# Plastic, creep or user material: segfault in \*NO ANALYSIS, \*BUCKLE, \*COMPLEX FREQUENCY, a linear \*STATIC after \*FREQUENCY, and modal steps with S/RF output

**URL:** <https://calculix.discourse.group/t/plastic-creep-or-user-material-segfault-in-no-analysis-buckle-complex-frequency-a-linear-static-after-frequency-and-modal-steps-with-s-rf-output/4243>\
**Category:** Analysis issues\
**Created:** [October 22, 2026, 7:00pm UTC](https://calculix.discourse.group/t/plastic-creep-or-user-material-segfault-in-no-analysis-buckle-complex-frequency-a-linear-static-after-frequency-and-modal-steps-with-s-rf-output/4243 "2026-10-22T19:00:53Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Sandervdb](https://avatars.discourse-cdn.com/v4/letter/s/49beb7/32.png) [@Sandervdb](https://calculix.discourse.group/u/Sandervdb)\
**Post date:** [October 22, 2026, 7:00pm UTC](https://calculix.discourse.group/t/plastic-creep-or-user-material-segfault-in-no-analysis-buckle-complex-frequency-a-linear-static-after-frequency-and-modal-steps-with-s-rf-output/4243/1 "2026-10-22T19:00:53Z")

</div>

## Summary

A model whose material has `*PLASTIC`, `*CREEP`, `*MOHR COULOMB`, `*DEFORMATION PLASTICITY` or `*USER MATERIAL` crashes with a segmentation fault (exit status 139, no message) in these steps:

- any `*NO ANALYSIS` step, also as the first step;
- any `*BUCKLE` step, also as the first step;
- a `*STATIC` step without NLGEOM after a `*FREQUENCY` step, a `*STEP, PERTURBATION` `*STATIC` step, and a `*VISCO` step after a `*FREQUENCY` step;
- a `*MODAL DYNAMIC` or `*STEADY STATE DYNAMICS` step that writes stresses (`*EL FILE` S), reaction forces (`*NODE PRINT` RF, `*NODE FILE` RF) or contact output (`*CONTACT FILE` CDIS, `*CONTACT PRINT` CSTR); with `*NODE FILE` U only these steps run;
- a `*COMPLEX FREQUENCY, CORIOLIS` step.

There are two exceptions, both in the material table below. A `*BUCKLE` step with the user material runs. With `*DEFORMATION PLASTICITY`, the `*FREQUENCY` step stops first, with an error message. The loads are far below yield, so the material stays elastic. The same decks run to the end when the material is elastic, elastic with `*DEPVAR`, or `*HYPERELASTIC`. A `*FREQUENCY` step of the plastic model runs as well.

In every case the backtrace ends in a material routine that reads a field nobody allocated, called through `results()` by the procedure routine: `linstatic()`, `arpackbu()`, `dyna()`, `steadystate()` or `complexfreq()`. These routines call the material routines (`incplas_lin`, `mohrcoulomb`, `umat_abaqusnl_total`, user materials through `resultsmech`), but they never allocate `xstateini` (the state variables at the start of the increment). `linstatic.c` allocates it only for contact. For user materials `linstatic`, `steadystate` and `complexfreq` also leave `vini` unallocated, and `dyna` leaves `stiini` and `emeini` unallocated. `arpack.c` (`*FREQUENCY`) allocates all of them, and its comment says what the state copy is for. That is why the frequency step runs.

All the cases have this one cause: the routines that ccx uses for linear steps evaluate the nonlinear material without the fields it needs. `*NO ANALYSIS`, `*FREQUENCY`, `*BUCKLE` and `*COMPLEX FREQUENCY` set `iperturb(1)=0`. That sends the `*NO ANALYSIS` step itself, and any later `*STATIC` or `*VISCO` step without NLGEOM, to `linstatic()`. A `*STEP, PERTURBATION` `*STATIC` step goes there too. `*BUCKLE`, `*MODAL DYNAMIC`, `*STEADY STATE DYNAMICS` and `*COMPLEX FREQUENCY` have their own routines.

