Material-Modeling Support

The PFC model provides a synthetic material consisting of an assembly of rigid grains that interact at contacts. This synthetic material encompasses a vast microstructural space, and only a small portion of this space has been explored. For example, the bonded-particle modeling methodology provides a rich variety of microstructural models in the form of bonded materials (Potyondy, 2015; Potyondy and Cundall, 2004). The PFC model includes both granular and bonded materials as well as an interface that can be inserted into the bonded materials. The support for material modeling that is provided by PFC2D and PFC3D version 5.0 is provided in the form of a consistent set of FISH functions, which we call the PFC 5.0 FISHTank (or fistPkg). The PFC 5.0 FISHTank provides a state of the art embodiment of four well defined materials and a user-defined material to support: practical applications (via boundary-value models made from these materials), and scientific inquiry (via further exploration of the microstructural space described above). [The PFC 5.0 FISHTank replaces the PFC 4.0 FISHTank from PFC2D and PFC3D 4.0. The Material-Modeling Support memo (Potyondy, 2017) replaces the PFC FISHTank chapters of the PFC2D and PFC3D 4.0 manuals. Material-modeling support may be provided in future versions of PFC by embedding the material-modeling capability directly into the command set of the PFC programs.]

REFERENCES

Potyondy, D. (2017) “Material-Modeling Support in PFC [fistPkg25],” Itasca Consulting Group, Inc., Technical Memorandum ICG7766-L (March 16, 2017), Minneapolis, Minnesota. DOWNLOAD LINK

Potyondy, D. O. (2015) “The Bonded-Particle Model as a Tool for Rock Mechanics Research and Application: Current Trends and Future Directions,” Geosystem Engineering, 18(1), 1–28. DOWNLOAD LINK

Potyondy, D.O., and P.A. Cundall. (2004)  “A Bonded-Particle Model for Rock,” Int. J. Rock Mech. & Min. Sci., 41(8), 1329–1364. DOWNLOAD LINK


This memo describes material-modeling support for PFC 5.0 as provided in the PFC 5.0 FISHTank (or fistPkg), and this memo corresponds with fistPkg25.

The following capabilities are provided by fistPkg25:

  • Material genesis of linear, contact-bonded, parallel-bonded, flat-jointed and user-defined materials (3D hill) in polyaxial, cylindrical and spherical vessels. Material grains can be either balls or clumps. Material tests are compression (confined, unconfined and uniaxial strain), diametral-compression and direct-tension. Microstructural monitoring includes properties (such as grain-size distribution) with microstructural plots and crack monitoring for bonded materials.

Usage instructions are given in fistPkg-README.txt and summarized as:

  • Create a 2D or 3D material (using the appropriate MatGen project).
  • Perform compression, diametral-compression and direct-tension tests on the material (using the CompTest, DiamCompTest and TenTest projects).

The following enhancements are planned:

  • Provide direct-shear and fracture-toughness tests, smooth-jointed interface, and stress-installation procedure.

 

Material-Modeling Support Software Update Revisions

fistPkg Release PFC Release Date / Description
25

5.00.30

3/20/17

Enhancements.

  1. Support clumped grains to provide general grain shapes --- see the common material parameters cm_shape and cm_ctName. Examples of clumped-grain models for granular materials are given in the Linear and User-Defined Materials Examples in the fistPkg memo. An example of clumped-grain models for bonded materials is given in the Contact-Bonded Material Example.
  2. Modify crack-tracking logic: (a) to reduce slowdown caused by crack filtering, and (b) by setting default value of ckUpdateRate to be two million --- the cracks are updated (by a call to ckForceUpdate) at the end of each loading stage before creating the SAV file.
24 5.00.30

2/28/17

Consistency test against PFC 5.00.30 successful.

24 5.00.29

1/18/17

Consistency test against PFC 5.00.29 successful.

24 5.00.27

10/12/16

Enhancements.

