An investigation on multilayer shape memory polymers under finite bending through nonlinear thermo-visco-hyperelasticity

This study presents a semi-analytical solution to describe the behavior of shape memory polymers(SMPs) based on the nonlinear thermo-visco-hyperelasticity which originates from the concepts of internal state variables and rational thermodynamics.This method is developed for the finite bending of multilayers in a dual-shape memory effect(SME) cycle.The layer number and layering order are investigated for two different SMPs and a hyperelastic material.In addition to the semi-analytical solution,the finite element simulation is performed to verify the predicted results,where the outcomes demonstrate the excellent accuracy of the proposed solution for predicting the behavior of the multilayer SMPs.Since this method has a much lower computational cost than the finite element method(FEM),it can be used as an effective tool to analyze the SMP behavior under different conditions,including different materials,different geometries,different layer numbers,and different layer arrangements.

Multiresolution method for bending of plates with complex shapes

A high-accuracy multiresolution method is proposed to solve mechanics problems subject to complex shapes or irregular domains.To realize this method,we design a new wavelet basis function,by which we construct a fifth-order numerical scheme for the approximation of multi-dimensional functions and their multiple integrals defined in complex domains.In the solution of differential equations,various derivatives of the unknown function are denoted as new functions.Then,the integral relations between these functions are applied in terms of wavelet approximation of multiple integrals.Therefore,the original equation with derivatives of various orders can be converted to a system of algebraic equations with discrete nodal values of the highest-order derivative.During the application of the proposed method,boundary conditions can be automatically included in the integration operations,and relevant matrices can be assured to exhibit perfect sparse patterns.As examples,we consider several second-order mathematics problems defined on regular and irregular domains and the fourth-order bending problems of plates with various shapes.By comparing the solutions obtained by the proposed method with the exact solutions,the new multiresolution method is found to have a convergence rate of fifth order.The solution accuracy of this method with only a few hundreds of nodes can be much higher than that of the finite element method(FEM)with tens of thousands of elements.In addition,because the accuracy order for direct approximation of a function using the proposed basis function is also fifth order,we may conclude that the accuracy of the proposed method is almost independent of the equation order and domain complexity.

Deformation Analysis on Shear-Bending of Ring-Shaped Piezoelectric Actuator

Deformation of a simple single piezoelectric actuator is usually quite small.A ring-shaped piezoelectric actuator with large piezoelectrically generated displacement was proposed.The thickness of the actuator was1 mm,and the inner and outer diameters were 4 mm and 40 mm,respectively.The ring-shaped actuator was made of BiScO_3-PbTiO_3(BS-PT)ceramic and polarized in radial direction.An electric field was applied to thickness direction and a large shear-bending deformation emerged.Then Rayleigh-Ritz method and Bessel functions were adopted to analyze the shear-bending deformation.Results show that under an electric field of 7.5kV/cm,the maximum displacement at the inner edge of the actuator reached 5.07μm,which agreed well with the corresponding experimental results.

Shape design of the reinforcement for bending load-carrying capacity of under-matched butt joint under four-point bending load

To improve the bending load-carrying capacity （ BLCC） of under-matched butt joint under four-point bending load in the elastic stage, the shape design of the reinforcement is studied based on the theoretics of mechanics of materials. The concept, criterion, realization condition and design proposal of equal bending load-carrying capacity （EBLCC） are put forward. The theoretical analysis results have been verified by the finite element method. The simulation results are coincident basically with the ones of theoretical analysis. The research results show that the shape design of the reinforcement of EBLCC can improve BLCC of under-matched butt joint and the unilateral-side type reinforcement can replace double-side symmetry

Fuzzy Control System of Hydraulic Roll Bending Based on Genetic Neural Network

For nonlinear hydraulic roll bending control, a new fuzzy intelligent control method was proposed based on the genetic neural network. The method taking account of dynamic and static characteristics of control system has settled the problems of recognizing and controlling the unknown, uncertain and nonlinear system successfully, and has been applied to hydraulic roll bending control. The simulation results indicate that the system has good performance and strong robustness, and is better than traditional PID and neural-fuzzy control. The method is an effective tool to control roll bending force with increased dynamic response speed of control system and enhanced tracking accuracy.

