机械式转速跟踪器在甘蔗收获机的应用研究

针对甘蔗收获机械恶劣的作业工作环境,提出一种机械式转速检测及跟踪调节装置,用于对作业机构转速的检测及反馈。介绍机械式转速跟踪装置的工作原理,运用ADAMS对该机械进行仿真分析,并搭建试验平台进行试验验证。结果表明:机械式转速跟踪器的输出转速等于目标转速与跟踪转速之差的一半,与理论分析结论一致。基于机械式转速跟踪器的转速输出特性,构建甘蔗收获机械作业机构的机电液速度闭环控制系统,建立该系统的动力学仿真模型,应用MATLAB分析系统的稳定性和动态响应特性。仿真结果表明:机械式转速跟踪器能够满足甘蔗收获机械各子系统间转速的协调联动控制要求。     

成形速度对卷板机工作辊疲劳寿命影响的研究

基于大型卷板机成形板材的过程,应用有限元分析软件ABAQUS和疲劳分析软件FESAFE对工作辊疲劳寿命进行了计算和分析。对比分析了不同工作辊转速对工作辊疲劳寿命的影响,最后得出了工作辊转速-疲劳寿命曲线。研究结果发现,在一定范围内,成形速度越快,工作辊疲劳寿命越低。     

基于AMESim的闭式液压系统热力学建模与仿真

以两行式甘蔗联合收割机液压闭式系统为对象,建立了基于AMESim热力学仿真模型,分析了影响系统温度的因素。结果表明:油箱的散热面积和冲洗阀压力影响温升的权重较低;散热器散热面积、风扇转速、负载和内泄漏量影响温升的权重较高,为闭式液压系统温升校核和元件选型提供参考。     

螺旋式扶蔗器振动分析及试验研究

针对南方丘陵地带甘蔗,收割机振动对收获系统的影响,建立了扶蔗器的振动模型,运用虚拟技术对该机构和甘蔗扶起过程进行了运动仿真,通过高速摄影进行了甘蔗扶起性能试验,获得扶蔗器对甘蔗的作用及影响规律。结果表明:在拾起段扶蔗器转速产生的振动有利于分蔗,运动状态较平缓。在输送段上,扶蔗器转速过慢会导致甘蔗未能被扶起,而扶蔗器转速过快,振动较大,甘蔗扶起过程中会出现严重跌落现象。螺旋式扶蔗器性能参数对甘蔗的扶起效果中,扶蔗器转速对振动影响最大。当扶蔗器转速为120 r/min时,扶起效果好。     

基于虚拟正交试验的压气机叶轮轴-毂径向微动特性研究(英文)

采用Pro/E建立压气机叶轮轴-毂三维模型,利用ANSYS软件采用子结构结合网格随移技术的分析方法,建立其有限元模型;采用虚拟正交试验方法对压气机叶轮轴-毂进行仿真,得出过盈量、摩擦系数、转速对最大单位摩擦功和平均摩擦功影响显著性次序及影响规律,从而得到最优组合。     

基于记忆程控截割法的采煤机液压调高系统响应时间的研究

主要介绍滚筒记忆程控截割技术,分析液压调高系统的响应时间与记忆程控调高的关系。在AMESim中建立液压调高系统模型,以MG750/1860-WD型采煤机为例进行仿真分析,得出液压系统空载调高情况下的响应时间,并对响应时间对螺旋滚筒高度调整的影响进行分析,同时通过实验来验证液压调高系统实际的响应时间。通过仿真分析及实验验证更加准确地确定了液压调高系统的响应时间,为采用记忆程控截割技术的采煤机滚筒高度调整中电磁阀通断时间长短的设定提供一定的数据依据,使螺旋滚筒高度的调整更加精确。     

