ansys学习非线性静态分析实例
ANSYS非线性分析指南
非线性结构分析非线性结构的定义在日常生活中，会经常遇到结构非线性。
例如，无论何时用钉书针钉书，金属钉书钉将永久地弯曲成一个不同的形状。
（看图1─1（a））如果你在一个木架上放置重物，随着时间的迁移它将越来越下垂。
（看图1─1（b））。
当在汽车或卡车上装货时，它的轮胎和下面路面间接触将随货物重量的啬而变化。
（看图1─1（c））如果将上面例子所载荷变形曲线画出来，你将发现它们都显示了非线性结构的基本特征--变化的结构刚性.图1─1 非线性结构行为的普通例子非线性行为的原因引起结构非线性的原因很多，它可以被分成三种主要类型：状态变化（包括接触）许多普通结构的表现出一种与状态相关的非线性行为，例如，一根只能拉伸的电缆可能是松散的，也可能是绷紧的。
轴承套可能是接触的，也可能是不接触的，冻土可能是冻结的，也可能是融化的。
这些系统的刚度由于系统状态的改变在不同的值之间突然变化。
状态改变也许和载荷直接有关（如在电缆情况中），也可能由某种外部原因引起（如在冻土中的紊乱热力学条件）。
ANSYS程序中单元的激活与杀死选项用来给这种状态的变化建模。
接触是一种很普遍的非线性行为，接触是状态变化非线性类型形中一个特殊而重要的子集。
几何非线性如果结构经受大变形，它变化的几何形状可能会引起结构的非线性地响应。
一个例的垂向刚性）。
随着垂向载荷的增加，杆不断弯曲以致于动力臂明显地减少，导致杆端显示出在较高载荷下不断增长的刚性。
图1─2 钓鱼杆示范几何非线性材料非线性非线性的应力──应变关系是结构非线性名的常见原因。
许多因素可以影响材料的应力──应变性质，包括加载历史（如在弹─塑性响应状况下），环境状况（如温度），加载的时间总量（如在蠕变响应状况下）。
牛顿一拉森方法ANSYS程序的方程求解器计算一系列的联立线性方程来预测工程系统的响应。
然而，非线性结构的行为不能直接用这样一系列的线性方程表示。
需要一系列的带校正的线性近似来求解非线性问题。
ANSYS教程,非线性结构分析过程
ANSYS教程，非线性结构分析过程尽管非线性分析比线性分析变得更加复杂，但处理基本相同。
只是在非线形分析的适当过程中，添加了需要的非线形特性。
非线性结构分析的基本分析过程也主要由建模、加载并求解和观察结果组成。
下面来讲解其主要步骤和各个选项的处理方法。
建模这一步对线性和非线性分析都是必需的，尽管非线性分析在这一步中可能包括特殊的单元或非线性材料性质，如果模型中包含大应变效应，应力─应变数据必须依据真实应力和真实（或对数）应变表示。
加载求解在建立好有限元模型之后，将进入ANSYS求解器(GUI：Main Menu | Solution)，并根据分析的问题指定新的分析类型(ANTYPE)。
求解问题的非线性特性在ANSYS中是通过指定不同的分析选项和控制选项来定义的。
非线性分析不同于线性分析之处在于，它通常要求执行多荷载步增量和平衡迭代。
下面就详细讲解一下进行非线性结构分析需要定义的各个求解选项、分析选项和控制选项是如何设置的，以及他们的意义是什么。
求解控制对于一些基本的非线性问题的分析选项，可以通过ANSYS提供的求解控制对话框中的选项设置来完成。
选择菜单路径：Main Menu | Solution | Analysis Type | Sol’n Controls，将弹出求解控制(Solution Controls)对话框，如下图所示。
从图中可以看出该对话框主要包括5个选项卡：基本选项（Basic）、瞬态选项（Transient）、求解选项（Sol’n Options）、非线性选项（Nonlinear）和高级非线性选项（Advanced NL）。
如果开始一项新的分析，在设置分析类型和非线性选项时，选择“Large Displacement Static”选项（不是所有的非线性分析都支持大变形）。
如果想要重新启动一个失败的非线性分析，则选择“Restart Current Analysis”选项。
选中下面的“Calculate prestress effects”单选按钮用于有预应力的模态分析时的预应力计算，具体内容见模态分析部分。
ansys学习-非线性静态分析实例
ansys学习－非线性静态分析实例问题描述一个子弹以给定的速度射向壁面。
壁面假定是刚性的和无摩擦的。
将研究子弹和壁面接触后达80微秒长的现象。
目的是确定子弹的整个变形，速度历程，以及最大等效Von Mises应变。
求解使用SI单位。
用轴对称单元模拟棒。
求解最好能通过单一载荷步实现。
在这个载荷步中，将同时施加初始速度和约束。
将圆柱体末端的节点Y方向约束住以模拟一固壁面。
打开自动时间分步来允许ANSYS 确定时间步长。
定义分析结束的时间为8E-5秒，以确保有足够长的时间来扑捉整个变形过程。
问题详细说明下列材料性质应用于这个问题：EX=117.0E09 (杨氏模量）DENS=8930.0 （密度）NUXY=0.35（泊松比）Yield Strength=400.0OE06（屈服强度）Tangent Modulus （剪切模量）下列尺寸应用于这个问题：长=32.4E-3m直径=6.4E-3m对于这个问题的初始速度是227.0。
图1铜圆柱体图解求解步骤：步骤一：设置分析标题1、选择菜单路径：Utility Menn>File>ChangeTitle。
2、键入文字“Coppery Cylinder Impacting a Rigid Wall”3、单击OK。
步骤二：定义单元类型1、选择菜单路径Mail Menu>Preprocessor>Element Type>All/Edit/Delete。
2、单击Add。
Library of Element Types(单元类型库）对话框出现。
3、在靠近左边的列表中，单击“Visio Solid”仅一次。
4、选靠近右边的列表中，单击“4node Plas 106”仅一次。
5、单击OK。
Library of Element Types 对话框关闭。
6、单击Options (选项）。
VISCO106 element type Options(visco106单元类型选项）对话框出现。
应用ANSYS实现几何非线性分析方法
应用ANSYS实现几何非线性分析方法摘要：本文简要介绍了用ANSYS对杆系结构进行非线性分析时应当注意的问题及方法。
通过Williams双杆体系这个算例来介绍几何非线性全过程分析，表明ANSYS软件丰富的单元库、强大的求解器以及便捷的后处理功能，对工程结构进行非线性分析不失为一种很好的方法。
关键词：杆系结构；几何非线性ANSYS；全过程分析BEAM3对于许多工程问题，结构的刚度是变化的，必须用非线性理论解决，而几何非线问题就是非线性理论中的一类。
因几何变形引起的结构刚度变化的一类问题都属于几何非线性问题。
几何非线性理论一般可以分成大位移小应变即有限位移理论和大位移大应变理论即有限应变理论。
其核心是由于结构的几何形状或位置的改变引起结构刚度矩阵发生变化，也就是结构的平衡方程必须建立在变形后的位置上。
ANSYS程序充分考虑了这两种理论。
ANSYS所考虑的几何非线性通常分为3类：①大应变，即认为应变不再是有限的，结构本身的形状可以发生变化，结构的位移和转动可以是任意大小；②大位移，即结构发生了大的刚体转动，但其应变可以按照线性理论来计算，结构本身形状的改变可以忽略不计；③应力刚化，是指单元较大的应变使得单元在某个面内具有较大的应力状态，从而显著影响面外的刚度。
大应变包括大位移和应力刚化，此时应变不再是“小应变”，而是有限应变或“大应变”；大位移包括了其自身和应力刚化效应，但假定为“小应变”；应力刚化被激活时，程序计算应力刚度矩阵并将其添加到结构刚度矩阵中，应力刚度矩阵仅是应力和几何的函数，因此又称为“几何刚度”。
几何非线性问题一般指的是大位移问题，只有在材料发生塑性变形时，以及类似橡皮这样的材料才会遇到的大的应变，大变形一般包含大应变、大位移和应力刚化，而不加区分。
1几何非线性分析应注意的问题用ANSYS进行几何非线性分析时，首先要打开大位移选项，即（NLGEOM，ON），并设置求解控制选项，可根据问题类型而定。
【ANSYS非线性分析】4-非线性分析方法
01112121222y y d N d d R d M d d R ελφ⎧⎫
⎧⎫⎡⎤⎧⎫=∆+⎨⎬⎨⎬⎨⎬⎢⎥
⎣⎦⎩⎭
⎩⎭⎩⎭ 改写为，
11112021222y y d N R d d d d M R d d εφλ-⎡⎤⎧⎫⎧⎫
⎧⎫=-⎨⎬⎨⎬⎨⎬⎢⎥
-⎩⎭⎩⎭⎩⎭
⎣⎦ 求解过程中，可控制d φy 的值，求出相应的0d ε及荷载增量比例因子d λ。
由于ij d 与截面应变平面有关，需要迭代才能使截面补平衡力12,R R 趋近于零。
图4-9 位移控制法 在结构分析中控制指定位移增量，则P —δ曲线的下降段不难求得。
将底端固定顶端自由的柱，在柱顶端施加水平荷载，将柱的加载点处换为支座，而分析时控制该支座位移并求出该支座的反力，图4—9表示了得到的全过程分析P-δ曲线。
对于一般结构，将刚度矩阵重新排列，使得选择的控制位移排到最后，将原矩阵分块表示成以下形式，
111211121
22222K K du P R K K du P R ⎡⎤⎧⎫⎧⎫⎧⎫=∆+⎨⎬⎨⎬⎨⎬⎢⎥⎣⎦⎩⎭⎩⎭⎩⎭
λ 改写方程为，
11
11121221
2222K P R K du du K P R K -⎡⎤⎧⎫⎧⎫⎧⎫
=-⎨⎬⎨⎬⎨⎬⎢⎥-∆⎩⎭⎣⎦⎩⎭⎩⎭
λ 需要指出的是，改写以后的系数矩阵是不对称的，也不是带状的，求解时需要较多的存储单元。
§4.5.4 修正完善后的弧长法 1．弧长法的基本原理
仍从结构增量平衡方程：{}{}{}11i i i i K w P g --=-∆∆λ∆。
ANSYS-6-非线性分析应用
第六章 钢筋混凝土结构非线性分析应用§6.1截面非线性分析例 1: 钢筋混凝土单筋矩形截面，混凝土和钢筋的应力-应变关系选自CEB 模型规范（1990），见下图6-1-1，图 6.1-1 截面和材料应力-应变关系极限弯矩 M u : 用弧长法对截面进行全过程分析，对给定的弯矩M y , 计算相应的截面应变平面({}[]T z y ϑϑεε0=).计算不平衡弯矩及相应的应变平面增量，直至满足收敛条件。
再增加弯矩∆M y , 计算相应的应变平面增量，等等，图6-1-2为截面弯矩-曲率关系曲线。
图 6.1-2 弯矩-曲率关系曲线 例2: 采用不同应力-应变关系（EC2规范, CEB 规范），钢筋混凝土矩形截面的几何尺寸和配筋同例1，非线性分析结果见图6-1-4。
力-应变关系随应变而逐渐的降低，截面刚度降低的也比较缓慢。
图 6.1-4 CEB 规范与EC2 规范建议的应力-应变关系截面分析结果比较例 3: 异形截面非线性分析. 此例Georg Knittel [32]计算过，Knittel 选择的材料应力应变关系取自德国规范DIN 1045(见图 6.1-5). 截面形状和尺寸见图6.1-6. Knittel 分析的截面极限承载力为，{}{}N M M y z T T=--005026000075... 相应的应变矢量为，{}{}{}TT z y 009343.0006976.0004359.00--==ϑϑεε. 用弧长法分析时取的参照荷载值为，{}{}N M M yz T T =--00050026000075... 截面极限荷载为，{}{}N M M y z T T =--004991490263211600076718...(a) DIN 1045建议的混凝土应力-应变关系 (b) DIN 1045建议的钢筋应力-应变关系图 6.1-5 DIN 1045规范建议的应力-应变关系图 6.1-6 钢筋混凝土柱截面图 6.1-7 极限状态时混凝土压应力分布图 6.1-8 弯矩-曲率(M y- y) 关系曲线§6.2 受弯和偏压构件非线性分析6.2.1 简化计算利用虚功原理计算荷载挠度曲线：设两点集中加载简支梁，弯矩图、曲率分布图如下，图6-2-1 梁内力与变形取支撑条件相同的简支梁为虚梁，拟求跨中挠度，在虚梁跨中施加单位荷载（求转角加单位力矩）。
非线性分析实例
ansys非线性分析实例(1) 设定分析参数，在ANSYS顶部菜单Parameters->Scalar Parameters，在弹出的Scalar Parameters窗口中输入，FORCE=100，OFFSET=0.1。
(2) 建立模型，在本算例中，我们将接触两种新的单元，三维梁单元Beam 4和三维索单元Link 10。
Beam 4单元在参数定义等方面比前面介绍的Beam 188单元简单，对于常见的矩形弹性截面，也是一个很实用的单元。
Link 10单位为ANSYS提供的空间索单元，用户可以控制该单元只能受压或者只能受拉，默认该单元只能受拉。
(3) 在ANSYS主菜单Preprocessor->Element type->Add/Edit/Delete中选择Beam 4单元和Link 10单元(4) Beam 4单元和Link 10单元都可以通过实参数来设置截面属性。
首先设置Beam 4单元的截面。
我们要建立的截面是一个0.1m×0.12m的矩形截面。
Beam 4单元如果没有指定截面主轴方向，则截面局部坐标系的Y轴方向将和整体坐标系的X-Y平面平行。
