Questions and issues regarding Bonding V2 Model
Hi all,
i'm using the Bonding V2 approach to model the des-agglomeration of Carbon particles (0,3mm diameter). In theory i would expect if us a high value of normal and shear strength (max. 1e300 Pa) that no particles would break in my simulation at all. I want to use this as a base case to fine-tune the breakage after. Is this assumption correct? What could be wrong if i still see breakage occuring?
Secondly, i have issues when i post-process. I can not see broken bonds in post-processing. Bond status is either 0 or 1 but never 2. How do i know which bonds are broken? Also i can only make the bonds visable via the Contact tab but not via the Bonds tab. Also when exporting results data it shows me only the Bond status via the Contacts query not via the Bonds query. Again, how can i analyse the number of broken bonds?
Thank you!
Answers
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Hi Clemens,
Your approach is logical. By setting the Normal Strength and Shear Strength to a very large value you will prevent or greatly limit bond failure. Have a look at the bond status that for the Bonding V2 model is listed under Contact Information (It is only the legacy bond model that will populate information in the Bond Attributes-sorry for this as it is not logical). If you see any bonds with a status of 2 that means they have failed due to a critical stress being exceeded. If this is the case try to increase the critical strength values to a larger value. However, you could still see "broken" particles and have bond statuses of either 0 or 1. That would suggest that the bonds are failing due to separation distance. If this is the case I would suggest that you verify you have set your normal and shear stiffness sufficiently high that the critical normal or shear strength is exceeded before the particles are separated beyond their contact radii.
Please let me know if this addresses your issue!
Kind Regards,
Eric Veikle
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In addition to what i posted earlier, i tried several things but my meta-particles always shatter during the slightest impact.. Is there something special to keep in mind? Really struggeling to get anything working.
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Hmm, my own reply seems to have vanished. So i try again: I tested several things but my meta-particle agglomerates get smashed right away with slightest impact. Is there anything i have to keep in mind? primary particle diameter is 0.3mm. I use a timestep of 10% Rayleigh. I set a normal/shear stiffness of ~1e5 and normal/shear strength to 1e100. My particles shatter all the time...
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Clemens Lischka_20358 said:
Hmm, my own reply seems to have vanished. So i try again: I tested several things but my meta-particle agglomerates get smashed right away with slightest impact. Is there anything i have to keep in mind? primary particle diameter is 0.3mm. I use a timestep of 10% Rayleigh. I set a normal/shear stiffness of ~1e5 and normal/shear strength to 1e100. My particles shatter all the time...
Hi Clemens,
My first thought would be that your timestep is still too large at 10% Rayleigh. Can you share your EDEM deck with me so I can have a look? I will send you an email with an address for sharing the deck.
Kind Regards,
Eric
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Hi Clemens,
Thanks for sharing your simulation deck so that I could have a look.
Indeed with the parameters that you were using the timestep needed to be smaller for the bonded particles to be stable, a Rayleigh timestep of 1.5 to 0.5% was required. The maximum stable timestep is particularly sensitive to the bond stiffness (both normal and shear) for this simulation you were using a stiffness on the order of 1 e 11 N/m3. If you can reduce the stiffness to something on the order of 1e7 N/m3 then you will be able to increase your timestep up to 20% Rayleigh. However, if you just make that change you will see that the bonds between particles will fail, not due to the critical strength being exceeded but instead due the the particles separation exceeding the contact radius of the particle. To avoid this you can increase your contact radius from 6% larger than physical radius to 35% larger then the physical radius.
The strategy that I take when setting up the bond model is to set the stiffness as low as possible (to maximize the allowable timestep) while also maintaining a reasonable accuracy of the virtual particle in relation to the physical material. I start with a contact radius 1.2 times the physical radius and set the critical shear and normal strength high enough that the critical stress will be exceeded before the particles are separated beyond their contact radius.
I hope this will get you on your way with the bond model!
Kind Regards,
Eric
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Altair Employee