  1. Update PFC 5.0 from 5.00.24 to 5.00.27.
  2. Fix crack-tracking bug that caused the diameters of some flat-jointed cracks to be assigned to the wrong flat-jointed elements.
  3. Complete the flat-joint interfaces plot set to display the interface, coordinate systems and discretization.
  4. Add the faced grain plot set. Known bug: 3D faced grains are not being drawn correctly.
  5. New technical memo {Flat-Joint Contact Model [version 1]}  in Documentation\FlatJointContactModel that provides a comprehensive and fully up to date description of the FJ formulation. There are some minor differences from the PFC 5 docSet. This memo also contains a two-grain test problem (in ExampleProjects\FlatJointContactModel\Test-TwoGrains) and exercises the faced-grain plot set.

23

5.00.24

06/23/16

Enhancements.

  1. Enhance crack monitoring: (1) define the crack gap as the surface gap (associated with the contact model), instead of the gap between the two contacting balls; and (2) enhance crack filtering to display the gap-based filtering criterion in the plot caption.
  2. Rename master project directories to remove the "my" designator, for example:

        myMatGen-X ==> MatGen-X, where
           X = {Linear, ContactBonded, ParallelBonded, FlatJointed, Hill}
         myCompTest     ==> CompTest
         myDiamCompTest ==> DiamCompTest
         myTenTest      ==> TenTest

22 5.00.24

05/16/16

Enhancements.

  1. Replace use of term "deviatoric stress and strain" in Section 5.1 {Stress, Strain and Porosity in the Material} of the fistPkg memo with the term "deviator stress and strain." Modify all references to this       term in the memo and in the project files, in particular, modify the title and y-axis label in all pl-wsd_wea views.\
  2. Clarify description of the Hertzian component of the hill contact model in Section 1.4 {Hill Material} of Potyondy (2016). Describe the grain-grain system as "two locally elastic spheres." Refer to the Hertzian component of the surface-interaction force model as Hertz-Mindlin springs [replaces use of Hertzian springs], with the Mindlin portion of the term denoting the tangential response. Provide a footnote summarizing the contact formulation of the Hertz-Mindlin springs, with associated references from which the general solution is obtained for sphere-sphere and sphere-plane contacts between two  elastic bodies with different radii and elastic constants. Describe the Hertzian component of the surface-interaction force model as providing "...the nonlinear force-displacement response arising from mutual       compression of two elastic bodies, which induces a local deformation of the bodies in the vicinity of the contact surface. The local deformation is determined by the shapes and elastic constants of the        bodies in the vicinity of the contact surface." REFERENCE: Potyondy, D. (2016) "Hill Contact Model [version 4]," Itasca Consulting Group, Inc., Minneapolis, MN, Technical Memorandum ICG7795-L (May 13, 2016).
  3. Update PFC 5.0 from 5.00.23 to 5.00.24.
  4. Remove the MakeThenTest drivers for the myMatGen projects, and replace with following scheme. Provide run projects [MatGen&Test-RUN] for each material to create that material and perform appropriate laboratory tests upon it. Provide master run project [MatGen&Test_AllMats-RUN] to create and perform appropriate tests on all materials. Modify all projects to exit upon completion.
  5. Provide plot-generation data files for material genesis, and each laboratory test: X-MakePlots.{p2,p3}dat, where X = {MatGen, CompTest, DiamCompTest, TenTest}.
21 5.00.23

04/18/16

Enhancements.

  1. Modify @mvListProps to list current and initial vessel dimensions. Fix the figures of the linear and hill example materials to show vessel dimensions at the end of material genesis, which are less than the initial vessel dimensions because the boundary-contraction packing procedure moves the vessel walls inward. The previous figures showed the initial vessel dimensions.
  2. Clarify specification of measurement regions within the material vessel--- see new material-vessel parameters mv_inset{D,L}Fac, and note the renaming of _mvMpFac{W,H} ==> mv_inset{D,L}Fac.
  3. Microstructural plotting is now off by default, it had been on by default. Microstructural plotting is turned on by @msOn. It can also be turned on at the end of material genesis by specifying [true] as the value of the new second parameter of mpMake in the material-genesis driver file. For large models, with more than 15000 grains, the microstructural plots require significant memory with a corresponding increase in save-file size. For large models, it is better to keep microstructural plotting off, and only activate it by calling @msOn when generating a microstructural plot.
  4. Reset grain displacements to zero after the seating phase of the tension and compression tests.
  5. Add MakeThenTest drivers to myMatGen projects.
20 5.00.23

02/26/16

Enhancements.

