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FRANC3D Version 7 Development PowerPoint Presentation
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FRANC3D Version 7 Development

FRANC3D Version 7 Development

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FRANC3D Version 7 Development

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  1. Fracture Analysis Consultants, Inc. FRANC3D Version 7 Development June 2014

  2. Changes from Version 6 to Version 7 Main window: setting speed of rotation and translation setting and saving camera positions buttons for setting clipping planes and center of rotation Version 7 Version 6

  3. Cut Planes: Entire model Allows user to cut away a portion of the model based on cutting planes aligned with the global Cartesian axes. Set Speed: Controls the speed of rotation, translation and zooming when “moving” the model with the mouse.

  4. Clipping Visual display of front and back clipping planes Default center of rotation is the center of the model Recenter

  5. Version 7 New Features • New geometric intersection engine for crack insertion (increased robustness) • ABAQUS/ANSYS GUI “look & feel” emulation • Built in sub-model generation tool • Expanded Fatigue Crack Growth Rate library • Expanded automatic FCG stopping options • Robust automatic method for fatigue life integration 5

  6. New Geometric Intersection Engine • The algorithms that compute the intersection curves between a flaw and the uncracked body and “trim off” portions of a flaw that fall outside have been completely rewritten. • Testing has focused on models that failed in the previous version. The new algorithms are proving to be much more robust. 6

  7. Sub-Model Generation Tool 7

  8. Sub-Model Generation Tool 8

  9. Sub-Model Generation Tool 9

  10. ABAQUS/ANSYS Emulation FRANC3D can be run in emulation mode, which mimics the model display and view manipulation “look & feel” used by ABAQUS/CAE or ANSYS/Classic 10

  11. Fatigue Crack Growth Rate Model Library • Separate growth rate and R-ratio models (except NASGRO eqn.) • All model can be specified as temperature dependent Growth rate models: • Paris • Bi-Linear Paris • Sigmoidal • Hyperbolic Sine • Tabular • NASGRO Sigmoidal Paris Bi-Linear Paris Tabular Hyperbolic Sine R-ratio models: • None • Walker • Closure • Tabular NASGRO 11

  12. Fatigue Crack Growth Rate Model GUI A GUI for the expanded FCG rate model library is under development Properties can be specified for various temperatures. Various options are available for interpolating among temperatures Units for material properties specified separately from the analysis model units, conversions are done automatically. 12

  13. Crack Growth Stopping Criteria • Formerly the user had to specify a fixed number of FRANC3D crack growth steps. • Now automatic crack growth stops when the first of the following is satisfied: • We would like to add a stopping criterion related to the maximum crack size, but we have not yet determined the best way to do this. • The new criteria require that FRANC3D maintain a running estimate of the applied cycles. 13

  14. Thick-walled Cylinder Model tension/torsion loads initial 0.1 radius surface crack oriented perpendicular to the cylinder axis 2 24 4 the crack immediately reorients to grow perpendicular to the maximum tension 14

  15. Thick-walled Cylinder Model (Cont.) As the crack grows into the central bore FRANC3D automatically transitions from a single to multiple crack fronts. 15

  16. Conventional Lifing with FRANC3D Results A “path” is defined through the crack fronts that effectively reduces the full 3D results to a single degree-of-freedom crack model. log da/dN The single DOF SIF ranges are integrated with a material growth rate model to determine cycles. log DK 16

  17. Problems With the Conventional Approach • Defining an appropriate K-path becomes difficult for complex crack geometry • Defining a path requires subjective engineering judgment leading to non-objective life predictions • Difficult to automate path selection • Uses only a small amount of the available SIF information ? ? ? ? 17

  18. Multiple/Variable DOF Approach New approach uses many small integration paths between predicted crack fronts (one for each finite element along the crack front). Multiple degrees-of-freedom with a variable number of DOF’s among crack steps. 18

  19. Multiple/Variable DOF Approach For all nodes on a crack front project perpendicular to the crack-front node to find the intersection with the next crack front. interpolate to find the projected DK Assume a linear variation in the DK’s going from step i to step i+1 and integrate to find the cycles where 19

  20. Multiple/Variable DOF Approach (Cont.) Ignore cases where a projected point cannot be found Average the computed cycles for all crack front nodes to find one value for the cycles required to grow from crack front i to crack front i+1 20

  21. Multiple/Variable DOF Approach (Cont.) The approach generates a unique cycle count for each of the crack fronts. 21

  22. Features of the New Approach • Objective life predictions • Uses most of the available data • Easily automated • Easily negotiates complex crack shapes • Generate a vs. N curves on surfaces (where computed K’s are inaccurate) 22

  23. Crack Mouth Coarsening Automatic coarsening of the crack face surface mesh away from the crack front reduces the total number of 3D volume elements generated in the mesh. 140,000 volume elements 42,000 volume elements 23

  24. FRANC3D Analysis Code Interface • switching from ABAQUS .fil results file to a Python script interface that extracts only the required results from the .odb file and saves to a .dtp file with the same format used with ANSYS • Python code that reads .op2 file will allow for similar switch for NASTRAN rather than reading .pch file • allow for shear tractions (in addition to normal pressure) on crack surfaces with update to M-integral SIF computation • new features/data for ANSYS 15 need to be examined 24