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汽车车架结构振动应变分析的模态法 总被引:2,自引:0,他引:2
根据在同一激振力的作用下用模态叠加法来表达位移响应和应变响应时,二者具有相同坐标的物理概念,先用位移模态分析法求取了模态质量、模态刚度、模态阻尼以及位移模态振型等模态参数。而后用共振法激发应变模态振型、增大应变量,以改善电阻应变计的测量精度,求取高精度的应变模态。这一方法用于车架的应变模态分析,取得了可靠的实验结果,并揭示了局部应力集中现象。 相似文献
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本文分析了非完整模态集振型叠加法应用于系统自由振动、受迫振动和冲击响应计算及实验模态分析中时的条件,有助于正确认识和应用模态截断的概念和方法。 相似文献
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伊立言 《振动、测试与诊断》1985,(4)
本文提出了用电阻应变片测量振动响应,用于弹性结构作模态分析的理论和方法。文中提出应变导纳的概念,建立了应变和振动位移关系,推导出在振动系统中用应变量表示传递函数公式。采用本文所述的方法可以识别出振动系统的固有频率,位移振型、应变振型、阻尼等模态参数以及主应力,主应力方向等。它可用在正弦试验,随机试验和冲击试验。本文通过锤击法试验从实践上验证了应变片测响应的实用性。文中也作了正弦试验和计算。三者相互比较,结果相当一致。 相似文献
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自然激励技术的提出为大型复杂工程结构环境激励下的模态提取提供了一条新的途径,但对于单输入的情况存在以下问题:白噪声激励下结构系统位移响应的互相关函数公式中的相位角和幅值缺乏解析表达式;当动力荷载恰好作用在系统某阶振型的节点时可能出现的现象缺乏分析和物理解释.发展了单输入自然激励技术,推导了白噪声激励下结构位移响应的互相关函数,给出了其中相位角和幅值的解析表达.研究发现,当单输入动力荷载恰好作用在系统某阶位移模态的节点时,任意两自由度位移响应的互相关函数中将不含有频率值等于该阶模态有阻尼固有频率的简谐成分,即该阶模态的信息在互相关函数中得不到反映. 相似文献
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为提高舰载设备的抗冲击性能,改善传统限位器产生的二次冲击问题,提出采用液压限位器代替传统橡胶限位器方法.首先建立基于AMESim的液压限位隔离系统计算模型,分析了阻尼孔孔径对隔离系统冲击响应的影响,然后对比分析了液压限位和橡胶隔离系统的冲击响应特性,最后通过冲击试验加以验证.研究结果表明:对于任一额定负载下的液压缓冲器,都存在一个最优阻尼孔孔径,使隔离系统获得最佳隔冲效果;与橡胶限位隔离系统相比,在相对位移响应一致的条件下,不仅加速度响应峰值降低了65%以上,而且保证了加速度隔冲率在45%以上,有效改善了二次冲击带来的危害,大幅提高了舰载设备的抗冲击性能. 相似文献
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基于三维CAD模型建立了某航空电子设备PCB组件的有限元仿真模型。通过有限元模态分析结果与实验模态分析结果的对比,验证了有限元模型的正确性。在此基础上进行了3种不同阻尼设置下的随机振动分析,并进行了实物的随机振动实验。分别比较了仿真和实验得到的均方根(RMS)值和功率谱密度(PSD)响应。最后得出结论:常数阻尼比0.01并叠加模态阻尼时的仿真结果与实验数据最接近;模态分析时应覆盖激励谱的全部频率。 相似文献
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高速铁道客车车体受轨道激扰力的作用产生弹性振动,影响客车运行平稳性。为了分析车体弹性振动与车体悬挂参数关系,基于刚柔耦合动力学原理,建立了客车垂向动力学模型,根据共振理论及模态叠加原理计算了系统固有频率和响应功率谱,分析了车辆系统悬挂参数和运行参数对振动的影响。仿真发现弹性车体振动响应大于刚性车体,车体一阶垂弯振动对弹性振动的贡献最大。在满足结构条件下,适当降低一、二系悬挂垂向阻尼、一系悬挂垂向刚度可减小车体弹性共振,系统各个部件自振频率控制、车体垂向悬挂阻尼控制可实现整车模态及局部有害模态控制。 相似文献
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文中针对某机载雷达天馈伺系统,进行使用环境下的随机振动分析。首先建立天馈伺系统的有限元模型,进行模态分析,得到系统的固有频率和对应振型,然后采用模态叠加法计算系统在随机激励试验谱线作用下的应力、位移响应,最后对结构的强度进行校核并提出结构改进的方向。分析结果表明,该天馈伺系统可以满足产品的使用环境要求并具有一定的安全余量。 相似文献
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Seongsoo Lee Hyungsoo Mok Chang-Wan Kim 《Journal of Mechanical Science and Technology》2011,25(12):3115-3121
The component mode synthesis (CMS) method on multi-level, called as recursive component mode synthesis (RCMS) method, is implemented
for the free vibration analysis of a vehicle system supported on damper-controlled spring-stiffness suspension. The nonproportional
damping is considered to describe the suspension system. The focus of the RCMS method is the out-of-core concept that uses
disk space rather than memory when computing large scale vehicle FE models. After the eigensolutions are obtained, the mode
superposition method is used to compute the dynamic response in the frequency domain. The proposed method can deal with a
damped structural system with a general damping system. The performance and accuracy of the proposed method compared to the
Lanczos method are demonstrated through an example FE model. 相似文献
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An analytical approach for vibration damping analysis of beams with partial passive constrained layer damping (PCLD) treatments is extended to the case where the structure is covered by multiple patches. The energy-based approach and assumed-mode method are used to derive the equations governing the vibration displacement responses of the system, which is characterized in terms of the identical transverse displacement of all layers, and the longitudinal displacements of the base beam and the constraining layers. Furthermore, the longitudinal displacements of the base beam and constraining layer are independent of each other, which is in contrast to Kerwin's weak core assumption. The direct frequency response method is employed to determine the modal loss factors of the damped beam in a frequency range of interest. A convergence study is made on the damped beam to determine appropriate numbers of the mode functions for frequency response function (FRF) calculations. Parametric studies are performed with the established analytical approach and the determined numbers of mode functions to study the effects of dividing a PCLD patch into two pieces in different length ratios and also the spacing between the patches on the damping performance of a simply supported beam. 相似文献
