Running the model in loop with different co-eff of friction.

[ShaileshFle]

Hello,
I am trying to extract few results (elemental pressure) with different co-eff of friction. I am able to do it with co-eff of friction in the created model but when I change the co-eff of friction I am not getting answer. Below is the code, can someone help me with this.

from ansys.mapdl.core import launch_mapdl
import os

def mu_changer(all_elem, mu):
    mapdl.prep7()
    mapdl.mp('MU','2', mu)
    for i in range(len(all_elem)):
        j = int(all_elem[i][0])
        mapdl.mpchg('2', str(j))
    
    mapdl.finish()

path = os.getcwd()

mapdl = launch_mapdl(run_location = path + "\X_Ansys_Pymodel_Co-ff_of_friction")

mapdl.clear()
_ = mapdl.input(r"model1_input09.txt")

for mt in range(3): 
    all_mu = [0.15, 0.3, 1, 0]
    mu_nxt = all_mu[mt+1]
    print("Calc for mu: ", all_mu[mt])
    Pres_list = []
    list_elements_ids = []
    mapdl.allsel()
    mapdl.finish()
    mapdl.slashsolu()
    mapdl.outres('erase')
    mapdl.outres('all', 'all')
    for i in range(1,5):
        mapdl.time(i)
        mapdl.solve()
    mapdl.finish()

    mapdl.post1()
    for i in range(0,5):
        mapdl.set(i)
        mapdl.esel('s','ename','',174)
        mapdl.nsle()
        list_elements_ids = mapdl.presol('nmisc',41).to_list()
        mapdl.allsel()

        for id in list_elements_ids:
            pressure = mapdl.get_value('elem',id[0],'smisc',13)
            Pres_list.append([i, int(id[0]), "{:.2e}".format(pressure)])

    Pres_list = sorted(Pres_list, key=lambda x: x[1])

    Coo_Elem = []
    for id in list_elements_ids:
        x = mapdl.get_value('elem',id[0],'CENT','X')
        y = mapdl.get_value('elem',id[0],'CENT','Y')
        z = mapdl.get_value('elem',id[0],'CENT','Z')
        Coo_Elem.append([int(id[0]), x, y, z])

    file_name = "Master_list_Steps_"+ str(all_mu[mt]) +".txt"

    Master_list = []
    for j in range(len(list_elements_ids)):
        temp = []
        temp.append(int(list_elements_ids[j][0]))
        for i in range(len(Pres_list)):
            if Pres_list[i][1] == int(list_elements_ids[j][0]):
                temp.append(Pres_list[i][2])
        temp.append(Coo_Elem[j][1])
        temp.append(Coo_Elem[j][2])
        temp.append(Coo_Elem[j][3])
        Master_list.append(temp)

    with open(file_name, "w") as file:
        file.write("TS  " + '\t' + '\t' + '\t' + '\t' + '\t' + '\t' + '\t' + "0.000000"+ '\t' + "1.000000"+ '\t' + "2.000000"+ '\t' + "3.000000"+ '\t' + "4.000000" + '\n')

        file.write('\n' + "#Presure" + '\n')
        for item in Master_list:
            file.write("#" + str(item[0]) + '\t' + str(round(item[31], 2)) + '\t'  + '\t' + str(round(item[32], 2))
			+ '\t'  + '\t' + str(round(item[33], 2)) + '\t'  + '\t' + item[1]
			+ '\t' + item[7] + '\t' + item[13] + '\t' + item[19] + '\t' + item[25] + '\n')

    print(len(Master_list))
    print("Done")    

    mapdl.finish()

    mu_changer(list_elements_ids, mu_nxt)

[mikerife]

Hi @ShaileshFle Can you please correct your posting by enclosing the PyMAPDL code in tick marks ( ```). These are tick marks on the same key as the tilde (~) and not single quotes. I don't think the spacing is correct in the listing, and spacing is very important! When writing the comment you can use:

```python
python and/or PyMAPDL code
```

And what do you mean that you are not getting an answer. You are not getting any answer i.e. the results don't change? Or something else?

[ShaileshFle]

Hello,
I mean I am getting an answer but its zero always, even if I change co-eff of friction from 0.15 to 0.16, the elemental pressure value becomes
New Text Document.txt
Code.txt
some constant throughout the element for 2 load step and after that it just becomes 0, and the value remains same regardless of the mu. For example if I take mu = 0.16 or 0.3, the output will be same for the second loop and similarly for 3rd loop, which doesn't look plausible.

I have attached the output file and the code for your reference.

[germa89]

@ShaileshFle

You haven't attached the model1_input09.txt input file which might be important.

Regardless, it seems to me that in the first iteration you don't fix MU, hence whatever you have in the simulation might be moving freely, hence the big displacement in the first iteration.

Later you change the material id 2, to have MU different than zero in later loops. Maybe the force you are using is not strong enough compared to the friction. I would probably set a veeery low MU (i.e. MU=0.001) and see if you are having the expected results or not.

