Optimization experiment on eccentric lapping of cylindrical rollers

Cylindrical rollers are important elements of bearings,and their machining accuracy and consistency affect the bearing quality.Using a GCr15 cylindrical roller ofФ11×12 as the processing object in this study,the effects of loading pressure,abrasive concentration,and speed combination on cylindrical roller machining precision were investigated using the orthogonal experimental design method on a double-side eccentric pendulum lapping and polishing machine.The machining parameters of the lapping stage were optimized,and the lapping optimal process parameters were determined by S/N response analysis and analysis of variance(ANOVA).The results show that when the experiment was optimized using loading pressure of 10 N/roller,abrasive concentrationof 20.0 wt%,and rotational speed combination,the material removal rate(MRR)of cylindrical roller reached 0.0896μm/min;the average roughness of the batch decreased from 0.056μm to 0.027μm,51.8%lower than the original batch average roughness,and the deviation decreased from the initial 0.022μm to 0.014μm;the batch average roundness error decreased from 0.47μm to 0.28μm,40.4%lower than the original batch average roundness error,and the deviation decreased from the initial 0.19μm to 0.038μm;and the batch average diameter variation decreased from 4.5μm to about 3.6μm,20%lower than the original batch average diameter variation.The double-side eccentric lapping of cylinder rollers does not only lead to improvement in the surface quality and shape accuracy of rollers,but also improvement in the batch consistency.     

Model Building of Backup Roller Diameter Effect Rate in 4-High Mill

Software for calculating the strip profile in 4-high hot rolling mill was developed using influence coefficient method. Regularity of backup roller diameter effect rate was studied systematically using the software. The results show that backup roller diameter effect rates decrease versus the increase of strip width, increase significantly versus the increase of backup roller diameter and obscurely increase versus the increase of reduction. The difference between backup roller diameter effect rate and it is reference value increases versus strip width increasing. When backup rollers diameter is set to be 1.64 m and strip width is 1.85 m, the error of strip profile calculated using the model of backup roller diameter effect rate reference value will be 3.55μm. Based on the results, reference values of roller diameter effect rate and six power polynomial fitting coefficients of modification coefficients were determined considering coherent parameters. The high precision model of backup roller diameter ef     

In vitro biocompatibility evaluation of silk-fibroin/polyurethane membrane with cultivation of HUVECs

In order to investigate the in vitro biocompatibility of a novel polyurethane （PU） membrane modified by incorporation of superfine silk-fibroin powder （SFP）, which was prepared for small-diameter vascular grafts, with the cultivation of human umbilical vein endothelial cells （HUVECs）, PU and SFP were mixed with the ratios of 9：1, 7：3, 5：5, 3：7 （PU：SFP） to make four composite materials. Unmodified PU and polytetrafluoroethylene （PTFE） were added as control groups. CCK-8 assay was used to evaluate the cytotoxicity of these biomaterials. Data were processed using SPSS, and P〈 0.05 was considered to be statistically significant. Adherence and spreading of HUVECs on the surface of specimens was observed using direct contact cultivation. The toxicity ratings of the novel composites were grade 0-1, which is in the acceptable range. In all the experimental groups except control, SFP/PU with ratio of 1：9 had the least cytotoxicity property, and more content of SFP in the composite showed no improvement of the biocompatibility. HUVECs strongly attached to and grew on the surface of the biomaterials, and proliferated rapidly. The proliferation ability increased with increased proportion of SFP; however the cell quantity on the surface of the materials decreased when the proportion of SFP was equal to or larger than that of PU in the composite. It is concluded that this novel material has excellent cellular affinity with no cytotoxicity to HUVECs. Adding SFP gives PU better biocompatibility, while further research on optimum blend ratios is still needed.     

