Modeling Nonlinear Viscoelastic Nanoindentation of PVAc at Different Unloading Rates

Modeling of viscoelastic shear: A nonlinear stick-slip formulation

We present a class of nonlinear dynamic viscoelastic models for materials subjected to shear stress. The model equations are based on a continuum variation of a reptation model in which chemically cross-linked (CC) systems of molecules act as constraint boxes per unit volume for physically constrained (PC) systems of molecules. Results from validating the model with dynamic shear experiments ar...

Characterization of Viscoelastic Properties of Polymeric Materials through Nanoindentation

Nanoindentation is used to determine the dynamic viscoelastic properties of six polymer materials. It is shown that varying the harmonic frequency of the nanoindentation does not have any significant effect on the measured storage and loss moduli of the polymers. Agreement is found between these results and data from DMA testing of the same materials. Varying the harmonic amplitude of the nanoi...

Multilayer Quasi-Linear Viscoelastic Characterization of Porcine Aorta Using Nanoindentation

In a wide range of applications from traumatic injury to stent grafts, the arterial wall has been considered as a homogeneous single-layer vessel, ignoring the fact that arteries are composed of distinct anatomical layers with different mechanical characteristics. The multilayer nature of arteries has an important influence in the development of mathematical models to predict large deformations...

AN EXPLORATORY INVESTIGATION OF VISCOELASTIC NANOINDENTATION ON POLYVINYL ACETATE By

the role of application of dynamic assessment approach in improvement of iranian efl writing performance at different language proficiency levels

the present study sought to investigate the role of dynamic assessment (da) in improvement of iranian efl writing performance at different language proficiency levels. to this end, after conducting the quick placement test, 60 iranian efl learners were assigned to two groups with different language proficiency levels. in both groups each participant wrote two compositions, one before and one af...