Code: microMegas

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Name microMegas (mM)
Status released
Release Date mM v. 1.0 - 09/2009; mMpar v. 1.0 - 01/2010
Authors Developers Team at CNRS ONERA, France; mMpar v.1.0=extension of original mM v. 3.2 + OpenMP additions, by Florina Ciorba
Contact CNRS-ONERA The Developers' Team or Sebastien Groh
License GNU GPL License
Repository mM v1.0 or mMpar
Documentation mM: README.txt (mM/trunk); README.txt (mM/tags/1.0) or mMpar: README.txt (mMpar/trunk); MSU.CAVS.CMD.2010-R0002.pdf (mMpar/doc)
Known problems None
Description MicroMegas is a 3-D DDD (Discrete Dislocation Dynamics) simulations

To report bugs, problems or to make comments please use the discussion tab above.


Contents

Overview of microMegas

MicroMegas (also known as 'mM') is an open source program for DD (Dislocation Dynamics) simulations originally developed at the 'Laboratoire d'Etude des Microstructures', CNRS-ONERA, France. mM is a free software under the terms of the GNU General Public License as published by the Free Software Foundation. Discrete dislocation dynamics (DDD) is a numerical tool used to model the plastic behavior of crystalline materials using the elastic theory of dislocations [1]. DDD is the computational counterpart to in site TEM tests. MicroMegas is a legacy simulation code used to study the plasticity of mono-crystalline metals, based on the elasticity theory that models the dislocation interactions into an elastic continuum. In crystalline materials, plastic deformation may be explained by (i) twinning, (ii) martensic transformation or/and (iii) dislocation interactions (see Figure 1).

MicroMegas is used at CAVS for modeling dislocation interactions and reactions in an elastic continuum. The code is used in a hierarchical multiscale framework of the plasticity to obtain information related to the hardening of the material (see for example, the multiscale framework presented in this review paper‎). Details of the discrete dislocations model can be found in the methodology‎ paper and in the references at the bottom of the page.

The discrete dislocation simulation code can be used for HCP, BCC and FCC materials.

Available DDD Codes

  • microMegas [2]
    • serial version mM
    • parallel version (openMP) mMpar

Setup

microMegas can be freely downloaded from the original development site at the French Aerospace Lab. It can also be downloaded from the CAVS Cyberinfrastructure Repository of Codes in two versions:

  • mM ver 1.0 – serial mM [original ver. 3.2] with various Intel Compiler Optimizations, or
  • mMpar ver. 1.0 – parallel version of mM [original ver. 3.2], where force calculations for each segment are calculated in parallel using OpenMP threads.

In this page we describe how to install, configure and run DDD simulations using mM ver. 1.0 (with Intel Compiler optimizations) and mMpar ver. 1.0 (with Intel Compiler optimizations and OpenMP threads). Installation instructions for mM ver. 1.0 and mMpar ver. 1.0 can also be found in the ‘readme’ files provided in each directory and subdirectory of the code. mM can be run in batch mode to get data analyzed with conventional graphical display programs (exemples of Gnuplot scripts are provided) or it can be used in interactive mode to simply visualize dislocations activity. Herein, we describe how to run the code in batch mode. For instructions on how to run mM in interactive mode, please refer to the ‘readme’ files provided with the code.

Before compiling microMegas on any of the HPC-CAVS computing systesm, one needs to route to the proper compiler and MPI path on the system using:

  • swsetup intel - to use the latest Intel Fortran Compiler installed on the system, and
  • swsetup openmpi-intel-64 - to use the latest version of the OpenMPI libaries, compiled with the Intel compiler for 64-bit systems.

Input files

The input files are located in the mM/in directory. The following files are needed to run the mM simulation.

