IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Finite element simulation of the densification behaviour of porous cylindrical steel specimens under dynamic loading was undertaken in depth. An explicit analysis along with a plasticity model for porous solids was used. Stress, strain, and density distributions were determined with respect to time. The effects of stress waves and the reflection of these waves at the specimen boundary were clarified, the stress exerted on the die wall during the process was evaluated, and the effects of die wall friction, specimen size, and material properties on the densification process are presented. The predicted results compared with experimental data from earlier reported works were found to be in good agreement.

Department of Engineering Design

World University root node

Simulation Studies on Compression of Porous Metals by Dynamic Loading

The technique of reinforcing soil for foundation improvement is well established. This paper addresses the aspect of settlement of reinforced sand foundations, where the major part of the existing work deals with the aspect of bearing capacity. A detailed analysis is made paying individual attention to soil, reinforcement, and the interface between the two. A three-dimensional, nonlinear finite-element analysis is presented that uses a three-dimensional, nonlinear soil-reinforcement interface friction element, along with other three-dimensional elements to model the system. The results of the analysis are compared with those from tests conducted in the laboratory and are found to be in good agreement. The studies lead to a better understanding of the behavior of the system at different stages of loading.

GENERAL

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Journal of Geotechnical Engineering

Settlement of reinforced sand in foundations

The title compound TeIVLI3 [L = diethyldithiocarbamate, (C2H5)2NCS-2], is the first example of a mixed halide-dithiocarbamate complex of TeIV with halide to a dithiocarbamate ratio of 3 : 1. Two different methods have been employed for the preparation of this compound. The first method involves the ligand exchange reaction between TeL2 and Tel4. The second method is the oxidative addition of iodine on TeIILI. The structure of the title compound has been determined and it is found to be polymeric with iodine being the bridging ligand. The polymer is made up of interlinking of edge-sharing pentagonal bipyramidal dimers, which are stacked along a axis of the triclinic unit cell. The three Te-I distances are Te-I(1) 2.982(1), Te-I(2) 2.901(1) and Te-I(3) 2.872(1) Å, and together with two Te-S and two intermolecular Te-I interactions complete the seven coordination with a distorted pentagonal bipyramidal geometry around each tellurium.

Department Of Chemistry

Polyhedron

A novel mixed ligand Te(IV) complex comprising three halides and a dithiocarbamate; synthesis and crystal structure of triiododiethyldithiocarbamatotellurium(IV), Te{(C2H5)2NCS2}I3

Bromo- and chloro-substituted tellurium(II) dithiocarbamate complexes were prepared by the reaction of iododiethyldithiocarbamatotellurium(II), dissolved in dichloromethane, with a suspension of their respective silver halide. The structure determination reveals the orthorhombic crystals of the complexes to be isomorphous, having halide-bridged polymeric structures. The polymeric chain adopts a helical configuration with the period of the helix being the length of the a-axis. Each tellurium has a TeS2X2 coordination. The Te - Br and Te - Cl distances observed in the complexes are 2.867(3) and 2.686(2) Å, respectively and this structure is similar to that of Te{(C2H5)2NCS2}1. Copyright © 1996 Elsevier Science Ltd.

Synthesis and structure of the isomorphous bromo- and chlorodiethyldithiocarbamatotellurium(II), Te{(C2H5)2NCS2}X (X = Br, Cl)

In the structure of bis(diethyldithiocarbamato-S,S′)-tellurium(II)-4,4′-bipyridyl (2/1), [Te(C5H10NS2)2].-1/2C10H 8N2, the bipyridyl molecule was found to bridge two bis(diethyldithiocarbamato)tellurium moieties centrosymmetrically, i.e. μ-(4,4′-bipyridyl-N:N′)-bis(diethyl-dithiocarbamato-S,S′) tellurium. The N atom of the bipyridyl is very weakly coordinated to tellurium and this is the first instance of Te-N coordination observed in a tellurium-dithiocarbamate complex. Each Te atom has an unusual planar-pentagonal arrangement of ligands around it.

Acta Crystallographica Section C: Crystal Structure Communications

The hemi-adduct of bis(diethyldithiocarbamato-S,S′)tellurium(II) with 4,4′-bipyridyl

In this paper, a finite element analysis of steady-state dynamic crack growth under Mode I, plane strain, small-scale yielding conditions is performed in a rate dependent plastic material characterized by the over-stress model. The main objective of the paper is to obtain theoretically the dependence of dynamic fracture toughness on crack speed. Crack propagation due to a ductile (micro-void) mechanism or a brittle (cleavage) mechanism, as well as transition from one mode to another are considered. The conversion from ductile to brittle has been observed experimentally but has received very little attention using analytical methods. Local fracture criteria based on strains and stresses are used to describe ductile and brittle fracture mechanisms. The results obtained in this paper are in general agreement with micro-structural observations of mode conversion during fracture initiation. Finally, the particular roles played by material rate sensitivity and inertia are examined in some detail. © 1992.

Acta Metallurgica Et Materialia

Dynamic growth of tensile cracks by ductile and brittle fracture mechanisms in a viscoplastic material

In this paper, steady-state, dynamic crack growth has been analysed under mode I plane stress, small scale yielding conditions using a finite element procedure. A Perzyna type, overstress viscoplastic constitutive equation has been employed in this analysis. A fracture criterion based on critical plastic strain has been imposed to obtain (theoretically) the variation of dynamic fracture toughness with crack speed, when crack propagation occurs in a ductile mode. The viscoplastic work rate is converted into heat input and the temperature rise distribution is determined by solving the governing conduction/convection equation, also by a finite element method. The effect of rate sensitivity and crack velocity on the fracture toughness and the temperature distribution have been clearly brought out in this study. © 1991.