磁悬浮运动演示仪

基于磁悬浮与电磁驱动原理研制了磁悬浮运动演示仪.该演示仪不仅可以演示磁悬浮运动,还可以开展多种相关实验探究.本文详细介绍了演示仪的设计与制作,并举例说明了利用该该仪器开展的探究活动.     

菱形开孔剪切钢板阻尼器的形状优化研究

矩形钢板阻尼器在剪力作用下耗能腹板各处受力不均匀,部分区域率先进入塑性而破坏,造成材料浪费甚至阻尼器延性欠佳。为使剪切钢板阻尼器充分发挥材料性能,可将矩形腹板开菱形孔,形成中部菱形孔钢板阻尼器,或两端去除半菱形,形成X型钢板阻尼器。然而,孔洞最优形状鲜有研究,而形状优化方法也很少提及。为了使菱形开孔剪切钢板阻尼器达到更好的滞回性能,对中部菱形孔和X型两种腹板开孔形式的阻尼器进行形状优化。在与试验结果验证的基础上,基于ABAQUS软件平台建立有限元分析模型,利用PYTHON语言开发了一种脚本优化方法,并与软件优化模块对比,分析优化前后的塑性分布和滞回耗能。结果表明,优化后最大塑性应变减小,塑性分布更均匀,利用脚本方法优化后的滞回曲线更饱满,耗能更好,为菱形开孔剪切型阻尼器的设计和优化提供了参考。     

Dynamics and control of an active pendulum system

The work focuses on autoparametric vibrations of system composed of a non-linear oscillator with an attached pendulum. A combination of semi-active damper together with a non-linear spring mounted in the suspension of system is proposed. The spring is made from a shape memory alloy (SMA) while damping is realized through a magnetorheological (MR) damper. The MR damper is used for controlling damping of the system, SMA spring is used to change system׳s stiffness. The system is solved numerically and verified experimentally on a custom made experimental rig. Specifically, non-linear resonances are investigated, and their influence on the system dynamics and absorption effect.     

一种新型防屈曲-分阶段耗能剪切型阻尼器及其性能分析

为解决传统剪切型金属阻尼器耗能形式单一,剪切腹板易过早发生局部屈曲的问题,设计了一种新型防屈曲-分阶段耗能剪切型阻尼器。该阻尼器主要由剪切腹板和防屈曲耗能件组成,防屈曲耗能件分布于剪切腹板两侧,上下两端与固定架相连。为考察其耗能和防屈曲能力,本文以传统的剪切型阻尼器试验模型为参考,利用ABAQUS有限元分析平台建立了14组阻尼器数值模型,分析了防屈曲耗能件的截面形状、使用材料的类型及与固定架间的连接方式等对阻尼器性能的影响,并采用刚度退化系数和等效黏滞阻尼比为评价参数衡量新型阻尼器的抗震性能。结果表明,设置了防屈曲耗能件的新型阻尼器其剪切腹板的最大面外位移与传统阻尼器的比值低于1/4,防屈曲耗能件与剪切腹板的最大屈服位移比超过3:1,可以有效防止剪切腹板过早发生屈曲,具备多阶段耗能的能力。相比于传统无防屈曲耗能件剪切型阻尼器,此类阻尼器耗能能力强、滞回性能稳定、具备较好的抗震性能,可以满足实际工程结构的抗震设计要求。     

A method to solve the efficiency-accuracy trade-off of multi-harmonic balance calculation of structures with friction contacts