在ANSYS 主菜单Preprocessor->Real Constants->Add/Edit/Delete，选择Add，指定实参数的关联单元类型为Beam 4单元，输入截面参数为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, 如下图所示(5) 继续添加第二个实参数类型，指定第二个实参数与Link 10单元相关。
取Link 10单元的截面积为4×10-6m2，初始应变为2×10-3，这里正的表示初始应变为拉应变。
(6) 下面设定材料属性，在本例子中为了简单起见，所有材料都设定为钢材。
ANSYS非线性分析
11.2 结构(jiégòu)非线性分析
➢ (4) Nonlinear标签
➢ Nonlinear标签局部(bù fen)选项及界面如表11-2及图11-4所示 。
第十六页，共204页。
11.2 结构(jiégòu)非线性分析
• 1.进入求解(qiú jiě)控制对话框 • GUI：【Main Menu】/【Solution】/【Analysis Type】/【Sol'n
Controls】 • 弹出求解(qiú jiě)控制对话框，如图11-1所示。此时的求解(qiú jiě)
用途 指定方程求解器 对于多重启动指定参数
第二十三页，共204页。
11.2 结构(jiégòu)非线性分析
图11-3 Sol'n Options标签(biāoqiān)界面
第二十四页，共204页。
11.2 结构(jiégòu)非线性分析
• ANSYS的自动求解控制在大多数情况下，激活稀疏矩阵直接求解器，即缺 省的求解器，其他选项包括(bāokuò)直接求解器和PCG求解器。对于在三 维模型中实体单元使用PCG求解器可能更快。假设用PCG求解器，而且是 小应变静力或完全瞬态分析，可以考虑用MSAVE命令降低内存应用。其他 情况，可用刚度矩阵的总体安装来求解。对于符合上述条件的结构，用 MSAVE,ON 可能可节省70%的内存，但求解时间可能增加，这与计算机的 配置和CPU速度有关。稀疏矩阵求解器是一个健壮的求解器。虽然PCG求 解器能够求解同样的矩阵方程，但在它碰到一个病态矩阵时，求解器将反 复指定的迭代数目，并在收敛失败时停止。在发生这种问题时，它触发二 分。在完成二分后，求解器继续求解，如果结果矩阵是良态的话，最后可 以求解整个非线性载荷步。稀疏矩阵求解器在梁、壳或者梁、壳、实体结 构，病态问题，不同区域材料特性相差巨大的模型以及位移边界条件缺乏 的情况下可得到满意解；PCG求解器在三维结构且自由度数相对较大时使 用。
ansys非线性分析例子
4.9 选择Main Menu>Solution>Load Step Opts>Write LS File,在对话框中输入 3，单击OK,如下图所 示
4.10 选择Main Menu>Solution>Solve >From LS Files，弹 出如下对话框，并进 行如下设置单击ok
5.1 选择Main Menu>General Postproc>Read Results>First Set,读取第一个载荷步的求解结果 5.2 Main Menu>General Postproc>plot Results>Contour Plot>Nodal Solu,弹出如下对 话框，并进行如下页的设置
/GO D,P51X, , , , , ,ALL, , , , , FLST,2,1,1,ORDE,1 FITEM,2,10 !* /GO F,P51X,FY,-12 FLST,2,1,1,ORDE,1 FITEM,2,10 !* /GO F,P51X,FX,0.05 LSWRITE,1, FLST,2,1,1,ORDE,1 FITEM,2,10 !* /GO F,P51X,FY,-13 FLST,2,1,1,ORDE,1 FITEM,2,10 !* /GO F,P51X,FX,0.05 LSWRITE,2, FLST,2,1,1,ORDE,1 FITEM,2,10 !*
1.1 单击 开始>所有 程序 >ansys12.1>mench anical APDL Product Launcher窗口如左图。 在working Directory 栏中设置工作目录， 在job name中输入如 左图所示的工作名。 单击Run,进入ansys。
ANSYS几何非线性和线性对比分析的一个工程实例
ANSYS 非线性和线性对比分析的一个工程实例二力杆几何非线性分析土木工程中，钢模板由于制作不精细或搬运模板过程受到碰撞或者挤压等外力作用常常会造成模板某处凸起，在活、恒载作用下或搬运过程中，该处常常会突然从凸起变成凹进状态。
这一现象被称为油罐效应，通常采用桁架的失稳模型进行几何非线性简化分析，因为也称为桁架的经典跳越问题。
分析模型如图1所示，采用LINK1单元构成二力杆，两端完全约束，中间节点加集中力。
图1荷载与顶点位移理论关系为：0(sin )(2sin )P EA x x x θθ=--式中，E 为弹性模量，0A 为杆件初始截面积，x=V/0L ,V 为顶点的竖向位移，0L 为杆长，θ为杆件倾角。
分析中取0A =102mm ,E=200Gpa, 0L =100mm, θ=06。
分析所用的非线性命令流如下。
!********************** 二力杆几何非线性分析************************ FINI/CLEAR/FILENAME,NONLINEAR_ER-LI-GAN/TITLE,The Analysis of NONLINEAR_ER-LI-GAN/PREP7/PNUM,LINE,1/PNUM,KP,1LO=100CTA=6*AFUN,DEGL1=2*LO*COS(CTA)H1=LO*SIN(CTA)AA=10EM=2E5ET,1,LINK1MP,EX,1,EMR,1,AAK,1K,2,0.5*L1,H1K,3,L1L,1,2$L,2,3LESIZE,ALL,,,1 LMESH,ALLFINI/SOLUDK,1,ALLDK,3,ALLFK,2,FY,-1200 ANTYPE,0NLGEOM,1NSUBST,100 OUTRES,ALL,ALL ARCLEN,ONSOLVEFINI/POST1/ESHAPE,1EPLOTSET,LASTPLDISP,1 !绘制变形图PRRSOLFINI/POST26NSOL,2,2,U,Y,DISPLACEMENTABS,3,2RFORCE,4,1,F,Y,F/AXLAB,X,DISPLACEMENT/AXLAB,Y,F/GRID,1XVAR,3PLVAR,4 !绘制节点2位移和节点1的竖向支反力关系FINI通用后处理中可得到最后一个荷载步时节点1 和节点3受到的水平方向支座反力分别为-4759.0N和4759.0N，双杆均受拉。
8.13.ansys非线性分析实例(GUI操作方法)-推荐下载
8.13.非线性分析实例（GUI操作方法）这个实例运行的是在静载和循环点载荷的情况下，对弹塑性圆板的非线性分析。
你可以自定义一条塑性随动曲线和载荷步的相关选项，包括载荷步数的最大值和最小值，以及施加的外部载荷值。
在这个过程中，你可以学习到如何去解读，程序再写入非线性分析过程中产生的监控文件。
该程序使用增量求解过程来得到非线性分析的解，在这个例子中，外部总载荷的施加，是通过载荷步中的载荷子步数依次增加来实现的。
该过程采用牛顿---拉普斯迭代过程来求解每一个子步。
过程中，你必须为每个载荷步指定载荷子步数，因为载荷子步数，是用来控制应用于每个载荷步中第一个子步初始载荷增量大小的。
此外，该程序可以在一个载荷步中，为每一个子步自动决定载荷增量的大小。
当然，你可以指定载荷步的最大值和最小值，来控制这些子步中载荷增量的大小。
如果你定义了载荷子步数，这些子步数的最大号和最小号都是一样的。
而且在载荷步中，程序会用一个恒定的值来作为每个子步的载荷增量。
1 问题描述用平面4节点182单元来建立圆板的轴对称模型，并且设置它的轴对称选项来为模型划分网格。
选择几何分线性分析。
并且制定如下的运动约束：固定住圆盘中心节点，使它的径向位移为0。
使位移圆盘外边缘的节点具有零径向位移和零轴向位移。
在第一个载荷步中施加静载，在随后的6个载荷步中施加循环点载荷。
请看问题的描述。
为第一个载荷步指定十个载荷子步，以保证施加在第一个子步的静载增量为总载荷0.125 N/m2的十分之一。
同样，还要指定载荷子步数的最大值为50，最小值为5，以确保，如果圆板在求解过程中出现严重的非线性行为，那么载荷的增量就会减小到总载荷的1/50。
如果圆板的非线性行为一般，那么载荷的增量就可以提高到总载荷的1/5。
对于接下来的6个载荷步，都施加循环载荷，都运用4个载荷子步，设置子步数的最大值为25，最小值为2。
显示在整个求解过程中，施加循环载荷位置的节点，在垂直方向上位移，以及位于底部，固定边缘节点的反作用力。
ANSYS非线性分析：4-非线性分析方法
第四章非线性有限元方程的解法结构分析问题转化为代数方程组，线性静力问题化为线性代数方程组，非线性静力问题化为非线性方程组。
线性代数方程组的解法有高斯消去法、三角分解法、非线性问题多种多样，但计算方法大同小异，无论材料非线性问题还是几何非线性问题，经过离散后，都归结为解一个非线性方程组。
本章以截面非线性分析为例，说明如何求解非线性方程问题。
对于应力-应变关系为线性关系的问题，截面（单元）刚度是常量。
当混凝土、钢筋材料的应Dδ。
力-应变关系为非线性时，截面（单元）刚度矩阵不是常数，而与截面应变平面值有关，记为()δδ-=。
求解非线性问题的方法可分为3类：此时，截面平衡方程是非线性方程组：[]{}{}()0D P增量法（显式求解）、迭代法（隐式求解法或全量迭代法）、混合法（增量迭代法）。
§4.1 非线性方程组求解的增量法基本思路：分段线性化，将荷载分成很多小步，逐步施加。
增量法也称为显式求解法。
增量法将荷载分成若干增量，每次施加一个荷载增量；假设每一个荷载增量段内（截面或结构）刚度矩阵是常量（线性的）；在不同荷载增量段内（截面或结构）刚度可以变化，与当时应力-应变关系（或位移状态）相对应。
增量法实质上是用一系列线性解去逼近非线性问题，即用分段线性折线替代非线性曲线。
增量法把荷载划分成许多荷载增量，增量的值可以相等，也可以不等。
具体操作方法：压弯构件截面平衡方程的增量矩阵表达式，110000012200311AA A S S I A S d d d d C 2C S J J I S J d d d d A A n nsi si i i i s nnsi isi i i i y N E M yy εφεφεεεεφεφφφφ====⎡⎤⎢⎥++⎡⎤⎡⎤⎧⎫⎧⎫⎧⎫⎧⎫++=⎢⎥⎨⎬⎨⎬⎨⎬⎨⎬⎢⎥⎢⎥++⎣⎦⎩⎭⎩⎭⎩⎭⎩⎭⎣⎦⎢⎥⎢⎥⎣⎦∑∑∑∑或[]{}{}()d d t D P δδ=或 011122122d d d d t t y y t t N dd M d d εφ⎧⎫⎧⎫⎡⎤=⎨⎬⎨⎬⎢⎥⎣⎦⎩⎭⎩⎭ 式中，{}[]T0d d d δεφ=——截面增量应变平面；{}[]Td d d P N M =——截面力增量；[]()t D δ—刚度矩阵，弹性结构=常量，非线性问题是变量，随截面应变平面的变化而变化。
8.6ANSYS非线性静力分析步骤帮助学习
8.6. Performing a Nonlinear Static AnalysisThe procedure for performing a nonlinear static analysis consists of these tasks:∙Build the Model∙Set Solution Controls∙Set Additional Solution Options∙Apply the Loads∙Solve the Analysis∙Review the Results∙Terminating a Running Job; Restarting8.6.1. Build the ModelThis step is essentially the same for both linear and nonlinear analyses, although a nonlinear analysis might include special elements or nonlinear material properties. See Using Nonlinear (Changing-Status) Elements, and Modeling Material Nonlinearities, for more details. If your analysis includes large-strain effects, your stress-strain data must be expressed in terms of true stress and true (or logarithmic) strain. For more information on building models in ANSYS, see the Modeling and Meshing Guide.After you have created a model in ANSYS, you set solution controls (analysis type, analysis options, load step options, and so on), apply loads, and solve. A nonlinear solution will differ from a