Slab and steel column with steel plate

About the development of the FEM module/workbench.

Moderator: bernd

User avatar
bernd
Posts: 7902
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

Re: Slab and steel column with steel plate

Postby bernd » Sun Oct 21, 2018 7:21 pm

Before you gone start to play with multiple materials you should get your mesh working with one material. Your mesh has dozens of nonpositive jacobians ... see error in report view and python console and the green nodes ...

Code: Select all

>>> nonpositive_jacobian_elenodes = [166L, 167L, 172L, 173L, 174L, 174L, 174L, 175L, 176L, 182L, 183L, 186L, 186L, 188L, 189L, 190L, 190L, 191L, 191L, 191L, 192L, 240L, 240L, 240L, 241L, 241L, 241L, 243L, 243L, 243L, 250L, 250L, 251L, 251L, 251L, 253L, 253L, 253L, 268L, 269L, 271L, 271L, 278L, 279L, 281L, 741L, 749L, 749L, 753L, 756L, 756L, 760L, 762L, 769L, 769L, 777L, 777L, 783L, 791L, 795L, 798L, 802L, 804L, 805L, 805L, 805L, 805L, 805L, 808L, 809L, 809L, 811L, 811L, 812L, 812L, 812L, 816L, 819L, 823L, 825L, 825L, 862L, 862L, 870L, 874L, 877L, 881L, 883L, 883L, 890L, 898L, 902L, 904L, 904L, 912L, 912L, 916L, 919L, 919L, 923L, 925L, 925L, 925L, 926L, 926L, 926L, 926L, 929L, 930L, 930L, 932L, 933L, 937L, 940L, 940L, 944L, 946L, 1039L, 1040L, 1095L, 1096L, 1099L, 1099L, 1100L, 1101L, 1137L, 1138L, 1141L, 1141L, 1141L, 1142L, 1143L, 1143L, 1257L, 1257L, 1257L, 1257L, 1257L, 1258L, 1259L, 1262L, 1262L, 1262L, 1264L, 1264L, 1299L, 1299L, 1299L, 1299L, 1299L, 1299L, 1300L, 1301L, 1304L, 1304L, 1304L, 1306L, 3623L, 3623L, 3625L, 3625L, 3629L, 3663L, 3664L, 3670L, 3671L, 3692L, 3707L, 3708L, 3714L, 3715L, 3723L, 3724L, 3734L, 3734L, 3735L, 3740L, 3741L, 3809L, 3809L, 3810L, 3836L, 3836L, 3838L, 3838L, 3842L, 3876L, 3877L, 3883L, 3884L, 3904L, 3905L, 3905L, 3920L, 3921L, 3927L, 3928L, 3936L, 3937L, 3947L, 3947L, 3948L, 3953L, 3954L, 4022L, 4023L, 4023L, 4313L, 4315L, 4318L, 4322L, 4325L, 4334L, 4342L, 4343L, 4343L, 4346L, 4356L, 4358L, 4359L, 4365L, 4366L, 4372L, 4372L, 4374L, 4374L, 4376L, 4377L, 4377L, 4377L, 4379L, 4379L, 4379L, 4381L, 4382L, 4386L, 4387L, 4397L, 4553L, 4553L, 4571L, 4572L, 4572L, 4596L, 4596L, 4597L, 4597L, 4602L, 4603L, 4603L, 4606L, 4606L, 4607L, 4714L, 4714L, 4714L, 4730L, 4731L, 4731L, 4748L, 4748L, 4749L, 4754L, 4755L, 4758L, 4758L, 4759L, 5122L, 5122L, 5123L, 5123L, 5123L, 5128L, 5128L, 5129L, 5132L, 5132L, 5133L, 5139L, 5152L, 5161L, 5266L, 5266L, 5267L, 5267L, 5272L, 5272L, 5273L, 5276L, 5276L, 5277L, 5287L, 5287L, 5309L, 5310L, 5310L, 5494L, 5498L, 5498L, 5498L, 5499L, 5503L, 5504L, 5504L, 5504L, 5507L, 5507L, 5514L, 5514L, 5514L, 5515L, 5542L, 5546L, 5546L, 5547L, 5549L, 5551L, 5551L, 5552L, 5552L, 5558L, 5559L, 5559L, 5559L, 5609L, 5609L, 5609L, 5609L, 6772L, 6772L, 6773L, 6774L, 6774L, 6774L, 6798L, 6798L, 6799L, 6800L, 6800L, 6806L, 6806L, 6851L, 6853L, 6853L, 6853L, 6866L, 6866L, 6954L, 6954L, 6970L, 6970L, 6970L, 6974L, 6975L, 6975L, 6980L, 6980L, 6981L, 6981L, 6982L, 7002L, 7003L, 7003L, 7022L, 7022L, 7031L, 7031L, 7032L, 7063L, 7063L, 7069L, 7149L, 7238L, 7280L, 7309L, 7316L, 7468L, 7620L, 7620L, 7620L, 7654L, 7654L, 7669L, 7669L, 7682L, 7682L, 7685L, 7685L, 7695L, 7695L, 7704L, 7704L, 7705L, 7705L, 7706L, 7706L, 7716L, 7716L, 7788L, 7790L]
User avatar
bernd
Posts: 7902
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

