Influence of vehicle-road coupled vibration on tire adhesion based on nonlinear foundation

The influence of pavement vibration on tire adhesion is of great significance to the structure design of vehicle and pavement.The adhesion between tire and road is the key to studying vehicle dynamics,and the precise description of tire adhesion affects the accuracy of dynamic vehicle responses.However,in most models,only road roughness is considered,and the pavement vibration caused by vehicle-road interaction is ignored.In this paper,a vehicle is simplified as a spring-mass-damper oscillator,and the vehicle-pavement system is modeled as a vehicle moving along an Euler-Bernoulli beam with finite length on a nonlinear foundation.The road roughness is considered as a sine wave,and the shear stress is ignored on the pavement.According to the contact form between tire and road,the LuGre tire model is established to calculate the tire adhesion force.The Galerkin method is used to simplify the partial differential equations of beam vibration into finite ordinary differential equations.A product-to-sum formula and a Dirac delt function are used to deal with the nonlinear term caused by the nonlinear foundation,which realizes the fast and accurate calculation of super-high dimensional nonlinear ordinary differential equations.In addition,the dynamic responses between the coupled system and the traditional uncoupled system are compared with each other.The obtained results provide an important theoretical basis for research on the influence of vehicle-road coupled vibration on tire adhesion.

Research on vibration and near-field sound radiation of ring-ribbed cylindrical shell coated deadening and decoupling materials

The research on structural vibration and sound radiation of underwater ring-ribbed cylindrical shell, which is coated with a kind of deadening and decoupling materials, becomes a focus in recent years. This paper analyzes the problem on two aspects: model experiment and numerical calculation. The model experiment is carried out including three cases firstly, in which the structural vibration response and radiating acoustic field are measured respectively, and the results gained in these three cases are analyzed to discuss the effect of reducing structural vibration and radiating noise of the deadening and decoupling materials. The coupling FEM/BEM and the SEA methods are both used in numerical calculation, i.e. the arithmetic of the coupling FEM/BEM method is adopted to calculate the low frequency characteristics and the SEA method is adopted to calculate the medium-high frequencies characteristics of the model. By comparing experimental results with numerical calculation results, it is proved that the algorithm adopted in this paper is reasonable.

Numerical modeling and experimental investigation of a two-phase sink vortex and its fluid-solid vibration characteristics

A sink vortex is a common physical phenomenon in continuous casting,chemical extraction,water conservancy,and other industrial processes,and often causes damage and loss in production.Therefore,the real-time monitoring of the sink vortex state is important for improving industrial production efficiency.However,its suction-extraction phenomenon and shock vibration characteristics in the course of its formation are complex mechanical dynamic factors for flow field state monitoring.To address this issue,we set up a multi-physics model using the level set method(LSM)for a free sink vortex to study the two-phase interaction mechanism.Then,a fluid–solid coupling dynamic model was deduced to investigate the shock vibration characteristics and reveal the transition mechanism of the critical flow state.The numerical results show that the coupling energy shock induces a pressure oscillation phenomenon,which appears to be a transient enhancement of vibration at the vortex penetration state.The central part of the transient enhancement signal is a high-frequency signal.Based on the dynamic coupling model,an experimental observation platform was established to verify the accuracy of the numerical results.The water-model experiment results were accordant with the numerical results.The above results provide a reference for fluid state recognition and active vortex control for industrial monitoring systems,such as those in aerospace pipe transport,hydropower generation,and microfluidic devices.

DYNAMIC ANALYSIS OF A SPATIAL COUPLED TIMOSHENKO ROTATING SHAFT WITH LARGE DISPLACEMENTS

The dynamic simulation is presented for an axial moving flexible rotating shafts, which have large rigid motions and small elastic deformation. The effects of the axial inertia, shear deformation, rotating inertia, gyroscopic moment, and dynamic unbalance are considered based on the Timoshenko rotating shaft theory. The equations of motion and boundary conditions are derived by Hamilton principle, and the solution is obtained by using the perturbation approach and assuming mode method. This study confirms that the influence of the axial rigid motion, shear deformation, slenderness ratio and rotating speed on the dynamic behavior of Timoshenko rotating shaft is evident, especially to a high-angular velocity rotor.

