Improvement for design of beam structures in large vibrating screen considering bending and random vibration

Demand for large vibrating screen is huge in the mineral processing industry. As bending and random vibration are not considered in a traditional design method for beam structures of a large vibrating screen, fatigue damage occurs frequently to affect the screening performance. This work aims to conduct a systematic mechanics analysis of the beam structures and improve the design method. Total motion of a beam structure in screening process can be decomposed into the traditional followed rigid translation(FRT), bending vibration(BV) and axial linear-distributed random rigid translation(ALRRT) excited by the side-plates. When treated as a generalized single-degree-of-freedom(SDOF) elastic system analytically, the BV can be solved by the Rayleigh's method. Stochastic analysis for random process is conducted for the detailed ALRRT calculation. Expressions for the mechanics property, namely, the shearing force and bending-moment with respect to BV and ALRRT, are derived, respectively. Experimental and numerical investigations demonstrate that the largest BV exists at the beam center and can be nearly ignored in comparison with the FRT during a simplified engineering design. With the BV and FRT considered, the mechanics property accords well with the practical situation with the maximum error of 6.33%, which is less than that obtained by traditional method.

Complicated motion of particles on vibration screen surface

The particles’ motion on screen surface was studied by the way of nonlinear dynamics. It was found that the particles’ motion may be changed from one form to another with its vibration strength. When the vibration strength K is bigger than 1 and smaller than 1. 33, the particles’ motion is the bifurcating type;when K is bigger than 1. 33 and smaller than 1. 67, its motion becomes the double bifurcation type; when K is bigger than 1. 67, its motion changes into chaos motion type. On basis of studying all effects of large vibration strength on particles penetrating, it was pointed out that a larger vibration strength K of screen surface will increase the strength of particles’ motion, and then increase their probability of penetrating screen surface. A primary theory of particles’ motion under large vibration strength for moisture fine coal was established.

Influence of vibration mode on the screening process

The screening of particles with different vibration modes was simulated by means of a 3D discrete element method (3D-DEM). The motion and penetration of the particles on the screen deck were analyzed for linear, circular and elliptical vibration of the screen. The results show that the travel velocity of the particles is the fastest, but the screening efficiency is the lowest, for the linear vibration mode. The circular motion resulted in the highest screening efficiency, but the lowest particle travel velocity. In the steady state the screening efficiency for each mode is seen to increase gradually along the longitudinal direction of the deck. The screening efficiency increment of the circular mode is the largest while the linear mode shows the smallest increment. The volume fraction of near-mesh size particles at the underside is larger than that of small size particles all along the screen deck. Linear screening mode has more near-mesh and small size particles on the first three deck sections, and fewer on the last two sections, compared to the circular or elliptical modes.

Trispectrum and correlation dimension analysis of magnetorheological damper in vibration screen

In order to improve the screening efficiency of vibrating screen and make vibration process smooth,a new type of magnetorheological (MR) damper was proposed. The signals of displacement in the vibration process during the test were collected. The trispectrum model of autoregressive (AR) time series was built and the correlation dimension was used to quantify the fractal characteristics during the vibration process. The result shows that,in different working conditions,trispectrum slices are applied to obtaining the information of non-Gaussian,nonlinear amplitude?frequency characteristics of the signal. Besides,there is correlation between the correlation dimension of vibration signal and trispectrum slices,which is very important to select the optimum working parameters of the MR damper and vibrating screen. And in the experimental conditions,it is found that when the working current of MR damper is 2 A and the rotation speed of vibration motor is 800 r/min,the vibration screen reaches its maximum screening efficiency.

Kinetic model of vibration screening for granular materials based on biological neural network

The kinetic model is the theoretical basis for optimizing the structure and operation performance of vibration screening devices.In this paper,a biological neurodynamic equation and neural connections were established according to the motion and interaction properties of the material under vibration excitation.The material feeding to the screen and the material passing through apertures were considered as excitatory and inhibitory inputs,respectively,and the generated stable neural activity landscape was used to describe the material distribution on the 2D screen surface.The dynamic process of material vibration screening was simulated using discrete element method(DEM).By comparing the similarity between the material distribution established using biological neural network(BNN)and that obtained using DEM simulation,the optimum coefficients of BNN model under a certain screening parameter were determined,that is,one relationship between the BNN model coefficients and the screening operation parameters was established.Different screening parameters were randomly selected,and the corresponding relationships were established as a database.Then,with straw/grain ratio,aperture diameter,inclination angle,vibration strength in normal and tangential directions as inputs,five independent adaptive neuro-fuzzy inference systems(ANFIS)were established to predict the optimum BNN model coefficients,respectively.The training results indicated that ANFIS models had good stability and accuracy.The flexibility and adaptability of the proposed BNN method was demonstrated by modeling material distribution under complex feeding conditions such as multiple regions and non-uniform rate.

