Respected Lammps users, I am going to simulate the cohesive zone debonding model using lammps. Which lammps command will execute will be used to model it? Is fracture or crack propagation work similar to measure the debond strength? Is the fracture strength be measured on the dependent cohesive energy element model or is it necessary to input the fracture toughness or elastic modes of failures?
Is it sufficient to write a script on the basis of interatomic potential and related variables?
Thanks for cooperation
Do you have any indication that this can be done with LAMMPS and without using custom C++ code that is not part of the LAMMPS distribution?
I cannot tell because I don’t know that model (and probably most people here don’t), so you would first have to explain how this is realized and what specific features would be needed in the simulation software for that. When posting questions in any online forum, do not make the mistake that everybody is familiar with your area of research; most likely the opposite is the case.
All LAMMPS commands and what they do are documented and the documentation is searchable. So you can search for yourself.
These are all questions about the science and not about LAMMPS and thus are off-topic for the LAMMPS forum categories. You would have to discuss with your adviser or tutor or a collaborator familiar with your specific area of research.
What do you mean by this?
Yes the literature support in the favour of doing it with lammps at atomistic scale to predict dedonding and measuring the fracture strength at the interface of the brazed diamond with silver to measure the debonding strength using traction seperation law between the silver diamond joint. The C++ code may not properly include the effect of failure at atomistic scale.
Which literature? Blanket statements without references for support, like this one, have no value in a scientific discourse.
Which specific C++ code are you referring to? Again, your statement is missing any confirmation from some credible source and thus is pure speculation without any support or proof.
I just need how to define the stregth of delamination between the interfaces of diamond and silver after a brazing of silver on the substrate of diamond. Will it be accomplished by interatomic potential EAM etc. Or the constrint showing the attactive force of joint to hold the interface together is also required which I think may not be suitable because that stuff is what I get experimentally and here at nanoscale all the behaviour changes.
For this how I command in LAMMPS?
Again, these are questions about the science and not about the syntax or semantics and thus something that you will have to sort out with the help of people familiar with your specific area of research.
It is impossible to recommend some commands for as long as you are not at all clear about what your model is comprised of. You’ll have to sort out the science of your model before you can ask about details. …and in that case you can refer to the documentation first. Chances are high, that all necessary information is already there.
There are no “do this kind of problem” type of commands in any simulation software. Rather, the researcher needs to construct a model, decide of potentials and components and then can look up how those can be implemented with the given software. You are trying to do this backwards and that just won’t work.
As far as C++ is concerned I dont have an idea but the research papers support to perform cohesive zone delamination using lammps and I want to proceed using it.
Then all you have to do is to follow the description of how the simulations were set up and performed from models and methods sections of the papers you are referring to.
Let me re-iterate: for as long as you don’t provide anything to back up your statements, nobody can know in detail what you are referring to and everything you state will be considered speculation.
From this I mean that many lammps input script supports the molecular dynamical analysis for example tensile test to be bench marked using experiments. In lammps input script for the tension test many scripts used the elastic moduli, fracture energy as an input variable to get the deformation output and considered eleastic moduli and fracture strength as independent variables while many scripts rely on the interatomic potential like EAM to predict fracture energy, strength, elastic moduli and other fracture properties. So In the same fashion I asked to proceed for cohesive zone debonding traction sepration may I need to define the attractive bonding force also taken from experiments rather than the interatomic potential between diamond and silver only or just interatomic potentials are enough making the system just depending on the interatomic potential rather than experiment.
As the experimentally calculated result if input in molecular dynamical simulation just or show the deformation completely simililar to experiment but if the simulation is done on basis of interatomic potential the results are totally different. ;(attractive or interatomic potentials at the delamination interface of diamond and silver)
After that how to explain that difference why at nanoscale how such a big variation occured like just in the case of gaphene and graphite?
You continue to keep asking predominantly about the science and you still fail to provide any references to back up any of your claims.
I have nothing more to add to this topic.
