发动机振动信号不对称现象分析

某柴油机振动信号出现不对称现象,其最大值与最小值差异较大。该信号的频谱特性表明:在0-100 Hz频段内,存在发动机转速的2阶、4阶、6阶分量,其中2、4阶分量之间存在某种微妙的相位关系,导致其在时域叠加后出现不对称现象。本文进一步研究了2阶、4阶分量在800~3 000 r/min整个转速范围内的振动位移,发现低转速时比高转速时大87.5%以上。根据发动机力学模型认为这是由发动机倾覆力矩引起的,指明了改进方向,为该发动机的改进方案提供了检验依据。     

城市轨道交通地下线工程条件对振动环境影响的研究分析

本文根据国内城市轨道交通工程环境影响评价中地下线环境振动影响预测和环境保护竣工验收监测结果，统计分析了地铁运营时产生的环境振动随敏感点与线路的距离、列车运行速度等变化情况，并根据环境振动影响范围提出了满足环境振动标准的控制距离。     

齿轮箱的失效原因与振动诊断

齿轮箱是各类机械设备通常具备的变速传动部件，齿轮和齿轮箱的工作状态的好坏直接影响整个机械系统的工作，它们的故障往往是造成系统不能正常运转的常见原因之一，所以它们的制造质量、工作平稳性和噪声是机器制造质量的重要标志。文章介绍了柴油机齿轮箱的失效形式和原因，并通过振动监测具体分析了某齿轮箱的故障。     

一种轻型天线稳定平台的设计

介绍了一种适用于大振动、冲击、强电磁干扰、倒单摆式大惯量负载等特殊要求的轻型天线稳定平台的机电一体化设计.可对类似的应用提供有用的借鉴.     

某站场地基强夯振动影响范围研究

针对某站场地基采用6000kN·m夯击能强夯加固海漫滩填海区工程，现场测试了地表振动速度，在此基础上，分析研究了振动在水平方向的衰减规律、主振频率等，分析了拟建场地边立交桥在不同夯击能下的安全距离．结果表明：地表最大振动速度的衰减规律满足乘幂关系；强夯产生的振动的主振频率均处于10Hz以下；以地表振动速度作为判别标准，测得该场地在6000kN·m夯击能下对立交桥的安全距离为30m．     

地铁交通诱发邻近建筑物振动的实测与分析

根据现场实测数据,对某地铁2号线沿线典型区段地铁引起的临近建筑物振动实况和振动特性及其传播规律等进行了分析研究。结果表明:地铁诱发的沿线建筑物的振动以竖向为主,且楼层竖向振动基本表现为整体振动;在框架结构中,振动信号主要是沿柱子向上部楼层传播;楼层振动主要表现为低频的楼板振动,楼层间信号的放大主要集中在20 Hz以下的低频信号。此外,本文还给出建筑物振动实测资料的评价分析,为评估地铁运营诱发的环境振动与城市规划设计提供参考。     

广珠西线高速公路沉降速率与剩余沉降关系分析

广珠西线高速公路实测沉降表明,沉降速率与剩余沉降基本为线性关系,沉降速率与剩余沉降的平方基本为正比关系,进而从理论上论证了两者的关系。两者的这种关系有利于将工后沉降法、沉降速率法统一起来。     

发动机带传动中皮带寿命提高方法研究

设计一种新型的通用皮带预紧力测量装置，通过分析发动机皮带传动中的横向振动，提出带轮结构布置原则。实验证明，根据该原则进行皮带轮结构布置并设定准确的皮带预紧力，可减小传动打滑现象，有效提高皮带的使用寿命及皮带传动效率.     

Railway wheel-flat and rail surface defect modelling and analysis by time–frequency techniques

Damage to the surface of railway wheels and rails commonly occurs in most railways. If not detected, it can result in the rapid deterioration and possible failure of rolling stock and infrastructure components causing higher maintenance costs. This paper presents an investigation into the modelling and simulation of wheel-flat and rail surface defects. A simplified mathematical model was developed and a series of experiments were carried out on a roller rig. The time–frequency analysis is a useful tool for identifying the content of a signal in the frequency domain without losing information about its time domain characteristics. Because of this, it is widely used for dynamic system analysis and condition monitoring and has been used in this paper for the detection of wheel flats and rail surface defects. Three commonly used time–frequency analysis techniques: Short-Time Fourier Transform, Wigner–Ville transform and wavelet transform were investigated in this work.     

The dynamic response of rail support

This research reviews principles behind the dynamic response of rail supports, and introduces a method of analysis to find the maximum response in a realistic setting. Assuming a time-dependent, moving mass with massive wheels is essential, because the ratio of the moving mass to the rail mass is significant. However, the dynamic response of the track is not affected by dynamic properties of the train other than its unsprung mass, because the natural frequencies of the train suspension and track are significantly different. A numerical method is developed to model the dynamic response based on these principles, and applied to the Korean urban transit. The dynamic response includes multiple peaks with a large amplitude range, creating noise while the wheel passes the support. The dynamic impact factor (DIF) for the rail support depends mainly on the stiffness and damping of the rail support. The DIF for the rail moment is below the code value, whether this value is based on numerical analysis or on-site measurements. However, our numerical analysis results in a DIF for support settlement that is greater than the code value, if the damping is less than 3%.