Nonlinear Static and Dynamic Stiffness Characteristics of Support Hydraulic System of TBM

Full-face hard rock tunnel boring machines(TBM)are essential equipment in highway and railway tunnel engineering construction.During the tunneling process,TBM have serious vibrations,which can damage some of its key components.The support system,an important part of TBM,is one path through which vibrational energy from the cutter head is transmitted.To reduce the vibration of support systems of TBM during the excavation process,based on the structural features of the support hydraulic system,a nonlinear dynamical model of support hydraulic systems of TBM is established.The influences of the component structure parameters and operating conditions parameters on the stiffness characteristics of the support hydraulic system are analyzed.The analysis results indicate that the static stiffness of the support hydraulic system consists of an increase stage,stable stage and decrease stage.The static stiffness value increases with an increase in the clearances.The pre-compression length of the spring in the relief valve a ects the range of the stable stage of the static stiffness,and it does not a ect the static stiffness value.The dynamic stiffness of the support hydraulic system consists of a U-shape and reverse U-shape.The bottom value of the U-shape increases with the amplitude and frequency of the external force acting on the cylinder body,however,the top value of the reverse U-shape remains constant.This study instructs how to design the support hydraulic system of TBM.

Performance analysis of high-static-low-dynamic stiffness vibration isolator with time-delayed displacement feedback

The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly analyzed from the viewpoint of equivalent damping. Firstly, the primary resonance of the controlled HSLDS vibration isolator subjected to a harmonic force excitation is obtained based on the multiple scales method and further verified by numerical integration. The stability of the primary resonance is subsequently investigated. Then, the equivalent damping is defined to study the effects of feedback gain and time delay on primary resonance. The condition of jump avoidance is obtained with the purpose of eliminating the adverse effects induced by jumps. Finally, the force transmissibility of the controlled HSLDS vibration isolator is defined to evaluate its isolation performance. It is shown that an appropriate choice of feedback parameters can effectively suppress the force transmissibility in resonant region and reduce the resonance frequency. Furthermore, a wider vibration isolation frequency bandwidth can be achieved compared to the passive HSLDS vibration isolator.

Low frequency vibration control of railway vehicles based on ahigh static low dynamic stiffness dynamic vibration absorber

In order to control the low frequency vibration of railway vehicles, a vertical two degrees of freedom(2DOF) low frequency dynamic vibration absorber(DVA) based on acceleration is proposed. Parameters of the dynamic vibration absorber are put forth to control the low frequency vibration of car body bouncing and pitching. Next, the acceleration power spectrum density(PSD)and ride quality of the car body are calculated based on the pseudo excitation method(PEM) and covariance algorithm,respectively. According to the requirement of 2DOF low frequency DVA, the isolators with high static low dynamic stiffness(HSLDS) are designed. A high-speed train dynamic model containing HSLDS isolators is established to validate the effects on the car body vibration. The results reveal that the 2D low frequency DVA can significantly reduce the vibration of the car body bouncing and pitching. Thus, the ride quality of the vehicle is increased, and passenger comfort is improved.

Characterization of an Electromagnetic Vibration Isolator

A novel vibration isolator is constructed by connecting a mechanical spring in parallel with a magnetic spring in order to achieve the property of high-static-low-dynamic stiffness (HSLDS). The HSLDS property of the isolator can be tuned off-line or on-line. This study focuses on the characterization of the isolator using a finite element based package. Firstly using the single physics solver, the stiffness behaviours of the mechanical and magnetic springs are determined, respectively. Then using the weakly coupled multi-physics method, the stiffness behaviours of the passive isolator and the semi-active isolator are investigated, respectively. With the found stiffness models, a nonlinear differential equation governing the dynamics of the isolator is solved using the time-dependent solver. The displacement transmissibility ratios of the isolator are obtained. The study confirms that the isolation region of the isolator can be widened through off-line or on-line tuning.

Dynamic Analysis of a Single-Column Platform

In this paper, a single-column structure used as well-head platform is studied. The loads of wave and current exerted on the single-column will be greatly reduced, therefore the cost of the structure will be decreased. The advantages of the single-column structure compared with ordinary jacket structure are explained. A dynamic analysis of this type of structure is made and some problems related to dynamic analysis are solved. In order to check the reliability of computation theory and programme, model tests have been carried out. However, as space is limited, the conclusion of tests will be introduced in another paper. Therefore, this type of structure is applicable for proctical engineering.