## Version

ccx 2.23 (macOS arm64). Source: master 9ba5d76 (16 Oct 2026).

## Already reported or fixed?

Not reported: I found no matching GitHub issue (open or closed) or pull request in Dhondtguido/CalculiX, and no calculix.discourse.group topic (searched 21 Oct 2026). Not fixed: `linstatic.c`, `arpackbu.c`, `dyna.c`, `steadystate.c` and `complexfreq.c` still have no allocation of `xstateini` outside contact on master (9ba5d76).

Related:

- [Linear \*STATIC step: \*EL FILE with SDV segfaults when the model has \*DEPVAR (xstaten is never allocated in linstatic.c) · Issue #221 · Dhondtguido/CalculiX · GitHub](https://github.com/Dhondtguido/CalculiX/issues/221) (open): a different array in the same routine. `linstatic.c` never allocates `xstaten`, so `*EL FILE` SDV segfaults in a linear `*STATIC` step of a model with `*DEPVAR`. A fix for #221 alone does not allocate `xstateini`, `vini`, `stiini` or `emeini`.
- [Segmentation fault with ccx\_2.19 dynamic modal analysis](https://calculix.discourse.group/t/1156:) the closest topic, a segfault in a modal dynamic step of the shell example shellf.inp. That thread points to the shell elements, not to the material, so it is a different case (a NULL work array for the mean-rotation MPCs in `dyna.c`, reported separately).

## Minimal input

`plastic_buckle.inp` is one C3D8 cube with an isotropic plastic material (yield 250), clamped at z = 0, and a buckling step with 1 N per top node:

```auto
*NODE
1, 0., 0., 0.
2, 1., 0., 0.
3, 1., 1., 0.
4, 0., 1., 0.
5, 0., 0., 1.
6, 1., 0., 1.
7, 1., 1., 1.
8, 0., 1., 1.
*ELEMENT, TYPE=C3D8, ELSET=EALL
1, 1, 2, 3, 4, 5, 6, 7, 8
*NSET, NSET=Z0
1, 2, 3, 4
*NSET, NSET=TOP
5, 6, 7, 8
*MATERIAL, NAME=STEEL
*ELASTIC
210000., 0.3
*PLASTIC
250., 0.
300., 0.1
*DENSITY
7.8E-9
*SOLID SECTION, ELSET=EALL, MATERIAL=STEEL
*BOUNDARY
Z0, 1, 3
*STEP
*BUCKLE
1
*CLOAD
TOP, 3, -1.
*END STEP

```

The elastic twin `elastic_buckle.inp` is the same deck without the two `*PLASTIC` data lines and the `*PLASTIC` card.