Post-Buckling Behavior of Laminated Composite Cylindrical Shells Subjected to Axial, Bending and Torsion Loads

In present work, post-buckling behavior of imperfect (of eigen form) laminated composite cylindrical shells with different L/D and R/t ratios subjected to axial, bending and torsion loads has been investigated by using an equilibrium path approach in the finite element analysis. The Newton-Raphson approach as well as the arc-length approach is used to ensure the correctness of the equilibrium paths up to the limit point load. Post-buckling behavior of imperfect cylindrical shells with different L/D and R/t ratios of interest is obtained and the theoretical knock-down factors are reported for the considered cylindrical shells.

Application of Approximation Full-Load Distribution Method to Pass Scheduling on Plate Mill With Hydro-Bending System

The influence of positive bending system on plate crown control was researched. The approximation fullload distribution method for pass scheduling was put forward. This method can not only make full use of the mill capacity with decreased pass number, but also give quality product of excellent flatness.

Research on vibration characteristics of L-shaped plate using a mobility power flow approach

L-shaped plates have become an important focuses in structural vibration research. To determine their vibration characteristics, this paper applied a mobility power flow method. Firstly, the L-shaped plate was divided into two substructures to simplify analysis. The coupled bending moment was then deduced by applying a continuous vibration property on the common edge. Next, the response on any point of the plate and the input and transmitted power flow formulas were calculated. Numerical simulations showed the distribution of the coupled bending moment and the response of the whole structure. The validity of this method was verified by the SEA approach.

Analysis and Simulation of S-shaped Waveguide in Silicon-on-insulator

The simulation and analysis of S-shaped waveguide bend are presented.Bend radius larger than 30 mm assures less than 0.5 dB radiation loss for a 4-μm-wide silicon-on-insulator waveguide bend with 2-μm etch depth.Intersection angle greater than 20° provides negligible crosstalk (<-30 dB) and very low insertion loss.Any reduction in bend radius and intersection angle is at the cost of the degradation of characteristics of bent waveguide and intersecting waveguide, respectively.

Mechanical Property Evaluation on the Bending and Compressing Behaviour of Nano-beam

Based on quasicontinuum（QC） multiscale simulation method,a series of simulation models were set up for bending and compressing rod-shaped microstructure of single crystal Cu.The effects of structural parameters on typical mechanical properties were analyzed,such as elastic modulus,elastic limit,yield strength,and Poisson’s ratio.According to the analysis of displacement,inner stress and strain energy,the mechanisms of deformation and failure were also revealed.The experimental result shows that the mechanical properties exhibit obvious size effect during the bending and compression process.In the bending simulation,when the span-thickness ratio is more than 10,the elastic modulus rises slightly with the increase of strain.And the smaller the beam is,the faster the elastic modulus grows.Meanwhile,when the spanthickness ratio keeps constant the elastic modulus will decrease with the growth of the beam sizes.However,in the compression model,the size effect on Poisson’s ratio is not remarkable.The dimensional change in one direction cannot influence the mechanical parameters greatly.Mechanical twins and dislocation contribute to the compression behaviour greatly.Meanwhile,the stress concentration can also be found in the inner partial area and the strain energy decreases abruptly after the crush of beam microstructure.

Shape Memory Polymer Composite Booms with Applications in Reel-Type Solar Arrays

Solar arrays are the primary energy source for spacecraft.Although traditional rigid solar arrays improve power supply,the quality increases proportionally.Hence,it is difficult to satisfy the requirements of high-power and low-cost space applications.In this study,a shape-memory polymer composite(SMPC)boom was designed,fabricated,and characterized for flexible reel-type solar arrays.The SMPC boom was fabricated from a smart material,a shape-memory polymer composite,whose mechanical properties were tested.Additionally,a mathematical model of the bending stiffness of the SMPC boom was developed,and the bending and buckling behaviors of the boom were further analyzed using the ABAQUS software.An SMPC boom was fabricated to demonstrate its shape memory characteristics,and the driving force of the booms with varying geometric parameters was investigated.We also designed and manufactured a reel-type solar array based on an SMPC boom and verified its self-deployment capability.The results indicated that the SMPC boom can be used as a deployable unit to roll out flexible solar arrays.