Here are the two lammps scripts doing the tesion test for graphene and rubber respectively. In the graphene no material property is used to calculate the stress strain curve of material except the interatomic potential while for the rubber elastic poisons ratio, elastic modulus are used as an input variable to go for strength analysis and why not just interatomic potentials are enough? Which will have the right explaination to proceed for tension test validity?
For graphene
“”“”#uniaxial tensile test of graphene
##---------------INITIALIZATION-------------------------------
units metal
dimension 3
boundary p p f
atom_style atomic
newton on
##---------------ATOM DEFINITION------------------------------
read_data grap.data
##---------------FORCE FIELDS---------------------------------
pair_style airebo 3.0
pair_coeff * * CH.airebo C
##---------------SETTINGS-------------------------------------
timestep 0.0005
variable ts equal 0.0005
##---------------COMPUTES-------------------------------------
compute 1 all stress/atom NULL
compute 2 all reduce sum c_1[1] c_1[2]
variable Lx equal lx
variable Ly equal ly
variable Lz equal lz
variable Vol equal vol
variable thickn equal 3.4
fix 1 all npt temp 300 300 0.05 x 0 0 0.5 y 0 0 0.5
thermo 2000
##---------------RELAXATION--------------------------------------
run 50000
##---------------DEFORMATION--------------------------------------
unfix 1
reset_timestep 0
fix 1 all npt temp 300 300 0.05 x 0 0 0.5
fix 2 all ave/time 1 100 100 c_2[1] c_2[2]
fix 3 all ave/time 1 100 100 v_Lx v_Ly v_Lz v_Vol
variable srate equal 1.0e9
variable srate1 equal “v_srate / 1.0e12”
fix 4 all deform 1 y erate ${srate1} units box remap x
run 100
##---------------THERMO-OUTPUTS--------------------------------------
variable CorVol equal f_3[4]*v_thickn/(f_3[3])
variable ConvoFac equal 1/1.0e4
variable sigmaxx equal f_2[1]v_ConvoFac/v_CorVol
variable sigmayy equal f_2[2]v_ConvoFac/v_CorVol
variable StrainPerTs equal v_srate1v_ts
variable strain equal v_StrainPerTsstep
thermo 100
thermo_style custom step temp v_strain v_sigmaxx v_sigmayy pe ke lx ly vol
##---------------DEFORMATION--------------------------------------
dump 1 all atom 5000 tensile_test.lammpstrj
run 500000 “”“”
For rubber
“”“”####################################################################################################
TLSPH example: elongate a 2d strip of a linear elastic material py pulling its ends apart
unit sytem: GPa / mm / ms
####################################################################################################
####################################################################################################
MATERIAL PARAMETERS
####################################################################################################
variable E equal 1.0 # Young’s modulus
variable nu equal 0.3 # Poisson ratio
variable rho equal 1 # initial mass density
variable q1 equal 0.06 # standard artificial viscosity linear coefficient
variable q2 equal 0.0 # standard artificial viscosity quadratic coefficient
variable hg equal 10.0 # hourglass control coefficient
variable cp equal 1.0 # heat capacity of material – not used here
####################################################################################################
INITIALIZE LAMMPS
####################################################################################################
dimension 2
units si
boundary sm sm p # simulation box boundaries
atom_style smd
atom_modify map array
comm_modify vel yes
neigh_modify every 10 delay 0 check yes # re-build neighbor list every 10 steps
newton off
####################################################################################################
CREATE INITIAL GEOMETRY
####################################################################################################
variable l0 equal 1.0 # lattice spacing for creating particles
lattice sq ${l0}
region box block -10 10 -10 10 -0.1 0.1 units box
create_box 1 box
create_atoms 1 box
group tlsph type 1
####################################################################################################
DISCRETIZATION PARAMETERS
####################################################################################################
variable h equal 2.01*{l0} SPH smoothing kernel radius
variable vol_one equal {l0}^2 volume of one particle – assuming unit thickness
variable skin equal {h} Verlet list range
neighbor {skin} bin
set group all volume {vol_one}
set group all smd_mass_density {rho}
set group all diameter ${h} # set SPH kernel radius
####################################################################################################