High-static-low-dynamic-stiffness vibration isolation enhanced by damping nonlinearity

High-static-low-dynamic-stiffness(HSLDS) nonlinear isolators have proven to have an advantage over linear isolators, because HSLDS nonlinear isolators allow low-frequency vibration isolation without compromising the static stiffness. Previously, these isolators have generally been assumed to have linear viscous damping, degrading the performance of the isolator at high frequencies. An alternative is to use nonlinear damping, where the nonlinear behavior is achieved by configuring linear dampers so they are orthogonally aligned to the excitation direction. This report compares the performances of single-stage and two-stage isolators with this type of damping with the corresponding isolators containing only linear viscous damping. The results show that both isolators with linear viscous damping and nonlinear damping reduce the transmissibility around the resonance frequencies, but the results show that the isolators with nonlinear damping perform better at high frequencies.

丁苯橡胶发泡材料的制备和性能研究

研究白炭黑用量、硫黄/过氧化物BIBP并用硫化体系的过氧化物BIBP和助交联剂TAIC用量、发泡倍率、预硫化温度和预硫化时间对丁苯橡胶(SBR)发泡材料性能的影响。结果表明:白炭黑用量增大,SBR发泡材料的100%定伸应力、拉伸强度、静刚度和动静刚度比增大,拉断伸长率减小;随着过氧化物BIBP用量和助交联剂TAIC用量增大,SBR发泡材料的拉伸强度、拉断伸长率、压缩永久变形和动静刚度比减小,100%定伸应力和静刚度增大;随着发泡倍率增大,SBR发泡材料的静刚度减小,动静刚度比增大;预硫化温度为125℃和预硫化时间为16 min时,SBR发泡材料的减振性能最佳,此时泡孔直径较小及分布均匀。

Evaluation of the fishbone model in simulating the seismic response of multistory reinforced concrete moment-resisting frames

The fishbone model is a simplified numerical model for moment-resisting frames that is capable of modelling the effects of column-beam strength and stiffness ratios. The applicability of the fishbone model in simulating the seismic responses of reinforced concrete moment-resisting frames of different sets of column-beam strength and stiffness ratios are evaluated through nonlinear static, dynamic and incremental dynamic analysis on six prototype buildings of 4-, 8-and 12-stories. The results show that the fishbone model is practically accurate enough for reinforced concrete frames, although the assumption of equal joint rotation does not hold in all cases. In addition to the ground motion characteristics and the number of stories in the structures, the accuracy of the model also varies with the column-beam stiffness and strength ratios. The model performs better for strong column-weak beam frames, in which the lateral drift patterns are better controlled by the continuous stiffness provided by the strong columns. When the inelastic deformation is large, the accuracy of the model may be subjected to large record-to-record variability. This is especially the case for frames of weak columns.

Elastic stability of shallow pin-ended parabolic arches subjected to step loads

Buckling could be induced when shallow arches were subjected to vertical step loads. In-plane static and dynamic buckling of shallow pin-ended parabolic arches with a horizontal cable was investigated. Based on the equations of motion derived from Hamilton's principle, nonlinear equilibrium equations and static buckling equilibrium equations were deduced. Through the pseudo-static analysis, approximate solutions to the lower and upper dynamic buckling loads under step loads were obtained, for shallow parabolic arches. The results show that dynamic buckling and snap-through buckling are impossible when modified slenderness ratio λ<λc and λ>λs, where λc and λs denote critical slenderness ratios of bucking and snap-through buckling, respectively; effects of the stiffness of the horizontal cable on the dynamic buckling are significant; and the dynamic buckling loads under a equivalent central concentrated step load are lower than the loads under a distributed load appreciably.

基于管柱动力学的特深井通井组合刚度评价方法与应用

我国特深井钻井正处于快速发展阶段,受井眼尺寸大和深度深的影响,钻井过程中极易出现微井斜、扩径缩径和井壁台阶等,导致套管下入困难,因此通井钻具组合评价尤为重要。目前,现场使用的评价方法常忽略了管柱下入过程中与井壁的碰撞和变形,导致通井效果时好时坏。为了辅助现场施工,文章基于全井管柱动力学模型和HHT-α数值计算方法提出了一种能够模拟管柱下入的动态过程的通井钻具组合的评价方法,该方法考虑了实测井眼轨迹、井眼扩大率和下入阻力等要素。通过某特深井三开下套管前的钻具组合进行实例计算分析,表明井眼扩大率和套管串下入阻力对通井能力和套管下入影响较大,当井眼扩大率较小且套管串下入阻力较大时,需要使用刚度较大的多扶正器通井钻具组合。本方法可以实现实测井况条件下比较精准的刚度对比模拟,也成功指导了案例井?486 mm套管的安全下入。

