Preset model of bending force for 6-high reversing cold rolling mill based on genetic algorithm

The hydraulic roll-bending device was studied, which was widely used in modem cold rolling mills to regulate the strip flatness. The loaded roll gap crown mathematic model and the strip crown mathematic model of the reversing cold rolling process were established, and the deformation model of roll stack system of the 6-high 1 250 mm high crown （HC） reversing cold rolling mill was built by slit beam method. The simulation results show that, the quadratic component of strip crown decreases nearly linearly with the increase of the work roll bending force, when the shifting value of intermediate roll is determined by the rolling process. From the first pass to the fifth pass of reversing rolling process, the crown controllability of bending force is gradually weakened. Base on analyzing the relationship among the main factors associated with roll-bending force in reversing multi-pass rolling, such as strip width and rolling force, a preset mathematic model of bending force is developed by genetic algorithm. The simulation data demonstrate that the relative deviation of flatness criterions in each rolling pass is improved significantly and the mean relative deviation of all five passes is decreased from 25.1% to 1.7%. The model can keep good shape in multi-pass reversing cold rolling process with the high prediction accuracy and can be used to guide the production process.

Contact force and mechanical loss of multistage cable under tension and bending

A theoretical model for calculating the stress and strain states of cabling structures with different loadings has been developed in this paper. We solve the problem for the first- and second-stage cable with tensile or bending strain. The contact and friction forces between the strands are presented by two-dimensional contact model. Several theoretical models have been proposed to verify the results when the triplet subjected to the tensile strain, including contact force, contact stresses, and mechanical loss. It is found that loadings will affect the friction force and the mechanical loss of the triplet. The results show that the contact force and mechanical loss are dependent on the twist pitch. A shorter twist pitch can lead to higher contact force, while the trend of mechanical loss with twist pitch is complicated. The mechanical loss may be reduced by adjusting the twist pitch reasonably. The present model provides a simple analysis method to investigate the mechanical behaviors in multistage-structures under different loads.

Tunable Bending Stiffness, Buckling Force, and Natural Frequency of Nanowires and Nanoplates

This paper aims to obtain the simple closed-form results for the combined effects of surface elasticity, initial stress/ strain, and material Poisson ratio on the bending stiffness, natural frequency and buckling force of nanowires and nano-plates. The results demonstrate that all these properties of nanowires or nanoplates can be designed either very sensitive or not sensitive at all to the amplitude of an applied electric potential;show how much of those properties can be controlled to vary;and thus provide a reliable guide to the measurement of the Young’s modulus of nanowires/nanoplates and to the design of nano-devices, such as nano-sensors or the cantilever of an AFM.

New Insights on the Deflection and Internal Forces of a Bending Nanobeam

Nanowires, nanofibers and nanotubes have been widely used as the building blocks in micro/nano-electromechanical systems, energy harvesting or storage devices, and small-scaled measurement equipment. We report that the sur- face effects of these nanobeams have a great impact on their deflection and internal forces. A simply supported nanobeam is taken as an example. For the displacement and shear force of the nanobeam, its dangerous sections are different from those predicted by the conventional beam theory, but for the bending moment, the dangerous section is the same. Moreover, the values of these three quantities for the nanobeam are all distinct from those calculated from the conventional beam model. These analyses shed new light on the stiffness and strength check of nanobeams, which are beneficial to engineer new-types of nano-materials and nano-devices.

Effect of Ground Stack for Additional Internal Force and Deformation of Underground Pipeline

Based on a three-dimensional finite element model of an underground pipeline,the influence of additional ground loads on the stress characteristics of the pipeline was studied.Furthermore,the effects of different soil properties,load locations,and varying burial depths on the pipeline’s stress characteristics were analyzed.The research results show that as the distance between the load center and the pipeline axis increases,the positions of the pipe’s maximum displacement,bending moment,and shear force along the axis decrease significantly.However,when this distance reaches a certain value,the pipeline’s maximum vertical displacement and internal forces approach zero.Different pipelines exhibit minimum values of maximum axial displacement and vertical displacement in soft soil,while maximum axial displacement occurs in clay,and the largest vertical displacement is observed in sandy soil.The maximum axial displacement of UPVC pipes in clay is twice that of soft soil.The vertical displacement of pipes made from different materials increases with burial depth,but for concrete and steel pipes,the maximum axial tension increases significantly with depth,whereas the change in UPVC pipes is more gradual.

