任意冲击脉冲波形发生器动态仿真研究

通过对后峰锯齿波冲击脉冲的动态仿真，讨论了应用流体力学和弹性特性曲线拟合原理实现任意冲击脉冲波形的机理，进而可以获得任意冲击脉冲波形发生器。     

任意冲击脉冲波形发生器动态仿真研究

通过对后峰锯齿波冲击脉冲的动态仿真 ,讨论了应用流体力学和弹性特性曲线拟合原理来实现任意冲击脉冲波形的机理 ,进而可以获得任意冲击脉冲波形发生器     

簧片式后峰锯齿波力脉冲成形机理及其装置的研究

通过简便的技术途径，实现符合冲击试验规范中规定的后峰锯齿波力脉冲，是目前冲击环境试验中急待解决的问题之一，本文对采用片弹簧和刚度可调式线性螺旋簧刚度拟合技术，实现了上述后峰锯齿波力脉冲波形的机理，技术途径进行探讨，并应用簧片预应力技术和卸荷技术，改善了簧片的应力状态，提高了使用寿命，为研制标准中规定的其它力脉冲波形（如半正弦波，梯形波）的力脉冲产生装置提供了理论依据和技术实施途径。     

车载机柜动态特性分析与研究

利用CAD软件对某型车载机柜建立了有限元模型;在分析其结构特点和材料力学性能的基础上,基于ANSYS软件,对车载机柜进行了模态、正弦波和后峰锯齿波冲击特性分析,校核其静、动态特性是否满足要求,并提出合理的改进意见.     

浅谈冲击响应谱试验

大部分产品试件即使在试验室里通过了用对称的脉冲谱即半正弦、梯形波和锯齿波做的冲击试验,在野外和实际环境中还有损坏,因此简单的用时间历程曲线或脉冲波作为冲击试验规范已经不能满足试验需求。所以复杂的冲击试验——冲击响应谱试验规范在越来越多的被提及和使用。本文主要介绍冲击响应谱在电动振动试验系统中的应用。     

浅谈冲击响应谱试验

大部分产品试件即使在试验室里通过了用对称的脉冲谱即半正弦、梯形波和锯齿波做的冲击试验,在野外和实际环境中还有损坏,因此简单的用时间历程曲线或脉冲波作为冲击试验规范已经不能满足试验需求.所以复杂的冲击试验--冲击响应谱试验规范在越来越多的被提及和使用.本文主要介绍冲击响应谱在电动振动试验系统中的应用.     

一种新型液压脉冲发生器的试验研究

提出一种适用于冲击碰撞试验的锥形间隙小孔组合节流液压脉冲发生器。通过调节节流面积和碰撞速度等参数,运用试验方法研究了脉冲发生器的负载自适应性、运动负载制动的高效性、脉冲波形可调性以及油液温升特性等机械动态特性。试验结果表明,采用开环控制方法调节节流口的通流面积来实现脉冲波形的调节正确可行,脉冲发生器可以满足相应冲击试验的要求。     

雷电冲击试验冲击电压发生器调波电阻的确定

在进行雷电冲击试验时,需对冲击电压发生器的调波电阻(波前电阻Rf、半峰值电阻Rt)进行调节,使冲击波形符合标准IEC60060-1的要求:波前时间tf为1.2μs(±30%),半峰值时间tt为50μs(±20%)。针对快速确定冲击电压发生器调波电阻的问题,对冲击电压发生器放电等值回路进行了数学分析,建立了关于Rf、Rt的非线性方程组,并采用混合遗传算法进行了求解。得到Rf、Rt的数值计算解后,在Matlab环境下对雷电冲击放电回路进行了仿真分析。最终,在高压试验大厅进行了现场试验加以验证。研究结果表明,所采用的调波电阻确定方法能够保证冲击波形符合标准要求,缩短设备调试时间,可为现场试验人员提供理论指导。     

