3.5.14.1. STATIC-STRESS branch

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The static-stress step can be used to compute the deformation response of the model under applied loads and boundary conditions. The inertia of the model is not taken into account. Let's discuss how to set up a static-stress resolution step.

In order to define a static-stress resolution step, you first need to specify the following parameters:

• The NAME of the step, used to identify the step during post-processing.
• The number of level (NB-LEVELS) that you want to impose for this resolution.
• The TIME-PERIOD of the step. Event though this step consist of a static analysis, SesamX uses this time-period to label each level computed. Modifying the time-period will not affect the resolution itself. By default, the time-period for a static-stress step is $1 s$.

Then, you need to provide the loading case and the constraint case. You can define multiple loading and constraint cases that work in an additive manner (LOADS and CONSTRAINTS branches). For each loading or constraint case, you must provide the NAME of the underlying load or constraint object, and its amplitude variation during the step (AMPLITUDE-FUNCTION keyword). The amplitude function must be a function of time (t), relative to the beginning of the step. For instance, let's assume that the step time-period is $1 s$:

• To define a constant amplitude we can use AMPLITUDE-FUNCTION: 1,
• To define a increasing ramp amplitude we can use AMPLITUDE-FUNCTION: t,
• To define a decreasing ramp amplitude we can use AMPLITUDE-FUNCTION: 1-t,
• To define a sinusoidal amplitude we can use AMPLITUDE-FUNCTION: sin(t).

To take into account contact conditions during the step resolution, you need also to provide the contact case through the CONTACT keyword. Unlike the loads and the constraints, only one contact case can be used, and no amplitude applies on it.

As discussed in the SOLVE function page, in non-linear analysis you need to define how the iterative resolution procedure must behave.

The most important set of parameters are the convergence criteria (CVG-CRITERIA branch). In SesamX, the convergence criteria are composed of the following parameters:

• MAX-FORCE: the maximum residual force allowed at each translational degree of freedom,
• MAX-MOMENT: the maximum residual moment allowed at each rotational degree of freedom,
• MAX-TRANSLATION: the maximum residual translation allowed at each translational kinematic relation.
• MAX-ROTATION: the maximum residual rotation allowed at each rotational kinematic relation.
• MAX-CONTACT-PENETRATION: the maximum penetration allowed for each contact condition.
• MAX-NB-ITERATIONS: the maximum number of iterations allowed (during a level) before the solver stops iterating.

SesamX defines a default value for each of these parameters, you can then omit to define them. However, as the convergence criteria tells when the solution is converged or not, you should always pay attention to the convergence criteria values you provide. Depending on the analysis some of these parameters may not be used during the resolution. For instance, if you do not provide a contact case, there is no need to define the MAX-CONTACT-PENETRATION parameter.

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Inside this branch, a list of NAME and AMPLITUDE-FUNCTION keywords is expected, as showcase in the following example.

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Inside this branch, a list of NAME and AMPLITUDE-FUNCTION keywords is expected, as showcase in the following example.

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STATIC-STRESS
  NAME: LOADING
  NB-LEVELS: 10
  CONSTRAINTS
    - NAME: BOUND_CASE  AMPLITUDE-FUNCTION: "1"
  LOADS
    - NAME: LOAD_CASE  AMPLITUDE-FUNCTION: "t."
  CONTACT: CONTACT_CASE

• SesamX SOLVE function

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