V. Parameswaran - Academia.edu (original) (raw)

Papers by V. Parameswaran

$Research paper thumbnail of Crack-tip fields for dynamic fracture in functionally gradient materials$

Materials & Design, 2010

The use of adhesive joints has gained good acceptance in the automotive and aerospace industries ... more The use of adhesive joints has gained good acceptance in the automotive and aerospace industries in recent years, particularly for joining glass fiber reinforced plastics (GFRP) to metals. Such joints will be subjected to short duration dynamic loads in service. The present study focuses on the evaluation of the shear strength of adhesive joints prepared using four different commercial adhesives at loading rates in the range of 0.6-1.2 MPa/ls. The adhesives used were Araldite 2014, Araldite 2011, Epibond 1590 and A/B Loctite 324. Joints were prepared with two different adherent combinations; aluminum-aluminum and aluminum-GFRP. The results of the study indicated that, depending on the adhesive and adherent combination, the dynamic strength was 2-4 times the static strength. Among the four adhesives, Epibond 1590 exhibited the highest rate sensitivity whereas Loctite 324 exhibited the least. Further it was also observed that the dynamic strength was not sensitive to the adherent combination whenever the failure was predominantly within the adhesive layer.

Strain, 2008

Abstract: This paper focuses on the application of the digital image correlation (DIC) technique... more Abstract: This paper focuses on the application of the digital image correlation (DIC) technique to determine the stress intensity factor (SIF) for cracks in orthotropic composites. DIC is a full-field technique for measuring the surface displacements of a deforming object and can be applied to any type of material. To determine the SIF from full-field displacement data, the asymptotic expansion of the crack-tip displacement field is required. In this paper the expansion of the crack tip displacement field is derived from an existing solution for strain fields. Unidirectional fibre composite panels with an edge crack aligned along the fibre were tested under remote tensile loading and the displacements were recorded using DIC. The SIF was calculated from the experimental data by fitting the theoretical displacement field using the least squares method. The SIF thus determined was in good agreement with theoretical results and therefore demonstrates the applicability of the derived displacement field and DIC technique for studying fracture in composites.

$Research paper thumbnail of Photoelastic investigation of interfacial fracture between orthotropic and isotropic materials$

Optics and Lasers in Engineering, 2003

... 2.2. Determination of stress intensity factor for stationary crack by boundary collocation me... more ... 2.2. Determination of stress intensity factor for stationary crack by boundary collocation method. The bi-material model used for numerical study is shown in Fig. 1(a) with traction T y applied on the upper and lower boundaries. ...

$Research paper thumbnail of Crack-tip stress fields for dynamic fracture in functionally gradient materials$

Mechanics of Materials, 1999

... V. Parameswaran and A. Shukla Corresponding Author Contact Information , E-mail The Correspon... more ... V. Parameswaran and A. Shukla Corresponding Author Contact Information , E-mail The Corresponding Author. ... Parameswaran and Shukla (1998) investigated dynamic fracture in FGMs having discrete property variations using dynamic photoelasticity. ...

Journal of Testing and Evaluation, 2000

... (1) Dynamic Photomechanics Laboratory, Department of Mechanical Engineering and Applied Mecha... more ... (1) Dynamic Photomechanics Laboratory, Department of Mechanical Engineering and Applied Mechanics, University of Rhode Island, RI ... Junta recubierta ; Efecto dimensional ; Carga dinámica ;Onda tensión ; Onda elástica ; Propagación onda ; Resistencia cizallamiento ...

Journal of Reinforced Plastics and Composites, 2010

ABSTRACT In this study, the thermoplastic poly-ether-ether-ketone (PEEK) was reinforced with alum... more ABSTRACT In this study, the thermoplastic poly-ether-ether-ketone (PEEK) was reinforced with alumina nanoparticles and the effect of adding nanoparticles on the properties of PEEK was investigated. A novel processing route consisting of first dispersing the nanoparticles and fine PEEK powder in ethanol medium through ultrasonication and then compounding the dried mixture in a single screw extruder to produce tapes was adapted to make the composites. Composites having particle weight fractions of 1%, 2%, 3%, and 5% were prepared successfully. Transmission electron micrographs of the prepared composites indicated excellent dispersion of nanoparticles even for the 5% composite. Subsequently, thermal, tensile and dynamic properties of the composite were evaluated. The results of the thermal characterization indicated that addition of 5% weight fraction of the nanoparticles improved the thermal decomposition temperature by 27°C. The storage modulus increased with addition of nanoparticles whereas the loss factor decreased. The tensile strength and failure strain of the 5% composite was respectively, 9% and 28% higher than that of PEEK.