> **Other cases: replace the \*STEP ... \*END STEP block of plastic\_buckle.inp with one of these**
>
> `steps_na.inp`:
> 
> ```auto
> *STEP
> *NO ANALYSIS
> *END STEP
> 
> ```
> 
> `steps_static_na.inp`:
> 
> ```auto
> *STEP
> *STATIC
> *CLOAD
> TOP, 3, -1.
> *END STEP
> *STEP
> *NO ANALYSIS
> *END STEP
> 
> ```
> 
> `steps_static_buckle.inp`:
> 
> ```auto
> *STEP
> *STATIC
> *CLOAD
> TOP, 3, -1.
> *END STEP
> *STEP
> *BUCKLE
> 1
> *CLOAD
> TOP, 3, -1.
> *END STEP
> 
> ```
> 
> `steps_freq.inp`:
> 
> ```auto
> *STEP
> *FREQUENCY
> 2
> *END STEP
> 
> ```
> 
> `steps_freq_static.inp`:
> 
> ```auto
> *STEP
> *FREQUENCY
> 2
> *END STEP
> *STEP
> *STATIC
> *CLOAD
> TOP, 3, -1.
> *END STEP
> 
> ```
> 
> `steps_static_pert.inp`:
> 
> ```auto
> *STEP
> *STATIC
> *CLOAD
> TOP, 3, -1.
> *END STEP
> *STEP, PERTURBATION
> *STATIC
> *CLOAD
> TOP, 3, -2.
> *END STEP
> 
> ```
> 
> `steps_md_u.inp` (`steps_md_s.inp`: `*EL FILE` / `S` instead of `*NODE FILE` / `U`; `steps_md_rf.inp`: `*NODE PRINT, NSET=Z0` / `RF` instead):
> 
> ```auto
> *STEP
> *FREQUENCY, STORAGE=YES
> 2
> *END STEP
> *STEP
> *MODAL DYNAMIC
> 0.001, 0.01
> *CLOAD
> 7, 1, 1.
> *NODE FILE
> U
> *END STEP
> 
> ```
> 
> `steps_ssd_u.inp` (`steps_ssd_s.inp`: `*EL FILE` / `S` instead; `steps_ssd_rf.inp`: `*NODE FILE` / `U, RF` instead):
> 
> ```auto
> *STEP
> *FREQUENCY, STORAGE=YES
> 2
> *END STEP
> *STEP
> *STEADY STATE DYNAMICS
> 10., 1000., 3
> *CLOAD
> 7, 1, 1.
> *NODE FILE
> U
> *END STEP
> 
> ```
> 
> `steps_cf.inp`:
> 
> ```auto
> *STEP
> *FREQUENCY, STORAGE=YES
> 4
> *DLOAD
> EALL, CENTRIF, 1.E4, 0., 0., 0., 0., 0., 1.
> *END STEP
> *STEP
> *COMPLEX FREQUENCY, CORIOLIS
> 2
> *DLOAD
> EALL, CENTRIF, 1.E4, 0., 0., 0., 0., 0., 1.
> *END STEP
> 
> ```
> 
> `steps_freq_visco.inp` (with `*CREEP, LAW=TIME` / `1.E-12, 1., 0.` in place of the `*PLASTIC` lines):
> 
> ```auto
> *STEP
> *FREQUENCY
> 2
> *END STEP
> *STEP
> *VISCO, CETOL=1.E-3
> 0.1, 1.
> *CLOAD
> TOP, 3, -1.
> *END STEP
> 
> ```
> 
