Ionut Cosmin
Aerospace
- Jul 22, 2016
- 24
Hello everyone,
I am currently modelling a part with finite elements in Patran, and I have encountered a small problem. Basically I have a part that is made out of several hollow beams and solid plates, and I have modeled everything with shell elements. The problem occurs at 4 beams that run through the whole part, these beams have a square hollow variable section (it starts at 14 mm edge length and ends at 10 mm). All the beams in the part were modeled with shell elements constructed at the mid-surface of the section, except for these 4 beams for which the elements where constructed on the exterior surface (I had to use the exterior surface because of the way the part was designed, it was easier to model this way).
Now I have 2 questions regarding my FE model:
1. As you can see on the picture I have attached, when I input the shell properties I use a shell offset for the thickness, this generates a material overlap which basically increases my overall mass. Because the thickness is quite high (3mm) and there are 4 beams I get a difference between the mass of my FE model and the mass of the CAD model of 170 grams (CAD Model: 2800 g and FEM Model: 2970), an error of 6%. How can I reduce this difference ? (without changing the FEM model)
2. Is this material overlap increasing the stiffness of the model ? will this have a very big impact on the overall strength and give wrong results ?
Thank you very much,
Cosmin
PS: Sorry for my English, I am not a native.
I am currently modelling a part with finite elements in Patran, and I have encountered a small problem. Basically I have a part that is made out of several hollow beams and solid plates, and I have modeled everything with shell elements. The problem occurs at 4 beams that run through the whole part, these beams have a square hollow variable section (it starts at 14 mm edge length and ends at 10 mm). All the beams in the part were modeled with shell elements constructed at the mid-surface of the section, except for these 4 beams for which the elements where constructed on the exterior surface (I had to use the exterior surface because of the way the part was designed, it was easier to model this way).
Now I have 2 questions regarding my FE model:
1. As you can see on the picture I have attached, when I input the shell properties I use a shell offset for the thickness, this generates a material overlap which basically increases my overall mass. Because the thickness is quite high (3mm) and there are 4 beams I get a difference between the mass of my FE model and the mass of the CAD model of 170 grams (CAD Model: 2800 g and FEM Model: 2970), an error of 6%. How can I reduce this difference ? (without changing the FEM model)
2. Is this material overlap increasing the stiffness of the model ? will this have a very big impact on the overall strength and give wrong results ?
Thank you very much,
Cosmin
PS: Sorry for my English, I am not a native.