Dear Friends
As I know, the simple shear test is the common experimental to derive shear modulus of rubber at multiple shear strain level.
What could we obtain the shear modulus (G) for relaxation test for certain strain level?I need a single value of G at 100% strain level (for instance: G at 100% is 0.5 MPa).
Please give me information what method should I used, since the relaxation test data consist of stress vs time.
BR
Yudha Lesmana
Dear Yudha Lesmana,
I suppose that we cannot derive the shear/young modulus from stress vs time data, except you have the loading(strain) history during relaxation test.
But she stress value in the relaxation data is often expressed as normalized stress, in which the maximum value is 1 at t=0 second. In this case you don't find the real value of the stress.
Regards,
I have conducted the stress relaxation test so I have the data test. What kind method should I used?
WhAT could I obtain single shear strain value at certain strain level.
Is it a uniaxial tensile-relaxation test? If so, what you can estimate is only the Young modulus at any axial strain level. Then you can estimate the equivalent shear modulus. G=E/(2*(1+v)).
However, I don't think there is a suggested method to do conversion from axial strain to shear strain.
.
I carried out two stress relaxation test (Tension and shear).
OK, you said "we can estimate the young modulus at any strain level", what method should I used to get it? Prony series?
As I know, If we use prony series, we only derive the constants, relative modulus(Gi) and relaxation time constant. How to extract the single value of shear modulus (G)? If you have sample calculation it better for me. Thanks.
Hello Yudha. I don't know if I can help you! But as I could understand, you can extract the young modulus (E) from your tests. If you have an idea about your rubber compressibility degree you can estimate your poisson's ratio and find shear modulus (G) by the equation Ahmad said. If you don't have any idea you can perform a volumetric compression test and find the bulk modulus (K). So, you can find G by the following equation: (3K.E)/(9K-E).
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