有限元分析案例

有限元分析案例

图1 钢铸件及其砂模的横截面尺寸

砂模的热物理性能如下表所示:

铸钢的热物理性能如下表所示:

一、初始条件:铸钢的温度为2875o F，砂模的温度为80o F；砂模外边界的对流边界条件：对流系数0.014Btu/hr.in2.o F，空气温度80o F；求3个小时后铸钢及砂模的温度分布。

二、菜单操作:

1.Utility Menu>File>Change Title, 输入Casting Solidification;

2.定义单元类型:Main Menu>Preprocessor>Element Type>Add/Edit/Delete, Add, Quad 4node 55；

3.定义砂模热性能:Main Menu>Preprocessor>Material Props>Isotropic,默认材料编号1, 在Density(DENS)框中输入0.054,在Thermal conductivity (KXX)框中输入0.025,在S pecific heat(C)框中输入0.28;

4.定义铸钢热性能温度表:Main Menu>Preprocessor>Material Props>-Temp Dependent->Temp Table,输入T1=0,T2=2643, T3=2750, T4=2875;

5.定义铸钢热性能:Main Menu>Preprocessor>Material Props>-Temp Dependent ->Prop Table, 选择Th Conductivity,选择KXX, 输入材料编号2,输入C1=1.44, C2=1.54, C3=1.22, C4=1.22,选择Apply,选择Enthalpy,输入C1=0, C2=128.1, C3=163.8, C4=174.2;

6.创建关键点:Main Menu>Preprocessor>-Modeling->Create>Keypoints>In Active

CS,输入关键点编号1,输入坐标0,0,0, 输入关键点编号2,输入坐标22,0,0, 输入关键点编号3,输入坐标10,12,0,输入关键点编号4, 输入坐标0,12,0;

7.创建几何模型:Main Menu>Preprocessor>-Modeling->Create>-Areas-> Arbitrary>Through KPs,顺序选取关键点1,2,3,4;

8.Main Menu>Preprocessor>-Modeling->Create>-Areas->Rectangle>By Dimension,输入X1=4,X2=22,Y1=4,Y2=8;

9.进行布尔操作:Main Menu>Preprocessor>-Modeling->Operate>-Booleans-> Overlap>Area,Pick all；

10.删除多余面:Main Menu>Preprocessor>-Modeling->Delete>Area and Below,3

11.保存数据库:在Ansys Toolbar中选取SA VE_DB;

12.定义单元大小:Main Menu>Preprocessor>-Meshing->Size Cntrls>-Global->Size,在Element edge length框中输入1;

13.对砂模划分网格:Main Menu>Preprocessor>-Meshing->Mesh>-Areas->Free,选择砂模;

14.对铸钢划分网格:Main Menu>Preprocessor>-Attributes->Define>Default Attribs, 在Material number菜单中选择2;

15.Main Menu>Preprocessor>-Meshing->Mesh>-Areas->Free,选择铸钢;

16.定义分析类型:Main Menu>Solution>-Analysis Type->New Analysis,选择Transient;

17.选择铸钢上的节点:Utility Menu>Select>Entities,选择element,mat,输入2,选择Apply,选择node, attached to element,选择OK;

18.定义铸钢的初始温度:Main Menu>Solution>-Loads->Apply>Initial Condit’n>Define,选择Pick all,选择temp,输入2875, OK;

19.选择砂模上的节点:Utility Menu>Select>Entities,Nodes, inverse

20.定义砂模的初始温度:Main Menu>Solution>-Loads->Apply>Initial Condit’n>Define,选择Pick all,选择temp, 输入80, OK;

21.Utility Menu>Select>Everything；

22.U tility Menu>Plot>Lines；

23.定义对流边界条件:Main Menu>Solution>-Loads->Apply>-Thermal ->Converction>On Lines,选择砂模的三个边界1,3,4, 在file coefficent框中输入80, 在Bulk temperature框中输入, 80;

24.设定瞬态分析时间选项:

Main Menu>Solution>Load Step Opts>Time/Frequenc>Time-Time Step,

Time at end of load step 3 Time Step size0.01 Stepped or ramped b.c. Stepped Automatic time stepping on