# Stresses at the edge of Tet Elements **URL:** \ **Category:** Uncategorized\ **Created:** [March 12, 2024, 3:20pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148 "2024-03-12T15:20:33Z")\ **Posts on this page:** 19\ **Page:** 2
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [March 13, 2024, 7:43pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/21 "2024-03-13T19:43:22Z")
Hi Prop, Nice to hear from you again. > [@prop\_design](#): > > some of the tests you’re doing seem to involve reentrant corners I’m just showing the elements of interest. The whole model is a simple cube . Meshed with tets and all have the same dimension. I haven’t rate it but mesh quality is off the scale. 😅 > **[Cube\_C3D10\_Mesh.inp](https://wetransfer.com/downloads/efb90799bc29ccb3b3c6c9570922989e20240313192810/6b2472)** > > 1 file sent via WeTransfer, the simplest way to send your files around the world > [@prop\_design](#): > > it’s good you are pounding on the software and finding issues though I hope the ccx community does not take this as malicious. My intention is to understand the weaknesses to get the best out of it… Abaqus has show a similar response for the simplest case. But unaveraged result from Calc\_em has light my bulb. Stress on the element with comond edge to the body edge is uniform. I have isolated some elments on top of the edge with that criteria and thinghs got much better. So that could be the workaround. ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/7/73363fa447156b28b3b67c8f3774929d7795f48c.png) > [@prop\_design](#): > > stress smoothing Don’t you think stress smoothing it’s masking the Stress Range.? Kind of like blurring the contour. Cheating oneself ---
**Author:** ![prop\_design](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/prop_design/32/197_2.png) [@prop\_design](https://calculix.discourse.group/u/prop_design)\ **Post date:** [March 13, 2024, 7:53pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/22 "2024-03-13T19:53:43Z")
hi disla, wrt to stress smoothing. it would be nice if the results matched reality. in many of the pictures posted above there are like polka dot stress distributions, in cylinders with contact. i have seen that many times too. there is no way that is real. if you try increasing the mesh density it doesn’t really help. all of the results i have seen with ccx contact just don’t look right. in my case, i can ignore it, since those areas are not critical for me. but if you really needed an accurate stress value in a contact patch, using ccx, i’m not sure what you would do. some of your other findings are interesting but i’m not sure what the issue is exactly. if you can test something without reentrant corners it may help debugging. i think if you have one node (reentrant) and the rest are not, it could be throwing off the element stress distribution. so it might be a type of issue, but not one you would encounter without reentrant corners. i don’t really know though. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [March 13, 2024, 7:58pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/23 "2024-03-13T19:58:57Z")
Really nice insight Victor!!!. I didn’t saw it when I was writing. 👌 ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [March 13, 2024, 10:21pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/24 "2024-03-13T22:21:00Z")
my cube example supported by elastic spring using coupling type distributing, but for contact two part use rigid body. I try to switch between each other, still shown uneven distribution for bad mesh pattern. Extending to several elements and multiply the height will not change the condition, this can be mean not problem in distribution at face loads. ![2024-03-14 05_39_49-](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/5/59e2b26cc54556111bf8d30228695d4dc9921760.png) ---
**Author:** ![vicmw](https://avatars.discourse-cdn.com/v4/letter/v/6de8d8/32.png) [@vicmw](https://calculix.discourse.group/u/vicmw)\ **Post date:** [March 13, 2024, 10:49pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/25 "2024-03-13T22:49:03Z")
Yea, my explanation doesn’t make so much sense for contact since they’re already nonlinear springs and you’d think they could/would adapt to the load distribution. But maybe they don’t? ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [March 14, 2024, 1:38am UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/26 "2024-03-14T01:38:44Z")