> Other materials, in place of the three `*PLASTIC` lines (the user material is ccx’s built-in `LIN_ISO_EL`, linear elastic):
> 
> ```auto
> *PLASTIC, HARDENING=KINEMATIC / 250., 0. / 300., 0.1
> *CREEP, LAW=TIME / 1.E-12, 1., 0.
> *MOHR COULOMB / 30., 0. / *MOHR COULOMB HARDENING / 100., 0.
> *DEFORMATION PLASTICITY / 210000., 0.3, 250., 10., 0.3
> *DEPVAR / 2
> *HYPERELASTIC, NEO HOOKE / 80000., 1.E-5
> user material: *MATERIAL, NAME=LIN_ISO_EL / *USER MATERIAL, CONSTANTS=2 / 210000., 0.3
> (no *ELASTIC card; *SOLID SECTION ... MATERIAL=LIN_ISO_EL)
> 
> ```
> 
> `contact_md.inp`: the plastic cube with an elastic block pressed on it (node-to-surface contact), a static step, a frequency step and a modal dynamic step with contact output. `TYPE=SURFACE TO SURFACE` crashes the same way.
> 
> ```auto
> *NODE
> 1, 0., 0., 0.
> 2, 1., 0., 0.
> 3, 1., 1., 0.
> 4, 0., 1., 0.
> 5, 0., 0., 1.
> 6, 1., 0., 1.
> 7, 1., 1., 1.
> 8, 0., 1., 1.
> 9, 0., 0., 1.
> 10, 1., 0., 1.
> 11, 1., 1., 1.
> 12, 0., 1., 1.
> 13, 0., 0., 2.
> 14, 1., 0., 2.
> 15, 1., 1., 2.
> 16, 0., 1., 2.
> *ELEMENT, TYPE=C3D8, ELSET=COL
> 1, 1, 2, 3, 4, 5, 6, 7, 8
> *ELEMENT, TYPE=C3D8, ELSET=BLK
> 2, 9, 10, 11, 12, 13, 14, 15, 16
> *NSET, NSET=Z0
> 1, 2, 3, 4
> *NSET, NSET=BTOP
> 13, 14, 15, 16
> *MATERIAL, NAME=STEEL
> *ELASTIC
> 210000., 0.3
> *PLASTIC
> 250., 0.
> 300., 0.1
> *DENSITY
> 7.8E-9
> *MATERIAL, NAME=EL
> *ELASTIC
> 210000., 0.3
> *DENSITY
> 7.8E-9
> *SOLID SECTION, ELSET=COL, MATERIAL=STEEL
> *SOLID SECTION, ELSET=BLK, MATERIAL=EL
> *SURFACE, NAME=COLTOP
> COL, S2
> *SURFACE, NAME=BLKBOT
> BLK, S1
> *SURFACE INTERACTION, NAME=INT
> *SURFACE BEHAVIOR, PRESSURE-OVERCLOSURE=LINEAR
> 1.E6
> *CONTACT PAIR, INTERACTION=INT, TYPE=NODE TO SURFACE
> BLKBOT, COLTOP
> *BOUNDARY
> Z0, 1, 3
> BTOP, 1, 2
> *STEP
> *STATIC
> *CLOAD
> BTOP, 3, -10.
> *END STEP
> *STEP
> *FREQUENCY, STORAGE=YES
> 2
> *END STEP
> *STEP
> *MODAL DYNAMIC
> 0.001, 0.01
> *CLOAD
> 15, 1, 1.
> *CONTACT FILE
> CDIS
> *END STEP
> 
> ```

