编织型食管支架结构及其丝线的力学性能分析(英文)

旨在找出支架结构参数与支架径向刚度之间的关系并了解支架变形及丝线上的应力分布规律.按照空间螺旋曲线方程创建几何模型,用梁-梁接触单元和三维梁单元建立有限元模型,并定义丝线为线弹性材料.有限元分析结果显示支架结构径向刚度及丝线上的应力分布与支架的各个结构参数都相关,其中丝线螺距对其影响最大.在相同载荷作用下,当丝线头数是24且支架的其他结构参数都不变时,丝线横截面上的应力最小.最后,将体外实验结果与分析结果进行比较,数据规律具有一致性,可以证明该有限元模型能够用于近似预测编织型食管支架的相关力学性能.     

混凝土重力坝二维与三维有限元仿真分析

运用有限元软件来模拟混凝土重力坝的二维、三维模型,通过对计算结果的分析,可以得到坝体的位移、应力-应变、裂缝等工程特性指标,可以为重力坝的设计、复核验算提供依据。     

一种用于模拟薄壁钢构件冲击响应的非线性显式动力GBT模型（英文）

建立了一种基于广义梁理论(GBT)的非线性显式动力梁有限元模型,该模型可用于等截面薄壁钢构件的冲击响应模拟.考虑冲击加载时的应变率强化及绝热升温引起的热软化效应,当前模型采用了一种修正的Cowper-Symonds率相关本构模型.用GBT截面变形模态构建单元截面位移场,因此新模型可考虑构件截面的畸变、屈曲及任意的翘曲剪切等局部效应.此外,用三次非均匀B样条基函数拟合各个GBT截面变形模态的幅值函数.用Kirchhoff薄板假设构造弯曲相关位移场.用Green-Lagrange应变张量和PK2应力分别描述材料点的应变和应力,假设各材料点处于平面应力状态.为了验证所提模型的有效性,给出了3组薄壁构件的冲击分析算例,将当前模型的结果和壳有限元(Ls-Dyna)分析结果进行了对比,结果表明:当前模型和壳有限元模型的位移解和应力解具有等效精度,但所提模型的计算效率更高,并具备更好的结构明晰性.     

可回收外周血管支架设计与生物力学研究

为解决传统支架长期滞留体内诱发支架内再狭窄的问题,设计一种新型可回收外周血管支架,并对其安全性与有效性进行力学分析。首先建立支架和外周斑块血管有限元模型,对支架进行压握、自由扩张过程的有限元分析,比对分析结果与径向支撑力测试结果,发现误差小于10%,验证了支架有限元模型有效性;在此基础上,再对支架植入及回收过程进行仿真模拟,分析与血管耦合条件下支架与血管生物力学性能。压握过程中支架最大应变为5.919%,回收过程中支架所受等效应力最大值为691MPa,均小于支架材料镍钛合金最大弹性应变及屈服应力。自膨胀扩张过程中血管所受最大等效应力值为0.592 6MPa,支架回收过程中血管所受等效应力最大值为0.536 6MPa,均小于血管损伤应力。试验结果表明,新型可回收外周血管支架理论上是可回收的,并且在植入以及回收过程中,其力学性能安全可靠。     

基于Solidworks工程图表达方法的教学实践

Solidworks设计的三维机件模型和二维工程图双向并联,即零件设计后可直接由三维模型生成二维工程图,是工程类技术人员必须掌握的工程技术软件。为此分析了Solidworks工程图与国标不符的差异及其解决方法。     

水流冲刷条件下群桩基础力学性质数值模拟

分析了群桩基础桩-土相互作用的主要特征,对三维问题进行分析并简化,建立桩-土非线性作用问题的有限元求解模型,并对不同工况进行数值计算。根据数值模拟计算所得位移、应变和应力结果,分析不同荷载组合下基桩受力特点和承台受力变形特征,为群桩基础设计考虑土与基础结构协调作用提供依据。     

带孔薄壁圆管多轴加载下的弹塑性有限元分析

对低碳钢材料带孔薄壁圆管试样采用逐级加载试验方法,得出其在室温下的单轴循环应力-应变本构关系。利用有限单元法对圆管试样进行弹塑性分析,采用Von Mises屈服准则、多线性随动强化模型,并结合试验获得的本构关系来定义材料的弹塑性特性。拉扭应变载荷加载在柱坐标下进行,采用一端固定,另一端加轴向位移与周向位移的方式。分别在纯拉、纯扭以及拉-扭比例加载下计算出应力应变场,获得不同受力情况下不同孔径尺寸试样在缺口处的应力应变分布。计算结果为多轴加载疲劳试验和复杂应力状态下工程零部件的疲劳寿命预测与分析提供基本数据。     

