Study of the thermal influence on the dynamic characteristics of the motorized spindle system

The severe internal heat generation of the motorized spindle system causes uneven temperature distribution, and will affect the vibration characteristics of the system. Based on the thermal analysis about the motorized spindle by finite element method (FEM), the thermal deformations of the spindle system are calculated by the thermal structure coupling simulation, and the thermal deformations of the rotor and the bearing units are extracted to analyze the bearing stiffness changes so that the modal characteristics of the rotor can be simulated in different thermal state conditions. And then the rotor thermal deformation experiment and the modal experiment of spindle by exciting with hammer are performed. The result shows that the thermal state of the motorized spindle system has a significant influence on the natural frequency of the rotor, which can be carefully treated when a spindle system is designed.     

电主轴冷却系统设计与仿真优化

为解决电主轴因内部温度场复杂而造成冷却效果差的问题,设计了一种用于电主轴冷却的水冷机系统。根据电主轴热特性分析结果,提出了水冷机冷却方案,计算了相关的传热参数,并建立了电主轴温度-流速控制模型。然后,利用ANSYS Fluent软件对电主轴进行了流体冷却有限元仿真,并通过电主轴冷却实验对仿真结果进行了验证。通过对比仿真结果和实验结果可知,冷却后电主轴电机定子最高温度约下降了60%,转轴的形变量约降低了70%。结果表明：利用水冷机系统对电主轴进行冷却具有良好的冷却效果,这可为高精密机床主动热控制技术的研究提供一定的借鉴和参考。     

Neural model for forecasting temperature in a distribution network of cooling water supplied to systems producing petroleum products

This article presents the application of a neural model of heat transfer for the purpose of forecasting temperature at selected points of a circulating water ring network. The purpose of a circulating water system is to lower the temperature of petroleum products manufactured on numerous petrochemical lines at a Polish petrochemical plant. Temperature forecasting at 96 nodes of the circulating water system, significant from the point of view of system operation, is carried out using SVM neural networks. Neural networks learn based on archival data recorded in the process parameter monitoring system. Thermal, hydraulic and control parameters of the cooling process, as well as weather variables, constitute crucial input data for the neural model. The temperature forecasting algorithm has been implemented in a computer program that was then applied and remains in use for temperature forecasting in a maintenance department of an industrial plant.     

Experimental study on the double-evaporator thermosiphon for cooling HTS (high temperature superconductor) system

A cryogenic thermosiphons is an efficient heat transfer device between a cryocooler and a thermal load that is to be cooled. This paper presents an idea of thermosiphon which contains two vertically-separated evaporators. This unique configuration of the thermosiphon is suitable for the purpose of cooling simultaneously two superconducting bearings of the HTS (high temperature superconducting) flywheel system at the same temperature. A so-called double-evaporator thermosiphon was designed, fabricated and tested using nitrogen as the working fluid under sub-atmospheric pressure condition. The interior thermal condition of the double-evaporator thermosiphon was examined in detail during its cool-down process according to the internal thermal states. The double-evaporator thermosiphon has operated successfully at steady-state operation under sub-atmospheric pressure. At the heat flow of 10.6 W, the total temperature difference of the thermosiphon was only 1.59 K and the temperature difference between the evaporators was 0.64 K. The temperature difference of two evaporators is attributed to the conductive thermal resistance of the adiabatic section between the evaporators. The method to reduce this temperature difference has been investigated and presented in this paper. The proper area selection of condenser, evaporator 1, and evaporator 2 was studied by using thermal resistance model to optimize the performance of a thermosiphon. The superior heat transfer characteristic of the double-evaporator thermosiphon without involving any cryogenic pump can be a great potential advantage for cooling HTS bulk modules that are separated vertically.     

