K.S.R.K. Murthy

Extent of Three Parameter Zone and Optimum Strain Gage Location for Eccentric Cracked Configurations

The accuracy of measurement of opening mode stress intensity factor using strain gage techniques mainly depends on location of the strain gages. The present work proposes a finite element based simple procedure for accurate determination of three parameter zone and optimum strain gage location for various eccentric cracked configurations. In this paper, the effect of specimen size and crack length to width of the eccentric cracked plate on optimum location of strain gage is also studied. The results of the present investigation show that specimen size and ratio of crack length to width of the plate strongly influence the optimum location of strain gage.

Free Vibration Control of MRE Embedded Viscoelastic Cored Sandwich Beam With Time Varying Magnetic Field

The present work deals with the free vibration control of a simply supported and cantilevered sandwich beam with magnetorheological elastomer (MRE) embedded viscoelastic core and conductive skins subjected to time varying magnetic field. The skins of the sandwich beam are conductive such that magnetic loads are applied to the skins. Considering the core to be stiff in transverse direction, classical sandwich beam theory has been used along with extended Hamilton’s principle and Galarkin’s method to derive the governing equation of motion. The resulting equation reduces to that of a parametrically excited system. Method of multiple scales has been used to study the response and stability of the system. Critical parameters of amplitude and frequency of magnetic field have been determined to actively control the free vibration response of the system. Effects of percentage of iron particles and carbon black in attenuation of vibration of the sandwich beam have been studied. Here the experimentally obtained properties of recently developed magnetorheological elastomers based on natural rubber containing iron particles and carbon blacks have been considered in the numerical simulation.Copyright

Mode I SIF Determination of Orthotropic Laminates with Double-Ended Cracks Using a Single-Strain Gage

The experimental determination of mode I SIF (\(K_{I}\)) in orthotropic composites is significant, and strain gage-based approaches for SIF determination are quite economic and easy to use. Strain gage techniques that have been developed for measurement of \(K_{I}\) of orthotropic laminates are based on the solutions of single-ended crack theories. The present investigation aims at demonstrating the application of a single-strain gage technique (based on single-ended crack theory) recently proposed by the authors to double-ended cracked configurations for accurate measurement of KI. Finite element-based numerical analyses have been conducted on carbon-epoxy orthotropic laminates having center-cracked configurations. The existence and determination of optimal gage locations for accurate measurement of \(K_{I}\) have also been shown through numerical studies. Numerical results show that accurate values of \(K_{I}\) for double-ended cracked orthotropic laminates can be obtained with the help of a single-strain gage, when placed within the optimal zone.

Determination of Mode I Stress Intensity Factor for Orthotropic Laminates Using a Single Strain Gage

The present work discusses a robust method developed for determination of mode I stress intensity factor (KI) of orthotropic laminates using a single strain gage and based on a three parameter strain series representation ahead of the crack tip. Appropriate radial location of the strain gage ahead of the crack tip is important in the sense that strain gages placed either very near or very far from the crack tip might lead to inaccuracies in the estimated SIFs due to 3D effects near the crack tip or inaccurate strain field representation at farther distances. The theoretical formulation has been presented for determination of angular location, orientation and the upper bound on the radial location (rmax) for pasting the strain gage which could be subsequently used for accurate determination of KI. Numerical simulations have been presented considering edge cracked [902/0]10S carbon-epoxy orthotropic laminates to illustrate the determination of rmax and KI of such laminates. A R T I C L E I N F O Article history: Received 21 August 2016 Accepted 24 September 2016