A virtual experiment showing single particle motion on a linearly vibrating screen-deck

A virtual sieving experimental simulation system was built using physical simulation principles.The effects of vibration frequency and amplitude,the inclination angle of the screen-deck and the vibration direction angle of screen on single particle kinematics were predicted.Properties such as the average velocity and the average throw height were studied.The results show that the amplitude and the angle of vibration have a great effect on particle average velocity and average height.The vibration frequency and the screen-deck inclination angle appear to have little influence on these responses.For materials that are difficult to screen the vibration frequency and amplitude,the screen-deck inclination angle and the vibration angle should be set to 14 Hz,6.6 mm,6° and 40°,respectively,to obtain optimal particle kinematics.A screening process can be simulated reliably by means of a virtual experiment and these results provide references for both screening theory research and sieving practice.

Dynamic analysis and simulation of four-axis forced synchronizing banana vibrating screen of variable linear trajectory

A new concept of banana vibrating screen which has the same effect as traditional banana vibrating screen in a new way was put forward.The dynamic model of vibrating screen was established and its working principle was analyzed when the action line of the exciting force did not act through the centroid of screen box.Moreover,the dynamic differential equations of centroid and screen surface were obtained.The motions of centroid and screen surface were simulated with actual parameters of the design example in Matlab/Simulink.The results show that not only the amplitude has a significant decrease from 9.38 to 4.10 mm,but also the throwing index and vibrating direction angle have a significant decrease from 10.49 to 4.59,and from 58.10° to 33.29°,respectively,along the screen surface,which indicates that motion characteristics of vibrating screen are consistent with those of traditional banana vibrating screen only by means of a single angle of screen surface.What's more,such banana vibrating screen of variable linear trajectory with greater processing capacity could be obtained by adjusting the relative position of force center and the centroid of screen box properly.

Dynamic simulation on rubber spring supporting equipment of vibrating screen

By ANSYS, dynamic simulation analysis of rubber spring supporting equipment used in vibrating screen was made. The modal frequency, mode, and harmonic displacement under working frequency were obtained. Variation of rubber spring supporting equipment＇s dynamic performance was discussed first, which is under the condition of existing spring stiffness difference and exciting force bias. Also, the quantitative calculation formulas were given. The results indicate that the performance of vibrating screen is closely related with rubber spring supporting equipment＇s dynamic performance. Differences of springs＇ stiffness coefficients reduce the modal frequency reduced, decrease the dynamic stiffness, and increase vibration displacement. Exciting force bias induces a larger lateral displacement. When rubber springs＇ stiffness coefficients exist, differences and lateral force accounts for 5% in total exciting force; rubber spring supporting equipment＇s side swing is larger than 1 mm, exceeding the side swing limit.

Static-deformation based fault diagnosis for damping spring of large vibrating screen

Based on the statics theory, a novel and feasible twice-suspended-mass method(TSMM) was proposed to deal with the seldom-studied issue of fault diagnosis for damping springs of large vibrating screen(LVS). With the static balance characteristic of the screen body/surface as well as the deformation compatibility relation of springs considered, static model of the screen surface under a certain load was established to calculate compression deformation of each spring. Accuracy of the model was validated by both an experiment based on the suspended mass method and the properties of the 3D deformation space in a numerical simulation. Furthermore, by adopting the Taylor formula and the control variate method, quantitative relationship between the change of damping spring deformation and the change of spring stiffness, defined as the deformation sensitive coefficient(DSC), was derived mathematically, from which principle of the TSMM for spring fault diagnosis is clarified. In the end, an experiment was carried out and results show that the TSMM is applicable for diagnosing the fault of single spring in a LVS.

