# \*SHELL SECTION, COMPOSITE: a layer without an orientation inherits the previous layer's orientation instead of the section's ORIENTATION or the global axes **URL:** \ **Category:** Analysis issues\ **Created:** [October 19, 2026, 8:44am UTC](https://calculix.discourse.group/t/shell-section-composite-a-layer-without-an-orientation-inherits-the-previous-layers-orientation-instead-of-the-sections-orientation-or-the-global-axes/4193 "2026-10-19T08:44:43Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Sandervdb](https://avatars.discourse-cdn.com/v4/letter/s/49beb7/32.png) [@Sandervdb](https://calculix.discourse.group/u/Sandervdb)\ **Post date:** [October 19, 2026, 8:44am UTC](https://calculix.discourse.group/t/shell-section-composite-a-layer-without-an-orientation-inherits-the-previous-layers-orientation-instead-of-the-sections-orientation-or-the-global-axes/4193/1 "2026-10-19T08:44:43Z")
## Summary Manual 7.118 (\*SHELL SECTION) says a composite layer without an orientation takes the one given by the ORIENTATION parameter, if any. Manual 6.2.14 adds that a layer with no orientation gets the default shell axes, from the global x-axis projected on the shell. In `shellsections.f`, however, `iorientation` is set once to the section’s ORIENTATION. Every layer line that names an orientation overwrites it, and nothing resets it. So a later layer line without an orientation silently gets the previous layer’s orientation. In the deck below, plies OR90 / (none) / OR90 run as 90/90/90 instead of 90/0/90. The same happens when the section itself has an ORIENTATION. Master (9ba5d76) still has the bug: `shellsections.f` was last changed on 6 Oct 2026, for ANISO\_CREEP/JOHNSONCOOK names. ## Version ccx 2.23 (conda-forge build pl5321h484372f\_2, macOS arm64). ## Already reported or fixed? Not reported: there is no matching GitHub issue (open or closed) or open pull request in Dhondtguido/CalculiX, and no calculix.discourse.group topic (searched 19 Oct 2026). Not fixed: the routine involved is unchanged on master, and conda-forge’s latest 2.23 build (pl5321hd17ca8b\_8, which carries about 40 extra patches) gives the same output. ## Minimal input `plies_blank.inp` is one S8R (unit square) of a unidirectional material: E1 = 100000, E2 = E3 = 10000, three plies of 1/3, stretched by 0.1 % along x. ```auto *HEADING One S8R, three plies: OR90 / no orientation / OR90; uniaxial stretch along x *NODE 1, 0., 0., 0. 2, 1., 0., 0. 3, 1., 1., 0. 4, 0., 1., 0. 5, 0.5, 0., 0. 6, 1., 0.5, 0. 7, 0.5, 1., 0. 8, 0., 0.5, 0. *ELEMENT, TYPE=S8R, ELSET=EALL 1, 1, 2, 3, 4, 5, 6, 7, 8 *NSET, NSET=NALL 1, 2, 3, 4, 5, 6, 7, 8 *NSET, NSET=X0 1, 4, 8 *NSET, NSET=X1 2, 3, 6 *MATERIAL, NAME=UD *ELASTIC, TYPE=ENGINEERING CONSTANTS 100000., 10000., 10000., 0.3, 0.3, 0.3, 5000., 5000., 5000. *ORIENTATION, NAME=OR90 0., 1., 0., -1., 0., 0. *SHELL SECTION, ELSET=EALL, COMPOSITE 0.333333333333, , UD, OR90 0.333333333333, , UD 0.333333333333, , UD, OR90 *BOUNDARY X0, 1, 1 1, 2, 2 NALL, 3, 3 *STEP *STATIC *BOUNDARY X1, 1, 1, 0.001 *NODE PRINT, NSET=X1, TOTALS=ONLY RF *END STEP ``` The reference `plies_explicit.inp` is the same deck with the middle ply naming the global axes: ```auto *ORIENTATION, NAME=OR0 1., 0., 0., 0., 1., 0. ... 0.333333333333, , UD, OR0 ``` ## How to run `ccx plies_blank` and `ccx plies_explicit` ## Expected Layup [90/0/90]. Laminate theory gives Nx = (A11 - A12^2/A22) \* 0.001 = 40.23 per unit width. ccx gives this for `plies_explicit.inp`: total RF\_x on X1 = 4.022304E+01. ## Actual `plies_blank.inp`: total RF\_x on X1 = 1.000000E+01. That is the [90/90/90] answer: laminate theory gives 10.00, and the same deck with all three plies naming OR90 also gives 1.000000E+01. With `*SHELL SECTION, ELSET=EALL, COMPOSITE, ORIENTATION=OR0` and the middle ply line left without an orientation, ccx also gives 1.000000E+01, where 4.022304E+01 is expected. ## Where it goes wrong `src/shellsections.f` (2.23 and master). `iorientation` is set from the ORIENTATION parameter before the layer loop (lines 121-135). Inside the loop (lines 313-331) it changes only when a layer names an orientation: ```fortran ! reading the orientation, if any ! if no orientation is specified, the global orientation defined ! by the ORIENTATION parameter, if any, will be used ! read(textpart(4)(1:80),'(a80)',iostat=istat) orientation ! if(orientation(1:1).ne.' ') then do i=1,norien if(orname(i).eq.orientation) exit enddo ... iorientation=i endif ``` Then `ielorien(nlayer,...)=iorientation` (lines 357 and 384) stores whatever is left from the previous layer. The comment in the code describes the documented behaviour. ## Fix Keep the section’s orientation and start every layer from it, e.g. with a new integer `iorientation0`: ```fortran ! before the layer loop (nlayer=0) iorientation0=iorientation ... ! for each layer, before reading its orientation iorientation=iorientation0 read(textpart(4)(1:80),'(a80)',iostat=istat) orientation ``` Workaround: give every layer line an orientation, using an identity `*ORIENTATION` for the global axes, as in `plies_explicit.inp`. ---
**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:** [October 19, 2026, 8:48am UTC](https://calculix.discourse.group/t/shell-section-composite-a-layer-without-an-orientation-inherits-the-previous-layers-orientation-instead-of-the-sections-orientation-or-the-global-axes/4193/2 "2026-10-19T08:48:30Z")
Confirmed (using official build of ccx 2.23 on Windows), needs a GitHub ticket. plies\_blank.dat: ```auto total force (fx,fy,fz) for set X1 and time 0.1000000E+01 1.000000E+01 -9.816327E-12 4.000619E-13 ``` plies\_explicit.dat: ```auto total force (fx,fy,fz) for set X1 and time 0.1000000E+01 4.022304E+01 1.057607E-11 6.308851E-13 ``` ---
**Author:** ![Sandervdb](https://avatars.discourse-cdn.com/v4/letter/s/49beb7/32.png) [@Sandervdb](https://calculix.discourse.group/u/Sandervdb)\ **Post date:** [October 19, 2026, 8:50am UTC](https://calculix.discourse.group/t/shell-section-composite-a-layer-without-an-orientation-inherits-the-previous-layers-orientation-instead-of-the-sections-orientation-or-the-global-axes/4193/3 "2026-10-19T08:50:02Z")
Posted: [\*SHELL SECTION, COMPOSITE: a layer without an orientation inherits the previous layer's orientation instead of the section's ORIENTATION or the global axes · Issue #220 · Dhondtguido/CalculiX · GitHub](https://github.com/Dhondtguido/CalculiX/issues/220)