  • ContCu

The input file with parameters used for the simulation. For instance, one can select the type of simulation (initial or restart from previous simulation) via the parameter SIDEJA. One can also select whether cross-slip displacement of dislocations is desired by setting the GLDEV parameter accordingly (‘T’ for enabled and ‘F’ for disabled). Also, one can set the total number of simulation steps via the NSTEP parameter. Each simulation time step corresponds to 10-9 real time seconds. Therefore, for a very small simulation use NSTEP=500 while for a long running simulation set NSTEP to anything from 106 and above. Finally, one can also select how often should the simulation save the current state of the code, via the KISAUVE, KISTAT, KKIM and KPREDRAW parameters. For more details, check the file that comes with code. An example of the content of this file is given below.


0             SIDEJA            Simulation state key: 0=New or restart with control modification;  1=simple restart
0             mode_deformation  0=strain rate.; 1=make carto; 2=run carto; 3=stress rate.; 4=creep; 5=fatigue; 6=metalofute; 7=metalofute2

14.8          echelle           simulation reference scale, i.e. size of the elementary BD vectors. (unit = Burgers vectors)

F             Shear             Applied stress is the resolved shear stress on the slip system with the highest Schmid factor (false = uniaxial stress)
4.0           Sigma0            Initial stress (MPa)
1.00D-9        DELTAT0           Elementary time step (s)
1000000       SigmaPoint        Elementary stress increments (units ?)      (mode_deformation=3,6,7)
20            EpsilonPoint      Imposed strain rate (s-1)                   (mode_deformation=0,5,6,7)
1.5           RAID              Apparente Young modulus                     (mode_deformation=0,5,6,7)
3.0D-5        EPSMAX            Maximum plastic strain per cycles           (mode_deformation=5)
1.D0          FSIG              Sign of the loading for the first cycle     (mode_deformation=5)

2             LINTEN            Line tension key: 0 -> Friedel approx; 1 -> Isotropic; 2 -> Isotropic Foreman; 3 -> Anisotrpic solution
F             GLDEV             Cross slip key:GLDEV=True means cross-slip active

0 0 1         Tensile_axis      Tensile or compression uniaxial test direction (miller indices)
300.          TEMPERATURE       Tenperature (Kelvin)
100           Facteur_Depmax    Maximum displacement tolerate for a dislocation segment (unit=BD vectors)

50            NstatControl      Number of steps accounted for in the simulation control feedback procedure ((mode_deformation=0,5,6,7)

0             relax_TL          Number of steps for the intial relaxation with only a line tension
0             relax_INT         Number of steps for the intial relaxation with no applied loading and no contact reactions
0             relax_reac        Number of steps for the intial relaxation with no applied loading
500            NSTEP             Number of steps for the simulation

0.25          Ldis_act          Reference mean length to force segments discretization (micron)
0.50          Ldis_nact         Reference mean length to force segments discretization on inactive slip systems (micron)

20            Period            Step periodicity at which the force on waiting (quasi-imobile) segments is recalculate
10            KRC               Step periodicity at which the long-range contribution to the internal stress is recalculated (if Greengard method)
3.0           L_Boite	        Linear mean size of the domaines used in the Greengard method (micron), negative value means dynamically defined 
5.0           AB_LENGTH_SEUIL   Maximum length of segments neglected in the long range contribution (if Greengard method)
5             DCFJ              Distance at which stress is calculated on the segments connected to a junction (unit: vector BD)

0             GB                Barriers key: 0-> inactives, 1-> planes, 2->spherical, 3->regular 3D network (polycristal)

100           TauINT_LIMITE     Critical stress at which the segments are considered as singular (MPa)

400            KISAUVE           Writing periodicity of the simulation segment configuration and information needed to restart a computation
400            KSTATS            Writing periodicity if simulation results
400             KKIM              Writing periodicity of the trajectory film information
100            KPREDRAW          Periodicity of the graphical interaface refresh

0             shift_rotation    Key for the translation and rotation of the simulation box boundary conditions (see the file shift_rotation)

-6542         iterinfo          step of debbug  (negative means no debbug)
-2            sysinfo           slip system of interest in the debbug procedure (needed in simulations with many segments) 
  • Cu

This is the file containing the material variables. See the existing file for more details. An example of this file is given below.

