超弹性+粘弹性材料问题（请大家帮忙看看）

rz_ca

大家好，本人在Canada上学，也是搞 simulation的，最近搞的一个题目是超弹性+粘弹性材料 (hyperelastic +viscoelastic combination). 问题是如果单独用hyperelastic (neo-hookean) material, 题目可以顺利完成，但加入 viscoelastic(one term prony)以后，计算就会中途终止。而且在加载的边上有 volumetric locking 的现象。 我担心是我用的教学版Ansys材料属性不全， 所以请哪位手里有高版本Ansys 的帮忙运行一下，看看是否也会中途停止。下面是我对问题的全面描述， 后面附了 input 文件， 多谢大家了。




Hi everyone,
I'm having trouble when using the combined hyperelastic material(neo-hookean) with viscoelastic (one term prony) in Ansys. The problemis a cone being pulled by uniform pressure at the top and fixed at the
bottom. Plane183 (8 node plane element with uniform reducedintegration) is used with axisymmetric option. This element empolyedmixed u-p formation. The hyperelastic material is assumed to beincompressible (u=0.5) or nearly incompressible (u=0.4995). (actuallyif use u=0.4995, Ansys will not run at all, the element will not format the first substep)

The model runs fine if only the neo-hookean hyperelastic
material (u=0.5) is used but will crash at about 30% of completionwhen viscoelastic material is combined. By looking at the hydrostaticpressure distribution in post-processing, there is obvious checkerboardpattern along the loading edge, so it seems that volumetric lockingcauses the analysis to stop.

My question is why this happens when viscoelastic material is combined but not happens when only hyperelastic material is used.

My guess is our version of Ansys is too limited (university intermediate version)?

So if anyone in this forum has higher version Ansys in his/herhand, can he/she kindly run this analysis for me and see if it's due tothe version problem?


The attached input file ?scripts_e02r1pull? combines hyperelasticand viscoelastic material. The run will take only a couple of minutes.Thanks a lot.

rz


/BATCH
/FILNAME,e02r1_pull,0
/TITLE,e02r1

/PREP7

/com  >> define element type and material
ET,1,PLANE183   

KEYOPT,1,3,1
KEYOPT,1,6,1
KEYOPT,1,10,0   

TB,HYPE,1,1,2,NEO   
TBTEMP,0
TBDATA,,1,0,,,,

TB,PRONY,1,1,1,SHEAR
TBTEMP,0
TBDATA,1,0.4,14,,,,  

/com TB,PRONY,1,1,1,bulk
/com TBTEMP,0
/com TBDATA,,0.4,2,,,,

/com  >> define keypoint
K,1,0,0,,   
K,2,0,1,,   
K,3,1,0,,   
K,4,0.1,1.012916581,,   
K,5,0.117647058,0.993055471,,   
K,6,0.12,0.992916581,,
K,7,0.6,0.992916581,,  
K,8,0.1,1.6,,


/com  >> generate quater circle  
FLST,2,2,8  
FITEM,2,0,0,0   
FITEM,2,1,0,0   
CIRCLE,P51X, , , ,90, ,

/com  >> generate straight lines
LSTR,       9,       1  
LSTR,       1,       10
LSTR,       8,       4  
LSTR,       6,       7

/com  >> generate small circle
LARC,       4,       6,       5

/com  >> divide lines
LDIV,       1,  0.70  

/com  >> copy contact zone lines
LGEN,2,7, , ,0,-0.04, , ,0

/com  >> shorten copied lines
LDIV,       8,  0.4539919309218844E-01  
LDELE,       8

LSTR,      11,      14
LSTR,      10,      13


/com  >> create area
AL,10,7,9,8

LSBL,       3,       9
AL,9,11,8,1,2

/com  >> manual meshing the contact zone
/com  >> transverse lines
LESIZE,8, , ,5, , , , ,1
LESIZE,7, , ,80, , , , ,1