Discussion on bearing capacity of soft rock ground based on in situ load test

This paper explores five methods of bearing capacity of soft rock foundation based on in-situ load test, namely, point of contraflexure method, relative settlement method, rebound method based on elastoplasticity theory, hyperbola fitted method and minimum curvature radius method. The suitability of various methods was discussed on the basis of the typical results from in-situ load test of Renshou mansion and Caifu plaza in YueYang. It shows that the bearing capacity can be obtained by the proportion load and limit load from p-s curve with first and second point of contraflexure easily. The accurate value of bearing capacity could be obtained by hyperbola fitted method and minimum curvature radius method theoretically, so it is recommended. The rebound method is clear in principle, in which the elastoplasticity characteristic was thought about, and it is recommended, too. Out of consideration for the unsteadiness and unobviousness of bearing capacity from relative settlement method, it can be only adopted as reference. So bearing capacity of soft rock foundation should be decided by weathering condition of soft rock and curve type.     

Structural Analysis and Improved Design of the Gearbox Casing of a Certain Type of Tracked Vehicle

Loads on a gearbox casing of a certain type of tracked vehicle were calculated according to the engine’s full load characteristic curve and the worst load condition where the gearbox operated while the tracked vehicle was running,and then stiffness and strength of the casing were analyzed by means of Patran/Nastran software.After analysis,it was found that the casing satisfied the Mises’ yield condition;however,the stress distribution was heterogeneous,and stresses near the bearing saddle bores of the casing were higher while those in other regions were much less than the allowable stress.For this reason,thicknesses of the casing wall on bearing assembling holes needed increasing,while those in other places can decrease.After much structural improving and re-analysis,the optimal casing design was found,and its weight decreased by 5%;the casing still satisfied the Mises yield criterion and the stress distribution was more homogeneous.     

Uniform texture in Al-Zn-Mg alloys using a coupled force field of electron wind and external load

Cylindrical Al-Zn-Mg alloys were processed by electroplastic compression with forced air cooling.Compared to a simple compression process,an unequal intensity of {110} <111> was obtained,and other textures were eliminated by electroplastic compression,that is,electroplastic compression can promote a uniform texture.The various textures formed in different regions along the radial direction under a simple compression process were illuminated by analyzing the relationship between the crystal rotation and stress state.Furthermore,the interaction between the electrons and dislocations was studied in electroplastic compression.The electrons enhanced {110} <111> by promoting slipping of the dislocations when the Burgers vectors of the dislocations were parallel to the drift direction of the electrons.However,the electrons also inhibited crystal rotation by pinning the dislocations with the Burgers vectors perpendicular to the drift direction of the electrons.Therefore,textures other than {110} <111>have difficulty forming under electroplastic compression.The effect of the current energy on the texture(enhancement or attenuation) was in accordance with the law of conservation.The results provided reasonable explanations for the test phenomena.     

Photocatalytic Property of TiO2 Films Deposited by Pulsed DC Magnetron Sputtering

TiO2 thin films were prepared by DC magnetron sputtering with the oxygen flow rate higher than the threshold. The film deposited for 5 h was of anatase phase with a preferred orientation along the <220> direction, but the films deposited for 2 and 3 h were amorphous. The transmittance and photocatalytic activity of the TiO2 films increased constantly with increasing film thickness. When the annealing temperature was lower than 700℃, only anatase grew in the TiO2 film. TiO2 phase changed from anatase to rutile when the annealing temperature was above 800℃. The photocatalytic activity decreased with increasing annealing temperature.     

An Adaptive Model and Algorithm for an Electrohydraulic Position Servo System in Auto Gauge Control for Aluminum Hot Tandem Mill

The electrohydraulic servo position control system (HPC) is the core of an auto gap control for a modern fourhigh continuous hot strip mill. The actuators are loaded with considerable external disturbances, rolling forces, and the system stiffness and position accuracy will become hypersensitive to the leakage and the compressibility of the oil. Many efforts have being made to increase the position accuracies. The conventional resources are proportion integral differential (PID) controller. But the PID controller is faint for a considerable external disturbance. In this paper, by introducing the adaptive control strategy of model reference the reciprocities of the system structure with the loads were analyzed. With the Lyapunov energy function, an adaptive control algorithm applied to improve the system accuracy was formulated. The system simulations and the selection of parameters of the model were also discussed. The simulations show the static state errors at 0.02%. Finally, the industrial experimental result was given.     

