水平螺旋输送机输送规律及摩擦系数的影响研究

运用EDEM离散元软件对水平螺旋输送机进行模拟仿真,详细描述了颗粒物料在水平螺旋输送机中的分布规律、运动规律和速度分布情况,提出将颗粒物料分为以周向流动为主和以轴向流动为主两种类型;在输送方向上选择多个截面并分析各截面的质量流率,得出水平螺旋输送的稳定输送区段;研究了筒壁、绞龙叶片与颗粒间摩擦系数对颗粒分布及螺旋输送效率的影响规律,发现筒壁摩擦系数存在最优值,为水平螺旋输送机筒壁、绞龙叶片等设计提供理论参考。提出了一种,螺旋输送机筒内壁上表面开槽处理的方法,该方法在消耗相同能量的基础上,提高了输送效率。     

摊铺机变径变螺距螺旋分料器抗离析研究

从摊铺机螺旋分料器布料过程中沥青混合料的力学特性和输送机理出发,采用流体力学及动力学对混合料在螺旋分料器中的受力、加速度、摩擦力及运动规律进行理论分析.得出了导致沥青混合料产生离析的技术原因和改进措施,提出了变径变螺距螺旋分料器的设计方法.在保证料流均匀的情况下,研究螺旋分料器工作转速、螺径/螺距比对混合料离析的影响,探讨螺旋分料器各工作参数与对物料输送性能之间的关系.建立了变径变螺距螺旋分料器参数化设计的计算模型,为变径变螺距螺旋分料器的结构设计提供了理论依据.     

振动力场强化单螺杆挤出固体输送的离散单元法模拟

将岩石力学中的研究方法——离散单元法引入塑料挤出固体输送研究中，并建立了固体输送段的离散输送模型。该模型可以从微观上分析聚合物颗粒在挤出过程中的受力和运动，也可以从宏观上描述整个颗粒体系的运动规律。模型能体现振动力场对强化单螺杆挤出固体输送的影响，反映电磁动态挤出机固体输送段的输送规律，为新型设备的设计应用提供理论支持。     

开式螺旋输送原理分析与参数设计

对开式螺旋输送机的输送机理进行了分析探讨,选取开式螺旋输送机内单颗物料为研究对象进行分析,通过运动学与动力学分析,得出了输送过程中散体物料的受力及运动情况,推导出开式螺旋输送机主要参数设计准则,得出主要参数设计及校验公式,为开式螺旋输送机的工作参数和结构参数的选择和确定提供了理论依据,完善了开式螺旋输送理论,有助于开式螺旋输送机的设计、制造、应用和推广。     

螺旋垂直振动输送干燥机的研究与设计

本文应用振动机械的理论,以振动电机为激振源、对化肥、化工、冶金等行业生产中物料的加热输送过程二机合一.设计出了新一代螺旋振动输送干燥机.本文简述了其工作原理、运动及工艺参数选择,并进行了同步理论分析及物料抛掷过程中的周期性分析,已在生产实践中得以验证.     

沥青混合料转运车性能试验研究

在分析沥青混合料转运车的工作原理及作用的基础上,通过理论分析螺旋搅料器搅拌输送沥青混合料的运动特性,并通过模型试验,研究了螺旋的螺距S、半径r对改善沥青混合料离析程度的影响,揭示了评价搅拌输送效能、质量的重要指标——离析系数及其随螺旋分料器结构参数、运动参数变化的依存关系,得出了螺距及螺旋半径之间的最佳关系,为沥青混合料转运车的设计开发提供科学可靠的依据.     

矿用螺旋输送混凝土的数值模拟

借助Fluent软件对混凝土在螺旋输送装置内的输送过程进行数值模拟,探讨了螺旋输送装置的转速、螺径比对其输送过程的影响规律,通过面积平均加权函数ea、质量流量、功能损耗三个方面评价了混凝土螺旋输送性能的优劣.仿真结果表明:螺旋输送装置的转速为90 r/min～100 r/min、螺径比约为1时,在保证其输送过程中的混合...     

螺旋卸船机取料机理分析

本文以螺旋卸船机的相对旋转式取料装置为研究对象，分析了物料在进料过程中的运动性态与受力性态，提出了判别物料进入取料翼板的条件，导出了物料运动参数的计算方法，进而建立了取料装置充填率的计算模型，它反映出取料装置结构尺寸，取料管转速以及输送段物料运动特性对取料性能的综合影响。本文在一定程度上揭示了当取料管与垂直输送螺旋反向旋转情况下物料运动的规律性，并通过模型试验进行了验证。     

缓凝砂浆在单螺旋输送中的ANSYS流场研究与分析

应用ANSYS软件,在宾汉姆体缓凝砂浆螺旋输送理论和单螺杆挤出机中流场的数值研究基础上,以一个螺旋长度为对象,对挤出机中的流体进行了模拟.结合假设经过简化和边界处理,得出单螺杆挤出机中缓凝砂浆的三维流场.根据所得流场分析结果,确定流动"死区"的存在,为输送理论和数值流场分析的结论提供可视化验证方法,同时为机件的设计提供参考.     

