共查询到18条相似文献,搜索用时 78 毫秒
1.
2.
3.
导电梁在磁场中的磁弹性随机振动 总被引:1,自引:1,他引:1
根据磁弹性基本理论和连续体的随机振动理论,得到了在外加磁场中通有随机电流的梁的磁弹性随机振动方程。给出了导电梁在耦合场中的洛伦兹力及力矩,并将洛沦兹力的耦合项假设为梁的一种阻尼,另一部分假设为随机分布载荷,对梁的位移响应进行了分析。以简支梁为例,分别得到了外加磁场中通入平稳和非平稳随机电流时简支梁的位移响应的均值、自相关函数、功率谱密度函数等数字特征。最后以一个通有理想白噪声平稳随机电流的简支梁为实际算例,对其位移响应的功率谱密度函数进行了计算。图形形状的改变表明了耦合项对梁的功率谱密度函数的影响,据此可知通过控制随机电流和磁场可以达到控制梁的随机振动的目的。 相似文献
4.
5.
6.
7.
8.
9.
10.
利用高灵敏度速度传感器,对上海光源实验大厅地基的随机振动进行了多点同步测量。数据分析结果表明上海光源实验大厅地基随机振动幅值具有周期变化的规律,且在低频区2 Hz~10 Hz具有较好的隔振效果。首次在上海光源大厅内进行随机振动中传递的相干规律的测试,测试表明在上海光源实验大厅中,距离为10 m的测试点在2.5 Hz以内的随机振动的互相关大于0.9;距离超过10 m时,两点随机偏差大于50 nm,超过随机振动RMS振幅的20%。随机振动传递规律的分析,对同步辐射光学元件的隔振设计有一定的指导作用。 相似文献
11.
Abstract: A ‘Go’ or ‘No Go’ assessment is a safety requirement for quick and robust estimation of the condition of gearboxes used in helicopters and other critical machines. A range of vibration‐based condition indicators (CIs) has been developed to meet this requirement. CIs are compared automatically with pre‐set threshold values representing a healthy system, so that the health of the gearbox can be assessed and diagnosis made where necessary. The use of kurtosis of the residual signal of the measured vibration data, computed as part of the ‘FM4’ method, is widespread, because it is accepted as a good and reliable indicator. However, it has been observed in some cases that FM4 may not show a continually increasing trend with the propagation of a fault. This behaviour may lead to improper assessment of the severity of the fault. Hence, a new CI, based on the deviation in the normal probability density function (PDF) of the measured vibration data, is suggested which demonstrates an increasing trend that is more robustly and monotonically correlated with the fault propagation. 相似文献
12.
运用概率统计的方法,对机械结构在阶跃干摩擦函数及二阶线性弹性函数作用下的振动数学模型进行分析,并给出汽车对应二阶线性弹性力的位移和加速度输出均方差,以便更合理地选择对汽车振动产生重要影响的某些参变量. 相似文献
13.
Majid Abedi 《先进材料力学与结构力学》2017,24(13):1124-1134
In this article, the exact probability density function for a nonlinear exponential functionally graded orthotropic plate under lateral random excitation is investigated. After that, a study on the probability density function (PDF) is done to examine the dynamic instability and bifurcation. Using nondimensional parameters, the results are justified for a wide range of plates. The outcomes are studied with respect to the variation of both mean value of lateral loads and in-plane forces. The famous Monte Carlo simulation is employed to validate the obtained analytical PDFs. An analogical study is done between the behaviors of homogenous plates with their corresponding functionally graded material ones. Finally, it is shown how the exponential profile functionally graded orthotropic material can affect the quality of instability and bifurcation. 相似文献
14.
针对电动振动台和数字式电动振动试验系统使用中的交越频率的定义及其推理过程加以阐述,探讨了影响电动振动台和数字式振动试验系统正确使用的因素及相关技术问题,同时针对检定规程中所规定的一些检定方法提出了值得商榷的看法,并给出相应的计算公式,供参考使用。 相似文献
15.
On the estimation of failure probability having prescribed statistical moments of first passage time
A method of estimating the probability density function and cumulative distribution function when only the ordinary or central moments of the distribution are known is examined. The technique is used in conjunction with previous work which yields the ordinary moments of time to first passage failure to obtain accurate estimates of the failure probability for two representative oscillators. The results are then compared to those obtained by a nearly exact numerical scheme. 相似文献
16.
《TEST》1982,33(2):47-63
This paper gives a formalization of the relation between the Debreu’s value function and the Von Neumann’s utility function,
with a generalization of this result for their respective vectorial functions. Finally the problem of incorporating complementary
information is consisdered.
相似文献
17.
Kurt Liffman Kanni Muniandy Martin Rhodes David Gutteridge Guy Metcalfe 《Granular Matter》2001,3(4):205-214
Metal disks of different size and density were placed at the bottom of a bed of monodisperse granular material. The system
was vibrated sinusoidally in the vertical direction. It was observed that, if the angular acceleration of the shaking was
slightly greater than that of gravity, the metal disks rose to the top of the bed. This result has been known for over sixty
years, but a basic understanding of the mechanism responsible for the rise of the disks is still a subject of debate. Our
experiments and theoretical model show that the ascent speed of the disk is proportional to the square root of the disk density,
approximately proportional to the disk size, and is a function of the disk's depth in the bed. We also investigated the speed
of ascent of the disk as a function of the shaking frequency, f
s
. We found that the effective friction or drag coefficient, β, between the disk and the granular bed, is proportional to a
functional form of the frequency: β∝ (f
s
−f
c
)−4, where f
c
is the critical shaking frequency for the disk to start moving through the bed. We discuss how such a dependency may arise.
Received: 28 August 2000 相似文献
18.
针对某高分辨率空间相机结构随机振动加速度响应大的问题,对空间相机支撑结构进行了优化设计。(1)建立了基于随机振动响应分析的数学模型,推导了随机振动均方根响应表达式;(2)基于三点定位原理和双脚架柔性结构原理设计了相机支撑结构,以相机安装点RMS值最小为目标,基频作为约束,建立了相机支撑结构随机响应优化模型,对支撑结构柔性环节位置进行了尺寸优化设计,采用MSC.PatranNastran有限元分析软件对优化处理后的支撑结构进行了工程分析,相机安装点随机响应RMS值最大19.6 grms;(3)对相机支撑结构进行了随机振动试试验。结果显示:有限元分析结果与试验测量数据符合的较好,最大相对误差为8.2%,所设计的空间相机支撑结构满足空间相机使用要求,验证了所采用优化方法的可行性。 相似文献