Analysis of bending on the front end of sheet during hot rolling

The analysis of bending in finishing rolling was performed. An asymmetrical rolling force model was established, and the upper and lower neutral points were determined. Thc bending which resulted from the asymmetrical rolling force at the roll gap was studied and related flexibility equations were proposed according to elastic mechanics. Moreover, material mechanics was used to analyze the effects of temperature difference and self-weight on the bending out of the roll gap, and the flexibility equations were constructed. The main factors on bending were summed up, and the bending rule in the rolling could be obtained. In addition practical calculation was made with the production data of ribbon steel from Laiwu Iron ＆ Steel Group Co. Ltd.

An Experimental Study of Several Special Issues Regarding the Ice Force on Conical Structures

The effect of the cone spacing of a conieal structure on the ice force is studied by model experiments. The ice force reduction coefficient presented in this paper expresses the relationship between the ice force and the arrangement of cones. The experiments prove that the mode of the ice failure before the boundary of upward-downward bending cone (UDBC) is crushing. A conclusion can also be drawn from the experiments that the ice force on the boundary of UDBC is by far less than that on a vertical pile with the same diameter. Moreover, the ice force frequencies on upright and inve-rted cones are obtained under the field condition of the platform JZ20-2, respectively. The results show that the alterna-tion of the ice force on UDBC can hardly induce resonance of platform JZ20-2.

Intra-trench variations in flexural bending of the subducting Pacific Plate along the Tonga-Kermadec Trench

We conducted a detailed analysis of along-trench variations in the flexural bending of the subducting Pacific Plate at the Tonga-Kermadec Trench.Inversions were conducted to obtain best-fitting solutions of trench-axis loadings and variations in the effective elastic plate thickness for the analyzed flexural bending profiles.Results of the analyses revealed significant along-trench variations in plate flexural bending:the trench relief(W0)of 1.9 to 5.1 km;trench-axis vertical loading(V0)of-0.5×10^12 to 2.2×10^12 N/m;axial bending moment(M0)of 0.1×10^17 to 2.2×10^17 N;effective elastic plate thickness seaward of the outer-rise region(Te^M)of 20 to 65 km,trench-ward of the outer-rise(Te^M)of 11 to 33 km,and the transition distance(Xr)of 20 to 95 km.The Horizon Deep,the second greatest trench depth in the world,has the greatest trench relief(W0 of 5.1km)and trench-axis loading(V0 of 2.2×10^12N/m);these values are only slightly smaller than that of the Challenger Deep(W0 of 5.7km and V0 of 2.9×10^12N/m)and similar to that of the Sirena Deep(W0 of 5.2 km and V0 of 2.0×10^12 N/m)of the Mariana Trench,suggesting that these deeps are linked to great flexural bending of the subducting plates.Analyses using three independent methods,i.e.,the/inversion,the flexural curvature/yield strength envelope analysis,and the elasto-plastic bending model with normal faults,all yielded similar average Te reduction of 28%-36% and average Te reduction area S△Te of 1195-1402 km^2 near the trench axis.The calculated brittle yield zone depth from the flexural curvature/yield strength envelope analysis is also consistent with the distribution of the observed normal faulting earthquakes.Comparisons of the Manila,Philippine,Tonga-Kermadec,Japan,and Mariana Trenches revealed that the average values Te^M of Te^M and both in general increase with the subducting plate age.

Clamping force of a multilayered cylindrical clamper with internalfriction

Holding an object by clamping force is a fundamental phenomena.Layered or laminated architectures with internal sliding features are essential mechanism in natural and man-made structural system.In this paper,we combine the layered architecture and clamping mechanism to form a multilayered clamper and study the clamping force with internal friction.Our investigations show that the clamping force and energy dissipation are very much depend on the number of layers,its geometry and elasticity,as well as internal friction.The central goal of studying the multilayered clamp is not only to predict the clamping force,but also as a representative case to help finding some clue on the universal behaviours of multilayered architectures with internal friction.

