THEORETICAL INVESTIGATION ON STATE OF LOAD DISTRIBUTION AMONG CONTACT BEARINGS OF DOUBLE CIRCULAR ARC HELICAL GEARS

A dynamic analysis approcach to investigate the state of load distribution among contact bearings of double circular are belical gears is proposed and a computer program is developed for calculating the factor of iced distribution based on the theory of W-N gears. The changing situations of load distribution among contact bearings of the gears influenced by main issues are analyzed by a series of parametric studies.

NON-LINEAR DYNAMIC BEHAVIOR OF THERMOELASTIC CIRCULAR PLATE WITH VARYING THICKNESS SUBJECTED TO NONCONSERVATIVE LOADING

The non-linear dynamic behaviors of thermoelastic circular plate with varying thickness subjected to radially uniformly distributed follower forces are considered. Two coupled non-linear differential equations of motion for this problem are derived in terms of the transverse deflection and radial displacement component of the mid-plane of the plate. Using the Kantorovich averaging method, the differential equation of mode shape of the plate is derived, and the eigenvalue problem is solved by using shooting method. The eigencurves for frequencies and critical loads of the circular plate with unmovable simply supported edge and clamped edge are obtained. The effects of the variation of thickness and temperature on the frequencies and critical loads of the thermoelastic circular plate subjected to radially uniformly distributed follower forces are then discussed.

THE PROBLEM OF AN EXTERNAL CIRCULAR CRACK UNDER ASYMMETRIC LOADINGS

Using the boundary integral equation method, the problem of an external circular crack in a three_dimensional infinite elastic body under asymmetric loadings is investigated. The two_dimensional singular boundary integral equations of the problem were reduced to a system of Abel integral equations by means of Fourier series and hypergeometric functions. The exact solutions of stress intensity factors are obtained for the problem of an external circular crack under asymmetric loadings, which are even more universal than the results obtained by the use of Hankel transform method. The results demonstrate that the boundary integral equation method has great potential as a new analytic method.

Load eccentricity effects on behavior of circular footings reinforced with geogrid sheets

In this paper, an experimental study for an eccentrically loaded circular footing, resting on a geogridreinforced sand bed, is performed. To achieve this aim, the steel model footing of 120 mm in diameterand sand in relative density of 60% are used. Also, the effects of depth of first and second geogrid layersand number of reinforcement layers （1e4） on the settlement-load response and tilt of footing undervarious load eccentricities （0 cm, 0.75 cm, 1.5 cm, 2.25 cm and 3 cm） are investigated. Test results indicatethat ultimate bearing capacity increases in comparison with unreinforced condition. It is observed thatwhen the reinforcements are placed in the optimum embedment depth （u/D ？0.42 and h/D ？0.42）, thebearing capacity ratio （BCR） increases with increasing load eccentricity to the core boundary of footing,and that with further increase of load eccentricity, the BCR decreases. Besides, the tilt of footing increaseslinearly with increasing settlement. Finally, by reinforcing the sand bed, the tilt of footing decreases at 2layers of reinforcement and then increases by increasing the number of reinforcement layers.

NONLINEAR VIBRATION OF CIRCULAR SANDWICH PLATE UNDER THE UNIFORMED LOAD

The differential equations of the axisymmetric large amplitude free vibration for circular sandwich plates under static load are derived, and a set of nonlinearly coupled algebraic and differential eigenvalue equations of the problem are formulated following an assumed time mode approach suggested. The analytic solutions are presented and a relation for amplitude frequency-load of the plates with edge clamped is derived by modified iteration method. The effects of static load on vibrations of plates are investigated.

Study on Deformation Law of Circular Foundation Under Combined Loading

The foundations of some ocean engineering structures are built to withstand not only the vertical gravity load V, but also the horizontal load H induced by sea waves and current. The horizontal load includes the concentrated force load, the moment load M, and the torque load T termed also as combined loading. It is of academic and engineering significance to study the deformation law of submarine seabed due to combined loading. On the basis of the three-dimensional elastic mechanics solution of circular foundation, numerical methods are used to analyze the deformation law of submarine soil under circular foundation with six degrees of freedom. The finite element analysis results give the elastic deformation law of soil in three dimensional spaces, modify the theoretical elasticity solution, and presents nonlinear soil deformation mechanism under the circular foundation with six degrees of freedom.

