Four states, not one button

Mental model — Four states, not one button

Do not treat solving as merely flipping a switch. The process contains four different states:

1. Prepared database: mesh, properties, constraints and loads.
2. Solution definition: type of analysis, increments and results requested.
3. Solution: MAPDL assembles and solves the system of equations.
4. Active set: a specific state of the results file is loaded into memory.

Physics — What does “linear static” mean?

The adjective contains three decisions:

• Structural: we seek displacements and forces that satisfy equilibrium and compatibility.
• Static: we do not include inertial terms or a physical time history.
• Linear: stiffness, geometry, and constitutive behavior do not change with the response.

The idealized system can be expressed as:

[K]{u} = {F}

Therefore, if we double the load without changing the model, displacements, reactions, and stresses must double. The challenge will use that proportionality as a second check.

APDL — State the hypothesis

/SOLU
ANTYPE,STATIC
NLGEOM,OFF
KBC,1
NSUBST,1
OUTRES,ALL,LAST

• ANTYPE,STATIC selects a static analysis.
• NLGEOM,OFF makes linear geometry explicit.
• KBC,1 applies the load stepwise in the single substep.
• NSUBST,1 defines a single substep for this linear case.
• OUTRES,ALL,LAST saves the requested final state.

Some options match the defaults. Writing them here is not padding; it turns the lesson assumptions into reviewable text.

Load step, substep and set

Load step

The load state to solve. It may represent a physical phase or a different condition.

Substep

Numerical increment within a load step. In nonlinear analysis it will have a decisive role.

Result set

Snapshot stored in the results file and recoverable later.

They are not synonyms. A load step can contain many substeps and not all of them have to have been written as sets.