# One Step Transient Thermal Stress Optimization

One Step Transient Thermal Stress analysis (OSTTS) calculates the displacement and stress history from a transient temperature history.

When optimization response is defined for the OSTTS subcase, internally response is created for each internally spawn static subcases. One Step Transient Thermal Stress Optimization (OSTTO) is carried out based on multiple responses through the time history.

## Input Cards

A linear transient heat transfer subcase and a static subcase should be defined to perform an OSTTS. TEMPERATURE case control entries with the HTIME keyword can be used in the static subcase to select specific or all time steps to perform the stress analysis. To perform OSTTO, objective function or constraints can be defined for OSTTS subcase.

Below is a sample input deck for OSTTO.
SUBCASE 100
TITLE = Transient thermal subcase
ANALYSIS = HEAT
THERMAL(sort1, punch)=ALL
TSTEP = 100
IC = 20
\$
SUBCASE 200
TITLE = One step transient thermal stress subcase
SPC = 1