仿生非光滑犁壁规范化设计

通过深入研究典型土壤动物蜣螂的体表而，建立了数学模型，以便描述非光滑单元体尺寸、形状和位置的分布规律；基于数学模型仿真，模拟了仿生非光滑表而。为了满足工业化生产，对仿生非光滑单元体的尺寸进行了规范化处理，并讨论了不同规范化没计的特点，以适应不同的仿生非光滑犁壁加工。     

悬挂式旋耕机组振动问题研究

悬挂式旋耕机组在作业过程中存在着严重的振动问题,这不仅恶化了驾驶员的工作环境,而且直接影响机具的工作寿命。本文运用频谱分析方法和模态分析技术,系统研究了引起振动的因素,提出了改善振动特性的方法。     

Measurements of Mouldboard Plow Draft: II. Draft-Soil-Crop and Yield-Draft Associations

The primary objective of this investigation was to evaluate some potential causal associations between draft derived from a 3-bottom mouldboard plow during normal fall field operations and soil-crop properties at a field site near Winchester, Ontario, Canada. A secondary objective was to investigate, in a preliminary manner, associations between draft and crop yield (corn, soybean, and wheat). Regression tree analysis indicated that draft variability was best explained by field location, crop type, soil cone penetration resistance in the plow layer, and soil texture in the plow layer. Draft was found to generally increase with cone penetration resistance in the plow layer and soil clay content. Corn yields were negatively associated with draft. The reverse was true for the soybean yields, and a combination of negative and positive draft vs. yield relationships existed for the wheat plots. The overall results indicated that draft data collected during normal field operations can be useful for producers interested in identifying areas in the field where soil strength/compaction might be problematic with regard to crop yields.     

Measurements of Mouldboard Plow Draft: I. Spectrum Analysis and Filtering

Measurements of mouldboard plow draft can potentially provide a useful tool for continuously mapping, as a surrogate variable, crop limiting soil properties such as soil strength/compaction. Numerous researchers have shown that loading on tillage tools can be periodic. One source of higher frequency periodic loading has been related to failure modes in the soil. Lower frequency periodic loading on tillage tools, assuming tillage depth is relatively constant, more often reflects local spatial variability in soil physical properties such as soil moisture, soil texture, organic matter, and/or soil strength/compaction. This study presents a spectrum and cross-spectrum analysis of mouldboard draft recorded during normal fall plowing operations along adjacent transects. One objective of this study was to determine the dominant periodic components in order to elucidate meaningful frequencies which might be better related to variation in soil physical properties. Spectral densities were generally dominated by signals with a few cycles per 300-m transect. The cross-amplitude and squared coherency between draft recorded on adjacent transects provided further indication of the frequencies which characterized the signals because they provide an indication of correlation as a function of frequency. Spatial dependence in the data was quantified using spatial autocorrelation and cross-correlation. An additional objective was to use the spectral information to help design more physically meaningful filters for the raw draft data. Taking the Fast Fourier Transform of the raw draft data and filtering in the frequency domain using an optimal filter informed via the spectrum and cross-spectrum analysis, provided a convenient method for isolating a more physically meaningful signal.     

元线非直线型铧式犁几何与力学特性研究

降低铧式犁耕作阻力,减少能源消耗,是国内外农业机械研究者一直非常关注的课题。铧式犁犁体曲面成型方法是元线沿着准线按照一定规律运动形成,元线与准线形式是影响铧式犁耕作阻力的两个重要因素。以BTU3 5犁体为基础,用三角函数曲线代替直线作为元线形成新犁体曲面,采用有限元分析方法 ,将两犁体曲面耕作阻力进行比较。研究发现:三角曲线作为元线形成的犁体曲面耕作阻力较小,在5、6、7km/h时耕作阻力分别比原犁体降低2.5%、4.1%、3.9%。结合直线与sin函数曲线曲率变化情况,可得出结论:变曲率犁体曲面更有利于降低耕作阻力。     

机械深松营造"土壤水库"工程技术在兰州地区的推广研究

旱作区耕地的“犁底层”已成为农业耕作的一大障碍。介绍了机械深松营造“土壤水库”工程技术及推广研究中采用的方法和主要技术措施;综述了在兰州地区推广应用情况及对比试验结果;并分析探讨机械深松营造“土壤水库”工程技术的增产机理。经过分析认为,该技术是旱作区农业增效农民增收的有效途径,推广前景十分广阔。     

手扶驱动式圆盘犁试验结果分析

对手扶拖拉机配套驱动式圆盘犁研究过程中有关试验结果作一分析。研究结果表明，作业工艺质量符合农艺要求；驱动速度系数以２．２０～４．６７为宜；以主选工作挡乘坐作业可显著提高生产率；驱动滑切形成沟壁，撕裂形成沟底，较大地降低了能耗。研究结果可供手扶驱动式圆盘犁产品设计及推广使用部门决策时参考。     

