Dynamic analysis of harmonically excited non-linear system using multiple scales method

An analytical method is presented for evaluation of the steady state periodic behavior of nonlinear systems. This method is based on the substructure synthesis formulation and a MS (multiple scales) procedure, which is applied to the analysis of nonlinear responses. The proposed procedure reduces the size of large degrees-of-freedom problem in solving nonlinear equations. Feasibility and advantages of the proposed method are illustrated with the nonlinear rotating machine system as an example of large mechanical structure systems. In addition, its efficiency for nonlinear response prediction will be shown by comparison of other conventional methods.     

Dynamic analysis and design of uncertain systems against random excitation using probabilistic method

In this paper, a method to obtain the sensitivity of eigenvalues and the random responses of the structure with uncertain parameters is proposed. The concept of the proposed method is that the perturbed equation of each uncertain substructure is obtained using the finite element method, and the perturbed equation of the overall structure is obtained using the mode synthesis method. By this way, the reduced order perturbed equation of the uncertain system can be obtained. And the response of the uncertain system is obtained using probability method. As a numerical example, a simple piping system is considered as an example structure. The damping and spring constants of the support are considered as the uncertain parameters. Then the variations of the eigenvalues, the correlation function and the power spectral density function of the responses are calculated. As a result, the proposed method is considered to be useful technique to analyze the sensitivities of eigenvalues and random response against random excitation in terms of the accuracy and the calculation time.     

Influence of bearing stiffness on the static properties of a planetary gear system with manufacturing errors

Hybrid finite element analysis was used to analyze the influence of bearing stiffness on the static properties of a planetary gear system with manufacturing errors. The effects of changes in stiffness were similar for most of the manufacturing errors. State variables were most affected by the stiffness of the planet bearings. Floating either the sun or carrier helps to equal load sharing and minimizes the critical tooth stress. The effects of a floating sun and carrier are similar, but it is not recommended that both float, because this can induce greater critical tooth stress. Planet bearing stiffness should be optimized. Both load sharing and critical tooth stress should be considered to determine optimal bearing stiffness.     

轴承套圈的预应力硬态切削分析

通过对轴承套圈工作状态的运动学和力学分析,明确了轴承工作时内圈先于静止外圈表面产生疲劳剥落的原因;阐述了轴承外圈外圆表面出现的残余拉应力现象和原因,并提出一种可改善轴承零件加工表面残余应力状态的预应力硬态切削方法。理论分析和实验结果证明,该方法可使轴承零件加工表面产生残余压应力,提高轴承的接触疲劳寿命。     

承力框螺栓断裂分析与改进设计探讨

针对某型飞机第二交点框框缘下部 3个螺栓在全机疲劳试验中出现疲劳断裂情况 ,从该框接头区的结构形式、连接支臂与框缘螺栓受力特点、全机疲劳试验情况出发 ,对螺栓断裂的原因进行了分析 ,并根据分析结果探讨了该螺栓的改进方案     

An envelope analysis based on the resonance modes of the mechanical system for the bearing defect diagnosis

In this paper, an envelope estimation algorithm based on the resonance modes of the mechanical system is proposed and the exponential decay frequency of the envelope signal could be further estimated to be a quantified index for the bearing defect diagnosis. According to the vibration spectrum of the bearing system, the resonance frequencies in the range of its corresponding resonance modes could be initially designated and further revised. Under the assumption of stepwise functions for the envelope signals, the vibration signal could be decomposed into the sinusoidal function bases with fundamental frequencies at the corresponding resonance frequencies. Thus, the envelope signals could be retrieved by estimating the stepwise functions. In addition, the reconstructed signal with noise rejection could be derived from the envelope signals. According to the envelope signals, the exponential decay frequency is estimated to be the diagnosis index of the bearing running condition. In the simulated and experimental studies, it is found that the envelope estimation algorithm could be effectively applied in the signal processing for the bearing vibrations. In addition, the envelope spectra also show good consistency between the proposed method and the high-frequency resonance technique. Finally, it is shown that the exponential decay frequency could successfully be the quantified index for the bearing defect diagnosis.     

微型机电系统的建模与仿真研究

概述了开展微型机电系统 (MEMS)建模与仿真研究的意义和必要性。提出了MEMS建模与仿真技术的特点 :( 1)多物理场耦合 ;( 2 )材料特性的变化 ;( 3 )依赖快速有效的算法 ;( 4 )原子尺度仿真。分别从器件级仿真、过程仿真和系统级仿真三个层次说明了MEMS仿真的方法。最后结合MEMS建模与仿真技术的发展现状 ,指出了该领域今后的发展趋势。     

PHEV行星齿轮传动系统设计及仿真

分析了并联式混合动力电动汽车(PHEV)行星齿轮传动系统的设计条件,针对条件要求进行了配齿计算,选择了齿轮的主要参数.在并联式混合动力电动汽车启动加速阶段,利用Simulink软件建立了系统的转速关系、输出扭矩和功率的仿真模型,仿真得出系统的输出转速特性、功率分配特性和扭矩输出特性曲线.结果表明:设计的行星齿轮系统符合PHEV启动加速工作模式的动力分配性要求.     

