K S R Krishna Murthy

• Indian Institute of Technology Guwahati

ABSTRACT The present paper aims at theoretical development of a strain gage-based methodology for accurate determination of notch stress intensity factor (NSIF) in sharp center V-notched tensile configuration (CENT). In line with Dally Sanford's single strain gage technique for determination of SIF in cracked configuration, theoretical formulations...

Notches are one of the most common features of the engineering world which are incorporated deliberately in certain engineering components such as screws, gears, nuts, bolts, etc. according to varied design needs. However, if not taken care of, the presence of notches may also be a matter of concern under certain conditions of load and other parame...

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....

Strain gage techniques have been successfully but sparsely used for the determination of stress intensity factors (SIFs) of orthotropic materials. For mode I cases, few works have been reported on the strain gage based determination of mode I SIF of orthotropic materials. However, for mixed mode (I/II) cases, neither a theoretical development of a...

Accurate determination of mixed mode stress intensity factors (SIFs) is essential in understanding and analysis of mixed mode fracture of engineering components. Only a few strain gage determination of mixed mode SIFs are reported in literatures and those also do not provide any prescription for radial locations of strain gages to ensure accuracy o...

This paper presents a robust technique for experimental determination of mode I stress intensity factor in orthotropic materials using only a single strain gage. Theoretical foundation and finite element based analysis leading to the selection of the angular orientation and position of the strain gage for accurate estimation of KI in orthotropic ma...

A theoretical frame work is developed for strain gage based determination of mixed mode stress intensity factors (SIFs) in slant edge cracked plate (SECP) made of orthotropic materials. Using three parameter strain series around the crack tip and appropriate stress functions, the present formulation shows that mixed mode SIFs in orthotropic materia...

Determination of accurate mixed mode stress intensity factors forms the basis for the under standing and analysis of mixed mode fracture. In this context, experimental methods for the measurement of stress intensity factors (SIFs) play a vital role. However, very few strain gage based techniques are available for measurement of mixed mode SIFs KI a...

Experimental determination of mode I stress intensity factor (SIF) KI in orthotropic composites is of significant importance. In this direction, single strain gage techniques that are developed for measurement of KI are based on the solutions of the single ended crack theories and those have also been tested only for single ended cracked orthotropi...

In this paper, a single strain gage technique has been used for determination of mode I stress intensity factor (SIF) for orthotropic laminates. Considering mode I crack in an orthotropic laminate as plane stress problem, angular position and orientation of a strain gage has been determined such that mode I SIF could be determined pasting a single...

In this paper, a single strain gage technique has been used for determination of stress intensity factor (SIF) for orthotropic laminates. Considering mode I crack in an orthotropic laminate as plane stress problem, angular position and orientation of a strain gage has been determined such that mode I SIF (KI ) could be determined pasting a single s...

In this work the dynamic stability of a rotating three layered symmetric sandwich beam with magnetorheological elastomer (MRE) core and conductive skins subjected to axial periodic loads has been investigated using finite element method (FEM). The derived governing equation of motion is in the form of a multi-degree of freedom Mathieu-Hill’s equati...

The present work proposes a new single strain gage technique for the accurate determination of mode I stress intensity factor (SIF) in orthotropic composite materials. This work also aims at showing the existence of valid or optimal gage locations for the accurate determination of SIFs in orthotropic composites. Accordingly, a finite element based...

In this study, the isotropic magnetorheological elastomer samples are fabricated with and without addition of carbon blacks into the silicon rubber matrix and carbonyl iron particles in the absence of magnetic field. Microscopic and morphological analyses, thermo-gravimetric analysis, MH measurements, thermomechanical analysis, dynamic mechanical a...

The dynamic stability of a partially treated magnetorheological elastomer (MRE) cored sandwich beam with conductive skins subjected to time varying axial load has been studied. The finite element method (FEM) and Guyan reduction method are used to derive the governing equation of motion which is similar to that of Mathieu's equation. The instabilit...