Vibration Reduction Performance of Damping-Enhanced Water-Lubricated Bearing Using Fluid-Saturated Perforated Slabs

As the first link element for the transmission of shaft vibration to the pedestal and even to the hull,water-lubricated bearing plays a key role in suppressing vibration.Although the porous structure is considered as one of the main methods for improving the wideband vibration and noise reduction performance of materials in many industrial fields,the studies in the field of water-lubricated bearing remain insufficient.To enhance vibration reduction performance,a fluid-saturated perforated slab is designed in this study,and via the establishment of a fluid-solid coupled vibration model,the influence law and impact levels were analyzed and verified by simulation and experiments.The results obtained verified that the total vibration amplitude of damping-enhanced stern bearing in the vertical direction was smaller than that of the normal stern bearing,and the reduction amplitude of the characteristic frequency agreed with the optimal value at approximately 0.1 of the volume fraction of the liquid phase when the solid-fluid phase was rubber–water.Additionally,the increase in fluid fraction did not enhance the damping effect,instead,it unexpectedly reduced the natural frequency of the raw material significantly.This research indicates that the design of the fluid-saturated perforated slab is effective in reducing the transmission of the vibration amplitude from the shaft,and presents the best volume fraction of the liquid phase.

Slip-Stick Vibrations of Wheelsets and Rail Corrugations

A dynamic space coupling model is developed for simulating the vibrations of wheel/rail systems as well as the torsion and bending vibrations of wheelsets. It is found that the slip stick vibrations of wheelsets are mainly caused and controlled by the crossing excitation or self excitation of the vertical vibrations of the whole system and by the bending vibrations and torsion vibrations of the wheelsets. It is found for the first time that the slip stick vibrations may occur in more than one forms, and one or another of the three kinds of vibrations is excited more strongly. Four typical kinds of slip stick vibrations are enumerated and described. The field investigation on rail corrugations shows that the four kinds of slip stick vibrations are most likely to exist and related with different corrugated features.

井下钻具耦合振动测量模型及实钻数据分析

为了监测井下钻柱的实际振动情况,调整钻进参数来控制井下钻柱的振动特性,从而优化钻进,提高钻速。针对如何通过测量的加速度信号对不同振动形式进行解译与表征的井下振动测量关键问题,建立钻柱振动的解析动力学模型,研究了某种特定振动模式下传感器输出信号的测量,分析了传感器输出信号与钻柱振动模式的关系。通过对模拟信号中振动模式所对应的加速度输出特征进行研究,分析得出实钻数据中所包含的振动信息。为井下振动测量信号的量化分析与运动模式解译提供依据。

风浪联合作用下分布式调谐质量阻尼器对海上半潜漂浮式风机的减振控制

海上半潜漂浮式风机在复杂深海环境下产生有害振动会威胁风机的安全性和耐久性,针对该问题并结合美国NREL的5 MW样机的漂浮平台几何结构构造,提出利用分布式调谐质量阻尼器(Tuned Mass Dampers,TMDs),即分别在漂浮平台的3根浮筒中布置TMD,形成等边三角形布置,对随机风浪联合作用下海上半潜漂浮式风机的平台纵摇振动进行控制。为了更好地描述分布式TMDs对海上半潜漂浮式风机的减振效果,基于拉格朗日方程和模态叠加法,对海上半潜漂浮式风机-TMDs耦合系统提出并建立了9自由度多体动力学模型。基于H_(∞)算法,即以平台纵摇频响函数的峰值为优化目标,对分布式TMDs的参数进行优化设计,优化设计中考虑了3个TMDs之间的耦合关系。对风机-TMDs耦合系统开展了风浪联合作用下的数值模拟,分析了分布式TMDs对平台纵摇响应的减振效果。结果表明:最优设计下的分布式TMDs对海上半潜漂浮式风机平台纵摇振动具有良好的减振性能;在三种不同工况的随机风浪荷载作用下,分布式TMDs对平台纵摇固有频率附近的功率谱密度曲线峰值减振率和标准差减振率能分别达到39%和52%以上。

