液黏调速离合器摩擦副热-结构耦合分析

根据热传导理论,结合热流密度,考虑摩擦片上沟槽的对流换热作用,建立了液黏调速离合器摩擦副的理论模型。根据离合器实际工况,对摩擦副边界摩擦阶段进行数值分析,研究摩擦副不同材料组合下的温度与变形差异。研究结果表明,摩擦副温度场被沟槽分成了不同温度梯度的椭圆块,高温集中在靠近外径处;相同工况下,对偶片材料为30Cr Mn Si A时温度和变形量最大。摩擦副内外径发生了沿z轴正向和负向位移,整个摩擦副产生碟形翘曲现象。在对偶片外径约束情况下,仅30Cr Mn Si A未发生塑性变形。这对液黏传动机理和摩擦副主动设计具有指导意义。     

液粘传动界面间油膜态数值模拟研究

为了研究在软启动过程中,液粘调速离合器摩擦副间隙内油膜形态的演变机理,基于计算流体动力学理论,建立流体油膜的计算模型,并考虑油膜的粘温特性,采用Fluent软件对摩擦副间隙内的油膜流场进行求解,获得了油膜的多物理场分布。研究结果表明：界面间油膜的最大温升从油膜出口位置转移至油膜入口位置附近;油膜在中间位置及出口位置的温度和径向速度呈现出抛物线状分布;影响摩擦副间隙内油膜最大动压的主要因素是油膜厚度与主、被动片相对转速;油膜的粘性扭矩输出呈现先增加后减小的趋势,粘性扭矩峰值出现在启动初期。     

液黏传动可控启动过程混合摩擦转矩特性研究

为了研究矿用重型刮板输送机可控启动装置中液黏传动可控启动过程混合摩擦阶段的转矩特性，基于雷诺方程建立了油膜承载力和剪切转矩数学模型，并根据G-W模型建立了微凸峰接触转矩模型，最终以刮板输送机实现S形曲线，得到了可控启动过程中摩擦副的承载特性和转矩特性。结果表明，可控启动过程中，摩擦副间油膜厚度按反S曲线随时间增大而减小；摩擦副的承载力和转矩不断增大，其中微凸峰为总承载力和转矩的主要承担部分，并且不断增大，而油膜承载力和转矩则只占据小部分并不断减小。研究结果为可控启动装置可控启动过程转矩特性预测和控制部分设计提供了理论依据。     

液黏传动摩擦副流固耦合传热分析

为探求液黏传动在充满工作油的流体阶段摩擦副温度分布情况,建立薄盘结构摩擦副热流固耦合模型,采用计算机流体仿真软件FLUENT对径向槽摩擦副进行数值模拟,得到摩擦副的温度云图。通过搭建液黏传动装置试验台,测得径向油槽摩擦副间油膜温度分布数据。结果表明:在径向方向上,随半径的增加,摩擦副温度逐渐增加且沟槽处温度低于无沟槽处;在圆周方向上,相同半径处摩擦副的沟槽区比无沟槽区温度高,表明沟槽可以有效地降低工作油的升温;在纯油膜阶段摩擦片升温明显高于对偶片升温。有限元分析和实验研究结果趋势基本一致,验证了理论分析的可靠性。     

超精密摩擦传动机构

针对超精密传动机构定位精度高、行程大、运行平稳、激励振动小、系统可靠性高的要求,设计了一种双圆弧型驱动轮摩擦副的超精密摩擦传动机构,与圆柱型驱动轮摩擦副、双V型驱动轮摩擦副的结构相比,减小了接触应力,提高了接触刚度。应用赫兹接触理论对摩擦副的接触区域中最大接触应力以及接触变形量进行分析。实验表明该摩擦传动机构在300 mm全行程范围内,定位精度±10 nm。     

液黏传动软启动过程摩擦副应力场瞬态特性研究

为了研究液黏传动摩擦副软启动过程应力场的分布特性,利用Abaqus软件建立三维摩擦副热弹性分析模型,采用间接耦合数值分析方法来预测应力场的瞬态特性,并对参数敏感性进行了分析。结果表明,软启动过程中对偶钢片热应力逐渐增大,在启动结束时达到最大值,且最大值位置逐渐向中心区域靠近;油槽具有良好的冷却效果,摩擦衬片热应力最大值出现在每个菱形区域的边缘;弹性模量和热膨胀系数有正影响,而厚度和泊松比有负影响;改变参数值对热应力最大值出现的位置无影响。分析结果为摩擦副结构参数和材料参数的选择提供了参考依据。     

液黏传动摩擦副软启动过程承载特性研究

以刮板输送机可控启动装置液黏传动软启动过程为研究对象,考虑摩擦副表面粗糙度及工作油的离心力,基于平均流量模型求解了油膜厚度及油膜压力的变化规律。基于Greenwood-Tripp接触模型建立了摩擦副粗糙接触压力和转矩方程,利用转矩平衡原理对软启动过程中摩擦副承载特性的时变性进行了分析。结果表明：当启动时间10 s,额定输出转速45 r/min,启动过程遵循S形曲线变化时,油膜厚度按照反S形曲线逐渐减小,并趋于恒定值;油膜压力随时间先增大后减小,且沿径向的分布与启动时间密切相关;摩擦副间压力按照S形曲线增大;负载越大,启动时油膜越薄,摩擦副间压力越大。研究结果为准确地分析摩擦副热特性提供了先决条件,同时也为控制策略的制定奠定了理论基础。     

锁止离合器液粘传动机理分析

液粘传动是利用主动和从动摩擦片间的油膜剪切力来传递运动和转矩,实现无级变速和同步运行的一种新型传动装置.本文运用流体动力润滑理论,对锁止离合器液粘油膜传动机理进行了理论分析,建立了带径向油槽摩擦片间油膜传动的数字模型,得到了油槽数目、深度、宽度对液粘传动性能的影响;并考虑油液离心力对传动性能的影响;获得了锁止离合器油膜温度场的分布.     

新型高效钢背/自润滑复合材料衬层结构传动螺母

为克服传统传动滑动螺旋副摩擦因数大、效率低的缺点,提出一种带衬层螺母的创新方案:螺母以钢为基体,衬层为碳纤维织物增强聚合物自润滑复合材料,兼有高的承载能力和低的摩擦因数。研究自润滑复合材料的配方、制备工艺、减摩机理和摩擦学性能。衬层表面的织构形成微润滑池,固-液协同润滑改善了重载下的润滑效果;衬层采用成形加工并在表面形成润滑油道,进一步改善了润滑条件。开发了新型螺旋副的制备工艺并研制了630 kN压力机实用螺母,测试表明,新型螺母较ZCuSn10Pb1青铜螺母的工作性能有较大提高,重载条件下复合材料螺母摩擦因数降低了21.2%,而传动效率提高了10.6%。新型螺旋副的开发,不仅解决了伺服压力机的发展的一个瓶颈问题,而且对于所有采用螺旋传动的机械装备都具有重要的意义。     

液粘传动系列装置的研究

介绍了液粘传动技术的国内外发展应用情况,对液粘传动系列装置的工作内容及技术关键进行了具体阐述,提出了技术实施方案,设计了流程图并指出目前该领域的发展前景.     

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...     

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...     

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。     

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。     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

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.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...