预应力模态下对旋风机叶片流致振动特性

为了研究预应力模态下对旋风机叶片流致振动特性,采用基于预应力模态的强迫振动响应方法进行仿真分析,以非定常流场压力脉动为激励载荷,对叶片实现强迫振动响应计算。分析了流场非定常激振力的特征频率,对比了无预应力模态和预应力模态下监测点的强迫振动响应特性。研究结果表明,对旋风机流场激振力特征频率为一级、二级叶轮的通过频率及其倍频;由于一级叶轮的3倍叶频与一级叶片2阶固有频率接近,二级叶轮4倍叶频与二级叶片3阶固有频率接近,从而叶片结构发生小幅共振,分别产生相应监控点的振动加速度最大峰值;无预应力模态由于忽略了预应力下的刚化效应,其监控点振动加速度曲线峰值高于预应力模态,两种模态计算出的监控点总振动加速度级差值最大约1.5 dB。     

流体激振及其对离心叶轮转子的影响

求出了离心泵叶轮所受的流体激振力,并研究了离心泵在考虑流体激振力时的动态特性。建立了在该状态下的运动微分方程。分析了流体激振力对离心泵叶轮系统的振动及其轴心轨迹的影响,为离心泵的监控和设计提供了理论依据。     

基于激励源的整车振动特性研究

针对影响汽车乘坐舒适性的两大主要激励源——路面激励和发动机激振力,建立了整车振动系统模型和整车的多体动力学模型,通过B级路面的虚拟行驶试验,对不同车速下,有、无发动机激振力情况的汽车座椅地板处垂向振动进行了比较研究。研究结果表明:路面激励在座椅振动响应贡献中占主要部分,表现为低频振动;发动机激振力对座椅振动贡献量为20%到40%,且随车速增加而增大,表现为与发动机振动对应的稍高频率的振动。     

短时脉冲激励下隧道振动响应与模态参数识别

为了研究短时脉冲激振力下隧道结构振动响应及有效地提取隧道结构的模态特征。首先分析了锤击作用下的不同短时脉冲激振力精度及其频域特性,其次将短时脉冲激振力应用于上海地铁12号某盾构隧道进行了现场动力测试,最后分析了脉冲激振与隧道结构响应之间的传递函数,并结合随机减量、正交多项式法及自回归滑动平均模型法有效地提取隧道结构的模态参数。结果表明:短时脉冲激振力的中低频振动信号在隧道结构中传递特性较好,传递距离较远。隧道结构的模态频率呈现明显低频特征,前10阶模态频率在100 Hz以下。因此,短时脉冲激振力能够很好地应用于隧道动力测试及模态识别,可为基于模态特征的隧道结构损伤识别及健康监测多个研究领域提供有效的支撑和参考依据。     

汽轮机转子-机匣系统碰摩的分叉现象分析

提高汽轮机热效率的有效途径是采用超超临界压力.压力的提高使得作用在转子-机匣上的激振力将显著增大,有必要对气流激振力作用下的转子-机匣系统的非线性动力学特性进行研究.本文采用双控体模型,以汽轮机转子-机匣系统为研究对象,将转子和机匣作为统一的弹性体,采用四阶Ruge-Kutta法进行数值仿真,来研究在密封气流激振力以及机匣体振动的双重作用下的转子与机匣的碰摩运动,揭示了转子与机匣碰摩的分叉动力学特性.给出了气流激振力作用前后的碰磨转子系统响应的分叉图、轨迹图、相轨迹图和Poincare映射图.着重讨论了输入气压和转子转速等决定气流激振力大小的因素对碰磨转子分叉特性的影响.对提高超超临界汽轮机的可靠性提供了有意义的参考.     

大转矩弹性橡胶联轴器高频减振特性分析

针对以往弹性联轴器减振特性分析中高频减振特性难以计算评佑的问题,基于应力波理论对弹性联轴器有限元模型进行高频激振作用下的弹性波分析,通过有限元分析软件Abaqus的动力学显式有限元方法求解该高频激振作用下的位移响应结果,通过FFT变换并计算获得了各不同高频激振力作用下的振级落差,比较分析不同高频段激振力作用下弹性橡胶联...     