/com  >> mesh the area
MSHAPE,0,2D
MSHKEY,1
AMESH,1,1   

SMRT,4  
MSHKEY,0
AMESH,2,2

SAVE

/com >> apply surface load
DL,10, ,UX,0  
DL,11, ,UX,0  
FLST,2,68,1,ORDE,3  
FITEM,2,1
FITEM,2,290
FITEM,2,-340
SF,P51X,PRES,-2.5

NSEL,S,node,,1418,1452
NSEL,a,node,,1372,1372
NSEL,a,node,,1373,1373

D,all,UY,0,         ! APPLY DISPL
NSEL,ALL

/COM, CONTACT PAIR CREATION - START
   
/COM, CONTACT PAIR PROPERTIES - END

/sol
/com >>analysis parameters
ANTYPE,0
NLGEOM,1
NSUBST,100,10000,30
OUTRES,ALL,3
AUTOTS,1
NEQIT,80
RESCONTRL,DEFINE,ALL,3,10
TIME,1

/com >>message display control
/UIS,MSGPOP,3
/NERR,0,10000,  


/com >>nonlinear diagnose
NLDIAG,MAXF,16  
NLDIAG,NRRE,1   
NLDIAG,EFLG,1   
NLDIAG,CONT,1  

/com >>run the job
SOLVE  

/com 2nd step
/com nsubst,50
/com time, 2000
/com solve   
FINISH  
! /EXIT,ALL

jinqinghai

Give out your project description!
Herein attached your results.
By the way, which university and what majore you are?

rz_ca

Hi jinqinghai,
Thanks a lot for your help. It seems your results are the same as those obtained from my version of Ansys. So maybe I should check on the model.


This question is from a  biomedical engineering project I'm doing right now. Our lab is using micropipette aspiration to measure the material property of a living cell. To be able to do that, the experimental results need to be compared with FEA results. So this question actually shows the cell being sucked into a pipette.


I'm doing my PhD in biomedical engineering at U of Toronto. Hope I can discuss more technical questions with you (and you guys) in the future time.


Thanks.

[ 本帖最后由 rz_ca 于 2007-6-15 21:55 编辑 ]

jinqinghai

I am Master of engineering in U of Alberta.
Any questions and comments are welcomed.

jinqinghai

Similar project to explore the characteristics of viscoelatic material.
see the attached

rz_ca

Hi qinghai,
Can you post the material definition of the above example? Because I'm wondering that either the material failed or the element failed in my problem. And also the strain seems not too large in your example, which means the material has not yet  reached the failure?

jinqinghai

my second plot is displacement profile without disp. distribution plot.
the large displcement is 0.1 as designated by project objective.

large displacement of twice ball radius as follows:

[ 本帖最后由 jinqinghai 于 2007-6-18 13:53 编辑 ]

jiajia51

看到发的命令流，能给我一点粘弹性分析资料吗？ 邮箱jiajia51@tom.com谢谢

jinqinghai

原帖由 jiajia51 于 2007-10-27 17:03 发表
看到发的命令流，能给我一点粘弹性分析资料吗？ 邮箱jiajia51@tom.com谢谢

I have some, but I can't transfer others resources without permission.

[ 本帖最后由 jinqinghai 于 2007-10-28 04:35 编辑 ]

zhtd2004

请问版主     刚柱体对超弹粘弹性材料的压凹痕变形用ANSYS/DYNA做是否合适呢？  还是用ANSYS 接触分析做更合适呢？

zhtd2004

请问楼主  如何将一种材料附上两种属性呢  请不吝赐教

wei284560702

好贴！nice
结果如何？

672644487

有没蠕变方面的材料啊？

FoRd

期待斑竹解答

qyt913

9# jinqinghai     请教版主，一种属性为超弹性固体和无粘性流体的物体，应该如何选取单元？

gaohaiping_sky

太高深了，我们这些初级人物只有学习的份了

dzgzpy

07年的帖子被顶上来啦  我也在学ansys呢 发现斑竹也是ua的啊  现在还在学校吗？

fzkjlt123

好，

ctfy-1987

你好！你能给我传一下你的超弹性和粘弹性合在一起的资料吗我的Q411293490

NEO_NEO

强人太多了，看的我都是膜拜啊