Elastic Bending Deformation of the Drill Strings in Channels of Curve Wells

The problem about identification of elastic bending deformation of a drill string in a curve wells based on the theory of flexible curved rods and the direct inverse problems of drill string bending in the channels of curvilinear bore-holes is stated. The problem is solved which determines the resistance forces and moments during performing ascending-descending operations in curvilinear bore-holes with trajectories of the second order curve shapes. The sensitivity of the resistance forces relative to geometric parameters of the bore-hole axial line trajectories is analyzed.

Sheet Bending Deformation in Production of Thin-Walled Pipes

Nowadays, thin-walled super-diameter pipes are produced by the method of plastic bending of sheets. After a sheet is bent into a pipe and its ends are welded, a pipe billet is subjected to expansion deformation. The technology of forming end areas of a sheet is developed and formulaes forming forces equations are deduced. Experimental investigations of deformation are undertaken.

THE METHOD OF THE RECIPROCAL THEOREM OF FORCED VIBRATION FOR THE ELASTIC THIN RECTANGULAR PLATES(Ⅲ)--CANTILEVER RECTANGULAR PLATES

In this paper,applying the method of the reciprocal theorem,we give the stationary solutions of the forced vibration of cantilever rectangular plates under uniformly distributed harmonic load and concentrated harmonic load acting at any point of the plates,the figures and tables of number value of bending moment and the deflection amplitudes as well.

THE METHOD OF THE RECIPROCAL THEOREM OF FORCED VIBRATION FOR THE ELASTIC THIN RECTANGULAR PLATES(Ⅱ)——RECTANGULAR PLATES WITH TWO ADJACENT CLAMPED EDGES

In this paper, applying the method of reciprocal theorem, we give the distributions of the amplitude of bending moments along clamped edges and the amplitude of deflections along free edges of rectangular plates with two adjacent clamped edges under harmonic distributed and concentrated loads.

A SOLVING METHOD FOR A SYSTEM OF PARTIAL DIFFERENTIAL EQUATIONS WITH AN APPLICATION TO THE BENDING PROBLEM OF A THICK PLATE

A theorem of solving a system of linear non-homogeneous differential equations through integrating and adding its basic solutions is put forward and proved, the mathematical role and physical nature of the theorem is interpreted briefly. As an example, the theorem is applied to solve the problem of thermo-force bending of a thick plate.

Impact of bending dies with different friction forms on forming force and quality of tubes manufactured by free bending technology

In the 3 D free bending forming system,the bending die can be designed either in a sliding type or rolling friction type.Bending die-based sliding friction type is often called normal bending dies;however,the bending dies-based rolling friction type includes bending die-based roller type and ball type in structure.In the current study,the impact of three bending dies on the forming force,and the bent tube quality was investigated.The obtained results showed that the tangential stresses and strains of the tubes formed by the bending die-based roller type were the smallest among the three bending dies.Besides,the spherical bearing force PUwas reduced drastically after using the roller type and ball type compared to the sliding friction type.Moreover,the uniformity of the wall thickness distribution of the tubes formed by the roller type and ball type was better than those obtained from the sliding friction type.In addition,the cross-section distortion rate was reduced by 2.8%using the roller type,and 1.8%using ball-type compared to the sliding friction type.

硬度耦合刚度增强型软体夹持器设计研究

软体夹持器具有良好的顺应性、无损伤和安全的人机交互性能等优点,但由于其材料的特性限制,往往存在刚度不足和夹持力小等问题。文中基于传统的快速气动网络结构,提出了一种硬度耦合结构的刚度增强型软体夹持器的结构方案。首先,结合硅橡胶材料的Yeoh本构模型和静力平衡及虚功原理,建立了刚度增强型软体夹持器的运动学和力学模型,描述了夹持器手指弯曲角度和末端接触力与压强之间的关系;其次,运用ABAQUS软件对不同硬度结构的夹持器进行了有限元分析,制作了夹持器实体,搭建实验台测定了夹持器手指实际变形和末端接触力数据,并通过实际抓取对比试验验证了实际抓取效果。结果表明:相较于传统结构,硬度耦合结构在同为20 kPa的驱动气压下,弯曲角度最大可减小120°;极限压力下,末端接触力最大增加0.1 N;最优设计为05HA结构,抓取物的质量是传统型的3.42倍。

