动力总成悬置支架拓扑优化研究

采用结构拓扑优化方法,对动力总成悬置支架进行了优化.在最优拓扑结构的基础上进行结构修改后,一阶固有频率明显提高,而重量有所减小.从加强筋的优化结果来看,在平行于一阶弯曲振型方向上布置加强筋,可获得较好的效果.研究表明,在产品的概念设计阶段采用拓扑优化方法,能给产品的详细设计提供一个很好的基础.     

一种内旁通道阀式磁流变液悬置结构原理与试验研究

理想的动力总成悬置在低频高幅值激励下应具有大刚度大阻尼、在高频低幅值激励下小刚度小阻尼特性.针对现有磁流变液悬置的动刚度可控范围低、零场动刚度大及工作行程有限等问题,本文提出并实现了一种在全工作频率范围内具有较大动刚度范围、较小零场动刚度和最大化工作行程的磁流变液悬置,即内旁通道阀式磁流变液悬置.利用有限元仿真软件对该磁流变液悬置进行了电磁场仿真分析.建立了该磁流变液悬置的可控阻尼力数学模型,并基于搭建的伺服液压作动系统进行了磁流变液悬置阻尼力可控性能试验.     

电动车辆驾驶室隔振系统建模与振动特性分析

针对电动车辆驾驶室的低频振动问题,首先建立了底部装有4个隔振器的驾驶室有限元模型,提出采用三个方向的非线性弹簧阻尼单元的方法来等效替代隔振器,并进行约束模态分析.根据模态分析结果,讨论了驾驶室晃动产生的原因,并在此基础上,给出了两种减小驾驶室晃动的隔振器设计改进方法.根据实际使用情况,对液阻型橡胶隔振器进行了设计和静力分析,改善驾驶室的乘坐舒适性,此外通过调整隔振器的安装位置有效地减轻驾驶室的振动,模态分析结果显示振型频率均有所提高,同时第4阶振型变为驾驶室后壁局部振动.最后,利用有限元仿真,对驾驶室隔振系统进行振动分析,结果表明调整隔振器安装位置后的驾驶室减振系统在低频路面位移激励下垂向振幅明显减小.     

Improving signal-to-noise ratio for the forensic analysis of glass using micro X-ray fluorescence spectrometry

Micro X-ray fluorescence spectrometry (μXRF) is a standard technique used for the elemental analysis of glass fragments in forensic casework. The glass specimens encountered in casework are usually small (<1 mm), thin fragments that are partially transparent to the exciting X-ray beam. In addition to providing fluorescence from the small glass fragments, the primary beam X-rays can scatter within the chamber and provide noise in the measurements. To reduce scatter from the sample stage, the fragments are typically mounted on a thin plastic film and raised on an XRF sample cup (≤3 cm in height). However, at these heights, there may still be significant scatter from the sample stage, which adversely affects the signal-to-noise ratio (SNR) and the limit of detection (LOD). A plastic mount was designed and 3D-printed in-house to allow fragments to be raised as high as possible from the sample stage, thereby minimizing stage scatter. Most elements detected in glass showed an improvement in the SNR when using the 3D-printed mount for analyses. The greatest improvement (>30%) was observed for lower atomic number elements (Na and Mg) and higher atomic number elements (Sr and Zr). Another simple method to improve SNR is the use of primary beam filters; when using primary beam filters during analyses, elements with characteristic lines in the high-energy range (Rb, Sr, and Zr) showed the greatest improvement (>70%) in SNR. The impact of both strategies for the improvement of SNR is presented here.     

