检索结果-南通市图书馆

Mesh stiffness evaluation of an internal spur gear pair with tooth profile shift

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2016年第9期59卷 1328-1339页

作者： CHEN ZaiGang ZHAI WanMing shao yimin WANG KaiYun State Key Laboratory of Traction Power Southwest Jiaotong University State Key Laboratory of Mechanical Transmission Chongqing University

Tooth profile shift will change the thickness of gear teeth and a part of geometrical parameters of a gear pair, thus influencing its mesh stiffness and consequently the dynamic performances. In this paper, an analytical mesh stiffness calculation model for an internal gear pair in mesh considering the tooth profile shift is developed based on the potential energy principle. Geometrical representations of the tooth profile shift are firstly derived, and then fitted into the analytical tooth stiffness model of gears. This model could supply a convenient way for mesh stiffness calculation of profile shifted spur gears. Then, simulation studies are conducted based on the developed model to demonstrate the effects of tooth profile shift coefficient on the tooth compliances and the mesh stiffness of the internal spur gear pair. The results show that tooth profile shift has an obvious influence on the mean value, amplitude variation and phase of the mesh stiffness, from which it can be predicted that the dynamic response of an internal gear transmission system will be affected by the tooth profile shift.

关键词： mesh stiffness tooth profile shift internal gear gear transmission tooth compliance

Gearbox Deterioration Detection under Steady State,Variable Load, and Variable Speed Conditions

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2009年第2期22卷 256-264页

作者： shao yimin CHRIS K Mechefske OU Jiafu HU Yumei State Key Laboratory of Mechanical Transmission Chongqing University Chongqing 400044 China Department of Mechanical and Materials Engineering Queen＇s University Canada China Chongqing Automobile Research Institute Chongqing 400039 China

Multiple dominant gear meshing frequencies are present in the vibration signals collected from gearboxes and the conventional spiky features that represent initial gear fault conditions are usually difficult to detect. In order to solve this problem, we propose a new gearbox deterioration detection technique based on autoregressive modeling and hypothesis testing in this paper. A stationary autoregressive model was built by using a normal vibration signal from each shaft. The established autoregressive model was then applied to process fault signals from each shaft of a two-stage gearbox. What this paper investigated is a combined technique which unites a time-varying autoregressive model and a two sample Kolmogorov-Smimov goodness-of-fit test, to detect the deterioration of gearing system with simultaneously variable shaft speed and variable load. The time-varying autoregressive model residuals representing both healthy and faulty gear conditions were compared with the original healthy time-synchronous average signals. Compared with the traditional kurtosis statistic, this technique for gearbox deterioration detection has shown significant advantages in highlighting the presence of incipient gear fault in all different speed shafts involved in the meshing motion under variable conditions.

关键词： gearbox condition detection hypothesis test time-varying autoregressive(AR) modeling Kolmogorov-Smimov goodness-of-fit test

Four-Beam Model for Vibration Analysis of a Cantilever Beam with an Embedded Horizontal Crack

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2016年第1期29卷 163-179页

作者： LIU Jing ZHU Weidong CHARALAMBIDES Panos G shao yimin XU Yongfeng WU Kai XIAO Huifang State Key Laboratory of Mechanical Transmission Chongqing University College of Mechanical Engineering Chongqing University Department of Mechanical Engineering University of MarylandBaltimore County National Engineering Research Center of Flat Rolling Equipment University of Science and Technology Beijing

As one of the main failure modes, embedded cracks occur in beam structures due to periodic loads. Hence it is useful to investigate the dynamic characteristics of a beam structure with an embedded crack for early crack detection and diagnosis. A new four-beam model with local flexibilities at crack tips is developed to investigate the transverse vibration of a cantilever beam with an embedded horizontal crack; two separate beam segments are used to model the crack region to allow opening of crack surfaces. Each beam segment is considered as an Euler-Bernoulli beam. The governing equations and the matching and boundary conditions of the four-beam model are derived using Hamilton＇s principle. The natural frequencies and mode shapes of the four-beam model are calculated using the transfer matrix method. The effects of the crack length, depth, and location on the first three natural frequencies and mode shapes of the cracked cantilever beam are investigated. A continuous wavelet transform method is used to analyze the mode shapes of the cracked cantilever beam. It is shown that sudden changes in spatial variations of the wavelet coefficients of the mode shapes can be used to identify the length and location of an embedded horizontal crack. The first three natural frequencies and mode shapes of a cantilever beam with an embedded crack from the finite element method and an experimental investigation are used to validate the proposed model. Local deformations in the vicinity of the crack tips can be described by the proposed four-beam model, which cannot be captured by previous methods.

