# Adiabatic Analysis

Adiabatic analysis is a coupled thermal-structural analysis. This analysis is applicable in modeling systems with inelastic strain, which can lead to quick heating of the material without sufficient time for the heat to be transmitted.

## Input

A summary of relevant input file entries for adiabatic analysis.

- Heat and structure are coupled at each time step.
- The adiabatic analysis subcase setup consists of the following.
- The implicit nonlinear subcase. This subcase should be one of:
- Small displacement nonlinear Static analysis
- Large displacement nonlinear Static analysis
- Small displacement nonlinear Transient analysis
- Large displacement nonlinear Transient analysis

- An ADIABATIC Subcase Information Entry should be specified in the implicit nonlinear subcase.

- The implicit nonlinear subcase. This subcase should be one of:
- Three dimensional elements and Axisymmetric elements are currently supported.
- Some parts of the model are made of elastic material, and other parts are inelastic.
- Elasto-plasticity (MATS1), Visco-elasticity (MATVE), and Cohesive elements (MCOHE, MCOHED) are supported for defining inelastic materials for adiabatic analysis.
- Cohesive elements only work as a heat source. Heat conduction or specific heat effects are not considered for cohesive elements.
- All the elements in a model participate in the structural analysis, but only the elements with thermal material participate in thermal analysis.

### Example Subcase

```
SUBCASE 1
ANALYSIS NLSTAT
ADIABATIC
SPC = 1
LOAD = 2
NLPARM = 5
VISCO = 12
NLOUT = 10
```

### Input Entries

The following tables summarize the input entries for an adiabatic analysis.

Entry | Purpose |
---|---|

ADIABATIC | Activates adiabatic analysis for an implicit nonlinear subcase. |

Entry | Purpose |
---|---|

MAT4 | Defines thermal material and INELAHTF
field which is the fraction of inelastic energy converted to
heat source in adiabatic analysis. |

MAT5 | Defines thermal material and INELAHTF
field which is the fraction of inelastic energy converted to
heat source in adiabatic analysis. |

## Output

Supported output requests for adiabatic analysis.

- Grid temperature
- Temperature gradient
- Heat flux
- Element heat energy
- Incremental heat power density (per time, per volume)
- Total heat power density (per volume)