TEMPERATURE

Format

TEMPERATURE (type, SUBTYPE=subtype_option) = option

Examples

TEMPERATURE(LOAD)=15
TEMP(MATERIAL)=7
TEMPERATURE=7
TEMPERATURE(LOAD,HTIME=ALL)=8
TEMPERATURE(LOAD,TEMPT)=23

Definitions

Comments

1. The total load applied will be the sum of external (LOAD command), thermal (TEMP(LOAD/BOTH) command) and constrained displacement (SPC command) loads.
2. In Linear static analysis, TEMP(BOTH), TEMP(LOAD), TEMP(MAT), and TEMP(INIT) can be used before the subcase level or inside the subcase. If used before the subcase level, it will apply to all subcases that do not have their own corresponding command. Additionally, only the last instance of TEMP(MAT) and TEMP(INIT) will be used to update the corresponding material or set the initial temperature for all subcases.
3. In Nonlinear Static analysis TEMP(LOAD) and TEMP(INIT) can be used before the subcase level or inside the subcase. If used before the subcase level, it will apply to all subcases that do not have their corresponding command. Additionally, only the last instance of TEMP(INIT) will be used to the set the initial temperature or material properties (if TEMP(LOAD) is not present) for all subcases.
4. Only one of TEMP(MAT) or TEMP(INIT) is allowed in any model. TEMP(MAT), TEMP(LOAD), and TEMP(BOTH) can point to a heat transfer subcase or TEMP/TEMPD. TEMP(INIT) cannot be used to reference a Heat Transfer Subcase.
5. Static and thermal loads should have unique set identification numbers.
6. In linear static analysis, temperature strains and material properties are calculated as: 2(1)
   $${\epsilon }_T=A(T)\hspace{0.17em}(T_{Final}-T_{Initial})$$

   Material properties are also calculated based on their corresponding temperature-dependency (wherever applicable).

   Where,

   • $A(T_{Final})$ is the thermal expansion coefficient. The value of $A(T_{Final})$ and temperature-dependent material properties can be defined via the MATi or MATTi Bulk Data Entries depending on whether temperature-dependent material are used. Temperature-dependent material are used if TEMP(BOTH), TEMP(MAT), or TEMP(INIT) are specified in conjunction with MATTi entries. If more than one or all three of TEMP(BOTH/MAT/INIT) are specified, then OptiStruct picks one of them for material update based on the following priority.

     TEMP(BOTH/MAT) have precedence over TEMP(INIT). If both TEMP(BOTH) and TEMP(MAT) are present, then the last one is used for material update.

     If none of TEMP(BOTH/MAT/INIT) are specified, then the MATi material properties are used.

   • $T_{Final}$ is the load temperature defined by TEMP(LOAD) or TEMP(BOTH). If both TEMP(BOTH) and TEMP(LOAD) are present, then OptiStruct picks the last one for the load temperature. TEMP(BOTH) and TEMP(LOAD) can be specified within the subcase in multiple subcases. In such situations, the load temperature can vary for each subcase depending on the entries specified within, and as mentioned previously, the last entry in each subcase will determine the load temperature for that particular subcase.
   • $T_{Initial}$ is the initial temperature defined by TEMP(INIT) or TREF (TREF field on MATi). TEMP(INIT) has precedence over TREF. If TEMP(INIT) is not specified, then TREF is used for the initial temperature.
   • SYSSETTING, TLOADMAT can be used to activate TEMP(LOAD) for material update instead of TEMP(MAT/INIT). It can also be used to deactivate thermal loading in structural analysis.
7. In nonlinear static analysis, temperature strains and material properties are calculated as: 3
   If PARAM, THMLSTN, 0 (Default)(2)

   $${\epsilon }_T=A\left(T_{Final}\right)\left(T_{Final}-T_{Initial}\right)$$
   Or, if PARAM, THMLSTN, 1(3)

   $${\epsilon }_T=A\left(T_{Final}\right)\left(T_{Final}-T_{Ref}\right)-A\left(T_{Initial}\right)\left(T_{Initial}-T_{ref}\right)$$

   Material properties are also calculated based on their corresponding temperature-dependency (wherever applicable).