The steady-state nonlinear forced response of systems with frictional damping can be computed in the frequency domain through the Harmonic Balance Method (HBM). A critical point is the selection of the number of harmonic terms used to represent the solution. In linear systems, this number is easily determined by the harmonic content of the forcing function (e.g. mono-harmonic). However, if nonlinearities are present, higher order harmonics may need to be included to ensure a proper representation of friction forces and displacements, with a detrimental effect on the computational time.The paper presents a novel method to solve the efficiency-accuracy trade-off of harmonic selection for nonlinear systems. This method warns the user whenever the number of retained harmonic terms is inadequate. As a result, it enables the user to run the simulation with a low number of retained harmonics, e.g. designers are typically interested in the first harmonic of the solution. The calculation is repeated with a larger harmonic support only when strictly necessary to keep the error below a user-defined threshold.The method is first compared to existing adaptive HBM techniques, highlighting its novel contributions. It is then carefully validated against high-order multi-harmonic calculations and against direct time integration. Its performance in terms of accuracy vs. computational time is highlighted. The method is then implemented in a state-of-the-art numerical tool for the design of underplatform dampers for turbine blades. Finally, its outcome is compared with experimental results.     

质量阻尼器的发展

广泛评述了调谐质量阻尼器(TMD)、多重调谐质量阻尼器(MTMD)、主动质量阻尼器(AMD)、半主动 TMD(SATMD)、主动调谐/主被动调谐/混合质量阻尼器(ATMD/APTMD/HMD)的研究现状.TMD, MTMD, AMD, SATMD, ATMD/APTMD/HMD能够有效地减小结构的风振与地震反应.指出强震下结构设置TMD, MTMD, AMD, SATMD, ATMD/APTMD/HMD的主要目的是限制结构屈服的进一步发展.因此,基于非线性结构模型的TMD, MTMD, AMD, SATMD, ATMD/APTMD/HMD研究具有重要意义.指出了TMD, MTMD, AMD, SATMD, ATMD/APTMD/HMD 有待于进一步研究的若干问题.提出了结构主动多重调谐质量阻尼器(AMTMD)和多重主被动调谐质量阻尼器(MAPTMD)的新控制策略.介绍了AMTMD和MAPTMD的研究进展并指出了进一步研究的发展方向.      

几何耦合对直升机桨叶液压减摆器等效线性阻尼的影响研究

建立了直升机前飞时,计入变距/挥舞/摆振几何耦合和力-速度非线性关系的液压减摆器分析模型;用4阶龙格-库塔法在时域内计算减摆器的轴向速度;根据减摆器轴向速度的瞬态响应成分,利用基于富里叶级数的移动矩形窗方法计算了减摆器等效线性阻尼。结果表明,存在变距/挥舞/摆振几何耦合的液压减摆器,在直升机前飞时其等效线性阻尼将大幅度下降。     

架空输电线防振锤安装位置的工程计算

防振锤被广泛用于架空输电线以耗散微风振动的能量,减轻微风振动的强度,保护架空输电线免受疲劳损害。根据架空输电线微风振动的特点,建立数值计算模型,通过计算振幅比,确定防振锤安装位置,供架空输电线微风振动防振设计和施工时参考。     

FREQUENCY-SHAPING LQR CONTROL OF WHOLE-SPACECRAFT VIBRATION ISOLATION PLATFORM BASED ON MR DAMPER1)

设计磁流变六杆隔振平台,以改善星箭界面低频振动环境.采用牛顿-欧拉法建立整星隔振平台动力学模型,利用固定界面模态综合法得到卫星和隔振平台动力学模型.由于星箭界面低频振动环境在特定频段存在振动量级较大的问题,采用频域加权LQR (linear quadratic regulator)方法,利用直接分解法扩展系统状态变量,进行磁流变阻尼器半主动控制系统设计.仿真结果表明,相对传统控制方法,频域加权LQR方法在特定频段减振效果明显改善,且在其他频段没有恶化,验证了算法有效性.     

Design of a higher harmonic cavity for the SSRF storage ring

Higher harmonic cavity used in the third generation synchrotron light source increases the Touschek lifetime.The higher harmonic cavity of Shanghai Synchrotron Radiation Facility(SSRF)is a 1.5 GHz passive superconducting cavity.Its higher order modes(HOM)are extracted by a ferrite HOM damper out of the cryostat.Multi-cell cavity is chosen concerning the voltage.The harmonic cavity dynamics,beam dynamics with passive harmonic cavity and the design of single cell cavity are included in this paper.