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CONTENTS
Volume 4, Number 1, March 2015
 

Abstract
Low carbon steel of composition 0.05C – 0.18 Mn – 0.012 Si is intercritically annealed at temperatures 750oC, 775oC and 800oC. The equilibrated alloys of different amounts of austenite with varying carbon contents are quenched in iced water. The same alloys are subcritically annealed at 675oC and 700oC for varying periods of times; the subcritically annealed alloy samples are quenched in iced water. Optical, scanning electron and transmission electron microscopy are carried out for all the samples. The dislocation structure, its distribution and density present in the above prepared duplex ferrite martensite steels are studied. The martensites are found to be highly dislocated due to lattice invariant deformation. At the same time ferrite adjoining the martensite areas also exhibits quite a high dislocation density. The high dislocation density is favorable for strain ageing and hence bakes hardenability. EDS analyses were carried out for both martensite and ferrite phases; it is found that the degree of supersaturation in ferrite together with carbon content in martensite varies with the process parameters. The microhardness test results show that the hardness values of different phases differ appreciably with process parameters. The microstructures and the corresponding microanalyses reveal that differently processed steels contain phases of varying compositions and different distribution.

Key Words
bake hardening; intercritical annealing; dual phase steel; martensite; Cottrell atmosphere

Address
M.K. Banerjee: Department of Metallurgical and Materials Engineering, MNIT Jaipur, Jaipur 302017 India

Abstract
Concrete suffers strength loss when subjected to elevated temperatures during an accidental event such as fire. The loss in strength of concrete is mainly attributed to decomposition of C-S-H gel and release of chemically bound water, which begins when the temperature exceeds 500

Key Words
heating; retention; cooling; strength loss; blended concrete

Address
Subhash C. Yaragal, Jishnu Warrier and Ramesh Podila: Department of Civil Engineering, National Institute of Technology Karnataka, Surathkal – 575 025, Mangalore, Karnataka, India

Abstract
Energy absorption and exposure buildup factor have been computed for natural uranium in the energy range of 0.05-15MeV up to penetration depth of 40 mfp. Five-parameter geometric progression (G-P) fitting method has been used to compute buildup factors of uranium. The variation of energy absorption and exposure buildup factors with, penetration depth and incident photon energies for the uranium has been studied. It has been concluded that the values of energy absorption and exposure buildup factors are very large at 0.15 MeV.

Key Words
energy absorption buildup factor; exposure buildup factor; uranium; GP fitting method

Address
Danial Salehiand Dariush Sardari: Department of Radiological and Nuclear Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran

M.S. Jozani: Faculty of Engineering, Islamic Azad University, South Tehran Branch, Tehran, Iran

Abstract
This paper presents a simple n-order four variable refined theory for buckling analysis of functionally graded plates. By dividing the transverse displacement into bending and shear parts, the number of unknowns and governing equations of the present theory is reduced, and hence, makes it simple to use. The present theory is variationally consistent, uses the n-order polynomial term to represent the displacement field, does not require shear correction factor, and eliminates the shear stresses at the top and bottom surfaces. A power law distribution is used to describe the variation of volume fraction of material compositions. Equilibrium and stability equations are derived based on the present n-order refined theory. The non-linear governing equations are solved for plates subjected to simply supported boundary conditions. The thermal loads are assumed to be uniform, linear and non-linear distribution through-the-thickness. The effects of aspect and thickness ratios, gradient index, on the critical buckling are all discussed.

Key Words
nth-order four variable refined theory; functionally graded plates; thermal buckling

Address
Z. Abdelhak, L. Hadji and T.H. Daouadji: Université Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algérie

L. Hadji, T.H. Daouadji and E.A Bedia: Laboratoire des Matériaux & Hydrologie, Université de Sidi Bel Abbes, 22000 Sidi Bel Abbes, Algérie

Abstract
This paper aimed to investigate the effect of MWCNTs on properties of slag Geopolymeric mortar. Geopolymeric matrices containing different MWCNTs concentrations (0.0, 0.1, 0.2, 0.3 and 0.4 % by weight of the used binder) were synthesized. The Geopolymer mortar composed of aluminosilicate slag to sand (1:2), while the alumino silicate source binder composed of 50% air cooled slag and 50%water cooled slag both passing a sieve of 90

Key Words
MWCNT; Geopolymer; mortar; water cooled slag; air cooled slag

Address
H.M. Khater and H.A. Abd el Gawaad: Housing and Building National Research Centre (HBNRC)
87 El-Tahreer St., Dokki, Giza, P.O. Box 1770 Cairo


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