EDEM Particle Explosions
Best Answer
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Jake Kim_21578 said:
Oh ok! that sounds good! So I am a little confused, if they used that young's modulus in the paper, its fine for me to reduce it because the bulk material behavior wont be severely impacted?
Hi Jake, that is it. Generally, as described in https://community.altair.com/community/en?id=community_blog&sys_id=593445c11b2f6810c4dfdbd9dc4bcb06 from tests conducted and general experience modelling materials using EDEM as long as the Shear modulus is kept over 1e7 (Young Modulus of 2.5e7) the material behaviour will be maintained or there will be no significant difference in a case like this where the main thing will be the flow of the powder for the spreading.
It is worth noting that for high stress systems where stiffness of the material can have a significant impact on the key behaviour to model it is worth keeping it higher (even if potentially not at the same value as the actual material property) and adjusting it during the calibration process with a test that captures the behaviour of interest for the full size application.
If you want to confirm how low you can go with the Shear Modulus value, you could do a sensitivity study decreasing the shear modulus to check if you achieve the same material behaviour and what speed up you get.
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Altair EmployeeAnswers
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Hello Jake,
On first impression, the time-step seems like it could be reasonable for stability. However the first thing I would look at tweaking is the Young's Modulus. That value seems to be quite high for what normally would be use in DEM, making the particles very stiff and if they are under some stress this may be causing the explosions. Normally it is recommended to artificially reduce somewhat the Shear/Youngs Modulus value as it does not change significantly the bulk material behaviour and can also make the simulation faster. You can read more about this here: https://community.altair.com/community/en?id=community_blog&sys_id=593445c11b2f6810c4dfdbd9dc4bcb06
Hope that this helps.
Kind regards
Ignacio
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Hello Jake,
On first impression, the time-step seems like it could be reasonable for stability. However the first thing I would look at tweaking is the Young's Modulus. That value seems to be quite high for what normally would be use in DEM, making the particles very stiff and if they are under some stress this may be causing the explosions. Normally it is recommended to artificially reduce somewhat the Shear/Youngs Modulus value as it does not change significantly the bulk material behaviour and can also make the simulation faster. You can read more about this here: https://community.altair.com/community/en?id=community_blog&sys_id=593445c11b2f6810c4dfdbd9dc4bcb06
Hope that this helps.
Kind regards
Ignacio
Oh ok! that sounds good! So I am a little confused, if they used that young's modulus in the paper, its fine for me to reduce it because the bulk material behavior wont be severely impacted?
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Hello Jake,
On first impression, the time-step seems like it could be reasonable for stability. However the first thing I would look at tweaking is the Young's Modulus. That value seems to be quite high for what normally would be use in DEM, making the particles very stiff and if they are under some stress this may be causing the explosions. Normally it is recommended to artificially reduce somewhat the Shear/Youngs Modulus value as it does not change significantly the bulk material behaviour and can also make the simulation faster. You can read more about this here: https://community.altair.com/community/en?id=community_blog&sys_id=593445c11b2f6810c4dfdbd9dc4bcb06
Hope that this helps.
Kind regards
Ignacio
Is it also possible particle explosions are happening because when I first generated the particles I reduced the young's modulus greatly to speed up my simulation. Once I finished generating, I changed the young's modulus back up to 2.1GPa and then spread the powder.
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Jake Kim_21578 said:
Oh ok! that sounds good! So I am a little confused, if they used that young's modulus in the paper, its fine for me to reduce it because the bulk material behavior wont be severely impacted?
Hi Jake, that is it. Generally, as described in https://community.altair.com/community/en?id=community_blog&sys_id=593445c11b2f6810c4dfdbd9dc4bcb06 from tests conducted and general experience modelling materials using EDEM as long as the Shear modulus is kept over 1e7 (Young Modulus of 2.5e7) the material behaviour will be maintained or there will be no significant difference in a case like this where the main thing will be the flow of the powder for the spreading.
It is worth noting that for high stress systems where stiffness of the material can have a significant impact on the key behaviour to model it is worth keeping it higher (even if potentially not at the same value as the actual material property) and adjusting it during the calibration process with a test that captures the behaviour of interest for the full size application.
If you want to confirm how low you can go with the Shear Modulus value, you could do a sensitivity study decreasing the shear modulus to check if you achieve the same material behaviour and what speed up you get.
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Jake Kim_21578 said:
Is it also possible particle explosions are happening because when I first generated the particles I reduced the young's modulus greatly to speed up my simulation. Once I finished generating, I changed the young's modulus back up to 2.1GPa and then spread the powder.
This could also be a factor playing a role. Since the decrease in young's modulus will decrease the stiffness and the change in stiffness will affect suddenly the overlap on the particles. Doing a quick test modifying it mid-simulation also caused an explosion for me. Would be best to stick to what ever modulus you start with.
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