固有频率

In the part of the vibration experiments and analysis, firstly, used the simple-beam theory to estimate the natural frequency of the beam of the 20-headed computerized embroidery machine.secondly, measured the beam of its low rank natural frequency, the beams horizontal vibrating acceleration amplitude, speed amplitude and the displacement amplitude in different rev and different turn parts. Found that it is sympathetic vibration, which bring on the thread-broken rate rise rapidly. On this base, established the finite element analysis modle of the vibrating beam, and took on hamonic analysis and modal analysis with the mold. The rusult of test and analysis offer the basis for farther improvement of the computerized embroidery machine.

振动分析部分，首先由简单梁理论出发，对横梁的固有频率进行估算；接着通过测振仪器对20头电脑刺绣机横梁进行了试验模态分析和不同工况振动测试；获得了横梁前四阶固有频率和模态振型，以及在不同工作转速、不同回转部件下横梁振动的加速度幅值、速度幅值和位移幅值；找到了横梁振动加剧的原因——共振；在此基础上建立了符合实际情况的横梁有限元模型，对模型进行了模态和谐响应计算，证实了模型的可靠性，为下一步的改进设计提供了依据。

It follows that the natural frequences of complete system not only reflect the natural frequences of elastic beam tail ro...

由此得到的整个系统的固有频率，既包含了弹性梁在真实动态支承条件下的固有频率，又揭示了该部件对支承基础的反作用。

The phase of ω0 frequency fluctuates tempestuously. The resonance peaks of flexural and torsional vibrations response are present at 2/3ω0 1/2ω0 1/3ω0 and 1/4ω0 with three kinds cracked rotor models. Near 1/2ω0 frequency, quasi-periodic and chaotic motions maybe appear. Periodic, quasi-periodic and chaotic motions show on alternately when the rotating speed is near to 2/3ω0.Combined step-by-step integral method with traditional transfer matrix method, an increment transfer matrix method is put forward.

研究结果表明：各种故障情况下，华北电力大学博士学位论文弯振和扭振之间都存在祸合关系，但弯扭祸合振动一般不会威胁机组安全运行：在叶片丢失或滑环飞脱故障时，将产生很大的弯振，同时各转子扭振也将被激发出来，它以工倍频和前三阶固有频率为主；在各种电气故障情况下，各转子都很快被激励出较大幅值的扭振来，相应各转子弯振也发生一定的变化，但它的变化明显滞后于扭振，扭振和扭矩主要以前三阶固有频率为主。

The responses properties of coupled vibrations for 120° and 180°asynchronous juxtaposition of 200MW turbine-generator set were analyzed. The results show that the responses properties of flexural and torsional vibrations caused by 120° asynchronous juxtaposition are similar to that of 180° asynchronous juxtaposition. When the fault happened, Former two steps inherence frequencies and whirl speed frequency of torsion are excited. And the first step inherence frequencies of flexural vibration are also excited besides whirl speed frequency. Transient electromagnetism moment peak, torsional and torsional moment responses caused by 180° asynchronous juxtaposition are lower than that of 120° asynchronous juxtaposition.

利用该方法，针对某200MW汽轮发电机组的120°和180°两种非同期并列情况，进行了机组弯扭耦合振动响应特性研究，分析表明：汽轮发电机组的120°和180°两种非同期并列情况下的弯振和扭振响应特性基本相似；非同期并列主要激发出工频和前两阶固有频率扭振，弯振除工频主分量外，第一阶固有频率也被激发出来；180°非同期并列时的暂态电磁力矩峰值比120°非同期并列时低，相应的扭振和扭矩响应也小于后者。

In ground testing research of some large airplane and aerocraft, suspend structure of sky need to be simulated. As a lower natural frequency and a good underprop, air spring can satisfy the need of the testing research. In this paper, a calculating model of air spring was built by ABAQUS.

一些大型的飞机，航天器等在做地面试验的时候，需要模拟空中的悬浮结构，由于自身的固有频率比较低，所以需要更低固有频率的支撑物，而空气弹簧正好可以满足试验的需要。

The distribution of gear's contact stress, root stress, and contact engagement line in the engagement situation of gear pairs, were obtained on the base of explicit integration method. 3. Adopting the method of system matrix, the torsional vibration differential equation of general shafting was gained. The simple harmonic forms of excitation torque under the normal combustion or piston flameout of in-line engine and v-type engine were analysed. The decoupled algorithm of free vibration and forced vibration and the solution to the vibration damper's energy of resistance and the off-resonance calculation were studied. The sensitivity formulations of the natural frequency and vibration mode to physical parameters of system were derived by solving the eigenvalue problem. These sensitivity formulations provided the theoretical base for the dynamic modification of structure.

运用系统矩阵法建立了轴系的扭振微分方程，并对直列和V型发动机在正常发火和气缸熄火工况下的激振力矩进行了详细的简谐分析；基于精确方法推导了自由振动和强迫振动的解耦算法，给出了能量法计算中的减振器阻尼功求解和非共振计算方法；并研究了曲轴系扭振非线性分析中的变惯量问题，得到了单缸转动惯量的精确求解公式以及变惯量和固有频率的关系式；最后，从特征方程和振型正交性出发，推导了固有频率和振型对轴系转动惯量和刚度等物理参数的灵敏度，为扭振系统的结构动力学修改提供了理论基础。

The thesis advances a new optimality design method which can consider stress and proper frequency restriction condition synthetically, through basing on stress optimality criteria methods, owing to optimality criteria don't relate to multi-constraint and apply incomprehensively.

本文针对优化准则法不能考虑多种优化约束条件、通用性差的缺点，基于应力优化准则法和固有频率优化准则法，提出了一种可以综合考虑设计模型的应力约束条件和固有频率约束条件的优化设计方法。

In the buckling question under nonconservation force,a simply example( the dynamic stability question under the uniformly follower forces with small deformation % linear elastic, straight normal.) is considered.The variational equation of braid composite cylindrical shells subjectd to uniformly follower forces is deduced based on the variation principle of quasinatural frequency of elastic nonconservative system self-excited vibration.The calculated formulas of the flutter load and quasinatural frequency of shells are obtained. The program for calculating the flutter load is developed.The numerical example is given and some useful conclusions are obtained.

对非保守力作用下的屈曲问题，具体研究了圆柱壳在比较简单的情况，即小变形、线弹性、直法线假设下在随动力作用下的壳屈曲问题，由拟固有频率变分原理推出了圆柱壳受随从力作用的变分方程，得到了颤振载荷与壳弯曲的固有频率的计算公式，编制了相应的计算机程序，并给出了具体算例，得到了一些有益的结论。

Finite element method is based on the actual ship models, a true reflection of the real ship distribution of the specific structure. This paper also uses empirical formula to calculate the inherent frequency of the catamaran; contrast them in the process of modeling the structural stiffness, and quality of the different treatments, as well as natural frequency calculated from the results of differences analyze the different and the reason between the finite method and the empirical formula method which used to calculate the inherent frequency of catamarans in the vibration analysis.

有限元方法是根据实际船型，较真实的反映了实船结构的具体分布特征；本文还采用经验公式对该船的固有频率进行了计算，对比它们在建模过程中对结构刚度、质量的不同处理，以及计算所得固有频率结果的差异，分析了在双体船振动特性分析中有限元法与经验公式法的结果略有差距及其原因。

Effects of the downhole temperature on axial vibration natural frequency of drill string in deep wells is investigated.

分析了井下温度对钻柱轴向振动固有频率的影响，推导出了井下任意温度时钻柱轴向振动固有频率的计算公式。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。