黄百铁路红水河特大桥无缝线路设计方案研究

基于我国典型铁路大跨度上承式拱桥桥上无缝线路设计及运营概况,针对新建黄百铁路红水河特大桥,以梁轨相互作用原理为依据,建立上承式拱桥梁轨协同作用三维分析模型,研究提出桥上无缝线路设计方案。研究结果表明:红水河特大桥采用常阻力扣件、不设置钢轨伸缩调节器的方案不满足钢轨强度要求;在拱圈内设置钢轨伸缩调节器,对于附加挠曲力和制动力改善效果不大,不满足钢轨强度要求;在拱圈外设置钢轨伸缩调节器,附加挠曲力和制动力均得到显著降低,桥上无缝线路钢轨强度、稳定性、断缝值均满足设计要求。

考虑弯曲空间效应影响的箱梁强迫振动分析

选取附加挠度为剪力滞广义位移,箱梁体系总动能中计入剪力滞附加变形的影响,综合运用薄壁结构弹性理论和Hamilton原理,建立考虑弯曲空间效应影响的箱梁强迫振动控制微分方程及边界条件,并给出任意简谐荷载作用下简支和连续箱梁的强迫振动解析解。引入振动频率影响的应力和挠度放大系数,详细分析简支、连续箱梁剪切剪力滞效应在初等梁结果中的占比及放大系数分布规律。算例分析表明:考虑弯曲空间效应影响的箱梁截面纵向动应力与有限元结果吻合良好;振动频率越大,应力和挠度放大系数、剪切效应占比越大,剪力滞效应占比越小;同频率振动时,简支箱梁放大系数远大于两跨连续箱梁(单跨长等于简支跨长),且频率越高,差值比越大;基频内振动时,箱梁纵向应力计算可忽略剪力滞效应,挠度计算需考虑剪切变形的影响。

基于同频弯扭耦合强迫振动的桥梁断面颤振导数识别方法改进

为拓展强迫振动法在桥梁断面颤振导数识别领域中的应用能力,采取让断面做2次同频异相的弯扭耦合简谐运动模式,理论推导出任意非零相位差条件下的桥梁断面颤振导数识别公式。以理想平板的Theodorsen解为气动力数据源,对该方法的识别能力进行数值验证,并在此基础上研究弯扭耦合运动相位差、高斯白噪声、整数倍频有色噪声对平板颤振导数识别结果的影响规律。基于Fluent软件,将该方法与计算流体动力学(Computational Fluid Dynamics,CFD)技术结合,识别得到丹麦大带东桥主梁断面的颤振导数。研究结果表明:当平板气动力不包含噪声时,在任意非零相位差取值条件下,按照该方法识别所得颤振导数结果与理论值完全吻合;当平板气动力含有高斯白噪声时,在考察的3个低水平噪声条件下(5%、10%、15%),颤振导数识别误差与高斯白噪声比例水平、折算风速均成正相关,但不同颤振导数对高斯白噪声敏感程度各异;当平板气动力包含整数倍频有色噪声时,3倍频、4倍频噪声对颤振导数的识别精度影响显著,其他低倍频噪声和超高倍频噪声的影响较小,在8个颤振导数的识别结果中,H_(2)^(*)、H_(4)^(*)、A_(2)^(*)、A_(4)^(*)对倍频有色噪声更敏感。应用该方法结合CFD数值模拟识别得到的大带东桥主梁颤振导数与既有文献结果吻合良好,经计算得到的颤振临界风速也较为接近。研究结果可满足同类桥梁颤振设计的工程计算需求。

表面效应对纳米开关结构线性弯曲行为的影响

纳米开关结构是纳米机电系统中的重要控制元件,基于表面能的模型引入表面效应,分析了表面效应和分子间作用力同时对纳米开关结构线性弯曲行为的影响。对应变能与表面能进行变分,并通过最小势能原理,推导出纳米开关的控制方程以及边界条件,并运用同伦摄动法来求解该非线性微分方程。通过计算结果具体分析了不同边界条件下纳米开关在考虑表面效应和Casimir力作用下表面效应对纳米开关弯曲变形、吸合电压的影响。研究结果表明,表面效应会使得纳米开关结构的弯曲变形更小,从而使得吸合电压变大,表面效应对纳米开关的吸合稳定性具有显著的影响。这对认识和研究纳米开关的力学行为,以及纳米开关的设计与制备有着重要的理论意义与实际使用价值。