26.6            ModuleG0                : G(0)=Shear modulus (GPa) at T = 0 K
0.0             dmusurdT                : rate of the Shear modulus temperature dependency
0.347D0         DPOISS                  : Poisson modulus

30.D6           TAUIII                  : stress defining the begining of stage III (GD) in Pa
0.9             BETA                    : 1st cross-slip parameter - pre-exp term (GD)
0.6             ALPHA                   : 2d cross-slip parameter - Ratio TauG TauD (GD)

CFC             crystal_structure       : Cristallographic symetry of the material (VARMVT)[2]
1               Nb_slip_types           : Number of slip system family (VARMVT)

2.86378         VecBurgers              : Norme of the Burgers vector (en Angstrom)
-1 -1 -1        Slip % planes           : ireference glide plane
-1 0 1          Slip % directions       : reference gliding direction
12              Slip % Nsystemes        : number of slip systems (all of the same crystallographic type)
2 2 2 2         Numero_loi_brute        : velocitu law applied to the vis,mixte1,edge,mixte2 dislocation caractere


2               NLV                     : Number of velocity law to consider

1               Nloi                    : velocity law index
0               Slip % Arrhenius        : clef : /=0 thermally activated, 0 = athermal
1.D-4           Slip % Coef_visqueux    : viscous friction coeficient
0.              Slip % Max_friction     : dry friction coeficient (Peierls) in MPa

2               Nloi                    : velocity law index
0               Slip % Arrhenius        : clef : /=0 thermally activated, 0 = athermal
5.5D-5          Slip % Coef_visqueux    : viscous friction coeficient
0.5             Slip % Max_friction     : dry friction coeficient (Peierls) in MPa

##################################
Velocity law exemples

-Please notice that one simulation can use several friction law, for different slip systems or even different line characters
-the law with index 1, is the one used during the initial configuration relaxation step (if defined).

Viscous law:

1               Nloi                    : velocity law index
0               Slip % Arrhenius        : clef : /=0 thermally activated, 0 = athermal
1.D-4           Slip % Coef_visqueux    : viscous friction coeficient
0.              Slip % Max_friction     : dry friction coeficient (Peierls)

Thermally activated law:

2               Nloi                    : Velocity law index
0               Slip % Arrhenius        : clef : /=0 thermally activated, 0 = athermal
262.0D6         Slip % taueff0          : effectif tau at zero K  (Pa)
1600.           Slip % V0               : constante de la loi de vitesse en m/s
5.D-6           Slip % L0               : longueur de refernce des vis pour la loi de vitesse en m.
1.06            Slip % deltaG0          : Energie d'activation totale en eV (pour T = 0 K pour les vis)
0.757           Slip % coef_p           : exposant p de la loie de vitesse (pour les vis)
1.075           Slip % coef_q           : exposant q de la loie de vitesse (pour les vis)
  • SegCu

This is the file containing the initial dislocation configuration (e.g., the active slip systems, the number of segments, the dimensions of the simulation reference volume box, etc). See the bottom of the existing file for more details.

 1 1 1 1 1 1 1 1 1 1 1 1
 1
 3632 4016 4816
     1      1816      1344      1744  664     17      0      0      0      0  F      0  F
     1      2476      2008      1744  664      1      0      0      0      0  F      0  F
     
initial screw dislocation in the middle of the box
     1      2476      2008      1744  664      1      0      0      0      0  F      0  F
initial edge dislcoation in the middle of the box
     1      1152      3336      1748  664      1      0      0      0      0  F      0  F