油菜直播机开沟犁体曲面优化与试验

为减小油菜直播机开畦沟系统牵引阻力并分析机组不同作业速度对牵引阻力影响的规律,开展了开畦沟犁体曲面参数与作业速度的试验研究。建立了EDEM离散元土壤仿真模型,以犁体牵引阻力为试验指标分别开展以铧刃起土角、导曲线开度、直元线起始角、直元线最大角及作业速度为试验因素的试验;构建了犁体曲面优化模型,并开展了犁体曲面的3D打印及试制加工。仿真试验结果表明:在试验范围内,牵引阻力随铧刃起土角增大而减小,分别随导曲线开度、直元线起始角、直元线最大角增大而增大,随作业速度的增大而急剧增大,作业速度从1.0 m/s增加到2.0 m/s,牵引阻力及功耗分别为前者的1.98倍及3.97倍;仿真优化结果表明:当犁体在一定工作参数条件下,铧刃起土角为15°,导曲线开度为190 mm,直元线起始角为35°,直元线最大角为40°时,犁体牵引阻力最小为241.11 N,比优化前减少11.26%。为考察优化犁体实际田间作业效果,对犁体进行3D打印及试制加工并与原有犁体进行田间对比试验,结果表明优化犁体作业的畦沟沟底大块土垡少,残留土壤质量减少62.87%,沟底干净,T型沟明显。     

Extending results from agricultural fields with intensively monitored data to surrounding areas for water quality management

A 45% reduction in riverine total nitrogen flux from the 1980-1996 time period is needed to meet water quality goals in the Mississippi Basin and Gulf of Mexico. This paper addresses the goal of reducing nitrogen in the Mississippi River through three objectives. First, the paper outlines an approach to the site-specific quantification of management effects on nitrogen loading from tile drained agriculture using a simulation model and expert review. Second, information about the net returns to farmers is integrated with the nitrogen loading information to assess the incentives to adopt alternative management systems. Third, the results are presented in a decision support framework that compares the rankings of management systems based on observed and simulated values for net returns and nitrogen loading. The specific question addressed is how information about the physical and biological processes at Iowa State University’s Northeast Research Farm near Nashua, Iowa, could be applied over a large area to help farmers select management systems to reduce nitrogen loading in tile drained areas. Previous research has documented the parameterization and calibration of the RZWQM model at Nashua to simulate 35 management system effects on corn and soybean yields and N loading in tileflow from 1990 to 2003. As most management systems were studied for a 6 year period and in some cases weather had substantial impacts, a set of 30 alternative management systems were also simulated using a common 1974-2003 input climate dataset. To integrate an understanding of the economics of N management, we calculated net returns for all management systems using the DevTreks social budgeting tool. We ranked the 35 observed systems in the Facilitator decision support tool using N loading and net returns and found that rankings from simulated results were very similar to those from the observed results from both an onsite and offsite perspective. We analyzed the effects of tillage, crop rotation, cover crops, and N application method, timing, and amount for the 30 long term simulations on net returns and N loading. The primary contribution of this paper is an approach to creating a quality assured database of management effects on nitrogen loading and net returns for tile drained agriculture in the Mississippi Basin. Such a database would systematically extend data from intensively monitored agricultural fields to the larger area those fields represent.     

基于EDEM的凿式犁铲土壤扰动仿真分析与试验

为探究凿式犁铲（以下简称凿铲）的土壤扰动机理并构建适用于东北地区黏重黑土与耕作部件之间的仿真模型,结合EDEM仿真分析与土槽试验,与深松铲作业效果进行对比,研究凿铲对土壤的微观扰动机理和宏观扰动状态,并建立适宜东北地区土壤的耕作仿真模型。仿真与试验结果表明,深松铲对土壤进行剪切破坏,将耕作层和犁底层抬升、下落,对土壤松而不翻,不破坏原有的耕层土壤结构,土壤膨松度试验值为12.4%,土壤扰动系数试验值为59.4%,纵向截面扰动面积为52.586mm2,俯视视图扰动面积为116.779mm2;凿铲对土壤进行挤压破坏,将犁底层土壤翻耕到地表,破坏原有耕层土壤结构,土壤膨松度试验值为14.1%,土壤扰动系数试验值为64.1%,纵向截面扰动面积为54.128mm2,俯视视图扰动面积为233.061mm2,通过与深松铲作业后数据相比可知,凿铲可以实现更为明显的土壤扰动效果。同时,建立东北地区黏重黑土条件下的离散元土壤耕作模型,选用Hertz-Mindlin with JKR Cohesion模型作为土壤接触模型,确定仿真模型的各项技术参数,仿真与试验得到的土壤扰动截面轮廓基本拟合,土壤膨松度、土壤扰动系数的仿真值与试验值的相对误差为17%、4.4%,模拟仿真的数据误差范围满足要求,研究可为东北地区的土壤耕作部件离散元模拟仿真分析提供基础数据。