ansys屈曲计算命令
(ANSYS屈曲分析)
7.1 特征值屈曲分析的步骤 7.2 构件的特征值屈曲分析 7.3 结构的特征值屈曲分析
第7章 结构弹性稳定分析
结构失稳或结构屈曲: 当结构所受载荷达到某一值时，若增加一微小的 增量，则结构的平衡位形将发生很大的改变，这种现 象叫做结构失稳或结构屈曲。 结构稳定问题一般分为两类: ★第一类失稳：又称平衡分岔失稳、分枝点失稳、特 征值屈曲分析。结构失稳时相应的荷载可称为屈曲荷 载、临界荷载、压屈荷载或平衡分枝荷载。 ★第二类失稳：结构失稳时，平衡状态不发生质变， 也称极值点失稳。结构失稳时相应的荷载称为极限荷 载或压溃荷载。 ●跳跃失稳：当荷载达到某值时，结构平衡状态发生 一明显的跳跃，突然过渡到非邻近的另一具有较大位 移的平衡状态。可归入第二类失稳。
7.1 特征值屈曲分析的步骤--查看结果
⑴ 列表显示所有屈曲荷载系数 命令格式：SET,LIST SET栏对应的数据为模态数阶次，TIME/FREQ栏对应的数据 为该阶模态的特征值，即屈曲荷载系数。荷载步均为1，但每个 模态都为一个子步，以便结果处理。 ⑵ 定义查看模态阶次 命令格式：SET,1,SBSTEP ⑶ 显示该阶屈曲模态形状 命令格式：PLDISP ⑷ 显示该阶屈曲模态相对应力分布 命令格式：PLNSOL或PLESOL等。 模态形状归一化处理，位移不表示真实的变形。 直接获取第N阶屈曲模态的特征值（屈曲荷载系数）： *get,freqN,mode,N,freq 其中FREQN为用户定义的变量，存放第N阶模态的屈曲荷载系 数，其余为既定标识符。
第7章 结构弹性稳定分析
★结构弹性稳定分析=第一类稳定问题 ANSYS特征值屈曲分析（Buckling Analysis）。 ★第二类稳定问题 ANSYS结构静力非线性分析，无论前屈曲平衡状态 或后屈曲平衡状态均可一次求得，即“全过程分析”。 这里介绍ANSYS特征值屈曲分析的相关技术。在本 章中如无特殊说明，单独使用的 “ 屈曲分析 ” 均指 “ 特 征值屈曲分析”。
最新ansys屈曲分析练习模型
ansys屈曲分析练习模型：边界条件：底端固定几何：长为100mm，截面：10mm×10mm 惯性矩：Izz=833.333材料性质：E=2.0e5MPa,v=0.3分析压力的临界值分析过程：特征值屈曲分析方法：1、建立关键点1(0 0 0),2(0 100 0)2、在关键点1、2之间建立直线3、定义单元类型(Beam3)4、定义单元常数5、定义材料属性6、定义网格大小，指定单元边长为107、划分网格（首先此处应该做一次模态分析，有模态数据文件，后出来才可以看屈曲模态。
）8、定义分析类型（static）9、激活预应力效应。
要进行屈曲分析，必须激活预应力效应。
10、施加位移约束（关键点1固定）11、施加集中荷载，Fy=-1N12、求解13、结束求解，14、重新定义分析类型（Eigen Buckling)15、设置屈曲分析选项，提取1阶模态（菜单路径：Solution-->Analysis Type-->Analysis options16、求解，结束后退出17、解的展开1）设置expansion pass “on”2）设置展开模态为1（Load Step Options>ExpansionsPass>Single Expand>Expand Modes3)重新求解18、查看结果（临界载荷和屈曲模态等）二、非线性分析方法前8步与上述过程相同9、设置分析控制（主要黄色高亮部分区域需要修改）10、施加位移约束（关键点1固定）11、施加集中荷载，Fy=-50000N，Fx=-250N12、求解13、查看变形和位移14、定义时间-历史变量1）进入时间历程后处理器（TimeHist Postproc)2）在弹出的对话框中选择左上角的+号，添加一个监控变量（节点2的Y方向位移）15、查看位移-载荷曲线屈曲分析是一种用于确定结构开始变得不稳定时的临介荷载和屈曲结构发生屈曲响应时的模态形状的技术。
ansys结构屈曲分析
退出求解器
命令： 命令：finish GUI：close the ： solution menu
ANSYS 结构屈曲分析 二 结构屈曲分析的基本步骤
（3）扩展解：无论采取哪种特征值提取方法，如果想要得到屈曲模 ）扩展解：无论采取哪种特征值提取方法， 态的形状，就必须执行扩展解。 态的形状，就必须执行扩展解。可以 把扩展解简单理解为将屈曲 模态的形状写入结果文件。具体操作步骤如下： 模态的形状写入结果文件。具体操作步骤如下：
注意二： 注意二： 材料的弹性模量 EX必须定义。
ANSYS 结构屈曲分析 二 结构屈曲分析的基本步骤
（2）获得静力解：与一般静力解类似，但需注意以下几点： ）获得静力解：与一般静力解类似，但需注意以下几点：