     1      2176      1984      3744  664      7     -3     -3     -1     -1  F      0  F
     2       848       624      2416  664     11     -1     -1     -1     -1  F      0  F
     3      2176      3280      3744  664      3     -1     -1     -1     -1  F      0  F
     4      3504       624       256  664     15     -1     -1     -3     -3  F      0  F
     5      1952        32      4416  664     11     -3     -3     -1     -1  F      0  F
     6      3280      2688       928  664      7     -1     -1     -1     -1  F      0  F
     7      1952      1328      4416  664     15     -1     -1     -1     -1  F      0  F
     8       624      2688      3088  664      3     -1     -1     -3     -3  F      0  F
     9      3488       288      2640  664     19     -3     -3     -1     -1  F      0  F
    10      2512      1616      1312  664     27     -1     -1     -1     -1  F      0  F
    11      3488      2944      4800  664     23     -1     -1     -1     -1  F      0  F
    12       832      1616      1312  664     31     -1     -1     -3     -3  F      0  F
    13      2576      1200      1840  664     31     -3     -3     -1     -1  F      0  F
    14      1600      3888      3168  664     19     -1     -1     -1     -1  F      0  F
    15       624      1200      1840  664     27     -1     -1     -1     -1  F      0  F
    16      1600      2528       512  664     23     -1     -1     -3     -3  F      0  F
    17      2368      3936       896  664     35     -3     -3     -1     -1  F      0  F
    18      1040      2608      3056  664     43     -1     -1     -1     -1  F      0  F
    19      3344      1280       896  664     39     -1     -1     -1     -1  F      0  F
    20      1040      2608      3552  664     47     -1     -1     -3     -3  F      0  F
    21       720      1472      4592  664     47     -3     -3     -1     -1  F      0  F
    22      2048      2800      1936  664     35     -1     -1     -1     -1  F      0  F
    23       720      1472      4096  664     43     -1     -1     -1     -1  F      0  F
    24      3024       144      1936  664     39     -1     -1     -3     -3  F      0  F
    25       432      2512      4112  664     55     -3     -3     -1     -1  F      0  F
    26      2736      3840      1456  664     63     -1     -1     -1     -1  F      0  F
    27      1408      1152      4112  664     51     -1     -1     -1     -1  F      0  F
    28      2736      3840      1952  664     59     -1     -1     -3     -3  F      0  F
    29       528      1504      1216  664     59     -3     -3     -1     -1  F      0  F
    30      1856       176      3376  664     51     -1     -1     -1     -1  F      0  F
    31      3184      2864      1216  664     63     -1     -1     -1     -1  F      0  F
    32      1856       176      3872  664     55     -1     -1     -3     -3  F      0  F
    33      2880       448      1248  664     67     -3     -3     -1     -1  F      0  F
    34       224      1776      2576  664     75     -1     -1     -1     -1  F      0  F
    35      2880      3104      3904  664     71     -1     -1     -1     -1  F      0  F
    36      1904      1776      2576  664     79     -1     -1     -3     -3  F      0  F
    37       992      3024      3072  664     79     -3     -3     -1     -1  F      0  F
    38      1968      1696      1744  664     67     -1     -1     -1     -1  F      0  F
    39      2944      3024      3072  664     75     -1     -1     -1     -1  F      0  F
    40      1968       336      4400  664     71     -1     -1     -3     -3  F      0  F
    41      2960      1104      3056  664     87     -3     -3     -1     -1  F      0  F
    42       656      2464      1728  664     95     -1     -1     -1     -1  F      0  F
    43      1984      1104       400  664     83     -1     -1     -1     -1  F      0  F
    44       656      3760      1728  664     91     -1     -1     -3     -3  F      0  F
    45      3360      1184      2416  664     91     -3     -3     -1     -1  F      0  F
    46      2032      2544      3744  664     83     -1     -1     -1     -1  F      0  F
    47       704      1184       256  664     95     -1     -1     -1     -1  F      0  F
    48      2032      3840      3744  664     87     -1     -1     -3     -3  F      0  F

