The Solid Mechanics (solid) interface (
), found under the
Structural Mechanics branch (
) when adding a physics interface, is intended for general structural analysis of 3D, 2D, or axisymmetric bodies. In 2D, plane stress, plane strain, or generalized plane strain assumptions can be used. The Solid Mechanics interface is based on solving the equations of motion together with a constitutive model for a solid material. Results such as displacements, stresses, and strains are computed.
The default material is a Linear Elastic Material. With either the Nonlinear Structural Materials Module or the Geomechanics Module, the physics interface is extended with more materials, for example, material models for plasticity, hyperelasticity, creep, and concrete. You can also add your own material models using an
External Stress-Strain Relation
When this physics interface is added, these default nodes are also added to the Model Builder —
Linear Elastic Material,
Free (a boundary condition where boundaries are free, with no loads or constraints), and
Initial Values. Then, from the
Physics toolbar, you can add other nodes that implement, for example, solid mechanics material models, boundary conditions, and loads. You can also right-click
Solid Mechanics to select physics features from the context menu.
The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern
<name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the
name string must be unique. Only letters, numbers, and underscores (_) are permitted in the
Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is
solid.
From the Structural transient behavior list, select
Include inertial terms or
Quasi-static. Use
Quasi-static to treat the dynamic behavior as quasi-static (with no mass effects; that is, no second-order time derivatives). Selecting this option gives a more efficient solution for problems where the variation in time is slow when compared to the natural frequencies of the system. The default solver for the time stepping is changed from Generalized alpha to BDF when
Quasi-static is selected.
Enter the coordinates for the Reference point for moment computation xref (variable
refpnt). The resulting moments (applied or as reactions) are then computed relative to this reference point. During the results and analysis stage, the coordinates can be changed in the
Parameters section in the result nodes.
The typical wave speed cref is a parameter for the perfectly matched layers (PMLs) if used in a solid wave propagation model. The default value is
solid.cp, the pressure-wave speed. To use another wave speed, enter a value or expression in the
Typical wave speed for perfectly matched layers field.
In the Solid Mechanics interface you can choose not only the order of the discretization, but also the type of shape functions: Lagrange or
serendipity. For highly distorted elements, Lagrange shape functions provide better accuracy than serendipity shape functions of the same order. The serendipity shape functions will however give significant reductions of the model size for a given mesh containing hexahedral, prism, or quadrilateral elements.
The default is to use Quadratic serendipity shape functions for the
Displacement field. Using
Linear shape functions will give what is sometimes called
constant stress elements. Such a formulation will for many problems make the model overly stiff, and many elements may be needed for an accurate resolution of the stresses.
The physics interface uses the global spatial components of the Displacement field u as dependent variables. The default names for the components are (
u,
v,
w) in 3D. In 2D the component names are (
u,
v), and in 2D axisymmetry they are (
u,
w). You can however not use the “missing” component name in the 2D cases as a parameter or variable name, since it is still used internally.