汽流激振力下转子裂纹-碰摩振动故障研究

针对汽轮机机组在运行过程中出现的振动故障问题,在考虑汽流激振力情况下建立了转子系统故障分析模型.通过数值分析方法,对转子故障模型进行了研究分析.结果 表明:在综合考虑汽流激振力作用下多种非线性因素作用时,碰摩转子系统在临界转速的混沌区域明显减小,并出现有幅值较大的1/4、3/4倍频.当裂纹深度增加时,故障转子系统的混沌区域逐渐减小;在超临界转速区域系统响应呈现出较长的周期3运动,频谱图上主要体现为3/4、2倍频.研究结果为进一步的故障问题分析诊断提供一定的理论依据.     

非稳态流体激励下离心泵转子振动特性研究

建立了离心泵全流道三维定常及非定常CFD数值模型,通过非稳态计算得到作用于叶轮上的流体激振力,同时建立了泵转子有限元模型,研究不平衡质量与非稳态流体激振力对转子振动特性的影响。研究结果表明离心泵叶轮内流体激振力具有多种频率成分。不考虑转子上不平衡质量影响时,叶轮处转子在流体激振力作用下振动幅值最大,依次为转轴中部、下部轴承和上部轴承对应的转子位置。转轴上不同位置振动频率特性具有差异,实际故障诊断时要考虑测试部位的影响。考虑不平衡质量影响时,在远离受流体激振力作用的叶轮部位,转子振动频率成分减少。     

齿式联接不对中转子的弯扭耦合振动特性分析

以齿式联轴器的不对中故障为研究对象,推导不对中激励力表达式,并从动力学的角度,建立不对中弯扭耦合振动微分方程。基于该微分方程,文中先从理论分析角度,定性分析弯振对扭振的影响和扭振对弯振的影响,接着从变转速过程、质量偏心、不对中量以及阻尼系数对弯扭耦合特性影响几方面进行数值仿真分析。计算表明,弯振与扭振是相互耦合的,质量偏心是耦合的前提。弯振频率包含工频和二倍频成分等,不对中越严重,二倍频所占比例越大,其轴心轨迹为双环椭圆。弯扭耦合将激发各阶谐波扭振,包括工频、二倍频和三倍频,其中工频扭振占主导地位。     

振动拉削系统振幅衰减特性分析与实验研究

为了探究振动拉削中导致激振幅值衰减的主要因素,以双伺服阀电液激振拉削设备为研究对象,综合考虑双阀电液激振系统动力学特性,以及拉刀多齿接触效应、工件尺寸参数等影响下的动态拉削力特征,建立了振动拉削过程中的激振系统模型;再分别通过理论计算及系统实验,对比研究了电液激振器在非线性负载扰动下实际输出力和输出位移的衰减波形,为振动拉削激振系统参数优化提供理论指导和实验依据。实验结果分析表明：振动频率是导致系统振幅衰减的主要因素,而动态拉削力通过影响激振缸活塞的运动特征使得输出波形的峰值衰减,甚至使位移振幅趋向于0。     

双层隔振系统模态匹配分析及其振动特性

针对出口内燃动车动力包的双层隔振问题,根据双层隔振系统的结构参数,建立双层隔振系统的有限元模型。对双层隔振系统进行了模态计算,掌握了系统的频率特性。根据柴油机组激振力的频率特性,定量对双层隔振系统进行模态匹配分析。对双层隔振系统进行谐响应计算,准确判断构架和机组是否发生共振,验证模特匹配的合理性。施加怠速工况下的各个激振力,对双层隔振系统进行了强迫振动计算,计算双层隔振系统的振动烈度和传递率。结果表明：双层隔振系统的隔振性能良好,能满足实际工程需求,研究结果可为实际工程提供参考。     