------------------------------------------------------------------
------------------------------------------------------------------
The segment file structure :

Line 1: An integer for each slip system is defined to change the Schmid factors of slip systems
(1 means that any change is made, 0 means that the Schmid's factor is artificialy set to zero)

line 2: The number of segments

line 3: dimensions of the simulation reference volume

Form line 3 to doted lines: the segments description
column 1 - The segment index
column 2 - x coordinate of the segment origin
column 3 - y coordinate of the segment origin
column 4 - y coordinate of the segment origin
column 5 - length of the segment in BVD vector
column 6 - index of BVD vector for the segment
column 7 - first neighbor segment at the origin side (zero for pining point)
column 8 - first non zero length neighbor segment at the origine side (idem)
column 9 - first neighbor segment at the extremity side (idem)
column 10- first non zero length neighbor segment at the extremity side (idem)
column 11- Flag for junction segment
column 12- index of the junction binome segment
column 13- Flag for screw segment in cross-sliped state (blocked at the intersection of two glide planes)


  • Segments

This is the file describing the initial number, type and characteristics of the dislocation segments. See the existing file for more details.

 1 1 1 1 1 1 1 1 1 1 1 1
                    96
                  6032                  6672                  7984
     1      3616      3296      6208 1360      7     -3     -3     -1     -1  F      0  F
     2       896      2064      3488 1360     11     -1     -1     -1     -1  F      0  F
     3      3616       832      6208 1360      3     -1     -1     -1     -1  F      0  F
     4       304      2064       944 1360     15     -1     -1     -3     -3  F      0  F
     5      3248        64      7344 1360     11     -3     -3     -1     -1  F      0  F
     6      5968      5504      2080 1360      7     -1     -1     -1     -1  F      0  F
     7      3248      4272      7344 1360     15     -1     -1     -1     -1  F      0  F
     8       528      5504      4624 1360      3     -1     -1     -3     -3  F      0  F
     9      5792       480      4384 1360     19     -3     -3     -1     -1  F      0  F
    10      5200      3200      1664 1360     27     -1     -1     -1     -1  F      0  F
    11      5792      5920      6928 1360     23     -1     -1     -1     -1  F      0  F
    12       352      3200      1664 1360     31     -1     -1     -3     -3  F      0  F
    13      4288      2000      3056 1360     31     -3     -3     -1     -1  F      0  F
    14      3696      5952      5776 1360     19     -1     -1     -1     -1  F      0  F
    15      3104      2000      3056 1360     27     -1     -1     -1     -1  F      0  F
    16      3696      4720       336 1360     23     -1     -1     -3     -3  F      0  F
    17      3952      6544      1488 1360     35     -3     -3     -1     -1  F      0  F
    18      1232      3824      4032 1360     43     -1     -1     -1     -1  F      0  F
    19      4544      1104      1488 1360     39     -1     -1     -1     -1  F      0  F
    20      1232      3824      6928 1360     47     -1     -1     -3     -3  F      0  F
    21      1216      2464      7632 1360     47     -3     -3     -1     -1  F      0  F
    22      3936      5184      2192 1360     35     -1     -1     -1     -1  F      0  F
    23      1216      2464      4736 1360     43     -1     -1     -1     -1  F      0  F
    24      4528      6416      2192 1360     39     -1     -1     -3     -3  F      0  F
