Arc-length corrector methods (Simcenter Samcef)

Classical Newton methods cannot converge when passing a flip point, for example, when the load versus displacement curve has decreasing time steps.

The arc-length method can help to solve such unstable problems. The arc-length method substitutes the arc length controlled variable for time, and adds a new equation to the system of equations in the model.

Riks, Fried, and Crisfield arc-length methods

When you edit a subcase in a nonlinear solution, you can select several arc-length methods and their options: the Riks Arc-Length Method (1), the Fried Arc-Length Method (2), and the Crisfield Arc-Length Method (3).

• In the Riks Arc-Length Method, the tangent predictor vector does not change during the Newton iterations. The corrections follow the original plane that is perpendicular to the initial tangent vector.

• In the Fried Arc-Length Method, the tangent predictor vector is evaluated at each iteration.Each correction follows its own local plane that is perpendicular to the tangent vector computed at the iteration.

• In the Crisfield Arc-Length Method, the tangent predictor vector is evaluated at each iteration. Corrections follow a locally linearized hypersphere. The arc length does not change during the iterations.

At the first iteration, you can also choose between a Tangent Predictor Vector or a Secant Predictor Vector. You can also specify the Min Radius and the Max Radius for the arc-length radii increment.

Computation stop

The computation stops when:

• The final computation time is reached.

• The maximum time TMAX for which the time step becomes negative is reached. You can anticipate this stop by defining a Stop Time Offset (.SUB TDEC).

• The maximum number of subincrements is reached. You set this maximum with the Maximum Number of Controlled Load Increments (.SUP NPAMAX) option.

• The minimum time step is reached. You set this minimum with the Minimal Time Step option.

Note:

The arc-length corrector methods are not available in Dynamic Analysis Type (.SUB MECA).

For more information, see the Non linear mechanics section of the Simcenter Samcef documentation.

Where do I find it?

Application	Simcenter 3D
Prerequisite	A Simulation file or a FEM file as the work part and displayed partSimcenter Samcef as the specified solver
Simulation Navigator	In an active solution, right-click an active subcase→Edit
Location in dialog box	Continuation Methods page

Look up more details

Solution Step dialog box (Simcenter Samcef Structure Nonlinear Analysis)

Arc-length corrector methods (Simcenter Samcef), Simcenter 3D 2021.1 Series

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