linear solution in that it often requires multiple load increments, and always requires equilibrium iterations. The general procedure for performing these tasks follows. See Sample Nonlinear Analysis (GUI Method)for a sample problem that walks you through a specific nonlinear analysis.8.6.2. Set Solution ControlsSetting solution controls for a nonlinear analysis involves the same options and method of access (the Solution Controls dialog box) as those used for a linear structural static analysis. For a nonlinear analysis, the default settings in the Solution Controls dialog box are essentially the same settings employed by the automatic solution control method described in Running a Nonlinear Analysis in ANSYS. See the following sections in Structural Static Analysis, with exceptions noted:∙Set Solution Controls∙Access the Solution Controls Dialog Box∙Using the Basic Tab∙The Transient Tab∙Using the Sol'n Options Tab∙Using the Nonlinear Tab∙Using the Advanced NL Tab8.6.2.1. Using the Basic Tab: Special ConsiderationsSpecial considerations for setting these options in a nonlinear structural static analysis include:∙When setting ANTYPE and NLGEOM, choose Large Displacement Static if you are performing a new analysis. (But, keep in mind that not all nonlinear analyses will produce large deformations. See Using Geometric Nonlinearities for further discussion of largedeformations.) Choose Restart Current Analysis if you want torestart a failed nonlinear analysis. You cannot change this setting after the first load step (that is, after you issue your first SOLVEcommand). You will usually choose to do a new analysis, rather thana restart. Restarts are discussed in the Basic Analysis Guide.∙When working with time settings, remember that these options can be changed at any load step. See "Loading" in the Basic Analysis Guide for more information on these options. Advancedtime/frequency options, in addition to those available on theSolution Controls dialog box, are discussed in Advanced Load Step Options You Can Set on the Solution Controls Dialog Box.A nonlinear analysis requires multiple substeps (or time steps; thetwo terms are equivalent) within each load step so that ANSYS can apply the specified loads gradually and obtain an accurate solution.The NSUBST and DELTIM commands both achieve the same effect(establishing a load step's starting, minimum, and maximum stepsize), but by reciprocal means. NSUBST defines the number ofsubsteps to be taken within a load step, whereas DELTIM defines the time step size explicitly. If automatic time stepping is off[AUTOTS], then the starting substep size is used throughout the load step.∙OUTRES controls the data on the results file (Jobname.RST). By default, only the last substep is written to the results file ina nonlinear analysis.Only 1000 results sets (substeps) can be written to the results file, but you can use the command /CONFIG,NRES to increase the limit (see the Basic Analysis Guide).8.6.2.2. Advanced Analysis Options分析选项You Can Set on the Solution Controls Dialog BoxThe following sections provide more detail about some of the advanced analysis options that you can set on the Solution Controls dialog box.8.6.2.2.1. Equation SolverANSYS' automatic solution control activates the sparse direct solver (EQSLV,SPARSE) for most cases. Other options include the PCG and ICCG solvers. For applications using solid elements (for example, SOLID92 or SOLID45), the PCG solver may be faster, especially for 3-D modeling.If using the PCG solver, you may be able to reduce memory usage via the MSAVE command. The MSAVE command triggers an element-by-element approach for the parts of the model that use SOLID45, SOLID92, SOLID95, SOLID185, SOLID186, SOLID187SOLID272, SOLID273, and/or SOLID285 elements with linear material properties. (MSAVE does not support the layered option of the SOLID185 and SOLID186 elements.) To use MSAVE, you must be performing a static or a modal analysis with PCG Lanczos enabled. When using SOLID185, SOLID186, and/or SOLID187, only small strain (NLGEOM,OFF) analyses are allowed. Other parts of the model that do not meet the above criteria are solved using global assembly for the stiffness matrix. MSAVE,ON can result in a memory savings of up to 70 percent for the part of the model that meets the criteria, although the solution time may increase depending on the capabilities of your computer and the element options selected.The sparse direct solver, in sharp contrast to the iterative solvers included in ANSYS, is a robust solver. Although the PCG solver can solve indefinite matrix equations, when the PCG solver encounters anill-conditioned matrix, the solver will iterate to the specified number of iterations and stop if it fails to converge. When this happens, it triggers bisection. After completing the bisection, the solver continues the solution if the resulting matrix is well-conditioned. Eventually, the entire nonlinear load step can be solved.Use the following guidelines for selecting either the sparse or the PCG solver for nonlinear structural analysis:∙If it is a beam/shell or beam/shell and solid structure, choose the sparse direct solver.∙If it is a 3-D solid structure and the number of DOF is relatively large (that is, 200,000 or more DOF), choose the PCG solver.