One Computational Method of the Eigenvalues of the Horizontal Vibration Problem of Beam

This paper considers one computational method of the eigenvalues approximate value of the horizontal vibration problem of beam. The proof of our main result is based on the variational formula. First of all, Cauchy inequality is used to obtain a basic inequality. Secondly, the functions of basis are made by Galerkin method, and the error estimates of eignevalues are obtained by Cauchy inequality. At last, the computational method of the approximate value of the eigenvalues turns out immediately, and acc...

Present Status and Prospect of High-Frequency Electro-hydraulic Vibration Control Technology

Electro-hydraulic vibration equipment(EHVE)is widely used in vibration environment simulation tests,such as vehicles,weapons,ships,aerospace,nuclear industries and seismic waves replication,etc.,due to its large output power,displacement and thrust,as well as good workload adaptation and multi-controllable parameters.Based on the domestic and overseas development of high-frequency EHVE,dividing them into servo-valve controlled vibration equipment and rotary-valve controlled vibration equipment.The research status and progress of high-frequency electro-hydraulic vibration control technology(EHVCT)are discussed,from the perspective of vibration waveform control and vibration controller.The problems of current electro-hydraulic vibration system bandwidth and waveform distortion control,stability control,offset control and complex vibration waveform generation in high-frequency vibration conditions are pointed out.Combining the existing rotary-valve controlled high-frequency electro-hydraulic vibration method,a new twin-valve independently controlled high-frequency electro-hydraulic vibration method is proposed to break through the limitations of current electro-hydraulic vibration technology in terms of system frequency bandwidth and waveform distortion.The new method can realize independent adjustment and control of vibration waveform frequency,amplitude and offset under high-frequency vibration conditions,and provide a new idea for accurate simulation of high-frequency vibration waveform.

Vibration Analysis of a Drillstring in Horizontal Well

The complicated geological conditions will bring great challenges to the drillstring of horizontal wells for the reason that the increase of the well depth in Sichuan-Chongqing region.Since drillstring failure and friction during drilling are generally caused by drillstring vibration,great importance must be attached to computer simulation methods for the prediction of drillstring vibration.A finite element model considering axial,lateral and torsional vibration is established.In order to verify the established numerical model,an indoor experimental device based on the similarity principle was established.The vibration characteristics of three shale gas horizontal wells drillstrings are described.The reasons for the large difference in vibration characteristics between the three wells were discussed by changing the well structure,BHA(bottom hole assembly)and drilling parameters.The simulation results show that the depth of ultra-deep well 3 is only 1.27 times of that of medium-deep well 2,but the fluctuation of WOB(weight on bit)is 2.8 times.The primary factor for the great difference of WOB fluctuation is the change of vertical section depth,the secondary factor is the change of the horizontal section length.Additionally,the reasonable range of speeds has been proposed and applied in the field.The advantage of this numerical analysis method is that it can judge the vibration and friction torque of drillstring in horizontal wells with arbitrary structure,drilling parameters and BHA.This method has certain guiding significance to the field practice.

Four-Beam Model for Vibration Analysis of a Cantilever Beam with an Embedded Horizontal Crack

As one of the main failure modes, embedded cracks occur in beam structures due to periodic loads. Hence it is useful to investigate the dynamic characteristics of a beam structure with an embedded crack for early crack detection and diagnosis. A new four-beam model with local flexibilities at crack tips is developed to investigate the transverse vibration of a cantilever beam with an embedded horizontal crack; two separate beam segments are used to model the crack region to allow opening of crack surfaces. Each beam segment is considered as an Euler-Bernoulli beam. The governing equations and the matching and boundary conditions of the four-beam model are derived using Hamilton＇s principle. The natural frequencies and mode shapes of the four-beam model are calculated using the transfer matrix method. The effects of the crack length, depth, and location on the first three natural frequencies and mode shapes of the cracked cantilever beam are investigated. A continuous wavelet transform method is used to analyze the mode shapes of the cracked cantilever beam. It is shown that sudden changes in spatial variations of the wavelet coefficients of the mode shapes can be used to identify the length and location of an embedded horizontal crack. The first three natural frequencies and mode shapes of a cantilever beam with an embedded crack from the finite element method and an experimental investigation are used to validate the proposed model. Local deformations in the vicinity of the crack tips can be described by the proposed four-beam model, which cannot be captured by previous methods.

