How to define the properties of temperature-dependent materials

Christos_Sakkoulas · February 12

Materials whose properties vary with temperature are crucial in various fields like electronics, engineering, and materials science. Understanding the temperature dependency of materials is essential for designing reliable systems and devices that operate under varying thermal conditions.

Temperature can have various effects on materials, influencing their physical, chemical, and mechanical properties. For example, metals generally become softer and more ductile at higher temperatures, while ceramics may become more brittle. Changes in temperature can also affect materials' strength, stiffness, and fatigue resistance.

Material Classifications

The following table presents the classification of the materials and the corresponding OptiStruct cards.

Figure 1 Material Classification

Temperature dependent material properties are defined using MATT1, MATT2, MATT8, and MATT9. All four have the same characteristics as described in the table above. The temperature dependency of each property is defined through TABLEM1, TABLEM2, TABLEM3, or TABLEM4 table entries.

Material properties definition

For the methodology explanation the MAT1 card was selected to be used. This card defines the material properties for linear, temperature-independent, and isotropic materials.

Some Key Parameters of the MAT1 card:

E: Modulus of Elasticity

G: Modulus of Rigidity
NU: Poisson's Ratio
RHO: Density

For this example, the following properties were defined:

Figure 2 MAT1 Card

The strength of materials generally decreases with increasing temperature. This is particularly noticeable in metals, where elevated temperatures can lead to a phenomenon called "thermal softening." At higher temperatures, atomic vibrations become more pronounced, causing dislocations to move more easily, which in turn leads to reduced strength. In order to capture this phenomenon, the MATS1 option needs to be enabled. MATS1 is defined as an extension to a MAT1 with the same MID. MATS1 is applicable to all nonlinear solutions. This card specifies strain-rate, and temperature-dependent material properties for use in applications involving nonlinear materials. The nonlinear material characteristics may need the table input TABLES1. For this reason, five stress-strain curves were created for five different temperatures.

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Figure 3 Stress-Strain Curves

For these five curves to be referenced by the MATS1 entry, a TABLEST has to be created that contains all of the above curves.

Figure 4 TABLEST Curve

Then the material card looks like this:

Figure 5 MAT1 Card with MATS1 Option Checked

Temperature dependent material properties

In order to define the temperature dependent material properties, the MATT1 option needs to be enabled. This option specifies these properties on MAT1 entry fields via TABLEMi or TABLEG entry.

Some Key Parameters of the MATT1 card:

T(E) - Young's modulus.
T(G) - shear modulus.
T(NU) - Poisson's ratio.
T(RHO) - mass density.
T(A) - thermal expansion coefficient.
T(GE) - damping coefficient.
T(ST) - tension stress limit.
T(SC) - compression limit.
T(SS) - shear limit.

The temperature dependency of each property is defined through TABLEM1, TABLEM2, TABLEM3, or TABLEM4 table entries. For this reason, three TABLEM1 curves were created to provide the temperature dependency of the Elastic modulus, the Poisson’s ratio and the thermal’s expansion.

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Figure 6 Poisson's Ratio Curve

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Figure 7 Young's Modulus Curve

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Figure 8 Thermal’s Expansion Curve

This article was authored from Robinson Ferrari and Christos Sakkoulas

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How to define the properties of temperature-dependent materials

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