饱和不可压多孔弹性板在面内扩散下的动力弯曲理论

根据多孔介质理论,在Kirchhoff假定和小变形前提下,针对流体的面内扩散情形,建立了饱和不可压多孔弹性板动力弯曲的数学模型.然后,利用Fourier展开法研究分析了阶梯载荷作用下四边简支透水矩形多孔弹性板的拟静定和动力弯曲响应,考察了不同参数下多孔弹性板的挠度、孔隙流体压力等效弯矩和固相有效应力等效弯矩的变化规律和特征.同时,通过基于Biot三维固结理论所建立的动力弯曲模型,比较了可压与不可压情况下其结果的差异.

粘弹性迭层板非线性动力弯曲问题的描述及建模

假设粘弹性迭层薄板的每一层都是各向同性的线性粘弹体 ,泊松比为常数 ,利用线性粘弹性理论中的Boltzmann叠加原理 ,由非线性几何方程和Karman方程 ,建立了线性粘弹性迭层薄板的非线性动力方程。这是一个二元积分 -非线性偏微分方程组。就粘弹性简支矩形迭层板 ,给出非线性动力初边值问题及方程组 ,并对粘弹性薄板这一特例用迭层板的方法进行了计算 。

饱和不可压正交各向异性多孔弹性板的动力弯曲分析

基于多孔介质理论,在Kirchhoff直法线假定以及小变形和线性本构关系前提下,建立了饱和不可压正交各向异性多孔弹性板的线性动力分析模型。针对流体的面内扩散问题,在忽略面内惯性项的影响下,进一步简化了分析模型,给出了相应的基本控制方程以及初始和边界条件的一般描述。根据所建立的模型,采用Fourier级数展开法研究了四边简支透水正交各向异性矩形多孔弹性板在冲击载荷作用下的拟静态和动力弯曲响应,数值分析了不同参数下孔隙流体压力等效弯矩、固相有效应力等效弯矩以及挠度的变化规律和动力特征。研究表明在外载荷作用初始阶段,孔隙流体对板弯曲变形的影响不可忽视。

预弯曲动力学防斜打快技术在塔里木盆地台前区应用研究

塔里木盆地直井段井斜不易控制,严重影响油气资源的经济高效开发。通过分析塔里木盆地台盆区井斜不易控制的地质原因,建立数学和数值计算模型优化设计预弯曲动力学防斜打快底部钻具组合和配套钻头,结合现场实际制定防斜打快施工方案。结果显示:志留系下部-桑塔木组等大倾角地层及裂缝广泛发育是直井易斜的主要地质原因;钻具组合弯角、弯角到下扶正器距离、弯角到上扶正器距离逐渐增大,降斜力先增大后减小最后趋于平稳,分别在0.9°~1.25°,0.5~0.7 m和4~6 m取得极值。PDC钻头造斜能力随保径长度和宽度的增加减弱,随保径倾角、内锥角、冠部旋转半径和高度的增大而增强。研究成果在塔里木盆地TK4-3X等井现场应用9口井,井斜控制良好,平均机械钻速较邻井同开次提高45.68%,实际钻井周期较设计周期累计节约周期105.64天,平均周期节约率21.43%。

饱和不可压正交各向异性多孔弹性大挠度板的动力弯曲模型

对于流体饱和不可压正交各向异性多孔弹性板,建立了大挠度弯曲模型,给出了相应的基本控制方程。模型中假设Kirchhoff直法线假定和线性本构关系成立,孔隙流体的运动服从Darcy定理并且仅在板平面内扩散。根据此模型,应用Galerkin截断法数值分析了四边简支透水多孔弹性矩形板在脉冲载荷作用下的非线性拟静态和动力弯曲响应。研究结果表明:大挠度弯曲模型能够反映出流体沿板厚度方向整体排水和吸水特性;当载荷增加到使所产生的挠度较大时,大挠度和小挠度弯曲模型对应结果之间的差别明显,且在拟静态响应中,大挠度弯曲模型下挠度和孔隙流体压力等效弯矩随时间的变化过程中存在有Mandel-Cryer效应,而小挠度弯曲模型下的对应结果不存在此效应。

预弯曲动力学防斜打快钻具组合动力学模型

建立了预弯曲动力学防斜打快钻具组合的动力学模型,对其动力学特性进行的仿真研究。结果表明,这种模型可以较好地反映出钻具组合在井下的涡动轨迹、涡动速度和涡动方向,同时能近似地计算出这种钻具组合的动态相对防斜力大小。钻具组合的涡动使得钻头对下井壁的动态侧向冲击力明显大于对上井壁的动态冲击力,从而使钻头具有较大的动态防斜力。通过合理设计结构参数和施工参数,可以有效地改善预弯曲动力学防斜打快钻具组合的涡动特征,从而使这种钻具组合具有较好的防斜效果。预弯曲动力学防斜打快技术的使用钻压比钟摆极限钻压提高50%以上,相应地提高了机械钻速。

