Linearization in nonlinear viscoelasticity and its use in the determination of relaxation moduli

A short review is given of the Green-Rivlin theory of nonlinear materials with memory. Small viscoelastic deformation following instantaneous finite elastic response is analysed by linearization of the added viscoelastic deformation. Incompressible, initially isotropic, materials are considered. Such an approach can simplify the analysis of the technologically important problem of stress analysis following sudden loading, which does not fall within the scope of the more common perturbation about a steady or equilibrium strain configuration. The method is applied to the problem of simple tension of a nonlinear viscoelastic rod. Measurement of the mechanical behaviour of real materials is considered. It is shown how material behaviour, in the form of the kernel functions (relaxation moduli) of the linearized constitutive equation, may be determined by a series of two-step simple relaxation tests. Use of the linearization in stress analysis problems is discussed. In addition to being able to determine the kernel functions of the linearized equation by a simple series of experiments, there is the additional practical advantage over the general nonlinear theory of speed of computation.     

The determination of oxidising and reducing cations in transition-metal oxides using vanadium sulphate solutions

Because vanadium sulphate solutions are very stable, they make useful analytical reagents. A solution of quinquevalent vanadium sulphate in dilute sulphuric acid can be used for the determination of Pe^II, Ti^III and V^III ions present in solid oxides. A similar solution of quadrivalent vanadium can be used for the determination of Co^III, MnIII and MnIV. The importance of the method in studies of mixed transition-metal oxides is briefly discussed.     

On the experimental determination of triplet-triplet extinction coefficients and oscillator strengths

Oscillator strengths for triplet-triplet transitions in fluid solution are reported. From these results and from a comparison with previous work, experimental support is provided for the constancy of triplet-triplet oscillator strengths under various solvent and temperature conditions.     

Novel identification approach for nonlinear systems with hysteresis

Nonlinear Dynamics - A new identification approach for a nonlinear system with hysteresis, namely a cascading Bouc–Wen hysteresis model with linear dynamics, is proposed in this study. The...