please ignore my last screenshot, it has problem in mesh. ![2024-03-14 08_36_05-Gmsh - C__Users_user_Documents_prob.msh](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/1/1566fb532b1de1af59ed9fc1363a59ea5dbd640e.png) edited: this is probably the correct ones (Gmsh, Transfinite, Recombine: No) i need to check further for both look like similar mesh pattern. ![2024-03-14 09_06_09-](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/d/da05e2dcc23c12f392193a1f47f2dbdffbad7860.png) ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [March 14, 2024, 12:07pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/27 "2024-03-14T12:07:20Z")
> [@Disla](#): > > [Unique Download Link | WeTransfer](https://wetransfer.com/downloads/efb90799bc29ccb3b3c6c9570922989e20240313192810/6b2472) ![2024-03-14 19_04_54-LISA](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/6/6322a2199afafebcef00d1c150d1418a14707e32.png) ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [March 14, 2024, 12:24pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/28 "2024-03-14T12:24:19Z")
> [@xyont](#): > > Gmsh, Transfinite, Recombine: No ![2024-03-14 19_22_20-LISA](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/b/b561eb6dddb76bfd81c8a51da32ccbd84c01972e.png) ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [March 14, 2024, 1:19pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/29 "2024-03-14T13:19:39Z")
Is this something for me or did you find something new? ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [March 14, 2024, 1:34pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/30 "2024-03-14T13:34:50Z")
first i tried to replicate the problem by create similar mesh pattern in [LISA](https://lisafea.com/), it seems to be failed in mesh conformity even solvable by CalculiX. Later i create from the base of CAD files then meshing using Gmsh,(Transfinity,Recombine:No) in PrePoMax, it has shown succeed. And the last i checked your mesh, did you trust the result and needed to go further when the mesh itself has a problem? p.s i do some mesh conversion between Inp file formal with Msh and Vtk to be readable of both pre-processor. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [March 14, 2024, 1:50pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/31 "2024-03-14T13:50:04Z")
> [@xyont](#): > > Later i create from the base of CAD files then meshing using Gmsh,(Transfinity,Recombine:No) in PrePoMax, it has shown succeed. Do you mean you have succed meshing a rectangle? > [@xyont](#): > > the mesh itself has a problem I don’t see any problem with the mesh. Not with Mecway at least. ¿Could you explain a little more? Inp file is a cube made of 8 x 8 x 8 cubes with 5 tets each one. 2560 Elements. ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/f/f8d4e456c33e58322c3c422d0ad2ff04abe112af.png) Seems you have lost some elements during the conversion. ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [March 14, 2024, 1:57pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/32 "2024-03-14T13:57:36Z")
nothing is lost during my conversions, PrePoMax also shown some sign it has a problem by displaying large internal boundaries in red lines. ![2024-03-14 20_52_32-LISA](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/d/d7926fd9d8b3bca95c80412a9a6862e11808bbb5.png) ![2024-03-14 20_53_23-PrePoMax v2.0.6](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/0/0558351f620a03ecb6f50b5a073b08a3ef65c056.png) a conformal mesh with the same edge division will generate 3072 elements and 729 nodes. ![2024-03-14 21_12_29-](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/3/3d4008166cd9acbc6190a6a43ce0ff86cd8ebbbd.png) ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [March 14, 2024, 2:42pm UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/33 "2024-03-14T14:42:45Z")
and the puzzle is ![2024-03-14 21_40_55-Calcpad 5.8.9](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/f/f2c5a27832fc344d9ac8769d8b286c6ddd04a256.png) tried different approach in mesher setting, ![2024-03-14 21_58_32-](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/b/b2e33b72c5fc4fee96b3d83ccadcd81d706890ec.png) ![2024-03-14 22_01_03-Calcpad 5.8.9](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/2/25da2e268d3760876dcf213c9e8599dbe460f581.png) ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [March 15, 2024, 10:12am UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/34 "2024-03-15T10:12:36Z")