高速静压内置式电主轴系统稳定性分析及优化

针对高效精密机床电主轴系统的高速化,讨论液体静压主轴系统失稳机理,并对高速静压内置式电主轴系统进行稳定性分析;提出基于遗传算法的电主轴系统稳定性优化方法。以系统稳定性评价指标为优化目标、电主轴系统轴向尺寸参数为设计变量,采用高效微型遗传算法实现电主轴系统稳定性优化。该方法既能高效解决增强轴系稳定性优化问题,又可避免复杂结构参数修改;通过某高速磨床静压内置式电主轴系统稳定性分析及优化对该方法进行验证。结果表明,稳定性分析及优化后系统稳定性得到明显提高。     

基于热阻网络模型的硅基微槽热沉多目标优化设计

微槽热沉具有传热效率高、可靠性强的优点,可用于对微尺度高热流密度电子元件进行冷却。为满足其性能需求和控制成本,在对微槽热沉进行设计时需要对其传热能力和流动阻力同时进行优化。传统研究采用的热阻网络模型较为简单,不能很好地反映热阻和流动阻力对微槽道截面形状拓扑变化的响应,且其优化对象通常为既定截面的形状尺寸。为此提出一种基于离散化方法的单层硅基微槽热沉热阻网络模型,将热沉鳍片细分为厚度较小的微元,根据微元热阻对微元宽度的响应及微元热阻对整体热阻的贡献来描述微槽道的整体热阻。以微泵输出功率为优化边界条件,压降和热阻为优化目标,通过SQP（sequential quadratic programming,序列二次规划）方法对层流状态下四边形等截面硅基微槽热沉进行尺寸优化,利用CFD（computational fluid dynamics,计算流体动力学）对优化结果进行模拟和验证。结果表明,当鳍片高度较低时,鳍片截面形状为矩形,随着鳍高增加,截面形状有向三角形发展的趋势。在设计区间内,微槽道截面为梯形、鳍片截面为三角形时传热效率与压降相对占优。用边界点法和理想点法优化模型求得微槽道高度、鳍底宽、槽底宽、槽顶宽的优化结果分别为500,50,64.5,114.5 μm和500,50,50,100 μm。该方法能根据设计需求调整评价函数,同时计算结果具有重要工程意义,为微槽热沉设计人员提供参考。     

Modelling of a thermal insulation system based on the coldest temperature conditions by using artificial neural networks to determine performance of building for wall types in Turkey

In formation of building external envelope, as two important criteria, climatic data and wall types must be taken into consideration. In the selection of wall type, the thickness of thermal insulation layer (d_i) must be calculated. As a new approach, this study proposes determining the thermal insulation layer by using artificial neural network (ANN) technique. In this technique five different wall types in four different climatic regions in Turkey have been selected. The ANN was trained and tested by using MATLAB toolbox on a personal computer. As ANN input parameters, U_w, T_e,Met, T_e,TSE, R_wt, and q_TSE were used, while d_i was the output parameter. It was found that the maximum mean absolute percentage error (MRE, %) is less than 7.658%. R² (%) for the training data were found ranging about from 99.68 to 99.98 and R² for the testing data varied between 97.55 and 99.96. These results show that ANN model can be used as a reliable modeling method of d_i studies.     

Kapitza resistance and thermal conductivity of Mylar at superfluid helium temperature

The Kapitza resistance and the thermal conductivity of type A Mylar sheets in the temperature range between 1.4 and 2.1 K have been determined. Four sheets with varying thickness from 37 μm to 255 μm, have been tested in steady-state condition. For a small temperature difference (10-30 mK) and heat flux density smaller than 30 Wm⁻², the total thermal resistance of the sheet is determined as a function of sheet thickness and bath temperature. The Kapitza resistance is given by R_K = (1.28 ± 0.08)T⁻³ × 10⁻³ Km² W⁻¹, and the thermal conductivity, κ = [(8.83 ± 0.75) + (11.73 ± 0.43) × T] × 10⁻³ Wm⁻¹ K⁻¹.     

考虑扣件温频变的车轨桥垂向耦合系统振动能量研究

通过对扣件进行定频变温试验,结合温频等效原理与高阶分数导数FVMP模型建立扣件的温频变动态力学模型,并在车-轨-桥耦合系统中采用新建模型模拟扣件,基于功率流法系统地分析与评价扣件温频变动态力学性能对车轨桥耦合系统振动能量分布与传递的影响.结果 表明:考虑扣件动参数频变会使中高频段内的轨道结构振动能量增大,对低频段的轨道...     