轮履复合机器人行走机构的设计及运动学分析

提出了一种新式轮履复合机器人的行走机构的设计方案。对机器人行走机构进行了结构设计,设计包括机器人的轮履变体轮的设计及其传动系统的设计。轮履复合机器人在履带式移动和轮式移动之间的相互转变,使得机器人具有在正常路面的高机动性以及在复杂路面的高通过性.同时,机器人还具有机构可重构、体积小等特点。最后,对机器人轮式行走和履带方式行走特别是履带方式越沟壑、爬斜坡、上台阶作了运动学分析,为后续机器人的研究提供了理论基础。     

柔性石墨纸轧机动刚度薄弱部位辨识与优化

借助谐响应分析辨识出柔性石墨纸轧机动刚度的薄弱环节,并利用灵敏度分析方法建立该环节的优化数学模型,进而实现对整机动刚度的提升。通过对各部件刚度提升前后的柔性石墨纸轧机进行模态分析,并对比各部件对整机固有频率的影响,辨识出薄弱部位为底座,故以底座为优化对象;将牌坊Y向共振频率对底座尺寸的灵敏度曲线拟合得出优化目标函数,以Y向共振频率为优化目标,质量为约束条件建立优化方程并求解;对比优化前后整机的动刚度,得出:在质量不增加的情况下,整机薄弱频率提升了24.1%,Y向振幅降低了15.9%。为提高优化效率提供了理论依据和参考。     

配气系统的设计分析与试验研究

讨论了1100型柴油机的配气系统的设计与分析，并对改进的摩擦副进行装机性能试验与耐久性试验，试验结果表明其性能和工作可靠性均符合主机的要求。     

粮食多功能出入仓机设计

所论及的新型粮食多功能出入仓机，基于系统设计和功能设计的思想，在对原粮食出入仓作业流程进行分析的基础上，重新设计新的作业流程，将粮食的风选除杂、振动除杂、入库、出库作业集成在一个机械系统中完成：此外对该装备的结构原理、特点及功用进行了介绍一试验及现场应用结果表明，该装备使用灵活方便，除杂效果可控，生产效率高，工作环境清洁，在粮食收储企业具有广泛的应用前景。     

套筒式铣头主轴系统热变形分析及解决措施？

本文就套筒式铣头主轴系统运转温升产生的热变形时主轴精度的影响进行了分析，并提出相应的解决措施，收到了良好的效果。     

IC卡式热能表充值系统的设计

IC卡式热能表充值系统是专用于IC卡式热能表充值管理的系统，本文从整体上介绍了IC卡式热能表充值系统的设计过程，设计包含读卡器和安装在PC机上的充值系统软件两部分的设计，并选用RS232 Modbus协议作为读卡器和PC机之间通信方式。     

机载交联设备综合检测系统设计与实现

介绍了某型机载交联设备综合检测系统的功能。主要阐述了系统的设计与实现，最后讨论了操作系统及开发软件的选择。     

风力机叶片气动设计与结构研究

采用Wilson模型优化设计水平轴风力机叶片的气动外形;利用有限元软件对玻璃钢叶片在风力、重力和离心力的耦合作用下的静力学、稳定性和动力学进行仿真分析.通过对叶片额定风况下的静力学和稳定性分析,不仅能获取叶片的应力和应变分布,而且可检验叶片设计的安全性和合理性.通过叶片动力学分析,计算叶片的振动频率,判断能否避免共振,实现正常运行.     

反求设计中非接触式位移检测的研究与应用

论述了反求设计中非接触式位移检测的基本原理,特别是对其检测的精度进行了详尽的分析,并基于此构建了一套测控系统,系统在非接触式位移检测中有较好的位移采样能力。     

专用双刀立式车床主轴系统结构设计及分析

对加工法兰盘的专用双刀立式车床主轴系统的布置进行分析,根据双刀立式车床的受力特点,以及盘类零件的加工特点,给出合理的轴段布置及轴承布置.基于有限元的方法对主轴一般受力情况进行力学分析,得出车床主轴设计时首先应该满足设计要求.对于双刀立式车床主轴的设计给出一般性的思路.     

对旋风机电动机轴承的失效分析及结构改进

由于对旋轴流式风机电动机轴承要承受大的轴向负荷和径向负荷，实际使用过程中常发生电动机轴承损坏的现象。这里针对此问题，通过对比对旋风机电动机输出轴安装叶轮前后的受力情况，对电动机轴承进行受力分析，查明电动机轴承损坏的机理。并在对电动机轴承组进行结构分析的基础上，给出两种有效的轴承组结构。     

影响切削工件表面质量的因素分析及要因的检测系统设计

采用因果分析图等质量分析工具分析了影响切削加工工件表面质量的原因,并找出了影响表面粗糙度的主要因素是切削力、切削温度和机械设备振动.针对切削力和切削温度影响因素,将薄膜热电偶技术引入切削温度检测,设计了一套切削力和切削温度的完整检测系统.试验表明,该检测系统人机交互作用强,操作简单,使用方便.