Nonlinear Resonance of the Rotating Circular Plate under Static Loads in Magnetic Field

The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating circular plate under static loads in magnetic field, the nonlinear vibration equation about the spinning circular plate is derived according to Hamilton principle. The algebraic expression of the initial deflection and the magneto elastic forced disturbance differential equation are obtained through the application of Galerkin integral method. By mean of modified Multiple scale method, the strongly nonlinear amplitude-frequency response equation in steady state is established. The amplitude frequency characteristic curve and the relationship curve of amplitude changing with the static loads and the excitation force of the plate are obtained according to the numerical calculation. The influence of magnetic induction intensity, the speed of rotation and the static loads on the amplitude and the nonlinear characteristics of the spinning plate are analyzed. The proposed research provides the theory reference for the research of nonlinear resonance of rotating plates in engineering.

Nonlinear vibration and buckling of circular sandwich plate under complex load

The nonlinear vibration fundamental equation of circular sandwich plate under uniformed load and circumjacent load and the loosely clamped boundary condi- tion were established by von Karman plate theory, and then accordingly exact solution of static load and its numerical results were given. Based on time mode hypothesis and the variational method, the control equation of the space mode was derived, and then the amplitude frequency-load character relation of circular sandwich plate was obtained by the modified iteration method. Consequently the rule of the effect of the two kinds of load on the vibration character of the circular sandwich plate was investigated. When circumjacent load makes the lowest natural frequency zero, critical load is obtained.

THE PROBLEM OF AN EXTERNAL CIRCULAR CRACK UNDER ASYMMETRIC LOADINGS

Using the boundary integral equation method, the problem of an external circular crack in a three-dimensional infinite elastic body under asymmetric loadings is investigated. The two-dimensional singular boundary integral equations of the problem were reduced to a system of Abel integral equations by means of Fourier series and hypergeometric functions. The exact solutions of stress intensity factors ore obtained for the problem of an external circular crack under asymmetric loadings, which are even more universal than the results obtained by the use of Hankel transform method. The results demonstrate that the boundary integral equation method has great potential as a new analytic method.

AXISYMMETRIC BENDING FOR THICK LAMINATED CIRCULAR PLATE UNDER A CONCENTRATED LOAD

Based upon the fundamental equations of three dimensional elasticity, the state equation for axisymmetric bending of laminated transversely isotropic circular plate is established and the concentrated force on plate surface is expanded into Fourier_Bessel's series, therefore, an analytical solution for the problem is presented. Every fundamental equation of three dimensional elasticity can be exactly satisfied by the solution and all the independent elastic constants can be taken into account fully, furthermore, the continuity conditions between plies can also be satisfied.

LARGE DEFLECTION PROBLEM OF CIRCULAR PLATES WITH VARIABLE THICKNESS UNDER THE ACTION OF COMBINED LOADS

By using the modified iteration method of large deflection theory of plates with variable thichness[1], we solve the problem of circular plates with variable thickness subjected to combined loads under the boundary conditions of the clamped edges and get comparatively more accurate second-order approximate analytical solution. If the results of this paper are degraded into the special cases, the results coinciding with those of papers [1,2] can be obtained. In this paper, the characteristic curves are plotted and some comparisons are made. The results of this paper are satisfactory.

EFFECT OF GEAR WIDTH AND HELIX ANGLE ON FACTOR OF DYNAMIC LOAD OF DOUBLE CIRCULAR ARC HELICAL GEARING

Based on theory of mechanical dynamics, meshing characteristic as well as thedynamic model of double circular arc helical gearing, an analysis approach and a computer programhave been developed for studying the state of dynamic load and factor of dynamic load of thegearing, the changing situation of dynamic load and dynamic load factor vs some affecting factorssuch as gear width, helix angle and accuracy grade etc are investigated. A series of conclusions areobtained: ①With the increasing in the values of gear width, the dynamic load factor appears slowdecreasing tendency in most region of gear width. ②When the accuracy grades of the gearing areimproved, the values of dynamic load factor decrease. ③The value of dynamic load factor appears adecreasing tendency with the increasing of value of helix angle at the same ratio of criticalrotational speed.

