使用ANSYS建立模型经验和技巧

1、使用 Ansys软件建模的经验与技巧1.始终注意保持使用一致的单位制；2 求解前运行 allsel 命令求解前运行 allsel 能会没有传到 nodes or elements 上去；3 网格划分问题牢记建模与分网指南上有关建模的忠告。网格划分影响模型是否可用，网格划分影响计算结果的可接受程度；自适应网格划分(ADAPT)前必须查自适应网格划分可用单元，在 ansys 中能够自适应网格划分的单元是有限的。网格划分完成后，必须检查网格质量！权衡计算时间和计算精度的可接受程度，必要时应该 refine网格4 实体建模布尔运算应用实体建模以及布尔运算（加、减、贴、交）的优势解决建立复杂模型时的困难

2、；但是，没有把握时布尔运算将难以保证成功！5 计算结果的可信度一般来说，复杂有限元计算必须通过多人，多次，多种通用有限元软件计算核对，互相检验，相互一致时有限元分析不是搞什么英雄主义，而需要多方面的质量保证措施。6 了解最终所需要的成果建立模型之前，应该充分了解最终要求提交什么样式的成果，这样能形成良好的网格，早期良好的建模规划对于后期成果整理有很大的帮助；7 撰写分析文档文档与分析过程力求保持同步，有利于小组成员之间的沟通和模型的检验和查证；8 熟悉命令对没有把握的命令应该先用简单模型熟悉之，千万不能抱有撞大运的想法；9 多种单元共节点不同单元使用共同节点时注意不同单元节点自由度匹配问题导致

3、计算结果的正确与否(建模与分网指南P 8 ) 壳单元的转动自由度的含义不一样。壳的ROTZ不是真实的自由度,它与平面内旋转刚度相联系，在局部坐标中壳的单元刚度矩阵 ROTZ对应的项为零，对此不能将梁与壳单元仅仅有一个节点相连，例外的是当 shell43 or shell63(两者都有 keyopt(3)=2)的 Allman旋转刚度被激活时。Solid65 单元和 shell63 shell63 单元的转动自由度的节点唯一则不会传到相连的 solid65 单元上。10 查找文献资料确定混凝土的材料参数输入（ Tb, concr, , , ）11 预测内存和磁盘空间大型复杂模型（例如 10 万个

4、节点，非线性问题，多工况问题，1000 步以上的瞬态分析等等）求解之前预测求解所需要的求解时间、内存和磁盘空间，使分析尽在掌握之中；12 收敛问题题的建议；对于以下参数，可以试一试这些参数对收敛速度以及结果精度的影响neqit = 625?加载荷载步大小 = ？接触单元的实常数 = ？ 例如接触刚度的大小取值必须权衡计算结果精度（穿透大小）和收敛问题（ 收敛时间 ）两者的可接受程度，需要经验值或者试算；13 启动重分析14 两个相贯的薄壁圆筒建模，壳单元没有公共节点Element Connectivity Error, 8-Node Curved Shell ElementsIn this i

5、mage, the red stiffener was intended to be welded to the purple pipe. Note that the elements of the redstiffener do not match up with those on the pipe. There is no connection, and the meshing was done independently.This is due to a geometric modeling error by the user (me). There are superimposed c

6、urved lines where theinterface is located. There should have been a shared line for the connection to have worked. I found this onlybecause of careful examination of the model - I had already run a stress analysis.What to do about these error concerns? Read and think. Share and listen to ideas and c

7、oncerns with others. Reviewyour own work, and the work of your co-workers. (Recently an experienced co-worker who does not even do FEAwork asked me if I had eliminated the added mass of water in pipes when evaluating shipping loads on a product. Ihadnt. Eliminating the added mass got rid of a high-s

8、tress problem. These errors are very easy to make.) Befriendly. Communicate with other departments. Have a check list and design reviews. Never use FEA blindly, orbelieve the results of an analysis without some critical review. Accept a critical review without taking it personally.Develop a good und

