针对CE认证的起重机结构强度计算方法研究

本文针对CE认证中对起重机结构强度的计算方法和要求以及与我国现行标准的对比,探讨在产品结构计算过程和计算文件的编制过程中应遵循的计算原则,梳理总结计算规律,提高计算效率。     

金属材料消耗工艺定额简便计算法

<正> 金属切削工具制造行业中生产的螺纹刀具(丝锥、板牙)、铣铰刀、麻花钻等产品都要正确计算材料消耗工艺定额。在计算过程中会遇到大量繁杂的数字,且计算项目多,是一种重复性的计算,计算工作量很大,既费时又易错。因此,如何改进计算方法,提高计算工作效率和计算的正确性,就成为材料消耗工艺定额计算的重要问题。本文提出的通过查系数表,然后进行计算获得结果的方法能使计算变得简便,提高工     

高速动车组车体传热系数模拟计算研究

采用有限元法对某新型高速动车组的车体传热系数进行了分区域法计算和整车模型计算,并对两种计算方法的结果进行了比较。结果表明,整车模型计算的K值比分区域法计算的K值大,计算结果更准确。     

阀门产品工程设计和校核计算系统

结合常规阀门设计思路 ,根据阀门产品设计原理及特点 ,利用常规工具 ,通过建立“设计计算和校核计算标准化屏幕生成器”及“设计计算和校核计算程序悬挂台” ,研究开发了“阀门产品设计计算、校核计算系统。     

声自导鱼雷发现概率统计计算新思路

为了研究声自导鱼雷发现概率的正确解析计算模型,对统计计算模型进行全面的分析讨论。基于鱼雷攻击正常流程建立了一类发现概率统计计算模型(称为绝对运动模型);基于随机相对性,建立了另一类发现概率统计计算模型(称为相对运动模型)。利用灵敏度分析的方法建立了一种提前角误差均方根解析计算模型,基于此提出了一种计算量大幅减小的发现概率统计计算模型(称为部分解析统计计算模型)。仿真计算表明,提出的几种统计计算模型的结果一致,为研究正确的声自导鱼雷发现概率解析计算模型打下了基础。     

渗透汽化级联计算模型及软件开发

膜分离装置的获得离不开对其分离过程的设计计算。本文介绍了渗透汽化级联计算的计算模型,运用VC开发实现了渗透汽化级联计算软件。该软件可以替代繁琐的手工计算。     

MATLAB在潮流计算演示教学中的应用

电力系统潮流计算是电力系统最基本的和最重要的计算,但是潮流计算的过程非常繁琐.MATLAB自1980年问世以来,以其学习简单、使用方便和强大的矩阵处理功能越来越受到世人的关注.利用MATLAB的来计算潮流计算和显示计算结果,可以避免繁琐的计算,缩短计算时间,为电力系统课堂演示教学提供了新思路.     

履带起重机机构设计计算程序的开发

本文阐述了履带起重机各机构之间的关系,说明了机构计算程序化的必要性。同时简单介绍了计算程序的界面和功能,并通过计算结果的查看说明了履带起重机机构设计计算程序完全可以代替手工计算。     

数控加工空间任意直线和平面的角度及坐标计算

采用三角函数和解析几何的方法 ,把空间平面角度计算和空间直线的角度计算相结合 ,建立一种便于计算和应用的空间角度计算的新方法 ,并对二次旋转后工件坐标的计算进行探讨。     

复合材料B基准值计算程序

通过C#语言编制了复合材料B基准值计算程序,根据用户的选择,可以分别选用HB 7618-2009或者MIL-HDBK-17-1F中的方法计算复合材料力学性能数据的B基准值。程序可以完成数据统计特性计算、异常数据检查、子体相容性检验、分布拟合优度检验、环境基准值计算等功能,计算结果以报告的形式输出。通过算例计算,验证了程序结果的正确性,并且对比了两种计算方法的不同及其对结果的影响。程序易于上手,计算方便,大大提高了数据计算分析的效率。     

Hybrid inversion method for equivalent electric charge of thunder cloud based on multi-station atmospheric electric field