拱坝坝身泄洪孔道脉动压力分布规律及其振动特征

【目的】高拱坝坝身泄洪安全研究涉及泄洪孔道设计、结构强度、泄洪过程中的水流压力分布和流态特性等方面。【方法】以某坝高为270 m拱坝为研究对象,利用计算流体力学模拟坝身泄洪孔道流场并分析其脉动压力分布特征,利用流体/结构耦合有限元模拟最不利工况压力脉动与坝体结构振动特征,解析泄流激励下高拱坝坝身振动机理。【结果】研究结果表明,拱坝坝身泄洪孔道内脉动压力变化极为复杂,其中表孔脉动压力最大值为133.25 kPa,最小值为29.48 kPa;中孔脉动压力最大值为5274.99 kPa,最小值为953.24 kPa.拱坝坝身泄洪孔道脉动压力在频域的能量分布均具有低频的特征,主能量分布在0~10 Hz的频率范围内。在泄流激励条件下,拱坝坝身总位移随脉动压力变化呈现一定周期性,且随周期总位移逐渐衰减,总位移值与脉动压力在同周期内先增大后减小,总位移值在1.2 s增大至最大值0.2120 cm,对应泄洪孔道脉动压力增大至极大值;拱坝坝身等效应力和等效应变的变化规律基本一致,1.2 s时等效应力和等效应变极大值分别为1426.60 kPa、7.49×10^(-5),且同周期内脉动压力呈现同样的变化趋势,拱坝坝身等效应力和等效应变与脉动压力变化具有完全的相关性。

随机激励下斜拉索-梁参数振动模型及响应分析

为了揭示随机激励下斜拉索参数振动特性,考虑拉索几何非线性、倾角以及桥面梁的协同振动影响,建立了斜拉索-桥面梁耦合参数振动模型,利用相空间变换推导了索-梁结构耦合振动伊藤状态方程组,给出了高斯白噪声作用下索梁振动时程求解迭代格式,分析了拉索随机响应时程、频域、统计特性以及概率密度变化,并与高斯截断方法进行比较,考察了拉索阻尼比、初始张力、桥面梁的初始扰动以及随机激励强度对拉索振动的影响规律。结果表明:斜拉索振动迭代方法可有效求解随机激励下索-梁耦合参数振动时程,与传统的高斯截断方法的计算结果吻合;随机激励下,斜拉索“拍振”振幅具有明显的不确定性,斜拉索与桥面梁结构发生耦合振动时,两者之间存在能量传递现象;斜拉索随机激励位移响应均值具有非平稳瞬态特性,其位移均方差的稳定时间大于理想激励下的响应;斜拉索响应功率峰值对应的频率和功率谱密度旁瓣峰值衰减量基本一致,但斜拉索第一旁瓣峰值与主峰差值并不相同。斜拉索振动响应概率密度分布满足高斯分布形态,置信区间约为0.98,符合马尔科夫性质。随着阻尼比增大,拉索阻尼抑制效率降低;桥面梁初始扰动越大,拉索振动位移越大;拉索张力越大,拉索振动幅值呈非线性减小趋势,但张力进一步增大时,拉索振动幅值衰减趋于稳定;随机激励强度越大,拉索响应越大。

波浪耦合作用下浮式风机非线性系统的统计线性化方法及其在振动控制中的应用

针对海上浮式风机既有分析方法难以高效率地预测其随机动力响应这一问题,提出了一种基于统计线性化算法的波浪耦合作用下浮式风机非线性系统的随机响应快速计算方法,并对其在浮式风机振动控制中的应用进行了研究。以Spar型海上浮式风机为对象,基于拉格朗日方程建立了其4-DOF的波浪耦合作用下的非线性模型,并验证了所建模型的准确性。在所建立的非线性模型基础上,提出了基于统计线性化算法的Spar型浮式风机随机振动分析方法,并从多方面对该方法进行了验证,结果表明该方法能将计算效率提升4,5个数量级,且具有足够精度。将该方法应用于浮式风机振动控制中,高效率地实现受TMD控制下的风机的控制参数优化和性能分析,得到了TMD的最优控制参数,发现TMD对浮式风机的振动控制效果有随海况等级的提高逐步降低的趋势。所提出方法兼具高精度、高效率和在不同海况下的普适性,同时也为海上浮式风机的设计优化、疲劳分析、可靠性验算等基于统计特性的研究提供了一种高效的分析方法。