粘弹性四边松散夹支薄板非线性动力响应

假设泊松比为常数 ,由Boltzmann叠加原理、非线性几何关系和Karman理论 ,建立了粘弹性薄板非线性动力方程和四边松散夹支各向同性粘弹性板动力弯曲的初边值问题及方程组 ,并用Galerkin法进行求解 。

二维线性动力学Koiter型弹性壳方程解的渐近分析

在一定条件得到了二维线性动力学膜壳方程和二维线性动力学弯曲壳方程.

杆件纵横弯曲振动性能的研究

研究了纵横弯曲杆件的动力性能 ,推导出了纵横弯曲杆件的振幅计算公式 ,并分析了激振参数对杆件动力性能的影响 ,提出了在实际工程中减小杆件振动的一些措施。

防斜打快技术的研究与发展

直井眼的防斜打快技术是目前国内外石油钻井急需的一项关键技术 .国内以钟摆防斜降斜技术和偏轴防斜技术为主 ,但无法解决这一难题 .国外的先进工具可以解决这一难题 ,但成本太高 .预弯曲动力学防斜打快技术通过控制钻具组合的有序变形 ,利用其动力学行为实现防斜打快目的 .本文认为 ,这项技术有望成为未来实用的防斜打快新技术 .

弱引力场中Einstein引力波简介

本文作为对近期证实引力波存在的响应,给出了Einstein引力波一个简单介绍,主要讨论了线性化引力场方程及其解的波动特性,从而对引力波的时-空涟漪特征作了一个数学描述.

塔里木油田台盆区Φ241．3mm井眼控移快钻技术研究

塔里木油田台盆地区241.3mm井眼介于1500～6600m之间,存在井段长、井段位移控制要求高的特点,从而束缚了钻井速度的提高。文章在分析各井段钻井特征的基础上,提出在中下部井段采用预弯曲动力学控移快钻技术方案,在优化设计BHA的前提下进行了一口井的现场试验。结果表明,该方法不但可以较好地控制井斜,而且可以较大幅度提高钻井速度。与邻井相比,试验井段的平均机械钻速比邻井平均机械钻速提高62.1%。

Combined effects of local curvature and elasticity of an isothermal wall for jet impingement cooling under magnetic field effects

The aim of this study is to examine the effects of local curvature and elastic wall effects of an isothermal hot wall for the purpose of jet impingement cooling performance.Finite element method was used with ALE.Different important parametric effects such as Re number(between 100 and 700),Ha number(between 0 and 20),elasticity(between 104 and 109),curvature of the surface(elliptic,radius ratio between 1 and 0.25) and nanoparticle volume fraction(between 0 and 0.05) on the cooling performance were investigated numerically.The results showed that the average Nu number enhances for higher Hartmann number,higher values of elastic modulus of partly flexible wall and higher nanoparticle volume fraction.When the magnetic field is imposed at the highest strength,there is an increase of3.85% in the average Nu for the curved elastic wall whereas it is 89.22% for the hot part above it,which is due to the vortex suppression effects.Nanoparticle inclusion in the base fluid improves the heat transfer rate by about 27.6% in the absence of magnetic field whereas it is 20.5% under the effects of magnetic field at Ha=20.Curvature effects become important for higher Re numbers and at Re=700,there is 14.11% variation in the average Nu between the cases with the lowest and highest radius ratio.The elastic wall effects on the heat transfer are reduced with the increased curvature of the bottom wall.

Stress Analysis of Top Tensioned Riser Under Random Waves and Vessel Motions

The bending stresses of top tensioned riser(TTR) under combined excitations of currents,random waves and vessel motions are presented in this paper,and the effect of the internal flowing fluid on the riser stresses is also considered.The computation programs which are used to solve the differential equations in the time domain are compiled and the principal factors of concern including the angular movements at the upper and lower ends of the riser,lateral displacements and bending stresses are presented.Then the effects of current velocity,random wave,top tension,vessel mean offset,low frequency motion and internal flow velocity on the bending stresses of the riser are analyzed in detail.

