You are here
In reply to Cohesive Zone Model in ANSYS
I got the following answers from ANSYS support and I thought may be someone want to know:(I am using ANSYS APDL 14.5)
1-In Workbench V15, we can do cohesive zone modeling based on interface elements. Also we can do two way Fluid Solid interaction problem in Workbench. Currently you are using FLOTRAN for FSI problem. I am not sure if ANSYS supports this anymore because I could not find anything in the help manual.
2-Yes, this is correct.
4-There is no special feature in APDL to mesh elliptical areas. You need to split the areas and use mapped meshing.
5-Yes you need to clear the physics before defining a new physics. Attached is one example I found on the internet. In this I noticed, that the author first defined the Fluid physics, then solid physics and at the end solved the FSI using FSSOLVE command. In FSSOLVE command we specifying the physics fluid and solid. This is how it recognizes all the information. (I could not attach here so I put the link of the website he used):
6-According to the attached paper, while defining FLUID physics we need to make solid elements as null and vice versa.
7-If the area are glued then while meshing interfaces will have shared nodes. CZMESH will only work on the shared nodes. So we need to glue the areas so that sharing nodes could be generated. Merging is an option where we can merge the two coincident nodes, area, element, etc.
P.S. But I do not think that it is completely correct. I guess you can use Merge instead of glue for CZM and it was working for me so I guess there is no need to have shared nodes but it is my idea. You can also look at the last chapter of this thesis I found:
8-According to the attached paper, I modified your input file. And now it is running fine. The major change I did is that first defined the FLUID physics and then SOLID physics. I am not sure about the results. Please validate it.
Please If you have more information let me know.
Perhaps this might be of help:
In reply to Education in China and in America
I wrote this post in 2007. The post comes to the list of Popular Content on iMechanica this morning. China has changed a lot. Thinking about my trip to China in May this year and now reading this old post, I feel even more that my own years as a college student was such a distant past. The government has long stopped assigning jobs to college graduates. Young people (and their parents) need to consider the job market when they enter the colleges. This condition must have a profound effect on education and on the choice of college majors. It will be interesting to compare education in China and in US and Europe again. What do you think?
In reply to Reading PDF files using iPad 3
By accident I landed on this old post today. I am still using these three items
- iPad Air. Its storage is larger than the storage of iPad 3. The resolution of the screen seems to be the same as iPad 3.
- Dropbox. I use Dropbox for placing most files in the cloud, so that all devices have the same files. This function has remained unchanged. Unfortunately, Dropbox is nearly inaccessible in China. My Chinese collaborators have stopped using Dropbox. That means we do not have shared folders now. We are exploring services other than Dropbox. Annoying!
- PDF Expert 5. I read nearly all PDF files using PDF Expert 5 on iPad. PDF Expert 5 synchronizes files with Dropbox, in a way I described in the original post. A small change in Version 5 has made a big difference to me. There is no stop from one page to another.
I read a lot, mostly papers and textbooks, in PDF format, mostly in bed, when light is not on. PDF Expert 5 allows me to annotate and search. I have nearly completely stopped reading papers and books on paper.
Do you have any update on how you read? Have you discovered any useful software and cloud service?
In reply to elastic follow-up
Same here. I have learned a lot through your blog and I think that discussing published papers is a fantastic idea.
Please continue with it.
In reply to Run Abaqus from a Java code
May be there are a lot of ways to link two softwares .... but my suggestion is to use an interface files to link your java and abaqus...
this interface files is not a complicated files ... this files is just a text file you use to store the data in it ... both abaqus and java read the interface data from this files ....
for example one file for reading stress, one file for reading strain, one file to tell abaqus to continue or stop and one file to tell java to continue or stop....
I used this method for linking matlab and ansys ... this is my own created method, may be there is other better methods...
In reply to VUMAT of Drucker Prager, help needed please..
you had a post before and I answered your post but you didn't reply that post, Plase let other know you have solved your problem...
