基于套圈变形的柔性轴承弹流润滑分析

以柔性轴承为研究对象,基于赫兹接触理论和弹性薄壁圆环理论,建立柔性轴承等温椭圆点接触弹流润滑模型,对滚珠及内外圈滚道的接触区受载荷最大位置处进行弹流润滑数值分析;计算危险点的曲率半径、速度及载荷,分析载荷及速度变化对该位置润滑性能的影响。研究结果表明:套圈变形使得润滑接触区峰值压力增大、膜厚减小;柔性轴承弹流润滑油膜最小膜厚及中心膜厚均随载荷的增大而减小,油膜压力随载荷的增大而变大,表明载荷增大对柔性轴承的承载有一定影响;随转速的增大最小膜厚及中心膜厚均增大,表明在一定范围内,适当提高转速能够改善润滑性能。     

磁流体润滑机床主轴滑动轴承弹流润滑分析

建立磁流体润滑机床主轴滑动轴承的弹流润滑模型,并进行弹流润滑数值模拟分析.探讨载荷和速度对磁流体润滑膜压力和膜厚的影响.分析结果表明:在磁流体润滑条件下,当转速不变时,压力峰值随着载荷的增大而增大,入口区压力、膜厚及最小膜厚随载荷的增大而减小;当载荷不变时,压力随着速度的增加没有明显变化,膜厚及最小膜厚都随速度增大而增加.     

链条套筒与销轴铰链副冲击载荷-往复运动的弹流润滑数值模拟

数值模拟链传动中销轴与套筒之间的定载荷和变载荷弹流润滑接触问题,套筒相对于销轴做纯滑动往复运动。定载荷是假定往复运动过程中载荷恒定不变;变载荷是假定链节在啮入和啮出链轮过程中存在的冲击载荷按正弦函数规律变化。比较在定载荷和变载荷加载条件下线接触往复运动工况的弹性润滑油膜变化情况,分析在动载荷加载条件下不同行程长度对弹性流体动力润滑特性的影响。研究发现,动载荷对油膜的压力、膜厚影响较大:随着动载荷的增加,油膜中压力急剧增大,膜厚减小;但加载方式对摩擦因数的影响不大;在相同的加载方式下,随着行程长度的增加,油膜压力减小,中心膜厚和最小膜厚显著增加。     

具有中央凸起的点接触弹流润滑特性研究

建立具有中央凸起的点接触弹流润滑控制方程,并采用多重网格法及多重网格积分法进行数值求解;比较有凸起表面和光滑表面下的压力及膜厚曲线,讨论载荷及卷吸速度对压力分布及油膜形状的影响。结果表明：具有中央凸起时在接触中心附近,压力经历了急剧升高、骤然下降、再升高的一个波动过程;最小膜厚出现在接触中心,且接触中心前面产生了一个凹陷;增大卷吸速度或减小载荷都使得膜厚曲线整体升高,最小膜厚随着卷吸速度的增大而增大,载荷几乎不影响最小膜厚;载荷增大使得最大压力增大,但中心局部压力波动范围变化很小;增大卷吸速度使得最大压力和中心局部压力波动范围都减小。     

高速小型复合陶瓷球轴承的润滑特性研究

为了寻求一种能够快速建立高速小型复合陶瓷球轴承弹流润滑数学模型的数值计算方法,基于Reynolds方程的情况下运用Fortran语言在Visual Studio中进行编译,通过给定初始压力分布,运用迭代法求得弹流润滑完全数值解,并获取最终的压力和膜厚值。结果表明:转速、载荷以及润滑油粘度会对轴承的接触区压力、膜厚产生影响,其中随着转速的增加,最小膜厚增加,最大压力减小;随着载荷的增加,最小膜厚减小,最大压力增大;而随着润滑油粘度的增加,膜厚增加,最大压力减小。通过与传统理论计算结果的对比,结果具有较好的一致性,研究结果对高速深沟陶瓷球轴承运用具有指导意义。     

三角形周期脉冲载荷对轧辊轴承弹流润滑的影响

建立了三角形周期脉冲载荷作用下轧辊轴承弹流润滑数学模型,利用压力求解的多重网格法及弹性变形的多重网格积分法数值模拟了连续三角形周期脉冲载荷作用下乳化液润滑膜压力及膜厚的分布,分析了三角形周期脉冲载荷作用下润滑膜中心压力、中心膜厚及最小膜厚随时间变化的特性.计算结果表明,润滑膜中心压力的变化周期同脉冲周期一致,中心膜厚的变化滞后于脉冲和中心压力的变化;随三角形周期脉冲幅值的增大,中心压力和中心膜厚的振幅均增大,周期脉冲幅值越大,中心压力值越大,中心膜厚上下波动越大;当周期脉冲脉宽变大时,中心压力和中心膜厚的波动脉宽也变大,0.03 s后的中心膜厚上下波动范围变化微小.     

变速变载变曲率时变等温线接触弹流润滑分析

在弹性流体动力润滑中,有时会出现速度、载荷、曲率半径同时随时间变化的工况.针对这类问题,选取一种椭圆凸轮,利用多重网格技术对椭圆凸轮/平底推杆副的线接触弹流润滑问题进行了数值仿真,给出了一个周期中压力和油膜厚度的变化情况.同时分析和比较了在不同工况下,中心压力和最小膜厚随时间的变化.数值计算结果表明:尽管在一个周期内,大部分瞬时的最小膜厚和中心压力的计算值与准稳态结果比较接近;但是在两表面速度反向运动期间,膜厚的计算值与准稳态结果存在着较大差异,说明挤压效应不可忽略.     

水润滑塑料合金轴承的弹流润滑分析

建立水润滑塑料合金轴承的数学模型,对水润滑条件下塑料合金轴承的弹流润滑问题进行数值模拟,讨论转速和载荷对水润滑膜压力和膜厚的影响。结果表明:在水润滑条件下,转速对水润滑膜的压力影响不明显,而膜厚及最小膜厚随转速的增大而明显增大;随载荷的增大,压力峰值有明显增大,而在入口区压力随载荷增大而减小,膜厚及最小膜厚随载荷增大而减小。     

乳化液润滑复合塑料轴承的弹流润滑分析

利用考虑惯性力的Reynolds方程,对乳化液润滑条件下复合塑料轴承的弹流润滑问题进行了数值模拟,讨论了载荷、转速和轴承轴径大小对乳化液膜压力和膜厚的影响.结果表明:在乳化液润滑条件下,惯性力对乳化液膜压力的影响很小,而对乳化液膜厚度的影响较大;随着载荷的增大,压力峰值有明显增大,而在入口区压力随载荷增大而减小,膜厚以及最小膜厚随载荷减小而明显增大;转速和轴承轴径大小对乳化液膜压力的影响不明显,而膜厚以及最小膜厚随转速增大而明显增大,随轴承轴径的增大而减小.     

指数率流体热弹流润滑分析

应用多重网格技术,求得了指数率非牛顿流体线接触热弹流润滑的数值解,分析了油膜压力、厚度和温度等随流变指数、速度参数、滑滚比及载荷参数的变化关系,并与相同工况下的等温解进行了比较。结果表明,随着流变指数的增加,油膜厚度和温度、入口处的当量粘度、最小膜厚、中心膜厚和最大温升均增大,而油膜压力和摩擦因数的变化较小。指数率流体弹流润滑问题的热效应不可忽略;与压缩功项相比,油膜能量方程中的热耗散项对温度的影响最大。同时,无量纲速度参数、滑滚比和载荷参数等均影响热弹流润滑特性。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

RLS and LMS blind adaptive multi-user detection method and comparison in acoustic communication

RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...