工字形钢梁-矩形钢管柱单向螺栓节点抗弯承载力理论计算方法

针对工字形纯钢梁和钢-混凝土组合梁分别与矩形钢管柱和矩形钢管混凝土柱采用单向螺栓(也称单边拧紧螺栓)连接形成的4种节点形式,对其在弯矩作用下的受力机理及破坏模式进行分析,讨论导致节点失效的因素。总结节点在弯矩作用下的9种失效模式,包括:单向螺栓拉断、端板受弯屈服、矩形钢管柱壁翼板受拉屈服、矩形钢管柱壁翼板受压屈服、矩形钢管柱壁腹板受压屈曲、混凝土楼板局部压溃、钢筋屈服、矩形钢管柱内混凝土局部压溃、矩形钢管柱壁腹板受压屈服,进而基于破坏模式给出节点各组件承载力的计算公式。对4种节点在不同破坏模式下的正弯矩承载力和负弯矩承载力进行分析,给出节点承载力计算公式。将节点抗弯承载力的理论计算结果与试验结果进行对比,验证理论计算方法的可靠性。

黄河“几”字弯都市圈资源环境承载力与经济发展耦合协调研究

在生态文明建设理念下,如何实现生态脆弱区资源环境与经济的协调发展,已成为我国亟待解决的问题之一。以典型生态脆弱区黄河“几”字弯都市圈21个地级市为例,基于2005年、2010年、2015年、2020年的资源环境与经济发展数据,运用熵权TOPSIS法分析资源环境承载力状况,并引入耦合协调度模型揭示资源环境承载力与经济发展水平耦合协调关系及其时空演变特征,结果表明:黄河“几”字弯都市圈资源环境承载力呈波动上升趋势,区域差异显著;资源环境承载力与经济发展水平的耦合协调度整体逐渐趋向于更高程度的耦合;通过莫兰指数分析发现,黄河“几”字弯都市圈资源环境承载力与经济发展水平耦合协调度为显著空间正相关。

冷连轧弯辊力精度改进PSO-SVM预测及补偿分析

为了进一步控制冷连轧弯辊力精度,构建改进PSO-SVM预测模型。利用包含压缩因子的粒子群算法完成支持向量机参数的更高效寻优处理,对回归轧制参数实施反归一化获得弯辊力模型。根据现场实际轧制结果完成预测模型的验证过程。研究结果表明:采用改进PSO-SVM模型获得的预测性能指标在上述优化方法中达到了最低,改进PSO-SVM模型具备最优预测效果。设置可靠补偿后大幅降低了AFC系统工作量,促进了带钢板形效率的显著提升。弯辊力补偿值形成了与弯辊力几乎相同的变化规律,具备优异预测性能。

腹板嵌入式双倒T型钢-混组合梁受弯性能研究

在通过横隔板连接的双倒T型钢腹板上部开槽,并将开槽腹板部分嵌入到混凝土翼板,与底部钢筋共同形成带有榫结构连接的腹板嵌入式双倒T型钢-混组合梁。设计了该试件的受弯性能试验,分析总结了试件的破坏模式,并基于荷载-挠度曲线和应变分布特征等试验结果对其承载力和延性等力学指标进行评估。该梁满足完全抗剪连接,具有良好的整体抗弯性能。根据试验及有限元模拟结果,提出了抗弯承载力设计方法,试验结果与理论计算结果误差为2.7%,结果吻合较好,该理论公式可作为结构设计的依据。