    25       720      4176      6816 1360     55     -3     -3     -1     -1  F      0  F
    26      4032       224      1376 1360     63     -1     -1     -1     -1  F      0  F
    27      1312      2944      6816 1360     51     -1     -1     -1     -1  F      0  F
    28      4032       224      4272 1360     59     -1     -1     -3     -3  F      0  F
    29       880      2496      2016 1360     59     -3     -3     -1     -1  F      0  F
    30      3600      6448      4560 1360     51     -1     -1     -1     -1  F      0  F
    31       288      3728      2016 1360     63     -1     -1     -1     -1  F      0  F
    32      3600      6448      7456 1360     55     -1     -1     -3     -3  F      0  F
    33      4784       736      2080 1360     67     -3     -3     -1     -1  F      0  F
    34      5376      3456      4800 1360     75     -1     -1     -1     -1  F      0  F
    35      4784      6176      7520 1360     71     -1     -1     -1     -1  F      0  F
    36      4192      3456      4800 1360     79     -1     -1     -3     -3  F      0  F
    37      1664      5040      5104 1360     79     -3     -3     -1     -1  F      0  F
    38      2256      2320      2384 1360     67     -1     -1     -1     -1  F      0  F
    39      2848      5040      5104 1360     75     -1     -1     -1     -1  F      0  F
    40      2256      1088      7824 1360     71     -1     -1     -3     -3  F      0  F
    41      4928      1824      5056 1360     87     -3     -3     -1     -1  F      0  F
    42      1616      3056      2336 1360     95     -1     -1     -1     -1  F      0  F
    43      4336      1824      7600 1360     83     -1     -1     -1     -1  F      0  F
    44      1616       592      2336 1360     91     -1     -1     -3     -3  F      0  F
    45      5568      1968      4016 1360     91     -3     -3     -1     -1  F      0  F
    46      2848      3200      6736 1360     83     -1     -1     -1     -1  F      0  F
    47       128      1968      1472 1360     95     -1     -1     -1     -1  F      0  F
    48      2848       736      6736 1360     87     -1     -1     -3     -3  F      0  F
    49      5264       720      2416 1360      3     -3     -3     -1     -1  F      0  F
    50      1952      1952      5136 1360     11     -1     -1     -1     -1  F      0  F
    51      4672       720      7856 1360      7     -1     -1     -1     -1  F      0  F
    52      1952      6160      5136 1360     15     -1     -1     -3     -3  F      0  F
    53      4016      5616      7408 1360     15     -3     -3     -1     -1  F      0  F
    54      1296       176      4688 1360      7     -1     -1     -1     -1  F      0  F
    55      4608      5616      1968 1360     11     -1     -1     -1     -1  F      0  F
    56      1296      4384      4688 1360      3     -1     -1     -3     -3  F      0  F
    57      5008      2032       224 1360     23     -3     -3     -1     -1  F      0  F
    58      5600      5984      2944 1360     27     -1     -1     -1     -1  F      0  F
    59       160      2032       224 1360     19     -1     -1     -1     -1  F      0  F
    60      5600      4752      5488 1360     31     -1     -1     -3     -3  F      0  F
    61      1472      3920      4224 1360     27     -3     -3     -1     -1  F      0  F
    62      2064      6640      1504 1360     23     -1     -1     -1     -1  F      0  F
    63      2656      3920      4224 1360     31     -1     -1     -1     -1  F      0  F
    64      2064      1200      6944 1360     19     -1     -1     -3     -3  F      0  F
    65      5024       672      3840 1360     39     -3     -3     -1     -1  F      0  F