Journal of Materials in Civil Engineering, 2004

Asphalt is a heterogeneous material composed of aggregates, binder cement and air voids, and may ... more Asphalt is a heterogeneous material composed of aggregates, binder cement and air voids, and may be thought of as a cemented particulate system. The load carrying behaviors are strongly related to the local load transfer between aggregate particles, and this is taken as the microstructural response. Numerical simulation was developed using two different finite element models, which were constructed to simulate the micromechanical response of the aggregate/binder system. The first model incorporated a network of frame elements with a special stiffness matrix developed to predict the load transfer between cemented particles. The second model used the commercial ABAQUS FEA code incorporating special user-defined continuum elements for the binder and rigid elements for the aggregate. Simulations of standard laboratory indirect tension tests have been conducted, and the results have compared favorably with experimental data. Further experimental verification has included tests on specially prepared cemented particulate systems, which have allowed detailed measurement of aggregate displacements and rotations using video imaging and computer analysis. Modeling simulations have been developed for a variety of material microstructures including aggregate gradation and distribution, binder volume and porosity.

Journal of Applied Mechanics, 2002

Stress field for stationary cracks, aligned along the gradient, in functionally graded materials ... more Stress field for stationary cracks, aligned along the gradient, in functionally graded materials is obtained through an asymptotic analysis coupled with Westergaard’s stress function approach. The first six terms of the stress field are obtained for both opening mode and shear mode loading. It is observed that the structure of the terms other than r−1/2 and r0 are influenced by the nonhomogeneity. Using this stress field, contours of constant maximum shear stress are generated and the effect of nonhomogeneity on these contours is discussed.

International Journal of Plasticity, 2011

A novel 'stack' model of a rate-independent polycrystal, which extends the 'ALAMEL' model of Van ... more A novel 'stack' model of a rate-independent polycrystal, which extends the 'ALAMEL' model of Van Houtte et al. (2005) is proposed. In the 'stack' model, stacks of N neighboring 'ALA-MEL' domains collectively accommodate the imposed macroscopic deformation while deforming such that velocity and traction continuity with their neighbors is maintained. The flow law and consistency conditions are derived and an efficient solution methodology based on the linear programming technique is given. The present model is applied to study plastic deformation of an idealized two-dimensional polycrystal under macroscopically imposed plane-strain tension and simple shear constraints. Qualitative and quantitative variations in the predicted macroscopic and microscopic response with N are presented. The constraint on individual 'ALAMEL' domains diminishes with stack size N but saturates for large N. Computational effort associated with the present model is analyzed and found to be well within one order of magnitude greater than that required to solve the classical Taylor model. Furthermore, implementation of the consistency conditions is found to reduce computation time by at least 50%.

Journal of Elasticity, 2002

A generalized elastic solution for an arbitrarily propagating crack in Functionally Gradient Mate... more A generalized elastic solution for an arbitrarily propagating crack in Functionally Gradient Materials (FGMs) is obtained through an asymptotic analysis. The shear modulus and mass density of the FGM are assumed to vary exponentially along the gradation direction. The mode mixity due to the inclination of property gradient is accommodated in the analysis through superposition of the opening and shear

IEEE Transactions on Dielectrics and Electrical Insulation, 2000

In this work, the complex permittivity of epoxy resin is measured. Earlier, we have shown that th... more In this work, the complex permittivity of epoxy resin is measured. Earlier, we have shown that the inclusion of nanometric alumina particles (Al2O3), both as-received and pre-processed, improves the ability of a polymeric dielectric (epoxy) to resist degradation when exposed to surface discharges. In this work, we use dielectric spectroscopy to characterize neat epoxy (unfilled) and epoxy nanocomposites prepared with

Experimental Mechanics, 1999

An experimental investigation of the ballistic performance of composite armor with geometric modi... more An experimental investigation of the ballistic performance of composite armor with geometric modifications was carried out. The armor was simulated using polymeric materials. Four different geometric modifications were incorporated into the front plate of the armor, and two different adhesives were considered in this study. High-speed photography was employed to observe the real-time evolution of impact damage and to obtain

Journal of materials science, 2000

A technique for preparing model Functionally Gradient Materials (FGM) using polyester resin and c... more A technique for preparing model Functionally Gradient Materials (FGM) using polyester resin and cenospheres is developed. The cenosphere volume fraction in the polyester matrix is continuously varied through a buoyancy assisted casting process. FGMs having ...