关键词： cracked cantilever beam embedded horizontal crack transverse vibration four-beam model continuous wavelet transform

An Improved Dynamic Modelling for Exploring Ball Bearing Vibrations from Time-Varying Oil Film

在线全文

学校读者我要写书评

暂无评论

Journal of Dynamics, Monitoring and Diagnostics 2022年第2期1卷 93-102页

作者： Minmin Xu Zhenzhen Song Xiaoxi Ding Guoxing Li yimin shao James Xi Gu State Key Laboratory of Mechanical Transmission Chongqing UniversityChongqing 400044China College of Mechanical and Vehicle Engineering Taiyuan University of TechnologyTaiyuan 030024China School of Engineering University of BoltonBoltonBL35ABUK

Bearings are key components in rotating machinery,which is widely used in many fields,such as CNC machines,wind turbines and induction *** increasingly harsh operation environment can lead to wear and tear on raceways and reduce the precision and reliability of bearing or even *** could relieve the wear to some degree,which is benefit to prolong the bearing’s ***,investigation on the vibration responses under the influence of oil film is of great ***,for mechanism analysis,how to include the oil film into the bearing dynamic model affects the result and efficiency of *** address this problem,this study proposed a fast algorithm through load distribution and interpolation when calculating oil film stiffness and thickness during the solution of bearing vibration *** of oil film on vibration is carried out and a bearing test rig is designed to verify the proposed *** simulation result shows that rotational speed and load have vital effect on oil film and *** experimental result is consistent with the simulation,which shows that the proposed model has a better performance on modeling bearing vibration and the method of considering oil film is reasonable.

关键词： dynamic modeling fault diagnosis lubrication rolling elements bearing time-varying oil film

Frequency of HLA-A*03 associates with HIV-1 infection in a Chinese cohort

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Life Sciences) 2013年第11期56卷 1014-1019页

作者： ZHANG WeiLun WANG Li HONG KunXue LIU YanXin SU Bing XU Cheng XU JianQin RUAN YuHua shao yimin ZHENG DeXian Institute of Basic Medical Sciences Chinese Academy of Medical Sciences & Peking Union Medical College State Key Laboratory for Infectious Disease Prevention and Control National Center for AIDS/STD Control and Prevention Anhui Center for Disease Control and Prevention Fuyang Center for Disease Control and Prevention

During the early mid-1990s, a number of rural farmers across central China were employed to the unregulated plasma- selling-activity and many of them were infected by HIV-1. However, AIDS progression in the former blood donors （FBDs） is various. The aim of this study is to assess human leukocyte antigen （HLA） class I allele distribution in FBDs and evaluate its association with HIV-1 infection and disease progression. A total of 353 FBDs were enrolled in the cohort including 294 ART na＇fve HIV-1 seropositive and 59 HIV-1 seronegative age-matched subjects. The viral load and CD4/CD8 T cell counts were assessed in all subjects. Compared with HIV-seropositive group, the frequency of HLA-A＊03 in control was significantly higher. After classifying the HLA-B alleles of the subjects according to the presence of Bw4/Bw6 serological epitopes, detri- mental effect of HLA Bw6/Bw6 homozygosity was also confirmed in the HIV-seropositive subjects. This study provides nov- el evidence on HLA class I allele distribution and association of HLA-A＊03 frequency with HIV-1 infection and viremia in the HIV-1 infected FBDs, which may throw light on intervention strategy for the HIV-1 infection and our understanding how host immunity and genetic background affect HIV infection and AIDS progression.

关键词： leukocyte antigen class I HIV-1 infection viremia control Chinese former blood donor cohort

基于角域振动信号特征统计量的发动机故障分类方法

在线全文

学校读者我要写书评

暂无评论

中国机械工程 2014年第10期25卷 1374-1380页

作者：丁岩邵毅敏重庆大学机械传动国家重点实验室重庆400044

为了提高发动机故障分类的准确率和成功率,提出了基于角域信号特征统计量的发动机故障分类方法。包括:利用编码器进行发动机振动信号的等角度采样;采用小波包分析和相关系数法获取发动机角域信号的特征阶次;选取特征阶次信号的能量比、... 详细信息

为了提高发动机故障分类的准确率和成功率,提出了基于角域信号特征统计量的发动机故障分类方法。包括:利用编码器进行发动机振动信号的等角度采样;采用小波包分析和相关系数法获取发动机角域信号的特征阶次;选取特征阶次信号的能量比、标准差比、谱能量比及谱均值比4组参数作为角域信号特征统计量来提取发动机故障特征;采用支持向量机法对发动机故障进行分类。连杆轴承配合间隙故障的台架试验结果证明:相比于传统的分类方法,该方法明显提高了发动机故障分类的准确率。

