激振力作用线对直线振动筛及筛上物料运动的影响

分析了直线振动筛激振力作用线偏离筛机质心时,筛机的运动状态发生的变化,建立了筛机质心的振动方程及绕质心转动的摇摆振动方程和筛机上任意点的振动方程。对影响物料的筛分效率、输送速度等作了详细的分析研究。     

轮式装载机行驶中振动对物料完整性的影响

以轮式装载机为研究对象,对其行驶中铲斗振动对物料完整性的影响进行了研究.首先通过简化分析建立了铲斗振动的数学模型和动态方程,求出其振动响应;然后通过分析铲斗振动的最大加速度,找出了影响物料完整性的各因素;最后基于MATLAB对ZL45型轮式装载机的物料完整性进行了仿真分析.结果表明,绕质心的转动惯量小,且较小弹性系数的低压比宽式专用轮胎等因素,有利于保持物料的完整性.     

物料管线振动分析与计算

某厂螺杆压缩机输送物料装置管线运行中发生严重振动 ,最大振幅发生在物料输送末端管线 ,最大振幅为 1 5mm ,严重威胁正常生产。通过振动测试 ,建立计算模型 ,振动计算分析 ,得出振动原因并通过模拟约束条件 ,给出管线防振改造方案 ,方案实施后大大减小了管线的振动     

我国第一代振动流化床：高效节能的GZQ系列振动流化床干燥机

该系列振动流化床干燥机为我国第一代振动流化床干燥(冷却、增湿)机,构思先进,质量可靠,生产效率高,并具有较低的耗能指标。振动流化床是在普通固定流化床的基础上。施加振动而成,其激振力来自按装在中部的振动电机;被处理的物料在给定方向的激振力的作用下跳跃前进,同时由流化底床部经气体分布板输入热风,使其物料呈流化状态,物料与热风充分接触,进而达到理想的干燥效果。整个工作过程及配套系统如图1所示。全机由振槽、槽盖、加料口、出料口、振床和减振器等部件组成,其结构简图及系列型谱如图2、表1所示。     

旋振筛的研究与发展

旋振筛体上各点的振动不尽相同。物料在旋振筛面上存在八种不同的运行轨迹，其中二种最适合筛分。此外，文事学简单地总结了旋振筛的发展和旋振技术的应用。     

振动流化床干燥机的基础特性研究

本文以振动流化床干燥机实验系统模型为基础，从动力学，运动学、空气动力学的角度，对振动流化床干燥机的特性进行了全面研究，得出了振动流化床的工作条件、运动状态及物料的运动状态。振动对物料的流化和干燥过程的影响也进行了分析。     

刚散耦合振动圆锥破碎机动力学分析

将振动圆锥破碎机简化为六自由度运动的物理模型,物料层采用分段线性接触力模型来表示。应用Lagrange方程,对振动圆锥破碎机进行了建模。通过Matlab采用Runge-Kutta法对振动微分方程组进行数值计算仿真,研究了不同激振频率下系统的动力学性能。研究结果表明,物料层的作用是系统非线性的根本来源,物料层的非线性导致系统从单一频率的简谐运动变为复杂运动,为振动圆锥破碎机的参数选择提供了依据。     

四激振器激励下振动机械⁃物料系统同步控制

针对振动机械-物料系统中激振器的转速和相位的同步控制问题,建立了考虑物料作用力的4个激振器激励下振动系统的动力学模型。考虑到相邻激振器之间存在耦合动力学特性,提出了一种精确的相邻交叉耦合策略控制方法来控制振动系统,并通过Lyapunov稳定性定理验证了相邻交叉耦合控制器的稳定性。Matlab仿真结果表明,所提出的相邻交叉耦合策略控制器可以降低感应电机启动阶段的速度过冲和速度稳定时的抖振,提高了控制精度。在考虑物料非线性力的振动系统中,相邻交叉耦合控制器控制4个反向旋转激振器,振动系统实现直线振动轨迹。最后,在振动系统中讨论了物料参数变化对相邻交叉耦合控制器的影响,说明相邻交叉耦合控制器的有效性。     