注意一： 注意一：
必须激活预应力影响。 必须激活预应力影响。
注意二： 注意二：
通常只需施加一个单位荷 载即可。当施加单位荷载 载即可。 时，求解得到的特征值就 表示临界荷载， 表示临界荷载，施加非单 位荷载时， 位荷载时，求解得到的特 征值乘以施加的载荷就得 到临界荷载； 到临界荷载；
• 命令：mxpand,nmode,,,elcalc • GUI:main menu 〉solution 〉loads step opts 〉 expasionpass 〉single modes 〉expand modes
扩展求解
• 命令：solve • GUI:main menu 〉solution 〉solve 〉current LS
列出现在所有的屈曲荷载因子
命令：set，list 命令 GUI: mian menu 〉 general postproc 〉results summary
读取指定的模态来显示屈曲模态形状
ansys 屈曲分析详细过程
题目：跨径L=89m ，矢跨比f/L =1/5的圆弧拱，梁高h/L =1/30,梁宽b/L =1/15 求：1.弹性屈曲荷载；2.非线性极限承载能力。
1、 线性屈曲荷载理论计算在理论计算时，先根据圆弧拱的矢跨比查出稳定系数2K ：表1 圆弧拱理论计算的稳定系数根据表1查得：290.4K =故其理论弹性屈曲荷载为：43723313.25105933.332966.671290.4 5.381089000xcr EI N q K m l ⨯⨯⨯⨯==⨯=⨯2、拱的弹性屈曲与非线性屈曲对于一般的特征值屈曲分析，主要是在平衡状态，考虑到轴向力或者中面内力对弯曲变形的影响，由最小势能原理，结构弹性屈曲分析归结为求解特征值问题：通过特征值分析求得的解有特征值和特征向量，特征值就是临界荷载系数，特征向量是临界荷载系数对应的屈曲模态。
特征值屈曲分析的流程图如下：[][]0D G KK λ+=图1 弹性屈曲分析流程图非线性屈曲分析是考虑结构平衡受扰动（初始缺陷、荷载扰动）的非线性静力分析，该分析是一直加载到结构极限承载状态的全过程分析，分析中可以综合考虑材料塑性和几何非线性。
结构非线性屈曲分析归结为求解矩阵方程：非线性屈曲分析的流程图如下：图2 非线性屈曲分析流程图[][](){}{}DGK K F δ+=3、非线性方程组求解方法（1）增量法增量法的实质是用分段线性的折线去代替非线性曲线。
增量法求解时将荷载分成许多级荷载增量，每次施加一个荷载增量。
在一个荷载增量中假定刚度矩阵保持不变，在不同的荷载增量中，刚度矩阵可以有不同的数值，并与应力应变关系相对应。
（2）迭代法迭代法是通过调整直线斜率对非线性曲线的逐渐逼近。
迭代法求解时每次迭代都将总荷载全部施加到结构上，取结构变形前的刚度矩阵，求得结构位移并对结构的几何形态进行修正，再用此时的刚度矩阵及位移增量求得内力增量，并进一步得到总的内力。
（3）混合法混合法是增量法和迭代法的混合使用。
ansys 屈曲分析详细过程
非线性屈曲分析的流程图如下：
图 2 非线性屈曲分析流程图
2
3、非线性方程组求解方法 （1）增量法 增量法的实质是用分段线性的折线去代替非线性曲线。增量法求解时将荷载
分成许多级荷载增量，每次施加一个荷载增量。在一个荷载增量中假定刚度矩阵 保持不变，在不同的荷载增量中，刚度矩阵可以有不同的数值，并与应力应变关 系相对应。
图 4 荷载及拱的几何尺寸示意
几何尺寸： f/L=1/5， H/L=1/30，B/图L=图1图/15
L=89m，f=17.8m，H=2.97m，B=5.93m，R=64.5m
材料性能：拱圈采用 C40 混凝土，弹性模量为 32500MPa，泊松比为 0.3。
在 ANSYS 中进行建模分析，初始荷载为 q=100000kN/m 其过程如下：
0.5
K2
58.9
90.4
93.4
86.7
64.0
根据表 1 查得：
K2 90.4
故其理论弹性屈曲荷载为：
qcr
K2
EI x l3
3.25104 1 5933.33 2966.673
90.4
12 890003
5.38107
N
m
2、拱的弹性屈曲与非线性屈曲 对于一般的特征值屈曲分析，主要是在平衡状态，考虑到轴向力或者中面内
力对弯曲变形的影响，由最小势能原理，结构弹性屈曲分析归结为求解特征值问 题：
KD KG 0
通过特征值分析求得的解有特征值和特征向量，特征值就是临界荷载系数， 特征向量是临界荷载系数对应的屈曲模态。
特征值屈曲分析的流程图如下：
1
图 1 弹性屈曲分析流程图
非线性屈曲分析是考虑结构平衡受扰动（初始缺陷、荷载扰动）的非线性静 力分析，该分析是一直加载到结构极限承载状态的全过程分析，分析中可以综合 考虑材料塑性和几何非线性。结构非线性屈曲分析归结为求解矩阵方程：