Dynamic and quasi-static experiments were performed using a novel lap joint specimen to evaluate ... more Dynamic and quasi-static experiments were performed using a novel lap joint specimen to evaluate the shear strength of adhesive bonded lap joints at different loading rates, length to width ratios and lap areas. Dynamic shear strength was determined by subjecting the lap joints to stress wave loading in a Split Hopkinson Pressure Bar (SHPB) apparatus. All joints were bonded by

Proceedings of the SEM …, 2007

Transparent graded materials were used to investigate the steady state and transient crack propag... more Transparent graded materials were used to investigate the steady state and transient crack propagation in a functionally graded material. A transparent graded material was fabricated using two different materials systems of polymer resin, which were cast using a special mold; to give continuously graded properties along the crack propagation direction. High-speed digital photography combined with photoelasticity technique was used to record the full-field stress data around the propagating crack. By analyzing the photoelastic fringe patterns the dynamic stress intensity factor and propagation velocity of the crack tip were obtained. Experiments were also done with FGMs where the properties were graded through thickness direction. Similar techniques were used for fabrication and analysis of the dynamic fracture behavior of thickness graded FGMs.

$Research paper thumbnail of Estimation of fracture parameters and stress field for edge cracks in finite elastically graded plates using boundary collocation$

Acta Mechanica, 2006

The fracture parameters, stress intensity factor and T-stress are obtained for edge cracks aligne... more The fracture parameters, stress intensity factor and T-stress are obtained for edge cracks aligned along the gradient in finite size elastically graded plates using the technique of boundary collocation. A scheme for extending the recently derived crack tip stress field for elastically graded materials is proposed. Using this extended stress field, the fracture parameters are evaluated for edge cracks subjected to far field tension and three point bending. The results for far field tension agreed well with published theoretical results over a good range of elastic gradients. The maximum shear stress calculated over the entire domain of the cracked plate using boundary collocation agrees very well with that obtained from finite element analysis. The efficacy of the extended stress field in capturing the effects of the elastic gradient on the stresses and fracture parameters is thus established in this study.

Acta Mechanica, 2003

Summary. Quasi-static stress fields for a crack inclined to the direction of property gradation... more Summary. Quasi-static stress fields for a crack inclined to the direction of property gradation in functionally graded materials (FGMs) are obtained through an asymptotic analysis coupled with Westergaard&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#x27;s stress function approach. The elastic modulus of the FGM is assumed to vary exponentially along the gradation direction. The mode mixity due to the inclination of the property gradient is accommodated in the

Abstract In this work we have proposed a combined experimental-numerical technique to elicit impo... more Abstract In this work we have proposed a combined experimental-numerical technique to elicit important quantitative information about the dielectric properties of the interphase region surrounding a nanoparticle embedded in a polymer matrix. The method involves ...

Compression test of Al 7075 T651 was carried out at high strain rates (1138 – 2534 s -1 ) using ... more Compression test of Al 7075 T651 was carried out at high strain rates (1138 – 2534 s
-1
) using
Split Hopkinson Pressure Bar and at slow strain rate (10
-4
s
-1
) in 100KN Universal Testing
machine to understand the improvement in mechanical properties and associated changes in
microstructures. Cylindrical specimens of 6 mm height and 6 mm diameter were compressed
dynamically. The influence of strain rates on mechanical properties, microstructure evolution
and corrosion behavior after immersion test in 3.5% NaCl solution was also investigated.
Strain rate, withdrawal stress and yield stress were observed to increase with impact velocity
in high strain rate tests, while in slow strain rate tests, n value was observed to increase with
increasing total strain. Microstructural observations revealed that after high strain rate test,
grains of Al matrix were elongated. It was observed that corrosion resistance decreased with
increase in impact velocity.