Dear All,
I am just trying to repeat the work published by Osetsky in “Modelling and simulation in Materials science and engineering,11(2003)427-446”. Which had simulated the movement of dislocation under an prescriptive strain rate.
In other to give a constant shear strain rate , I use the method mention in Osetsky’s paper : “applying strain incrementally with relaxation of the crystallite to the minimum potential energy at each step.” & “Relaxation is best achieved by repeated combination of static relaxation by conjugate gradients followed by quasidynamic relaxation with a loweffective temperature, of the order of 10 K” I use a loop in input files to realize it (input data attach in the end )
However , the stress-strain curve go wrong , under the same shear strain , the shear stress is one-tenth of the paper’s result. Through Analysis, I found that Problems appeared in the minimization , the dislocation moved (plastic deformation) during the minimization ,even the strain is still very small(elastic state), in the other word ,one part of the strain I add on the system turn to the plastic strain ,so the stress (which is relate to the elastic strain) has become smaller.
How can I avoid this dislocation movement during the minimization ,which is clearly not make sense
#------------------------LOOP-----------------------------------------------------------------------------
label loading
variable i loop 10
variable strain equal “v_i*0.002”
variable iter equal ${i}
print “iteration times, iter: ${i}”
shell cd static_203_bigstrain_test6
#--------------------------------MINIMIZE---------------------------
displace_atoms down move 0 0 0.23 units box
displace_atoms up move 0 0 -0.23 units box
dump minimize_dump all custom 1000 mini*.${i}th.static id type x y z c_new1
minimize 0.0 0.0 2000 20000
undump minimize_dump
#--------------------------------DYNAMICE RUN---------------------------
dump dynamic_dump all custom 50000 loop*.${i}th.static id type x y z c_new1 f_5
velocity mobile create 30.0 4928459 dist gaussian
fix 3 all nve
fix 2 mobile temp/rescale 10 15.0 15.0 0.5 0.1
reset_timestep 0
fix print mobile ave/time 1 1000 50000 c_mytemp v_strain v_sigma_xz v_force_z1 v_force_z2 v_new_zz v_new_xz file INFORMATION${i}.txt
timestep 0.001
run 50000
undump dynamic_dump
unfix print
shell cd …
next i
jump shear2.data loading