This article proposes the hybrid method to inverse the equivalent electric charge of thunder cloud based on the data of multi-station atmospheric electric field. Firstly,the method combines the genetic algorithm( GA) and New ton method through the mosaic hybrid structure. In addition,the thunder cloud equivalent charge is inversed based on the forw ard modeling results by giving the parameters of the thunder cloud charge structure. Then an ideal model is built to examine the performance compared to the nonlinear least squares method. Finally,a typical thunderstorms process in Nanjing is analyzed by Genetic-New ton algorithm with the help of weather radar. The results show the proposed method has the strong global searching capability so that the problem of initial value selection can be solved effectively,as well as gets the better inversion results. Furthermore,the mosaic hybrid structure can absorb the advantages of tw o algorithms better,and the inversion position is consistent with the strongest radar echo.The inversion results find the upper negative charge is small and can be ignored,w hich means the triple-polarity charge structure is relatively scientific,w hich could give some references to the research like lightning forecasting,location tracking.     

POWER FLOW ANALYSIS AND APPLICATION SIMULATION OF ELECTROMAGNETIC CONTINUOUSLY VARIABLE TRANSMISSION

With the structure of two air gaps and two rotors, the electromagnetic continuously variable transmission（EMCVT） is a novel power-split continuously variable transmission（CVT）. There are two kinds of power flowing through the EMCVT, one is mechanical power and the other is electric power. In the mean time, there are three power ports in the EMCVT, one is the outer rotor named mechanical power port and the other two are the inner rotor and the stator named electric power ports. The mechanical power port is connected to the driving wheels through the final gear and the electric ports are connected to the batteries through the transducers. The two kinds of power are coupled on the outer rotor of the EMCVT. The EMCVT can be equipped on the conventional vehicle being regarded as the CVT and it also can be equipped on the hybrid electric vehicle（HEV） as the multi-energy sources assembly. The power flows of these two kinds of applications are analysed. The back electromotive force（EMF） equations are illatively studied and so the dynamic mathematic model is theorized. In order to certify the feasibility of the above theories, three simulations are carried out in allusion to the above two kinds of mentioned applications of the EMCVT and a five speed automatic transmission（AT） vehicle. The simulation results illustrate that the efficiency of the EMCVT vehicles is higher than that of the AT vehicle owed to the optimized operation area of the engine. Hence the fuel consumption of the EMCVT vehicles is knock-down.     

CHARACTERISTCS OF FLUID FILM IN OPTIMIZED SPIRAL GROOVE MECHANICAL SEAL

In order to investigate the sealing performance variation resulted from the thermal deformation of the end faces, the equations to calculate the fluid film pressure distribution, the bearing force and the leakage rate are derived, for the fluid film both in parallel gap and in wedgy gap. The geometrical parameters of the sealing members are optimized by means of heat transfer analysis and complex method. The analysis results indicate that the shallow spiral grooves can generate hydrodynamic pressure while the rotating ring rotates and the bearing force of the fluid film in spiral groove end faces is much larger than that in the flat end faces. The deformation increases the bearing force of the fluid film in flat end faces, but it decreases the hydrodynamic pressure of the fluid film in spiral groove end faces. The gap dimensions which determine the characteristics of the fluid film is obtained by coupling analysis of the frictional heat and the thermal deformation in consideration of the equilibrium condition of the bearing force and the closing force. For different gap dimensions, the relationship between the closing force and the leakage rate is also investigated, based on which the leakage rate can be controlled by adjusting the closing force.     

地铁车辆车轮多边形化形成原因分析

针对地铁车辆车轮多边形化问题,探讨分析车轮多边形化形成原因。提出车轮多边形化是由车轮滚动多周的振动所形成的这一创新观点,并分析车轮多边形化的顶点相位角、主振频率与运行速度之间的关系。以某直线电动机地铁车辆为例,基于建立的多体动力学模型,研究各速度下轮轨垂向力的主导频率,分析易产生车轮9边形化的速度及主导频率特性,指出在72～80 km/h的速度范围内,该直线电动机地铁车辆有形成车轮9边形化的可能。以72 km/h和80 km/h为例,给出此速度下的轮轨垂向力及其主导频率、前转向架直线电动机垂向振动加速度及其主振频率,结果表明两种速度下主导频率分别为39.08 Hz和43.48 Hz的振动有形成车轮9边形化的趋势。指出各速度下的相位角变化,并给出车轮9边形化的示意图。     