Research on Horizontal Vibration of Heavy-Weight Drill Pipes in Directional Drilling

The mode of load and deformation of directional drilling string and the expression of trigonometric series of deflection equation are established by means of elastic deformation energy and of the vertical and horizontal bending. A calculation formula for natural frequency of horizontal resonance and rotational speed is derived based on the calculation method by Ritz, with which analysis is made for the cause and affecting factors of the excessive abrasion of heavy-weight drill pipe in high-angle holes so as to provide reference and basis for rational selection of drilling parameters and drilling tools in the future high-angle directional drilling.

Vertical vibration control using nonlinear energy sink with inertial amplifier

To reduce additional mass, this work proposes a nonlinear energy sink(NES)with an inertial amplifier(NES-IA) to control the vertical vibration of the objects under harmonic and shock excitations. Moreover, this paper constructs pure nonlinear stiffness without neglecting the gravity effect of the oscillator. Both analytical and numerical methods are used to evaluate the performance of the NES-IA. The research findings indicate that even if the actual mass is 1% of the main oscillator, the NES-IA with proper inertia angles and mass distribution ratios can still effectively attenuate the steady-state and transient responses of the main oscillator. Nonlinear stiffness and damping also have important effects. Due to strongly nonlinear factors, the coupled system may exhibit higher branch responses under harmonic excitation. In shock excitation environment, the NES-IA with a large dynamic mass can trigger energy capture of both main resonance and high-frequency resonance. Furthermore, the comparison with the traditional NES also confirms the advantages of the NES-IA in overcoming mass dependence.

Investigation of Eccentric PM on High-frequency Vibration in FSCW PM Machine Considering Force Modulation Effect

This study investigates the negative influence of an eccentric permanent-magnet(PM)design on high-frequency electromagnetic vibration in fractional-slot concentrated-winding(FSCW)PM machines.First,an analytical expression for the sideband current harmonics was derived using the double Fourier series expansion method.Then,the characteristics of the flux-density harmonics are studied from the perspective of the space-time distribution and initial phase relationship.The influence of the eccentric PM design on high-frequency electromagnetic and concentrated forces was studied based on the electromagnetic force modulation effect.Consequently,an eccentric PM design is not conducive to reducing the 2pth-order high-frequency electromagnetic forces.Finally,two FSCW PM machines with conventional and eccentric PM designs are manufactured and tested to verify the theoretical analysis.The results show that the eccentric PM design worsens high-frequency vibrations.

Solidification of horizontally continuous casting of super-thin slab in stable magnetic field and alternating current

The solidified structures of horizontally continuous casting（HCC） of super-thin slab and its relations with the current were studied under the electromagnetic vibration（EMV）.The results show that,under the action of the periodical forces from EMV,the solidified structures of the super-thin slab of pure tin is greatly refined,and the extent of grain refinement is increased with the magnitude of alternating current.For the Sn-10%Pb alloy,it is shown that the EMV promotes the growth of equiaxed grains in the center of super-thin slab,and the grains are refined with the alternating current increasing.This is useful to prevent some solidification defects in the horizontally continuous casting of super-thin slab,such as columnar grains butting,porosity,inclusions and gases gathering,and composition segregation in the centre of slab.

基于ADAMS/Vibration的桥式起重机振动研究

根据桥式起重机垂直振动和横向振动的特点,将机车简化为二自由度质量—弹簧系统,并建立基于ADAMS的虚拟样机模型,对受钢丝绳的物理参数k、c及货载质量m影响的结构动态特性进行了振动仿真研究,得到了整机在小车起吊过程和大车制动过程的振动特性。

Research and application on three-dimensional seismic and vibration isolation for building

This paper presents the study of a three-dimensional(3D) isolation system.Firstly,the authors investigated the effects of an innovative 3D isolator,which was composed of a connecting plate,a rubber pad for vibration isolation in the vertical direction and a horizontal rubber bearing for seismic isolation in both horizontal directions.Secondly,the authors designed such a vibration isolation system and installed it underneath two specific residential buildings which were built directly over an existing subway communication hub platform in Beijing.These buildings required good performance vibration and seismic isolation system to reduce the impact from the running of nearby subway trains.Finally,in situ tests were conducted for both the isolated and the non-isolated buildings for the purpose of comparison.The test results showed that the maximum acceleration response level of the isolated superstructure is reduced by 10% as compared to that of the platform.The maximum attenuation of vibration reaches up to 25 dB.The 3D system explored in this paper is very effective in control and suppression of building vibration induced by earthquakes or running of trains.

