纱线高速运动时张力的精确计算

对纱线在零件表面上高速运动时的力学问题进行了研究，得出了准确计算纱线张力的理论公式，并与传统的欧拉张力公式作了比较分析     

板带轧制工艺控制理论概要

以最小阻力定律、体积不变条件和秒流量相等条件为内容的经典轧制理论,经试验、演绎形成了较完整的轧制应用技术科学体系,这种体系所反映的是静态规律。在轧制理论发展中引入控制论、信息论、计算机科学等高新技术,对轧制过程进行控制。在轧制理论发展史上,弹跳方程建立之前是以力学为基础建立的经典轧制理论,之后为以力学和控制论为基础建立的基本轧制工艺控制理论。文章提出工艺控制理论概念,是在基本轧制工艺控制理论的基础上建立的新的理论体系,主要内容包括：在连轧张力理论中反映了张力的负反馈,建立了连轧张力理论体系;在厚控过程中,     

混凝土初始损伤对爆炸压碎区尺寸影响分析

在已有经验公式的分析基础上,考虑钻孔或侵彻对炮孔产生损伤的影响,引入一个无量纲的参数,提出预估混凝土介质中爆炸压碎区半径的经验公式,通过文献实验对经验公式参数进行拟合,并由文献提供的全尺寸实验对提出的公式进行验证。分析比较表明,本文提出的公式预估与实验符合较好。     

混凝土初始损伤对爆炸压碎区尺寸影响分析

在已有经验公式的分析基础上,考虑钻孔或侵彻对炮孔产生损伤的影响,引入一个无量纲的参数,提出预估混凝土介质中爆炸压碎区半径的经验公式,通过文献实验对经验公式参数进行拟合,并由文献提供的全尺寸实验对提出的公式进行验证。分析比较表明,本文提出的公式预估与实验符合较好。     

冷轧卷取机张力恒定的研究

本文利用某钢厂的实际生产数据,建立了计算出口带钢卷取张力的数学模型,对卷取张力恒定的影响因素进行了研究。通过公式推导和计算,得NT各影响因素和张力之间的相互关系式,为以后张力恒定的深入研究和通过最末架机架的张力控制来控制板型提供了理论基础。     

非标准人体静电模型实验数据的理论转换

目的　静电敏感度数据的处理 .方法　从旺希贝尔模型出发 ,利用理论推导 ,处理非标准人体静电模型的实验数据 .结果　得到 RC放电模型之间的转换公式 .结论　便于不同静电敏感度数据的比较分类     

IEEE STD 1309-2013电场校准标准的公式与计算讨论

理论推导表明,目前采用的电场计量标准IEEE STD 1309-2013给出的TEM小室场强计算公式值得商榷,同时推导了修正公式。实验表明:修正公式和原公式计算结果在实验条件下差别微小,在目前的验证条件下难于分辨这种差别。进一步改善实验验证,有两个可能的技术方向。     

再议牛顿第二定律的验证性实验

高中教材中学生实验"验证牛顿第二定律"都是选用砂桶小车研究物体加速度与力、加速度与质量之间的关系.这个实验有一个要求,即m<相似文献   

覆冰导线舞动的动态张力研究

导线舞动严重威胁输电线路安全稳定运行,确定舞动引起的动态张力是研究舞动问题的重要内容之一。首先从能量平衡和导线长度变化的角度,推导动态张力的理论公式。然后建立导线舞动张力变化数值模拟模型。以实际高压输电线路为例,将理论结果与数值计算进行比较,判断理论公式是否有效及其适用范围。分析理论和数值结果,得到舞动幅值、阶数、档距、高差角等参数对动态张力的影响规律。对导线舞动分析有参考价值     

印刷机张力控制系统的建模与仿真

卷筒纸印刷中影响印刷速度和印品质量的主要因素是纸带的张力,因此,要提高卷筒纸印刷质量,必须精确控制纸带张力,国外的卷筒纸印刷机全面控制系统发展较快,但国产印刷机张力控制的研究与国外相比有很大差距.针对这一问题,研究了一套较完整的适用于各种印刷方式的张力控制理论和方法,对印刷机张力控制系统进行了建模与仿真实验.实验表明,设计的控制结构具有良好的可靠性能,对提高国产卷筒纸印刷机张力控制系统的精度具有重要意义.     

Computational Intelligence-Based Process Optimization for Tandem Cold Rolling

The requirements for the manufacturers of steel have been increased in many respects in recent years. Harsh competition among manufacturers demands a continuous reduction of production costs and improvement of product quality. The work presented herein describes maximizing rolling mill throughput and minimizing processing costs and crop losses by computational intelligence-based process modeling and optimization. In this article, an intelligent searching mechanism is introduced to optimize the rolling schedule by assessing rolling constraints and the combined cost function of tension, shape, and power distribution. The optimization results have been compared with current rolling practices based on empirical models. It is shown that the proposed model can significantly reduce the power distribution cost, maximize the safe level of strip tension, and obtain good strip shape. The proposed model is generic for complex engineering problem optimization, and is capable of multiple-objective problem solving.     