钻柱振动的主被动控制研究进展与展望

在油气井钻进作业过程中,钻柱长期工作在充满钻井液的狭长井筒里,其受到井底压力、摩擦、岩石硬度变化的影响,受力情况非常复杂,会产生多种形式的振动,这些是影响钻具寿命和钻进效率的最主要因素。为系统分析工程界和学术界长期以来普遍关注的钻柱系统振动的有效控制问题,对近几十年来国内外在钻杆振动控制上使用的各种方法进行了分类和归纳,总结了各种方法的特点、应用场景以及不足之处,并对钻柱系统振动控制技术的发展趋势进行了展望。研究结果表明:(1)现有的钻柱振动主动控制主要集中于单一方向(扭转振动)和2个方向的耦联振动(纵扭耦联振动),且控制参数主要集中于钻压和扭矩,仅控制单方向的振动和单参数的调节,效果将很难保证;(2)被动控制是通过改变钻柱系统自身的结构或设计参数来抑制其振动,控制过程不受结构响应和外部干扰的影响,虽然效果有较大的局限性,但仍应在设计阶段给与足够的重视;(3)今后钻柱振动控制将朝着同时基于地面和井下测量数据,纵、横、扭3个方向联合控制的方向发展。结论认为,钻杆振动往往是几种基本振动形式的耦联,并具有明显的非线性特征,基于数据驱动的钻进系统动力学建模、考虑模型不确定性的现代鲁棒自适应控制技术以及新兴的人工智能技术将会成为未来钻柱振动研究和发展的主流趋势。

高速列车齿轮传动系统机电耦合建模与振动特性分析

为研究高速列车运行过程中齿轮传动系统的振动特性,文章基于多体系动力学理论和交流电传动理论,利用Simpack和Simulink建立了高速列车齿轮传动系统机电耦合动力学模型,并开展了有、无轮轨激励下的振动特性分析,通过对比仿真与实测齿轮传动系统振动加速度时频域数据,验证了模型的准确性。对比有、无轮轨激励工况显示:无轮轨激励时振动幅值较小,在频域上以内部齿轮啮合激励频率为主;而在轮轨激励作用下随着运行速度增加,齿轮传动系统振幅急剧增大,在频域上低速段以齿轮啮频为主,高速段以车轮多边形为主。分相区内外对比显示:电机扭矩作用使齿轮传动系统振动幅值显著增大,且频域中齿轮啮频和车轮多边形主频成分更明显。研究结果表明:由于高速列车齿轮传动系统服役环境的特殊性,电机扭矩、轮轨激励对齿轮传动系统振动存在显著影响,设计时须考虑负载和激励的耦合作用。

Vibration characteristics simulation and comparison of traditional cab system model and seat–cab coupled model for trucks

To define the application fields of the traditional cab system model and the seat–cab coupled model,this paper mainly aims to investigate the differences of the vibration characteristics of the two models.First,the two models and their motion equations were introduced.Then,based on the mechanical parameters of the seat and cab system for a truck,the transmissibility characteristics of the two models were analyzed.The results show that the traditional model can relatively accurately predict the pitch and roll vibration characteristics of the real seat–cab system.However,it overvalues the vertical vibration transmitted from the front suspensions of the cab.Third,the typical excitation conditions and the measuring points were selected.Finally,under the typical excitation conditions,the dynamic responses of the measuring points were calculated.The results show that under the vertical excitation condition,the dynamic responses of the two models have obvious differences.Under the roll excitation condition and the pitch excitation condition,the roll responses and the pitch responses of the cab between the two models show almost no obvious difference.Under the random excitation condition,the vertical acceleration responses have relatively larger deviations between the two models,however,the angular acceleration responses are almost the same.For the preliminary design of the cab system,the traditional cab system model can be used.However,for the accurate design and the optimization of the seat–cab system,the seat–cab coupled model is recommended.

基于LES方法的新型涡激振动风能采集器俘能特性分析

以所研制的涡激振动能量收集器(VIVPEHS)为研究对象,联合开源软件OpenFOAM和Matlab对大涡模拟(LES)方程、二阶范德波尔(Van der Pol’s)方程和高斯定律(Gauss’law)进行涡街振动俘能耦合计算,建立流机电耦合VIVPEHS数值模型,同时搭建并列双圆柱VIVPEHS俘能测试平台对数值模型开展实验验证。结果表明:升/阻力、压电梁位移、机电转换效率和尾流形态的预测值与实验数据符合良好。实验和计算结果表明,当圆柱直径(D)不变时,随着俘能距离(Sn)的增加,输出电压先增大后减小,在S_(n)=8D时输出电压最大;随着负载阻抗的增大,输出功率先增大后减小,存在最优负载阻抗(25000Ω),此时并列双圆柱VIVPEHS的输出功率可达72 mW,且直接点亮21只商用LED。