光伏支架高强冷弯C型钢檩条的受弯性能研究

为研究光伏支架中高强冷弯C型钢檩条的受弯性能,对5种布置方式下的LQ550高强冷弯C型钢檩条(下文简称为“C型钢檩条”)开展了跨间6个加载点集中加载试验。建立C型钢檩条有限元模型,并通过试验得到的C型钢檩条受弯性能验证模型的准确性,并依此模型探究檩条相对长细比对其受弯稳定承载力的影响规律。参照GB 50018—2002《冷弯薄壁型钢结构技术规范》的规定,分析了撑杆约束对檩条受弯稳定承载力的有利作用。结合实际项目,对采用C型钢撑杆的光伏支架开展现场加载试验。研究结果表明:1)檩条的抗弯刚度和受弯稳定承载力通过在跨间设置撑杆约束后明显提高,且设置C型钢撑杆约束的提高效果强于圆管撑杆。2)C型钢撑杆可视为理想侧向支承,檩条平面外计算长度系数可以根据C型钢撑杆的设置情况取值。3)现场加载试验证明C型钢撑杆对檩条扭转具有良好的约束效果,充分验证了采用C型钢撑杆体系的新型光伏支架结构的适用性。

气动扇形腔室软体弯曲驱动器的设计及分析

为了设计结构简单、制作方便、易于建模的大角度弯曲驱动器,提出了一种扇形腔室结构的软体多腔室弯曲驱动器。该驱动器由超弹性材料制作而成,并在Yeoh本构模型的基础上,建立了输入空气压力与弯曲角的函数关系。利用Abaqus有限元分析软件对驱动器在不同驱动气压下的弯曲变形进行了仿真,分析了腔室端面半径、腔室壁厚、腔室端面夹角、凹槽深度、底层厚度等结构参数对驱动器弯曲角度的影响。制作了软体驱动器,搭建了气动控制实验平台,测试了驱动器的弯曲性能,输入气压为0~65 kPa,弯曲角度为0~218°,仿真结果与实验结果基本吻合。基于弯曲驱动器设计了一种夹爪长度可调的软体夹持器,测试了其对不同尺寸、形状、质量的物体的夹持效果,实验结果验证了所设计驱动器和夹持器的实用性,表明驱动器具有良好的弯曲性能。研究结果可以为软体驱动器的进一步研究提供参考。

H形钢梁弯曲滞回性能研究与数值模拟优化

为完善H形钢梁在纯弯曲荷载作用下的滞回性能的研究,对2类截面的H形钢梁增加一个多周滞回加载制度下的拟静力试验。此加载制度下的目标耗能量与此试件等幅升幅加载制度下达到峰值荷载时的总耗能量相等,因此对该试件的破坏模式、累积损伤和耗能规律进行分析,验证了原设想中存在的不影响滞回耗能的阈值低于0.02 rad。同时进行了有限元对比分析,对此试验已有模型进行了精细化处理。有限元分析中利用热塑性方法模拟了试件焊接残余应力的变化过程,从而在模型加载过程中引入残余应力的影响,使试件的初始刚度、翼缘局部屈曲发生的时刻、极限荷载后刚度退化有显著改善。

宽翼工字形涤纶的生产工艺

介绍了一种宽翼工字形涤纶全拉伸丝(FDY)的生产工艺,对喷丝板、纺丝工艺、热辊拉伸工艺等进行了调试,探索得到最佳工艺条件。试验表明:在纺丝温度为290~295℃,冷却风速为2.5 m/s,冷却风温为20℃,GR1速度为1 800 m/min、温度为91℃,GR2速度为4 370 m/min、温度为135℃,卷绕速度为4 300 m/min的工艺条件下,生产的工字形涤纶FDY的断裂强度为3.59 cN/dtex,10%模量为3.20 cN/dtex,条干不匀率在1.2%以下。该纤维抗弯性佳,且质轻、手感滑糯,具有特殊的光泽,可应用于割绒、貂绒、獭兔毛等起绒面料,具有很好的经济价值和推广价值。

关于弯剪型特性的底部隔震剪力墙结构计算方法研究

底部隔震剪力墙结构在强震作用下具有弯剪型侧移曲线的特性,采用铁木辛柯梁模拟底部隔震的剪力墙结构在隔震后的动力特征和隔震效应。推导了底部隔震悬臂梁模型在地震中的动力特征,提出了延长周期、减少高阶振型参与质量系数和增加体系阻尼比是隔震技术减震的三大因素,指出了增加结构阻尼可有效地提高长周期高层结构的隔震效果,同时隔震可降低复杂高层结构高阶振型的影响。