Dear Mr. Kumar,

Start in reading this book:

ENGINEERING VISCOELASTICITY

David Roylance

Department of Materials Science and Engineering

Massachusetts Institute of Technology

Cambridge, MA 02139

October 24, 2001

Good luck

Ori

http://www.reading.ac.uk/web/files/maths/thesis_jing_final.pdf

http://archimed.uni-mainz.de/pub/2003/0084/diss.pdf

https://dasher.wustl.edu/chem478/reading/md-intro-2.pdf (see chapter 4)

http://www2.mpip-mainz.mpg.de/~duenweg/Public/minn.pdf

All these links are about MD calculation of polymer systems. The autocorrelation function can be fitted by a realxation time distribution (Laplace transform) - but in my opinion this is somewhat arbitrary. It is much better to simulate the correlation function itself - if possible. It telles more about the physics behind the process.

Theoretically it is possible to determine the relaxation spectrum from any strain controlled experiment (e.g. G(t), G'(omega), G"(omega)). The question is obviously how you are trying to determine the spectrum from this as it is an ill-posed problem and there are lots of different ways to get the relaxation spectrum.

However, it is not possible to determine the relaxation spectrum from any stress controlled experiment without a transformation of that experiment. E.g. you can transform J' and J" to G' and G" and then calculate the relaxation spectrum from those. For creep and creep recovery functions, the whole issue becomes more difficult and in this case it is better to calculate the retardation spectrum - see Kaschta and Schwarzl's 1994 papers on this matter.

If you are using simulations, you need to distinguish between integral and differential models. The former more or less calculate the spectrum and then the rheology from this, the latter determine the step-wise relaxation and thus G(t). So you only need to calculate the spectrum for differential models.

Hello Nityanshu,

Here is the experimental method to measure viscoelastic properties from a strain step:

Journal of Rheology 60, 649 (2016)

However, I am afraid that you won't be able to extract a relaxation time spectrum from these data.

Kind regards

Guy

See this discussion from 4 years ago.

https://www.researchgate.net/post/Is_there_any_simple_way_to_calculate_relaxation_spectrum_H_and_appearent_elastic_modulus_Ge_from_the_available_frequency_sweep_data

What the significance of Master-curve (TTS) from

1. Three point Bending

2. Dual cantilever

3. Single cantilever

@Nagamadhu M:

theoretically, it doesn't matter, with which geometry you measure the data. Practically, clamping will always lead to artefacts, which is why, I would prefer 3-p bending, if possible (if the sample is not too soft)

Dear sir

To determine of 3D polymer systems relaxation time may be to use tensometrical method

Best regards

Hi, there is a MATLAB simulation with codes available for relaxation spectrum (both continuous and discrete). You can google ReSpect MATLAB files, this should lead you to mathworks website and you can use the functions created by the author.

Thanks