9、erstanding of the intent of the design codes that regulate your work. Consult an expert when itis appropriate. Pay attention to the ethics and standards of your professional association. Choose your employerwisely. (Some of these things you were supposed to have learned in Kindergarten, but life isn

10、t always that simple.)解决方法：通过 volumn 建模形成相贯线，该方法建模使面相交处共线，xmesh后有公共 nodes15 选择集的应用为了利用选择集 cm / xsel 的强大功能，可以合理定义线，面的实常数 real 属性，为了选择操作方便而赋予更多的单元实常数号，材料号18 UPGEOM 和 MPCHG 的应用! UPGEOM更新几何形状!a.rst为计算结果文件名，最后一个为目录这两个参数应根据你的计算情况定UPGEOM,1,LAST,LAST,NEW,rst,F:729! MPCHG弹性模量恢复为真值esel,s,mat,3mpchg,4,allYou m

11、ight be tempted to try to deactivate or reactivate elements by changing their material properties MPCHG ( Main MenuPreprocessorMaterial PropsChange Mat Num ).However, you must proceed cautiously if you attempt such a procedure. The safeguards and restrictions that affectkilled elements will not appl

12、y to elements that have their material properties changed in SOLUTION. (Elementforces will not be automatically zeroed out;nor will strains, mass, specific heat, etc.) Many problems could resultfrom careless use of MPCHG . For instance, if you reduce an elements stiffness to almost zero, but retain

13、its mass,it could result in a singularity if subjected to acceleration or inertial effects.One application of MPCHG would be in modeling construction sequences in which the strain history of a bornelement is maintained. Using MPCHG in such cases will enable you to capture the initial strain experien

14、ced byelements as they are fitted into the displaced nodal configuration19 Ansys 中的坐标系统，使用各种坐标系时应该明白在各处理器中输入输出会受到那些坐标系的影响整体和局部坐标系 CSYS-用于定位几何形状参数的空间位置显示坐标系 DSYS-用于几何形状参数的列表和显示节点坐标系-定义节点自由度方向和节点结果数据的方法。输入数据时受到节点坐标系影响的有：约束自(从)自由度；在/POST26 中在节点坐标系下输出文件和显示的数据结果有：自由度解，节点荷载，反作用荷载；Forces are defined in the

15、 nodal coordinate system. The positive directions of structural forces and moments arealong and about the positive nodal axis directions. The node and the degree of freedom label corresponding to theforce must be selected NSEL , DOFSEL .单元坐标系-每个单元都有自己的坐标系，单元坐标系用于确定材料特性主轴，加面压力和和单元结果数据（如应力和应变）的输出方向；AN

16、SYS规定了单元坐标系的缺省方向；许多单元都有 keyopts 可用于修改单元坐标系的缺省方向；对于面和体单元而言，可以用 ESYS 命令将单元坐标系的方向调整到已定义的局部坐标系；结果坐标系 RSYS-/POST1 /POST1中结果数据换算到结果坐标系(RSYS)*GET, ACTSYS, ACTIVE,CSYS$ RSYS, ACTSYS使结果坐标系与激活的坐标系（用于定义路径）相匹配求解坐标系-PSD,CQC,SRSS RSYS,SOLU命令来避免在结果坐标系中发生变换，使结果数据保持在求解坐标系中。20 Ansys 5.7通过函数定义边界条件 5.6中介绍的表格化边界条件的扩展功能。

17、用户可以创建大量函数并存储起来，以便于将来使用。5.6 的表格化边界条件(Tabular boundary conditions)Tabular boundary conditions ( VALUE = % tabname %) are available only for structural (UX, UY , UZ, ROTX, ROTZ) and temperature degree of freedom (TEMP) labels and are valid only in static ( ANTYPE ,STATIC)and full transient ( ANTYPE ,TRANS) analyses.滞回曲线位移加载*DIM,dis,TABLE,9,1,TIME, ,DIS(1,0) = 0,1,2,3,4,5,6,7,8DIS(1,1) = 0,3,0,-3,0,4,0,-4,0D,22, , %DIS% , , , ,UZ, , , , ,ansys 5.6 help files- 2.6.3. Applying Loads Using TABLE Type Array Parame