ansys屈曲分析
3.1 几何非线性3.1.1 大应变效应一个结构的总刚度依赖于它的组成部件（单元）的方向和单刚。
当一个单元的结点经历位移后，那个单元对总体结构刚度的贡献可以以两种方式改变。
首先，如果这个单元的形状改变，它的单元刚度将改变（图3-1(a)）。
其次，如果这个单元的取向改变，它的局部刚度转化到全局部件的变换也将改变（图3-1（b））。
小的变形和小的应变分析假定位移小到足够使所得到的刚度改变无足轻重。
这种刚度不变假定意味着使用基于最初几何形状的结构刚度的一次迭代足以计算出小变形分析中的位移（什么时候使用“小”变形和应变依赖于特定分析中要求的精度等级）。
相反，大应变分析考虑由单元的形状和取向改变导致的刚度改变。
因为刚度受位移影响，且反之亦然，所以在大应变分析中需要迭代求解来得到正确的位移。
通过发出 NLGEOM，ON（GUI路径Main Menu>Solution>Analysis Options)，来激活大应变效应。
这种效应改变单元的形状和取向，且还随单元转动表面载荷。
（集中载荷和惯性载荷保持它们最初的方向。
）在大多数实体单元（包括所有的大应变和超弹性单元），以及部分的壳单元中大应变特性是可用的。
在ANSYS/Linear Plus程序中大应变效应是不可用的。
图3－1 大应变和大转动大应变过程对单元所承受的总旋度或应变没有理论限制。
（某些ANSYS单元类型将受到总应变的实际限制──参看下面。
）然而，应限制应变增量以保持精度。
因此，总载荷应当被分成几个较小的步，这可用〔 NSUBST， DELTIM， AUTOTS〕命令自动实现(通过GUI路径 MainMenu>Solution>Time/Frequent)。
无论何时如果系统是非保守系统，如在模型中有塑性或摩擦，或者有多个大位移解存在，如具有突然转换现象，使用小的载荷增量具有双重重要性。
3.1.2 应力－应变在大应变求解中，所有应力─应变输入和结果将依据真实应力和真实（或对数）应变（一维时，真实应变将表示为ε=Ln(l/l) 。
ANSYS中通过迭代求解真实特征值屈曲荷载
finish/clear/filname,bucklingforce=100offset=0.1/prep7et,1,beam4et,2,link10r,1,0.1*0.12,0.12*0.1**3/12,0.1*0.12**3/12,0.12,0.1 r,2,4e-6,2e-3mp,ex,1,2e11mp,prxy,1,0.27mp,dens,1,7800k,1,0,0,0k,2,0,0,5k,3,0,0,-5k,11,0.2,0,0k,12,-0.2,0,0k,13,0,0.2,0k,15,0,-0.2,0l,1,2l,1,3l,1,11l,1,12l,1,13l,1,15l,2,11l,2,12l,2,13l,2,15l,3,11l,3,12l,3,13l,3,15lsel,s,line,,1,6,1latt,1,1,1lesize,all,0.3lmesh,alllsel,invelatt,1,2,2lesize,all,,,1lmesh,allallsel,all/eshape,1/soludk,3,ux,,,,uy,uz,rotzdk,2,ux,,,,uyfk,2,fz,-forceantype,staticnlgeom,0pstres,1time,0autots,offnsubst,1solvefinish/soluantype,bucklebucopt,lanb,1solvefinish/post1set,lastpldispfinish所谓特征值失稳计算就是用结构材料刚度矩阵减去荷载作用下的几何刚度乘以一个系数λ，当总刚度矩阵奇异时，λ就是失稳特征值。
ANSYS在处理刚度矩阵时不能区分我们需要分析的外力荷载还是不需要的结构内力对几何刚度矩阵的贡献。
因此得到的特征值荷载是不正确的，必须通过迭代来解决该问题。
其基本思想就是根据第一次算出来的荷载放大倍数，调整加载结构上的外荷载，再重新求解特征值失稳放大倍数。
基于ANSYS的大型风力机塔筒的屈曲分析
模型进行简化" 对于整体的屈曲分析" 可按照单 一的尺寸进行结构简化& 忽略中间尺寸的变化" 取 塔筒的顶端直径为 $0*&* X" 顶端壁厚为"$0' XX" 底部直径为 %0&** X" 底部厚度为 $'0* XX" 对
单节的整体塔筒结构尺寸进行分析! 对整体的简 化影响不大$& 建立塔筒模型如图 " 所示&
g*0'(!
#J$
!'$
式中" (% O分别为弹性模量和泊松比" 代入得
$?为 "0'% k"*+ W8&
.
对局部带有门洞的屈曲
""/
"
相对细长比为
槡 /g
$T "$?