  1. Enhance support for computation of grain size distribution via @gsdGetSizeOfPercentile(pct), which returns grain size corresponding to percentile {pct} for grain size distribution in GSD table created by @gsdMeasure.
  2. Improve microstructural monitoring (see Section 3.0 in fistPkg memo).
  3. Add description of resilent modulus computation as a means to quantify the deformability of a granular material (see Section 5.2 in fistPkg memo).
  4. Add the hill contact model to the fistPkg as a user-defined contact model. The hill contact model is described in Potyondy (2016a). The creation and triaxial testing of a hill material are described in Potyondy (2016b, User-Defined Material Example). A material-behavior study that compares the responses of the linear and hill materials for narrow and broad grain-size distributions is given in Section 2.3 of Potyondy (2016a). The following modifications were made to the user-defined material interface, and to the hill contact model:
    • Provide new file udm_hl.p3fis for udm redefinitions, and replace udm_setMatBehavior with hlm_setMatBehavior.
    • Rename hill model property suc_coef => suction.
    • Rename hill model parameters:
      • hlm_sucCoef    => hlm_suction
      • hl_makeDry     => hlm_makeDry
      • hl_makeWet(gm) => hlm_makeWet(psi, gm)

REFERENCES:
Potyondy, D. (2016a) "Hill Contact Model [version 4]," Itasca Consulting Group, Inc., Minneapolis, MN, Technical Memorandum ICG7795-L (February 26, 2016).
Potyondy, D. (2016b) "Material Modeling Support in PFC [fistPkg20]," Itasca Consulting Group, Inc., Minneapolis, MN, Technical Memorandum ICG7766-L (February 26, 2016).

19 5.00.22 01/12/16
Create microstructural plot sets --- see Section 3.2 {Microstructural Plots}. Hide many of the views, they are manipulated via the Documents button. Modify default values of _mvMpFacH and _mvMpFacW from 0.9 to 0.8; these values control the size of the measurement spheres used to measure stress and strain in the material.
18 5.00.22

12/10/15

Enhancements.

  1. Modify compression test for bonded materials to provide two additional hidden views (pl-mer_wea, pl-mev_wea) to be used during UCS tests. The wall-based radial and volumetric strains are not measured during UCS tests, and thus, the corresponding measurement-based quantities must be used to plot radial and volumetric strain versus axial strain curves.
  2. Enhance microstructural monitoring to include: microstructural properties (overlap ratios [mp_ORs] and bond coordination number [mp_CNb]); crack filtering and gaps; and microstructural plots --- see Section 3.0 {MICROSTRUCTURAL MONITORING}.
17 5.00.21 09/22/15
Enhancements.
  1. Enhance compression test to include uniaxial-strain test (by setting ct_testType = 2).
  2. Delete grains with centers lying outside of the material vessel at the end of step 2 of the packing phase.
  3. Compute grain size distribution (GSD) of synthetic material by calling sdMeasure(numBins) to create table GSD, which is displayed in view pl-GSD (see Section 2.9 {Microstructural Properties} of the material modeling support memo).
16 5.00.20

07/22/15
Minor enhancements.