小型跌落冲击台的设计原理

本文介绍了一种长脉冲持续时间的小型跌落冲击台，并对其结构特点，工作原理，冲击试验的波形进行阐述和分析。文中还提及了有关改进措施。     

小型跌落冲击台的设计原理

介绍一种长脉冲持续时间的小型跌落冲击台，并对其结构特点，工作原理，冲击试验的波形进行阐述与分析，文中还提及有关改进措施。     

冲击脉冲法评价滚动轴承故障的系数自修正方法

对机械工业中常用的评价滚动轴承故障的冲击脉冲法,提出了一种基于神经网络的故障评价系数自修正策略。这一修正系数模块已用于工业现场滚动轴承状态在线监测系统中,经长期运行的实践证明,自修正系数模块的引入极大地提高了滚动轴承运行状态判断的准确性。     

THEORY AND EXPERIMENT ON THE VISCOUS HEATING OF FLUID DAMPER UNDER SHOCK ENVIRONMENT

A specially designed fluid damper used as negative shock pulse generator in the shock resistance test system to dissipate the shock input energy in transient time duration is presented. The theoretical modeling based on the three-dimensional equation of heat transfer through a fluid element is created to predict the viscous heating in the fluid damper under shock conditions. A comprehensive experimental program that investigates the problem of viscous heating in the fluid damper under different shock conditions is conducted on the shock test machine to validate the analytical expression. Temperature histories for the fluid within the damper at two locations, the annular-oriflce and the-end-of stroke of the damper, are recorded. The experimental results show that the theoretical model can offer a very dependable prediction for the temperature histories in the damper for increasing input velocity. The theoretical model and experimental data both clearly indicate that the viscous heating in the damper is directly related to the maximum shock velocity input and the pressure between the two sides of the piston head.     

Sifting process of EMD and its application in rolling element bearing fault diagnosis

Among the vibration-based fault diagnosis methods for rolling element bearing, the shock pulse method (SPM) combined with the demodulation method is a useful quantitative technique for estimating bearing running state. However, direct demodulation often misestimates the shock value of characteristic defect frequency. To overcome this disadvantage, the vibration signal should be decomposed before demodulation. Empirical mode decomposition (EMD) can be an alternative for preprocess bearing fault signals. However, the trouble with this method’s application is that it is time-consuming. Therefore, a novel method that can improve the sifting process’s efficiency is proposed, in which only one time of cubic spline fitting is required in each sifting process. As a consequence, the time for EMD analysis can be evidently shortened and the decomposition results simultaneously maintained at a high precision. Simulations and experiments verify that the improved EMD method, combined with SPM and demodulation analysis, is efficient and accurate and can be effectively applied in engineering practice. This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin Hongbo Dong was born in Chaoyang, China, in 1979. He received the B.E. and M.E. degree from Northwestern Polytechnical University in Mechanical Engineering in 2002 and 2005 respectively and received the Ph.D degree from Xi’an Jiaotong University in Mechanical Engineering in 2009. His research interests include fault diagnosis of rotor and bearing system. Bing Li was born in Xuzhou, China, in 1976. He received the B.E. and M.E. degree from Northwestern Polytechnical University in Mechanical Engineering in 1999 and 2002 respectively and received the Ph.D degree from Xi’an Jiaotong University in Mechanical Engineering in 2005. After graduating from Xi’an Jiaotong University, he works as a lecturer in Xi’an Jiaotong University. His research interests include wavelet finite element theory and its application in fault diagnosis.     

Condition monitoring studies on spindle bearing of a lathe

In modern industry, machinery must become increasingly flexible and automatic. In order to increase productivity, enhance quality and reduce cost, machine tools have to work free of any failure. When a failure occurs in a machine tool, it is necessary to identify the causes as early as possible. Machine tool condition monitoring is very important to achieve this goal. Condition monitoring is generally used on the critical subsystem of any machine tool. This paper endeavors to focus on the condition monitoring aspects on the machine tool element. In the present study, a critical subsystem has been identified based on the failure data analysis. Condition monitoring techniques like vibration monitoring, acoustic emission, Shock Pulse Method (SPM) and surface roughness have been successfully used for fault identification.     