高炉渣滚筒法处理过程的模拟实验研究

针对高炉渣滚筒法干式处理工艺,用液态石蜡模拟高炉融渣,研究了粘度和滚筒转速对凝固层厚度的影响规律。结果表明:凝固形成的蜡层厚度随熔体粘度的升高而变大,随滚筒转速的增加而变小;凝固层厚度随熔体粘度与滚筒转速的变化关系满足拟合公式:δ=15.43(μ/ρνL)~(1/2)。     

滚筒清理机转速的理论计算

对滚筒清理机内物料的运动进行了分析,给出了物料运动的一般方程及清理系数的计算方法。求出了滚筒清理机转速与滚筒半径的函数关系(n=25.34/R~(1/2)),按此函数选择滚筒转速可获得最佳清理效果。     

滚筒破碎筛滚筒转速的理论计算

从理论上将砂块视为质点,分析了砂块在无能量损失的情况下在滚筒中的运动轨迹,求出了滚筒破碎筛转速与滚筒半径的函数关系。按此函数关系选择滚筒转速可使砂块具有最大撞击能,由此可获得最佳破碎效果。     

宽窄行甘蔗种植机液压系统设计与研究

根据甘蔗宽窄行种植机的实际自动化作业需求,设计了该种植机的液压系统,并基于AMESim建立系统仿真模型,研究种植机液压系统液压特性和排种机构的输出特性。在比例调速阀的AMESim模型中,通过调节减压阀弹簧的初始力、初始位移和刚度大小、反馈腔的阻尼孔等主要参数获得了与产品样本一致的输出特性,从而为比例控制回路仿真提供合理的仿真参数,系统的其他仿真参数则由理论计算得到。仿真和试验结果表明:在种植机正常运行工况下,比例调速阀有较好的稳定速度的作用,在泵出口压力为10 MPa和泵出口流量20 L/min的条件下各执行元件都能协调工作,排种机构的转速最大误差为5.5%,种植机在不同行走速度下的播种间距均匀性较好,为甘蔗种植机的研究提供了参考。     

铝合金大型复杂薄壁壳体多道次旋压缺陷形成机理

铝合金大型复杂薄壁壳体旋压是多道次、多参数耦合作用下的复杂非线性过程,该过程中易出现反挤、鼓包、破裂等缺陷。采用实验和有限元模拟相结合的方法,分析这些缺陷的形成机理。结果表明,过大减薄率引起的旋轮前方金属隆起是导致反挤、鼓包、环状剥离及周向开裂的主因,过高的芯模转速会导致周向开裂和鳞状剥离等缺陷。提出了相应的缺陷防止措施,即采用24%以内的减薄率可以避免旋轮前方金属的严重隆起;限制芯模转速过高,以避免周向开裂和鳞状剥离等缺陷的发生。采用这些措施旋制出了合格的铝合金大型复杂薄壁壳体。     

泵控马达系统响应特性和效率特性的研究

建立了泵控马达系统仿真模型,对系统响应特性进行仿真研究和试验验证,结果表明:变量泵排量比由电信号决定,定量马达转速由电信号和泵转速共同决定。建立了静液压系统效率模型,对效率特性进行比较研究和试验验证,结果表明:泵控马达系统在大排量、中压、中高转速范围内具有良好的效率特性。     

Test and analysis of mechanism and influential elements of axial drifting of weldment on turning rolls

0　IntroductionTheweldingturningrollsismainlyusedforweldingassemblyofcylindricalweldingcomponents.Duetode viationinfabricationandassemblyofweldingturningrollsandgeometricirregularityofweldment,theweld mentthrobsaxiallywhileitrollsontheweldingturningrolls .Itwillinfluencetheweldingqualityandbreaknor malweldingprocedure .Intheworstcases,theweld mentfallsdownfromtheweldingturningrollsandcaus esaccident.Akindofweldingturningrollsagainstaxialdriftinghasbeeninventedabroadinthemiddleof 1980andhasbee…     

Origin,modeling and suppression of grinding marks in ultra precision grinding of silicon wafers