局部锈蚀圆钢管混凝土短柱轴压承载力试验研究

钢管混凝土(CFST)在服役环境中被腐蚀,导致其钢结构承载力降低,严重威胁到结构的服役性能和使用寿命。首先,采用机加工车铣方法制作模拟局部锈蚀的人工缺陷,然后以钢管外表面局部环向贯通锈蚀位置、锈蚀钢管体积损失率、锈蚀外表面面积损失率(简称锈蚀面积损失率,下同)为试验参数,对45根局部锈蚀圆CFST短柱试件进行轴压承载力试验;其次,分析锈蚀位置、锈蚀钢管体积损失率、面积损失率和壁厚损失率对锈蚀试件承载力、刚度和延性的影响,揭示锈蚀CFST试件破坏机理和承载力退化机制;最后,针对局部锈蚀圆CFST短柱构件轴压承载力提出一个简化实用计算公式。研究结果表明:各试件具有类似的破坏特征,主要呈明显的腰鼓状破坏,且发生在锈蚀区;随着锈蚀钢管体积损失率增大,锈蚀CFST柱的承载力、刚度和延性均出现不同程度的降低;在锈蚀钢管体积损失率和面积损失率相同的情况下,就局部锈蚀位置影响而言,中部影响最大;就锈蚀程度表征参数影响而言,锈蚀钢管体积损失率影响最大,面积损失率次之,壁厚损失率最小;本文提出的简化实用公式可为圆钢管混凝土构件全寿命设计提供参考依据。

安装误差对双圆弧齿轮啮合特性影响分析

为深入研究安装误差对双圆弧齿轮副啮合特性的影响,基于有限元法建立齿轮加载分析模型,研究啮合过程中单齿凸、凹齿廓的接触性能,对比分析安装误差对接触性能以及传动误差的影响规律。结果表明:啮合周期内,双圆弧齿轮的凹齿廓先接触且承担较大的法向接触力,但凸齿廓的啮入端接触应力最大,凸、凹齿面接触压力差与转矩成正比;安装误差对齿面接触性能影响较大,其中中心距误差容易引起齿轮分阶处应力集中,轴线平面的安装误差会引起齿面接触偏载,且对安装误差影响最大。

火灾后圆形孔蜂窝组合梁受力性能研究

圆形孔蜂窝组合梁火灾后的力学性能研究,可为受火后建筑结构性能评估提供参考依据。对4根火灾后圆形孔蜂窝组合梁及1根未过火处理圆形孔蜂窝组合梁开展静力加载试验,分析火灾、加劲肋设置、开孔率等因素对圆形孔蜂窝组合梁破坏形态、抗弯刚度及承载能力的影响。结果表明:降低开孔率可以提高火灾后圆形孔蜂窝组合梁的抗弯刚度和极限承载能力;设置加劲肋的火灾后圆形孔蜂窝组合梁与未设置加劲肋的构件相比,其极限承载能力提高了6.9%;火灾前、后,圆形孔蜂窝组合梁在静力荷载作用下均发生弯曲破坏,但火灾后其开裂荷载、极限承载能力和延性均出现不同幅度的下降;提出了具有良好精度的圆形孔蜂窝组合梁火灾后剩余抗弯承载力的计算方法。

模型冰水平圆盘中心加载弯曲强度试验研究

由各种垂直施力引起的冰层破坏是极地探索和利用活动中重要的工程场景,而冰强度特性对于活动于此区域的平台的结构强度和安全操控的设计评估有直接影响。本文依托中国船舶科学研究中心小型冰水池,制作盐水柱状模型冰,开展模型冰水平圆盘中心加载试验。试验对环向外沿均布支撑下的水平圆盘冰样中心区域垂直加载,利用测力系统记录冰样从起始承载直至弯曲破坏的力值曲线,根据受力峰值求取冰样破坏时的弯曲强度,利用影像系统捕捉冰样破坏失效细节,分析冰样承载失效过程。在此基础上,改变加载速度和冰样温度,开展系列试验测量,分析两个因素对模型冰弯曲强度的影响。本文工作为测量分析模型冰强度特性补充了一种可行手段,也为深入研究冰区结构物与冰层垂直作用机理和冰载荷形成机制建立了初步基础。