REGULARITY OF VIBRATION RESPONSE OF MECHANICAL SYSTEM UNDER AFFECT OF VARI-FREQUENCY EXCITING FORCE

ＲＥＧＵＬＡＲＩＴＹＯＦＶＩＢＲＡＴＩＯＮＲＥＳＰＯＮＳＥＯＦＭＥＣＨＡＮＩＣＡＬＳＹＳＴＥＭＵＮＤＥＲＡＦＦＥＣＴＯＦＶＡＲＩ－ＦＲＥＱＵＥＮＣＹＥＸＣＩＴＩＮＧＦＯＲＣＥＲＥＧＵＬＡＲＩＴＹＯＦＶＩＢＲＡＴＩＯＮＲＥＳＰＯＮＳＥＯＦＭＥＣＨＡＮＩ...     

磁轴承激励下转子系统动力学特性

为分析磁轴承激励下转子系统的振动机理,应用一维有限元方法建立了双盘转子系统动力学特性计算模型,研究了不同类型磁轴承激励下转子系统的动力学行为.研究结果表明:同向旋转的扫频激励力激发了转子系统的正进动模态,而反向旋转的扫频激励力激发了转子系统的反进动模态,两种情况下转子系统均以圆轨迹进动;由于单向简谐激励力可以分解为同向...     

WRIST FORCE SENSOR'S DYNAMIC PERFORMANCE CALIBRATION BASED ON NEGATIVE STEP RESPONSE

Negative step response experimental method is used in wrist force sensor＇s dynamic performance calibration. The exciting manner of negative step response method is the same as wrist force sensor＇s load in working. This experimental method needn＇t special experiment equipments. Experiment＇s dynamic repeatability is good. So wrist force sensor＇s dynamic performance is suitable to be calibrated by negative step response method. A new correlation wavelet transfer method is studied. By wavelet transfer method, the signal is decomposed into two dimensional spaces of time-frequency. So the problem of negative step exciting energy concentrating in the low frequency band is solved. Correlation wavelet transfer doesn＇t require that wavelet primary function be orthogonal and needn＇t wavelet reconstruction. So analyzing efficiency is high. An experimental bench is designed and manufactured to load the wrist force sensor orthogonal excitation force/moment. A piezoelectric force sensor is used to setup soft trigger and calculate the value of negative step excitation. A wrist force sensor is calibrated. The pulse response function is calculated after negative step excitation and step response have been transformed to positive step excitation and step response. The pulse response function is transferred to frequency response function. The wrist force sensor＇s dynamic characteristics are identified by the frequency response function.     

基于欧拉梁的准零刚度隔振系统动力特性分析

将两端受轴向压力的欧拉梁和线性弹簧并联,组成一个具备高静刚度和低动刚度的准零刚度隔振器。通过对隔振系统进行静力分析,给出系统具备准零刚度特性所需的条件。利用谐波平衡法求解系统的振动微分方程,分析系统的幅频特性,给出了系统的力传递率,讨论了阻尼、激励力等参数对系统传递率的影响。最后分析了该隔振系统的跳跃频率。研究结果表明：激励力以及初始偏移量的增大会使系统的隔振效果变差,因此要控制激励力的大小并尽量避免超载;阻尼比的选取需要综合考虑高频的隔振效果和有效隔振频率范围。     

基于叶轮转子系统下的干气密封轴向振动分析*

为探究基于叶轮转子系统下干气密封轴向振动特性,基于干气密封结构特性,建立叶轮转子-轴承-干气密封系统轴向振动模型,采用待定系数法进行求解,推导得出静环轴向振动幅值表达式;建立叶轮转子-轴承-干气密封系统几何模型,运用ANSYS Workbench软件进行模拟仿真计算,分析气膜刚度和激振力对轴向振动的影响。结果表明:气膜刚度对动、静环振动幅值的影响不大;动、静环振动频率相同、振动幅值相同,说明动、静环的追随性高,其间隙稳定,从而保证干气密封的稳定运行;动、静环位振动幅值与激振力成正比关系,说明激振力严重影响干气密封的稳定性,为提高干气密封的稳定性,应平衡好叶轮的轴向激振力。     

Investigation of a new-type precision cropping system with variable-frequency vibration