  1. Force chains can now be displayed as either bi-colored to denote tension and compression or scale-colored to denote magnitude (see plot items: "Contact force chain" and "Contact force_mag"). This capability is described as follows. The macroscopically applied compressive load is carried by the granular material as force chains that propagate from one grain to the next across grain-grain contacts. The force-chain fabric is depicted as a network of cylinders, with a cylinder at each contact. Force magnitude corresponds with cylinder color and thickness, and force direction corresponds with cylinder orientation.
  2. Add {Section 5.4 Loading Rate} to memo {Material Modeling Support in PFC}.         
  3. Improve setup phase of UCS test to move platens away from specimen at ten times the previous rate.
  4. Add geometry set "viewBox" to material-genesis to allow one to display a box of a specified size on each plot (via the Geometry plot item).
15 5.00.17 04/22/15
Add capability to create a user-defined material, with a user-defined material example that creates a 3D Hill material.
14 5.00.15 02/17/15
Add diametral-compression test for PFC2D, with usage example for the 2D parallel-bonded material.
13 5.00.15 02/05/15
Remove the packing parameters: pk_emod and pk_krat. These two properties are replaced by the properties of either the linear material group (lnm_emod and lnm_krat) or the user-defined contact model (as specified in the udm_setMatBehavior FISH function).
12 5.00.15 02/02/15
Two enhancements: (1) Add a spherical material vessel. (2) Add diametral-compression test for PFC3D, with usage example for the parallel-bonded material. Break the material-modeling support memo into three related memos named "Material-Modeling Support in PFC," and "Material-Modeling Support in PFC (Example Materials {1,2}."
11 5.00.15 01/27/15
Two modifications: (1) Fix bug in computation of servomechanism gain in axial direction for 3D cylindrical vessel, and improve computation of wall-based stresses (now controlled by mv_wAreaMode). (2) Add Potyondy (2014) to documentation directory (see reference in entry for fistPkg 10).
10 5.00.15 01/20/15
Modify "Material-Modeling Support in PFC" memo to correspond with updated PFC 5.00.15 documentation set, and to refer to Potyondy (2014). Enhance compression test to support fully unconfined tests. [REFERENCE: Potyondy, D.O. (2014) "The Bonded-Particle Model as a Tool for Rock Mechanics Research and Application: Current Trends and Future Directions," Geosystem Engineering, 17(6), 342-369.]
09 5.00.14 11/17/14
PFC 5.0 FISHTank released to users as fistPkg09.
08 5.00.14 10/20/14
Update the PowerPoint slide set that summarizes Potyondy (2014a). REFERENCE: {Potyondy, D. (2014a) "Material-Modeling Support in PFC," Itasca Consulting Group, Inc., Minneapolis, MN, Technical
Memorandum ICG7766-L, October 20, 2014.}
07 5.00.9 10/10/14
Initial release of the PFC 5.0 FISHTank, which provides the following capabilities (for both PFC2D and PFC3D): material genesis of linear, contact-bonded, parallel-bonded and flat-jointed materials (all grains are balls) in physical material vessels (cylindrical and polyaxial) with compression and direct-tension testing.
06 5.00.9 09/19/14
Minor enhancements since fistPkg05. fistPkg06 has been released for selective internal Itasca review.
05 5.00.9 09/04/14
Material genesis of linear, contact-bonded, parallel-bonded and flat-jointed materials in physical material vessel with compression and direct-tension testing (PFC3D only, all grains are balls). Not yet available: (1) extend to support PFC2D, (2) allow grains to be clumps, (3) provide Brazilian-tension and fracture-toughness tests, (4) provide smooth-jointed interface and (5) provide stress-installation procedure.
04a 5.00.9 07/25/14
THIS IS A PRIVATE VERSION of ongoing developments, created for use of Derrick Blanksma. It supports creation of a linear material, and compression testing of that material. Note that it has been tested with PFC 5.00.9, it should probably work with more recent versions of PFC as well.
03 5.00.9 06/25/14
Modified interface to compression-test procedure to make it correspond with description in the memo: "Material-Modeling Support in PFC."
02 5.00.9 06/22/14
Material genesis and compression testing can be performed on the linear material for which all grains are balls.
01 5.00.7  06/10/14
Establish initial tank to support creation of linear material and compression testing (PFC3D only).

The first column of this table lists the fistPkg revision number; the second column lists the PFC 5.0 release against which the fistPkg has been tested; and the third column describes the fistPkg revision. Note that each revision of the fistPkg is expected to operate with a PFC 5.0 release that is current or newer than that listed. Since newer revisions of the fistPkg may use features available only in newer revisions of PFC 5.0, they may not be compatible with older revisions of PFC 5.0.

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