共查询到18条相似文献，搜索用时 250 毫秒
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越沙步行轮仿生设计及动力学性能仿真 总被引：1，自引：0，他引：1
为提高车轮在沙土介质环境的通过性能,基于鸵鸟足趾结构形貌与运动方式,设计出一种仿生越沙步行轮。该步行轮通过轮脚中的定立柱和动滑块相互配合实现对轮下沙土的限流紧固功能,同时自适应带动轮刺机构进入附着牵引工作状态与离沙减扰非工作状态。采用多刚体动力学分析软件,预测了仿生越沙步行轮轮腿各部件之间的活动范围和干涉情况。采用离散元软件,分析了轮脚底面/沙土相互作用关系,验证了该仿生越沙步行轮具有良好的固沙限流、牵引附着性的特点。该研究为提高松软地面中步行机构的通过性能提供了参考。 相似文献
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为研究轻型地面车辆松软地面通过性能,针对轻载荷条件建立车轮牵引通过性预测模型,该文采用轮上载荷为30~90 N的轻载荷条件,以轮上载荷和轮径度为试验因素,车轮沉陷、挂钩牵引力和牵引效率为试验指标,开展滑转条件下轮壤相互作用试验研究。分析了试验因素对车轮牵引通过性的影响规律,发现载荷因素对试验指标的影响最为显著,显著性检验的置信度达90%。沉陷随着轮径的减小以及轮上载荷和滑转率的增加,车轮沉陷均呈现增加趋势,平均相对增加率分别为14.3%、36.9%和77.4%。挂钩牵引力随着载荷、滑转率和轮径的增加平均提高了约263%、295%和29.71%,牵引效率最大值均值为0.23,对应的滑转率为26.86%。基于传统沉陷模型和轮壤接触应力分布线性化公式,结合车轮土槽试验结果,建立了适合滑转条件的沉陷模型,模型计算值与试验值残差低于3.6 mm,平均相对误差小于6.4%,结果表明该模型能准确预测轻载荷条件下车轮沉陷。该研究为轻型车辆研制、轻载荷条件下车轮牵引通过性评估提供了参考。 相似文献
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针对黏重黑土地区马铃薯挖掘铲挖掘阻力大、能耗高等问题，以白茅根膜质叶鞘为仿生原型，设计了一种基于仿生波纹结构的马铃薯减阻挖掘铲。基于离散元（DEM）法仿真和土槽试验，确定减阻性能最优的设计参数；通过田间试验以油耗和阻力为指标验证仿生挖掘铲的减阻效果和挖掘性能。离散元仿真得到仿生挖掘铲最佳布置方式为纵向布置；在相同纵向布置方式下，通过土槽试验得到仿生挖掘铲的波纹参数在幅值为2.5 mm、频率为0.5时表现出较为优异的减阻性能。根据最佳参数研制仿生纵波纹铲，进行普通平铲和仿生纵波纹铲的作业对比试验，结果表明仿生纵波纹铲阻力减少了14.45%，单位油耗减少了17.15%。研究表明仿生纵波纹铲具有较好的减阻特性，仿生结构设计合理，能实现黏重黑土条件下马铃薯收获挖掘作业，可为整机节能减耗的研究奠定基础。 相似文献
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针对当前中国自走式蓝莓采收机作业通过性差等问题,建立轮壤接触力学模型,分析车轮驱动力矩、负载、沉陷量及挂钩牵引力等力学行为,得到车轮通过性影响因素为土壤属性、车轮结构参数和行走速度。采用离散元法建立蓝莓采收机轮壤接触模型,以车轮结构参数(宽度195、205、215 mm,直径615、627、639 mm)、行走速度0~11 km/h为试验因素,车轮结构参数或行走速度增加时,车轮阻力矩和土壤波动速度随之增加。依据车轮阻力矩设计行走驱动系统,采用闭式静液压四轮行走驱动系统,通过工况适应性仿真验证各车轮输出特性一致,稳定行走;系统可以克服车轮沉陷,平稳越障。通过样机田间试验得到行走驱动系统满足行驶速度范围0~11 km/h要求,运行平稳;车轮沉陷越障时无非目的性转向偏移,越障时间为3.3 s,与仿真结果一致;行走驱动系统与采收系统匹配性良好,采收效率为7.01 kg/min,果树采净率为92%,果树损伤率为11.5%。研究表明建立的轮壤接触模型可靠,行走驱动系统作业通过性效果好,可为蓝莓采收机研发提供参考。 相似文献
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机械弹性车轮提高轮胎耐磨性和抓地性分析 总被引：5，自引：5，他引：0
为提高轮胎接地性能,对新型机械弹性车轮垂直静态接地特性进行了研究。通过对车轮结构和承载方式进行分析,分别建立了基于Timoshenko圆形梁的车轮外圈弹性圆环模型和基于连续辐板的铰链组模型,并通过非线性有限元法和试验进行了验证。根据所建立的非线性有限元模型对机械弹性车轮和子午线充气轮胎的接地特性进行了对比研究,结果表明机械弹性车轮通过悬毂式承载控制车轮外圈变形,没有胎肩处的应力集中。在载荷为5 000 N时,机械弹性车轮和充气轮胎接地印迹中心0.14 m×0.265 m矩形区域内的接地压力偏度值分别为0.424和0.536 MPa。机械弹性车轮有效降低了接地压力偏度值,改善了轮胎接地的均匀性,提高了车轮耐磨损性能和抓地性能,研究为车轮性能优化提供了参考。 相似文献
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《土壤通报》2018,(6)
轮胎-土壤相互作用是地面力学重要的研究内容,水稻插秧机车轮和水田土壤交互作用是非常复杂的研究课题。研究插秧机转弯过程中流变土壤非线性运动过程,是揭示其复杂力学机理的重要研究方向。搭建多体动力学ADAMS与离散元EDEM双向耦合平台,基于双向耦合方法,模拟研究插秧机转弯过程中车轮与水田土壤相互作用运动机理;对比分析试验软泥层深度、承载力和黏附力,进行耦合模拟结果的可行性分析;模拟分析土壤颗粒力和位移时程变化,进而分析双向耦合微观机理。随着转弯角度的不断加大,车身外侧车轮较内侧车轮运动过程中水稻田土壤产生明显的运动;运动过程中水稻田泥土向两侧明显分离,且在车轮的表面有一定的黏附,并随着车轮的滚动逐渐脱落,但仍有少部分黏附在车轮侧壁。插秧机转向过程中车轮与土壤破碎颗粒均发生复杂的非线性动态运动,车辙的产生与水稻田颗粒内部受力状态及变化有着密不可分的联系。 相似文献
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四轮驱动拖拉机的驱动轮沿前轮辙行驶,在旱地、水田获得良好的牵引性能,因而得列广泛应用,有取代履带拖拉机的趋势。在水田,四轮驱动船式拖拉帆具有优良的越野、牵引性能,其后驱动叶轮除滑前驱动轮轮辙行驶外,还要求后驱动轮轮时沿前驱动轮刺孔行驶,这是更进一步的要求。该文是对沿前刺孔行驶的四轮驱动船式拖拉机动力学的专项试验研究,设计了三轮叶模拟试验装置,对前后轮叶刺孔的最佳偏移距或偏移率、前岳驱动叶轮轮叶的推力、承力和效率,以及影响效率的因素如滑转率、倾角、陷深、轮叶数等进行了深入的试验和探讨。 相似文献
