Code: microMegas
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== Running microMegas == | == Running microMegas == | ||
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. | 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. | ||
| + | |||
| + | To get an idea of the type of simulations that can be conducted with microMegas, we give here the parameters of a representative simulation selected in the input files, the compilation and execution commands. The simulation parameters of a representative microMegas simulation are: | ||
| + | * 0.5% plastic deformation | ||
| + | * 10x10x10 µm^3 simulation box dimensions | ||
| + | * 1012 1/m^2 initial density | ||
| + | * 10 1/s strain rate in multi-slip conditions | ||
| + | ''Note'': Multi-slip calculations were performed to evaluate and demonstrate the efficiency of the parallel version of microMegas. | ||
| + | * Material: representative volume elements of Al (FCC crystal structure with Burgers vector of magnitude b = 2.86 Å) of dimensions 9x10x12 µm^3 | ||
| + | * For '''tension simulations''': loading along the [001] direction | ||
| + | * For '''compression simulations''': loading along the [100] direction | ||
| + | * strain rate of 20 1/s | ||
| + | * temperature of 300 K under periodic boundary conditions | ||
| + | * time step was considered to be 1/10^9 seconds | ||
| + | ''Note'': Screw dislocations were not allowed to cross-slip at any time. | ||
| + | |||
| + | |||
| + | |||
| + | == Output files == | ||
== References == | == References == | ||
Revision as of 15:18, 2 September 2010
| 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
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 |
The source files are located in the mM/src/simu/ directory. These 18 modules are briefly described below. For more information, please refer to the actual content of these files.
- 01constantes.f90 - module containing the declaration of all simulation constants
- 02bricamat.f90 - module containing a toolbox of useful subroutines for, e.g., dot products, etc.
- uses 01constantes module
- 03varbase.f90 – module containing the data structures and variables database (lattice, etc)
- uses 01constantes module
- 04varglob.F90 – module containing initializations of all the constants and variables common to all the modules of the main program
- uses 01constantes and 03varbase modules
- 05intergra.f90 – module that enables integration with the graphical module (for interactive modem mM simulations)
- uses 04varglob module
- 06debug.f90 – module containing the subroutines required for debugging, i.e., subroutine Conf(i) and subroutine verif_reseau
- uses 01constantes, 02bricamat, 03varbase and 04varglob modules
- 07init.F90 – module that reads the input files and assigns values to all other variables not initialized in 04varglob
- uses 02bricamat, 04varglob, 06debug and carto modules
- 08connec.f90 – module that checks the connectivity between all segments (not CPU intensive)
- uses 04varglob and 06debug modules
- 09elasti.F90 – module where the short-range and long-range interaction forces between each segments pair is calculated
- uses 02bricamat, 04varglob, 06debug, 08connec and microstructure modules
- 10dynam.F90 - module where the moving velocity of each segment is calculated
- uses 01constantes, 04varglob, 06debug and 08connec modules
- 11topolo.f90 – module containing the procedures used to generate the boundary conditions, to discretize the dislocation lines into segments and to locate the segments before they are eliminated
- uses 04varglob, 06debug, 08connec and microstructure modules
- 12contact.f90 – module containing simple displacements and where the interactions between segments are updated in four steps.
- uses 02bricamat, 04varglob, 06 debug, 08connec and microstructure modules
- check for every possible obstacle,
- check for every possible contact reaction (annihilation, junction formation, etc.),
- make the reactions, and
- update the positions of the segments
- 13resul.F90 – module where the results and statistics are calculated
- uses 02bricamat, 04varglob, 06 debug and microstructure modules
- 14bigsave.F90 – module that saves the simulation state either when the number of selected time steps has elapsed or to be able to restart a computation
- uses 02bricamat and 04varglob modules
- 15main.F90 - main module containing the simulation time loops; it calls all other modules either implicitly or explicitly; for more details see Figure 2
- uses 02bricamat, 04varglob, 06debug, 07init, microstructure, 09elasti, 10dynam, 11topolo, 12contact, 13resul and 14bigsave modules
- base.f90 – module that reads all the data of the main program, in three groups of files:
- materiaux – given material physical properties
- control – given simulation parameters
- seg3D – regroups the characteristics of the segments given at the beginning of the simulation
- uses 01constantes, 02bricamat and 04varglob modules
- carto.f90 – to be written
- microstructure.F90 – module containing the subroutines used to detect the obstacles, i.e., subroutine barriere_spherique and subroutine barriere_plane; it prints the segments structure
- uses 02bricamat, 03varbase, 04varglob, 06debug and 08connec modules
Running microMegas
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.
To get an idea of the type of simulations that can be conducted with microMegas, we give here the parameters of a representative simulation selected in the input files, the compilation and execution commands. The simulation parameters of a representative microMegas simulation are:
- 0.5% plastic deformation
- 10x10x10 µm^3 simulation box dimensions
- 1012 1/m^2 initial density
- 10 1/s strain rate in multi-slip conditions
Note: Multi-slip calculations were performed to evaluate and demonstrate the efficiency of the parallel version of microMegas.
- Material: representative volume elements of Al (FCC crystal structure with Burgers vector of magnitude b = 2.86 Å) of dimensions 9x10x12 µm^3
- For tension simulations: loading along the [001] direction
- For compression simulations: loading along the [100] direction
- strain rate of 20 1/s
- temperature of 300 K under periodic boundary conditions
- time step was considered to be 1/10^9 seconds
Note: Screw dislocations were not allowed to cross-slip at any time.
Output files
References
Please remember to cite the relevant references from the articles 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.