The present work focuses on the experimental verification of optimal strain gage locations and their importance in accurate determination of mode I stress intensity factors (SIFs) using Daily and Sanford's single strain gage technique (DS technique). The results of the present experimental study are also used to substantiate the efficacy of the met...

In this article, the free and forced vibration analyses of a three-layered magnetorheological elastomer embedded viscoelastic cored sandwich beam with conductive and non-conductive skins have been carried out using finite element method. The finite element method formulation is validated by conducting experiments for a viscoelastic cored sandwich c...

Strain gage based methods for experimental determination of stress intensity factors (SIFs) are equally powerful as compared to the other methods such as photoelasticity and caustics. However, a major problem with the strain gage methods is the lack of practical recommendations for appropriate radial locations for strain gages for accurate measurem...

Assessment of proper radial location for strain gages is extremely important in accurate experimental determination of mixed mode stress intensity factors (SIFs) and is an open problem. The present work proposes a methodology for accurate estimation of maximum permissible radial location (rmax) and also suggests a new strain gage method for experim...

The present work deals with the dynamic stability of a symmetric sandwich beam with magnetorheological elastomer (MRE) embedded viscoelastic core and conductive skins subjected to time varying axial force and magnetic field. The conductive skins induce magnetic loads and moments under the application of magnetic field during vibration. The MRE part...

In this work free vibration analysis of a sandwich beam with magneto rheological elastomer (MRE) core and composite skins has been investigated using finite element method (FEM). Both classical and higher order theories have been applied in the FE formulation. While in classical theory the strain in the transverse direction is neglected, in higher...

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 p...

The dynamic analysis of a three-layered symmetric sandwich beam with magnetorheological elastomer (MRE) embedded viscoelastic core and conductive skins subjected to a periodic axial load have been carried out under various boundary conditions. As the skins of the sandwich beam are conductive, magnetic loads are applied to the skins during vibration...

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...

A general methodology has been proposed for calculation of optimum radial strain gage locations for measurement of the stress intensity factors using strain gage technique. The upper bound (rmax) of strain gage locations for complex single ended and double ended cracked configurations has been determined using the proposed method. Further, dependen...

Strain gage methods are popular in experimental determination of stress intensity factors (SIFs). Radial location of gages with respect to the crack tip plays an important role in accuracy of strain measurements and thus accurate determination of SIFs. The present work proposes a finite element based simple, accurate and consistent method for deter...

A new, simple and efficient method for simultaneous estimation of the mixed-mode stress intensity factors (SIFs) and T-stresses using finite element computations is proposed in this paper. The current work is based on the formation of overdetermined system of equations using the displacement components near the crack tip. The proposed method can be...

The accuracy of measurement of opening mode stress intensity factors using the strain gage techniques largely depends on location of the gages. The radial position of the strain gages is a major issue in measurement of the stress intensity factors. This paper describes an approach to resolve this problem. The present work proposes a method for prac...

Among techniques for the determination of the mode I stress intensity factors (SIFs), strain gage procedures are the simplest and most straightforward. We report here on an experimental investigation of the determination of opening mode stress intensity factors using the single strain gage method. Our approach overcomes certain drawbacks and greatl...

An h-adaptive finite element procedure consisting of recently developed mesh generator (advancing front type and exclusively suitable for two-dimensional domains containing cracks), ZZ-error estimator and a refinement strategy based on strain energy concentration index have been used to refine the meshes of domains containing cracks adaptively to a...

A fully automatic advancing front type mesh generator to take care of crack problems has been presented. It is coupled with the Zienkiewicz and Zhu error estimator and the refinement methodology depends on the concept of strain energy concentration for completely automatic adaptive analysis of mixed-mode crack problems. For the first time energy ba...

Fully automatic advancing front type mesh generator to take care of crack and fracture problems has been presented. It is coupled with Zienkiewicz and Zhu error estimator, the refinement methodology depends on the concept of strain energy concentration for adaptive analysis of mixed-mode crack problems. No investigation is reported in this directio...