有限元分析 三维托架实体受力分析

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《有限元基础理论》报告学院:班级:姓名:学号:任课老师:二〇一一年十二月题目一:三维托架实体受力分析题目:1、三维托架实体受力分析:托架顶面承受50psi的均匀分布载荷。

托架通过有孔的表面固定在墙上,托架是钢制的,弹性模量E=29×106psi,泊松比v=0.3.试通过ANSYS输出其变形图及其托架的von Mises应力分布。

题目1的分析:先进行建模,此建模的难点在对V3的构建(既图中的红色部分)。

要想构建V3,首先应将A15做出来,然后执行Main Menu>Preprocessor>Modeling>Operate>Booleans>Add>Volumes命令,将所有的实体合并为一个整体。

建模后,就对模型进行网格的划分,实行Main Menu>Preprocessor>Meshing>MeshTool,先对网格尺寸进行编辑,选0.1,然后点Meshing,Pick all进行网格划分,所得结果如图1.1。

划分网格后,就可以对模型施加约束并进行加载求解了。

施加约束时要注意,由于三维托架只是通过两个孔进行固定,故施加约束应该只是针对两孔的内表面,执行Main Menu>Solution>Define Loads>Apply>Structrual>Displacement>Symmetry B.C>On Areas命令,然后拾取两孔的内表面,单击OK就行了。

施加约束后,就可以对实体进行加载求解了,载荷是施加在三维托架的最顶上的表面的,加载后求解运算,托架的变形图如图1.2。

图1.1、托架网格图图1.2输出的是原型托架和施加载荷后托架变形图的对比,虚线部分即为托架的原型,从图1.2可看出,由于载荷的作用,托架上面板明显变形了,变形最严重的就是红色部分,这是因为其离托板就远,没有任何物体与其分担载荷,故其较容易变形甚至折断。

这是我们在应用托架的时候应当注意的。

图1.2、托架位移变形图图1.3为托架的应力分布图,由图可看出主要在两孔处出现应力集中,也就是说这些地方所受的应力的最大的,比较容易出现裂痕。

我们在应用托架的时候,应当注意采取一些设施,以便减缓其应力集中。

特别是在施加载荷时,绝对不能够超过托架所能承受的极限,否则必将导致事故的发生。

文后附上建模分析时所执行的命令流。

图1.3、托架应力分布图1.指定分析标题1.选取菜单路径Utility Menu | File | Change Jobname,将弹出Change Jobname (修改文件名)对话框。

2.在Enter new jobname (输入新文件名)文本框中输入文字“bracket”,为本分析实例的数据库文件名。

单击对话框中的“OK”按钮,完成文件名的修改。

3.选取菜单路径Utility Menu | File | Change Title,将弹出Change Title (修改标题)对话框。

4.在Enter new title (输入新标题)文本框中输入文字“press analysis of bracket structure”,为本分析实例的标题名。

单击对话框中的“OK”按钮,完成对标题名的指定。

2.定义单元类型1.选取菜单路径Main Menu | Preprocessor | Element Type | Add/Edit/Delete,将弹出Element Types (单元类型定义)对话框。

单击对话框中的按钮,将弹出Library ofElement Types (单元类型库)对话框。

2.在左边的滚动框中单击“Structural Solid”,选择结构壳单元类型。

在右边的滚动框中单击“Quad 10node 92”,在对话框中单击“OK”按钮,完成对这种单元的定义。

3.指定材料特性1.选取菜单路径Main Menu | Preprocessor | Material Props | Material Models,将弹出Define Material Model Behavior (材料模型定义)对话框。

2.依次双击Structural,Linear ,Elastic 和Isotropic,将弹出1 号材料的弹性模量EX 和泊松比PRXY 的定义对话框。

3.在EX文本框中输入2.9E11,PRXY文本框中输入0.3。

定义材料的弹性模量为2.9E6 N/m2,泊松比为0.3。

单击“OK”按钮,关闭对话框。

4.在Define Material Model Behavior (材料模型定义)对话框中,选取路径Material | Exit,完成对材料模型的定义。

5.单击ANSYS10.0 的ANSYS Toolbar (工具条)上的“SAVE”按钮,保存数据库文件4.建立托架的有限元模型1.选取路径Main Menu | Preprocessor | Modeling | Create | Volume|Block|By Dimensions,将弹出Create Block by Dimensions(根据坐标创建体)对话框。

在对话框输入:X1,X2 X-coordinates:-1,1Y1,Y2 Y-coordinates:-1.5,1.5Z1, Z2 Z-coordinates:0,1/8然后单击“APPL Y”按钮,再次在对话框输入:X1,X2 X-coordinates:-1,1Y1,Y2 Y-coordinates:1.5,1.625Z1, Z2 Z-coordinates:0,32.选取路径Main Menu | Preprocessor | Modeling | Operate |Booleans|Add|Volumes将弹出Add Volumes(体相加)对话框,在对话框单击“PICK ALL”按钮完成体相加操作。