一种新的基于应力的有限元分析公式（英文）

目的:本文旨在提出一种新的基于应力的结构分析公式,以期可以相对轻松地解决材料非线性分析问题并对材料的线性行为及非线性行为直接给出结果。另外,期望该方法可以扩展到三维有限元分析中。创新点:1.目前关于材料非线性分析的技术非常冗长、乏味和耗时,而本文提出的公式由于可以看作是积分公式而不是微分公式,所以非常适合解决断裂力学问题;2.本文提出的公式对问题的求解是通过机器学习的回归模型完成。方法:1.应用本文所提出的新方法并在分析过程中消除经典方法的繁琐、冗长、逐步增量以及迭代的过程。2.在分析过程中不需要使用弹性模量,直接使用由材料的应力-应变曲线导出的应力-应变函数作为材料输入。结论:本文提出的方法在物理步骤上非常简单、准确和清晰,适合材料非线性和断裂力学问题的求解。     

荷载倾角对光伏支架微型桩承载特性影响的试验与数值模拟研究

依据卵石土地区华能海南州光伏项目现场试桩竖向抗拔和水平静载试验数据,采用三维连续介质拉格朗日法有限差分软件(FLAC^3D)建立计算模型,通过模型分析光伏微型短桩及支架体系在不同荷载倾角下的承载特性。结果表明：光伏微型单桩竖向位移的增长率随着荷载倾角的增大逐渐变缓,水平位移增长率逐渐变快;荷载倾角位于15°～75°范围内,光伏支架体系竖向位移在加载前期增长趋势相同;光伏支架体系的倾斜荷载-桩顶水平位移曲线均呈缓变型,极限水平荷载随荷载倾角的增大而减小;由于光伏支架体系的整体性,荷载倾角位于15°～30°范围内时合位移由竖向位移和水平位移共同决定,建议在工程设计时采用倾角在此范围内的光伏支架,以保证其良好的抗拔性能。     

3D打印并联机器人实验平台的设计

以基于4-RPR冗余并联机构的3D打印机器人为研究对象,首先,确定了3D打印机器人并联机构的具体尺寸,对机架进行结构设计,利用Solidworks建立机器人平台的三维模型。其次,将模型导入Adams进行运动学和动力学仿真分析,得出该机构的位移、速度和加速度变化曲线,根据仿真结果,得出关键点受力数据,对电动推杆进行选型。最后,利用Ansys Workbench对机器人实验平台的主要连接件进行有限元仿真,对其进行应力应变分析,保证机器人工作的安全性及稳定性。     

鱼塘水电站溢洪道闸室三维有限元分析

通过建立三维模型，应用ANSYS分析软件，对鱼塘水电站溢洪道闸室进行三维有限元计算，重点分析了预应力锚固端和牛腿部位的应力和应变，为鱼塘水电站溢洪道闸室的设计提供了依据，也为今后的实际工程提供了有意义的参考。     

Carrier distribution and electromechanical fields in a free piezoelectric semiconductor rod

We made a theoretical study of the carrier distribution and electromechanical fields in a free piezoelectric semiconductor rod of crystals of class 6 mm. Simple analytical expressions for the carrier distribution, electric potential, electric field, electric displacement, mechanical displacement, stress, and strain were obtained from a 1D nonlinear model reduced from the 3D equations for piezoelectric semiconductors. The distribution and fields were found to be either symmetric or antisymmetric about the center of the rod. They are qualitatively the same for electrons and holes. Numerical calculations show that the carrier distribution and the fields are relatively strong near the ends of the rod than in its central part. They are sensitive to the value of the carrier density near the ends of the rod.     

Computation of rolling resistance caused by rubber hysteresis of truck radial tire

Applying the results of stress and strain calculated by 3D finite element model of truck radial tire 11.00R20, a MATLAB program used to compute rolling resistance of the tire caused by hysteresis rolling resistance (HRR) is worked out. The HRR distribution on different part of tire section, and the effects of speed, load, internal pressure and the width of the rim on HRR are analyzed. The analysis results showed that energy loss produced by tread rubber contributes the most part to HRR of the whole tire, and that to decrease the HRR, the hysteresis factor of the tread rubber should be reduced, and the distribution of the stress and strain on the section be optimized.     