低频大幅隔振器设计及实验

为了突破传统隔振器刚度和承载能力之间的矛盾,需要隔振器具有高的静态刚度,低动态刚度的特性.如今的准零刚度隔振器技术可以实现低频微幅隔振,但是对于大幅振动,隔振效果并不明显甚至失效,因此突破宽幅隔振成为隔振领域亟待解决的问题.为此,我们利用多稳态折纸通过并联装配的方式,构造具有宽幅零刚度区间的折纸型隔振器,以解决传统隔振器振动抑制幅值较低的问题.本文建立了宽零刚度隔振器模型,提出宽幅零刚度的设计方法,并通过动力学分析分析了模型的隔振效果.最后搭建试验样机,验证了理论的正确性.这种设计打破了传统准零刚度隔振器单点准零的设计准则,能够在一个大幅范围内保证稳定性,同时实现零刚度,极大拓宽了隔振器的适用范围.这种设计理念能够被用在新隔振材料设计和航空、船舶等大幅低频动态环境中.

一种小动静比橡胶隔振器仿真与试验

通过隔振器内部结构设计,在保证承载能力的同时降低橡胶隔振器的动态刚度。开展橡胶隔振器的静态变形、在给定静变形下的动态仿真分析,表明该隔振器在静态力-位移曲线上具有负斜率特性,对应隔振器内部结构的失稳变形;进行隔振器的静压试验、动态试验和隔振系统中的振动传递试验,结果表明,静态力-位移曲线试验结果呈现负斜率特性,在静态曲线上不同工作点处的固有频率呈现负斜率处最小的特性。

一种电磁式高静-低动刚度隔振系统建模与特性分析

为改善传统线性隔振系统尺寸参数确定后就无法取得更低起始隔振频率的缺陷,基于电磁线圈嵌套永磁体结构,提出一种具有高静-低动刚度特性的电磁式可变刚度隔振系统.采用分子电流法建立隔振系统磁力的数学模型;充分考虑隔振系统力学模型中二次与三次非线性刚度项的影响,建立单自由度被动隔振系统强非线性动力学模型;采用增量谐波平衡法(IHB)求解动力学模型,分析激励、电流等对隔振系统位移传递率的影响规律;构建实验测试系统,验证所提出新型隔振系统的有效性.实验结果和理论计算表明:通入电流比未通入电流时隔振系统的起始隔振频率降低了19.25%,拓宽了隔振频带,实现了其对不同振源的适应性.

用于夹层梁静动力及屈曲分析的新型组合结构单元

推导出新型组合结构单元,用于考虑界面滑移的3层部分作用夹层组合梁的静动力及屈曲特性分析.基于铁木辛柯梁理论,建立考虑夹层梁部分作用效应的能量原理.针对其受力特性,在节点位移、横截面转角和界面滑移插值时均采用含内部自由度的高阶插值函数,以解决含界面有限元数值分析中常遇到的“滑移锁定”现象.通过变分原理得到夹层梁的刚度矩阵、质量矩阵以及几何刚度矩阵的显示表达式.基于MATLAB编译相应夹层结构的有限元程序并验证其准确性.对不同截面3层夹层组合梁进行不同荷载条件和边界条件下的静动力及屈曲特性分析,并探讨不同夹层组合梁跨高比和不同界面抗剪连接刚度下的计算结果及其误差的变化规律.所推导的显示表达式新型组合结构单元计算效率高,并便于推广应用于其他有限元程序或商业软件子程序中.

一种双简支―悬臂梁反共振隔振器设计分析与试验

[目的]为探究三元件型反共振隔振器的实现形式,提出一种由一根悬臂端含质量块的双简支-悬臂梁与一根双支撑梁所组成的机械装置(BAVI)。[方法]首先,分析双简支-悬臂梁的动态特性,推导其阻抗方程;然后,根据驱动点阻抗函数综合其低阶模型是单惯容与单弹簧二元件的串联结构,并解析低阶模型的等效参数;最后,通过装置试件设计与试验,验证其反共振特性和理论方法有效性,并在此基础上分析装置刚度特性及不同阻尼形式的效果。[结果]结果表明,当跨度比共振隔振器结构,具有“高静低动”刚度特性;在双简支-悬臂梁上采取阻尼措施后,可实现隔振区传递率以最大速率衰减的同时抑制共振峰的效果。[结论]所提机械装置证明了三元件型反共振隔振器的可实现性,提供了一种简易可行的工程结构。