## How to run

`ccx plastic_buckle`; for the other cases, build the deck from the model part of `plastic_buckle.inp` and a steps block, then run it the same way.

## Expected

The deck finishes with exit status 0, as the elastic twins do. `elastic_buckle.inp` prints the buckling factor 0.1122004E+05. In these steps the cube stays elastic: under the same load in a static step, the largest stress component is 4.5, against a yield stress of 250. Where ccx cannot handle the material in a step, the intended way to stop is an `*ERROR` message.

## Actual

`ccx plastic_buckle` prints:

```auto
 STEP 1

 Buckling analysis was selected

 Decascading the MPC's

 Determining the structure of the matrix:
 Using up to 1 cpu(s) for setting up the structure of the matrix.
 number of equations
 12
 number of nonzero lower triangular matrix elements
 66

 Using up to 1 cpu(s) for the stress calculation.

```

and is then killed by SIGSEGV (exit status 139). There is no message, and the .dat file is empty.

Per case (plastic cube, exit status; elastic twin; the procedure routine in the backtrace):

| steps | `*PLASTIC` | elastic | crash in |
| --- | --- | --- | --- |
| `*NO ANALYSIS` | 139 | 0 | linstatic |
| `*STATIC`, `*NO ANALYSIS` | 139 | 0 | linstatic |
| `*BUCKLE` | 139 | 0 | arpackbu |
| `*STATIC`, `*BUCKLE` | 139 | 0 | arpackbu |
| `*FREQUENCY` | 0 | 0 | |
| `*FREQUENCY`, `*STATIC` | 139 | 0 | linstatic |
| `*STATIC`, `*STEP, PERTURBATION` `*STATIC` | 139 | 0 | linstatic |
| `*FREQUENCY`, `*VISCO` (`*CREEP`) | 139 | 0 | linstatic |
| `*FREQUENCY`, `*MODAL DYNAMIC` with `*NODE FILE` U | 0 | 0 | |
| same with `*EL FILE` S | 139 | 0 | dyna |
| same with `*NODE PRINT` RF | 139 | 0 | dyna |
| `*FREQUENCY`, `*STEADY STATE DYNAMICS` with `*NODE FILE` U | 0 | 0 | |
| same with `*EL FILE` S | 139 | 0 | steadystate |
| same with `*NODE FILE` U, RF | 139 | 0 | steadystate |
| `*FREQUENCY`, `*COMPLEX FREQUENCY, CORIOLIS` | 139 | 0 | complexfreq |
| contact: `*STATIC`, `*FREQUENCY`, `*MODAL DYNAMIC` with `*CONTACT FILE` CDIS | 139 | 0 | dyna |
| same with `*CONTACT PRINT` CSTR | 139 | 0 | dyna |
| same as `*STEADY STATE DYNAMICS` with `*CONTACT FILE` CDIS | 139 | 0 | steadystate |

Per material (exit status):

| material | `*NO ANALYSIS` | `*BUCKLE` | `*FREQUENCY`, `*STATIC` |
| --- | --- | --- | --- |
| `*PLASTIC` (isotropic or kinematic) | 139 | 139 | 139 |
| `*CREEP` | 139 | 139 | 139 |
| `*MOHR COULOMB` | 139 | 139 | 139 |
| `*DEFORMATION PLASTICITY` | 139 | 139 | 201 (1) |
| `*USER MATERIAL` (`LIN_ISO_EL`) | 139 | 0 | 139 |
| elastic, elastic + `*DEPVAR`, `*HYPERELASTIC` | 0 | 0 | 0 |

(1) The `*FREQUENCY` step stops first, with “\*ERROR in umat\_abaqusnl: negative eigenvalue of the Cauchy-Green tensor”. That is a different problem (reported separately).

The plastic material crashes in `incplas_lin` reading address 0x0 (`epini=xstateini(1,iint,iel)`, `incplas_lin.f` line 72). Mohr-Coulomb crashes in `mohrcoulomb`, and deformation plasticity in `umat_abaqusnl_total` (copying `xstateini` into `xstate`). The user material crashes in `resultsmech` reading `vini` (address 0x8) or `stiini` (address 0x0 in `dyna`).

## Where it goes wrong

The material cards switch the model to nonlinear: `plastics.f` line 73 sets `iperturb(1)=3`, and so do `creeps.f`, `mohrcoulombs.f`, `deformationplasticitys.f` and `usermaterials.f`. The perturbation-type cards switch it back for the rest of the analysis:

```fortran
      if(iperturb(1).gt.1) iperturb(1)=0 ! frequencys.f:165, buckles.f:117, complexfrequencys.f:94
      iperturb(1)=0 ! noanalysiss.f:45

```

`CalculiX.c` (lines 1249-1264) sends a `*STATIC` or `*NO ANALYSIS` step with `iperturb[0]<2` to `linstatic()`. `*BUCKLE` goes to `arpackbu()`. After the frequency step, `*MODAL DYNAMIC`, `*STEADY STATE DYNAMICS` and `*COMPLEX FREQUENCY` go to `dyna()`, `steadystate()` and `complexfreq()`. All of these call `results()`, which still evaluates the plastic, creep or user material through `mechmodel` → `incplas_lin` / `mohrcoulomb` / `umat_abaqusnl_total` / `umat_main`. Those routines read the state at the start of the increment from `xstateini`, and user materials also read `vini`, `stiini` and `emeini` in `resultsmech.f` (lines 793, 823, 929).