基于高速摄像与PIV技术的喷丸丸粒运动特征研究

喷丸作为一种重要的金属表面机械处理工艺，其加工质量与固体丸粒在高速气流作用下的运动规律密切相关。探究一种精确可行的喷丸丸粒速度测量方法，明确喷丸丸粒流的空间散射特征和速度场分布特征，对于优化喷丸工艺参数至关重要。基于高速摄像机，搭建了喷丸丸粒运动高速图像数据采集系统，捕捉喷丸中丸粒的瞬时空间位置变化特征。采用Photoshop图像处理软件对采集的照片进行预处理，获得具有高对比度的丸粒流黑白二值化图片。使用开源的粒子图像测速(Particle Image Velocimetry, PIV)软件PIVLab对丸粒流图像进行数据处理，获得喷丸丸粒流的速度场结果。结果表明，在喷气压力为0.4 MPa,采用0.4 mm铸钢丸粒条件下，丸粒流的散射锥体倾角为10°,丸粒最大运动速度约为46.5 m/s。在不同的空间截面上，丸粒运动速度呈现高斯分布特征，且其标准差随丸粒与喷嘴之间的距离增大而增大。丸粒在离开喷嘴后速度迅速增长至稳定值，速度变化符合Logistic函数特征。与经验公式相比，所得到的丸粒速度场分布公式更加准确，且能体现丸粒的空间分布特征。     

基于旋量理论的装配模型中零件瞬时运动分析

提出一种直接根据装配模型中零件几何信息和空间配置关系分析其零件瞬时运动特性的方法。该方法首先对不同零件CAD模型中面几何方程进行比较得到零件之间的面-面接触关系和类型,并应用旋量理论将面-面相对瞬时运动表示为螺旋;然后,对多个面接触上的螺旋进行交运算,生成零件之间的相对瞬时运动螺旋;最后,根据零件邻接关系图和邻接零件相对运动螺旋,对装配模型中零件整体瞬时可动性和驱动关系进行了分析,给出不相邻零件之间的相对瞬时运动螺旋计算方法和它们之间可驱动性的判断方法。论文通过实例验证了该方法的正确性及有效性。     

全方位装配机器人的刚度误差分析

为了提高工作效率并节约劳动力,设计了一种可执行装配任务的全方位装配机器人,此机器人能在实际工程中执行一些简单的装配任务。为提高机器人在执行装配作业任务时的装配精度,对其刚度误差进行分析。根据机器人的结构特点并结合旋量理论对并联机构各支链进行建模,推导出机器人的刚度模型。通过仿真分析得出了支链长度以及载荷对系统刚度的理论影响。结合实验测试对刚度矩阵进行修正,得出不同姿态下系统刚度引起的误差。详细分析误差的产生的原因,提出了减小误差的改进方案。     

Electrostatic precipitability of the coal fly-ash by the pilot scale test

The equation of the particle collection efficiency proposed by Deutsch has been modified through the various experiments to correct the errors caused by the assumptions made for the equation. In order to get an modified Deutsch equation that can be applied to real conditions, a pilot scale electrostatic precipitator is used. The effects of operational variables on the particle collection efficiency are evaluated. Particle resistivity, gas temperature, moisture contents in gas, gas velocity and particle concentration are used as the operational variables. Two different types of coal fly-ash obtained from the fluidized bed combustor and the pulverized coal combustor are used as test particulate to evaluate the effect of the physiochemical and electrical characteristics of the particle on the particle collection efficiency. The experimental results are fitted with the modified Deutsch equation made by Matts-Öhnfeldt and the extended Deutsch equation made by E. C. Potter to evaluate the effect of the particle characteristics and the operational conditions on the particle collection efficiency of the electrostatic precipitator.     

Momentum transmission of a diaphragmed magnetic spectrometer: I. Analysis and definitions

An experimental device consisting of a plane source of charged particles and of a magnetic spectrometer equipped with horizontal and vertical diaphragms is considered. An analysis intended to achieve an exact analytical expression to connect the observed particle flux to the source emission and spectrometer transmission characteristics is developed. An analytical expression for the average value of the source brightness that is actually obtained from corpuscular flux measurements is also given. The effectiveness of the diaphragms in defining the domains of the initial conditions of the particles is also emphasized and general definitions of these domains are introduced. These definitions are stated for exact optical transformations, i.e., accounting for geometric and chromatic aberrations, and for general positions of the diaphragms along the optical axis as well as for symmetrical or asymmetrical apertures of the same. The results obtained and the introduced definitions will be used in Part II of this work. The important case of a thick source is considered in Appendix A.     