Sometimes "small" deviation in your answere and other Fe codes are quiet normal, I will tell you my experience ...
I wrote a full FE code in Fortran two years ago(Drucker prager model), and I compared my code by ansys and I found some deviation...
My code was correct but the deviation was because of the number 1 in below. there may be many reason for deviation:
1- Ansys is using different shape function for elements(extra shape functions) ( I used classical shape function)
2- Ansys may use different number of integration point
3- Ansys may use B_bar method for calculation of volumetric constrains...
After I changed the setting of the ansys to have same option as my code, my result became accurate up to four floating point.
In your case may be the same happens in abaqus, may be when you use Vumat the abaqus disables some option for elements...
The first step I suggest is to set initial yield condition vey high in order that plastic flow wont happen... then check your elastic answer with the one in original built-in abaqus... this helps you to make sure the deviation is not because of element options ....
In reply to keywords error in vumat
I think you should look at the abaqus keywords manual. Your questions are basic abaqus questions, that can be resolved just by looking at the manuals.
I am waiting for John Hutchinson's respopnse. It is impolite to post emails others sent to you, unless you are showing them as evidence of misdemeanor.
Can you, pleas, show full conversation.
In reply to Presumably a needless conversion
I want to write umat again, but I have a problam on state variable in umat. How can I give initial value to STATEV? I should write "initial condition, Type= Solution" in keywords?
Hi every one
I want to introduce a porous material to abaqus in order to simulate the heat transfer through that... means showing the heat doesnt transfer through voids...
All I have found is about introducing porous media in abaqus for mechanical analysis.
I want to just model a porous material
It is aluminum foam
Plzzzzzz help me if you know
In reply to corotational concept
thanks all Dear friend for colloboration.
His question is not about objective rates jaumman(corotational) or other rates... I had the same mistake first, his question is about the kinematic description of a geometrically nonlinear problem. as you know there are three description for geometrical nonlinearity:
corotational description usually deal with large rotation and small strains ... we don't need just rate formulation to describe material behavior ... energy( hyper-elastic for example) formulation can be used too in corotational description...
you are right the bar element stiffness matrix is not diagonal, i made mistake ... thank you for correcting me
however I find this useful ...
Corotational total Lagrangian formulation for three-dimensional beamelement
KUO M. HSIAO
Read More: http://arc.aiaa.org/doi/abs/10.2514/3.10987?journalCode=aiaaj
In reply to Actualy I'm not an expert in
The stiffness matrix for a bar element is not diagonal in local cooridinate system. More importantly the discussion of rotation from local coordinate system to global coordinate system is completely different from the discussion of corotational rates. A corotational rate for example with respect to spin tensor is written like this:
å = d(a)/dt - wa + aw
which is objective under rigid body rotation.
In reply to thanks for your response.
Actualy I'm not an expert in beam theory but I can give some idea for clarification
In Corotational concept a local frame is attache to element or integration point. The local tangent stiffness matrix in this case is different from the global stiffness matrix. for example for a rotated rod the local stiffness matrix is a diagonal matrix, since the rod axial force is just dependent on deformation of axial displacement (not tangential or transverse displacement), but the global stiffness matrix has both diagonal and non-diagonal terms, the global stiffness matrix is resulted by rotating the local stiffness matrix.
since in TL formulation you drive all derivatives(gradient operators) base on material refrence coardinates, your coardinates can not be rotated. you should deal with refrence coardinates.
but if you still want to use a local frame attached to the element, it is ok, you can have discret deformation gradients by the chain rule and this formula:
where zeta is your local coardinate parameter....
In reply to Hi
thanks for your response.
I study geometrically nonlinear euler bernoulli beam. beam remains elastic. I obtain tangent stiffness matrix in TL approach. but there are tangant terms in tangent stiffness matrix. I want to use a local frame attaching to element(similar to corotational concept) and then continue problem.