`arpack.c` allocates the field before its `results()` calls (lines 367-375):

```c
  /* field for initial values of state variables (needed if
     previous static step was viscoplastic and for contact */

  if((*nstate_!=0)&&((*mortar==0)||(ncont==0))){
    NNEW(xstateini,double,*nstate_*mi[0]*(ne0+*nslavs));

```

`linstatic.c` has the same lines (301-308), but only inside `if(*mortar>-2){` (line 176), i.e. only in a model with contact. Without contact `xstateini` stays NULL (line 98). Its first `results()` call (line 351) also passes `vini` (never allocated) and `stiini` / `emeini` (allocated at lines 574-575 only for energy output). `arpackbu.c` allocates the user-material fields, with the comment “following fields are needed if \*ener==1 or kode\<-100” (lines 150-156), but not `xstateini`. `dyna.c`, `steadystate.c` and `complexfreq.c` have no `NNEW(xstateini, ...)` at all. Their `results()` calls run only for stress, strain, RF or contact output in `dyna.c` (line 1785) and `steadystate.c`, but every time in `complexfreq.c` (line 1462) and `arpackbu.c` (line 161). That is why the modal dynamic and steady state dynamics steps need such output to crash.

## Fix

Allocate `xstateini` as a copy of `xstate` whenever `*nstate_!=0` in `linstatic.c`, `arpackbu.c`, `dyna.c`, `steadystate.c` and `complexfreq.c`, before their first `results()` call, as `arpack.c` lines 370-375 do, and free it at the end. In `linstatic.c` that means moving the existing block (lines 301-308) out of `if(*mortar>-2){`. In addition, allocate `vini`, `stiini` and `emeini` unconditionally where they are now missing or tied to `*nener==1` (`linstatic.c`, `dyna.c`, `steadystate.c`, `complexfreq.c`), as `arpackbu.c` does at lines 150-156.

This should remove the crashes (not built or tested here). One thing would stay the same: after a `*FREQUENCY`, `*BUCKLE` or `*NO ANALYSIS` step, a later `*STATIC` step of such a model is still solved by `linstatic()`, in one linear solve, because no step card sets `iperturb(1)` back.

Workaround: put NLGEOM on the `*STEP` card of a `*STATIC` step that follows a perturbation step. This sends the step back to `nonlingeo()`, and `*FREQUENCY`, then `*STEP, NLGEOM` `*STATIC` runs. In `*MODAL DYNAMIC` and `*STEADY STATE DYNAMICS` steps, request displacements only. There is no workaround for `*BUCKLE`, `*COMPLEX FREQUENCY` or `*NO ANALYSIS` with these materials.

---

<div class="post-metadata">

**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 23, 2026, 5:31am UTC](https://calculix.discourse.group/t/plastic-creep-or-user-material-segfault-in-no-analysis-buckle-complex-frequency-a-linear-static-after-frequency-and-modal-steps-with-s-rf-output/4243/2 "2026-10-23T05:31:00Z")

</div>

Confirmed using official build of ccx 2.23 on Windows, needs a GitHub ticket.

plastic\_buckle:

```auto
 STEP 1

 Buckling analysis was selected

 Decascading the MPC's

 Determining the structure of the matrix:
 Using up to 12 cpu(s) for setting up the structure of the matrix.
 number of equations
 12
 number of nonzero lower triangular matrix elements
 66

 Using up to 1 cpu(s) for the stress calculation.

```

---

<div class="post-metadata">

**Author:** ![Sandervdb](https://avatars.discourse-cdn.com/v4/letter/s/49beb7/32.png) [@Sandervdb](https://calculix.discourse.group/u/Sandervdb)\
**Post date:** [October 23, 2026, 5:32am UTC](https://calculix.discourse.group/t/plastic-creep-or-user-material-segfault-in-no-analysis-buckle-complex-frequency-a-linear-static-after-frequency-and-modal-steps-with-s-rf-output/4243/3 "2026-10-23T05:32:25Z")

</div>

posted: [Plastic, creep or user material: segfault in \*NO ANALYSIS, \*BUCKLE, \*COMPLEX FREQUENCY, a linear \*STATIC after \*FREQUENCY, and modal steps with S/RF output · Issue #285 · Dhondtguido/CalculiX · GitHub](https://github.com/Dhondtguido/CalculiX/issues/285)