DEFINE VELOCITY BOUNDARY CONDITIONS
####################################################################################################
variable vel0 equal 0.005 # pull velocity
region top block EDGE EDGE 9.0 EDGE EDGE EDGE units box
region bot block EDGE EDGE EDGE -9.1 EDGE EDGE units box
group top region top
group bot region bot
variable vel_up equal ${vel0}(1.0-exp(-0.01time))
variable vel_down equal -v_vel_up
fix veltop_fix top smd/setvelocity 0 v_vel_up 0
fix velbot_fix bot smd/setvelocity 0 v_vel_down 0
15
####################################################################################################
INTERACTION PHYSICS / MATERIAL MODEL
####################################################################################################
pair_style smd/tlsph
pair_coeff 1 1 *COMMON {rho} {E} {nu} {q1} {q2} {hg} ${cp} &
*STRENGTH_LINEAR &
*EOS_LINEAR &
*END
####################################################################################################
TIME INTEGRATION
####################################################################################################
fix dtfix tlsph smd/adjust_dt 0.1 # dynamically adjust time increment every step
fix integration_fix tlsph smd/integrate_tlsph
####################################################################################################
SPECIFY TRAJECTORY OUTPUT
####################################################################################################
compute S all smd/tlsph_stress # Cauchy stress tensor
compute E all smd/tlsph_strain # Green-Lagrange strain tensor
compute nn all smd/tlsph_num_neighs # number of neighbors for each particle
dump dump_id all custom 10 dump.LAMMPS id type x y z vx vy vz &
c_S[1] c_S[2] c_S[4] c_nn &
c_E[1] c_E[2] c_E[4] &
vx vy vz
dump_modify dump_id first yes
####################################################################################################
STATUS OUTPUT
####################################################################################################
variable stress equal 0.5*(f_velbot_fix[2]-f_veltop_fix[2])/20 # stress = force / initial width
variable length equal xcm(top,y)-xcm(bot,y)
variable strain equal (v_length-{length})/{length} # engineering strain
fix stress_curve all print 10 “{strain} {stress}” file stress_strain.dat screen no
thermo 100
thermo_style custom step dt f_dtfix v_strain
####################################################################################################
RUN SIMULATION
####################################################################################################
run 2500 “”“”
Please see the forum guidelines about how to correctly quote input scripts or any text in the forum. Significant chunks of those files are unreadable.
Those are two very different models. The first is using an atomistic description, the second is a grid free mesoscale model (where the positions do not represent individual atoms). These models differ massively in scale and resolution.
You really need to have an in-depth discussion with an adviser or tutor or competent collaborator. You need a much better understanding of the physics and what models can be used for what purposes. This is near impossible to teach online and specifically difficult in a forum discussion. Also, this is - as stated before - off-topic for the LAMMPS categories. While you are quoting LAMMPS inputs, your question has nothing to do with LAMMPS itself, but is about the models (so you could use just any other simulation code that has support for either model).
You are comparing apples and oranges here. Either model is valid for what it is supposed to be used for and within the error ranges for what they are parameterized for and that are intrinsic in those models, but since they are very different models and applied to significantly different problems and problem sizes, you cannot compare them.
I am very thankful to your deep concern here I need to proceed myself without the help of supervisor because of his research domain belongs to engineering but my topic has a mixture of both engineering and physics.
For the better understanding of physics which branch of physics I need to deal with for deep learning, so that I may learn it separately regarding these issues?
Thanks
If your adviser is lacking the expertise, then a suitably competent collaborator needs to be found.
I strongly advise against learning on your own. That is even more urgent due to your limitations in having a proper scientific discussion. The latter is certainly something that your adviser should be capable of teaching you.