Released: 27 August 2024

Coreform Flex Preprocessor

New features

Example tutorials

Improvements to the mesh, set, and interface managers

The set and interface managers are used to set up boundary conditions and contact interfaces in Coreform Flex. These managers have been improved to simplify workflows for creating meshes, sets, and interfaces.

Simplified terminologies 

We have updated language throughout the Coreform Flex input deck and the Coreform Flex GUI to be more familiar to experienced analysts. The changed terminology is as follows: 

Fill → Mesh

Affine → Rectilinear

Hatch → Element

Hatch Spacing → Element Size

Edge Centered → Element Centered

Import/Export

New import and export functionality is now available in Coreform Flex.

Import. In addition to supporting the import of CAD standard formats including CATIA, SolidWorks, NX, creo, STEP, Parasolid, and ACIS, Coreform Flex now supports the import of Coreform .cf files that can be generated from Coreform Cubit. .cf files can contain both geometry, mesh, and metadata information, which enables any files prepared in Coreform Cubit to be used directly in Coreform Flex.

Export. Coreform Flex Preprocessor is a native isogeometric analysis preprocessor. While it is written expressly to support model setup for Coreform Flex Solver, through the new Bezier Extraction (BEXT) export capability, Coreform Flex can be used to prepare data for simulations in other solvers that have IGA capabilities and read in the Bezier extraction file (.bext), encoded in JSON format, such as LS-DYNA, MOOSE, and Epic. Because BEXT only supports body-fit meshes, this workflow only supports body-fit export, and is as follows: 

1. 1. Use Coreform Cubit to create a body-fit hex mesh of a CAD model. 
   2. Export to the Coreform (.cf) file format, the native file format for Coreform Flex. This export will contain the CAD and mesh.
   3. Import the .cf file in Coreform Flex. 
   4. Using the Mesh Manager in Coreform Flex, create a mesh on the part and select the “CAD with mesh” scheme to select the mesh generated in Coreform Cubit.
   5. In the Job Manager, create a job with type “Trim” and add the desired part(s) to the job.
   6. Run the job by clicking on the “Submit Job” button, which will generate a U-spline mesh fitted to the part’s geometry
   7. Click on the “Export BEXT” button to export the .bext file.

Python interface 

Coreform Flex now supports an integrated Python command console within the GUI application, and can be imported as a module within an external Python session, just as Coreform Cubit.  This means that Coreform Flex simulations can now be fully-automated scripted with Python for design optimization and other processes. To access Coreform Flex via Python, see this forum post with instructions.

Improved Flex meshing robustness

We have fundamentally improved the Flex meshing algorithm to more robustly handle complex CAD models common in modern engineering workflows.

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Solid mechanics

With this release, Coreform Flex has implemented some basic features that enable nonlinear solid-mechanics analyses. These capabilities represent the initial implementations of some of the most common forms of nonlinearities encountered in solid-mechanics.  These capabilities include:

Mechanical Contact

This release introduces mechanical contact and supports frictionless and a Coulomb friction model.  Contact is supported for traditional body-fit hex meshes, Coreform’s novel “flex-mesh” technology, and combinations of these meshes.

Friction contact

Snapshot of results from one of our contact verification tests. The cylinder is moving to the right, the unsymmetric contours of the tangential stress component demonstrates the Coulomb friction contact model.

 Automatic parameters selection

Mechanical contact is a weakly enforced constraint that is strongly discontinuous and requires a “contact-search” step. Coreform Flex now supports automatic selection of parameters for the weak-enforcement and contact-search, based on theory, heuristics, and best practices, which simplifies model setup for a majority of applications.

Compression of a direct-ink write silicone pad. Model setup is drastically-simplified due to the automatic selection of contact parameters.

Materials

Neo-Hookean elasticity

A finite deformation elasticity material model based on a two parameter isotropic hyperelastic strain-energy potential.  Furthermore, an optional pressure-stabilized modification is available for supporting near-incompressibility.

An animation of one of our verification tests demonstrating the robustness of the neo-Hookean elasticity model for large deformations.

Mooney-Rivlin elasticity

A finite deformation elasticity material model based on the three-parameter isotropic hyperelastic “Mooney-Rivlin” strain-energy potential.  Furthermore, an optional pressure-stabilized modification is available for supporting near-incompressibility.

An animation of one of our verification tests for the pressure-stabilized Mooney-Rivlin material model for a nearly-incompressible material.

Neo-Hookean elasticity with isotropic plasticity

An extension of the neo-Hookean elasticity model that adds an isotropic, nonlinear, rate-independent plasticity model based on J2 flow theory.

A snapshot of one of our verification tests for the neo-Hookean isotropic plasticity model.

Solvers

Nonlinear statics

Implicit solver for nonlinear statics problems based on numerical continuation.

Nonlinear dynamic (implicit)

Implicit time integration of dynamic problems based on the generalized-alpha time integration scheme.

Demonstration of the implicit dynamics solver in Coreform Flex, evaluating an elastic ball bouncing on a rigid surface.  The time integration scheme used here applies significant numerical damping of medium-to-high frequencies.

Nonlinear equation solver

Nonlinear implicit schemes require solving a system of nonlinear equations.  This release includes an implementation of the Newton method for solving nonlinear systems of equations.  As Coreform Flex currently only supports direct solvers for linear systems of equations, the overall nonlinear solution method supported by Coreform Flex is the Newton-Raphson method.

Boundary conditions

Automatic penalty estimation

Unlike traditional FEA, Coreform Flex uses non-interpolatory spline basis functions and immersed techniques.  This means that Dirichlet (solution) boundary conditions must be weakly-enforced, rather than strongly-enforced.  Weak-enforcement algorithms support / require parameters defining how to enforce them.  In this release Coreform Flex supports automatic parameter selection based on theory and best-practices, simplifying model setup for a majority of applications.

One of our verification problems that demonstrates the automatic estimation of weak-enforcement parameters for boundary conditions. This problem also includes mechanical contact, with automatic parameter estimation, as well as the neo-Hookean isotropic plasticity model and the implicit dynamic solver – further demonstrating all the other features of this release working in unison with the automatic weak-enforcement parameters’ estimation.