利用加速度反馈的大型光电设备主轴控制技术

随着光电跟踪设备的大型化,在系统的惯量增大的同时,机械谐振频率一般会降低,此时控制系统的带宽设计将受到限制,而且大型的光电设备更容易受到风阻、地基振动等各种干扰的影响,从而降低系统的控制精度。由于惯性测量元件——加速度计直接感受被测对象的受力情况,通过引入加速度反馈控制回路,在不增大系统带宽的前提下,中低频段的扰动抑制传递函数幅值下降约25 dB。理论、仿真和实验三方面均验证了该控制方式的有效性。     

广东南岭国家级自然保护区鸟类群落的研究

对广东省南岭国家级自然保护区鸟类群落、特点进行了研究．南岭国家级自然保护区有鸟类２１７种，隶属１７目、４１科．根据南岭山地植被的垂直分布，鸟类的垂直地理分布可分为５个带：①农耕区植被带（海拔２００ｍ以下）；②低山常绿阔叶林带（海拔２００～８００ｍ）；③中山山地常绿阔叶落叶混交林带（海拔８００～１４００ｍ）；④高山亚热带山地常绿针阔混交林带（海拔１４００～１７００ｍ）；⑤山顶亚热带常绿阔叶苔藓矮林带（海拔１７００ｍ以上）．     

弹性三脚架的模态试验研究

本文探讨了机枪弹性三脚架模态试验研究的基本方法.经试验获得了某重机枪弹性三脚架在不同状态、不同方向的固有特性参数.     

磁流变液可控多流道悬置隔振性能仿真分析

设计一种动刚度和阻尼可调的磁流变液可控多流道悬置.首先,建立多惯性通道液压悬置模型,数值仿真不同的流道数量对悬置动刚度和滞后角的影响;然后,建立磁流变液可控多流道悬置模型,通过实验验证可控多流道可以控制流道的开闭;最后,分析磁流变液可控多流道悬置不同流道开闭的动态特性变化.结果表明:对不同的流道分别施加磁场作用可使悬置的动刚度、阻尼可调和力的传递率最小;已知激励频率,根据可控区域实时控制流道数量,可获得最佳隔振性能.     

Constitutive computational modelling foundation of piezoelectronic microstructures and application to high-frequency microchip DSAW resonators

This paper establishes a piezoelectric constitutive computational approach based on generalized eigenvalue and multivariable finite element solutions with potential applications to accurate and effective analysis of layered piezoelectric microstructures of arbitrary geometries and different anisotropic materials, to ease the limitation of current computer capacity in analyzing large-scale high-frequency disturbed surface acoustic waves (DSAW) by mounted electrodes in piezoelectric devices such as microchip SAW resonators. A new incompatible generalized hybrid/mixed element GQM5 is also proposed for improving predictions of the piezoelectric surface mount thermal stresses that are shear-dominated. The (generalized) plane strain constitutive model is numerically verified for piezoelectric finite element computation. With the help of computational piezoelectricity (electro-mechanics) for general layered structures with metal electrodes and anisotropic piezoelectric substrates, some new interesting, reliable and fundamental constitutive finite element results are obtained for high-frequency piezoelectric and mechanical SAW propagations and can be used for further applications. The ST-cut FEA results agree quite well with available exact and lab solutions for free surface case. The project supported by SRF for ROCS, SEM of China, the past Rutgers Univer-Seiko Epson Joint Fund and Zhejiang Provincial NSF     

应用于汽车发动机start/stop模式的磁流变悬置设计与分析

针对汽车在start/stop模式下发动机传递至车身的振动和扭矩过大问题,设计了一种具有惯性通道的流动模式磁流变悬置.在考虑了激励电流对磁流变液黏度的影响规律和悬置液阻效应的基础上,建立悬置的阻尼力数学模型.采用有限元软件分析了在励磁线圈作用下磁流变悬置磁路阻尼通道处的磁感应强度分布规律,分析了激励电流和磁路的结构参数对悬置恢复力和可控力的影响规律.并对磁流变悬置进行了性能测试和start/stop模式下的实车试验.结果表明,所设计的磁流变悬置具有良好的可控性,并且能有效地隔离汽车发动机在start/stop模式下的振动传递.