[ShaileshFle]

model1_input09.txt

Hi, I have attached the file. While creating the model I have already given it a mu = 0.15 and hence I am not changing its value in the first loop. So at the end of first loop the mu value is changed, and it is used for the second loop. So I think it should match

[mikerife]

@ShaileshFle So a few observations. There is nothing in the model that would create contact pressure. The forced movement in in the +/- X direction whereas the pressure would be in the Z. And the two parts are just touching. Is there meant to be some other load that would cause (contact) pressure between the two parts?

Generally this type of frictional contact model should be run with large deformations turned on.

You may want to switch the target/contact side so that the contact side is always in contact.

Mike

[ShaileshFle]

Hello, then how am I getting the values of elemental pressure in first loop? And why is the value changing in the second loop with the same co-eff of friction. Is the logic of changing the co-eff of friction correct? Is there any way to cross check if the applied co-eff is acting on the surface?

[mikerife]

@ShaileshFle getting very small, on the order of 1E-10, values for pressure does not constitute having an contact pressure in the normal sense. Frictional contact with sharp corners can lead to a little bit of "snagging" of the contact. Which happens here and the contact pressure changes. But still the absolute value of contact pressure is still essentially zero.

Delete the UZ=0 condition on the sliding block and replace with a applied pressure.

Well, you will also need to change the "item" in the loop writing the files as there are not =>31 items in the list. Try this:

from ansys.mapdl.core import launch_mapdl
import os

def mu_changer(all_elem, mu):
    mapdl.prep7()
    mapdl.mp('MU','2', mu)
    for i in range(len(all_elem)):
        j = int(all_elem[i][0])
        mapdl.mpchg('2', str(j))
    
    mapdl.finish()

path = os.getcwd()
mapdl = launch_mapdl(run_location = path) 

mapdl.clear()
_ = mapdl.input(r"model1_input09.txt")

mapdl.nsel('s','loc','z',-2)
mapdl.ddele('all','uz')
mapdl.sf('all','pres',10)
mapdl.allsel()

for mt in range(3): 
    all_mu = [0.15, 0.3, 1, 0]
    mu_nxt = all_mu[mt+1]
    print("Calc for mu: ", all_mu[mt])
    Pres_list = []
    list_elements_ids = []
    mapdl.finish()
    mapdl.slashsolu()
    mapdl.outres('erase')
    mapdl.outres('all', 'all')
    mapdl.nlgeom('on')
    mapdl.nsubst(10,10,1)
    for i in range(1,5):
        mapdl.time(i)
        mapdl.solve()
    mapdl.finish()
    mapdl.post1()
    for i in range(1,5):
        mapdl.set(i)
        mapdl.esel('s','ename','',174)
        mapdl.nsle()
        list_elements_ids = mapdl.presol('nmisc',41).to_list()
        mapdl.allsel()

        for id in list_elements_ids:
            pressure = mapdl.get_value('elem',id[0],'smisc',13)
            Pres_list.append([i, int(id[0]), "{:.2e}".format(pressure)])

    Pres_list = sorted(Pres_list, key=lambda x: x[1])

    Coo_Elem = []
    for id in list_elements_ids:
        x = mapdl.get_value('elem',id[0],'CENT','X')
        y = mapdl.get_value('elem',id[0],'CENT','Y')
        z = mapdl.get_value('elem',id[0],'CENT','Z')
        Coo_Elem.append([int(id[0]), x, y, z])

    file_name = "Master_list_Steps_"+ str(all_mu[mt]) +".txt"

    Master_list = []
    for j in range(len(list_elements_ids)):
        temp = []
        temp.append(int(list_elements_ids[j][0]))
        for i in range(len(Pres_list)):
            if Pres_list[i][1] == int(list_elements_ids[j][0]):
                temp.append(Pres_list[i][2])
        temp.append(Coo_Elem[j][1])
        temp.append(Coo_Elem[j][2])
        temp.append(Coo_Elem[j][3])
        Master_list.append(temp)

    with open(file_name, "a") as file:
        file.write("TS  " + '\t' + '\t' + '\t' + '\t' + '\t' + '\t' + '\t' + "0.000000"+ '\t' + "1.000000"+ '\t' + "2.000000"+ '\t' + "3.000000"+ '\t' + "4.000000" + '\n')

        file.write('\n' + "#Presure" + '\n')
        for item in Master_list:
            file.write("#" + str(item[0]) + '\t' + str(item[1]) + '\t'  + '\t' + str(item[2])
			+ '\t'  + '\t' + str(item[3]) + '\t'  + '\t' + str(item[4])
			+ '\t'  + '\t' + str(item[5]) + '\t' + str(item[6]) + '\t' + str(item[7]) + '\n')

    print(len(Master_list))
    print("Done")    

    mapdl.finish()

    mu_changer(list_elements_ids, mu_nxt)