Ductile Damage evolution in Abaqus (02 - Effect of Fracture strain on Element deletion)

This is the 2nd video of Ductile Damage evolution in Abaqus. In this video I discussed the Effect of Fracture strain on Element deletion and common mistakes made by user.
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[@sejong4672]

Thank you for your educational video. I look forward to seeing the next video!!

[@NarendraBhandava]

very nicely explained in both videos.

[@user-xj1zl3xp1k]

thank you for the video. I want to ask or rather confirm, based on Abaqus online documentation, fracture strain is equivalent to fracture strain at damage initiation. So, the fracture strain is not from zero point to the plastic strain at failure (ephsilon, pl, f), but from zero point to the equivalent plastic strain at the onset of damage (ephsilon, pl, 0). But in the video 3:19, you mention that fracture strain is from zero to plastic strain at failure (ephsilon, pl, f).

[@simtech0598]

Dear,
Damage initiation is the point from where fracture starts. But its value can certainly increase till the complete fracture. I think you misinterpreted the abaqus documentation. Please check again.

[@knir7145]

@@simtech0598 Hello, do you mean that the equivalent plastic strain (onset of damage, "ephsilon, pl, 0") changes when the element deforms?

[@praveenanand852]

Hello sir, you were about to start ABAQUS tutorial session in April.....I would like to be a part of that, pl let me know yhe details

[@simtech0598]

Dear,
No such plan in this month.
Please join telegram and Facebook group (link is in video discription) so any upcoming batch information will be update there.

[@hoslis5446]

Do you mean by plastic strain the elongation at break? Is the fracture strain then the value of elongation at break related to UTS or is the value where the Fracture strength of the material is reached?

[@veeturivarun5201]

How do we calculate damage evolution in terms of energy??.... I have taken the area under stress displacement curve from damage initiation to full damage region...excluding the characteristic length...is this the right approach??... Kindly guide me...

[@landrytim8595]

fracture strain is the intersection of a linear function with the slope of the elastic modulus and the ultimate stress, so it has to be lower than the strain corresponding to the ultimate stress

[@simtech0598]

No dear,
Watch carefully.

[@hnrwagner]

@@simtech0598 do you have a reference for this claim ? according to the abaqus user manual, the fracture strain is defined as the equivalent plastic strain at damage initiation. you seem to confuse it with the failure strain in a stress strain diagram. here is another quote from the abaqus user manual:
The ductile criterion is a phenomenological model for predicting the onset of damage due to nucleation, growth, and coalescence of voids. The model assumes that the equivalent plastic strain at the onset of damage,
is a function of stress triaxiality and strain rate.

[@simtech0598]

In the figure
σy0
and
ε_pl_0
are the yield stress and equivalent plastic strain at the onset of damage, and
ε_pl_f is the equivalent plastic strain at failure; that is, when the overall damage variable reaches the value D=1
abaqus-docs.mit.edu/2017/English/SIMACAEMATRefMap/simamat-c-damageevolductile.htm

[@tao1763]

@@hnrwagner Hello Dr. Wagner, I am confused by the definition of fracture strain. Can you please explain it a little more? Many thanks

[@knir7145]

@@simtech0598, Dear friend, I'm with @hnrwagner. The Abaqus online documentation says that the Johnson-Cook damage model (empirical formula dominated by d1-d5) calculates the failure strain corresponding to the equivalent plastic strain at the onset of the damage, not the equivalent plastic strain at the point of final fracture. Meanwhile,
The original statement of the document, "The value of the equivalent plastic strain at failure,(ε, pl,f), depends on the characteristic length of the element and cannot be used as a material parameter for the specification of the damage evolution law.", also indicates this view((ε, pl,f) is determined by the failure strain calculated through Johnson-Cook damage model and displacement at failure or fracture energy).

[@MrGabry83]

Sorry, but if i want to see the ramp (1-D)E in plot strain-stress, how cai i do?

[@simtech0598]

Dear u need to plot S-S curve only.

[@MrGabry83]

@@simtech0598 for exemple, s11-LE11?

[@kikinano5830]

Please how find the stress triaxiality and strain rate

[@simtech0598]

Dear,
For stress triaxiality you need to perform couples of experiment on set of predefined shape... there also analytical methods are available...like for round bar, round bar with notch etc.
With the help of optimization technique applied on these data point you can find a relationship for strain triaxiality.
For lower Strain rate you can use standard tension test machine. For higher strain rate the split Hopkinson bar technique is often used (10^2-10^3 /s) and with some special experimental setups, strain rates can reach up to 10^4 /s.

[@kikinano5830]

@@simtech0598 i have exemple of aluminum 2024 t3

[@simtech0598]

Dear,
I don't have data for your material. You need to find out releted research article or contact to material distributor or need to conduct experiment by yourself.

[@kikinano5830]

@@simtech0598 thunks 😊

[@landrytim8595]

can you please share the inp file of this?

[@simtech0598]

Dear,
I cannot share file..files are available only for members.