Horizontal dynamic response of a large-diameter pipe pile considering the second-order effect of axial force

The second-order effect of axial force on horizontal vibrating characteristics of a large-diameter pipe pile is theoretically investigated.Governing equations of the pile-soil system are established based on elastodynamics.Threedimensional wave equations of soil are decoupled through differential transformation and variable separation.Consequently,expressions of soil displacements and horizontal resistances can be obtained.An analytical solution of the pile is derived based on continuity conditions between the pile and soil,subsequently from which expressions of the complex impedances are deduced.Analyses are carried out to examine the second-order effect of axial force on the horizontal vibrating behavior of the pipe pile.Some conclusions can be summarized as follows： stiffness and damping factors are decreased with the application of axial force on the pile head; distributions of the pile horizontal displacement and rotation angle are regenerated due to the second-order effect of the applied axial force; and redistributions of the bending moment and shearing force occur due to the second-order effect of the applied axial force.

自复位浮置物隔震系统的动力试验与数值分析

提出了一种自复位浮置物隔震系统,该系统采用双层正交导轨隔离水平地震,并通过预拉弹簧绳实现自复位。考虑系统摩擦与弹簧绳刚度,建立了自复位浮置物隔震系统的理论模型,完成了不同工况下的隔震系统振动台试验,结果表明输入地震波的加速度峰值越高,隔震系统的隔震率也会相应提升。在输入地震波加速度峰值为0.15、0.2、0.4、0.62 g时,隔震系统平均隔震率分别为50%、58%、75%、82%。在相同峰值的地震波及楼面波地震动输入下,隔震系统均具有良好的隔震效果且能够实现系统自复位。最后建立了浮置物隔震支座-浮置物体系的有限元模型,验证了隔震系统理论模型的有效性。

非饱和土地基中端承桩对SH波的水平地震响应

为探讨非饱和土地基中SH波作用下端承桩的水平地震响应,先基于一维波动理论得出SH波引起的土层自由场水平振动解,然后考虑非饱和土体动剪切模量随其饱和度的变化特性,采用三维连续介质力学和Euler梁模型建立轴向静荷载下非饱和土-端承桩水平耦合振动模型,进而通过引入势函数和分离变量法推导出桩顶水平位移相互作用因子、桩顶水平位移放大因子和桩身曲率比的表达式,经与已有成果对比验证后再经参数分析,获得土体饱和度、桩身长径比和土体黏滞阻尼对桩身水平抗震特性的影响规律:土体饱和度和桩身长径比仅在高频范围对相互作用因子和放大因子有显著影响;土体黏滞阻尼仅在共振频率使得相互作用因子和放大因子分别逐渐增大和减小。

西寺坪电站一号机组动平衡试验及稳定性测试分析

西寺坪电站采用HLD06A-WJ-50型水轮机组SFW630-6/990型发电机组,于2020年检修中更换了发电机前、后轴承,启动过程中发电机振动偏大,为此对机组进行了动平衡试验及稳定性试验。经动平衡试验指导处理后,调整效果较好。稳定性试验中变电流试验结果表明,该机组电磁平衡状态较差,建议对发电机进行相关电气专项检查或试验。目前该机组摆度测点处的原始偏摆偏大,建议对轴颈表面光洁度、椭圆度等进行检查和修复,复核其原始偏摆值。

考虑连续特性的水平井钻柱轴向振动分析

为精确描述水平井钻柱轴向受迫振动规律,以连续性波动理论为基础,考虑了钻柱连续特性、库伦阻尼及钻井液黏性阻尼作用和轴向振动工具对钻柱的位移激励,并采用等效黏性阻尼法对库仑阻尼进行线性化处理,建立了轴向振动工具作用下的水平井钻柱运动的动态解析模型;通过轴向振动工具测试实验验证了本文所建模型,并利用数值模拟分析了轴向振动工具的频率及钻柱与井壁间摩擦系数对水平井钻柱轴向受迫振动的影响。结果表明:在一定范围内增加轴向振动工具的振荡频率可提高水平井钻柱的轴向受迫振动响应;钻柱与井壁间摩擦系数对水平井钻柱轴向受迫振动的影响随着钻柱长度的增加而降低。本文的研究方法和模型可为改善轴向振动工具在水平井作业中的应用提供理论指导。

