The key difference between viscoelastic and viscoplastic is that viscoelastic materials show both viscous and elastic properties when undergoing deformation, whereas viscoplastic materials show unrecoverable deformation.
Viscoelasticity and viscoplasticity are described regarding the properties of polymer materials. Both these terms describe the behaviour of a polymer material during the deformation of the polymer.
CONTENTS
1. Overview and Key Difference
2. What is Viscoelastic
3. What is Viscoplastic
4. Side by Side Comparison – Viscoelastic vs Viscoplastic in Tabular Form
5. Summary
What is Viscoelastic?
Viscoelastic materials are polymer substances that show both viscous and elastic properties during the deformation of the material. This property is named as viscoelasticity. Generally, viscous substances such as water resist shear flow and strain linearly with time when we apply stress. On the other hand, elastic substances, when stretched, return to their original state once the stress is removed. Therefore, we can observe that viscoelastic materials have both these properties. Moreover, these materials exhibit a time-dependent strain. Generally, elasticity is the result of the bond stretching along crystallographic planes in an ordered solid, while viscosity is the result of the diffusion of atoms or molecules inside an amorphous material.
When comparing elastic and viscoelastic substances, a viscoelastic substance has both viscous and elastic components, and the viscosity of these substances give them a strain rate that depends on time. Moreover, a pure elastic material does not dissipate energy when a load is applied and removed, but a viscoelastic substance dissipates energy at the same occasion.
Viscoelasticity can be defined as a molecular rearrangement. When we apply stress on these materials, part of the long polymer chain changes the positions. This rearrangement is named as a creep. Even after this rearrangement, the polymer remains solid in order to accompany the stress.
What is Viscoplastic?
Viscoplastic materials are polymer substances that show both viscous and plastic properties during the deformation of the material. This property is named as viscoplasticity. It is a rate-dependent inelastic behaviour of solids. The term “rate-dependence” refers to the deformation of the material that depends on the rate at which loads are applied. Viscoplasticity refers to inelastic behaviour, which means that the material undergoes unrecoverable deformations when a load level is reached.
Usually, we can model viscoplasticity in three-dimension using overstress models. These models have the stress allowed to be increased beyond the rate-dependent yield surface upon the application of a load, and then it is allowed to relax back to the yield surface over time. As an alternative approach, we can add a strain rate dependence to the yield stress and use the techniques of the rate-independent plasticity for the calculation of the response of a material.
Viscoplasticity theories are important in the calculation of permanent deformations, the prediction of the plastic collapse of structures, crash simulations, the investigation of stability, the dynamic problems and systems that are exposed to high strain rates.
What is the Difference Between Viscoelastic and Viscoplastic?
Viscoelasticity and viscoplasticity are described regarding the properties of polymer materials. The key difference between viscoelastic and viscoplastic is that viscoelastic materials show both viscous and elastic properties when undergoing deformation, whereas viscoplastic materials show unrecoverable deformation.
The below infographic summarizes the differences between viscoelastic and viscoplastic materials.
Summary – Viscoelastic vs Viscoplastic
Viscoelasticity and viscoplasticity are described regarding the properties of polymer materials. The key difference between viscoelastic and viscoplastic is that viscoelastic materials show both viscous and elastic properties when undergoing deformation, whereas viscoplastic materials show unrecoverable deformation.
Reference:
1. “Viscoplasticity.” Wikipedia, Wikimedia Foundation, 12 May 2020, Available here.
Image Courtesy:
1. “Non-Newtonian fluid” By Non-Newtonian_fluid.PNG: Original uploader was Duk at English Wikipedia / *derivative work: Nicoguaro (talk) – Non-Newtonian_fluid.PNG. Modifications: Vectorized. The original can be viewed here: Non-Newtonian fluid.PNG: Modifications made by Nicoguaro (CC BY-SA 3.0) via Commons Wikimedia