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This study was aimed at finding the effect of a lug parameter that has been considered less important in improving the performance of cage wheels. This was the lug arrangement or configuration like a rubber tire on the cage wheels, called opposing circumferential lugs. The experiments were carried out in a laboratory soil bin with clay soil of 49% average soil moisture content and 135 kN average cone index. Cage wheels with opposing circumferential lugs at four levels of circumferential angle, 0°, 15°, 30° and 45°, were evaluated and their performance compared with normal cage wheels. The lug spacing and wheel slip of the test wheels were varied from 20°, 24°, 30° to 40° and from 25, 40 to 55%, respectively. All tests were conducted at a constant lug sinkage of 7 cm and at 20 rpm rotational speed of the wheel. The characteristics of three orthogonal force components produced by the cage wheels with opposing circumferential lugs were obtained by using a triaxial dynamometer. The pull and lift forces of the opposing lugs at circumferential angles of 15° and 30° were significantly higher than those of the normal lugs due to increase in the shear area in the corresponding direction, caused by the increase in lug length at larger circumferential angle. However, the wheel forces were drastically affected by the influence of the opposing circumferential lug interference at 45° circumferential angle. The better balancing of side forces could be obtained by increasing the circumferential angle and decreasing the lug spacing. The cage wheels with opposing circumferential lugs at 15° circumferential angle, 24° and 30° lug spacing gave superior performances as compared to other combinations. 相似文献
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The forces acting on a single model cage wheel lug were measured when operating in a wet clay soil. After initial lug entry into the soil, the normal and tangential forces acting on the lug increased up to a certain peak value and then dropped as lug rotation increased further. The tangential force later attained a negative peak value. The pull force showed the same trend as lug normal force. The lift force showed the same trend as tangential force, however, the positive peak value of lift force was much higher than the positive peak value of tangential component. The lift force was higher than the pull force. Increase in lug sinkage showed almost proportionate increase in lug forces while increase in soil moisture showed decrease in lug forces. The effect of lug slip on lug forces at constant sinkage was found to be statistically non-significant. 相似文献
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通过对水田叶轮单轮叶动力性能的大量测试结果,分析了轮叶产生的推进力、支承力和驱动效率受轮叶倾角、陷深、滑转率的影响和随轮叶转角位置的变化规律。轮叶产生最大推进力和支承力所对应的转角分别在90°和75°附近,支承力由正值变为零为零所对应的转角在100°左右。在95°轮叶转角附近轮叶的驱动效率最高,在80°至110°转角范围内有较高的驱动效率。但作旋轮线轨迹运动的单个轮叶,在滑转率10％～15％时最高驱动效率达75％,随着陷深和滑转率的增大驱动效率的平均值明显下降。 相似文献
