Simple Creep/Slump Testing of a Cylindrical Part
Simple Creep/Slump Testing of a Cylindrical Part
(OP)
Hello, I'm trying to figure out how a part made from a viscoelastic thermoplastic material will deform with time. Is there a simple method to do this?
The problem can be simplifid to a 2-d state. I can obtain relevant material values for an analytical test, or if you can suggest a way to relate temperature to slump rate I could do a test at elevated temperature.
The part has the shape of a thick-walled pipe, adhered to an outside sleeve of a perfectly rigid support material. This part will be stored laying on its side, subjected only to the force of gravity. The problem is, the inner diameter part will tend to "float up" with the passage of time - and I was hoping to be able to predict the extent of this flow behavior at a given storage temperature and time span.
Thanks!
The problem can be simplifid to a 2-d state. I can obtain relevant material values for an analytical test, or if you can suggest a way to relate temperature to slump rate I could do a test at elevated temperature.
The part has the shape of a thick-walled pipe, adhered to an outside sleeve of a perfectly rigid support material. This part will be stored laying on its side, subjected only to the force of gravity. The problem is, the inner diameter part will tend to "float up" with the passage of time - and I was hoping to be able to predict the extent of this flow behavior at a given storage temperature and time span.
Thanks!





RE: Simple Creep/Slump Testing of a Cylindrical Part
Just on a feeling basis I would be surprised to find the hole in a polymer pipe moving up due to gravity. I don't think that should be fast enough to be noticeable for any high molecular weight polymer.
RE: Simple Creep/Slump Testing of a Cylindrical Part
Now, that makes no sense, if the way to use a_T is divide the time ordinate in the curve fit of your original experimental data. The temperature of interest plot ends up "compressed in time" WTR to the elevated temperature test, while the expected behavior would result in a "stretched in time" plot.
Am I using a_T correctly? Thanks!
RE: Simple Creep/Slump Testing of a Cylindrical Part
Can you do a google search for using the WLF? I am sure there are links to polymer courses that give examples to make things clearer.
RE: Simple Creep/Slump Testing of a Cylindrical Part
http:/
which describes how to modify the constants c1g and c2g used in the WLF equation to reflect a specific reference temperature other than glass transition temperature. Page 48 of the document refers to Neilsen and Landel (Mechanical Properties of Polymers and Composites, Marcel Dekker, 1994) to get:
c1 = (c1g*c2g)/(c1g+Tref-Tg)
c2 = c2g+Tref-Tg
Thanks for your help again!
RE: Simple Creep/Slump Testing of a Cylindrical Part