关键词：等角度采样特征统计量内燃机故障分类

科技学术期刊名词规范化工作的现状分析和建议

在线全文

学校读者我要写书评

暂无评论

编辑学报 2015年第4期27卷 346-347页

作者：邵一敏中国移动通信集团设计院有限公司<电信工程技术与标准化>编辑部北京100080

阐明科技名词规范化的重要性,认为科技名词规范化工作任重道远。通过列举通信技术名词规范化应用的实例,就已公布的规范名词、没有纳入规范的名词和新词的使用应遵循的原则提出建议。

关键词：科技术语科技学术期刊标准化

考虑内圈挡边表面波纹度的圆锥滚子轴承振动特征研究

在线全文

学校读者我要写书评

暂无评论

机械工程学报 2018年第8期54卷 26-34页

作者：刘静吴昊邵毅敏师志峰重庆大学机械传动国家重点实验室重庆大学机械工程学院

表面波纹度是圆锥滚子轴承滚道表面的主要形状误差之一。针对圆锥滚子轴承内圈挡边表面波纹度诱发的时变激励机理和动力学建模的问题,考虑流体动力润滑油膜与轴承轴向和径向变形耦合激励作用的影响,提出考虑时变激励的圆锥滚子轴承挡边... 详细信息

表面波纹度是圆锥滚子轴承滚道表面的主要形状误差之一。针对圆锥滚子轴承内圈挡边表面波纹度诱发的时变激励机理和动力学建模的问题,考虑流体动力润滑油膜与轴承轴向和径向变形耦合激励作用的影响,提出考虑时变激励的圆锥滚子轴承挡边表面波纹度动力学模型,并通过试验结果验证模型的有效性;研究内圈挡边表面波纹度时变激励下的圆锥滚子轴承的振动响应特征;分析内圈挡边表面波纹度幅值和阶次对圆锥滚子轴承振动响应特征的影响规律,解决圆锥滚子内圈挡边波纹诱发的时变激励及其动力学建模问题,为获得准确的含内圈挡边表面波纹度的圆锥滚子轴承的动力学响应特征提供新的手段和方法。结果显示,轴承的振动水平随着内圈挡边表面波纹度幅值的增大逐渐加剧;内圈挡边表面波纹度会改变轴承振动加速度响应频谱的峰值频率;当内圈挡边表面波纹度的阶次为滚动体数目的整数倍时,圆锥滚子轴承振动值将出现峰值。因此,控制内圈挡边表面波纹度的幅值与阶次将有利于抑制圆锥滚子轴承的振动水平。

关键词：圆锥滚子轴承挡边波纹度流体弹性动力润滑动力学建模

基于自然驾驶试验的山区公路纵坡路段驾驶负荷分析

在线全文

学校读者我要写书评

暂无评论

东南大学学报（自然科学版） 2017年第3期47卷 619-625页

作者：徐进汪旭林伟王灿邵毅明重庆交通大学重庆市交通运输工程重点试验室重庆400074 重庆交通大学交通运输学院重庆400074

为得到驾驶人在纵坡路段上行车时的驾驶负荷及其影响因素,在山区复杂线形公路上开展了自然驾驶试验,采集了真实驾驶习惯条件下的汽车行驶速度、轨迹、加速度等运行参数和驾驶人心电信号,分析了公路纵面线形参数、汽车加(减)速度与驾驶... 详细信息

为得到驾驶人在纵坡路段上行车时的驾驶负荷及其影响因素,在山区复杂线形公路上开展了自然驾驶试验,采集了真实驾驶习惯条件下的汽车行驶速度、轨迹、加速度等运行参数和驾驶人心电信号,分析了公路纵面线形参数、汽车加(减)速度与驾驶人心率增长率H_(RI)之间的关系.结果表明,纵坡参数、加速度与H_(RI)三者之间相互影响.坡长与H_(RI)之间存在较弱的正相关性;坡度与H_(RI)之间存在较强的相关性,其中下坡路段的相关性强于上坡路段,并且坡长越长,坡度增加导致H_(RI)的增长越明显;H_(RI)与加(减)速度正相关,坡度越大,H_(RI)对加(减)速度的变化越敏感,且下坡路段减速度与H_(RI)的相关性较上坡路段加速度与H_(RI)的相关性更显著.

关键词：山区公路驾驶负荷纵断面坡度坡长心率增长率