限流用PTCR耐雷电波测试仪的研制

】介绍了正温度系数热敏电阻ＰＴＣＲ耐雷电波冲击测试仪的工作原理和基本性能。并从雷电波波形产生电路、时序控制及延时电路、冲击次数控制电路等方面详细分析了电路设计思想。     

An inverse shock response spectrum

The shock response spectrum (SRS) is a tool commonly used by application engineers that characterizes the severity of a transient acceleration. Due to the definition of the SRS, neither an analytical nor a unique inverse exists for an arbitrary function. An SRS presented without any temporal information makes creating a corresponding acceleration time history for an experimental or numerical study prohibitively difficult without a rigorous method to determine an inverse of the SRS (a corresponding time history). The present work develops a method to calculate an inverse of an arbitrary SRS using three sets of well characterized basis functions: an impulse function, a sine function/damped sine function, and a modified Morlet wavelet. These three basis functions are specifically chosen for the properties of their transformations: the impulse introduces a constant increase to the SRS above a given frequency, the sine wave introduces a narrow peak at a given frequency, and the Morlet wavelet introduces a plateau with an adjustable width and relative height. Using the definition of the SRS, the transformations of the basis functions are calculated and these expressions are used to derive a methodology for calculating an inverse SRS. The effectiveness of the method is demonstrated by several examples. The quality of an inverse SRS is evaluated by comparing the SRS of the inverse to the target SRS. This method is developed in order to provide a quick estimate of a corresponding time history; in applications where a higher fidelity representation of the SRS is needed than can be provided by the method developed, a genetic algorithm is used to optimize the coefficients of the basis functions. Given a sufficient number of basis functions for the optimization, the resulting SRS can almost exactly match a randomly generated target SRS that is nonzero over the frequency range considered. For applications in which the permissable basis functions are limited (such as for an experimental test apparatus), an extension of the genetic algorithm method is discussed.     

偏心高速冲击杆有限单元分析

以模锻锤锤杆为对象，借助有限单元法，分析了细长杆在对中、偏心条件下高速冲击时的应力分布，得出了应力沿杆长的分布图，并研究了不同圆角半径和材质对应力分布的影响，为该类杆件结构的改进提供了理论依据     

STUDY ON THE PERIODIC WATERHAMMER INITIATED BY A NOVEL HYDRAULIC SHOCK GENERATOR

0 I~UCnowDessme ~lents inihated by the sudden challges of flow ~is are collUnonly refewh to waterher or in some case"oil halnlner". They are generally regalded as ~ Phenomena in oil andchendcal indusal, power Plants as well as fluid power ~ssion systemS, as they always damage Pipes,valveS and Other system elements, and somehmes they even cause severe accidents. Gnd effortS have homade to Pedct, Prevent and contwl the watelhalnmer by a number of researChers. The most sighficantcontributio…     

新型全方位脉象仪设计方案

提出一种基于古代中医脉象描述的特点的新型全方位脉象仪设计与实现方案。该方案通过脉搏传感器全方位采集脉搏数据，绘制整体脉搏-脉体时空综合图，以反映脉体、脉力、脉长；整体脉搏-脉势时空综合图，以反映脉宽、脉体、脉流、脉力；整体脉搏-脉流时空综合图，以反映脉流、脉长、脉宽等，从而准确反映脉搏整体动态变化，使脉搏的“位、数、形、势”得到精确体现。     

某悬架减振器的精确建模及仿真

针对某轻型汽车悬架减振器结构 ,建立了精确的计算模型 ,经过仿真计算和与试验数据的对照 ,证明了模型的准确性 ,并对此减振器仿真计算结果与试验数据的差异提出了改进建议