Modeling an "equivalent" plate to represent a waffle like structure
Modeling an "equivalent" plate to represent a waffle like structure
(OP)
To all
I am looking for a way of modelling a waffle-like structure by a simple equivalent plate. Creating all the waffle structure using to 2D element could be done. it's just a matter of taking the time. Because the waffle pattern is quite small compare to the overall size one could end up with a lot of elements. While I am sure I could run a very large model, I like to use elements where it matters.
What makes the geo a bit more difficult is that the waffle is partially hollow to accommodate small cooling channels.
So the questions are;
1. What would be the best way of approximating a typical waffle cross section to a (uniform) plate thickness? I think at this stage I am more interested in the stiffness being right
2. with an "equivalent" plate, stress prediction would not be correct (am i right??) so is there a way of scaling the stress to estimate the stress in the waffle ie the real structure
An hint, help would be appreciated
Thanks
Regards
JXB0809
I am looking for a way of modelling a waffle-like structure by a simple equivalent plate. Creating all the waffle structure using to 2D element could be done. it's just a matter of taking the time. Because the waffle pattern is quite small compare to the overall size one could end up with a lot of elements. While I am sure I could run a very large model, I like to use elements where it matters.
What makes the geo a bit more difficult is that the waffle is partially hollow to accommodate small cooling channels.
So the questions are;
1. What would be the best way of approximating a typical waffle cross section to a (uniform) plate thickness? I think at this stage I am more interested in the stiffness being right
2. with an "equivalent" plate, stress prediction would not be correct (am i right??) so is there a way of scaling the stress to estimate the stress in the waffle ie the real structure
An hint, help would be appreciated
Thanks
Regards
JXB0809





RE: Modeling an "equivalent" plate to represent a waffle like structure
perhaps the best way is to make a stand-alone model of the waffle, and to compare it to a simple plate model. then you should be able to trick the material properties to give you near the right stiffness. The advantage of doing it this way is you can then take displacement results from the full model, apply them to the detail waffle and get good estimates of stresses in the waffle.
the alternative these days to say "that's took much like hard work, i'll just model the waffle in the full model and let it run a minute or two longer".
remember the day when designers had to visualise their creations and make 2D drawings based on this understanding of their structure; as opposed today when we can make 3D models and we don't have to visualise (and understand ?) near so much.
another day in paradise, or is paradise one day closer ?
RE: Modeling an "equivalent" plate to represent a waffle like structure
A stand alone FE is on the "possible approach/method" list
Thinking along the line
Ixx value of the waffle = Ixx_waffle
Iplate = bt^3/ 12 = Ixx_waffle ---> tequivalent = (12*Ixx_waffle/b)^1/3
which obviously only works for one I value
RE: Modeling an "equivalent" plate to represent a waffle like structure
Alternatively adjust the depth to give the right EI in one direction, adjust the E in the other direction (if required), which will give you good results for deflection and bending moment, you can then calculate the bending stresses externally.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Modeling an "equivalent" plate to represent a waffle like structure