A phenomenon commonly encountered in grinding of silicon wafers is the grinding marks, which are difficult to remove by subsequent polishing process, and have been a great obstacle to the manufacture of silicon wafers with higher flatness. In this paper, the grinding marks formation mechanism was clarified, a grinding marks formation model and an angular wavelength model were developed, and a grinding marks suppression method was proposed. A series of grinding experiments were carried out to verify the developed models and investigate the effect of the wafer rotational speed, the wheel rotational speed, the infeed rate, the axial run out of the cup wheel and the spark out time. The results show that: (1) grinding marks are waviness generated on silicon wafers caused by non-uniform material removal circumferentially due to the axial run out of the cup wheel; (2) grinding marks present multiple angular wavelengths characteristics; (3) the angular wavelength of grinding marks is a one-variable function of the rotational speed ratio of the wheel to the wafer; and (4) grinding marks could be suppressed significantly by properly selecting the rotational speed ratio.     

An Investigation into Microstructures and Mechanical Properties of AA7075-T6 during Friction Stir Welding at Relatively High Rotational Speeds

In this study, microstructural changes and mechanical properties during friction stir welding of AA7075-T6 have been investigated. Friction stir welding at relatively high rotational speeds ranging from 1000 to 1400 rpm and longitudinal speeds in the range of 40 to 80 mm/min have been performed and then microstructures and mechanical properties of the weldments have been studied. The results show that the rotational and longitudinal speeds have a significant effect on the microstructures as well as the mechanical behavior of the welded material while a fine grain structure is produced at higher ratio of rotational speed to longitudinal speed. On the other hand, for a given longitudinal speed, it is revealed that there is an optimum rotational speed which gives the highest tensile strength and elongation for the stirred zone.     

An elastic deformation model of high speed spindles built into ball bearings

Kinematic characteristics and elastic deformation properties of ball bearings such as stiffness, axial, and radial deflections of the rings, speeds of balls, contact angles, and loads, all vary strongly with rotational speed, temperature, and axial preload. This paper presents an elastic deformation model of spindle units built into ball bearings, which are running on high rotational speed and axial preload. For this, software for simulation of the high speed spindle units was developed and introduced into a practical use. A computer aided analysis of the model was carried out and experiments were made, which showed a significant effect of high rotational speed, cutting load, bearing axial preload, and a new effect for which the criteria for a choice of bearing preload are given.     

回填式搅拌摩擦点焊过程的材料流动规律模拟

利用流体力学软件ANSYS FLUENT模拟了回填式搅拌摩擦点焊过程的材料流动行为,着重分析了搅拌头旋转速度与回填速度对材料流动的影响规律并加以试验验证.模拟结果表明,材料的流动速度随着到套筒内外壁距离的增加而减小,流动速度最大值出现在套筒端面的外壁处.在套筒内部,流动速度最小的材料位于焊点的中心处,此处的材料流动状态可通过增加旋转速度进行改善;从扩大焊点有效面积的角度来讲,增加搅拌头的旋转速度优于增加回填速度.上述规律得到了试验验证.     

Y型轧机圆锥齿轮的安装误差对轧件质量影响

本文以青铜峡铝业集团的UL+Z-1 500+255/14型铝镁硅连铸连轧机组为研究对象,以Y型三辊连轧机直齿圆锥齿轮的安装误差对圆铝杆表面质量的影响为研究内容,基于ADAMS软件对其进行了仿真分析。分析结果表明,Y型三辊连轧机直齿圆锥齿轮的安装误差可造成同一机架的三个轧辊的速度不一致,这种速度差不仅会造成圆铝杆表面的刮擦划伤和麻面斑痕等表面缺陷,而且当轧制温度较低时,会造成圆铝杆表面形状的差异,进而会形成麻坑、起皮、分层、裂纹等,导致圆铝杆产品因表面质量而不合格。因此,在提高直齿圆锥齿轮零部件的设计要求与加工精度的同时,重视和提高安装精度,是保证和提高圆铝杆表面质量的有效途径。