!)$
代入得 /g*0$"' l*0$&
其中 $?为屈服极限" 临界压缩应力 $QU为
{$T!!!!!!!!!/#*0$
$QUg
!,$
'g/-;
J #
!"*$
式中" /" ;表示影响系 数" 取 值 由 表 # 决 定&
表 中 & 代 表 孔 径 角" 当 & g$*q时 取 =$&&
! 6$%&M$ 下的 /" g*0,&" '" g*0**# "& 取 /g
*0,&" ;g*0**# "& 代入得 'g*0'+& 所以此塔筒
ansys 屈曲分析命令流
BucklingIntroductionThis tutorial was created using ANSYS 7.0 to solve a simple buckling problem.It is recommended that you complete the NonLinear Tutorial prior to beginning this tutorialBuckling loads are critical loads where certain types of structures become unstable. Each load has an associated buckled mode shape; this is the shape that the structure assumes in a buckled condition. There are two primary means to perform a buckling analysis:1.EigenvalueEigenvalue buckling analysis predicts the theoretical buckling strength of an ideal elastic structure. It computes the structural eigenvalues for the given system loading and constraints. This is known asclassical Euler buckling analysis. Buckling loads for several configurations are readily available from tabulated solutions. However, in real-life, structural imperfections and nonlinearities prevent most real-world structures from reaching their eigenvalue predicted buckling strength; ie. it over-predicts theexpected buckling loads. This method is not recommended for accurate, real-world buckling prediction analysis.2.NonlinearNonlinear buckling analysis is more accurate than eigenvalue analysis because it employs non-linear, large-deflection, static analysis to predict buckling loads. Its mode of operation is very simple: itgradually increases the applied load until a load level is found whereby the structure becomes unstable (ie. suddenly a very small increase in the load will cause very large deflections). The true non-linearnature of this analysis thus permits the modeling of geometric imperfections, load perterbations, material nonlinearities and gaps. For this type of analysis, note that small off-axis loads are necessary to initiate the desired buckling mode.This tutorial will use a steel beam with a 10 mm X 10 mm cross section, rigidly constrained at the bottom. The required load to cause buckling, applied at the top-center of the beam, will be calculated.ANSYS Command ListingEigenvalue BucklingFINISH ! These two commands clear current data/CLEAR/TITLE,Eigenvalue Buckling Analysis/PREP7 ! Enter the preprocessorET,1,BEAM3 ! Define the element of the beam to be buckledR,1,100,833.333,10 ! Real Consts: type 1, area (mm^2), I (mm^4), height (mm)MP,EX,1,200000 ! Young's modulus (in MPa)MP,PRXY,1,0.3 ! Poisson's ratioK,1,0,0 ! Define the geometry of beam (100 mm high)K,2,0,100L,1,2 ! Draw the lineESIZE,10 ! Set element size to 1 mmLMESH,ALL,ALL ! Mesh the lineFINISH/SOLU ! Enter the solution modeANTYPE,STATIC ! Before you can do a buckling analysis, ANSYS! needs the info from a static analysisPSTRES,ON ! Prestress can be accounted for - requiredanalysisbucklingduring!DK,1,ALL ! Constrain the bottom of beamFK,2,FY,-1 ! Load the top vertically with a unit load.! This is done so the eigenvalue calculated! will be the actual buckling load, since! all loads are scaled during the analysis.SOLVEFINISH/SOLU ! Enter the solution mode again to solve buckling ANTYPE,BUCKLE ! Buckling analysisBUCOPT,LANB,1 ! Buckling options - subspace, one modeSOLVEFINISH/SOLU ! Re-enter solution mode to expand info - necessary EXPASS,ON ! An expantion pass will be performedMXPAND,1 ! Specifies the number of modes to expandSOLVEFINISHpost-processorEnter/POST1!SET,LIST ! List eigenvalue solution - Time/Freq listing is the! force required for buckling (in N for this case). SET,LAST ! Read in data for the desired modePLDISP ! Plots the deflected shapeNonLinear BucklingFINISH ! These two commands clear current data/CLEAR/TITLE, Nonlinear Buckling Analysis/PREP7 ! Enter the preprocessorET,1,BEAM3 ! Define element as beam3MP,EX,1,200000 ! Young's modulus (in Pa)MP,PRXY,1,0.3 ! Poisson's ratioR,1,100,833.333,10 ! area, I, heightK,1,0,0,0 ! Lower nodeK,2,0,100,0 ! Upper node (100 mm high)Drawsline!L,1,2ESIZE,1 ! Sets element size to 1 mmLMESH,ALL ! Mesh lineFINISH/SOLUANTYPE,STATIC ! Static analysis (not buckling)NLGEOM,ON ! Non-linear geometry solution supportedOUTRES,ALL,ALL ! Stores bunches of outputNSUBST,20 ! Load broken into 5 load stepsNEQIT,1000 ! Use 20 load steps to find solution AUTOTS,ON ! Auto time steppingLNSRCH,ON/ESHAPE,1 ! Plots the beam as a volume rather than line DK,1,ALL,0 ! Constrain bottomFK,2,FY,-50000 ! Apply load slightly greater than predicted! required buckling load to upper nodeFK,2,FX,-250 ! Add a horizontal load (0.5% FY) to initiatebuckling!SOLVEFINISH/POST26 ! Time history post processorRFORCE,2,1,F,Y ! Reads force data in variable 2NSOL,3,2,U,Y ! Reads y-deflection data into var 3XVAR,2 ! Make variable 2 the x-axisPLVAR,3 ! Plots variable 3 on y-axis/AXLAB,Y,DEFLECTION ! Changes y label/AXLAB,X,LOAD ! Changes X label/REPLOT。