Mechanical Properties and Fracture Behavior of Mg-Al/AlN Composites with Different Particle Contents

In this study, magnesium matrix composites reinforced with different loading of AlN particles were fabricated by the powder metallurgy technique. The microstructure, bending strength and fracture behavior of the resulting Mg-Al/Al N composites were investigated. It showed that the 5 wt% AlN reinforcements led to the highest densification and bending strength. The total strengthening effect of AlN particles was predicted by considering the contributions of CTE mismatch between the matrix and the particles,load bearing and Hall–Petch mechanism. The results revealed that the increase of dislocation density,the change of Mg17Al12 phase morphology, and the effective load transfer were the major strengthening contributors to the composites. The fracture of the composites altered from plastic to brittle mode with increasing reinforcement content. The regions of clustered particles in the composites were easy to be damaged under external load, and the fracture occurred mainly along grain boundaries.     

对转圆柱滚子轴承动态特性分析

针对内外圈对转圆柱滚子轴承内部复杂的运动特性及相互作用力,通过分析轴承径向游隙的影响因素以及考虑滚子与滚道的接触变形和热效应对油膜厚度的影响,利用拟静力学法建立了轴承的分析模型,并采用NewtonRaphson法进行求解;同时,利用该模型对滚子打滑率进行计算,以验证所采用分析方法的正确性和可靠性。然后,进一步探讨了不同工况下对转圆柱滚子轴承内部组件的转速变化规律与接触特性。结果表明：滚子的自转转速、滚子与滚道的接触载荷均随径向载荷的增大而增大;内、外圈转速变化会使受载区滚子与滚道的接触载荷以一定的规律重新分配,且转速对最小油膜厚度的影响较径向载荷更为明显。研究结果可为对转圆柱滚子轴承的结构优化和生热机理分析提供理论依据。     

偏载状态下轧机轴承接触力学模型研究

该文针对板带轧制过程偏载工况下滚动轴承接触力学模型进行研究。建立了支承辊四列圆柱滚子轴承的Hertz理想接触模型、基于柔度矩阵法的轴承偏载接触力学模型。针对辊间不同载荷进行了模型数值求解,仿真模拟了理想及偏载接触过程。研究表明:偏载运行状态严重影响各列轴承载荷分布,15°~30°位置角的滚动体承载最大,最大接触应力呈“M”形分布;仿真结果与数值模拟结果吻合程度较好,误差不超过15%,且略小于数值求解结果,在实际工程应用范围内;随着轧制载荷的增大,轴承同一列上的总径向力不断增大,偏载程度越来越严重。研究为延长轴承使用寿命、保证轧机安全稳定运行提供理论依据,具有重要工程意义。     

考虑紧固螺栓的三排滚柱式转盘轴承载荷分布计算

螺栓是转盘轴承的关键紧固件。为考察紧固螺栓工作参数对转盘轴承载荷分布的影响,提出了一种针对三排滚柱式转盘轴承的有限元等效建模方法。首先,基于三排滚柱式转盘轴承的结构特点和受力情况,建立考虑紧固螺栓的转盘轴承有限元模型,并从减少计算量和保证计算效率等方面考虑,采用非线性弹簧单元模拟滚子,通过有限元仿真快速获取了该转盘轴承的载荷分布。然后,设计并开展三排滚柱式转盘轴承静态加载试验,通过有限元仿真结果和试验结果的对比验证了所构建有限元模型的准确性。最后,基于构建的有限元模型,分析了螺栓预紧力和螺栓结合面处摩擦系数对三排滚柱式转盘轴承载荷分布的影响。仿真结果表明：螺栓预紧力对三排滚柱式转盘轴承载荷分布的影响显著,而螺栓结合面处摩擦系数的影响微弱,其中上排滚子承受的最大载荷随螺栓预紧力的增大而增大,下排滚子承受的最大载荷随预紧力的增大而减小;在轴向力和倾覆力矩的联合作用下,三排滚柱式转盘轴承下排滚子承受的载荷总体上高于上排滚子,充足的螺栓预紧力可以提高转盘轴承的承载能力,而螺栓预紧力不足则会使下排滚子承受更大的载荷,导致转盘轴承提前失效。研究结果可为转盘轴承的安装和后期维护提供参考。     

