固有振动

Firstly, this paper researched the mechanism of tubing string vibration when natural gas flows in horizontal well tubing string. Secondly, established whole tubing string undamped and damped vibration system model according as reasonable assumption data of one horizontal well. Apply finite element analysis software to calculate tubing string natural characters, simple harmonic dynamic behavior of stable gas production and nonlinear dynamic behavior. Finally, this paper carried out the safety varied frequency of gas well and the method of vibration reduction.

本文首先从理论和数值模拟研究了天然气在水平井油管柱内的流动诱发油管柱振动的机理，然后在合理假设的基础上结合某水平井数据建立了全井段油管柱无阻尼和有阻尼振动系统模型，利用有限元软件计算分析了油管柱固有特性、稳产简谐动力学响应和非线性动力学响应，针对油管柱振动规律提出了天然气安全调节频率范围和减振措施。

The thesis studied the woodworking tension band saw blades by means of the vibration theories,made sure the relationship between tension force and inhesion frequency of its system.

应用振动理论，对经过适张处理后的木工带锯条进行研究，确定张紧力与系统固有频率之间的关系，提出将带锯条的振动简化为弦的振动与受拉伸的梁振动。

The equations of dynamics for the balance are established by Kane's method, from which derives the characteristic equation of natural frequency by means of linearization of dynamic equations, and the six natural frequencies being developed according to the theory of vibration. The law of the six natural frequencies varying with mass of the upper platform and the stiffness of the elastic element are presented,and the Finite Element Method is employed to testify the validity of theoretical results.

基于 Kane 方法研究天平的动力学及模态，通过线性化动力学方程建立天平的固有频率方程，依据振动理论推导出并联天平的六阶固有频率及其对应的振型，同时研究了天平的六阶固有频率随敏感单元刚度系数及上平台质量的变化规律，并用有限元法验证理论计算结果的正确性。

The PZT plates were polarized in thickness direction. By using the deformation in the plane perpendicular to the direction of polarization, the rotation around Z axis was generated when the torsional vibration around Z axis mode was excited. And the rotation around X axis or Y axis was generated by combining the longitudinal vibration mode and the bending vibtration mode.

利用压电陶瓷在垂直极化方向平面内的变形，激励定子绕Z轴的扭转振动模态，实现转子绕Z轴的转动；激励在定子中固有频率接近、振动方向相垂直的伸缩振动模态和弯曲振动模态，并通过振动的叠加使定子末端质点产生绕X轴或者Y轴的椭圆运动，实现转子绕水平轴的转动。

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 results show that the vibration intensity of the substructure has a connection with the depth of the well, the geological condition and the density of drilling fluid; the horizontal vibration of the substructure is mainly caused by bent kelly; the included angle between the axis of cardan shaft and the derrick floor is also the cause of the vibration in three directions, and the cause of t...

分析结果表明，底座的振动强度与井深、地质条件和钻井液密度有关；弯曲的方钻杆是造成底座水平方向振动的最主要原因；万向轴因与钻台面存在夹角，从而引起底座在三个方向的振动；采用四挡钻进时，万向轴的工频及其倍频接近底座垂直方向的固有频率是引起底座在该方向振动强烈的原因。

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。

The method is as follows that the two ends of a nanometer are fixed on two pivots and an axial micro-pulling force T is applied on the nanometer; an electrode is arranged on the middle part of the side of the nanometer and an alternate voltage is applied on the electrode to motivate the nanometer to generate resonance, and therefore, the natural frequency f of the nanometer is measured and acquired; according to the material characteristics and the geometry characteristics of the nanometer as well as the boundary condition of the nanometer material, the relation between the natural frequency and the axial pulling force of the nanometer, namely the f-t curves of the nanometer, can be calculated by a vibration equation; according to the measured natural frequency f, the size of the micro-pulling force T can be acquired.

该方法将一根纳米材料的两端固定在两个支点上，给纳米材料施加一个轴向的微小拉力T；在纳米材料的侧面，位于该纳米材料的中部放置一个电极，在电极上施加一个交变的电压激励纳米材料使其发生共振，测得纳米材料的固有频率f；根据纳米材料的材料特性和几何特征以及纳米材料的边界条件，由振动方程计算出该纳米材料的固有频率与所受的轴向拉力的关系，即纳米材料的f-T曲线；根据上述测得的固有频率f，得到微小拉力T的大小。

The formula put together the natural frequency f s of shearing bending vibration of superstructure rigidly fixed on the hull and the natural frequency f r of rigid rotating vibration of superstructure elastically fixed on the hull, in which t...

推导中 ，仍将上层建筑整体纵向固有频率视为由下述两部分串联合成：上层建筑根部刚性固定在主船体上的剪弯振动固有频率 fs；上层建筑根部弹性固定在主船体上的刚体转动固有频率 fr。

This paper puts forward the method of using the vibrating isolation ring to reduce noise ,and advances the definite principle of the rigidity of the vibrating isolation ring and calculation formula.

提出了用隔振环来降低振动筛噪声的方法，以及隔振环刚度的确定原则和计算公式。分析了安装隔振环后，对振动筛固有频率影响不大，可保证工作频率是最高固有频率的两倍以上，可保证振幅不低于原振幅的98%，基本上不降低工作效率。

In the negative and interrogative forms, of course, this is identical to the non-emphatic forms.

。但是，在否定句或疑问句里，这种带有"do"的方法表达的效果却没有什么强调的意思。

Go down on one's knees;kneel down

屈膝跪下。。。下跪祈祷