ANSYSWorkbench基础教程与工程分析详解第六章屈曲分析
工程中很多结构需要进行结构稳定性计算，如细长杆、压缩部件、真空容器等，这些构件在不稳定（屈曲）开始时，结构本质上没有变化的载荷作用下（超过一个很小的动荡），在x 方向上的微小位移会使得结构有一个很大的改变，这类问题除了要考虑强度之外，还要分析其屈曲稳定性的问题。
本章所要学习的内容包括： ¾ 了解线性屈曲分析基础¾ 掌握ANSYS Workbench 屈曲分析的操作流程 ¾ 了解线性屈曲分析的应用场合 ¾ 理解屈曲分析的结果6.1 线性屈曲分析基础特征值或线性屈曲分析预测的是理想线弹性结构的理论屈曲强度（分歧点）；而非理想和非线性行为阻止许多真实的结构达到它们的理论上的弹性屈曲强度。
线弹性通常产生非保守的结果，但也是有优点的。
（1）它比非线性屈曲计算省时间，并且应当做第一步计算来评估临界载荷（屈曲开始的载荷）。
（2）线性屈曲分析可以用来作为决定产生什么样的屈曲模型形状的设计工具，为设计做指导。
线性屈曲的分析方程为：{}([][])0i i K S λΨ+=式中各个符号的含义如下。
S 表示应力刚度矩阵； i λ表示屈曲载荷乘子；i Ψ表示屈曲模态。
实际上，线性屈曲方程和自由振动方程很相似，两者都是利用相似的矩阵方法来求解特征值问题的。
线性屈曲的分析步骤与之前的静力学分析非常相似，过程如下。
（7）求解计算并保存。
ANSYS Workbench1 4.5屈曲模态分析步骤与其他有限元分析步骤大同小异，软件支持模态分析中存在接触对，但因为屈曲分析是线性分析，所以接触行为不同于非线性接触行为，接触设置的线性屈曲分析设置如表6-1所示。
表6-1 存在接触设置的线性屈曲分析设置Linear Buckling Analysis（线性屈曲分析）Contact Type （接触类型） Initially Touching （初始接触） Inside Pinball Region （Pinball 区域内） Outside Pinball Region （Pinball 区域外） Bonded （绑定） Bonded （绑定） Bonded （绑定） Free （自由） No Separation （不分离） No Separation （不分离） No Separation （不分离） Free （自由） Rough （粗糙） Bonded （绑定） Free （自由） Free （自由） Frictionless （光滑）No Separation （不分离）Free （自由）Free （自由）6.2 案例图解6.2.1 斜撑杆受压屈曲分析分析起落架中承受轴向压力的斜撑杆，杆为空心圆管，外径为52mm ，内径为44mm ，L =950mm 。
ansys屈曲（Ansysbuckling）
ansys屈曲（Ansys buckling）03 string stability calculation (ANSYS)This example will discuss the eigenvalue instability and nonlinear instability of the string with prestressed stressKnowledge points:(a) prestressed(b) stable eigenvalues(c) consideration of the stability of eigenvalues of other internal forces(d) add initial defect(e) arc n(f) nonlinear analysis and convergence(g) relationship of load displacement(1) set the Parameters of analysis. In the top menu of ANSYS, parameter-> Scalar Parameters, input in the pop-up Scalar Parameters window, FORCE = 100, OFFSET = 0.1.(2) establish a model. In this example, we will contact two new units, three-dimensional Beam unit Beam 4 and 3d cable unit Link 10. The Beam 4 unit is simpler than the Beam 188 unit introduced before, and is also a useful unit for the common rectangularelastic cross section. Link 10 is the space cable unit provided by ANSYS. The user can control the unit only under pressure or can only be pulled. By default, the unit can only be pulled.(3) select Beam 4 units and Link 10 units in the ANSYS main menu Preprocessor - > Element type - > Add/Edit/Delete(4) both Beam 4 and Link 10 can use real parameters to set the section properties. First, the section of the Beam 4 unit is set. The cross section we want to build is a rectangular section of 0.1 m by 0.12 m. If the Beam 4 unit does not specify the direction of the main axis of the section, the Y-axis of the partial coordinate system of the section will be parallel to the x-y plane of the whole coordinate system. In the ANSYS main menu Preprocessor - > Real Constants - > Add/Edit/Delete, select Add, the associated unit type of the specified Real parameter is Beam 4 unit, and the input section parameter is AREA: 0.1 * 0.12, IZZ: 0.12 * 0.1 * * 3/12, IYY: 0.1 * 0.12 * 3/12, TKZ: 0.12, TKY: 0.1, as shown in the figure below(5) continue to add the second real parameter type, and specify that the second real parameter is associated with the Link 10 unit. The sectional area of the Link 10 unit is 4 x 10-6m2, and the initial strain is 2 x 10-3. The initial strain is the strain of strain.(6) the material properties are set below. In this example, all materials are set as steel for simplicity. Add Material properties to the ANSYS main menu Preprocessor - > Material Props - > Material Models. In the Material window, select the Structural - > Linear - > Elastic - > Isotropic, input Elasticmodulus 2 x 109 and poisson ratio 0.27, also can input the Density of the Material, select the Structural - > Density in the Material window, and the input Density is 7800.(7) the geometric model is established. In this example, we still construct geometric models strictly according to the points, lines, planes and body topologies that are required by the modeling process of ANSYS.