Generation of higher harmonics in longitudinal vibration of beams with breathing cracks

This paper was accepted for publication in the journal Journal of Sound and Vibration and the definitive published version is available at http://dx.doi.org/10.1016/j.jsv.2016.06.025.Classical nonlinear vibration methods used for structural damage detection are often based on higher- and sub-harmonic generation. However, nonlinearities arising from sources other than damage – e.g. boundary conditions or a measurement chain – are a primary concern in these methods. This paper focuses on localisation of damage-related nonlinearities based on higher harmonic generation. Numerical and experimental investigations in longitudinal vibration of beams with breathing cracks are presented. Numerical modelling is performed using a two-dimensional finite element approach. Different crack depths, locations and boundary conditions are investigated. The results demonstrate that nonlinearities in cracked beams are particularly strong in the vicinity of damage, allowing not only for damage localisation but also for separation of crack induced nonlinearity from other sources of nonlinearities

Exact vacuum solutions of six dimensional Bianchi Type-I space-time in f (R) theory of gravity

In this paper, we have extended the five dimensional work refer it to [2] regarding the accelerating expansion of the universe to higher six dimension and obtained exact vacuum solutions of six dimensional Bianchi type-I space time in f (R) theory of gravity using metric approach. In particular, two different models of the universe have been investigated using the law of variation of Hubble parameter. We observed that, the first model is singular and second one is non singular. The physical properties of these models have been discussed and evaluated function of Ricci scalar, f (R) for both the models. It is interesting to note that, our five dimensional work explained in [2] and the work of M. Sharif and M. Farasat Shamir ( (2009) in 4 V regarding the universe expansion can be reproduced by reducing the dimensions

Role of grain/Phase boundary nature on the formation of hydrides in Zr-2.5% Nb alloy

Hydride formation in a fully recrystallized Zr-2.5%Nb alloy having equiaxed grains of α and β was studied. Primarily the electron back scatter diffraction (EBSD) technique was used for the characterization of the hydrides in conjunction with optical and transmission electron microscopy. Hydrides were found to have preferentially formed along the α/β interfaces. Microtexture measurements showed that the orientation relationship (OR) between α and δ -hydride phase was (0 0 0 1)<SUB>α</SUB> || (1 1 1)<SUB>δ</SUB> and [21<SUP>‾</SUP>10]<SUB>α</SUB> || [1 1 0]<SUB>δ</SUB>. It was shown that the hydrides have higher preference to form along such α/β interfaces which have one of the low index planes of the β phase constituting the interface

Automated reconstruction of pre-transformation microstructures in zirconium

An automated reconstruction of the pre-transformation microstructure from the microtexture data of the post-transformation product phase is proposed. The method involves identifying triplets of neighboring product grains with a common variant and linking such neighboring triplets via a generalized misorientation criterion. The approach is non-iterative and extremely efficient computationally. The method was tested successfully for different post-transformation microstructures in zirconium

Annealing of cold worked two-phase Zr-2.5 Nb - associated microstructural developments

Pilgered two-phase Zr-2.5 Nb was subjected to recovery (400 °C) and recrystallization (700 °C) annealing - broad objective was to bring out associated microstructural developments. Effects of recovery and recrystallization were indexed in terms of changes in hardness, lattice strain, stored energy of cold work and residual stress. Though recovery did not cause significant changes in grain/phase structure; visible coarsening of 2nd phase was associated with recrystallization. Such coarsening continued even after the completion of primary recrystallization, with concurrent and noticeable changes in microstructure and in crystallographic texture