# Any improvement of linear tetrahedral element? **URL:** \ **Category:** Uncategorized\ **Created:** [March 3, 2023, 9:45am UTC](https://calculix.discourse.group/t/any-improvement-of-linear-tetrahedral-element/1516 "2023-03-03T09:45:43Z")\ **Posts on this page:** 7\ **Page:** 1
**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 3, 2023, 9:45am UTC](https://calculix.discourse.group/t/any-improvement-of-linear-tetrahedral-element/1516/1 "2023-03-03T09:45:43Z")
hi all, is there any progress or improvement of linear tetrahedral element available out there for Abaqus/CalculiX? an example of user element. i read few of paper regarding to this topics. this can be large benefit for hexa-dominant meshing, since automatic mesh still contains of tetrahedral element generates. ![2023-03-03 16_31_48-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/9/975df688b8057bb1d916e18c8b78d275b5a52c87.png) ![2023-03-03 16_48_27-testhexdom.inp - SciTE](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/5/556fbf3e39fa47124c4bd436bce3540d51ef939c.png) it can be easily to switch to quadratic of both element type (hexa & tetra), but may lead to consequently in computational times and convergences of contact analysis. best regards, ---
**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:** [March 3, 2023, 11:06am UTC](https://calculix.discourse.group/t/any-improvement-of-linear-tetrahedral-element/1516/2 "2023-03-03T11:06:12Z")
What kind of improvement do you mean ? In Abaqus linear tetrahedrons (as well as linear triangles, pyramids and wedges) are described as having poor convergence rate with respect to mesh refinement. They also tend to overstiffen the results when bending is involved. Thus, they are recommended to be used only as filler elements, far from areas of interest. Otherwise, very fine meshes would be needed. ---
**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 3, 2023, 11:25am UTC](https://calculix.discourse.group/t/any-improvement-of-linear-tetrahedral-element/1516/3 "2023-03-03T11:25:37Z")
it seems Abaqus also still used old formulation, i’ll look at another FE codes for comparisons. an improvement of the element formulation itself, mesh refinement is a different things i think. there’s many paper has been discussed, ones are from K.J Bathe (2011) \*edited or maybe using burble function like below i extracted from [Ismail Caylak](https://ris.uni-paderborn.de/record/19187) (2011) ![2023-03-03 19_48_57-3-8440-0084-4_INH.PDF - Opera](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/a/afbda47322affa5e92fadb15d9345eb93ffc6704.png) ---
**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 3, 2023, 1:41pm UTC](https://calculix.discourse.group/t/any-improvement-of-linear-tetrahedral-element/1516/4 "2023-03-03T13:41:20Z")
AMPSTech seems to be the best wrt using all linear elements. In general, ANSYS has good element formulations. However, not on the level of AMPSTech, for using all linear elements. AMPS is available through IronCAD as well, as an add on. ---
**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 3, 2023, 2:09pm UTC](https://calculix.discourse.group/t/any-improvement-of-linear-tetrahedral-element/1516/5 "2023-03-03T14:09:28Z")
thank you for mentions to AMPSTech, interesting to know the technology applied, i was reading their white paper ([link](https://www.ampstech.com/ampstech/Asp/Customer.asp)). however, it’s closed and i’m seeking an implementation such as user element subroutine in CalculiX if available or possible. ---
**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 3, 2023, 2:33pm UTC](https://calculix.discourse.group/t/any-improvement-of-linear-tetrahedral-element/1516/6 "2023-03-03T14:33:12Z")
yeah i know what you mean. i’ve never actually used it, due to cost. it looks really interesting though. unfortunately, people often charge for new technologies. open source has been gaining steam but not necessarily in there area of cutting edge. there is one open source project that has some pretty cutting edge tech, though not in the area you are interested in. that project is MFEM. i’m hoping MFEM will gain more traction. i mentioned AMPS because that’s the only program i know of that does what you are interested in. ---
**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 3, 2023, 2:52pm UTC](https://calculix.discourse.group/t/any-improvement-of-linear-tetrahedral-element/1516/7 "2023-03-03T14:52:58Z")
> [@prop\_design](#): > > i mentioned AMPS because that’s the only program i know of that does what you are interested in. it’s okey, i’m also following any mainstream FE commercial software available. it seems to be right AMPS challenging them at the industry and real world application. design and regulation become more complex ,large scale, tight schedule, etc.