Effects of prebuckling deformations on the elastic flexural-torsional buckling of laterally fixed arches

The effect of the prebuckling in-plane deformations on the elastic flexural-torsional buckling of laterally fixed circular arches is studied in this paper. The finite strains and the energy equation for the flexural-torsional buckling of arches have been derived based on an accurate orthogonal rotation matrix. A closed form solution for the elastic flexural-torsional buckling resistance of laterally fixed arches in uniform bending, including the effects of the prebuckling deformations, is obtained. It is found that the notion that the prebuckling deformations increase the flexural-torsional buckling moment of an arch or of a beam is not necessarily correct for a laterally fixed arch or beam in uniform bending, in deference to a laterally pinned arch. When a laterally fixed arch is subjected to positive uniform bending, the effects of the prebuckling deformations decrease the buckling moment, and the reduction of the buckling moment increases with an increase of the included angle and of the out-of-plane slenderness ratio of the arch. When a laterally fixed arch is subjected to negative uniform bending, the effects of the prebuckling deformations decrease the absolute value of its buckling moment when the included angle is very small, but increase the absolute value of the buckling moment when the included angle exceeds a certain value. The increase in the absolute value of the buckling moment increases with an increase of the included angle and of the out-of-plane slenderness ratio of the arch. When the ratio of the out-of-plane to the in-plane second moments of area of the cross-section is not small, both the reduction of the buckling moment of a laterally fixed arch in positive uniform bending and the increase of the buckling moment of a laterally fixed arch in negative uniform bending, are substantial.     

运用EMD和GA SVM的齿轮故障特征提取与选择

针对齿轮故障特征提取,首先将齿轮箱振动信号进行经验模态分解,得到一组固有模态函数.计算各固有模态函数的能量和矩阵的奇异值,采用Shannon熵和Renyi熵度量能量和奇异值分布,构成原始特征子集.再采用遗传算法和最小二乘支持向量机的Wrapper方法选择最优特征子集.该方法能够利用较少的特征参数集准确判别齿轮故障,提高了齿轮故障诊断的精度与效率.     

基于等厚涡轮盘结构的可靠性研究

利用有限元软件对转子进行可靠性分析时,转子的结构以及其他设计参数都是以确定量来进行分析的,不能实现所有参数的随机性分析.以弹性力学为基础,从转子的微元体出发,推导出同时考虑离心力和温度场对转子系统影响的等厚度轮盘任意一点的应力计算式和实际工程常用的变厚度轮盘任意一点的应力计算式.以传统的应力-强度干涉模型为基础,考虑转子随机结构尺寸、温度应力、转速和材料强度等参数的随机性,利用积分随机有限元方法对转子进行可靠性分析,该方法利用确定性有限元实现了随机分析,计算精度较高,实现了转子系统随机结构的可靠性分析.     

PHENOMENON OF CARVED DRIVING WHEELS

A newly found phenomenon of carved driving wheels of a rear-wheel-drive tractor used in an airport is discussed. The circum of every driving wheel is damaged at three regions,which distribute regularly and uniformly. Everyday,the tractor tows a trailer which are times heavier than the tractor,and moves on the same road in the airport. The phenomenon is explained by the torsional self-excited vibration system of the powertrain. The simplified torsional vibration system is discribed by a 2-order ordinary differential equation,which has a limit circle. Experiments and numerical simulations show the followings: Because of the heavy trailer,the slip ratio of the tractor’s driving wheels is very large. Therefore,there is severe torsional self-excited vibration in the tractor’s drivetrain,and the self-excited vibration results in severe and regular fluctuations of the rear wheel’s velocity. The severe fluctuations in velocity fastens the damage of the driving wheels. At the same time,the time interval in which an arbitrary point in the circum of the driving wheel contacts with the road twice is two times more than the period of the torsional self-excited vibration,and this times explained the existence of three damaged regions. At last,it points out that the phenomenon can be avoided when the torsional damping is large enough.     

汽车发动机检测诊断技术探析

通过对现行汽车发动机检测与诊断技术的应用状况进行分析研究,从保证发动机正常工作的动力性和经济性指标方面,介绍了运用先进的汽车诊断专用设备对发动机的各项主要状态参数进行分析、处理的方法和步骤,以实现汽车发动机使用的安全性和最佳经济性的目的。