基于有限元法的油浸式变压器振动特性分析及优化设计

根据油浸式变压器的电气和结构参数,基于有限元仿真软件建立电路-磁场仿真模型;根据材料磁特性实验测量结果,结合J-A磁滞模型辨识得到的特征参数,获得材料的磁特性模型。建立变压器磁场-结构力场仿真模型,获得变压器周围磁场和应力分布;将计算得到的铁心麦克斯韦力和磁致伸缩力、绕组洛仑兹力作为激励,计算得到考虑材料磁特性的变压器振动位移;提取铁心不同位置的振动位移,获得铁心振动特性分布规律。在此基础上,为降低油浸式变压器的铁心振动,将有限元法与实验设计方法相结合,通过调整变压器绕组参数获得最佳的参数,结果表明优化前后变压器最大振动位移分别为6.12μm和5.71μm,优化方法显著降低了变压器的振动,对油浸式变压器减振降噪具有重要的指导意义。

落石冲击作用下西部山区铁路简支箱梁桥行车安全性研究

为研究落石冲击作用对铁路桥梁行车安全性的影响规律,以西部山区某铁路简支箱梁桥为研究对象,建立充分考虑材料非线性和接触非线性的落石冲击桥梁仿真分析模型和列车-轨道-桥梁耦合动力分析模型;阐明落石冲击桥墩工况下落石冲击力特征,分析落石冲击作用下桥上行车安全性能,并揭示落石冲击速度、冲击角度、冲击高度和落石直径对行车安全性的影响规律。研究结论如下:(1)落石冲击力的峰值随着落石速度、落石直径的增大而增大,落石冲击高度和冲击角度几乎不影响落石冲击力峰值;(2)落石直径的增大会扩大桥墩结构破坏范围,表现为多个冲击力峰值的出现和冲击力时程的延长;(3)落石冲击速度越快,冲击能量越大,对桥上行车安全影响越大,落石冲击高度越接近墩顶、落石直径越大,列车横向动力响应越大,对桥上行车安全威胁越大;(4)落石冲击角度各工况下列车各项安全评价指标时程曲线变化规律相似,对桥上行车安全影响变化较小;(5)轮重减载率对落石直径和冲击高度十分敏感,轮重减载率在落石直径达到2.5 m时超出规范限值。研究成果可为西部山区铁路桥梁全寿命周期的设计和安全运维提供参考。

空化流对管路振动的影响与分析

管路系统空化流动诱导的管路振动是导致管路破坏的重要因素.重点研究流动扰动与空化的相互作用,以及对管路振动的影响.采用Zwart-Gerber-Belamri(ZGB)空化模型研究小扰动下空化云随空化数及雷诺数的动态演变规律,发现空化云会引起管路的不平衡力和流量脉动.同时,空化云会加剧不平衡力和流量脉动的脉动幅值以及改变频率的调幅变频特性.在此基础上,将空化激励等效为激励源项引入传统管路流固耦合动力模型,得到一种改进的分析管路振动空化诱导机制的流固耦合动力学模型,对空化激励下的管路进行振动求解,给出临界空化数区间,同时揭示小扰动下空化诱导管路振动的原因.所得结果对研究空化管路系统的减振降噪及安全运行具有重要意义.

可调轴向力的振动压电俘能器建模与实验

针对传统能量收集器的工作带宽窄和输出功率低等问题,对一种可调轴向力的双稳态振动压电俘能器进行研究。该俘能器将两个压电悬臂梁自由端通过附加质量连接为一个梁,通过测微调节器控制轴向压力使系统变为双稳态结构。利用非保守力的拉格朗日方程对压电俘能器进行发电分析,建立了机电耦合模型。利用PZT5H压电材料搭建实验样机和平台,进行了系统俘能特性的调查研究。实验研究结果表明,仿真值预测的结构特性与实验结果一致性较好,该结构能有效拓展低频发电带宽,压电扫频输出具有两个明显低频峰值。利用实验对系统的负载参数进行优化,双稳态系统的电压输出峰值能达到17V。

轨道交通下层状地基中混凝土排桩隔振效果研究

为了研究在轨道交通荷载作用下混凝土排桩的隔振效果,特建立“车轮-轨道-地基”耦合模型,通过轨道竖向不平顺功率谱建立不平顺轨道并模拟列车在其表面行驶过程,根据控制变量法研究在混凝土排桩几何参数变化的情况下对混凝土排桩隔振效果的影响,通过本文的研究结果表明:混凝土排桩具有一定的隔振效果,随着各个参数的变化其隔振效果也会发生改变;桩长的增加,地基表面和地基深处隔振效果增强;随着埋置深度和桩间距的增加,混凝土排桩的隔振效果均下降,布置混凝土排桩埋深越浅隔振效果越好,布置混凝土排桩越紧密隔振效果越好。在土层的分界面上会出现振动加强的效果,在实际施工中应注意土体分层面带来的影响。