Stress and Displacement Distribution of Soft Clay Slope with 2D and 3D Elastoplastic Finite Element Method

Based on elastoplastic model, 2D and 3D finite element method (FEM) are used to calculate the stress and displacement distribution in the soft clay slope under gravity and uniform load at the slope top. Stability analyses indicate that 3D boundary effect varies with the stress level of the slope. When the slope is stable, end effect of 3D space is not remarkable. When the stability decreases, end effect occurs; when the slope is at limit state, end effect reaches maximum. The energy causing slope failure spreads preferentially along y-z section, and when the failure resistance capability reaches the limit state, the energy can extend along x-axis direction. The 3D effect of the slope under uniform load on the top is related to the ratio of load influence width to slope height, and the effect is remarkable with the decrease of the ratio.     

Equivalent Theorem of Hellinger-Reissner and Hu-Washizu Variational Principles

lintroductionIn1954,byso-calledtry-and-el.l.ormethodHull]deducedtheHu-Washizupl'inciple,whichplaysan.importantroleinthehistoryofvariation.In1964,ChienlZIsystematicallydiscussedtheLagrangemultipliermethod.Withthemethod,hesuccessfullydeducedHu-Washizuprinci…     

Equivalent theorem of Hellinger-Reissner and Hu-Washizu variational principles

The paper has proved that Hellinger-Reissner and Hu-Washizu variational principles are but equivalent principles in elasticity by following three ways: 1) Lagrange multiplier method. The paper points out that only a new independent variable can be introduced when one constraint equation has been eliminated by one Lagrange multiplier, which must be expressed as a function of the original variable(s) and/or the new introduced variable after identification. In using Lagrange multiplier method to deduce Hu-Washizu principle from the minimum potential energy principle, which has only one kind of independent variable namely displacement, by eliminating the constraint equations of stress-displacement relations, one can only obtain a principle with two kinds of variables namely displacement and stress; 2) involutory transformation, with such method Hu-Washizu variational principle can be deduce directly from the Hellinger-Reissner variational principle under the same variational constraints of stress-strain relation, and vice verse; 3)semi-inverse method, by which both of the above variational principles can be deduced from the minimum potential energy principle with the same variational constraints. So the three kinds of variational functions in Hu-Washizu variational principle are not independent to each other, the stress-strain relationships are still its constraint conditions.     

基于神经网络结构分解与FLAC~(3D)的初始地应力场反演

介绍了采用FLAC30内嵌功能较强的FISH语言对初始地应力场生成方法的改进,建立了三维非线性地应力反演分析数值模型.模拟了断层及裂隙密集带,并采用此方法构造神经网络样本,采用神经网络结构分析的方式,对不同深度的侧向系数进行反演.通过正分析的计算结果与现场实测值对比,满足精度要求,表明所获得的岩体地应力场是基本合理的.     

基于ANSYS的应力强度因子计算

利用大型有限元分析软件ANSYS并基于"位移外推"法进行应力强度因子的计算,其实现方法有两种:一种是采用1/4节点单元模拟裂纹尖端奇异性,由ANSYS直接给出应力强度因子值;另一种是先计算出靠近裂纹尖端处节点的位移或应力,再线性拟合,这种方法不一定要考虑奇异性,只需使网格足够精细即可。文章通过实例介绍了这两种方法求解应力强度因子的过程和技巧,并将计算结果与理论分析结果进行了比较,表明两种方法均可行。     

3D finite element simulation of tunnel boring machine construction processes in deep water conveyance tunnel

Applying stiffness migration method, a 3D finite element mechanical model is established to simulate the excavation and advance processes. By using 3D nonlinear finite element method, the tunnel boring machine (TBM) excavation process is dynamically simulated to analyze the stress and strain field status of surrounding rock and segment. The maximum tensile stress of segment ring caused by tunnel construction mainly lies in arch bottom and presents zonal distribution. The stress increases slightly and limitedly in the course of excavation. The maxi-mum and minimum displacements of segment, manifesting as zonal distribution, distribute in arch bottom and vault respectively. The displacements slightly increase with the advance of TBM and gradually tend to stability.     

Digital Modeling and Visualization of Hydroelectric Engineering Geoinformation

To describe the spatial tendency and complex relationship of geological structures, a digital modeling based on geographic information system and the visualization of hydroelectric engineering geology information are presented. The functions of information visual query, spatial cutting, section drawing, and coupled analysis with hydraulic structures are realized. The geologic model can match the attribute data with the shape data of geological structures, and organize the information for spatial query and analysis of the 3D model. With an application in Laxiwa hydroelectric project on the upriver of Huanghe River, the method provides a 3D parallel section view and query results of geoinformation, and 3D section views of geoinformation along axis of spillway tunnel,and along the 5th axis with underground structures, respectively.