(8) the key points are established In the ANSYS main menu Preprocessor - > Modeling - > Create - > Keypoints - > In Active CS(9) connect the key points below and connect the following key points in the ANSYS main menu Preprocessor - > Modeling - > create-> Lines - > Straight LineGet the string model(10) to divide the grid by geometry. In the ANSYS main menu Preprocessor - > meshing-> Mesh Attributes - >, line 1, select 1 ~ 6 straight line, setting its unit type, material type and real parameter are all 1. Select the line 7-14, the material type is 1, the unit type and the real parameter are both 2.(11) control the size of the grid. For the analysis, in the middle of the column is the key of the research, the mesh so we want to have to close some, in the ANSYS Preprocessor main menu - > Meshing - > Size Cntrls - > Lines - > Picked Lines, select 1 ~ 6 straight Lines, set the maximum Length of grid unit (Element Edge Length) of 0.3. For the surrounding prestressedcables,Since Link 10 is a relatively complex nonlinear unit, it is easy to solve the difficult convergence problem when solving the problem. Therefore, we divide the prestressed cable into one unit. Select the line 7 ~ 14, and set the number of grid segments as 1.(12) in the ANSYS main menu Preprocessor - > meshing-> Mesh - > Lines, select all the Lines and divide the grid(13) at the top of ANSYS, the menu plotctrls-> Style -- > Size and shape, set Display of element as On. Get the unit shape as shown in the figure:(14) the boundary condition and load are added under the model. Main menu first into the ANSYS Solution - > Define Loads - > Apply - > Structural - > below - > On Keypoints, selected key point 3, constraint three horizontal movement dof UX, UY, offers and rotational degree of freedom ROTZ, select the point 2, two translational degree of freedom UX and UY constraints.(15) enter the ANSYS main menu Solution - > Define Loads - > Apply - > struck-> Force/Moment - > One Keypoints, select key point 2, load direction of FZ and size - Force(16) to conduct a Static Analysis, Solution main menu - > into ANSYS Analysis Type - > New Analysis, set for the Static Analysis of types, into the Solution - > Analysis Type - > Sol 'n Controls, set for small deformation Analysis and consider prestressed, close the automatic time step control steps andset Analysis child (Substeps) to 1(17) for a Solution operation, enter the ANSYS main menu Solution - > Solve - > Current LS.(18) the eigenvalue buckling of the model is solved. Solution main menu - > into ANSYS Analysis Type - > New Analysis, set Analysis of Type Eigen Buckling, Solution main menu - > into ANSYS Analysis Type - > Analysis Options, set the Solution of the first-order stable load.(19) to Solve the operation again, enter the ANSYS main menu Solution - > Solve - > Current LS.(20) into the post-processing operation at this moment, the main menu into ANSYS General Postproc - > Read the results - > the Last Set, Read in the Last step as a result, the main menu select ANSYS General Postproc - > Plot results - > Deformed Shape, they can get form of instability of the structure and the corresponding buckling load magnification, which is 118.602, as shown.(21) enter the Parameters - > Get scalar data at the top of ANSYS, select Results data in Get scalar data, and select Model Results (modal result) in the result, as shown in the figure. Click OK to go to the next window Get Model Results, and select the variable that will store the modal result in the name Freq1. Modal is the first order mode.(22) from the top window of the ANSYS window, the first-order frequency is 118.6021, as shown in the figure(23) the above process is the general process of analyzing eigenvalue instability. However, ANSYS has a defect in the process of analyzing eigenvalues instability. As is known to all, the so-called eigenvalue buckling calculation is to use the structure stiffness matrix minus the geometric stiffness of the structure under load multiplied by a coefficient, when the total stiffness matrix singularity is buckling eigenvalues. ANSYS in dealing with a load caused by stiffness matrix cannot differentiate between we need analysis of the external force load (in this case is top concentration) and don't need the structure of the internal force (for example, the calculation of prestressed) contribution to the geometric stiffness matrix. Therefore, it is incorrect to get the eigenvalue yield of 118602N (equal to the initial value of the initial value of 100 x eigenvalue instability of 118.602). Therefore, the problem must be solved through the following iterative calculation.