FISH function for plasticity state

FLAC
1

Hi all,

Using FLAC v.8, I am trying to write a fish function to associate zero cohesion and tensile values to all the zones “currently at yield in shear and/or volume” (i.e., state = 1) or “currently at yield in tension” (i.e., state = 3). This is the function:

define failure
    loop i (1, izones)
        loop j (1, jzones)
            if z_state(i, j) = 1 then
                cohesion(i, j) = 0
                tension(i, j) = 0
	    endif
	    if z_state(i, j) = 3 then
                cohesion(i, j) = 0
                tension(i, j) = 0
	    endif
        end_loop
    end_loop
end

The function is read by my script but does not seem to make any changes in terms of cohesion and tensile values for the zones with state = 1 or 3.

Would anyone be able to help me?

Thank you,

2

Probably your zones have more than one specific state and the numbers 1 or 3 never happen

3

Hi msepu, and thank you for your reply!

Honestly, it doesn’t seem that the zones have more than one specific state (at least in terms of visual observation):

STATE PLOT:

Screenshot 2024-11-05 143238
Screenshot 2024-11-05 143238934×789 73.2 KB

COHESION PLOT

coh
coh943×795 73.2 KB

GRID + PLASTICITY INDICATOR PLOT

num
num952×796 47.8 KB

Do you think the FISH function I wrote is correct?

Thank you,

4

There is no ‘z_state()’ fish intrinsic function, you either use state(i,j) or z_prop(i,j,‘state) for CPP constitutive models to access the ‘state’ value. And use z_prop(i,j, ‘cohesion’) and z_prop(i,j,’ tension’) to assign new values.
Check this topic: Use z_model(),z_prop() and z_group(). to access model and properties

1 Like
5

As we can see, there is no different state in your model. But as Jwang said z_state does no exist in flac.

6

Thank you jwang.

Even by modifying the function following your advice (both using state(i, j) and z_prop(i, j, ‘state’)), nothing seems to change. I also tried the function on another project with a different geometry and problem. I’m using a simple Mohr-Coulomb model.

define failure
    loop i (1, izones)
        loop j (1, jzones)
	  if model(i,j)#1
            if state(i, j) = 1 then
               z_prop(i, j, 'cohesion') = 0
               z_prop(i, j, 'tension') = 0
	    endif
	    if state(i, j) = 3 then
               z_prop(i, j, 'cohesion') = 0
               z_prop(i, j, 'tension') = 0
	    endif
	  endif
       end_loop
    end_loop
end

Do you may have any other suggestions?

Here you can find a demo of the project on which I’m working:

Thank you,

7

try the following updated code, MC is a built-in model(not C++ model), you have to use state(i,j) and cohesion() and tension().

define failure
loop i (1, izones)
loop j (1, jzones)
if model(i,j)#1
if state(i,j) = 1 then
cohesion(i,j) = 0
tension(i,j) = 0
endif
if state(i,j) = 3 then
cohesion(i,j) = 0
tension(i,j) = 0
endif
endif
end_loop
end_loop
end
failure

8

Thank you jwang!
Seems that the function is starting to work…

However, while for cohesion values I have no problems (i.e., cohesion = 0 is assigned to all zones currently at yield in shear and/or vol)(Figure 1), for tension values the function seems to associate null values even to the zones currently not at yield but has been in the past (Figure 2). How is it possible?

FIGURE 1

cohesion
cohesion1099×795 77.6 KB

FIGURE 2

tension
tension1101×795 75.4 KB

Plastic state indicator numbers are referred to pag. 1-148 of the Command Reference Manual.

Thank you so much for your help!

9

For tension, you may check if the tension is already set to zero prior to the fish function. For MC model, once the zone has tension failure, the tension strength will be set to zero automatically by the code.

10

Thank you jwang, your help is always precious and essential!