∙If the problem is ill-conditioned (triggered by poor element shapes), or has a big difference in material properties in different regions of the model, or has insufficient displacement boundaryconstraints, choose the sparse direct solver.8.6.2.3. Advanced Load Step Options载荷步选项 You Can Set on the Solution Controls Dialog BoxThe following sections provide more detail about some of the advanced load step options that you can set on the Solution Controls dialog box.8.6.2.3.1. Automatic Time SteppingANSYS' automatic solution control turns automatic time stepping on [AUTOTS,ON]. An internal auto-time step scheme ensures that the time step variation is neither too aggressive (resulting in many bisection/cutbacks) nor too conservative (time step size is too small). At the end of a time step, the size of the next time step is predicted based on four factors:∙Number of equilibrium iterations used in the last time step (more iterations cause the time step size to be reduced) ∙Predictions for nonlinear element status change (time step sizes are decreased when a status change is imminent)∙Size of the plastic strain increment∙Size of the creep strain increment8.6.2.3.2. Convergence CriteriaThe program will continue to do equilibrium iterations until the convergence criteria [CNVTOL] are satisfied (or until the maximum number of equilibrium equations is reached [NEQIT]). You can define custom criteria if the default settings are not suitable.ANSYS' automatic solution control uses L2-norm of force (and moment) tolerance (TOLER) equal to 0.5%, a setting that is appropriate for most cases. In most cases, an L2-norm check on displacement with TOLER equal to 5% is also used in addition to the force norm check. The check that the displacements are loosely set serves as a double-check on convergence.By default, the program will check for force (and, when rotational degrees of freedom are active, moment) convergence by comparing the square rootsum of the squares (SRSS) of the force imbalances against the product of VALUE*TOLER. The default value of VALUE is the SRSS of the applied loads (or, for applied displacements, of the Newton-Raphson restoring forces), or MINREF (which defaults to 0.01), whichever is greater. The default value of TOLER is 0.005. If SOLCONTROL,OFF, TOLER defaults to 0.001 and MINREF defaults to 1.0 for force convergence.You should almost always use force convergence checking. You can also add displacement (and, when applicable, rotation) convergence checking. For displacements, the program bases convergence checking on the change in deflections (Δu) between the current (i) and the previous (i-1)iterations: Δu=ui -ui-1.Note: If you explicitly define any custom convergence criteria [CNVTOL], the entire default criteria will be overwritten. Thus, if you define displacement convergence checking, you will have to redefine force convergence checking. (Use multiple CNVTOL commands to definemultiple convergence criteria.)Using tighter convergence criteria will improve the accuracy of your results, but at the cost of more equilibrium iterations. If you want to tighten (or loosen, which is not recommended) your criteria, you should change TOLER by one or two orders of magnitude. In general, you should continue to use the default value of VALUE; that is, change the convergence criteria by adjusting TOLER, not VALUE. You should make certain that the default value of MINREF= 0.001 makes sense in the context of your analysis. If your analysis uses certain sets of units or has very low load levels, you might want to specify a smaller value for MINREF.Also, we do not recommend putting two or more disjointed structures into one model for a nonlinear analysis because the convergence check tries to relate these disjointed structures, often producing some unwanted residual force.Checking Convergence in a Single and Multi-DOF SystemTo check convergence in a single degree of freedom (DOF) system, you compute the force (and moment) imbalance for the one DOF, and compare this value against the established convergence criteria (VALUE*TOLER). (You can also perform a similar check for displacement (and rotation) convergence for your single DOF.) However, in a multi-DOF system, you might want to use a different method of comparison.The ANSYS program provides three different vector norms to use for convergence checking:∙The infinite norm repeats the single-DOF check at each DOF in your model.∙The L1 norm compares the convergence criterion against the sum of the absolute values of force (and moment) imbalance for all DOFs.∙The L2 norm performs the convergence check using the square root sum of the squares of the force (and moment) imbalances for all DOFs.(Of course, additional L1 or L2 checking can be performed for adisplacement convergence check.)ExampleFor the following example, the substep will be considered to be converged if the out-of-balance force (checked at each DOF separately) is less than or equal to 5000*0.0005 (that is, 2.5), and if the change in displacements (checked as the square root sum of the squares) is less than or equal to 10*0.001 (that is, 0.01).CNVTOL,F,5000,0.0005,0CNVTOL,U,10,0.001,28.6.2.3.3. Maximum Number of Equilibrium IterationsANSYS' automatic solution control sets the value of NEQIT to between 15 and 26 iterations, depending upon the physics of the problem. The idea is to employ a small time step with fewer quadratically converging iterations.This option limits the maximum number of equilibrium iterations to be performed at each substep (default = 25 if solution control is off). If the convergence criteria have not been satisfied within this number of equilibrium iterations, and if auto time stepping is on [AUTOTS], the analysis will attempt to bisect. If bisection is not possible, then the analysis will either terminate or move on to the next load step, according to the instructions you issue in the NCNV command.8.6.2.3.4. Predictor-Corrector OptionANSYS' automatic solution control will set PRED,ON if there are no SOLID65 elements present. If the time step size is reduced greatly in the current substep, PRED is turned off. For transient analysis, the predictor