    66      1712      3392      1296 1360     43     -1     -1     -1     -1  F      0  F
    67      5024       672      6736 1360     35     -1     -1     -1     -1  F      0  F
    68      2304      4624      1296 1360     47     -1     -1     -3     -3  F      0  F
    69      2032      1440      2928 1360     47     -3     -3     -1     -1  F      0  F
    70      4752      4160      5472 1360     39     -1     -1     -1     -1  F      0  F
    71      1440       208      2928 1360     43     -1     -1     -1     -1  F      0  F
    72      4752      4160       384 1360     35     -1     -1     -3     -3  F      0  F
    73      3040      2640      6800 1360     55     -3     -3     -1     -1  F      0  F
    74       320      5360      1360 1360     63     -1     -1     -1     -1  F      0  F
    75      3632      1408      6800 1360     51     -1     -1     -1     -1  F      0  F
    76       320      5360      4256 1360     59     -1     -1     -3     -3  F      0  F
    77       592      2864      3744 1360     63     -3     -3     -1     -1  F      0  F
    78      3904      5584      1200 1360     51     -1     -1     -1     -1  F      0  F
    79       592      2864      6640 1360     59     -1     -1     -1     -1  F      0  F
    80      3312       144      1200 1360     55     -1     -1     -3     -3  F      0  F
    81      5024      4528      6192 1360     67     -3     -3     -1     -1  F      0  F
    82      5616       576       928 1360     75     -1     -1     -1     -1  F      0  F
    83      5024      3296      3648 1360     71     -1     -1     -1     -1  F      0  F
    84      4432       576       928 1360     79     -1     -1     -3     -3  F      0  F
    85      4608      4688      6832 1360     79     -3     -3     -1     -1  F      0  F
    86      5200      1968      4112 1360     71     -1     -1     -1     -1  F      0  F
    87      4608      5920      1392 1360     75     -1     -1     -1     -1  F      0  F
    88      4016      1968      4112 1360     67     -1     -1     -3     -3  F      0  F
    89       704      3600      6560 1360     83     -3     -3     -1     -1  F      0  F
    90      4016      2368      1296 1360     95     -1     -1     -1     -1  F      0  F
    91       704      1136      6560 1360     87     -1     -1     -1     -1  F      0  F
    92      3424      2368      3840 1360     91     -1     -1     -3     -3  F      0  F
    93      3280        16      5840 1360     91     -3     -3     -1     -1  F      0  F
    94       560      1248       576 1360     87     -1     -1     -1     -1  F      0  F
    95      3280      2480      5840 1360     95     -1     -1     -1     -1  F      0  F
    96      6000      1248      3120 1360     83     -1     -1     -3     -3  F      0  F
------------------------------------------------------------------
------------------------------------------------------------------
 Latice simulation parameter =   1.498498709443860E-003
 Size of the simulation box (microns) =    10.0000000000000     
 Parallelepipede (Non : 0, Oui : PARA) :   0.905000000000000     
   1.00000000000000        1.19800000000000     
 Number of domains used to homogenize the density (NbUd) = 
                     3
 Density (*10^12) =    1.00000000000000     
 Length of sources (microns), dispertion), number of sources (total and per slip
  systems) =    10.0000000000000       0.000000000000000E+000
                   108                     2
 Tolerance :   0.800000000000000     
 Angular dispersion of character   0.349065850398866     
 Max :   0.543336856878968     
 Ratio of occupation in domains =    1.00000000000000     
 Effective density =  0.180451757999050       10^-12