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根据湖南省一般淹水水田和旱态水田的圆锥指数承压特性及土壤力学参数剪切特性来设计湖南独轮耕整机的驱动轮。设计驱动轮的依据是:(1)机械原理上公认的共轭啮合定律作为轮叶几何参数的推导依据,以滑转率(相当于齿轮的模数)作为基本推导轮叶基圆、滚动圆、倾角、压力角、轮叶高、轮叶数等几何参数;(2)按照轮叶下土壤流动失效及土壤反力模型试验数据以土壤力学理论分析推导轮叶倾角、数目等参数。设计了三轮样轮,通过在湖南省的夏耕、春耕生产试验,牵引性能试验,获得性能较优、结构较合理的H4、H3型驱动轮,能适应湖南省一般淹水水田和旱态水田使用。 相似文献
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A. Armstrong J. N. Quinton B. C. P. Heng G. C. Sander 《European Journal of Soil Science》2012,63(1):54-64
A significant amount of research focusing on the formation of surface seals and crusts and their effect on erosion can be found in the literature. In contrast, there has been limited research investigating the formation of surface shields, a layer of loose coarse sediment on the soil surface, despite the consequences for the transport of sediment, nutrients, metals and microorganisms. This study used rainfall simulation to examine the role of slope (2 and 10%), infiltration (with and without) and ponding depth (0, 0.3 and 0.7 cm) on the development of surface shields on a silt loam and a loamy sand soil. The results show that a continuous surface shield of loose coarse particles developed on the loamy sand, whereas the silt loam soil surface was covered by varying proportions of aggregates, compacted soil and loose coarse particles. Infiltration had a limited positive impact on shield development and both slope and ponding depth were significant controls over the development of the surface characteristics. 相似文献
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黄土高原土壤颗粒组成及质地分区研究 总被引：7，自引：0，他引：7
黄土高原土壤颗粒组成主要以细沙粒和粗粉沙为主 ,此二者是土壤的骨架部分 ,其含量占颗粒总量的 5 0 %以上。该区土壤颗粒组成具有高度的均一性 ,分布具有一定的规律性。按照土壤物理性黏粒含量 ,区内土壤质地可分为松沙土带、紧沙土带、沙壤Ⅰ带、沙壤Ⅱ带、轻壤Ⅰ带等 10个条带 相似文献
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Microwave heating of commercial microwavable polypropylene packaging in contact with fatty food simulants caused significant antioxidant degradation and increased specific migration as shown by electrospray ionization-mass spectrometry (ESI-MS) and gas chromatography-mass spectrometry (GC-MS). Degradation of the antioxidants Irgafos 168 and Irganox 1010 was not detected during conventional heating of polypropylene packaging at the same temperature. The migration into aqueous food simulants was primarily restricted by the water solubility of the migrants. Using isooctane as fatty food simulant caused significant swelling and greatly enhanced overall migration values compared to the other fatty food simulant, 99.9% ethanol, or the aqueous food simulants 10% ethanol, 3% acetic acid, or water. ESI-MS spectra clearly reflected the overall migration values, and the number and amount of compounds detected decreased as the hydrophilicity of the food simulant increased. ESI-MS was shown to be an excellent tool for the analysis of semivolatile migrants and a good complement to GC-MS analysis of volatile migrants. 相似文献