青菜头缩短茎滑切刀研制

青菜头机械化收获水平低下是制约青菜头产业发展的重要原因之一。为解决青菜头机械化收获过程中缩短茎切割难度大和农机与农艺融合程度低等问题,该研究提出了一款滑切式青菜头收获机并对其滑切刀作业参数进行分析与试验。首先,基于青菜头收获农艺要求阐述青菜头收获机整机及其切根装置的结构及工作原理,根据受力分析确定滑切刀安装方式。然后,对紫色土壤和滑切刀的接触参数进行标定并基于EDEM建立土壤-滑切刀互作模型,仿真分析不同作业速度、刀具夹角对滑切刀作业阻力的影响。结果表明:1)相同速度下,滑切刀交叉夹角与作业阻力负相关;2)相同滑切刀角度下,滑切刀作业阻力与作业速度正相关。以滑切刀切削阻力为评价指标,作业速度、刀具夹角、切割距离为影响因素进行切割试验并对试验参数进行优化,结果表明:滑切刀作业速度与切削阻力呈正相关,切割距离与切削阻力呈负相关,刀具夹角从60°到120°,切削阻力先减小再增大。影响切削阻力大小的主次因素顺序为作业速度、刀具夹角和切割距离。优化圆整后的滑切刀作业速度为0.1 m/s,刀具夹角65°,切割距离20 mm,3次重复试验得到的切削阻力依次为141.24、156.32和150.65 N,与理论切削阻力128.63N相对误差分别为9.8%、21.53%和17.12%,较Box-Behnken试验平均切削阻力分别下降44.30%,38.35%和40.59%,验证了滑切刀作业参数优化的有效性。研究结果可为青菜头机械化收获提供参考,具有重要的工程应用价值。

滑切防缠式香蕉秸秆还田机设计与试验

针对香蕉秸秆富含纤维且含水率高等物理特性,现有的秸秆与根茬粉碎还田机田间作业时存在着切割阻力大,秸秆纤维易缠绕等问题。采用理论建模方法确定了秸秆滑切刀片的刀刃曲线方程;设计阐述了还田机的关键结构参数,该文研制出一种滑切防缠式香蕉秸秆还田机,并阐述了还田机械的总体机构与工作原理,同时对其秸秆粉碎率以及功耗进行田间试验。结果表明:各因素对香蕉秸秆粉碎率和功耗影响的显著性顺序从大至小依次均为秸秆粉碎刀辊转速、灭茬刀辊转速、机器前进速度。当机器前进速度为1.39 m/s、秸秆粉碎刀辊转速为1 600 r/min、灭茬刀辊转速为500 r/min时,香蕉秸秆粉碎率为95.2%,功耗为4.96 k W。在最优工作参数情况下,实际香蕉秸秆粉碎率为94.9%,实际功耗为5.1 k W,与软件分析值(95.2%、4.96 k W)间的误差分别为0.31个百分点、0.27%,验证了分析的可信性。通过与甩刀式立式香蕉秸秆粉碎还田机进行性能对比试验,得出所研制的滑切防缠式香蕉秸秆还田机秸秆粉碎率提高1.94个百分点,功耗降低11.3%。该机器的设计为中国南方热带地区香蕉秸秆还田技术的推广与应用提供了基础。

水稻秸秆反旋深埋滑切还田刀优化设计与试验

针对水稻秸秆深埋还田时,还田刀作业功耗过高和缠草的问题,结合还田机作业过程,分析还田刀功耗过高和缠草的原因,设计了一种反旋深埋滑切还田刀。使用阿基米德螺旋线设计还田刀侧切刃,提高还田刀的滑切性能,计算并验证侧切刃曲线的动态滑切角满足土壤秸秆滑出还田刀的条件,使用圆弧曲线设计还田刀正切面,以耕宽和正切面安装角为依据确定圆弧半径为60 mm。运用离散元仿真软件EDEM进行了反旋深埋滑切还田刀与传统还田刀的仿真对照试验,结果表明反旋深埋滑切还田刀的秸秆还田率、抛土性能与传统还田刀基本一致,作业功耗降低18.19%,选取留茬高度、刀辊转速和机具前进速度为影响因素,选取作业功耗为评价指标进行正交试验设计,确定影响还田机作业功耗的因素从大到小依次为:刀辊转速、机具前进速度、留茬高度。田间试验结果表明:在土壤含水率为20%~30%,地表秸秆覆盖量为336~353 g/m^(2),拖拉机作业速度为低速一挡(1.5 km/h),刀辊转速为250 r/min时,秸秆深埋滑切还田刀作业后,平均耕深为18 cm左右,秸秆还田率为87.9%~89.7%,地表平整度为2.1~3.7 cm,作业指标均满足秸秆还田的农艺要求。

Performance evaluation of minimum quantity lubrication by vege-table oil in terms of cutting force,cutting zone temperature,tool wear,job dimension and surface finish in turning AISI-1060 steel

In all machining processes, tool wear is a natural phenomenon and it leads to tool failure. The growing demands for high productivity of machining need use of high cutting velocity and feed rate. Such machining inherently produces high cutting temperature, which not only reduces tool life but also impairs the product quality. Metal cutting fluid changes the performance of machining operations because of their lubrication, cooling and chip flushing functions, but the use of cutting fluid has become more problematic in terms of both employee health and environmental pollution. The minimization of cutting fluid also leads to economical benefits by way of saving lubricant costs and workpiece/tool/machine cleaning cycle time. The concept of minimum quantity lubrication (MQL) has been suggested since a decade ago as a means of addressing the issues of environmental intru- siveness and occupational hazards associated with the airborne cutting fluid particles on factory shop floors. This paper deals with experimental investigation on the role of MQL by vegetable oil on cutting temperature, tool wear, surface roughness and dimen- sional deviation in turning AISI-1060 steel at industrial speed-feed combinations by uncoated carbide insert. The encouraging results include significant reduction in tool wear rate, dimensional inaccuracy and surface roughness by MQL mainly through reduction in the cutting zone temperature and favorable change in the chip-tool and work-tool interaction.