# compute smd/ulsph/stress command

## Syntax

``` LAMMPS
compute ID group-ID smd/ulsph/stress
```

-   ID, group-ID are documented in [compute](compute) command
-   smd/ulsph/stress = style name of this compute command

## Examples

``` LAMMPS
compute 1 all smd/ulsph/stress
```

## Description

Define a computation that outputs the Cauchy stress tensor.

See [this PDF guide](PDF/MACHDYN_LAMMPS_userguide.pdf)\_ to using Smooth
Mach Dynamics in LAMMPS.

## Output info

This compute calculates a per-particle vector of vectors (tensors),
which can be accessed by any command that uses per-particle values from
a compute as input. See the [Howto output](Howto_output) doc page for an
overview of LAMMPS output options.

The values will be given in [units](units) of pressure.

The per-particle vector has 7 entries. The first six entries correspond
to the xx, yy, zz, xy, xz, yz components of the symmetric Cauchy stress
tensor. The seventh entry is the second invariant of the stress tensor,
i.e., the von Mises equivalent stress.

## Restrictions

This compute is part of the MACHDYN package. It is only enabled if
LAMMPS was built with that package. See the [Build
package](Build_package) page for more info. This compute can only be
used for particles which interact with the updated Lagrangian SPH pair
style.

## Related commands

[compute smd/ulsph/strain](compute_smd_ulsph_strain), [compute
smd/ulsph/strain/rate](compute_smd_ulsph_strain_rate) [compute
smd/tlsph/stress](compute_smd_tlsph_stress)

## Default

none