Shear stress in a polymer under pressure
Shear stress in a polymer under pressure
(OP)
I am trying to design a polymer(thermoplastic) ring under a uniformly loaded fluid pressure at high temperature for an extended period of time to resist deformation into the gap between the gland and piston. What are the contitutive equation I need to be using to predict geometric parameters for the rings.
Any direction to follow or reference to literature will be helpful.
Any direction to follow or reference to literature will be helpful.





RE: Shear stress in a polymer under pressure
You also need to check whether the fluid interacts with the polymer, for example by plasticizing it.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: Shear stress in a polymer under pressure
RE: Shear stress in a polymer under pressure
The only data I ever saw was published by ICI when they existed.
It was all based on extensive test results, not calculation.
Bayer and Akzo may also have published some years ago, but such data has tended to be withdrawn as the marketing experts tended to decide that complex technical data scared people off.
Regards
Pat
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RE: Shear stress in a polymer under pressure
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: Shear stress in a polymer under pressure
RE: Shear stress in a polymer under pressure
Forgot that!
RE: Shear stress in a polymer under pressure
Your formula does not take time into account which is the only difficult aspect.
Regards
Pat
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RE: Shear stress in a polymer under pressure
These are nowadays much like unicorn droppings, but if you can contact the "white coat" department of your material supplier, you may get lucky!
No, it is definitely NOT!! You can only work from empirical data.
Patprimmer summed it up in his post of 16th Aug 21:24.
As for the original query
A: There ain't one!
You might get lucky....
H
www.tynevalleyplastics.co.uk
RE: Shear stress in a polymer under pressure
Isochronous was the term I was trying to remember.
I actually have them somewhere for most of the OLD ICI range.
Regards
Pat
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RE: Shear stress in a polymer under pressure
These constitutive models typically require several material parameters, which should be calibrated from experimental stress-strain curves at different loading rates, and at the temperature of interest (isochronous data is more convenient but not required). Unless your geometry is very simple, it's better to perform a finite element analysis using the calibrated constitutive models.
You can find more details and discussions on these material models in PolymerFEM (http://www.polymerfem.com) which is a specialized forum on modeling of polymers developed and maintained by one of my coworkers Dr. Jorgen Bergstrom.
Nagi Elabbasi
Veryst Engineering