Structure Design and Optimization of Deep Cavity Rollers of Rotary Steering Spindle System

The center shaft of rotary steering spindle system is bendable under bias force. A severe partial load effect occurs among rollers, the inside and outside circles of the first cantilever bearing. Simulation analysis was conducted by loading boundary condition of the spindle under bias force. Furthermore, three different types of deep cavity rollers, which were cylindrical, conical, and spherical, respectively, were analyzed by finite element method. The effects of deep cavity angles, radius, and offset on mechanical properties of bearing were studied. The data obtained by simulation analysis were trained and predicted by Back Propagation (BP) neural network, and then the BP neural network model was incorporated into fmincon function. Thereby, structure optimization of rollers was established based on BP neural network model and fmincon function. The results show that structure of the conical deep cavity roller gets optimal mechanical performance. After being optimized, maximum stress of edge region and elliptical area decreases, respectively, by 22 and 17% than before, indicating that structure optimization method of the neural network and fmincon function can be used in optimization of deep cavity rollers. This method can quickly search for the optimal solution with sufficient engineering accuracy, ease of use, and adaptability.     

印刷包装设备常用深沟球轴承参数对性能的影响

目的为轴承设计和公差选用提供理论依据与指导,有效解决轴承精密公差的选用问题。方法以高速糊盒机中6300型号的深沟球轴承为具体分析实例,建立深沟球轴承的数学模型,分析轴承参数微量变化带来的影响及其变化规律,并通过软件进行仿真分析与验证。结果深沟球轴承的疲劳寿命、刚度与滚子数量、直径及其内外圈曲率半径有着密切联系,其中轴承疲劳寿命对滚子数量和滚子直径变化表现敏感,寿命的增加量达到77.78%,轴承径向刚度对轴承滚子数量的变化很敏感,刚度的增加量为23.08%,而轴承轴向刚度对滚子直径和套圈曲率半径的变化较为明显,刚度的增加量分别为38.29%和15.1%。结论在一定范围内应尽量选取和设计滚子数量较多、直径较大、内外圈曲率半径较小的深沟球轴承,使其疲劳寿命与刚度性能达到最优。     

印刷机偏心滚子轴承接触应力与变形仿真分析

目的对偏心轴承接触应力与滚子静、动态变形进行研究,得到接触应力与变形和结构与工况因素的关系。方法在Hertz线接触与弹流润滑理论下,建立滚子接触应力模型及静、动态滚子间接触变形的关系模型,利用有限元软件Ansys仿真计算。建立静、动(润滑与转速)态下滚子变形之间的关系公式,分析印刷机偏心双列圆柱滚子轴承的接触应力与变形及相互关系。结果滚子与内外套圈的接触应力均随径向载荷的增大而增大,滚子与内套圈的接触应力大于滚子与外套圈的接触应力;滚子的总接触变形量与径向载荷呈正比关系,滚子的内外接触应力与滚子的总接触变形量也呈正比关系;滚子的边缘出现应力集中,须用设计凸度的方法降低,从而更好地提高偏心轴承的整体性能。结论根据接触应力与变形的关系,可为偏心轴承的设计与优化提供理论依据。     