  • b_plan, b_poly1, b_spher

These are the input files needed to run polyphase simulations. See the existing files for more details.

b_plan

Input file for the simulations working with planes boundaries

One must define:

line 1 = the variable named longminseg gives the minimum lenght to discretize segments stopped 
         on barriers (minimum lenght->modur/longminseg)
line 2 = the total number of planes defining the closed domaine of simulation (e.g. a cubic doamine =6)
         Notice that "0" means that any closed domaine is defined.
line 3 = T means that the intial dislocations must be outside the close area defined above
         F means that the intial dislocations must be inside the close area defined above
line 4 = The total number of planes to be considered. Additional planes with respect to the definition of line 1
         correspond to internal barriers
         
from line 5 = each normal planes vector (e.g. 0 0 1) and the shifting amplitude D such that Ax + By + Cz = D

exemple (1) a periodic bicrystal
100
0
F
1
1 0 0  500

exemple (2) a finit cubic grain
100
6
F
0
1 0 0       100.
0 1 0       100.                
0 0 1       100.               
-1 0 0    -4000.     
0 -1 0    -4000.            
0 0 -1    -4000.              

> Reading start after the following line
###########################################################
100                  !  longminseg
6                    !  nbplanDom 
T                    !  InclExcl 
6                    !  NbPlanMax
1 0 0      500.      !  varplan     posplan 
-1 0 0    -3132.     
0 1 0      500.                
0 -1 0    -3516.            
0 0 1      500.               
0 0 -1    -4316.              

b_poly1

Tesselation parameters

##############################
100                    the variable named longminseg gives the minimum lenght to discretize segments stopped 
                       on barriers (minimum lenght->modur/longminseg)
F	               Desorientation key: TRUE means activation of euler angles (file (eulerangle)
4992                   Box Size (X=Y=Z) en a
16                     Grain number (2 or 16)
POSdeux                COnstant array corresponding to the grain number
                       -POSun for system with 2 grains
                       -POSdeux for system with 16 grains           

b_spher

Commentaire a faire

###############################
2.2   !The sphere grain radius in micron

Simulation source files

Micromegas is written in a mix of Fortran 90 and Fortran 95, consists of 18 source modules and contains roughly 25,000 lines of code. The pseudocode of the MAIN module in Micromegas is shown below.

! Module MAIN: simulation time loop
TIME: do = 1, STEPS
...
call SOLLI ! Apply load 
call DISCRETI ! Discretize the simulation volume !into dislocation lines/segments
call FORCE ! Calculate interaction forces 
!FORCE calls SIGMA_INT_CP to calculate short !range interaction forces
!FORCE calls SIGMA_INT_LP to calculate long !range interaction forces
call DEPPREDIC ! Predict moving segments 
call UPDATE ! Search for obstacles, determine & make contact reactions, update positions of segments
call CORRIGER_CONFIG ! Check the connections between all segments
...
enddo TIME

A typical simulation run in Micromegas requires somewhere between 10^6 to 10^9 time steps to gain more insight about the plastic deformation range. Simulations with a smaller number of steps will very likely not capture the plastic range of deformation – the region of interest for the materials scientists studying plastic deformation. A simulation run over 10,000 steps using serial version of Micromegas requires 68 hours on average and reaches 0.2% of the plastic deformation on a Nehalem quad-core Xeon W3570 processor, with 6GB of triple channel 133MHz DDR-3 RAM. Simulations of about 10^9 time steps are needed to reach the desired percentage of deformation, that is, the strain rate as high over 1% as possible.

References

Please remember to cite the relevant references from the list below when publishing results obtained with microMegas:

  • F. M. Ciorba, S. Groh and M. F. Horstemeyer. Parallelizing discrete dislocation dynamics simulations on

multi-core systems. 10th Int. Conf. on Computational Science, Procedia Computer Science, 1:1, pp. 2129-2137, 2010.

  • S. Groh, E. B. Marin, M. F. Horstemeyer, and H. M. Zbib. Multiscale modeling of the plasticity in an aluminum single crystal. Int. J. of Plasticity, 25, pp. 1456-1473, 2009.
  • S. Groh and H. M. Zbib. Advances in Discrete Dislocations Dynamics and Multiscale Modeling, J. Eng. Mater. Technol. vol. 131:4, 041209 (10 pages), 2009.
  • Multiscale Modeling of Heterogenous Materials: From microstructure to macro-scale properties. Chapter 2: Discrete Dislocation Dynamics: Principles and Recent Applications (by Marc Fivel). Edited by Oana Cazacu. Published by Wiley. ISBN: 9781848210479, 2008.
  • B. Devincre, V. Pontikis, Y. Brechet, G.R. Canova, M. Condat and L.P. Kubin. Three-dimensional Simulations of Plastic Flow in Crystals. Plenum Press: New York, M. Marechal, B.L. Holian (eds.), 1992, p. 413
  • L.P. Kubin and G. R. Canova. The modelling of dislocation patterns. Scripta Metall., 27, pp. 957-962, 1992.

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