基于昆虫翅脉仿生流道的数控机床主轴系统冷却结构热设计

主轴系统的热误差是影响数控机床加工精度的主要因素。根据自然界昆虫的翅脉结构,设计了一种基于鳞翅目昆虫翅脉仿生流道的新型主轴系统冷却结构。建立了昆虫翅脉仿生流道冷却结构模型,在数值传热学相关理论基础上,通过Fluent有限元软件对传统螺旋形流道和新型昆虫翅脉仿生流道冷却结构进行流固耦合仿真对比分析,结果显示后者比前者具有更好的散热效果和流动特性：在相同边界条件下,冷却液最大流速约为1.839 m/s,出入口压降为3 181 Pa,加热面最高温度降低了约17.8%、最低温度降低了约4.6%,且冷却结构的温度场分布更均匀。研究结果可为数控机床主轴系统冷却结构的热设计提供参考。     

Impact of the non-homogenous temperature distribution and the coatings process modeling on the thermal barrier coatings system

The present study deals with a numerical investigation of the residual stresses arising during the plasma-sprayed coatings process and their effects on the final stress state of the thermal barrier coatings system (TBCs) during service. A new thermo-mechanical finite element model (FEM) has been designed to function using a non-homogenous temperature distribution. Several phenomena are taken into account in the model such as: residual stresses generated during the spraying of coatings, morphology of the top-coat/bond-coat interface, oxidation at the top-coat/bond-coat interface, thermal mismatch of the material components, plastic deformation of the bond-coat and creep of all layers during thermal cycling. These phenomena induce local stresses in the TBCs that are responsible of micro-crack propagation during cooling and thermal cycling, specifically near the ceramic/metal interface.     

基于LabVIEW的介电材料电阻温度特性测控系统

介绍了在LabVIEW环境下开发测试程序VI（虚拟仪器）测试片状元件试样的方阻、电阻率以及电阻温度系数TCR随温度的变化关系，主要包括电阻温度特性测控系统的硬件构成，基于IabVIEW开发平台的测控软件框图及测试程序。该测试系统在-20℃～120℃温度范围内能够实现对元件试样的多点测试，升温方法采取线性升温，且升温速率可在0．1℃／min～10℃／min之间选择，测试结果对于介电材料性能的研究以及元器件开发都有一定的价值。     

模糊支撑半径变量贝叶斯网络多态系统故障概率分析

针对现有隶属函数描述系统及部件故障状态的不足,构建了一种含模糊支撑半径变量的隶属函数来描述部件故障状态,提出了一种基于模糊支撑半径变量的贝叶斯网络多态系统故障概率计算方法。在隶属函数的构造中,用变量代替精确值描述隶属函数模糊支撑半径,建立了含模糊支撑半径变量的隶属函数;并将其引入贝叶斯网络,利用桶消元法对多态系统叶节点故障概率进行分析,得到叶节点故障概率变化曲线。将所提出的方法与文献中基于模糊支撑半径为定值的隶属函数贝叶斯网络方法相比较,验证了方法的有效性。最后,将该方法应用到数控机床主轴系统故障分析实例中,对叶节点故障概率进行计算。结果表明,该方法能够有效解决多态系统故障状态隶属函数选择中的主观性问题。     

神经网络模型在预测Ni-Al系热爆点火时间中的应用

基于人工神经网络的原理,对热爆法制备Ni-Al系金属间化合物中的控制参数进行了研究,选取了加热速率、颗粒尺寸、压坯密度三个参数,通过对此参数的调控可以影响热爆反应的点火时间及反应过程.本文采用BP算法来训练网络,对热爆反应中的过程参数与热爆点火时间的映射关系进行了函数逼近,建立了热爆点火时间的神经网络模型.根据该模型可以预测热爆的点火时间,为控制热爆反应加压过程提供了可靠的依据.     