3.在执行显示keypoint的操作之后,执行显示line的操作,选取路径Main Menu | Preprocessor | Modeling | Create |Lines|Lines|StrainghtLine将弹出Create Straight Line对话框,然后选择关键点5、13生成L13直线,单击“OK”按钮完成操作。

4.选取路径Main Menu | Preprocessor | Modeling | Create |Area|Arbitrary|By Lines将弹出对话框Create Area By Lines然后选择直线L1,L9,L13,L20,L24,L25,单击“OK”即可生成面A4。

5.选取路径Main Menu | Preprocessor | Modeling |Operate|Extrude|Areas|Along Normal弹出对话框Extrude Area by…选择面A4单击“OK”按钮,将弹出另一个对话框,在Length extrusion项输入“-1/8”,单击“OK”按钮。

然后再次如前做的将所有体相加的操作。

6.选取路径Main Menu | Preprocessor | Modeling |Create|Areas|Circle|Solid Circle将弹出Solid Circular Area对话框,在WP x,WPy,Radius项分别输入0,-0.5,0.25单击Apply,再次输入0,0.5,0.25然后单击“OK”按钮。

然后选取路径Main Menu | Preprocessor | Modeling|Operate|Extrude|Areas|Along Normal弹出对话框Extrude Area by…选择其中一个圆面单击“Apply”按钮,将弹出另一个对话框,在Length extrusion项输入“1”,单击“OK”按钮。

对另一个圆面做相同操作。

7.选取路径Main Menu | Preprocessor | Modeling | Operate |Booleans|Subtract|Volumes将弹出Subtract Volumes(体相减)对话框,选择两个圆柱体所在的体,单击“Apply”按钮,然后选择两个圆柱体,单击“OK”按钮,完成体相减操作。

5.网格划分1.选取路径Main Menu | Preprocessor | Modeling|Meshing|MeshTool将弹出MeshTool对话框,单击“Mesh”按钮,弹出另一对话框,再次单击“PICK ALL”按钮完成网格划分。

6.施加约束,载荷并求解1.选取菜单路径Main Menu | Preprocessor | Loads | Define Loads | Apply | Structural | Displacement | On Areas,将会弹出拾取对话框,选择两圆孔,单击对话框中的“OK”按钮。

完成施加约束操作。

2.选取菜单路径Main Menu | Solution | Define Loads | Apply | Structural |Pressure |On Areas将会弹出拾取对话框,选择面A10,A19单击“OK”按钮,弹出另一对话框,在Load PRES value 项输入“50”单击“OK”完成施加载荷操作。

3.选取菜单路径Main Menu | Solution |Solve|Current LS弹出Solve Current Load Step对话框,单击“OK”开始求解,求解结束后,关闭相应对话框。

4.选取菜单路径Main Menu |General Postproc|Plot Results|Contour Plot|Nodal Solu将弹出Contour Nodal Solution Data对话框,选择Nodal Solution|DOF Solution|Displacement vector sum 将得到如位移图(1.2):5.选取菜单路径Main Menu |General Postproc|Plot Results|Contour Plot|Nodal Solu将弹出Contour Nodal Solution Data对话框,选择Nodal Solution|Stress|von Mises Stress将得到如应力图(1.3):命令代码/BATCH/COM,ANSYS RELEASE 10.0 UP20050718 22:40:4612/25/2011/input,menust,tm p,'',,,,,,,,,,,,,,,,1/GRA,POWER /GST,ON /PLO,INFO,3/GRO,CURL,ON/CPLANE,1/REPLOT,RESIZEWPSTYLE,,,,,,,,/REPLOT,RESIZE/FILNAME,bracket,0/TITLE,pressanalysis ofbracket structure/PREP7!*ET,1,SOLID92!*!*MPTEMP,,,,,,,,MPTEMP,1,0MPDATA,EX,1,,2.9E11MPDATA,PRXY,1,,0.3SA VEBLOCK,-1,1,-1.5,1.5,0,0.125,BLOCK,-1,1,1.5,1.625,0,3,FLST,2,2,6,ORD E,2FITEM,2,1 FITEM,2,-2V ADD,P51X/PNUM,KP,1/PNUM,LINE,0 /PNUM,AREA,0 /PNUM,VOLU,0 /PNUM,NODE,0 /PNUM,TABN,0 /PNUM,SV AL,0 /NUMBER,0!*/PNUM,ELEM,0 /REPLOT!*/USER, 1/FOC, 1, 0.426937526219,0.284687479101 E-01,1.50000000000 /REPLO/VIEW, 1, -0.68569594035 6 , 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