悬挂设备隔振频率与刚度优化分析

基于隔振原理,首先给出了系统频率避免共振需要满足的条件;其次,以E3C动车组牵引变压器冷却单元风机组为研究对象,建立了详细的有限元模型,通过对其进行模态分析得到变压器组装的刚体振动频率和冷却单元吊梁的弹性振动频率;然后,按照变压器组装的垂向浮沉振动、风机组的自身工作振动、冷却单元吊梁的垂向弹性振动对组合模型振动的影响依次降低的原则,研究了风机组避免与三种激励发生共振所需的悬挂频率与刚度;最后,通过避开三种激励的主共振区得到最优的风机组悬挂频率和风机组安装座减振橡胶刚度。

一种分时差分的频率调制MEMS加速度计

为提升MEMS加速度计温度适应性,设计了频率调制和分时差分方法。基于静电刚度效应,将敏感质量块因加速度产生的位移变化调制成谐振频率的变化,兼顾了位移检测的温度系数较低与谐振频率检测不易受电路噪声干扰的优点,且采用单个谐振器在时间上通过刚度切换进行分时差分,从而降低零偏随温度的漂移。通过实验测得,在10 V调谐电压下,加速度计室温下的零偏稳定性为76.79μg。-40℃~60℃全温范围内经过分时差分后得到的频差全温变化量为-0.072 Hz,相较于单个刚度状态下的谐振频率变化约7.7 Hz,减小了约99%,验证了静电刚度频率调制和分时差分的有效性。

动静刚度约束下客车骨架的轻量化设计

对由矩形管梁拼焊而成的客车骨架结构进行轻量化研究.首先计算了矩形管梁单元的截面特性,并定义了客车骨架的静态弯扭刚度响应与动态频率刚度响应.其次建立了客车结构优化数学模型:目标函数是车身骨架质量;设计变量是矩形管截面宽度、高度与厚度;约束是弯扭刚度与频率刚度.然后推导了响应对设计变量的灵敏度信息,并采用序列线性规划求解了该非线性优化模型.最后通过数值算例验证了该模型能在满足约束条件的前提下高效地获得轻量化的客车最优结构.

变载荷空气悬架固有频率的控制研究

从气体压缩的玻意耳定律出发,基于空气悬架的四个简化模型:忽略大气压力的无附加气室模型、考虑大气压力的无附加气室模型、忽略大气压力的有附加气室模型和综合考虑大气压力和附加气室的模型,采取循序渐进的方式探究空气弹簧的弹性特性、刚度特性和频率特性,推导出相关公式,并分析得到:有附加气室的空气悬架模型的固有频率要小于理想模型的固有频率、当空气弹簧的附加气室的容积一定时,悬架的固有频率随着气囊剩余空气柱的高度的增加而减小,与在实际工程上可通过设计体积可调的附加气室来实现悬架的固有频率的稳定,从而提高客货车的乘坐舒适性。

机载雷达驱动机构的刚度分析计算

天线驱动机构（又称天线座）作为雷达系统中的驱动单元，它的固有频率影响到天线座伺服带宽。以前对天线座固有频率的计算及分析很少考虑到驱动机构中运动副（轴承）对整个天线座刚度的影响，本文通过对某机载雷达天线座刚度的分析计算看到，轴承刚度对天线座固有频率产生的影响。

Dynamic simulation on rubber spring supporting equipment of vibrating screen

By ANSYS, dynamic simulation analysis of rubber spring supporting equipment used in vibrating screen was made. The modal frequency, mode, and harmonic displacement under working frequency were obtained. Variation of rubber spring supporting equipment＇s dynamic performance was discussed first, which is under the condition of existing spring stiffness difference and exciting force bias. Also, the quantitative calculation formulas were given. The results indicate that the performance of vibrating screen is closely related with rubber spring supporting equipment＇s dynamic performance. Differences of springs＇ stiffness coefficients reduce the modal frequency reduced, decrease the dynamic stiffness, and increase vibration displacement. Exciting force bias induces a larger lateral displacement. When rubber springs＇ stiffness coefficients exist, differences and lateral force accounts for 5% in total exciting force; rubber spring supporting equipment＇s side swing is larger than 1 mm, exceeding the side swing limit.

高度阀内置空气弹簧性能测试方法与分析

与普通空气弹簧不同,高度阀内置空气弹簧是将高度阀设置在空气弹簧气囊内部形成的一体式结构。由于其结构较特殊,目前还没有专门针对这种结构空气弹簧的性能测试方法。为了得到高度阀内置空气弹簧的性能测试方法,防止因测试方法不当造成高度阀内置空气弹簧的损坏,针对一款汽车驾驶室悬置高度阀内置空气弹簧进行了性能测试。测试参照普通空气弹簧的性能测试方法进行。测定了高度阀内置空气弹簧和外置高度阀的普通空气弹簧的载荷-位移曲线和动刚度-加载频率曲线。依据测试结果的对比分析可以发现:高度阀内置空气弹簧和普通空气弹簧性能曲线的变化趋势一致,而且所测定的曲线比较符合实际行车情况。说明参照普通空气弹簧的性能测试方法对高度阀内置空气弹簧进行性能测试是可行的。由此可知,高度阀内置空气弹簧与普通空气弹簧的性能测试方法具有一致性。