ZG型惯性振动给料机的动力学研究

根据物料运动理论对振动给料饥工作面运动的分析，对ZG型惯性振动给料饥进行动力学研究，得出单轴卧式和立式惯性振动给料机动力学分析方程和运动曲线图，并对这两种不同安装方式进行分析比较．得出单电机立式安装优越于卧式，完全能满足现场需要。     

电磁振动给料器给料速度影响因素的探讨

介绍了电磁振动给料器的组成及工作原理,建立了振动微分方程求得料斗的振动位移,进而得到了料斗速度、加速度.通过对物料在料斗振动时的受力和运动情况进行分析的基础上,建立了物料相对于料槽运动微分方程,求解方程得到了物料相对料槽的平均速度.并进一步对影响平均速度的几个因素进行了分析,提出了物料在连续滑移条件下的最佳振幅、振动方向角和料槽平均升角的确定依据,从而为电磁振动给料器的重量,电磁铁的气隙、电压,主振弹簧刚度设计提供了依据.     

Optimization of electrical discharge machining characteristics of WC/Co composites using non-dominated sorting genetic algorithm (NSGA-II)

Electrical discharge machining (EDM) is a process for shaping hard metals and forming deep and complex shaped holes by arc erosion in all types of electro conductive materials. In the present work, the effectiveness of the EDM process with tungsten carbide and cobalt composites is evaluated in terms of the material removal rate and the surface finish quality of the workpiece produced. The objective of this research is to study the influence of operating parameters of EDM such as pulse current, pulse on time, electrode rotation and flushing pressure on material removal rate and surface roughness. The experimental results are used to develop the statistical models based on second order polynomial equations for the different process characteristics. The non-dominated sorting genetic algorithm (NSGA-II) has been used to optimize the processing conditions. A non-dominated solution set has been obtained and reported.     

An experimental study of elastohydrodynamic central and minimum film thicknesses for various material parameters

A newly developed experimental technique, based on colorimetric interferometry, has allowed accurate measurement of central and minimum elastohydrodynamic (EHD) film thickness for a wide range of operating conditions. This study was aimed at determining the influence of various material parameters on central and minimum EHD film thicknesses. Obtained experimental data were compared with Hamrock and Dowson film thickness equations and a numerical solution presented by Venner. The results obtained confirmed that the ratio between the central and minimum film thicknesses changes significantly with both load and material parameters.     

A statistical method for evaluating structural reliability and minimum structural creep life at elevated temperature

A study of the observed scatter of time for creep rupture of a given structural material, operating under identical conditions of stress and temperature, is given, using probabilistic concepts. Reliability functions for creep rupture time and also for the corresponding minimum creep rupture time for structural materials, under known conditions of temperatures and stresses are given, in terms of the empirical physical and chemical parameters of the materials. The reliability function is the probability of successful operation of the material, under the given operating conditions. Tables and graphs are prepared which enable easy applications of the results to be made on simple practical problems.     

基于扩展一阶混合Petri网的机械制造系统碳流动态建模方法

机械制造系统是生产与能源的强耦合系统.针对其耦合特性,提出一种基于扩展一阶混合Petri网的碳流动态建模方法.对机械制造系统碳流动态特性进行分析,建立相应的系统边界,由系统边界分析制造系统的生产构成、运行模式,并导出能量、物料平衡方程以及碳排放量计算公式,为模型的建立奠定数量分析基础.针对机械制造系统能耗的连续性及离散状态对连续过程的影响等,在原一阶混合Petri网的基础上,引入控制弧、抑制弧相关元素以增强建模语义,并给出模型的形式化定义及规则说明.以某制造系统自动生产线为例,建立相应的多目标函数及约束条件,仿真优化其能量流、物料流的时域特性,并计算碳排放量,对所建模型进行验证,为企业实施低碳制造奠定一定的理论基础.     

