Raju Sethuraman

A continuum damage mechanics model for ductile fracture

Abstract Continuum damage mechanics theory together with large deformation elastic–plastic finite element analysis has been used to predict crack growth initiation in ductile materials. The damage growth law is based on experimental observations reported in the literature. A local crack growth initiation criterion is proposed. The criterion makes use of the critical damage as the continuum parameter and the average austenite grain size as the characteristic length. To test the validity of this criterion, experiments have been conducted on standard specimens and have also been simulated numerically. The proposed criterion has been used to predict the values of the critical load at crack growth initiation and the fracture toughness. The numerically predicted values compare favourably with the experimental values.

Steady-state analysis of a three-layered electro-magneto-elastic strip in a thermal environment

In this paper, a three-layered electro-magneto-elastic strip is investigated under a plane stress condition using finite element procedures. Two types of thermal loading, uniform temperature rise and non-uniform temperature distribution, are used. A two-dimensional rectangular element with four nodal degrees of freedom viz. thermal displacements in the x1 and x3 directions, and electric and magnetic potentials, is used to discretize the finite element model. The uncoupled and coupled analysis is carried out for two types of stacking sequence (B/F/B and F/B/F) under fixed–fixed and fixed–simply supported boundary conditions. Steady-state analysis is carried out to study the influence of piezo and magnetic constants on displacement, electric and magnetic potential across the thickness direction. It is found that the discontinuities of normal stress σ1 occur on interfaces of two dissimilar materials across the thickness direction.

Stress intensity factors for circular hole and inclusion using finite element alternating method

Abstract A centre cracked plate subjected to remote tensile and shear loading is considered for the analysis. Effect of circular hole and influence of shrunk fit inclusion on stress intensity factors are studied. Multiply connected domain boundary value problem is solved using finite element alternating method (FEAM). Parametric studies involving drilled hole/inclusion sizes and locations are investigated. Energy release rates evaluated using the stress field obtained by FEAM are in good agreement with other methods. The optimum location in reducing the stress intensity factor with hole/inclusion is obtained and located at a distance 20% of semi-crack length from crack tip on the side opposite the ligament for Mode-I loading and it is also observed that the location is almost invariant of hole sizes. For Mode-II loading, the optimum location for the hole is located at a distance about 23% of semi-crack length from the middle of the crack along the transverse direction.

Vibro-Acoustic Analysis of Functionally Graded Elliptic Disc under Thermal Environment

Parametric studies are carried out on the prediction of vibro-acoustic response from an elliptic disc made up of Functionally Graded Material with several cases of FGM index “n,” varying minor axis “a” and for different ceramic combinations with steel. Displacement, velocity, acceleration, radiated sound pressure, radiated sound power level and radiation efficiency of the elliptic disc are examined over a range of varying frequencies. Vibration response due to harmonic point load under thermal environment was computed by finite element method using a macro developed in Ansys Parametric Design Language by the authors, using available physics in ANSYS. Acoustic response of the FGM elliptic disc was computed by coupling the vibration data from the finite element method to the boundary element method using LMS SYSNOISE.

Buckling and Vibration Analysis of Layered and Multiphase Magneto-Electro-Elastic Beam Under Thermal Environment

The paper deals with the investigation of linear buckling and free vibration behavior of layered and multiphase magneto‐electro‐elastic (MEE) beam under thermal environment. The constitutive equations of magneto‐electro‐elastic materials are used to derive finite element equations involving the coupling between mechanical, electrical and magnetic fields. The finite element model has been verified with the commercial finite element package ANSYS. The influence of magneto electric coupling on critical buckling temperature is investigated between layered and multiphase magneto‐electro‐elastic beam. Furthermore, the influence of temperature rise on natural frequencies of magneto‐electro‐elastic beam with layered and different volume fraction is presented.

Computational simulation of fatigue crack growth and demonstration of leak before break criterion

Abstract A thick plate with a semi-elliptical surface crack subjected to remote tension and tension fatigue loading is considered for the analysis. In the present study the material is assumed to have variable fracture toughness in the surface and thickness directions. Material with isotropic fracture toughness is also considered. The developed three dimensional finite element code which has the capability to handle singularity and evaluate fracture parameter based on force method is used to characterise the fatigue crack growth. Parametric study involving various initial crack sizes is carried out and Foreman’s equation is used to predict the crack growth. Various regions viz. break, leak before break are obtained.

PSEUDO ELASTIC ANALYSIS OF MATERIAL NON-LINEAR PROBLEMS USING ELEMENT FREE GALERKIN METHOD

Abstract Element Free Galerkin Method (EFGM) based on pseudo‐elastic analysis is presented for the determination of inelastic solutions. In the proposed method a linear elastic analysis, using moving least square approximating function, is carried out for the determination of stress field of material non‐linear problems using material parameters as field variables. Henckys total deformation theory is used to define effective elastic material parameters, which are treated as spatial field variables and considered to be functions of equilibrium stress state and material properties. These effective material parameters are obtained in an iterative manner based on strain controlled projection method and total energy balance Neubers rule, using experimental uniaxial tension test curve. The effectiveness of the method is illustrated using a problem of cylindrical vessel subjected to internal pressure and shear loads. Three different material models are considered for the problem: elastic‐perfectly plastic, linear strain hardening type and nonlinear behavior obeying Ramberg‐Osgood model. Obtained results for all the cases are compared with standard nonlinear finite element results and are found to be in good agreement.

Buckling and vibration analysis of layered and multiphase magneto‐electro‐elastic cylinders subjected to uniform thermal loading

Purpose – The purpose of the paper is to investigate the linear thermal buckling and vibration analysis of layered and multiphase magneto‐electro‐elastic (MEE) cylinders made of piezoelectric/piezomagnetic materials using finite element method.Design/methodology/approach – The constitutive equations of MEE materials are used to derive the finite element equations involving the coupling between mechanical, electrical, magnetic and thermal fields. The present study is limited to clamped‐clamped boundary conditions. The linear thermal buckling is carried out for an axisymmetric cylinder operating in a steady state axisymmetric uniform temperature rise. The influence of stacking sequences and volume fraction of multiphase MEE materials on critical buckling temperature and vibration behaviour is investigated. The influence of coupling effects on critical buckling temperature and vibration behaviour is also studied.Findings – The critical buckling temperature is higher for MEE axisymmetric cylinder as compared ...

Thermally induced vibrations of piezo‐thermo‐viscoelastic composite beam with relaxation times and system response

Purpose – The purpose of this paper is to present numerical studies on thermally induced vibrations of piezo‐thermo‐viscoelastic composite beam subjected to a transient thermal load using coupled finite element method.Design/methodology/approach – The thermal relaxation and viscoelastic relaxations are taken into consideration to obtain the system response. The concept of “memory load” along with the thermal relaxation is accounted for viscoelastic core material. The influence of type of core material on the response of the system also analyzed.Findings – The findings show viscoelastic behavior with relaxation times in composite sandwich structures.Originality/value – The paper shows accounting relaxation times as a memory load in composite sandwich structures.

VIBRO-ACOUSTIC ANALYSIS OF COMPOSITE CIRCULAR DISC WITH VARIOUS ORTHOTROPIC PROPERTIES

Composite circular discs with polar orthotropic and rectangular orthotropic fibers of different composite materials are modeled and their vibration response due to harmonic point load was computed by finite element method (FEM) using ANSYS. Acoustic response of composite circular disc was computed by coupling the vibration data from FEM to the boundary element method using LMS SYSNOISE.