# Doubt in input of experimental data for viscoelasticity

Hi Mr.Jorgen and all members

I am working on material Polypropelene . software: Ansys

I am considering Viscoelastic property.In that the experiment (i thought)required to be done is either 1 or 2

1.Tensile test relaxation data (strain is fixed and stress varies)

2.Creep Test(stress fixed strain varies)

CASE 1:

If I consider the relaxation data i will calculate the shear modulus by dividing modulus by 3

Using this data i want to apply in PRONY (shear response) in Ansys.

I know only this approach suggest me regarding other approaches(Maxwell,curve fitting)

CASE 2: I dont know how to approach this in Ansys

Please Help me in choosing the right way.

The easiest way is to use CASE 1: a stress relaxation experiment.

Note that PP is only linear viscoelastic at small strains.

-Jorgen

Thank you jorgen

Case 1: Yongs modulus and poissons ratio as input parameters,

case 2: Giving young modulus, poissons ratio and prony series data for pp at ROOM Temperature

The results from case 1 and case 2 will it be same or not

Please explain me.

hi

i used the ptfe material. I have taken tension relaxation data avaialable in this site .I claculated the shear modulus and used the curve fitting technique for viscoelastic(input is shear modulus versus time). I applied a displacement of 2 mm( as load) and got the results.The result obtained from taking viscoelastic and only elastic(youngs modulus,poissons ratio) giving same answer . This should not be happen according to my knowledge ......please suggest anything

You are right that a linear elastic material model should not give the same result as a linear viscoelastic material model. They only give the same results if the viscoelastic parameters are selected such that the viscous effects are not influencing the results.

-Jorgen

In the data i considered(taken from your site) is at room temperature i think so.

I am thinking that if i do the experiment at 45 to 100 degrees then the data should be incorporated .Then the results will differentiate i think so the viscous effects come into picture

i have another doubt that time history pricessor come intoexistence or not

Is the load application gone wrong or any other way of giving .............please suggest me

Performing additional experiments sounds like a great idea.

-Jorgen

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