提出了一种基于变量预测模型(Variable predictive model based class discriminate,简称VPMCD)和改进固有时间尺度分解(Intrinsic time-scale decomposition,简称ITD)算法的滚动轴承故障诊断方法。VPMCD方法充分利用了特征值之间的相...提出了一种基于变量预测模型(Variable predictive model based class discriminate,简称VPMCD)和改进固有时间尺度分解(Intrinsic time-scale decomposition,简称ITD)算法的滚动轴承故障诊断方法。VPMCD方法充分利用了特征值之间的相互内在关系来建立预测模型,并以这些模型对待诊断样本的特征值的预测结果作为分类依据来进行模式识别。ITD方法能自适应地将非平稳信号分解成为若干单分量信号(固有旋转分量,Proper rotation component,简称PRC)之和。首先对ITD算法进行了改进;接着采用改进ITD算法对原始振动信号进行分解得到多个内禀尺度分量(Intrinsic scale component,简称ISC);然后对包含主要故障信息的若干内禀尺度分量建立对数正态分布模型,并提取其对数均值和对数标准差作为故障特征值;最后采用VPMCD模式识别方法得到各故障特征值的预测模型,并利用预测模型对待诊断样本的故障类型和工作状态进行分类和识别。对滚动轴承正常、外圈故障和内圈故障振动信号的分析结果表明了该方法的有效性。展开更多
Carrying on a series of compression and shear tests by a large number of specimens, reliabilities of T300/QY8911 laminated composite were studied when dispersibility models were described. The results show that the st...Carrying on a series of compression and shear tests by a large number of specimens, reliabilities of T300/QY8911 laminated composite were studied when dispersibility models were described. The results show that the stress is linearly dependent on the strain and the damage modes of specimens are brittle fracture for both kinds of tests. Dispersibility models of compression and shear strength are expressed as Re-N（415.39, 6 586.36） and Rs-ln（5.071 8, 0.155 3）, respectively. When normal and lognormal distributions were used to describe the dispersibility models of compression and shear strength, and the compression or shear load follows the normal distribution, the almost same failure probability can be obtained from different reliability analysis methods.展开更多
文摘为探索高速公路出口事故发生的关键诱因,依托美国佛罗里达州24条高速公路上405个出口匝道的历史事故和道路交通数据,验证了出口匝道事故服从于对数正态分布.以匝道交通量、匝道长度和设计一致性(分别以平均半径、曲率变化率、运行速度差和运行速度变化率度量)为解释变量,以2004—2006年间事故数为因变量,建立了4个泊松对数正态事故预测模型,其中以速度变化率表征设计一致性的事故预测模型具有最好的拟合度.基于最优拟合度模型的弹性分析表明,运行速度变化率及匝道长度为关键因素;基于安全考虑,出口匝道速度变化率宜控制在20%以内,出口匝道极限最小长度不宜小于200 m,一般最小长度不宜小于400 m.
文摘提出了一种基于变量预测模型(Variable predictive model based class discriminate,简称VPMCD)和改进固有时间尺度分解(Intrinsic time-scale decomposition,简称ITD)算法的滚动轴承故障诊断方法。VPMCD方法充分利用了特征值之间的相互内在关系来建立预测模型,并以这些模型对待诊断样本的特征值的预测结果作为分类依据来进行模式识别。ITD方法能自适应地将非平稳信号分解成为若干单分量信号(固有旋转分量,Proper rotation component,简称PRC)之和。首先对ITD算法进行了改进;接着采用改进ITD算法对原始振动信号进行分解得到多个内禀尺度分量(Intrinsic scale component,简称ISC);然后对包含主要故障信息的若干内禀尺度分量建立对数正态分布模型,并提取其对数均值和对数标准差作为故障特征值;最后采用VPMCD模式识别方法得到各故障特征值的预测模型,并利用预测模型对待诊断样本的故障类型和工作状态进行分类和识别。对滚动轴承正常、外圈故障和内圈故障振动信号的分析结果表明了该方法的有效性。
基金Project(51175424) supported by the National Natural Science FoundationProject(B07050) supported by the 111 Project,ChinaProject (JC20110257) supported by the Basic Research Foundation of Northwestern Polytechnical University
文摘Carrying on a series of compression and shear tests by a large number of specimens, reliabilities of T300/QY8911 laminated composite were studied when dispersibility models were described. The results show that the stress is linearly dependent on the strain and the damage modes of specimens are brittle fracture for both kinds of tests. Dispersibility models of compression and shear strength are expressed as Re-N（415.39, 6 586.36） and Rs-ln（5.071 8, 0.155 3）, respectively. When normal and lognormal distributions were used to describe the dispersibility models of compression and shear strength, and the compression or shear load follows the normal distribution, the almost same failure probability can be obtained from different reliability analysis methods.