Surface Motion of Alluvial Valley in Layered Half-Space for Incident Plane P-Waves

The indirect boundary element method (IBEM) is used to study the surface motion of an alluvial valley in layered half-space for incident plane P-waves based on Wolf’s theory. Firstly, the free field response can be solved by the direct stiffness method, and the scattering wave response is calculated by Green’s functions of distributed loads acting on inclined lines in a layered half-space. The method is verified by comparing its results with literature and numerical analyses are performed by taking the amplification of incident plane P-waves by an alluvial valley in one soil layer resting on bedrock as an example. The results show that there exist distinct differences between the wave amplification by an alluvial valley embedded in layered half-space and that in homogeneous half-space and there is interaction between the valley and the soil layer. The amplitudes are relatively large when incident frequencies are close to the soil layer’s resonant frequencies.

弹性支承下弧齿锥齿轮实验台设计及其动态特性分析

现代航空发动机大多采用弹性支承,为了掌握弹性支承对弧齿锥齿轮传动的动态特性影响规律,需要开展弹性支承下弧齿锥齿轮的实验研究。设计并搭建了弧齿锥齿轮实验台,采用挠性套筒与刚性套筒相结合实现弹性支承刚度的连续变化,避免了拆卸转子造成的锥齿轮副安装位置的变化。建立了弹性支承下弧齿锥齿轮实验台的振动方程,并对齿轮副啮合刚度进行了数值计算,获得了啮合刚度的回归公式。针对不同外激励频率和支承刚度,计算了齿轮轴心振动位移和振动速度,得出在ω=2 300 Hz时主动齿轮振动最大的结论,为进一步的实验研究奠定了基础。

The Influence of Edge Restraining Stiffness on the Transverse Vibrations of Rectangular Plate Structures

This paper presents an analytical study on the influence of edge restraining stiffness on the transverse vibrations of rectangular plate structure. An improved Fourier series method was employed to analyze the transverse vibration of plate structure with general elastically restrained boundary conditions. A linear combination of a double Fourier series and eight auxiliary terms was sought as the admissible function of the flexural displacement of the plate, each term being a combination of a polynomial function and a single cosine series expansion. The auxiliary terms were introduced to ensure and improve the smoothness of the original displacement function and its derivatives at the boundaries. Several numerical examples were given to demonstrate the validity and accuracy of the current solution. The influences of translational and rotational stiffness on the natural frequencies and mode shapes of plate were analyzed by numerical results. The results show that the translational stiffness has bigger influence on the natural frequencies than the rotational stiffness. It is generally well known that little change of the rotational stiffness has little influence on the mode shapes of plate. However, the current work shows that a very little change of rotational stiffness value may lead to a large change of the mode shapes of a square plate structure.

Changes in Coupled Vibration Frequencies and Modes of Wall-Cavity Systems Induced by Stiffness Variation in the Structure

Problems of fluid structure interactions are governed by a set of fundamental parameters. This work aims at showing through simple examples the changes in natural vibration frequencies and mode shapes for wall-cavity systems when the structural rigidity is modified. Numerical results are constructed using ANSYS software with triangular finite elements for both the fluid （2D acoustic elements） and the solid （plane stress） domains. These former results are compared to proposed analytical expressions, showing an alternative benchmark tool for the analyst. Very rigid wall structures imply in frequencies and mode shapes almost identical to those achieved for an acoustic cavity with Neumann boundary condition at the interface. In this case, the wall behaves as rigid and fluid-structure system mode shapes are similar to those achieved for the uncoupled reservoir case.

Compromises in Vehicle Suspension Design

When designing vehicle suspension systems, compromises are usually made when setting the range of values for spring stiffness and damping constant. Suspension parameters are set depending on the operational requirements of the market. Passenger car for example, would require high quality damping while off road vehicle requires high spring stiffness setting. A quarter vehicle suspension model has been used to study the suspension transmissibility in handling and ride at various frequency ratios. The results obtained show that as the frequency ratio increases, transmissibility for handling reduces with increasing suspension stiffness and increases as the damping constant is increased. On the other hand, transmissibility for ride deteriorate as the spring constant is increased but approaches the ideal as the damping constant is increased. The dynamic magnification of the sprung masses reduces while that of the unsprung masses improves as the frequency ratio is increased.

牵引电机转子振动对高速列车动力学性能的影响

为了分析牵引电机转子振动对车辆动力学性能的影响,建立了包括驱动系统的动车非线性动力学模型,模型中考虑了转子-轴承系统的非线性力。通过数值仿真,研究了转子-轴承系统非线性反力对牵引电机振动的影响,对比分析了考虑与不考虑转子轴承非线性反力时车辆在驱动、匀速和惰行工况下的动力学特性。结果表明,电机转子的振动是由轴承变刚度频率及其次谐波频率振动引起的。轴承反力对电机、构架和轮对的垂向与纵向高频振动影响较大,横向振动以及车体振动影响较小。转子具有结构偏心时,这种影响更加明显。