Application of experimental modal analysis technique to structural design of linear vibrating screen

A large model of the screen was mounted in the laboratory for studying its modal performance. The model is suspended with steel ropes. Modal test was carried out with artificially exciting by 500 g impacting hammer and 100 kg exciting force shaker respectively. Synthesis and correction of the modal parameters are obtained from both testing methods. Design faults of vibrating screen were determined based on the analy-sis and dynamic correction of structure approaches about the screen was put forward finally.

Research on CAD of Activatorof Vibrating Screen

Based on Autodesk Mechanical Desktop (MDT), three main. approaches of parametric part design including program-drive, table-drive and interactive-drive were studied. By using Visual Basic and ActivesX automation component programming, access database, parametric drawing and mechanism analysis were integrated. h probes into how to design mechanical products quickly and effectively by means of CAD.

A Time History Method for Analysing Operational Piping Vibrations

Vibration failure of piping is a serious problem and a matter of concern for safety and reliability of plant operations. Fatigue is the main cause of such failures. Due to the complexity of the phenomenon no closed form design solutions are available. In our study an analytical technique based on the theory of vibrations in the time domain has been presented. Using the inverse theory, the problem has been reduced to a system of Volterra Integral equations to be solved simultaneously at every time step. The solution of the inverse problem may be used in the conventional method to calculate stresses and end reactions which are important from the perspective of engineering design and condition monitoring. The method is robust, simple and can be easily adopted by practicing engineers.

基于TOF相机的振动筛上物料状态动态监测方法

振动筛筛上物料载荷异常不仅影响生产效率还可能导致安全隐患,实时准确地监测筛上物料状态具有重要意义。针对传统人工监测方法劳动强度大、速度慢、有极高安全隐患并且不容易发现设备微小故障等问题。基于TOF相机物料动态监测技术,提出了一种联合KD树与帧差法的点云数据补全方法和基于曲面重构的筛上物料动态监测方法。该点云数据补全方法有效修补了因筛上物料表面水分和物料缝隙导致的TOF相机拍摄过程中的点云数据缺失问题,通过对补全后的筛上物料进行点云曲面重构分析,判断欠载、过载、左偏载和右偏载四种筛上物料状态,实时监测筛上物料状态。研究通过TOF相机直接获取筛上物料状态信息,对筛上物料实时检测,减少了人工干预的需求且具备实时性。为筛上物料状态实时监测问题提供了一个可靠的解决方案。

基于EDEM的核桃壳仁混合物振动筛分级工艺优化

为提高核桃壳仁混合物的分级效果,对现有核桃壳仁混合物分级设备进行三维实体建模,利用EDEM软件模拟核桃壳仁混合物的分级过程,以筛面上物料的运动速度、质量以及各等级颗粒在统计区域的数量为指标,以振幅、振动频率、振动方向角、筛面倾角为考察因素,对振动筛分级工艺进行优化。结果表明:在振动频率12 Hz、振幅5 mm、振动方向角45°、筛面倾角4°的工艺参数组合下,各等级核桃壳仁的透筛率最高,分级效果最好。

阻尼层敷贴法对钻井振动筛降噪效果的影响

针对钻井振动筛工作噪声问题,提出了在钻井振动筛筛箱侧板敷贴阻尼层以减弱其噪声辐射的方法。通过筛箱振声模型,采用有限元法和模态应变能法对侧板敷贴阻尼前后的振动模态和侧板声辐射进行分析,利用COMSOL进行仿真求解,比较分析了不同材料、不同厚度的阻尼层对筛箱表面噪声辐射的影响。研究表明,表面阻尼结构能减弱噪声辐射;敷贴较硬的材料能对侧板起到一定的振动约束作用;需要根据材料属性选取最佳厚度,达到最佳减振降噪效果。

基于活性炭颗粒的圆振动筛主要技术参数优化分析

为验证圆运动振动筛在对活性炭颗粒筛分时,振动筛各运动参数对筛分效率的影响,采用平均筛分效率来代表活性炭筛分效果。采用Box-Behnken响应面分析来研究圆运动振动筛的振动幅度、运动倾角以及振动频率对筛分效果的影响并进行仿真模拟,探讨3个因素之间对活性炭筛分的影响作用。验证结果表明:对筛分效果影响最大的是振动频率,影响最弱的是运动倾角,振动幅度和运动倾角之间具有显著影响作用,在振动幅度为4.21 mm、运动倾角16.07°以及振动频率13.83 Hz时筛分效果达到最大值40.86%。通过该方法优化的圆振动筛,可提高活性炭的筛分效率。