is also turned off.You can activate a predictor on the DOF solution for the first equilibrium iteration of each substep. This feature accelerates convergence and is particularly useful if nonlinear response is relatively smooth, as in the case of ramped loads.8.6.2.3.5. VT AcceleratorThis option selects an advanced predictor-corrector algorithm based on Variational Technology to reduce the overall number of iterations [STAOPT,VT for static analyses, TRNOPT,VT for transient]. This option requires an HPC license. It is applicable to analyses that include large deflection [NLGEOM], hyperelasticity, viscoelasticity, and creep nonlinearities. Rate-independent plasticity and nonlinear contact analyses may not show any improvement in convergence rates; however, you may choose this option with these nonlinearities if you wish to rerun the analysis with changes to the input parameters later.8.6.2.3.6. Line Search OptionANSYS' automatic solution control will toggle line search on and off as needed. For most contact problems, LNSRCH is toggled on. For mostnon-contact problems, LNSRCH is toggled off.This convergence-enhancement tool multiplies the calculated displacement increment by a program-calculated scale factor (having a value between 0 and 1), whenever a stiffening response is detected. Because the line search algorithm is intended to be an alternative to the adaptive descent option [NROPT], adaptive descent is not automatically activated if the line search option is on. We do not recommend activating both line search and adaptive descent simultaneously.When an imposed displacement exists, a run cannot converge until at least one of the iterations has a line search value of 1. ANSYS scales the entire ΔU vector, including the imposed displacement value; otherwise, a "small" displacement would occur everywhere except at the imposed DOF. Until one of the iterations has a line search value of 1, ANSYS does not impose the full value of the displacement.8.6.2.3.7. Cutback CriteriaFor finer control over bisections and cutback in time step size, use [CUTCONTROL, Lab, VALUE, Option]. By default, for Lab= PLSLIMIT (maximum plastic strain increment limit), VALUE is set to 15%. This field is set to such a large value for avoiding unnecessary bisections caused by high plastic strain due to a local singularity which is not normally of interestto the user. For explicit creep (Option= 0), Lab= CRPLIM (creep increment limit) and VALUE is set to 10%. This is a reasonable limit for creep analysis. For implicit creep (Option = 1), there is no maximum creep criteria by default. You can however, specify any creep ratio control. The number of points per cycle for second order dynamic equations (Lab = NPOINT) is set to VALUE = 13 by default to gain efficiency at little cost to accuracy.8.6.3. Set Additional Solution OptionsThis section discusses additional options that you can set for the solution. These options do not appear on the Solution Controls dialog box because they are used infrequently, and their default settings rarely need to be changed. ANSYS menu paths are provided in this section to help you access these options for those cases in which you choose to override the ANSYS-assigned defaults.8.6.3.1. Advanced Analysis Options You Cannot Set on the Solution Controls Dialog BoxThe following sections describe some advanced analysis options that you can set for your analysis. As noted above in Set Additional Solution Options, you cannot use the Solution Controls dialog box to set the options described below. Instead, you must set them using the standard set of ANSYS solution commands and the standard corresponding menu paths.8.6.3.1.1. Stress StiffnessTo account for buckling, bifurcation behavior, ANSYS includes stress stiffness in all geometrically nonlinear analyses. If you are confident of ignoring such effects, you can turn stress stiffening off (SSTIF,OFF). This command has no effect when used with several ANSYS elements; see the Element Reference for the description of the specific elements you are using.Command(s):SSTIFGUI: Main Menu> Solution> Unabridged Menu> Analysis Type> Analysis Options 8.6.3.1.2. Newton-Raphson OptionANSYS' automatic solution control will use the FULL Newton-Raphson option with adaptive descent off if there is a nonlinearity present. However, when node-to-node, node-to-surface contact elements are used for contactanalysis with friction, then adaptive descent is automatically turned on (for example, PIPE20, BEAM23, BEAM24, and PIPE60). The underlying contact elements require adaptive descent for convergence.Command(s):NROPTGUI: Main Menu> Solution> Unabridged Menu> Analysis Type> Analysis Options Use this option only in a nonlinear analysis.This option specifies how often the tangent matrix is updated during solution.If you choose to override the default, you can specify one of these values: ∙Program-chosen (NROPT,AUTO): The program chooses which of the options to use, based on the kinds of nonlinearities present in your model. Adaptive descent will be automatically activated, whenappropriate.∙Full (NROPT,FULL): The program uses the full Newton-Raphson procedure, in which the stiffness matrix is updated at everyequilibrium iteration.If adaptive descent is on (optional), the program will use thetangent stiffness matrix only as long as the iterations remainstable (that is, as long as the residual decreases, and no negative main diagonal pivot occurs). If divergent trends are detected on an iteration, the program discards the divergent iteration andrestarts the solution, using a weighted combination of the secant and tangent stiffness matrices. When the iterations return to aconvergent pattern, the program will resume using the tangentstiffness matrix. Activating adaptive descent will usually enhance the program's ability to obtain converged solutions for complicated nonlinear problems but is supported only for elements indicatedunder "Special Features" in the Input Summary table (Table 4.n.1 for an element, where n is the element number) in the ElementReference.