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桥面不平引起车桥系统随机振动车速因素分析 总被引:1,自引:0,他引:1
将桥梁离散为梁单元,车辆简化为两自由度系统,桥面不平顺引起的车桥耦合振动荷载等效为虚拟激励荷载,建立移动车辆-桥梁耦合随机振动模型,运用虚拟激励法((pseudo excitation method,简称PEM)并结合模态综合叠加技术进行求解。将数值迭代结果与Monte-Carlo法对比,验证求解算法的正确性。以简支梁桥为例,在频域内对桥面不平顺引起车桥耦合随机振动的车速因素进行分析。结果表明:桥梁跨中竖向位移均方根值随车速变化较大,车速对位移和加速度功率谱曲线的1阶频率峰值和带宽影响显著;近支点加速度功率谱曲线的峰值、频率及带宽随车速变化明显。研究桥面不平顺引起的车桥耦合随机响应,车速对桥梁和车体振动影响不可忽略。 相似文献
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Nobuhiko Henmi Yuta Sumi Michihiko Tanaka 《Journal of Mechanical Science and Technology》2010,24(1):211-214
A displacement magnification mechanism which uses flexure motion guide using elastic hinges can realize smooth frictionless
motion but has poor vibration damping capability. An impact damper is a damping mechanism which uses collision energy to dissipate
vibration energy. If the damper is used for vibration control of the flexure mechanism, it may be able to dissipate unexpected
vibration without killing the merits of the flexure mechanism. In the paper, a loading type impact damper is applied to settle
down transient vibration of a displacement magnification mechanism. We investigate differences of damping effect by setting
conditions of the damper. It is shown that the impact damper can eliminate residual vibration at step response effectively
without steady state error. The experimental displacement magnification mechanism with impact damper can settle down less
than 1/5 of the response without the damper under appropriate setting conditions. Influence of natural frequency ratio between
damper and displacement magnification mechanism is investigated. Influences of indentation at impact point are also examined. 相似文献
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基于准定常假定,采用谐波叠加法仿真集装箱起重机的脉动风场并对其进行脉动风载作用下的抖振响应分析。风场仿真结果表明,除自谱的低频误差较大外,风速样本的功率谱密度与目标值完全一致。岸桥前梁端点的位移响应谱表明,低频的脉动风载荷对岸桥的基频模态具有最强的激振效应,且紊流风作用下岸桥前梁端点顺风向抖振最大位移高达53mm,可能会激起梁上小车与轨道的耦合振动,影响梁上电动小车行驶安全性,而横向和竖向脉动风下的振动位移很小,可忽略不计。 相似文献
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Optimization of secondary suspension of piecewise linear vibration isolation systems 总被引:1,自引:0,他引:1
Sagar Deshpande Sudhir Mehta G. Nakhaie Jazar 《International Journal of Mechanical Sciences》2006,48(4):341-377
A comprehensive optimal design solution is presented for piecewise-linear vibration isolation systems. First, primary suspension optimum parameters are established, followed by an investigation of jump-avoidance conditions for the secondary suspension. Within the no-jump zones, an optimal design solution is then obtained for the secondary system and overall results are discussed.Averaging method is employed to obtain an implicit function for frequency response of a bilinear system under steady-state conditions. This function is examined for jump-avoidance and a condition is derived which when met ensures that the undesirable phenomenon of ‘jump’ does not occur and the system response is functional and unique. Optimal stiffness and damping parameters for the primary suspension are extracted from a recently established work for passive linear vibration systems. For each point of the primary suspension optimal curve, jump-free zones are identified. Iterating this process, a boundary surface between no-jump (unique response) and jump (multiple-response) areas is established. Keeping optimal parameters for the primary suspension system fixed, the secondary suspension stiffness and damping parameters are varied inside the no-jump zones to explore optimum solutions for the secondary.The root mean square (RMS) of the absolute acceleration is minimized against the RMS of the relative displacement (η). It is observed that there is a certain band of parameters defined by primary damping, within which a valid frequency response can be obtained. An optimum numerical solution is sought within this band of parameters. Optimal solution curves are achieved for the secondary suspension. These can be used in conjunction with the optimal curve for the primary suspension to select design parameter values for the best possible vibration isolation performance in a given application. 相似文献