When we use the MinMax material and the “other” material of the command (that is called until it fails) is for instance a bilinear or trilinear Hysteretic curve, does it mean that after the strain reaches the ending point of the hysteretic curve then the material suddenly acts like it has a zero stiffness and develops infinitely strains while the stresses are zero?
The two options “$minStrain” and “$maxStrain”, do they concern the case that the user wishes the material’s “new behavior” to restart from a specific value and to end to a specific value of strain?
MinMax material
Moderators: silvia, selimgunay, Moderators
Re: MinMax material
yes it's as if the material fractured (though the other material itself does not know it).
no. if you provide a min and max then if the material hits any strain outside these values it is considered gone, fractured, or whatever you want to call it.
no. if you provide a min and max then if the material hits any strain outside these values it is considered gone, fractured, or whatever you want to call it.
Re: MinMax material
O.k, thank you.
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wuhaoshrek
- Posts: 122
- Joined: Tue Oct 28, 2008 4:01 am
Re: MinMax material
fmk wrote:
> yes it's as if the material fractured (though the other material itself
> does not know it).
>
> no. if you provide a min and max then if the material hits any strain
> outside these values it is considered gone, fractured, or whatever you
> want to call it.
Hi Frank,
I just come across a problem. I used Steel02 material for truss element to model post-tensing bar, and I set wrap the material with a MInMax material with maximum strain to be 0.01(PT fracture at 1% strain). I used "uniaxialTest" command to firstly test the stress-strain of the material, and it works just fine. However, when I run the dynamic model, and check the stress-strain again, then I found the material fracture until the strain goes to 0.014, rather than 0.01. I used fiber section (with only 1 fiber) for corotTrussSection element to model PT, and use "recorder Element -file $dataDir/PT_Story1.out -time -ele 11 21 31 41 section fiber 0. 0. $IDPT stressStrain" to recorder the stress-strain of the material. It seems very strange the material got fractured until it hits a higher strain value than that I specified in MinMax. Since I can only record the strain of the material in this way, I can't double check using recorder -element force command. I can't explain why it is like this. Do you have any idea why? Thank you.
> yes it's as if the material fractured (though the other material itself
> does not know it).
>
> no. if you provide a min and max then if the material hits any strain
> outside these values it is considered gone, fractured, or whatever you
> want to call it.
Hi Frank,
I just come across a problem. I used Steel02 material for truss element to model post-tensing bar, and I set wrap the material with a MInMax material with maximum strain to be 0.01(PT fracture at 1% strain). I used "uniaxialTest" command to firstly test the stress-strain of the material, and it works just fine. However, when I run the dynamic model, and check the stress-strain again, then I found the material fracture until the strain goes to 0.014, rather than 0.01. I used fiber section (with only 1 fiber) for corotTrussSection element to model PT, and use "recorder Element -file $dataDir/PT_Story1.out -time -ele 11 21 31 41 section fiber 0. 0. $IDPT stressStrain" to recorder the stress-strain of the material. It seems very strange the material got fractured until it hits a higher strain value than that I specified in MinMax. Since I can only record the strain of the material in this way, I can't double check using recorder -element force command. I can't explain why it is like this. Do you have any idea why? Thank you.
Re: MinMax material
it shouldn't .. are there recorded steps between the .01 and .014?
look at the source code for MinMax (it is really quite simple (what you care about are setTrialStrain() method):
http://opensees.berkeley.edu/WebSVN/fil ... terial.cpp
look at the source code for MinMax (it is really quite simple (what you care about are setTrialStrain() method):
http://opensees.berkeley.edu/WebSVN/fil ... terial.cpp
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wuhaoshrek
- Posts: 122
- Joined: Tue Oct 28, 2008 4:01 am
Re: MinMax material
fmk wrote:
> it shouldn't .. are there recorded steps between the .01 and .014?
>
> look at the source code for MinMax (it is really quite simple (what you
> care about are setTrialStrain() method):
>
> http://opensees.berkeley.edu/WebSVN/fil ... terial.cpp
Hi Frank,
Because I set a initial strain for the original material(roughly 0.004), so when I use the uniaxial material test to test the minmax material, it started with 0 strain corresponding to a initial stress value, and the material get fracture at a strain value 0.01. However in the dynamic analysis, the material started with initial strain (not 0 strain) and correspond to a same initial stress. So when the maximum strain value(0.01) in the minmax command actually developed a fracture value equal to 0.004+0.010=0.014. I think the problem is with initial strain, the bound value in the minmax command refers to the strain value excluding the initial strain. That's why it happened like this. Right?
> it shouldn't .. are there recorded steps between the .01 and .014?
>
> look at the source code for MinMax (it is really quite simple (what you
> care about are setTrialStrain() method):
>
> http://opensees.berkeley.edu/WebSVN/fil ... terial.cpp
Hi Frank,
Because I set a initial strain for the original material(roughly 0.004), so when I use the uniaxial material test to test the minmax material, it started with 0 strain corresponding to a initial stress value, and the material get fracture at a strain value 0.01. However in the dynamic analysis, the material started with initial strain (not 0 strain) and correspond to a same initial stress. So when the maximum strain value(0.01) in the minmax command actually developed a fracture value equal to 0.004+0.010=0.014. I think the problem is with initial strain, the bound value in the minmax command refers to the strain value excluding the initial strain. That's why it happened like this. Right?
Re: MinMax material
yes.