∙Modified (NROPT,MODI): The program uses the modifiedNewton-Raphson technique, in which the tangent stiffness matrix is updated at each substep. The matrix is not changed duringequilibrium iterations at a substep. This option is not applicable to large deformation analyses. Adaptive descent is not available.∙Initial Stiffness (NROPT,INIT): The program uses the initial stiffness matrix in every equilibrium iteration. This option can be less likely to diverge than the full option, but it often requiresmore iterations to achieve convergence. It is not applicable tolarge deformation analyses. Adaptive descent is not available.∙Full with unsymmetric matrix (NROPT,UNSYM): The program uses the full Newton-Raphson procedure, in which the stiffness matrix isupdated at every equilibrium iteration. In addition, it generates and uses unsymmetric matrices that you can use for any of thefollowing:o If you are running a pressure-driven collapse analysis, an unsymmetric pressure load stiffness might be helpful inobtaining convergence. You can include pressure loadstiffness using SOLCONTROL,INCP.o If you are defining an unsymmetric material model using TB,USER, you would need NROPT,UNSYM to fully use the propertyyou defined.o If you are running a contact analysis, an unsymmetric contact stiffness matrix would fully couple the sliding and thenormal stiffnesses. See Determining Contact Stiffness andAllowable Penetration in the Contact Technology Guide fordetails.You should first try NROPT,FULL; then try NROPT,UNSYM if youexperience convergence difficulties. Note that using anunsymmetric solver requires more computer time to obtain a solution, than if you use a symmetric solver.∙If a multistatus element is in the model, however, it would be updated at the iteration in which it changes status, irrespective of the Newton-Raphson option.8.6.3.2. Advanced Load Step Options You Cannot Set on the Solution Controls Dialog BoxThe following sections describe some advanced load step options that you can set for your analysis. As noted above in Set Additional Solution Options, you cannot use the Solution Controls dialog box to set the options described below. Instead, you must set them using the standard set of ANSYS solution commands and the standard corresponding menu paths.8.6.3.2.1. Creep CriteriaIf your structure exhibits creep behavior, you can specify a creep criterion for automatic time step adjustment [CRPLIM,CRCR, Option]. (If automatic time stepping [AUTOTS] is off, this creep criterion will have no effect.) The program will compute the ratio of creep strain increment , the change in creep strain in the last time step) to the elastic (Δεcrstrain (εel), for all elements. If the maximum ratio is greater than the criterion CRCR, the program will then decrease the next time step size; if it is less, the program might increase the next time step size. (The program will also base automatic time stepping on the number of equilibrium iterations, impending element status change, and plastic strain increment. The time step size will be adjusted to the minimum size calculated for any of these items.) For explicit creep (Option = 0), ifthe ratio Δεcr / εelis above the stability limit of 0.25, and if thetime increment cannot be decreased, a divergent solution is possible and the analysis will be terminated with an error message. This problem can be avoided by making the minimum time step size sufficiently small [DELTIM and NSUBST]. For implicit creep (Option = 1), there is no maximum creep limit by default. You can however, specify any creep ratio control.Command(s):CRPLIMGUI: Main Menu> Solution> Unabridged Menu> Load Step Opts> Nonlinear> Creep CriterionNote: If you do not want to include the effects of creep in your analysis, use the RATE command with Option = OFF, or set the time steps to be longer than the previous time step, but not more than 1.0e-6 longer.8.6.3.2.2. Time Step Open ControlThis option is available for thermal analysis. (Remember that you cannot perform a thermal analysis using the Solution Controls dialog box; you must use the standard set of ANSYS solution commands or the standard corresponding menu paths instead.) This option's primary use is in unsteady state thermal analysis where the final temperature stage reaches a steady state. In such cases, the time step can be opened quickly. The default is that if the TEMP increment is smaller than 0.1 in three (NUMSTEP = 3) contiguous substeps, the time step size can be "opened-up" (value = 0.1 by default). The time step size can then be opened continuously for greater solution efficiency.Command(s):OPNCONTROLGUI: Main Menu> Solution> Unabridged Menu> Load Step Opts> Nonlinear> Open Control8.6.3.2.3. Solution MonitoringThis option provides a facility to monitor a solution value at a specified node in a specified DOF. The command also provides a means to quickly review the solution convergence efficiency, rather than attempting to gather this information from a lengthy output file. For instance, if an excessive number of attempts were made for a substep, the information contained in the file provides hints to either reduce the initial time step size or increase the minimum number of substeps allowed through the NSUBST command to avoid an excessive number of bisections.Command(s):MONITORGUI: Main Menu> Solution> Unabridged Menu> Load Step Opts> Nonlinear> MonitorAdditionally, the