Solid Stress Load Step Solver Reference

In simulations with nonlinear geometry or nonlinear materials, you can improve convergence using the Solid Stress Load Step solver. This solver applies external loads incrementally over several iteration steps in steady simulations, or over several time-steps in unsteady simulations.

Simcenter STAR-CCM+ adds the Solid Stress Load Step solver to the simulation tree when you activate the Load Stepping property for the Solid Stress Solver.

For instructions, see Load Stepping: Applying Loads Progressively.
For the load stepping formulation, see Load Stepping.

Note	The Solid Stress Load Step solver only acts on mechanical loads and has no effect on thermal loads.

Solver Properties

Verbosity: Controls the amount of information that is displayed in the Output window. When set to High, Simcenter STAR-CCM+ prints detailed information on the load stepping progress and the Newton solution update.

Max Newton Steps

Specifies the maximum number of Newton iterations per each load loop. For more information, see Load Stepping.

Max Load Steps

Specifies the number of steps over which the external load is incrementally applied. The load increment that is applied in each step depends on the Load Step Control property.

Load Step Control

Determines the load increment that is applied at each load step. The available options are:

Option	Activated Controls
Static Load Step Control The solver applies the same load increment at each load step. The solver calculates the load increment by deviding the full load value by the specified maximum load steps.	None
Linear Load Step Control At each load step, the solver applies a load increment that is calculated based on convergence of previous load steps.	Solid Stress Load Step > Linear Load Step Control Allows you to specify the Initial Load increment that is applied in the load step and the Optimal Newton Steps that are used to calculate the load increment. At each load step, the solver increments the load linearly based on the current and previous load steps. For more information, see Load Stepping.

Solver Frozen

When On, the solver does not update any quantity during an iteration. It is Off by default. This is a debugging option that can result in non-recoverable errors and wrong solutions due to missing storage. See Finite Volume Solvers Reference for details.

Solver Controls

Stopping Criteria

The Solid Stress Load Step solver has stopping criteria based on the convergence of displacement, force, contact constraint, contact pressure, and strain energy:

Load Step Displacement Criterion
Load Step Force Criterion
Load Step Contact Constraint (only available when you set Contact Constraint Enforcement to Augmented Lagrangian (Uzawa algorithm))
Load Step Contact Pressure (only available when you set Contact Constraint Enforcement to Augmented Lagrangian (Uzawa algorithm))
Load Step Strain energy Criterion (only available when you activate Strain energy on the Solid Stress Solver node).

When you set the solver Verbosity to High Simcenter STAR-CCM+ reports the residual values in the Output window. You can control the normalization of the residual values by setting the Normalization Option of the corresponding Force, Displacement, and Strain energy monitors, under the Monitors node. For more information on the Normalization Option, see Monitor Properties.

When you use the Uzawa algorithm with the Solid Stress Load Step solver, the Uzawa update loop is embedded with the iterations for each load step. All required stopping criteria must be met for the simulation to progress.

Each stopping criterion node has the following properties:

Minimum Value: The minimum value of the residual that satisfies the criterion. The criterion is satisfied when the value of the residual is less than the Minimum Value. The default value is the product between the Multiplier property value and the Minimum Limit that you specify for the corresponding Reference Stopping Criterion.
Use Reference Minimum Value: When activated (default), the Minimum Value is equal to the Minimum Limit of the Reference Stopping Criterion times the Multiplier. When deactivated, you specify the minimum value directly using the Minimum Value property. Specifying a value for the Minimum Value automatically deactivates Use Reference Minimum Value. You can activate Use Reference Minimum Value only when the Criterion Option of the Reference Stopping Criterion is set to Minimum.
Multiplier: The value of the multiplicative factor applied to the Minimum Limit of the Reference Stopping Criterion, to determine the Minimum Value of the Load Step > Stopping Criteria.
Reference Stopping Criterion (read-only): The Stopping Criterion whose Minimum Limit is used as a reference value by the Load Step > Stopping Criteria. The Load Step Displacement Criterion uses Displacement Criterion as the Reference Stopping Criterion, the Load Step Force Criterion uses Force Criterion, and the Load Step Strain energy Criterion uses the Strain energy Criterion.
Criterion Satisfied: Indicates if the stopping criterion has been satisfied (read-only).

For more information on the common properties of stopping criteria, see Using Automatically Generated Stopping Criteria.