基于BP神经网络模型的Ni-SiC纳米镀层耐磨性能预测研究

采用神经网络技术,构建结构为3×8×1型的BP神经网络模型,并利用该模型对超声电沉积Ni-SiC纳米镀层的耐磨性能进行预测。通过磨损试验测试并研究Ni-SiC纳米镀层的耐磨性能,利用扫描电镜(SEM)、原子力显微镜(AFM)和X射线衍射(XRD)观察不同参数下Ni-SiC纳米镀层的组织结构及成分。结果表明,在BP神经网络模型的隐含层数和神经元数分别为1和8时,该BP神经网络模型的均方根误差最小,其最小值为1.24%。该BP神经网络模型的预测值与实验值相差不大,其最大误差为1.51%。当采用SiC粒子浓度8 g/L、电流密度2 A/dm^2、温度40℃时,SiC粒子均匀分布于Ni-SiC纳米镀层中,且镀层镍晶粒显著细化,其镍晶粒的衍射峰变宽、变矮。     

Theoretical model of the operation parameters regulated by the MIMO and SISO system in a cooling chamber

Smart buildings technologies are more and more common in the refrigeration industry. From definition, smart buildings are the integrated monitoring and controlling systems that govern processes inside the rooms and react immediately on every change inside and outside of the building to minimize exploitation costs and maintain functionality. Smart rooms are functional while ensuring suitable conditions (accurate temperature, humidity and air velocity) for food or medicines temporary storage.The temperature, humidity level and an air velocity are regulated in such a way, to improve quality of food and reduce exploitations costs. Modern methods and technologies enable engineers to design and build up an installation of a cold room with integrated subsystems working accordingly to the data gathered by the sensors to maintain specified functions.The article presents:

• •A transient model of the cooling chamber.
• •Transient parameters of cooling processes in MIMO and SISO control.
• •A refrigeration control system design.

     

Constraint-based network model of pathogen–immune system interactions

Pathogenic bacteria such as Bordetella bronchiseptica modulate host immune responses to enable their establishment and persistence; however, the immune response is generally successful in clearing these bacteria. Here, we model the dynamic outcome of the interplay between host immune components and B. bronchiseptica virulence factors. The model extends our previously published interaction network of B. bronchiseptica and includes the existing experimental information on the relative timing of IL10 and IFNγ activation in the form of qualitative inequalities. The current model improves the previous one in two directions: (i) by augmenting the network with new nodes with specific function in T helper cell differentiation and effector mechanisms and (ii) by using a dynamic approach that allows us to quantify node states and mechanisms revealed to be important from our previous model. The model makes predictions about the time scales of each process, the activity thresholds of each node and novel regulatory interactions. For example, the model predicts that the activity threshold of IL4 is higher than that of IL12 and that pro-inflammatory cytokines regulate the activity of Th2 cells. Some of these predictions are supported by the literature, and many can serve as targets of future experiments.     

考虑转动的双曲正切与正切组合模型缓冲系统冲击响应研究

针对普遍使用的缓冲材料受压时应力-应变曲线呈现的线弹性区、屈服区和压实区三段式形态,建立了双曲正切与正切组合模型.在此基础上,考虑包装产品冲击时由偏心导致的受力不平衡引起的转动,推导了具有转动和平动耦合的缓冲包装系统在半正弦加速度脉冲激励下的动力学方程,探讨了包装系统平动与转动相耦合的规律.数值算例的结果表明,未考虑转动效应,会导致一定程度的过度包装,造成浪费.该模型的建立和考虑平动与转动相耦合情况的动力学方程,更加接近实际缓冲包装的工程应用情况,为包装结构优化设计提供了参考.     

Ti-22Al-24Nb-0.5Y合金流变行为及BP神经网络高温本构模型

利用Gleeble-3500热模拟试验机进行等温恒应变热压缩实验,以实验获得的数据为基础,研究Ti-22Al-24Nb-0.5Y合金流变行为,通过正交实验对影响合金的流变应力因素进行分析,并建立基于BP神经网络的合金高温本构关系模型。结果表明:影响合金流变应力的主要因素依次为应变速率、变形温度和应变量;Ti-22Al-24Nb-0.5Y合金在热变形时的流变应力对应变速率和变形温度都较为敏感。当变形温度较低,应变速率较高时,合金变形呈流变软化特征,当变形温度较高,应变速率较低时,合金变形趋向于稳态流动;利用BP神经网络建立的合金高温本构关系模型,具有较高的精度,其相关性系数达到0.9949,平均相对误差在3.23%,预测值偏差在10%以内的数据点达98.79%,该预测模型可作为Ti2AlNb基合金塑性成形过程有限元模拟的本构关系。