# About heat transfer analysis procedures

 Abaqus can solve several types of heat transfer problems.

Abaqus can solve the following types of heat transfer problems:

Uncoupled heat transfer analysis

Heat transfer problems involving conduction, forced convection, and boundary radiation can be analyzed in Abaqus/Standard. See Uncoupled heat transfer analysis. In these analyses the temperature field is calculated without knowledge of the stress/deformation state or the electrical field in the bodies being studied. Pure heat transfer problems can be transient or steady-state and linear or nonlinear.

Sequentially coupled thermal-stress analysis

If the stress/displacement solution is dependent on a temperature field but there is no inverse dependency, a sequentially coupled thermal-stress analysis can be conducted in Abaqus/Standard. Sequentially coupled thermal-stress analysis is performed by first solving the pure heat transfer problem, then reading the temperature solution into a stress analysis as a predefined field. See Sequentially coupled thermal-stress analysis. In the stress analysis the temperature can vary with time and position but is not changed by the stress analysis solution. Abaqus allows for dissimilar meshes between the heat transfer analysis model and the thermal-stress analysis model. Temperature values will be interpolated based on element interpolators evaluated at nodes of the thermal-stress model.

Fully coupled thermal-stress analysis

A coupled temperature-displacement procedure is used to solve simultaneously for the stress/displacement and the temperature fields. A coupled analysis is used when the thermal and mechanical solutions affect each other strongly. For example, in rapid metalworking problems the inelastic deformation of the material causes heating, and in contact problems the heat conducted across gaps may depend strongly on the gap clearance or pressure.

Both Abaqus/Standard and Abaqus/Explicit provide coupled temperature-displacement analysis procedures, but the algorithms used by each program differ considerably. In Abaqus/Standard the heat transfer equations are integrated using a backward-difference scheme, and the coupled system is solved using Newton's method. These problems can be transient or steady-state and linear or nonlinear. In Abaqus/Explicit the heat transfer equations are integrated using an explicit forward-difference time integration rule, and the mechanical solution response is obtained using an explicit central-difference integration rule. Fully coupled thermal-stress analysis in Abaqus/Explicit is always transient. Cavity radiation effects cannot be included in a fully coupled thermal-stress analysis. See Fully coupled thermal-stress analysis for more details.

Fully coupled thermal-electrical-structural analysis

A coupled thermal-electrical-structural procedure is used to solve simultaneously for the stress/displacement, the electrical potential, and the temperature fields. A coupled analysis is used when the thermal, electrical, and mechanical solutions affect each other strongly. An example of such a process is resistance spot welding, where two or more metal parts are joined by fusion at discrete points at the material interface. The fusion is caused by heat generated due to the current flow at the contact points, which depends on the pressure applied at these points.

These problems can be transient or steady-state and linear or nonlinear. Cavity radiation effects cannot be included in a fully coupled thermal-electrical-structural analysis. This procedure is available only in Abaqus/Standard. See Fully coupled thermal-electrical-structural analysis for more details.