> [@xyont](#): > > first i tried to replicate the problem by create similar mesh pattern in [LISA](https://lisafea.com/), it seems to be failed in mesh conformity even solvable by CalculiX That’s great!!. I’m sure users will appreciate that unnoticed bug inside the meshing tools of “LISA” 😉 . Specially known that conformity (edge conformity) could be lost unnoticed after a refinement process. My mistake and your findings will be very useful to others. Once I have fixed that on my mesh: -Things get slightly better but unfortunately don’t remove the wavy patterns. > [@xyont](#): > > ![2024-03-14 21_40_55-Calcpad 5.8.9](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/f/f2c5a27832fc344d9ac8769d8b286c6ddd04a256.png) This is not exactly right so I’m still in search of some procedure to detect nonconformal tet mesh (edge non-conformity) to avoid future problems. ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/4/404758213176e2b9a0cfcb9056149e5a957308cb.jpeg) > [@xyont](#): > > And the last i checked your mesh, did you trust the result and needed to go further when the mesh itself has a problem? I didn’t trust my results, that’s why I initiated this review process. Especially after you posted this: > [@xyont](#): > > I’m frequently in modeling of bolt and hole plate contact with quadratic tetrahedral element, even coarse (16 elements per circumference) have no issue like uneven spot stress. If that’s true, which I don’t doubt, It is still not clear where those wavy patterns come from. Maybe your holes are fully structured (that’s not the common case) and all the nodes at the edge share the same number of elements. That’s only possible in a closed edge but that’s the case. If so , I would say the averaging would provide a uniform stress distribution to the eye , but maybe wrong value. I need to look. ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [March 15, 2024, 11:02am UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/35 "2024-03-15T11:02:53Z")
> [@Disla](#): > > Things get slightly better but unfortunately don’t remove the wavy patterns. indeed, my second test of contact two part by similar pattern but conformal, still shown result uneven in distribution. > [@Disla](#): > > This is not exactly right so I’m still in search of some procedure to detect nonconformal tet mesh (edge non-conformity) to avoid future problems. so that’s puzzle, another setting can give true. First problem is in conformal mesh, and later in mesh pattern itself. > [@Disla](#): > > It is still not clear where those wavy patterns come from from fisrt screenshot of their global model, it has shown did not fit in curved geometry. Probably using linear tetrahedral element or midside node of quadratic did not set properly ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [March 16, 2024, 11:10am UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/36 "2024-03-16T11:10:10Z")
> [@Disla](#): > > Specially known that conformity (edge conformity) could be lost unnoticed after a refinement process. LISA is an old, being used by many students here since years. Refinement and conformal mesh depend on the steps in creating. Previously, i’m using manual duplicate after one cube of 40 elements generate then it failed. ![2024-03-16 18_04_36-](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/1/1d25ed15b959ed5dfce83daaf029754b56a419c9.png) it should not a problem without manual duplicating. ![2024-03-16 18_00_20-LISA](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/c/c23b1161a8bcdc6e4283ce3ef17f41c5c6373d3a.png) ![2024-03-16 17_59_34-](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/7/7691c5c05562e9538c103643d535512565f58603.png) ---
**Author:** ![OliverKunc](https://avatars.discourse-cdn.com/v4/letter/o/aca169/32.png) [@OliverKunc](https://calculix.discourse.group/u/OliverKunc)\ **Post date:** [May 13, 2024, 7:48am UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/37 "2024-05-13T07:48:07Z")
Thanks for this nice example! Haven’t seen this before. I find it a little bit surprising that you mention TET10 only at the end, seemingly as an alternative. So, as a reminder for everyone new to CCX or FEM in general: you should never ever use TET4 but only TET10. Basically, it doesn’t matter how exactly TET4 behave in any scenario because they are useless. See CCX manual or ask anyone with experience. ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [May 13, 2024, 7:53am UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/38 "2024-05-13T07:53:42Z")
> [@OliverKunc](#): > > you should never ever use TET4 Unless a ton of them is used, stress concentrations like this aren’t of interest or only heat transfer is considered, for instance. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [May 13, 2024, 8:57am UTC](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148/39 "2024-05-13T08:57:53Z")
Hi Oliver. You are right , the post started with TET10 until I focused more on the corners. Seems the source of those wavy patterns could be the different tet orientations converging on common corner nodes. > [@OliverKunc](#): > > TET4 behave in any scenario because they are useless. Well, I don’t agree completely. Everything has its use. You just have to find the right place for it. 🙂 [Previous page](https://calculix.discourse.group/t/stresses-at-the-edge-of-tet-elements/2148.md?page=1)