带张力轧制H型件边端的力能参数的实验研究及理论计算

本文通过实验研究了在连轧条件下轧制H型件边端的轧制力和力矩及张力对它们的影响,确定丁轧边端时的应力函数和力臂系数的变化规律。用刚塑性有限元法对轧H型件边端的力能参数进行了理论计算,计算结果与实验结果符合较好。本文的研究结果可推广于H型钢生产的工程计算。     

FFS重膜印刷机收卷部双锥度张力控制方法

目的解决FFS重包装膜在高速印刷过程中带卷过大所引起的卷膜中心处皱折和端面不齐等产品质量问题。方法提出一种双锥度张力控制方法,通过对收卷张力和辊筒压力分别采用锥度张力控制来有效控制卷膜内部张力的分布,令卷膜内部张力分布更加均匀。基于等效张力的概念,对卷膜中的单元体进行受力分析,得到卷膜受力和卷膜自身张力的变化规律。建立卷膜张力的数学模型,对双锥度控制方法的性能进行理论分析。结果通过集成到设计的平台上,对所提出方法的有效性进行验证,实验结果表明该方法使收卷张力更加稳定,可减少卷膜内层抓心变形,产品合格率提高至98%以上。结论实验结果验证了所提出方法和研制装置的有效性,可有效解决产品出现的质量问题。     

Effect of Processing Parameters on Edge Cracking in Cold Rolling

Experimental and numerical investigations have been carried out to study the effect of processing parameters on edge cracks in cold rolling process of silicon steels. The onset of edge cracks has been simulated by using finite element method (FEM) based on the Gurson–Tvergaard–Needleman damage model. Factorial design and Taguchi experimental design methods have been proposed to analyze the effects of reduction ratio, tension, work roll diameter, and friction coefficient on the formation of edge cracks. Parametric studies indicated that with the increasing of reduction ratio, friction coefficient, and tension, the crack length increases. A bigger work roll is beneficial to restrict the edge crack growth as well. The rank according to the impact degrees on the crack initiation from high to low is reduction ratio, tension, work roll diameter, and friction coefficient. Meanwhile, the combined effect curve of reduction ratio and tension on crack length was obtained which was validated by the experimental results as well.     

Surface tension of binary and ternary aluminium alloys of the systems Al-Si-Mg and Al-Zn-Mg

The surface tension and density of liquid binary and ternary aluminium alloys of the systems Al-Si-Mg and Al-Zn-Mg (Si, Mg and Zn contents less than 19, 8 and 20 wt %, respectively) have been measured by means of the maximum bubble pressure method. A semi-empirical theory, which relates the surface tension to bulk thermodynamic properties, is used to calculate the surface tension of the binary alloys and discuss the experimental data. For the ternary alloys, the present results indicate that in the range of compositions explored here, the properties of the ternaries can be obtained from those of the binaries. Comparison with results previously reported by other authors is made.     

A Generalized Yield Criterion

A generalized yield criterion is proposed based on the metai plastic deformation mechanics and the fundamental formula in theory of plasticity. Using the generalized yield criterion, the reason is explained that Mises yield criterion and Tresca yield criterion do not completely match with experimental data. It has been shown that the yield criteria of ductile metals depend not only on the quadratic invariant of the deviatoric stress tensor J2, but also on the cubic invariant of the deviatoric stress tensor J3 and the ratio of the yield stress in pure shear to the yield stress in uniaxial tension κ/σs. The reason that Mises yield criterion and Tresca yield criterion are not in good agreement with the experimental data is that the effect of J3 and κ/σs is neglected.     

MONODISPERSE DROPLET GENERATION BY SPONTANEOUS CONDENSATION OF STEAM FLOW IN NOZZLES

ABSTRACT

Spontaneous Condensation (also called homogeneous Condensation)of steam flow in one dimensional nozzle has been numerically modeled. The classical (Frenkel and Volmer) and Deich's nucleation theories were used. Unlike the classical theory, Deich's theory also accounts for the critical droplet size dependence upon the expansion rate in the nozzle. Pressure ratio, mean droplet size and droplet size distributions were obtained along the axial length for various nozzles. Comparisons with experimental data were made. The agreement between the numerical results and the experimental data was good. Both theories predicted the pressure ratio properly but the classical theory tended to underestimate the droplet sizes. Deich's theory is preferred for analyzing and designing new nozzles. The classical theory cannot be used for obtaining a correlation for surface tension ratio, thereby limiting its usage for new nozzles. Effects of Inlet conditions and nozzle expansion rates on mean droplet size and droplet size distributions were examined. The spontaneous condensation process results in relatively monodisperse droplets. The numerical model and the results are discussed in this paper.     

基于动态贝叶斯网络与DS证据理论的轧机颤振监测方法

提出了基于动态贝叶斯网络和DS(Dempster/Shafer)证据理论的轧机颤振实时监测方法,该方法预选多个时域和频域的特征参数表征轧机不同工况下振动信号的不同特征,利用稳定判别率方法筛选敏感度高的特征参数;使用动态贝叶斯网络与DS证据理论实时监测模型建立轧机颤振状态实时监测系统,构建连续的速度载荷时间片,将3个连续的速度载荷时间片作为DS证据理论的证据体,给出了优化基本概率分配的信任度方法,解决了DS证据理论的证据体间冲突问题;最后在轧机实验平台进行实验,诊断结果表明：该方法对轧机颤振不同状态的识别率达到99.05%。     

A comparison of nucleation theories by the asymptotic solution of condensing nozzle flows

Summary The classical and Dillmann-Meier nucleation rates are compared in transonic nozzle flows of moist air under atmospheric supply conditions using the asymptotic solution of Delale, Schnerr and Zierep. The comparison is made in slender nozzles using two distinct expressions for the poorly known surface tension, one fitted to the experiments of Peters and Paikert by the classical theory and the other extrapolated from room temperatures to the range of temperatures investigated. The droplet growth law is fixed by the Hertz-Knudsen formula. It is shown that the Dillmann-Meier theory predicts higher nucleation rates than the classical theory together with a delay of the onset of condensation when either of the surface tension expressions is employed.