NLHIST command allows you to monitor results of interest in real time during solution. Before starting the solution, you can request nodal data such as displacements or reaction forces at specific nodes. You can also request element nodal data such as stresses and strains at specific elements to be graphed. Pair-based contact data are also available. The result data are written to a file named Jobname.nlh.For example, a reaction force-deflection curve could indicate when possible buckling behavior occurs. Nodal results and contact results are monitored at every converged substep while element nodal data are written as specified via the OUTRES setting.You can also track results during batch runs. To execute, either access the ANSYS Launcher and select File Tracking from the Tools menu, or type nlhist120in the command line. Use the supplied file browser to navigate to your Jobname.nlh file, and select it to invoke the tracking utilty. You can use this utilty to read the file at any time, even after the solution is complete.Command(s):NLHISTGUI: Main Menu> Solution> Results TrackingNote: Results tracking is not available with FLOTRAN analyses.8.6.3.2.4. Birth and DeathSpecify birth and death options as necessary. You can deactivate [EKILL] and reactivate [EALIVE] selected elements to model the removal or addition of material in your structure. As an alternative to the standard birthand death method, you can change the material properties for selected elements [MPCHG] between load steps.Command(s): EKILL,EALIVEGUI: Main Menu> Solution> Load Step Opts> Other> Birth & Death> Kill ElementsMain Menu> Solution> Load Step Opts> Other> Birth & Death> Activate ElemThe program "deactivates" an element by multiplying its stiffness by a very small number (which is set by the ESTIF command), and by removing its mass from the overall mass matrix. Element loads (pressure, heat flux, thermal strains, and so on) for inactive elements are also set to zero. You need to define all possible elements during preprocessing; you cannot create new elements in SOLUTION.Those elements to be "born" in later stages of your analysis should be deactivated before the first load step, and then reactivated at the beginning of the appropriate load step. When elements are reactivated, they have a zero strain state, and (if NLGEOM,ON) their geometric configuration (length, area, and so on) is updated to match the current displaced positions of their nodes. See the Advanced Analysis Techniques Guide for more information on birth and death.Another way to affect element behavior during solution is to change the material property reference number for selected elements:Command(s):MPCHGGUI: Main Menu> Solution> Load Step Opts> Other> Change Mat Props> Change Mat NumNote: Use MPCHG with caution. Changing material properties in a nonlinear analysis may produce unintended results, particularly if you change nonlinear [TB] material properties.8.6.3.2.5. Output ControlIn addition to OUTRES, which you can set on the Solution Controls dialog box, there are several other output control options that you can set for an analysis:。
基于ANSYS软件的结构非线性有限元分析及应用实例
基于ANSYS软件的结构非线性有限元分析及应用实例郝艳娥;兰永强【摘要】This article briefly introduces ANSYS software to analyze the structural problems of the basic processes and procedures elaborated nonlinear finite element analysis and geometric nonlinear structural material based on ANSYS software. And the application of ANSYS software to the nonlinear behavior of a structure instance is simulated and analyzed.%文章简要介绍ANSYS软件分析结构问题的基本流程与步骤，详细阐述了基于ANSYS软件的结构材料非线性和几何非线性有限元分析方法。
并应用ANSYS软件对一结构实例的非线性行为进行了模拟和分析。
【期刊名称】《电子测试》【年(卷),期】2014(000)021【总页数】2页(P166-167)【关键词】ANSYS软件;有限元;材料非线性【作者】郝艳娥;兰永强【作者单位】延安大学，延安，716000;延安大学，延安，716000【正文语种】中文ANSYS有限元软件界面友好、功能强大、方便实用，已广泛应用于土木、流体、热、电磁、声学等各种领域。
利用ANSYS软件对结构的受力变形进行仿真分析，不仅能大致预测结构的危险区域和破坏情况，及时采取相应预防措施，提高工作效率，而且能达到与试验互相验证、有效补充的目的。
虽然ANSYS软件应用在不同的工程领域里，相应的分析方法和步骤略有不同，但大多数分析的基本过程是：（1）单元类型的设定。
ANSYS单元库中具有一百五十多种以上不同的单元类型，在建模之前必须先设定单元类型以模拟工程中各种结构和材料，单元类型决定了单元位于二维空间还是三维空间和的单元自由度数。
非线性2【ANSYS非线性分析】
1几何非线性分析随着位移增长，一个有限单元已移动的坐标可以以多种方式改变结构的刚度。
一般来说这类问题总是是非线性的，需要进行迭代获得一个有效的解。
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变。
首先，如果这个单元的形状改变，它的单元刚度将改变。
（看图2─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。
（看图2─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，大应变分析说明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1─11 大应变和大转动大应变处理对一个单元经历的总旋度或应变没有理论限制。
（某些ANSYS单元类型将受2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，这可以〔NSUBST ，DELTIM ，AUTOTS 〕，通过GUI 路径 Main Menu>Solution>Time/Prequent)。
无论何时当系统是非保守系统，来自动实现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。
ANSYS非线性分析：非线性2
几何非线性分析随着位移增长，一个有限单元已移动的坐标可以以多种方式改变结构的刚度。
一般来说这类问题总是是非线性的，需要进行迭代获得一个有效的解。
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变。
首先，如果这个单元的形状改变，它的单元刚度将改变。
（看图2─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。
（看图2─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，大应变分析说明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。
1图1─11 大应变和大转动大应变处理对一个单元经历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，这可以〔NSUBST，DELTIM，AUTOTS〕，通过GUI路径Main Menu>Solution>Time/Prequent)。
无论何时当系统是非保守系统，来自动实现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。
【ANSYS非线性分析】6-非线性分析应用
两曲线在下降段区间差别较大的原因在于，EC2规范建议的应力-应变关系中，当应变小于-0.0034时应力突降为零,因此截面刚度迅速降低。CEB规范建议的应力-应变关系随应变而逐渐的降低，截面刚度降低的也比较缓慢。
图6.1-4CEB规范与EC2规范建议的应力-应变关系截面分析结果比较
图6.1-5DIN 1045规范建议的应力-应变关系
图6.1-6钢筋混凝土柱截面
图6.1-7极限状态时混凝土压应力分布
图6.1-8弯矩-曲率(My-y)关系曲线
§6.2
6.2.1简化计算
利用虚功原理计算荷载挠度曲线：设两点集中加载简支梁，弯矩图、曲率分布图如下，
图6-2-1梁内力与变形
取支撑条件相同的简支梁为虚梁，拟求跨中挠度，在虚梁跨中施加单位荷载（求转角加单位力矩）。虚梁在单位力作用下的弯矩为，
三个高斯点计算的极限荷载值为Pmax= 0.045957 MN，相应的跨中挠度为wpmax= 0.016184.五个高斯点计算的极限荷载值为Pmax= 0.046073 MN，相应的跨中挠度为wpmax= 0.016568.相对极限荷载误差为0.23%以及跨中挠度is 2.32%.