Re: Slab and steel column with steel plate

Postby bernd » Sun Oct 21, 2018 7:52 pm

No wonder you have elements without material. FreeCAD only can assign a material to an element if it is inside the geometry. There are faces outside the geometry. As said before get it working with one material (BTW it works for me with max element size of 10 mm.)


Screenshot_20181021_215033.png
Screenshot_20181021_215033.png (333.17 KiB) Viewed 187 times
UR_
Posts: 856
Joined: Tue Jan 03, 2017 8:42 pm

Re: Slab and steel column with steel plate

Postby UR_ » Sun Oct 21, 2018 8:47 pm

Worst element's aspect ratio shouldn't really go far beyond 10.

Taken from here: https://caeai.com/blog/will-poorly-shap ... y-solution

2018-10-21 22_36_29-Will Poorly-Shaped Elements Really Affect My Solution_ _ CAE Associates.png
2018-10-21 22_36_29-Will Poorly-Shaped Elements Really Affect My Solution_ _ CAE Associates.png (56.12 KiB) Viewed 182 times

Salome's tools for mesh quality checking shows: there some elements with over 60!

2018-10-21 22_37_11-Mesh Information.png
2018-10-21 22_37_11-Mesh Information.png (6.62 KiB) Viewed 182 times
gnathan87
Posts: 7
Joined: Sat Oct 13, 2018 10:47 pm

Re: Slab and steel column with steel plate

Postby gnathan87 » Sun Oct 21, 2018 9:27 pm

Thanks guys. Yes, just to be clear, I just used the default mesh for the purposes of this post, it was not intended to be my final mesh (!!) I was really just trying to establish why, despite assigning materials to all solids, some elements were apparently not getting material assignments, and whether it might be due to a bug. However, I will see if the above suggestions explain the issue.
User avatar
bernd
Posts: 7902
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

Re: Slab and steel column with steel plate

Postby bernd » Mon Oct 22, 2018 6:15 am

There is no bug in this regard. You just have a very bad mesh. We might consider to print better message in such case. Gmsh sometimes makes very bad meshes with standard values.

Use 10 mm max element size for your mesh and you will be fine. But keep in mind inp file writing will take some tome due to the multi material element search in the mesh.

bernd
User avatar
bernd
Posts: 7902
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

Re: Slab and steel column with steel plate

Postby bernd » Mon Oct 22, 2018 6:20 am

_UR: interesting link
User avatar
bernd
Posts: 7902
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

Re: Slab and steel column with steel plate

Postby bernd » Mon Oct 22, 2018 10:24 am

@gnathan87: your file with multiple material, ... just changed max element size in Gmsh object to 10 mm, and have some patience ...


Screenshot_20181022_122000.png
Screenshot_20181022_122000.png (859.77 KiB) Viewed 140 times