新型螺旋筛面旋振筛的参数优化

为研究螺旋筛面旋振筛的筛分效率与筛分参数之间的非线性关系,文章使用神经网络对其筛分参数综合寻优,得到最佳筛分参数及筛分效率。首先,建立不同结构参数的螺旋筛面旋振筛三维模型,利用离散单元法对其仿真模拟,获取不同参数下的筛分效率数据。然后,利用神经网络对样本数据进行训练、验证及得到预测数据。研究结果表明:通过神经网络的训练和测试,证明神经网络可以用于螺旋筛面旋振筛的参数优化;在螺旋升角为11.613°、振动频率为15.720 Hz、振动幅度为1.481 mm、螺旋圈数为1.468圈、内外径比值为0.256时,螺旋筛面旋振筛获得最佳筛分效率,并且优化了螺旋圈数,缩短了筛长。

面向筛面复杂背景的矿山异物视觉检测方法

矿山异物检测是异物智能化去除的前提,更是保障设备安全运行,矿山正常生产的关键。在矿山生产过程中,异物来源广泛,种类繁杂。针对传统的矿山异物检测方法面临适应性差和效率低的问题,提出了一种面向大型振动筛筛面的矿山异物检测算法模型。为解决强振动、矿石遮挡和粉尘水雾等复杂环境的干扰,该模型引入了改进的显式视觉中心模块(EVCBlock),轻量化上采样算子CARAFE和基于动态非单调聚焦机制的梯度增益损失函数WiseIoU-v3,有效提升了在复杂环境下的异物检测性能。利用TensorRT对模型优化并部署至边缘计算设备Jetson Xavier NX,实现了在边缘侧的异物检测。研究结果表明:该模型在振动筛筛面异物检测上的表现明显好于其他对比模型。经多线程视频推流测试,模型部署至边缘计算设备平均识别精确率可以达到96.3%,平均帧率达到25 FPS以上,满足了实际检测要求。

玉米亲本种子变幅振动式分级装置研制

针对玉米繁种阶段亲本种子播前分级效率低、筛面自净效果差的问题,该研究提出一种变幅振动筛分方法,并设计了种子分级振动筛装置,对驱动机构和自净清筛装置进行设计与分析。在喂入量2.5 kg/s的条件下,以京科968玉米种子为试验对象,以分级合格率、作业时间和卡种数量为试验指标,通过四因素(进料口高度、振幅、振动频率和筛面倾角)三水平Box-Behnken试验,建立各因素与试验指标间的回归模型,并对参数进行优化。结果表明,影响变幅振动式分级装置分级合格率的主次因素顺序为振动频率、筛面倾角、振幅和进料口高度,影响作业时间的主次因素顺序为振动频率、振幅、筛面倾角和进料口高度;卡种数量具有较大的随机性,当振幅和振动频率都较低时,筛面卡种数量急剧增多,自净效果极差。最优参数组合为进料口高度19 mm、振幅5 mm、振动频率8.25 Hz、筛面倾角7°,模型优化预测结果为分级合格率88.04%,作业时间40 s。在最优条件下的验证试验结果为分级合格率89.55%、作业时间39 s,平均卡种数量8粒,与预测结果基本一致,较等幅振动式分级装置的分级合格率提高3.25个百分点,作业时间减少4 s,平均卡种数量减少2粒,作业性能优于等幅振动式分级装置。分级装置分级效率达0.33 t/h,各项指标均满足相关设计要求。研究结果可为繁种阶段种子分级装备的设计提供参考。

加速度传感器的振动筛螺栓松动故障诊断系统

针对GLS10型直线振动筛弹簧紧固螺栓松动故障,结合软件LABVIEW和NIUSB-6363数据采集卡,构建一种基于加速度传感器的振动筛螺栓松动故障诊断系统。通过拧松固定螺栓个数的方法,模拟振动筛弹簧悬臂梁固定端松动故障。结果表明:当振动筛悬梁臂固定端松动时,其最大振幅明显减小,其幅度为原先幅值的53%,可以有效判断故障类型;当故障类型相同、故障程度不同时,分析得到的加速度信号图谱互不相同,且振幅差异明显,可根据振幅的阈值来判断螺栓松动的故障程度。