(24) the basic idea of iterative calculation is to adjust the external load on the structure and to solve the eigenvalue instability magnification of the new load according to the magnification of the load.Repeat the above operation until the magnification of the eigenvalue instability is basically equal to 1. The external load added to the structure is the real eigenvalue instability load. And it doesn't contradict the internal forces. The command flow for iterative computing is as follows:! Set the maximum number of iterations 100 times* to DO, I, 1100,FINISH/ SOLU! Apply new load to the structureFk1 - FK, 2, FZ - FORCE! Static analysisANTYPE, 0! Set time1 TIME,AUTOTS, 0NSUBST, 1,,, 1SSTIF, ONSOLVEFINISH! The eigenvalue instability analysis is carried out / SOLUANTYPE, BUCKLE! Buckling analysisBUCOPT, LANB, 1! Use Block Lanczos solution method, extract 1 modeMXPAND, 1! Expand 1 mode shapePSTRES, ON! The INCLUDE PRESTRESS EFFECTSSOLVEFINISH! The first order frequency of the current eigenvalue instability (magnification)* GET FREQ1, MODE, 1, FREQ* the IF, ABS (FREQ1-1), LT, 0.01, THEN! If the frequency error is less than 1%, exit the loop* the EXIT* ENDIFThe FORCE = FORCE * FREQ1! Otherwise, the load times the new magnification is calculated again* ENDDO(25) after repeating the above process, the structure of real eigenvalue buckling load of 198174 n, visible if does not exclude the prestressed internal force of the influence of the geometric stiffness matrix, calculated the eigenvalue buckling load (118602 n) are much smaller.(26) finally, we have a nonlinear buckling analysis. The buckling load calculated by eigenvalue instability is actually the upper limit solution for ideal material. Due to various initial defects or nonlinear effects of materials, the instability load of the actual structure is usually smaller than that of the eigenvalue. Therefore, nonlinear instability analysis is necessary. In nonlinear instability analysis, initial defects need to be introduced. There are many ways to choose the initial defect, and it is more commonly used to add the eigenvalue instability shape of the structure as the most unfavorable initial defect to the structure. The UPGEOM command is provided in ANSYS to facilitate the implementation of the above process, as described below(27), first of all, we need to get the largest eigenvalue buckling mode of the structure deformation is how much, the first main menu in the ANSYS General Postpro Results - > - > List are Sorted Listing - > Sort Nodes, choose the Results of the total displacement (USUM), the maximal displacement of all Nodes.(28) next, select Parameters - > Get Scalar Data in the top menu of ANSYS and select Results Data - > Other operations in Get Scalar Data(29) in the Get Data from Other POST1 Operations window, select the Data from the sorting result that you just did. The required data is the maximum of the sorted order, which is placed in the DMAX variable.(30) DMAX = 1 can be seen from the Scalar Parameter window(31) use the UPGEOM command to adjust the shape of the structure and apply the initial defect. Select Preprocessor - > Modeling - > Update Geom in the ANSYS main menu. UPGEOM will read the structure from the result file and adjust the geometry of the structure. We set the magnification multiple as OFFSET/DMAX, i.e. the maximum initial defect we need is OFFSET = 0.1, and the maximum deformation in the result file is DMAX, so the magnification ratio is OFFSET/DMAX. Finally, the result of the specified eigenvalue instability analysis is called Case03. RST.(32) after the geometry of the structure has been updated, the nonlinear solution can be performed. We know that the load of the eigenvalue instability of the structure is 198174N, and the maximum load of the structure is the loss of the stability load of the characteristic value of three times, which is the input field in the top of the ANSYS window. The load loading structure is constructed, and the analysis type is set to static analysis.(33) in the end, we have to set the solution method in the solver control.This will automatically track the failure path. Enter the ANSYS main menu Solution - > Analysis Type - > Analysis Options. First,set the Analysis Type in the basic option to analyze the large displacement, and consider the prestress. Set the analysis substeps for 20 steps and output the results per step.