Formulas Used in Thermal Elastohydrodynamic Lubrication

A numerical solution to the problem of thermal compressible elastohydrodynamic lubrication of rolling/sliding contacts has been tested over a wide range of operating parameters consisting of dimensionless load, speed, slip, and material parameters. A least squares exponential curve fit was used to develop simple formulas for the amplitude and location of the pressure spike, the minimum film thickness, and the maximum lubricant temperature as a function of the operating parameters. These equations can be used to evaluate parameters affecting the performance of rolling/sliding heavily loaded lubricated contacts.     

振动流化床干燥机的振型分析

为了研究LHZC6/60型振动流化床干燥机主要模态的特性,对干燥机进行简化,建立有限元模型。利用有限元分析软件ANSYS对干燥机进行了模态分析,求出干燥机的前8阶固有频率和振型图。通过分析干燥机的振型图得到振动流化床干燥机的动态特性和其结构的薄弱环节,这为该机结构的改进设计和动态分析提供了理论依据。     

便携式压力容器压力管道干燥机的设计

针对当前压力容器和压力管道的工程实际,提出便携式压力容器压力管道干燥机的设计方案,并进行了相关的探讨和研究,开发出由用户自主定温、仪器自行控温的热空气吹扫干燥机.使用结果表明,用该套设备进行干燥更节约,更方便.     

膨胀干燥机螺杆轴断裂失效分析

膨胀干燥机螺杆轴是一种呈悬臂状态工作的旋转轴,实际使用中常发生断裂事故。对该轴的断裂原因进行了失效分析。结果表明：螺杆轴断裂的主要原因是由于35CrMo材料承受介质的腐蚀和交变载荷作用而引起的腐蚀疲劳,而轴材料中的缺陷及其热处理工艺不当也是造成轴断裂的原因之一。在失效分析的基础上提出了解决问题的方法,经实际验证该方法可使轴的工作寿命得到大幅度提高。     

Experimental Study of Central and Minimum Elastohydrodynamic Film Thickness by Colorimetric Interferometry Technique

Recently developed colorimetric interferometry technique was used for the study of both minimum and central film thicknesses for a wide range of operating parameters. Over 300 film thickness maps were obtained for the combination of four values of the materials parameter G, five values of the load parameter W and many values of the speed parameter U. The use of a spacer layer extended the range of film thickness measurement down to 5 nm. An excellent agreement was found between experimental values and data obtained from numerical solution presented by Venner and ten Napel, especially for thin lubrication films. An increase in a speed exponent with increasing material parameter G was observed for both central and minimum film thicknesses. The minimum film thickness and, thereby, the ratio between central and minimum film thickness was confirmed to be of a stronger dependence on material and load dimensionless parameters than Hamrock and Dowson equations predict.     

Lateral Vibration Analysis of Flexible Shafts Supported on Elliptical Journal Bearings

This paper presents the development of a finite element procedure for the dynamic analysis of flexible rotors supported on fluid-film elliptical journal bearings operating under several operating conditions. The rotating shaft is modeled by using Timoshenko beam theory and the coupled rotating components, such as disks and impellers, are modeled by using lumped masses. The modeling of the elliptical journal bearings is performed by solving the lubrication equations generated from the application of a linearized perturbation method on the classical Reynolds equation. The bearing carrying-load capacity and the linearized dynamic force coefficients can be predicted for elliptical bearings with different preloads and journal eccentricities. The rotor transient whirling unbalance response is estimated by performing the time integration of the finite element equations using Newmark method. Experimental whirling unbalance response of a rotating shaft supported at two identical journal bearings is used to validate the finite element procedure. A comparative analysis of the dynamic response of flexible rotors supported on both cylindrical and elliptical journal bearings is performed to show that some elliptical bearings are capable of attenuating the rotor unbalance response more efficiently than cylindrical bearings are.