Change material properties at a specified step

[Mohamedsayed]

Hell,

I want to change the material properties in my model at the third step.I know that i can use either USDFLD subroutine or *Field keyword option. Since i am not familiar with the USDFLD subroutine i chose the * field keyword. That is what i did

*Material, name=Material-1
*Elastic, dependencies=1
3e+06, 0.3, , 1.
300000., 0.3, , 2.
** where the first value of Young's modulus should be used in the first and the scond step, while the the second value should be used in the third step.

*Amplitude, name=step
0.,1.,1.,1.
*Initial conditions, type = field, variable = 1
name of node set,1
** since i want to change the Young's modulus in the third step
*step, name=step-3
.....
*field, variable=1, amplitude=step

But unfortunately it did not work, i do not know why, i read many posts about how to use * field variable to change the material properties, i read the manual. but i do not know why it did not work.
I wish any one send my the input file for a very simple model just one element and change the properties of that element at any load step.

I attached the input file, please help me
I spend almost 2 weeks to solve this problem
Thank you.
Mohamed

 

[IceBreakerSours]

You have not assigned the correct node set name to the field variable assignment keywords. The correct name is:

Part-1-1.Nall instead of Nall

because the node set Nall was defined in the Part module. Conversely, had the node set been defined in the Assembly module, Nall would have worked out just fine.

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[Mohamedsayed]

First of all, thank you so much for your advice.
I used the node set as you suggest, since i made this node set in the part module (Part-1-1.Nall) instead of Nall, but it did not work also.i.e., Young's modulus does not change in the second step.
I repeat the same model again, and make the node set in the Assembly module, so this time i can use Nall as the name of the node set,i still could not change Young's modulus in the second step.

I wish you have time and help me. I read the manual (predefined field) and read some posts.

Again, my objective is to change young's modulus in the second step. i defined young's modulus as function field variable, then i change this field variable in the second step using *field, variable=n option. i attached the input file, so you can check it again. Thank you in advance.

 

[IceBreakerSours]

Check the value of the field variable in the Viewer.

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[Mohamedsayed]

Could you please tell me how can i plot the value of the field output in the viewer, What i did is just checking the magnitude of the displacement at the the end of step1 and step2, since young's modulus should be smaller in second2 , hence the displacement should be bigger. but what i found is that, the displacement does not change, which gives indication that young's modulus does not also change. please correct me if i am wrong.

In the step module, i requested output for FV. but in the visualization module , i could not plot it.

So, please tell me how can i check the value of the field variable in the viewer.
Your suggestions and help are greatly appreciated. i am looking forward to hearing from you. Thank you so much.

 

[IceBreakerSours]

Will your reasoning work in both load and displacement control? Think about it. And you should read the CAE documentation regarding plotting field variables.

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[Mohamedsayed]

My model is under load control, so i believe that this reasoning should work,i.e., as the stiffness decreases the displacement increases. I am not sure about the displacement control.

I plotted the FV, i found that it is zero in both step one and two. I want to tell you that step one is solved in one increment as well as step two.

I sent you the input file, please run it and tell me what should i do to overcome this problem.

Thank you so much. Your suggestions are highly appreciated.

Thanks

 

[Mohamedsayed]

Hello

In Abaqus manual, section 33.6.1, It gives an idea about how to change Young's Modulus during the time step from and initial value 30E6 to final value 35E6. this is the idea.

"Define an initial condition to specify the initial value of field variable 1 as 1.0 for a node set. Then, define a predefined field variable in the analysis step to specify the value of field variable 1 as 2.0 for the node set. Young's modulus will vary smoothly over the course of the step as the field variable's value is ramped from 1.0 to 2.0 at all nodes in the node set".

*Material, name=Material-1
*Elastic, dependencies=1
**E, new, , FV1
30E6,.3, , 1
35E6,.3, , 2

** and then
*Amplitude, name=myAmp
0.,0.,1.,1.
*Initial condition, type=field, variable=1
name of the set, 1

*step, name=step-1
......
*Field, variable=1, amplitude=myAmp.
name of the set,2


I try to follow this idea on a very simple model, but it did not work.

I wish you help me and make a very simple model under uniaxial compression or tension , and send it to me.
thank you.

 

[IceBreakerSours]

Your file (working) is attached. Field variable changes as expected.

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[Mohamedsayed]

Hello Sir,

You mean my file is working? I cheeked the LE, and the U , at the end of step one and step two, they are the same, and since the model is under load control and the Modulus of elasticity should be smaller in the second step, so the displacement and LE should be bigger in the second step compared to the first step. so how come the file is working and the field variable changes as required. please give more details.

Thank you for your patience.

 

[IceBreakerSours]

How did you figure out the values of LE/U? You should try to find out how to plot XY data from ODB field output; check CAE manual for details.

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[Mohamedsayed]

I will give you an example, so you can understand me.

suppose you squeeze two materials under certain amount of load, one of them is stiff (high Young's modulus), while the other is not stiff (Low Young's modulus). You will find that the displacement in the soft material is bigger than the stiff material, right?

Now in my model, i am trying to decrease the stiffness in the second step, almost (1/100) of that in the first step, Hence the displacement at the end of step one should be smaller than that in step 2. but as i told you they are the same, which means that there is no change in stiffness in the second step.


I do not need to plot x-y curve, I can compare the values of the contour plots at the end of step one and step.

Thank you so much.
Your suggestions are appreciated.

 

[IceBreakerSours]

Check the attached image; both "displacement" and "stress" (at node # 85) change as the steps change.

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[Mohamedsayed]

Hello,

The graph you sent looks great, it seems that the stiffness changed in the second step as required. could you please send me the file that you run and got that results.

I run the model that i sent you whose name is (Job-1-sent-jop), and this is the x-y plot for the E2 at node 85. the strain is constant at the end of step i and step 2.

Thank you for your patience.

 

[Mohamedsayed]

Hello My friend
In the previous post i sent you only the E22, and make comments on your results, please read the previous post also. i think your input is different from my input file. Here i attached a graph for FV, E22 and the input file that i run and gave me the results that i sent you.

Thank you.

 

[IceBreakerSours]

Run the input deck that I uploaded for you.

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[Mohamedsayed]

Hello My friend

in a previous post you told me (Your file (working) is attached. Field variable changes as expected. ), I downloaded the file in that post, I run it and i did not see any thing new.However, the graph you sent looks great and reasonable. did you get this result from that input file that i am talking about. or changed the input file?

Send me that input file that you run and got that results please. I start to have doubt about my software!!!

Thank you very much.

 

[IceBreakerSours]

I am uploading the file again. And please do not blame the software!

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[Mohamedsayed]

Hello my friend,

I run the input file which you sent(Job-1-sent_jop). I checked the FV and E22 at node 85. please see the attached file.
I really do not know what is wrong. i can not find any explanation why your results are different from my results, although both of us run the same input file.

Please be patient for one more time. I know that i disturb you very much. forgive me.

Thank you so much

 

[Mohamedsayed]

Please read the previous post also. This Graph is the variation of the displacement with time. Check it please. all graphs resulted from the input file that you sent.

Thank you