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Implementing flexural modulus
Posted 28 déc. 2009, 19:22 UTC−5 3 Replies
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Good day,
Material properties of plastics are generally reported with a 'flexural modulus' as opposed to Young's Modulus (Modulus of Elasticity, E) because there is not much of a linear region to a standard tensile stress-strain curve. The 'flexural modulus' is generally obtained by placing a known sample in a three point bending test rig and deforming the sample to a pre-specified value. Because this places portions of the sample in both tension and compression it of course is not directly transferable into a value for elastic modulus as used in COMSOL.
I'm curious how one might adapt a published flexural modulus to the COMSOL material parameters entry. Perhaps the capability is there but I've not noticed its availability.
Any advice would greatly appreciated.
Regards,
Marty
Material properties of plastics are generally reported with a 'flexural modulus' as opposed to Young's Modulus (Modulus of Elasticity, E) because there is not much of a linear region to a standard tensile stress-strain curve. The 'flexural modulus' is generally obtained by placing a known sample in a three point bending test rig and deforming the sample to a pre-specified value. Because this places portions of the sample in both tension and compression it of course is not directly transferable into a value for elastic modulus as used in COMSOL.
I'm curious how one might adapt a published flexural modulus to the COMSOL material parameters entry. Perhaps the capability is there but I've not noticed its availability.
Any advice would greatly appreciated.
Regards,
Marty
3 Replies Last Post 4 janv. 2010, 01:47 UTC−5
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Posted:
1 decade ago
Hi
Good thought.
Now, if you know rather precisely how the "flexural" modulus is obtained (the geometry and the deformation=main strain), and you have a rather good guess of the shape (polynomial development) of the stress strain curve and want to fix this curve in amplitude corresponding to the "measurement" then you have an inverse problem, as Niklas talks about in the Multiphysics Blog of August 2009.
This you can perfectly set up in COMSOL (by the way, I'm not so sure how this could be done in "older" FEM codes), there are several examples around in the doc and the model gallery.
Try it out, could be raher handy for those active with plastics to know how well or just better how to correct a flexural to an equivalent Young modulus, or just to confirm the acceptable correspondance
Good luck
Ivar
Good thought.
Now, if you know rather precisely how the "flexural" modulus is obtained (the geometry and the deformation=main strain), and you have a rather good guess of the shape (polynomial development) of the stress strain curve and want to fix this curve in amplitude corresponding to the "measurement" then you have an inverse problem, as Niklas talks about in the Multiphysics Blog of August 2009.
This you can perfectly set up in COMSOL (by the way, I'm not so sure how this could be done in "older" FEM codes), there are several examples around in the doc and the model gallery.
Try it out, could be raher handy for those active with plastics to know how well or just better how to correct a flexural to an equivalent Young modulus, or just to confirm the acceptable correspondance
Good luck
Ivar
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Posted:
1 decade ago
Good day Ivar,
Thanks for your thoughtful recommendations. You are of course correct the reported flexural modulus is very much sample geometry dependent. I'll attempt to follow through and if I have success I'll report back.
As always, many thanks for the advice.
Oh, what is the news regarding the 4.0 release?
Regards,
Marty
Thanks for your thoughtful recommendations. You are of course correct the reported flexural modulus is very much sample geometry dependent. I'll attempt to follow through and if I have success I'll report back.
As always, many thanks for the advice.
Oh, what is the news regarding the 4.0 release?
Regards,
Marty
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Posted:
1 decade ago
Hi
thanky for the kind words, just to make it clear, I'm NOT from COMSOL, I'm a Systems Engineer in a private high tech R&D company , but a fan of their multiphyiscs product, so I'm in the same state as you.
I'm also really waiting for V4, as I have 2 months with heavy modelling in front of me, and strict deadlines, and it would be so much easier with the new features, IF they are reliable ;)
Have a nice day
Ivar
thanky for the kind words, just to make it clear, I'm NOT from COMSOL, I'm a Systems Engineer in a private high tech R&D company , but a fan of their multiphyiscs product, so I'm in the same state as you.
I'm also really waiting for V4, as I have 2 months with heavy modelling in front of me, and strict deadlines, and it would be so much easier with the new features, IF they are reliable ;)
Have a nice day
Ivar