辊式涂布两辊间隙施涂过程的数值计算分析

目的系统地计算涂层厚度与两辊间隙、涂布辊速度以及胶黏剂的流体稠度和流动指数等影响因子的关系。方法在分析该复杂流动机理的基础上,利用CFD软件对具有非牛顿流体特性胶黏剂的两辊间隙施涂过程进行二维数值模拟。结果在五辊无溶剂涂布工程中,两辊间隙增大,最终涂布厚度也明显增大;增大涂布辊转速,涂布厚度也将减小;胶黏剂的流体稠度越大,最终传递到基材上的涂层厚度减小。结论两辊间隙的大小对涂层厚度的影响最大,胶黏剂的流体稠度、流动指数也对涂层厚度有较大的影响。     

圆柱滚子轴承多体接触动力学研究

考虑滚子和套圈、滚子和保持架、保持架和引导套圈的动态接触关系,提出了机械系统中圆柱滚子轴承多体动力学分析的新方法。基于圆柱套圈滚道的三角网格模型,实现了圆柱滚子和套圈滚道的动态接触力的预测搜索算法,进而建立了计及润滑摩擦作用和Hertz接触作用的圆柱滚子轴承的三维多体接触全动力学模型。运用广义-α方法计算分析了不同工况条件下圆柱滚子轴承的动态特性和保持架的稳定性,获得了不同工况下轴承的运动轨迹、角速度、滚子和倾斜扭转振动、动态接触力,拖动力和相轨迹等动态响应的变化规律。计算结果表明低速或较小径向力下,滚子和保持架的拖动力相对较小且不稳定,滚子和保持架侧梁、外圈挡边之间存在明显的频繁接触冲击作用,内圈中心的振动位移相对较大,保持架中心的径向平面运动轨迹形成不稳定的近似圆周运动,圆柱滚子轴承的运动稳定性相对较差。随着转速或旋转径向力的增加,保持架中心的径向平面运动轨迹为圆周运动和单周期的相轨迹运动,保持架中心的轴向振动明显,滚子倾斜扭转振动相对较小。     

Computational model for determination of dynamic load capacity of large three-row roller slewing bearings

In the presented paper a calculation procedure for determination of dynamic load capacity of large three-row roller slewing bearings is presented. The calculation procedure consists of three main parts: (i) determination of internal contact force distribution in a large three-row roller slewing bearing with consideration of bearing clearances and ring support deformations, (ii) determination of stress field in the contact area between raceway and rollers as a consequence of contact forces and (iii) determination of the bearing’s fatigue life due to contact fatigue of the raceway. The internal contact force distribution is determined numerically by using a symmetry 3D FEM-model of a large three-row roller slewing bearing. Another numerical procedure is used to determine the stress field in the contact area between rollers and raceway. This problem is studied on different roller types: cylindrical roller (without profile correction), fully crowned roller (logarithmic-profile) and partially crowned roller (ZB-profile). Numerically determined contact stresses then serve as a basis for fatigue analyses, where the bearing’s service life of the bearing is determined by using the stress-life approach, considering typical material parameters of the bearing’s raceway.     

基于有限元分析的瓦楞辊中凸曲线优化设计

目的研究瓦楞辊在复杂工作应力条件下的中凸度优化设计。方法通过理论力学的方法,建立相应的上、下瓦楞辊的中凸度数学模型,推导出中凸曲线方程。对优化后的瓦楞辊进行力的加载和几何约束等边界条件,建立有限元模型,并且使用Ansys软件进行模拟仿真,将优化前后的中凸值和6对啮合的瓦楞辊间隙值进行比较。结果优化后的上瓦楞辊中凸值比优化前最大降低了31.1%,下瓦楞辊中凸值比优化前最大降低了43.7%;6组啮合的瓦楞辊,优化后比优化前的中凸值间隙减小,说明优化后的6组瓦楞辊的自身受力情况较为均匀,生产出的瓦楞纸板质量更好,并且瓦楞辊之间的阻力减小,延长了瓦楞辊使用寿命。结论通过对瓦楞辊中凸曲线进行优化设计,将上瓦楞辊制成向下凹的形状,同时将下瓦楞辊制成向上凸的形状,根据有限元仿真的数据对比得出研究方法是合理可靠的。