Plastic strain in elastic material

[fabricix]

I am simulating a block of elastic material applying a force over an elasto-plastic material.

During the simulation I observe plastic strains in booth materials:

Why is there an effective plastic strain in the block material, if this material is elastic?

Note: if I define all materials as elastic, the plastic strain is null in all particles.

This is the input file:

! title
mpm3d 3d-cube

! units' comments
! Unit: m  kg  N  s  Pa

! number of components (2=contact on, 1=contact off)
nbco 1

! number of body
nbbo 2 

! number of particles
nbmp 4008

! number of materials
nmat 2

! background grid
spx   0.0   10.0
spy   0.0   10.0
spz   0.0    8.0

! cell grid dimension
dcell 1.00

! dynamic relaxation damping
drda

! critical time step fraction
dtscale 0.2

! simulation time
endtime 0.5

! gimp scheme
gimp

! stress update scheme
usl on

! Jaummnn stress rate correction
jaum on

! paraview results
para

! time interval for write results
outtime 0.01

! grid boundary condition
!      x0  xn  y0  yn  z0  zn
fixed  2   2   2   2   1   2

! soil
Particle block 1 
!matID, p_mass, p_spacing, ox, oy, oz, nx, ny, nz
1 225.00 0.50 0 0 0 20 20 10

! block
Particle block 2
!matID, p_mass, p_spacing, ox, oy, oz, nx, ny, nz
1 225.00 0.50 4.5 4.5 5 2 2 2

! material model
material
1      dpm    1800.0    20e6      0.3        0.4105731305  4402.384598   0.0    10.72e3   
!1      elas   1800.0    20e6      0.3   
2      elas   1800.0    20e6      0.3   

! 100 kPa in -Z
load
body 2  0.0 0.00 -12.5e3
endl   

! end of the input file
endi

[ZhouRuopu]

you didn't apply the elastic material into the bock. Please modify your code on line 63 in your input file, and you just need to change the matID to 2 instead of 1, which represent the elastic material. This is the modified simulation.

[fabricix]

Sure. The material Id of the block 2 must be 2 but in the code is defined as 1. Thanks.

! block
Particle block 2
!matID, p_mass, p_spacing, ox, oy, oz, nx, ny, nz
2 225.00 0.50 4.5 4.5 5 2 2 2