   Where,

   • $A(T_{Final})$ is the thermal expansion coefficient. The value of A(T) and and temperature-dependent material properties can be defined via the MATi or MATTi Bulk Data Entries depending on whether temperature-dependent material are used. Temperature-dependent material is used if TEMP(LOAD) is specified in conjunction with MATTi entries. If TEMP(LOAD) is not specified, then TEMP(INIT) is used. If neither TEMP(LOAD) or TEMP(INIT) are specified then the MATi material properties are used.
   • $T_{Final}$ is the load temperature defined by TEMP(LOAD). TEMP(LOAD) can be specified within the subcase in multiple subcases. In such situations, the load temperature can vary for each subcase depending on the entries specified within, and the last entry in each subcase will determine the load temperature for that particular subcase.
   • $T_{Initial}$ is the initial temperature defined by TEMP(INIT), TREF (TREF field on MATi), or TEMPT entry. TEMP(INIT) has precedence over TREF and TEMPT entry. If TEMP(INIT) is not specified:
     • In a model with subcase continuation, the initial temperature is determined by the first subcase in the series. The determination follows the following rules.
       • For nonlinear static subcases with TEMP(LOAD,TEMPT), the temperature field corresponding to HTINI defined in the TEMPT entry is used as the initial temperature field.
       • If TEMPT format is not used, then TREF is used for the initial temperature.
     • Otherwise, TREF is used for the intial temperature.
   • TEMP(MAT), TEMP(BOTH) cannot be used in Nonlinear Static Analysis subcases. OptiStruct will error out, if they are specified inside Nonlinear Static Analysis subcases. If TEMP(MAT) or TEMP(BOTH) are specified outside Nonlinear Static Subcases (either globally or in subcases of other solution sequences), then TEMP(LOAD) should be defined inside the Nonlinear Static Subcases in the model.
8. In versions prior to OptiStruct 8.0, thermal loads were selected in the Subcase Information section using the LOAD data selector. In version 8.0, the TEMPERATURE data selector was added to perform this function. It is possible to revert to the old behavior mode by setting the LOADTEMP option to SHAREID in the Configuration File.
9. For Linear Static Subcase, TEMP(LOAD), TEMP(BOTH), or TEMP(MAT) can point to a heat transfer subcase or TSTRU ID. The temperature field from a steady-state heat transfer analysis or at the final time step of a transient heat transfer analysis will be used. When TEMP(LOAD) or TEMP(BOTH) points to a transient heat transfer subcase or TSTRU ID, TIME= ALL can be used to select temperature fields at all time steps for coupled thermal structural analysis. HTIME= ALL cannot be defined in TEMP(INIT) or TEMP(MAT) entry. For more information, refer to One Step Transient Thermal Stress Analysis.
10. For Nonlinear Static Subcase, TEMP(LOAD) can point to heat transfer subcase. The temperature field from a steady-state heat transfer analysis will be used to update thermal loading and temperature-dependent material properties. If TEMP(LOAD) points to transient thermal subcase from Nonlinear Static Subcase, then HTIME= ALL can be used to select temperature fields at all time steps for coupled thermal structural analysis. HTIME=ALL cannot be defined in the TEMP(INIT) entry. For more information, refer to One Step Transient Thermal Stress Analysis.
11. For Nonlinear One Step Transient Thermal Stress Analysis, a more flexible definition on thermal load can be used by the combination of TEMP(LOAD) and flag TEMPT. In this format, the thermal load can be read from either an external file (HFILE) or an internal transient thermal analysis (HSUB). In this case, grid temperature values at different time steps are predefined and mapped to the current nonlinear structural analysis. The mapping rule is defined in TEMPT card. The referenced TEMPT card ID is defined in SUBTYPE.
12. In nonlinear analysis, the thermal expansion coefficient $A\left(T\right)$ is a secant value. You can obtain its value from the instantaneous thermal expansion coefficient using:(4)
    $$A\left(T\right)=\frac{1}{\left(T-T_{ini}\right)}{\displaystyle \underset{T_{ini}}{\overset{T}{\int }}\alpha \left(T\right)dT}$$
    Where,

    $T_{ini}$

    Initial temperature.

    $\alpha \left(T\right)$

    Instantaneous thermal expansion coefficient.

    $A\left(T\right)$

    Secant thermal expansion coefficient at temperature $T$ . This is used by OptiStruct.

    When PARAM,THMLSTN,1 is specified, the secant thermal expansion coefficient can be obtained by:(5)

    $$A\left(T\right)=\frac{1}{\left(T-T_{ref}\right)}{\displaystyle \underset{T_{ini}}{\overset{T}{\int }}\alpha \left(T\right)dT}+A\left(T_{ini}\right)\frac{T_{ini}-T_{ref}}{T-T_{ref}}$$

    Where, $T_{ref}$ is the reference temperature defined on the material entry.

    For the initial state, the secant thermal expansion coefficient, $A\left(T_{ini}\right)=\alpha \left(T_{ini}\right)$ .

13. If an initial temperature (predefined outside of the subcases) is different from the temperature at the very beginning of a subcase and the resulting thermal expansion is nonzero, the thermal strain due to this temperature difference is counted.