Mechanical APDL Basic Analysis Guide - Ansys

You can choose constant, isotropic, linear material properties from a material library available through the
GUI. Young's modulus, density, coefficient of thermal expansion, Poisson's ratio, thermal conductivity and
specific heat are available for 10 materials in four unit systems.
Caution
The property values in the material library are provided for your convenience. They are typical
values for the materials you can use for preliminary analyses and noncritical applications. As always,
you are responsible for all data input to the ANSYS program.
To define temperature-dependent material properties, you can use the MP command in combination with
the MPTEMP or MPTGEN command. You also can use the MPTEMP and MPDATA commands. The MP
command allows you to define a property-versus-temperature function in the form of a polynomial. The
polynomial may be linear, quadratic, cubic, or quartic:
Property = C 0 + C 1T + C 2T 2 + C 3T 3 + C 4T 4
C n are the coefficients and T is the temperature. You enter the coefficients using the C0, C1, C2, C3, and C4
arguments on the MP command. If you specify just C0, the material property is constant; if you specify C0
and C1, the material property varies linearly with temperature; and so on. When you specify a temperaturedependent
property in this manner, the program internally evaluates the polynomial at discrete temperature
points with linear interpolation between points (that is, piecewise linear representation) and a constantvalued
extrapolation beyond the extreme points. You must use the MPTEMP or MPTGEN command before
the MP command for second and higher-order properties to define appropriate temperature steps.
The second way to define temperature-dependent material properties is to use a combination of MPTEMP
and MPDATA commands. MPTEMP (or MPTGEN) defines a series of temperatures, and MPDATA defines
corresponding material property values. For example, the following commands define a temperature-dependent
enthalpy for material 4:
MPTEMP,1,1600,1800,2000,2325,2326,2335 ! 6 temperatures (temps 1-6)
MPTEMP,7,2345,2355,2365,2374,2375,3000 ! 6 more temps (temps 7-12)
MPDATA,ENTH,4,1,53.81,61.23,68.83,81.51,81.55,82.31 ! Corresponding
MPDATA,ENTH,4,7,84.48,89.53,99.05,112.12,113.00,137.40 ! enthalpy values
If an unequal number of property data points and temperature data points are defined, the ANSYS program
uses only those locations having both points defined for the property function table. To define a different
set of temperatures for the next material property, you should first erase the current temperature table by
issuing MPTEMP (without any arguments) and then define new temperatures (using additional MPTEMP
or MPTGEN commands).
The MPPLOT command displays a graph of material property versus temperature. Figure 1.1 (p. 6) shows
a plot of the enthalpy-temperature curve defined in the example above. The MPLIST command lists material
properties.
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1.1.4. Defining Material Properties
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