Dynamic viscoelastic properties of bamboo were determined in torsion and bending. Damping, measured by tan δ, in dry bamboo was relatively small, about 0.01 in bending and 0.02 to 0.03 in torsion, with little dependence on frequency in the audio range. In wet bamboo, damping was somewhat greater: 0.012 to 0.015 in bending and 0.03 to 0.04 in torsion. The anisotropy in damping implies a purely c...

In this paper a hybrid semi-analytical Finite Element formulation is proposed to efficiently calculate the time dependent response due to stress waves propagating in a slender solid with uniform cross-section when excited by impulsive forces. The formulation takes advantage of the direct and inverse Fourier transform to formulate and solve the governing wave equation. The framework is applied t...

This paper presents computational simulations of single-mode and bimodal atomic force microscopy (AFM) with particular focus on the viscoelastic interactions occurring during tip-sample impact. The surface is modeled by using a standard linear solid model, which is the simplest system that can reproduce creep compliance and stress relaxation, which are fundamental behaviors exhibited by viscoel...

A phenomenological approach is used to represent the nonlinear viscoelastic behavior of solid propellants. A three dimensional nite strain viscoelastic model, modi ed by a strain softening function that accounts for damage e ects, is considered in the research. Some of the signi cant aspects of high-elongation propellants are incorporated into the constitutive model. The resulting stress-strain...

In this research, two systems are studied. In the first system, the ratio of poly (methyl methacrylate) (PMMA) and poly (vinyl chloride) (PVC) is varied, whereas in the second system, the composition of PMMA-PVC polymer blends is varied with dopant salt, lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) with a fixed ratio of 70 wt% of PMMA to 30 wt% of PVC. Oscillation tests such as amplitu...

In vivo aspiration experiments on human livers are analyzed and material parameters for a non-linear-viscoelastic constitutive model are determined. A novel procedure is applied for the inverse analysis that accounts for the initial tissue deformation in the experiment and for the non-homogeneity of liver tissue. A numerical model is used consisting of a surface layer (capsule) and an underlyin...

We numerically model the human brain dynamics in realistic 2D cross-sections during traumatic scenarios corresponding to the Head Injury Criterion’s critical value HIC36=1000. Our simulations are based on the Kelvin-Voigt Partial Differential Equations that treat the brain tissue as a viscoelastic solid and on our nonlinear generalization of these linear PDEs that treats the tissue as an incomp...

Starches were isolated from grains of waxy, heterowaxy, and normal sorghum. To study the relationship between starch structure and functionality and guide applications of these starches, amylose content, amylopectin chain-length distributions, gelatinization and retrogradation, pasting properties, dynamic rheological properties, and in vitro enzyme digestion of raw starches were analyzed. Heter...

The experimental timescale of memory effects related to restoring equilibrium viscoelastic properties in solution-cast linear and long-chain branched polyethylenes has been investigated. It was found that the crystallization history of low-density polyethylene and ultra-high-molecular-weight polyethylene, with respect to solid-state and melt properties, is lost after heating into the melt after...