Bending stress of rolling element in elastic composite cylindrical roller bearing

A new structure design method of elastic composite cylindrical roller bearing is proposed, in which PTFE is embedded into a hollow cylindrical rolling element, according to the principle of creative combinations and through innovation research on cylindrical roller bearing structure. In order to systematically investigate the inner wall bending stress of the rolling element in elastic composite cylindrical roller bearing, finite element analysis on different elastic composite cylindrical rolling elements was conducted. The results show that, the bending stress of the elastic composite cylindrical rolling increases along with the increase of hollowness with the same filling material. The bending stress of the elastic composite cylindrical rolling element decreases along with the increase of the elasticity modulus of the material under the same physical dimension. Under the same load, on hollow cylindrical rolling element, the maximum bending tensile stress values of the elastic composite cylindrical rolling element after material filling at 0° and 180° are 8.2% and 9.5%, respectively, lower than those of the deep cavity hollow cylindrical rolling element. In addition, the maximum bending-compressive stress value at 90° is decreased by 6.1%.

Experimental study on pressure fluctuation characteristics of slug flow in horizontal curved tubes

In order to study the pressure characteristics of slug flow in horizontal curved tubes,two kinds of curved tubes with central angle 45° and 90° respectively are studied,of which are with 0. 5m circumference and 26 mm inner diameter are used. When the superficial liquid velocity or the superficial gas velocity is constant,the pressure fluctuations and the probability distribution of the average velocity of slug flow are clear for all of the five experimental conditions. The results of experiment show that the pressure characteristics of slug flow in curved tubes have periodic fluctuations. With the rise of central angle,the period of pressure fluctuation is more obvious. The system pressure of the slug flow increases with the increasing of superficial liquid/gas velocity. Meanwhile,the probability distribution of pressure signal shows regularity,such as unimodal,bimodal or multimodal.

The theoretical analysis of dynamic response on cantilever beam of variable stiffness

The paper presents the theoretical analysis of a variable stiffness beam. The bending stiffness EI varies continuously along the length of the beam. Dynamic equation yields differential equation with variable co- efficients based on the model of the Euler-Bernoulli beam. Then differential equation with variable coefficients becomes that with constant coefficients by variable substitution. At last, the study obtains the solution of dy- namic equation. The cantilever beam is an object for analysis. When the flexural rigidity at free end is a constant and that at clamped end is varied, the dynamic characteristics are analyzed under several cases. The results dem- onstrate that the natural angular frequency reduces as the fiexural rigidity reduces. When the rigidity of clamped end is higher than that of free end, low-level mode contributes the larger displacement response to the total re- sponse. On the contrary, the contribution of low-level mode is lesser than that of hi^h-level mode.

Aerodynamic performance of high-turning curved compressor cascade with boundary layer suction

The impact of boundary layer suction on the aerodynamic performance of a high-turning compressor cascade was numerically simulated and discussed.The aerodynamic performance of a curved and a straight cascade with and without boundary layer suction were comparatively studied at several suction flow rates.The results showed that boundary layer suction dramatically improved the flow behavior within the flow passage.Moreover,higher loading over the whole blade height,lower total pressure loss,and higher passage throughflow were achieved with a relatively small amount of boundary layer removal.The integration of curved blade and boundary layer suction contributed to better aerodynamic performance than the cascades with only curved blade or boundary layer suction used,and the more favorable effect resulted from the weakening of the three dimensional effects of the boundary layer close to the endwalls.

Forced transverse vibration of rolls for four-high rolling mill

In order to investigate the forced transverse vibration of rolls under distributed draught pressure and moment of bending roll force, the forced transverse vibration model of rolls for four-high rolling mill was established. The work roll and backup roll were considered as elastic continuous bodies that were joined by a Winkler elastic layer. According to Euler-Bemoulli beam theory, the forced transverse vibration of rolls was analyzed based on modal superposition method. The forced vibration equations were established when the draught pressure and moment of bending roll force were imposed on the rolls respectively. Numerical modeling was made on 2 030 mm cold tandem rolling mill of Baoshan Iron and Steel Company. Simulation results show that when the work roll is only subjected to different forms of draught pressures, the vibration curves of work roll and backup roll are quadratic curves with amplitudes of 0.3 mm and 45 μm, respectively. When only the moments of bending roll force are imposed on the work roll and backup roll, the vibration curves of work roll and backup roll are quadratic curves, and the amplitudes are 5.0 and 1.6 μm, respectively. The influence of moment of bending roll force on the vibration of work roll is related with the bending roll force.

AN EXPERIMENTAL STUDY ON DYNAMIC FRACTURE SPEED

This paper deals with an experimental study on dynamic fracture speed of three point bending specimen and cylindrical specimen made of epoxy resin by means of silver conductive painting grid. According to the test results ,the relations between fracture load ,fracture speed and loading speed are discussed and the features of final fracture surfaces are analysed in detail.