(34) select the Advanced NL page in the Solution Controls window, and click on the arc-length Method, which USES the default values for the arc-length Method.Main menu (35) into ANSYS Solution - > Solve - > Current LS, began to calculate the Current problem, because the problem is that we come into contact with the first nonlinear problem, it is necessary to introduce the meaning of the output in ANSYS nonlinear calculation window. Nonlinear computing as we know, there is a convergence problem, in this example, the ANSYS output in the reprocessing window four computing intermediate variables: 2 norm of unbalanced force (F L2), unbalanced force closed then poor (F CRIT), 2 norm of unbalanced moment of L2 (M) and the unbalanced moment then sent CRIT (M). The horizontal axis in the window is the time (calculation process), and the ordinate is the corresponding value. In the case of force, if the two norm of the unbalanced force (F L2) is higher than the unbalance force, the F CRIT indicates that there is no convergence, and the calculation is to be continued. If (F L2) is less than (F CRIT), the two curves of (F L2) and (F CRIT) in the graph intersect, indicating that the step calculation has been convergent and the next load step can be calculated. In this case, the case of convergence is still good, and the general iteration converges once or twice.(36) after the calculation has been completed, the post-stroke processor enters ANSYS, selects TimeHist Postpro, and clicksthe variable button in the toolbar in Time History Variables to select add node Z direction deformation, as shown in the figure. Select node 2.(37) in the Time History Variables window set for UZ_2 X coordinates, Time to light up as Y-axis, click on the plot button on the toolbar, you can get the relative load as shown - vertex deformation curve.In General Postproc, the General Postproc - > Read Results - > By Time/Freq was selected, and the display Time was 0.2 (i.e. the maximum load equivalent to 1/5), and the General Postproc - > Plot Results - > Deformed Shape of ANSYS main menu was selected. Draw the current deformation of the structure as shown. Gradually increase the result Time, showing the deformation of Time = 0.4 and 0.6.。
ansys屈曲临界荷载系数
ansys屈曲临界荷载系数英文版ANSYS Buckling Critical Load FactorIn the realm of engineering analysis, ANSYS stands tall as a reliable and comprehensive finite element analysis software. Among its many applications, one of the most significant is the calculation of critical load factors, particularly in the context of buckling analysis. Buckling, a phenomenon where a structure loses its stability under compressive loads, is a crucial aspect to consider in the design and safety assessment of various engineering structures.The buckling critical load factor, often denoted as the eigenvalue or critical load multiplier, represents the ratio of the applied compressive load to the load that would cause the structure to buckle. This factor is crucial in determining the stability of a structure and helps engineers assess its ability to withstand compressive loads without failing.Using ANSYS, engineers can perform detailed buckling analysis to determine the critical load factors of their structures. This software offers a range of tools and features that allow for accurate and efficient analysis. By simulating real-world conditions and loads, ANSYS can provide valuable insights into the structural behavior of a system, enabling engineers to make informed decisions about design modifications or material selections.The application of ANSYS in buckling analysis is not limited to any specific industry. It finds widespread use in civil engineering, mechanical engineering, aerospace, and numerous other fields where the stability of structures under compression is a critical consideration. By leveraging the power of ANSYS, engineers can ensure that their designs are robust, safe, and reliable.中文版ANSYS屈曲临界荷载系数在工程分析领域，ANSYS作为一款可靠且全面的有限元分析软件，备受信赖。
Ansys120Mechanical教程-6线性屈曲分析
Ansys120Mechanical教程-6线性屈曲分析本章将介绍线性屈曲分析。
内容:A.屈曲的背景知识;B.屈曲分析步骤Workbench-MechanicalIntroduction7-1本章将介绍线性屈曲分析。
内容:A.屈曲的背景知识;B.屈曲分析步骤简介本章将介绍线性屈曲分析。
内容:A.屈曲的背景知识B屈曲分析步骤B.C.Workhop7-1TrainingManual本章所述的功能，一般可用于ANSYSDeignSpaceEntra及以上版本的许可。
–本章讨论的某些选项可能需要更高级的许可，但这些都指出相应的许可。
本章将介绍线性屈曲分析。
内容:A.屈曲的背景知识;B.屈曲分析步骤A.屈曲的背景知识TrainingManual需要评价许多结构的稳定性。
在薄柱，压缩部件，和真空罐的例子中，稳定性是重要的。
失稳（屈曲）的结构，负载基本上没有变化（超出一个小负载扰动）会有失稳曲的结构负载基本上有变化超出个小负载扰动会有一个非常大的变化位移{Δ某}F稳定的不稳定的F本章将介绍线性屈曲分析。
内容:A.屈曲的背景知识;B.屈曲分析步骤…屈曲的背景知识特征值或线性屈曲分析预测理想线弹性结构的理论屈曲强度。
此方法相当于教科书上线弹性屈曲分析的方法。
此方法相当于教科书上线弹性屈曲分析的方法–用欧拉行列式求解特征值屈曲会与经典的欧拉解一致。
TrainingManual缺陷和非线性行为使现实结构无法与它们的理论弹性屈曲强度一致缺陷和非线性行为使现实结构无法与它们的理论弹性屈曲强度致。
线性线性屈曲一般会得出不保守的结果。
线性屈曲无法解释的问题–非弹性的材料响应。
–非线性作用。
–不属于建模的结构缺陷（凹陷等）。
本章将介绍线性屈曲分析。
内容:A.屈曲的背景知识;B.屈曲分析步骤…屈曲的背景知识尽管不保守，线性屈曲有多种优点：TrainingManual–它比非线性屈曲计算省时,并且可以作第一步计算来评估临界载荷(屈曲开始时的载荷).在屈曲分析中做一些对比可以体现二者的明显不同–线性屈曲分析可以用来作为确定屈曲形状的设计工具具.结构屈曲的方式可以为设计提供向导本章将介绍线性屈曲分析。