How to define paramaters of perzyna viscoplastic model?

[zerrouki]

Hello everyone
i want to model viscoplasticity using Ansys APDL, Perzyna and Peirce or Anand
model offer us to do this modeling, and each modèle Contains different parameters.
the question is: how to determine the parameters (if we can determine them experimentally, what is the concerned test "tensile test or creep").
thanks for help.

 

[Kevin McHugh]

You'll need an Instron for the tensile strength elongation, and yield. The same machine can test for creep, but you need an environmental chamber for temp control. Creep is cold flow of a material under strain at a given temperature.

 

[zerrouki]

hello
is it possible to determine these paramaters using tensile tests with different strain rate or by using the creep test ?
thank's for help.

 

[Kevin McHugh]

You can program the Instron for any strain rate within its capabilities, but strain rates affect yield, elongation at break. That is why there are ASTM methods for determining these parameters. Creep is done at constant strain. You can find physical properties of just about any resin in Modern Plastics data guidebook.

You can find elongation at 100%, elongation at break, elongation at yield, flexural modulus, and many other properties.

 

[zerrouki]

dear McHugh
the material to be tested is HDPE, the machine that can do this test is "Zwick Z100". how can I do the tests with different strain rates.
thanks

 

[Kevin McHugh]

Consult your machine's operation manual. I am not familiar with this machine. I've always used Instrons. Consult ASTM methods for setting machine's parameters.