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.

In the structure, material nonlinearity generates irreversible strain energy, which acts as a heat source. This heat source is used as loading in the thermal analysis. This thermal analysis provides an increment of temperature, and subsequently the heat source can vary at each time increment. The structural material properties can also be temperature dependent.
Note: There is no heat exchange between the system and the environment. Inelastic strain energy is the only heat source in the analysis.


A summary of relevant input file entries for adiabatic analysis.

  1. Heat and structure are coupled at each time step.
  2. 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.
  3. Three dimensional elements and Axisymmetric elements are currently supported.
  4. Some parts of the model are made of elastic material, and other parts are inelastic.
  5. Elasto-plasticity (MATS1), Visco-elasticity (MATVE), and Cohesive elements (MCOHE, MCOHED) are supported for defining inelastic materials for adiabatic analysis.
  6. Cohesive elements only work as a heat source. Heat conduction or specific heat effects are not considered for cohesive elements.
  7. All the elements in a model participate in the structural analysis, but only the elements with thermal material participate in thermal analysis.

Example Subcase

   SPC = 1
   LOAD = 2
   NLPARM = 5
   VISCO = 12
   NLOUT = 10

Input Entries

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

The relevant Subcase Information Entries are:
Table 1. Subcase Information Entries
Entry Purpose
ADIABATIC Activates adiabatic analysis for an implicit nonlinear subcase.
The relevant Bulk Data Entries are:
Table 2. Bulk Data Entries
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.


Supported output requests for adiabatic analysis.

Results are available in both the regular H3D file and the on-the-fly H3D file. The following outputs are available for adiabatic analysis (in addition to the regular nonlinear implicit analysis output):
  • Grid temperature
  • Temperature gradient
  • Heat flux
  • Element heat energy
  • Incremental heat power density (per time, per volume)
  • Total heat power density (per volume)