圆钢管型钢再生混凝土组合柱水平承载力计算方法研究

通过对11个圆钢管型钢再生混凝土组合柱进行低周反复荷载试验,分析再生粗骨料取代率、型钢截面形式、轴压比、型钢配钢率及圆钢管壁厚参数对组合柱水平承载力的影响规律;观察了组合柱的破坏形态及特征,研究了圆钢管、型钢翼缘及腹板应变的发展规律,分析了组合柱的地震破坏特征。研究表明,在水平地震作用下组合柱发生典型的压弯塑性铰破坏。在此基础上,结合现有规范提出了基于叠加原理的圆钢管型钢再生混凝土组合柱水平承载力计算方法。计算结果表明,其水平承载力计算值与试验值吻合度较好,能较为准确地预测组合柱的水平承载力。

福建圆形土楼悬挑屋盖风荷载特性及气动抗风措施研究

福建圆形土楼悬挑屋盖属于风敏感结构,且处于我国台风多发区,为提升结构的风灾防御水平,保障其抗风安全,采用CFD数值模拟方法对屋盖表面风荷载分布特性进行研究,同时提出了增强其抗风性能的气动抗风措施。研究表明:圆形土楼悬挑屋盖迎风面风压较大,其中,内、外悬挑屋盖端部风压系数绝对值最大,分别达到1.5和0.75,属于风荷载敏感部位;在外悬挑屋盖端部加设竖直挡风板和波纹挡风板均可以一定程度地卸载上述风荷载敏感部位的风压值,综合比较,设置波纹挡风板较竖直挡风板对风压卸载效果更好;对于设置波纹挡风板,当其相对高度h/Hj=0.05(h为波纹挡风板高度,Hj为地面到屋脊处距离)、倾角θ=-45°、波纹圆弧半径R=5.5 m时整体对屋盖表面风压卸载效果最优,其内、外悬挑屋盖端部风压系数卸载率分别达到40.1%和54%,原因在于倾斜布置的波纹挡风板对悬挑屋盖表面来流起到阻挡作用,使得气流撞击形成的漩涡从屋盖悬挑端转移到挡风板表面,同时波纹的存在降低了内、外悬挑屋盖表面气流漩涡强度,从而达到卸载屋面风荷载的效果。

基于空间距离改进的航线网络级联失效模型

为准确分析航线网络在多种干扰事件影响下的级联失效过程,首先,对以往研究的节点过载、节点状态识别和节点负载-容量关系三个部分进行整合,引入容量参数α、β和过载系数γ,建立一个综合性的航线网络级联失效模型;在此基础上,考虑实际空间距离因素,对传统的全局负载重分配策略进行改进,提出以丧失运输功能的机场为圆心、实际k倍平均航线里程为半径的圆形负载重分配策略。然后,以国内航线网络为例,开展随机、蓄意两种攻击策略下的仿真。结果表明:基于空间距离的负载重分配策略更具有普适性,即传统全局负载重分配策略仅是其中一个特例;同时,航线网络级联失效结果与负载分配半径密切相关,确定合理的负载分配半径,对缓解航线网络级联失效影响有重要意义。

游梁式抽油机非圆齿轮传动设计与节能分析

[目的]针对游梁式抽油机存在系统效率低、能耗高、负载波动大的不足,对基于非圆齿轮传动的游梁式抽油机节能设计方案进行研究.[方法]在考虑非圆齿轮传动条件及其与曲柄载荷匹配原则的基础上,选取最优非圆齿轮节曲线,形成非圆齿轮节曲线的节能设计准则.通过仿真分析,获得不同非圆节曲线对应的能耗值,筛选出最低能耗对应的非圆节曲线,并结合CYJY10-4.2-53HB型号游梁式抽油机进行仿真和实验验证.[结果]1)仿真结果得到在同功率电机下耗能降低4.7%,在更小功率电机下耗能降低11%,与实验结果基本一致;2)基于非圆齿轮传动的游梁式抽油机,可大幅度降低抽油机输入轴的扭矩峰值和扭矩波动,降低能耗,实现节能.[结论]从节能和降低负载波动的角度来看,非圆齿轮传动对于圆柱齿轮更有优势.