仿真为结构的设计提供了依据。 相似文献
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赵向阳 《农业装备与车辆工程》2010,(12)
采用有限元分析方法,建立了某电动轿车车身结构的有限元模型,分析了该车身结构弯扭组合工况下的静态特性,全面评价了该车身骨架结构的整体性能。在试验结果的基础上,提出了电动改装轿车车身结构的优化措施。 相似文献
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从结构优化的角度,对北方常见的连栋温室结构进行了荷载分析及内力计算,并采用优化设计理论,对实际应用结构进行了优化分析计算。在此基础上提出了合理的结构改进设计方案,研究结论可供北方连栋温室设计参考。 相似文献
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利用ANSYS软件对插秧机锥齿轮外壳结构建立了参数化几何模型和有限元分析模型,采用接触副合理解决了轴承和转轴间的接触问题。在此基础上进行了路面行驶危险工况和水田调头工况两种危险工况下的约束、加载和结构有限元分析计算,得到各工况下结构的应力分布和最大应力。采用ANSYS对插秧机锥齿轮外壳进行了优化设计,在满足结构外形变化不大的前提下,使结构强度得到提高。 相似文献
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在随机载荷的激励作用下,系统塔架结构产生了一系列的随机性动力响应。利用有限元方法对塔架结构建模,并应用随机振动理论和有限元方法对塔架结构进行随机性动力响应分析,推导了结构在随机载荷激励下的位移、应力响应的功率谱和均方值的计算公式,这为以后分析塔架结构随机动力响应提供了计算理论;同时给出算例,分析结果,最终肯定了该理论的可行性和必要性。 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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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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借鉴SCADA系统结构,讨论了一种温室环境监控系统,系统采用CAN/1-Wire分级网络,布线方便,运行可靠;RTU以基于ARM CORTEX-M3核的STM32处理器为核心,外围模块丰富,数据处理能力强;HMI采用CAN TO USB模块,软件设计灵活,安装使用方便,同时给出了系统结构和实现关键细节。 相似文献
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品种选择是农作物生产的第1步,不同品种在生育期、抗病性、抗倒性、区域适应性等方面存在较大的差异。选择适合本地区种植条件的优良品种与种子对农业生产和农民增收至关重要。结合丹东地区的实际情况,阐述在玉米、水稻品种的优化选择上应把握的原则和注意的问题,并提出相应的解决措施。 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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利用三包服务期内故障数据评估汽车的可靠性 总被引：2，自引：0，他引：2
利用汽车制造企业用户服务部门提供的三包服务期内的故障数据,可以对汽车的可靠性作出评估。通过对可靠性数据的整理,运用随机过程的理论建立整车可靠性评估的数学模型,并给出了算例。 相似文献
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为研究滴灌+冠层弥雾微喷(降温增湿措施)模式对葡萄光合特性,生理指标及产量品质的影响,试验设定微喷处理(WP1,WP2与WP3)与对照处理(CK)4个处理,在果粒膨大期测定不同处理的光合特性,果粒体积,产量与品质等数据结果显示:微喷处理胞间CO2浓度日变化幅度均低于对照处理,微喷处理中WP1处理的胞间CO2浓度最低;各处理的净光合速率均呈现“M”变化规律,在14:00出现“午休”现象,但微喷处理比对照处理“午休”时长较短,且WP1处理在14:00净光合速率降低幅度较小,各处理果粒体积与增长速率大小依次为WP1,WP2,WP3,CK,各处理的果粒体积增长速率均在7月15日达到最大.使用熵值法对各处理的产量与品质进行评价,各处理得分大小依次为WP1,WP2,CK,WP3.说明每日恰当的微喷处理可以显著提高葡萄净光合速率,果粒体积与果粒体积增长速率,产量与品质,但当微喷时间较长时也会影响葡萄产量与品质,因此以微喷1 h/d为最优. 相似文献
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Adapting to climate change: Agricultural system and household impacts in East Africa 总被引：4，自引：0，他引：4
The East African region exhibits considerable climatic and topographic variability. Much spatial and temporal variation in the response of different crops to climate change can thus be anticipated. In previous work we showed that a large part of this variation can be explained in terms of temperature and, to a lesser extent, water effects. Here, we summarise simulated yield response in two crops that are widely grown in the region, maize and beans, and investigate how the impacts of climate change might be addressed at two levels: the agricultural system and the household. Regionally, there are substantial between-country and within-system differences in maize and bean production responses projected to 2050. The arid-semiarid mixed crop-livestock systems are projected to see reductions in maize and bean production throughout most of the region to 2050. Yields of these crops in the tropical highland mixed systems are projected to increase, sometimes substantially. The humid-subhumid mixed systems show more varied yield responses through time and across space. Some within-country shifts in cropping away from the arid-semiarid systems to cooler, higher-elevation locations may be possible, but increased regional trade should be able to overcome the country-level production deficits in maize and beans caused by climate change to 2050, all other things being equal. For some places in the tropical highlands, maize and bean yield increases could have beneficial effects on household food security and income levels. In the other mixed systems, moderate yield losses can be expected to be offset by crop breeding and agronomic approaches in the coming decades, while more severe yield losses may necessitate changes in crop types, movement to more livestock-orientated production, or abandonment of cropping altogether. These production responses are indicative only, and their effects will be under-estimated because the methods used here have not accounted for increasing weather variability in the future or changes in the distribution and impacts of biotic and other abiotic stresses. These system-level shifts will take place in a context characterised by high population growth rates; the demand for food is projected to nearly triple by the middle of this century. Systems will have to intensify substantially in response, particularly in the better-endowed mixed systems in the region. For the more marginal areas, the variability in yield response, and the variability in households’ ability to adapt, suggest that, even given the limitations of this analysis, adaptation options need to be assessed at the level of the household and the local community, if research for development is to meet its poverty alleviation and food security targets in the face of global change. 相似文献
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为了解决针对型孔轮式排种器播量调节困难的问题,在偏心轮型孔轮式排种器的基础上,设计了一种由型孔轮和调节环（舌）组成的变容量型孔轮式排种器,以排种器的转速、调节舌类型、播量调节档位、行进速度、调节舌宽度为变量对油菜种子进行了单因素和多因素试验。试验结果表明：影响排种均匀性、各行排量一致性和种子破碎率的主要因素为排种器的转速、调节舌类型和型孔大小。变容量型孔轮式排种器的转速以30～50 r/min为宜,调节舌类型凹圆头优于平头,型孔长度增大对提高排种均匀性和各行排量一致性及降低破碎率有利。在所设计的结构尺寸条件下,该排种器适应于各类小粒度种子的条播。 相似文献