由图6.2-6和图6.1-7，发现三个高斯点与五个高斯点的细微差别，在曲线峰值点处，三个高斯点有锋利的转折，而五个高斯点无此特征。图6.2-8为两曲线比较。.本例仅为材料非线性分析，如果同时考虑几何非线性分析，建议单元积分时最好取五个高斯点。
例4:单元—平面四节点等参元，整体式单元模式；分析方法—割线刚度法
图6-2-16钢筋混凝土简支梁
图6-2-17钢筋、混凝土应力-应变曲线
图6-2-18钢筋混凝土简支梁单元划分
图6-2-19荷载-挠度曲线
ANSYS-几何非线性分析实例
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ansys学习－非线性静态分析实例问题描述一个子弹以给定的速度射向壁面。
壁面假定是刚性的和无摩擦的。
将研究子弹和壁面接触后达80微秒长的现象。
目的是确定子弹的整个变形，速度历程，以及最大等效Von Mises应变。
求解使用SI单位。
用轴对称单元模拟棒。
求解最好能通过单一载荷步实现。
在这个载荷步中，将同时施加初始速度和约束。
将圆柱体末端的节点Y方向约束住以模拟一固壁面。
打开自动时间分步来允许ANSYS确定时间步长。
定义分析结束的时间为8E-5秒，以确保有足够长的时间来扑捉整个变形过程。
问题详细说明下列材料性质应用于这个问题：EX= (杨氏模量）DENS= （密度）NUXY=（泊松比）Yield Strength=（屈服强度）Tangent Modulus （剪切模量）下列尺寸应用于这个问题：长=-3m直径=-3m对于这个问题的初始速度是。
图1铜圆柱体图解求解步骤：步骤一：设置分析标题1、选择菜单路径：Utility Menn>File>ChangeTitle。
2、键入文字“Coppery Cylinder Impacting a Rigid Wall”3、单击OK。
步骤二：定义单元类型1、选择菜单路径Mail Menu>Preprocessor>Element Type>All/Edit/Delete。
2、单击Add。
Library of Element Types(单元类型库）对话框出现。
3、在靠近左边的列表中，单击“Visio Solid”仅一次。
4、选靠近右边的列表中，单击“4node Plas 106”仅一次。
5、单击OK。
Library of Element Types 对话框关闭。
6、单击Options (选项）。
VISCO106 element type Options(visco106单元类型选项）对话框出现。
7、在关于element behavior（单元特性）的卷动柜中，卷动到“Axisymmetric” 且选中它。
8、单击OK。
9、单击Element Types (单元类型）对话框中的Close。
步骤三：定义材料性质1、选择菜单路径Main Menu>Preprocessor>Material Props>-Constant-Isotropic. Isotropic Matersal Properties (各向同性材料性质）对话框出现。
2、单击OK来指定材料号为1。
另一个I sotropic Material Properties对话框出现。
3、对杨氏模量（EX）键入4、对密度（DENS）键入8930。
5、对泊松比（NUXY）键入。
6、单击OK。
步骤四：定义双线性各向同性强化数据表（BISO）1、选择菜单路径Main Menu>Preprocessor>Matersal Props>Data Tables> Define/Activate .Define/Activate Data Table(定义数据表）对话柜出现。
2、在关于type of data table(数据表类型）的卷动框中，卷动到“Bilin isotr BISO”且选中它。
3、对material reference number(材料参考号）健入1。
4、对number of temperatures(温度数）键入1和单击OK。
5、选择菜单路径Main Menu>Preprocessor>Material Props>Data Tables>Edit Active. Data Table BISO 对话框出现。
6、对YLD Strs(屈服应力）键入。
7、对 Tang Mod(剪切模量）键入。
8、选择File>Apply & Quit。
9、选择菜单路径Main Menu>Preprosessor>Material Porps>Data Tables>Graph. Graph Data Tables(图形表示数据表）对话框出现。
10、单击OK接受绘制BISO表的缺省。
一个BISO表的标绘图出现在ANSYS图形窗口中。
11、在ANSYS TooLbar上单击SAVE_DB。
步骤五、产生矩形在这一步中，你产生一个代表柱体半横截面积的矩形。
1、选择菜单路径Main Menu>Preprocessor>-Modeling-Create>-Area-Rectangle>By Dimensions. Create Rectanyle by Dimensions(依据尺寸产生矩形）对话框出现。
2、对X_坐标键入0，.0032。
3、对Y_坐标键入0，.0324然后单击OK。
一个矩形出现在ANSYS图形窗口中。
4、选择菜单路径Utility Menu>Plot>lines.步骤六：设置单元尺寸1、选择菜单路径Main Menu>Preprocessor>-Meshing-Shape&Size>-Lines-Picked Lines. Element Size On Picked Lines(关于挑选出的线的单元尺寸）选择菜单出现。
2、在长线中的一条上单击一次然后单击OK。
Element Sizes on Picked Lines 对话框出现。
3、对number of element divisions（单元划分的数目）键入20然后单击OK。
4、重复步骤1和2，次选择短线中的一条。
但这5、对number of element divisions键入4然后单击OK。
步骤七：设置网格单元形状且对矩形划分网格1、选择菜单路径Main Menu>Preprocessor>-Mesh Tool2、选择“quad”和“Map”，然后单击“Mesh”3、在拾取菜单出现后，选择面，然后单击“OK”4、在ANSYS Toolbar上单击SAVE_DB。
5、选择菜单路径Main Menu>Preprocessor>-Meshing-Mesh>-Area-Mapped>3 or 4 Sided. Mesh Areas(对面积划分网格）选择菜单出现。
6、单击Pick All。
7、单击ANSYS Toolbar上的SAVE_DB。
步骤八：定义分析类型和选项1、选择菜单路径Main Menu>Solution>-Analysis Type-New Analysis.2、单击“Transient”来选中它然后单击OK。
3、选择菜单路径Main Menu>Solution>Analysis Analysis（瞬态过程分析）对话框出现。
4、单击OK接受完全求解方法的缺省。
Full Transient Analysis对话框出现。
5、单击Large deform effects option(大变型效应选项）使之为ON（开）状态然后单击OK。
步骤九：定义弹的初始速度1、选择菜单路径Main Menu>Solution>-Loads-Apply>Initial Condit'n>Define. Define Initial Condition(定义初始条件）选择菜单出现。
2、单击Pick All. Define Initial Conditions 对话框出现。
3、在关于DOF to be Specified(要被指定的DOF）的卷动框中，卷动到“UY”且选中它。
4、对initial velocity(初始速度）键入－227然后单击OK。
5、单击ANSYS Toolbar上的SAVE_DB。
步骤十：施加约束1、选择菜单路径Main Menu>Solution>-Loads-Apply>-Structural-Displacement> On 。
U,ROT on Nodes 选择菜单出现。
2、单击Pick All.， Apply U, ROT on Nodes 对话框出现。
3、对于DOFs to be Constrained (要被约束的DOFs）单击“UY”，然后单击Apply.4、在选择菜单中，单击“BOX”作为选择方法。
5、当你拖鼠标沿X=的结点周围（沿矩形左边的第一个结点集）形成一个矩形柜时要按下且保持鼠标左键。
6、单击Apply.7、在对话框中，对于DOFs to be constrained单击“UX”。
你需要单击“UY”一次以去除它。
8、单击Apply.9、在选择菜单中，单击“BOX”选择方法。
10、当你拖鼠标沿Y=O的结点周围（沿矩形底边的第一个结点集）形成一个矩形框时按下且保鼠标左键。
11、单击OK。
12、在对话框中，单击“UY”来选中它，你需要单击“UX”仅一次来淘汰它。
13、单击OK。
现在在ANSYS图形窗口中位移符号沿矩形的左边和底边产生。
步骤十一：设置载荷步选项1、选择菜单路径Main Menu>Solution>-Load Step Options-Time/Frequenc> time&Time Step. Time&Time Step Option(时间和时间步选项）对话框出现。
2、对time at end of Load Step(载荷步终止时间）键入8e-5。
3、对time step size (时间步长）键入。
4、单击“Stepped”来选中它。
5、单击automatic time stepping option（自动时间分步选项）使之为ON（开）状态然后单击OK。
6、选择菜单路径Main Menu>Solution>-Load Step Options-Output Ctrls> DB/Results File。
Controls for Database and Results File Writing (对数据库和结果文件写入的控制）对话框出现。
7、单击“Every Nth substep”（“每隔N个子步”）且选中它。
8、对于Value of N (N的值）键入4然后单击OK。
9、单击ANSTS Toolbar上的SAVE_DB。
步骤十二：求解问题1、选择菜单路径Main Menu>Solution>-Solve-Current LS。
2、检阅状态窗口中的信息然后单击close。
3、单击Solve Current Load Step(求解当前载荷步）对话框中的OK开始求解。
4、当求解完成时单击close。