Acceleration-Dependent Analysis of Vertical Ball Screw Feed System without Counterweight

The distinguishing feature of a vertical ball screw feed system without counterweight is that the spindle system weight directly acts on the kinematic joints.Research into the dynamic characteristics under acceleration and decel-eration is an important step in improving the structural performance of vertical milling machines.The magnitude and direction of the inertial force change significantly when the spindle system accelerates and decelerates.Therefore,the kinematic joint contact stiffness changes under the action of the inertial force and the spindle system weight.Thus,the system transmission stiffness also varies and affects the dynamics.In this study,a variable-coefficient lumped parameter dynamic model that considers the changes in the spindle system weight and the magnitude and direc-tion of the inertial force is established for a ball screw feed system without counterweight.In addition,a calculation method for the system stiffness is provided.Experiments on a vertical ball screw feed system under acceleration and deceleration with different accelerations are also performed to verify the proposed dynamic model.Finally,the influence of the spindle system position,the rated dynamic load of the screw-nut joint,and the screw tension force on the natural frequency of the vertical ball screw feed system under acceleration and deceleration are studied.The results show that the vertical ball screw feed system has obviously different variable dynamics under acceleration and deceleration.The influence of the rated dynamic load and the spindle system position on the natural frequency under acceleration and deceleration is much greater than that of the screw tension force.     

浅谈螺纹锁固胶的选型与应用

螺纹联接是一种可拆卸的固定联接,具有结构简单、联接可靠、拆装方便等优点。螺纹联接包含拧紧技术与防松技术,螺纹联接防松的方法很多,如机械防松、摩擦防松、螺纹锁固胶防松等,其中,螺纹锁固胶防松技术具有高效、便捷、可靠、成本低等特点,已在机械行业得到广泛的应用。重点阐述了在众多螺纹锁固胶产品的背景下,企业如何正确地选型与应用螺纹锁固胶。     

Three-dimensional finite element analysis of the mechanical properties of helical thread connection

Conventional analytical and numerical methods for the mechanical properties of helical threads are relied on many assumptions and approximations and thus hardly yield satisfied results. A parameterized 3D finite element model of bolted joints with real helical thread geometry is established and meshed with refined hexahedral elements. The Von Mises plasticity criterion, kinematic hardening rule of materials and interfacial contacts are employed to make it possible for the suggested model be able to approach real assembly conditions. Then, the mechanical properties of bolted joints with different thread pitches, thread numbers and modular ratios are investigated, including the contact pressure distribution at joint interfaces, the axial load distribution and stress concentration in screw threads during the loading and unloading process. Simulation results indicate that the load distribution in screw threads produced by the suggested model agrees well the results from CHEN’s photoelastic tests. In addition, an interesting phenomenon is found that tightening the bolt with a large preload first and then adjusting the clamping force by unloading can make the load distribution more uniform and reduce the maximum residual equivalent stress in thread roots by up to 40%. This research provides a simple and practical approach to constructing the 3D finite element model and predicting the mechanical properties of helical thread connection.     

Particle swarm optimization for minimizing assembly variation in selective assembly

Quality of a product is based on the quality of the mating parts. When the parts are assembled interchangeably, the assembly variation will be the sum of the component tolerances. If the assembly variation is to be less than the sum of the component tolerances, selective assembly is the only solution. In conventional selective assembly, the corresponding selective groups are assembled. In this paper, selective group combinations for assembling the mating parts is obtained using particle swarm optimization (PSO). The combination obtained has resulted in an appreciable reduction in assembly variation. The proposed algorithm has been demonstrated for a linear assembly, which consists of three components having equal dimensional distributions. The assembly variation obtained by interchangeable assembly is 36 μm. By implementing the proposed method, the assembly variations are reduced from 36 to 7.2 μm. However, this algorithm can be extended for assemblies with more number of components and with different dimensional distributions.     

Note: A microfluidic chip setup for capillarity-assisted particle assembly

We developed a microfluidic chip setup for capillarity-assisted particle assembly (CAPA). A capillary bridge is formed between the aperture of a silicon chip and the assembly template. The bridge is fed with particle suspension through a microfluidic channel on the chip top side. With this setup, we can control the particle assembly location and tune the suspension composition during particle assembly. In this note, we describe the chip setup, the CAPA process using the microfluidic chip, and results of complex particle assemblies, such as composite particle arrays and particle gradients, that could not be obtained using a conventional CAPA setup.     

球形物料螺旋输送能力影响因素的试验分析

为获得粒子冲击钻井技术中关键设备钢球螺旋输送机输送量计算的经验公式,对影响输送量的相关因素如螺槽深度、螺杆和筒壁表面质量、物料粒径大小、螺杆与筒壁的间隙等因素,进行了相关的试验研究。试验结果表明：输送能力随着螺槽深度的增加而增强,筒壁和螺杆表面质量的高低对球形物料输送能力的影响很小,粒径大小和颗粒表面光滑程度对输送能力有一定的影响;螺杆与筒壁的间隙越大,输送能力越差。最终根据试验结果,得出钢球螺旋输送机的输送量计算的经验公式,并通过粒子反流试验装置中的钢球螺旋输送机进行了验证,可为后续装置的应用设计和设备制造提供指导。