To investigate a new-type precision cropping system with variable-frequency vibration, it is necessary to obtain the characteristics of vibrating force and displacement of shearing die in different exciting frequencies. The model and equations of a six-degree-of-freedom vibrating system are established, and the six natural frequencies of the system are achieved by means of classical analysis method, the amplitude-frequency characteristics are described according to Cramer's rule, and the theoretical analysis results are verified by experiments. The approximate relationship between the vibrating force and exciting frequency are achieved and the experimental results show that crack will propagate along z direction, which is in agreement with the theoretical results. The work-piece cross-section obtained by the experiments has no radial distortion and deviation angle, moreover, the cutting force is lower and the die lifetime is longer compared with common bar cropping method. A new cross-section quality assessment method is proposed for the work-piece obtained under the control of different frequency-time characteristic curves. The assessment results show that the linear decrement control mode is better for producing good-quality work-piece.     

柔性铰链近场超声悬浮滑块动特性系数研究

应用可压缩气体动力润滑理论建立了柔性铰链超声挤压膜滑块的动、静特性系数模型,并应用数值方法对模型进行求解,获得了高频激励条件下柔性铰链气体挤压膜滑块的动、静特性系数。讨论了悬浮高度、激励振幅以及激励频率对动特性系数的影响。根据分析发现,这些参数都对挤压膜特性有着显著的影响。悬浮高度越高,挤压膜刚度和阻尼越小。激励振幅越大,挤压膜刚度和阻尼越大。而频率的影响几乎呈线性关系,频率越高,刚度和阻尼越大,挤压膜刚度和阻尼都随着频率的增加而增加,最后对这种结论进行了解释。     

Effects of joint on dynamics of space deployable structure

Joints are necessary components in large space deployable truss structures which have significant effects on dynamic behavior of these joint dominated structures.Previous researches usually analyzed effects of one or fewer joint characters on dynamics of jointed structures.Effects of joint stiffness,damping,location,number,clearance and contact stiffness on dynamics of jointed structures are systematically analyzed.Cantilever beam model containing linear joints is developed based on finite element method,influence of joint on natural frequencies and mode shapes of the jointed system are analyzed.Analytical results show that frequencies of jointed system decrease dramatically when peak mode shapes occur at joint locations,and there are cusp shapes present in mode shapes.System frequencies increase with joint damping increasing,there are different joint damping to achieve maximum system damping for different joint stiffness.Joint nonlinear force-displacement is described by describing function method,one-DOF model containing nonlinear joints is established to analyze joints freeplay and hysteresis nonlinearities.Analysis results show that nonlinear effects of freeplay and hysteresis make dynamic responses switch from one resonance frequency to another frequency when amplitude exceed demarcation values.Joint contact stiffness determine degree of system nonlinearity,while exciting force level,clearance and slipping force affect amplitude of dynamic response.Dynamic responses of joint dominated deployable truss structure under different sinusoidal exciting force levels are tested.The test results show obvious nonlinear behaviors contributed by joints,dynamic response shifts to lower frequency and higher amplitude as exciting force increasing.The test results are further compared with analytical results,and joint nonlinearity tested is coincident with hysteresis nonlinearity.Analysis method of joint effects on dynamic characteristics of jointed system is proposed,which can be used in optimal design of joint parameters     

螺栓连接接口轴向振动能量耗散特性研究

根据螺栓连接接触面的轴向接触微观特征,将接触面的接触方式分为峰-峰接触和峰-谷切向接触,提出了螺栓连接轴向振动的动力学模型。在假定接触面出现简谐运动条件下,推导出接口阻尼力的解析表达式和接口能量耗散的关系式。该式表明,轴向振动单位周期内的能耗包括粘性阻尼和干摩擦阻尼能耗两部分,这两部分能耗都与振动幅值和固有频率的平方成正比。粘性阻尼能耗与频率比和阻尼比成正比,干摩擦阻尼能耗与接触面峰-谷切向接触压力与总压力之比成正比,而与振动幅度和压缩位移比成反比,与接口的拉压刚度比成非线性关系。