Most of the sources that I had read about either talks about anelasticity or viscoelasticity, they don't compare both. From what I have read so far ,both anelastic and viscoelastic materials are the same. And they both show significant amount of time dependent strain component. Is there any difference between these two?
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$\begingroup$ anelastic? Did you mean in-elastic? $\endgroup$– Solar MikeAug 11, 2021 at 12:47
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$\begingroup$ @Solar Mike Nope. I think there is a term called anelasticity. $\endgroup$– Abhishek P GAug 11, 2021 at 13:18
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$\begingroup$ So this may help you: sciencedirect.com/topics/physics-and-astronomy/anelasticity $\endgroup$– Solar MikeAug 11, 2021 at 13:25
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$\begingroup$ @Solar Mike I did try to read it.But i was able to understand only the introduction. Rest of it is too complex or not at my level of knowledge to understand. As per the introduction what i understood was anelasticity is a special case of viscoelasticity. And anelasticity shows a time-dependent non elastic behaviour. $\endgroup$– Abhishek P GAug 11, 2021 at 14:22
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2 Answers
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Anelastic is a material that exhibits a delay in the deformation with respect to the loading.
figure 1: Anelastic material bevahiour (left: wrt to time, right: stress vs. strain) (source Princeton)
Visco-elastic are materials that the load to obtain the deformation also depends on the strain rate. I.e. How fast the deformation is applied. It might depend on other things. There are different models for the viscoelastic material:
figure 1: common Viscoleastic models (source Dickerson)
So a material can be anelastic and viscoelastic at the same time. They describe different properties which happen to be both related to time. Usually aviscoelastic material exhibits hysteresis which is trademark for anelastic.
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$\begingroup$ By this it would mean that visco elasticity is a special case of anelasticity where the stress-strain curve would depend on strain rate. Where as in anelasticity strain rate doesn't affect stress-strain curve. Does anelastic material have hysterisis loss. I have seen most reference that viscoelastic materials have hysterisis loss. $\endgroup$ Aug 11, 2021 at 14:33
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$\begingroup$ To be honest, -i've been trying to but - I can't think of a model that a material that can be represented by one of the common viscoelastic models will not have an anelastic behavior (at least under certain conditions). Also, I think anelastic behaviour is that norm in real life (at least in any form of cyclic loading). Maybe that is the reason that you have found in the literature that they appear being the same thing. $\endgroup$– NMech ♦Aug 11, 2021 at 18:20
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Anelastic materials have an element of time delay between stress and strain, and a time-dependent relaxation of strain. Wikipeidia link
But the viscoelastic materials have both properties of elastic and viscous materials when undergoing deformation.
Viscous materials resist shear flow. And have defusion of atoms under stress as compared to bond stretching along crystallographic planes.
Stress–strain curves for a purely elastic material (a) and a viscoelastic material (b). The red area is a hysteresis loop and shows the amount of energy lost (as heat) in a loading and unloading cycle. It is equal to , where is stress and is strain.1
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$\begingroup$ How is it different from viscoelasticity? $\endgroup$ Aug 11, 2021 at 15:08