层状地基中楔形桩水平向非线性振动响应分析

楔形桩是一种集施工简便、承载力高等特点的新型路基处理桩型。为进一步完善楔形桩水平振动分析理论以推广其在工程中的应用,基于动力Winkler地基理论,建立楔形桩-土体水平耦合振动非线性分析模型,针对水平简谐荷载作用下层状地基中的楔形桩水平动力响应问题展开研究,并探讨不同桩身长径比对桩土分段的敏感性,研究楔形角和土体分层特性参数对楔形桩水平向非线性动力响应的规律。结果表明:随着楔形角或桩侧土体模量的增大,楔形桩水平动力特性均会得到显著改善;等体积条件下保持桩端半径不变改变桩长较保持桩长不变改变桩端半径时水平动力性能表现更好;桩侧上层土体性质变化对桩顶动力响应影响更加显著。

新型空心管屏障隔振效果对比数值研究

为研究新型空心管屏障在工程隔振中的应用价值及对其影响因素进行分析,基于Plaxis3D有限元分析软件,依照已有的模型和现场试验参数建立有限元模型,并采用经过验证的有限元模型进行仿真计算。基于有限元数值分析方法,开展新型空心管隔振效果与已有模型和现场试验中屏障的对比研究;分析单根空心管高度和空心管数量对新型空心管隔振效果的影响。研究发现:新型空心管屏障平均减振系数比填充沟、排桩和波阻板小得多,彼此之间平均减振系数偏差最大可达373%,而与空沟的平均减振系数偏差较小。这一结果表明:新型空心管的隔振效果明显要优于填充沟、排桩和波阻板,而与空沟的隔振效果相接近。此外,还发现在不同的工程条件下,新型空心管隔振屏障的平均减振系数大都在0.3以下,具有很好的隔振效果;且随着空心管数量的增加,空心管的隔振效果也随之提升;在空心管总高度不变的条件下,调节单根空心管的高度对屏障的隔振效果影响很小。

四轴水平振动输送机的物料速度仿真分析与实验

针对当前四轴水平振动输送机的物料速度随输送机偏心轴相位角变化规律不明确的问题,以某钢厂水平振动输送机的参数为基础,对机体与物料速度进行了理论推导和仿真分析。首先,推导了机体激振力与机体速度的通用公式,并对3种初始相位角对应的机体速度进行了仿真,分析了初始相位角对机体速度的影响规律;然后,对机体速度和物料速度进行了对比仿真,并研究了物料起始运动时间、初始相位角以及角频率对物料速度的影响规律;最后,采用仿真软件分析了固定高速轴(或低速轴)的初始相位角时,物料稳态平均速度随低速轴(或高速轴)相位角变化的规律,并对相关内容进行了实验验证。研究结果表明:输送机4个偏心轴以及齿轮等相关部件组装完成后,物料的稳态平均速度不随任一个偏心轴质心相位角的变化而变化;在输送机稳定运行时,物料的稳态平均速度与其加入料槽内的先后顺序无关;此外,针对某一机型的最佳物料速度,在高速轴(或低速轴)的初始相位角不同时,两种轴的相位角差也可能不同,单纯指定相位角差3π/4、π/2或3π/2等特定角度以利于物料输送的方案是不合理的,应该同时规定高低速偏心轴的相位角。

页岩气水平井振动固井套管柱振动特性研究

为了求解页岩气水平井振动固井套管柱振动特性和动力响应,考虑扶正器分布支承的特点,运用传递矩阵法建立了页岩气水平井套管柱的动力学模型,并通过试验验证了套管柱动力学模型的准确性。在此基础上,研究了扶正器支承和套管柱参数对套管柱振动特性的影响,探索了振动固井工况下套管柱的动力响应和振幅衰减规律。研究结果表明:扶正器刚度增大、扶正器支承数量增加和套管外径增大均会导致套管柱固有频率的增加;扶正器刚度增大会加快套管柱振幅衰减;增大激振力的同时利用低频共振能提高套管柱振动有效传播距离。该研究能够为页岩气水平井振动固井装备设计提供有益参考。

仿真数据驱动的长期服役电梯导轨故障迁移诊断方法

现有的电梯导轨故障诊断研究存在水平振动分类数据稀缺,训练和测试数据集分布差异较大等问题。提出了一种仿真数据驱动的长期服役电梯导轨故障迁移诊断方法。首先构建电梯轿厢的水平动力学模型,将不同类型的导轨故障激励作为系统输入进行仿真,获得丰富的轿厢水平异常振动数据;然后融合残差网络和卷积注意力机制来提取故障特征,采用子领域自适应方法实现无监督场景下源域与目标域条件分布的对齐;最后使用不同工况下的电梯水平振动数据作为目标域对所提方法进行验证。实验结果表明,所提方法在无监督跨域场景下具有较高的故障诊断精度,为解决长期服役电梯的故障数据稀缺问题提供了参考。