2D plane frame elements with different thicknesses to model a gripper

[brango]

Hello,

I am working on a compliant gripper. I optimized the gripper for maximum displacement using MATLAB. The optimized parameter is the thickness of each element.

I am having trouble modeling it with ansys. I have around 54 elements.

I tried at first to create 1 plane82 element type and after i created the keypoints and elements i discovered that you can assign only one thickness for the element type.

Should I create 54 plane82 elements each having a different thickness and then create the elements one by one ?

If yes, can it be done using APDL? because manually creating 54 element types and then associating each one to its corresponding element is long and subject to errors. I have read a simple tutorial about APDL but I dont understand its capabilities yet.

If no, what is the best way to do it ?

I attached a picture of the gripper design.

I appreciate any help you can offer me.

Thank you in advance.

 

[meshparts]

Hello,

you only need one element type but 54 real constants. If you know the thickness from Matlab then it would be easy to do it with APDL.

Just define a vector of thicknesses in matlab an save it as as Ascii file like thickness.dat (see command save in matlab).

Then read the vector in Ansys using *vread. Then define the real constants using a *do loop. Assigning the real constants to each element is done by emodif. Suposing the element numbers are same to the real numbers, the code could look like that:

*dim,thickness,array,54
*vread,thickness,thickness,dat
(1F6.3)
*do,i,1,54
 r,i,thickness(i)
 emodif,i,real,i
*enddo

Regards
Alex

 

[brango]

Hello,

I tried the code but it didnt work. It tells me:

"R is not a recognized BEGIN command"

Please can you further explain ?

Thank you.

 

[meshparts]

Hello,

It seems like you are a beginner in Ansys. I suggest you try a simpler tutorial first, because what you want to do is not really beginner level.

But anyway, the warning you are getting is because you are at the BEGIN level in Ansys. Type /PREP7 to get in the Preprocessor.

Regards
Alex

 

[brango]

Thank you for your willingness to help me.

Yes, I am a beginner in ANSYS. I checked some tutorials but theres nothing similar to my application. I found typical problems like a truss structure.

Also, I tried to search for tutorials on APDL, but i mostly found documentations that tell you what each command does.

If I could only get the part of code that u gave me to work, it would solve my problem. The rest are basic procedures just like in other tutorials (meshing, solving,etc...).

Right now Im having problems with (1F6.3). Obviously it is the format of the data. Does it mean float ? with 6 digits before decimal and 3 after ?

Its causing an error when I try it.

this is a sample of a thickness inside my thickness.dat file: 3.5778292e-004. This is how matlab saved it. im guessing it should be saved as 0.0003557 without the e-04 part right ?

I last thing. I didnt understand what does this line of code do: r,i,thickness(i)

Thank you.

 

[meshparts]

Hi,

yes (1F6.3) stands for float with 3 decimal and 6 digits in total. For your file format it should look like something this: (1E13.3). Not sure if it is right. You will have to play with these settings till it works. Also take a look at FORTRAN file descriptors in Internet.