炭黑N330用量对天然橡胶阻尼性能的影响

研究炭黑N330用量对天然橡胶(NR)阻尼性能的影响。结果表明:随着炭黑用量的增大,NR混炼胶的FL,Fmax和Fmax-FL增大,t90缩短;NR硫化胶的邵尔A型硬度、100%定伸应力、300%定伸应力、拉伸强度和撕裂强度增大,拉断伸长率和回弹值减小;NR硫化胶低温下的损耗因子(tanδ)峰值减小,高温下的tanδ呈增大趋势。随着温度的升高,NR硫化胶的tanδ减小,且炭黑N330用量大的NR硫化胶的tanδ减小速率大于炭黑N330用量小的NR硫化胶,表明高温下炭黑N330用量大的NR硫化胶的阻尼性能对温度变化更敏感。随着炭黑N330用量的增大,NR硫化胶的静刚度和动/静刚度比都增大,表明炭黑N330用量增大对NR硫化胶的阻尼性能有提升作用。

Ti-6Al-4V六槽深浅腔动静压轴承刚度数值分析

针对传统材料制造的动静压轴承刚度较差的问题,提出一种基于Ti-6Al-4V材料制造六槽深浅腔交错分布的动静压轴承。利用ANSYS有限元软件建立六槽深浅腔动静压轴承流固耦合模型,研究轴径间隙、转速以及偏心率对QSn4-3轴承和Ti-6Al-4V轴承刚度的影响规律。结果表明:钛合金材料制成的轴承刚度优于传统锡基合金材料制造的轴承,各工况参数中,轴径间隙对轴承刚度的影响最为显著,其次是偏心率。该研究可为钛合金滑动轴承的数值模拟和设计提供参考。

大重合度直齿轮动载特性分析

针对大重合度直齿轮啮合齿数与普通直齿轮间的差异性变化,以一对大重合度直齿轮和普通直齿轮为研究对象,通过有限元法求解齿轮时变啮合刚度,建立大重合度直齿轮啮合耦合型动力学模型,利用Newmark-β时域积分求解齿轮系统动态响应,对其进行时频域分析并与普通直齿轮进行对比,获得了大重合度直齿轮在不同转速、误差影响下的动载系数变化规律。结果表明,大重合度直齿轮啮合刚度与普通齿轮有较大差异,其动态响应结果波动幅值较普通直齿轮有明显降低,提升了系统稳定性;大重合度直齿轮动载系数与普通直齿轮相比有明显下降,并且随着转速的升高和误差的增大出现不同程度的增加,其中在共振转速区域范围内增幅明显。

碳纳米管对天然橡胶复合材料高频动态性能的影响

以0.5份(每100质量份天然橡胶中添加的质量份)碳纳米管(CNTs)替换基础配方中不同份数(0,2,4,6,8)炭黑制备天然橡胶复合材料,研究了碳纳米管对天然橡胶复合材料静态力学性能和高频动态性能的影响。结果表明:随着CNTs替换炭黑份数的增加,复合材料的硬度降低,拉伸强度先升后降再升,断裂伸长率先降再增,100%定伸应力先增后降;用0.5份替换2份炭黑后的复合材料的综合静态力学性能最佳,此时拉伸强度和100%定伸应力均最大,分别比未用CNTs替换炭黑的复合材料提升13.52%和8.47%。随着CNTs替换炭黑份数的增加,复合材料动刚度均方根呈先减后增的趋势,替换2份炭黑后的复合材料动刚度均方根最小,比未用CNTs替换炭黑复合材料的动刚度均方根降低了12.94%,此时复合材料具有最好的高频动态性能,拉伸强度和定伸应力与高频动态性能正相关,断裂伸长率和硬度与高频动态性能的相关度不显著。

变位设计对斜齿轮系统动态特性影响研究

为了研究不同变位设计下斜齿轮的动态特性,以标准斜齿轮和变位斜齿轮为对比研究对象,基于拉格朗日动力学建立了斜齿轮传动系统动力学模型;采用解析法求解变位斜齿轮时变啮合刚度,分析了不同变位系数对啮合刚度的影响;将不同变位设计下的斜齿轮时变啮合刚度与动力学模型结合,分析了不同变位设计对斜齿轮系统动态特性的影响。结果表明,斜齿轮正传动修正能够减小时变啮合刚度,从而减小啮合力;负传动修正能够增大时变啮合刚度,从而增大啮合力。研究可为后续斜齿轮传动的设计和优化提供一定的参考。