Features and limitations of recent elastoviscoplastic constitutive models under Large Amplitude Oscillatory Shear (LAOS)

Abstract

Elastoviscoplastic (EVP) models are becoming more widely adopted to investigate the deformation and flow of yield stress materials for various applications. In this work, we investigate EVP models, primarily the Saramito model but also the recently developed Kamani–Donley–Rogers (KDR) model, under Large Amplitude Oscillatory Shear (LAOS) tests using Fourier Transform (FT) rheology, dissipation ratio ($\varphi$) analysis and the Sequence of Physical Processes (SPP) framework. A detailed parametric study has been conducted for the Saramito model for a wide range of values of the relevant non-dimensional parameters – Bingham, Weissenberg and Deborah numbers. We also compare the Saramito and KDR models for a particular set of conditions and compare them with experimental data for Pluronic F127 hydrogel, a yield stress fluid commonly used in 3D printing. The parametric study of the Saramito model reveals a universal scaling for the onset of purely elastic behaviour, which shows dependence on both Bingham and Weissenberg numbers. Moreover, we demonstrate that although both EVP models can predict the ‘yielding’ process, the KDR model provides a better agreement with rheological data for Pluronic F127. The KDR also performs better in predicting associated EVP behaviour compared to the Saramito model, e.g. gradual change in the storage and loss moduli and the $\varphi$ values near the onset of yielding. However, neither model could fully capture higher harmonics, shapes of the Lissajous-Bowditch curves and the intra-cycle rheological transitions when compared to experimental data. In addition to the LAOS measurements, further tests under different flow conditions of the recently-developed KDR model against experimental data for yield stress fluids are required to assess its capabilities in capturing the full spectrum of EVP behaviours.