Material properties (which may be functions of temperature) are described as linear properties because most nonthermal analyses with those properties require only a single iteration. Material properties for a single-solution analysis are typically input via the MP command.

If properties needed for a thermal analysis (such as KXX) are temperature-dependent, the problem is considered to be nonlinear. Properties such as stress-strain data are nonlinear because an analysis with these properties requires an iterative solution.

Linear material properties required by an element but that remain undefined use default values. (Exceptions are EX and KXX, which must be input with a nonzero value where applicable.) The program ignores any additional material properties.

The X, Y, and Z portions of the material property labels refer to the element coordinate system. In general, if a material is isotropic, only the X and possibly the XY term are input.