Indian
Journal of Engineering & Materials Sciences
Vol.
16, October 2009, pp. 295-300
Fracture analysis for a non-homogeneous weldment with a crack parallel to the interface
Yong-Dong Li, Hong-Cai Zhang
& Kang
Yong Lee
Fracture modeling and analysis are of significance in the design and evaluation of weldments. Based on a new four-zone model, the present work performs anti-plane fracture analysis on a non-homogeneous weldment consisting of four different kinds of zones: base metal, heat affected zone (HAZ), fusion zone and weld metal. The HAZs and fusion zones are modeled as functionally graded materials. A crack parallel to the interface is assumed to be in the HAZ or weld metal. The crack problem is solved by the methods of Fourier integral transform and dual integral equation. Parametric studies on the stress intensity factors yield two conclusions for the current fracture model of the four-zone weldment. (i) The optimal value of the mismatch factor is 1.0. The increase in mismatch factor will decrease the driving force of a HAZ crack, but it will enhance that of a weld-metal crack. In engineering, mismatch factors too larger or too smaller than 1.0 should be avoided. (ii) The effect of non-homogeneity parameter embodies that of the relative stiffness of the crack-tip region. Stiffer crack-tip region may induce larger driving force for the crack.
Keywords: Weldment, Mismatch factor, Heat affected zone, Fracture, Functionally graded materials
Indian
Journal of Engineering & Materials Sciences
Vol.
16, October 2009, pp. 301-309
Fundamental studies on buoyancy-aided conjugate mixed
convection with surface radiation from a discretely heated vertical
electronic board
S M Sawant & C Gururaja
Rao
The present paper reports numerical results related to the problem of buoyancy-aided conjugate mixed convection with surface radiation from a discretely heated vertical electronic board. The board is equipped with three flush-mounted discrete heat sources of identical dimensions and volumetric heat generation, while air is used as the cooling medium. The governing continuity, Navier-Stokes and energy equations are taken without boundary layer approximations and are solved using finite volume method with the help of stream function–vorticity formulation. An extended computational domain is considered and is discretised with 151 grids along and 111 grids across the board. The nature of variation of local board temperature distribution, peak board temperature, local drag coefficient, mean friction coefficient and relative contributions of mixed convection and radiation to board heat dissipation with reference to some of the pertinent independent parameters has been looked into. Also, some of the contour plots related to isotherm distribution in the computational domain for typical sets of working conditions have been provided.
Keywords: Buoyancy-aided conjugate mixed convection, Surface radiation, Electronic board, Discrete heat sources, Maximum board temperature, Mean friction coefficient
Vol. 16, October 2009, pp. 310-318
Effects
of ferrochromium slag with neat and polymer modified binders in hot
bituminous mix
Mehmet Yilmaz & Baha Vural
Kok
In this study the
properties of hot bituminous mix containing ferrochromium slag with neat and
styrene-butadiene-styrene modified binders have been investigated. The
ferrochromium slag is used as coarse aggregate and total aggregate. Three
different binders, B 50/70, B 160/220 and B
160/220+3% SBS, are used in mixtures. The physical and mechanical properties
of polymer modified binders and binder-aggregate mixes are evaluated in terms
of their fundamental engineering properties such as dynamic shear rheometer
(DSR), rotational viscometer (RV) for binders, Marshall stability, indirect tensile stiffness modulus, tensile strength and
moisture susceptibility for mixtures. It has been concluded through the
laboratory tests that using ferrochromium slag as coarse aggregate provided
satisfactory results. The usage of ferrochromium slag as total aggregate does
not exhibit good performance in terms of stability and stiffness modulus.
However, the mixtures prepared entirely with ferrochromium slag showed good
resistance to moisture damage. It is found that in spite of the similarity
between high temperature performance grades of B 50/70 and B 160/220+3% SBS,
the mechanical properties of the mixtures prepared with these binders do not
show the same performance.
Keywords: Hot bituminous mix, Ferrochromium slag, Stability,
Stiffness modulus,
Indian
Journal of Engineering & Materials Sciences
Vol.
16, October 2009, pp. 319-325
Interfacial studies of polyamide 6 composites filled with oxidation carbon fiber
J Li & Y C Xia
In this work, ozone modification method and air-oxidation are used for the surface treatment of polyacrylonitrile(PAN)-based carbon fiber. The surface characteristics of carbon fibers are characterized by X-ray photoelectron spectroscopy (XPS). The interfacial properties of carbon fiber reinforced polyamide 6 (CF/PA6) composites are investigated by means of the single fiber pull-out tests. As a result, it is found that IFSS values of the composites with ozone treated carbon fiber are increased by 60% compared to that without treatment. XPS results show that ozone treatment increases the amount of carboxyl groups on carbon fiber surface, thus the interfacial adhesion between carbon fiber and PA6 matrix is effectively promoted. The effect of surface treatment of carbon fibers on the tribological properties of CF/PA6 composites is investigated. Experimental results reveal that surface treatment can effectively improve the interfacial adhesion between carbon fiber and PA6 matrix. Thus, the wear resistance is significantly improved.
Keywords: Ozone, CF/PA6 composite, Single fiber pull-out, Interfacial adhesion
Indian
Journal of Engineering & Materials
Sciences
Vol.
16, October 2009, pp. 326-330
Comparison of mechanical properties of boronized and vanadium carbide coated AISI 1040 steels
A Calik, F Taylan, O Sahin
&
Comparison of mechanical properties of medium carbon steel AISI 1040
for vanadium carbide coated (VCC) and boronized conditions has been studied
by means of microhardness, tensile and impact tests. For the treated steels, the boriding and
vanadizing processes have been carried out in the same conditions, i.e., at a
temperature of 1210 K for 4 h. The thickness of diffusion layer
has been measured as 5 µm and 100 µm for the VCC
and the boronized steels, respectively. In laboratory conditions, the VCC
steels show considerably higher strength and surface hardening with respect
to the untreated and the boronized steels. At the same time, Charpy
V-notch impact tests have also been carried out for the steels with and
without surface hardening. It is concluded that
coating is effective in improving the mechanical performance of AISI 1040
steels.
Keywords: Vanadium carbide coating, Boronizing, Impact toughness, Borides, Notch
Indian
Journal of Engineering & Materials Sciences
Vol.
16, October 2009, pp. 331-334
Methodology to evaluate the
quality of diffusion bonded
joints by ultrasonic method
The quality and the soundness of diffusion bonded joints are generally evaluated by metallographic techniques, shear strength/tensile strength etc. Since these conventional methods are of destructive in nature, inspection on actual products is difficult. Therefore, non-destructive testing of diffusion bonded joints is required to evaluate the quality and to study the interphase properties. The ultrasonic A-scan method is suitable for diffusion bonded joints, since the sensitivity is 0.01-0.0001% as compared to the X-ray and Gamma ray methods having sensitivity of 0.5-2% only. In the present work, Ti-6Al-4V was bonded with Ti-6Al-4V at 1073 K at varying pressures of 1.6-4 MPa for a bonding time of 4 h so as to obtain bonds with interfaces of varying bonded area fraction. The shear strength of the bond is correlated with bonded area fraction which is measured using metallographic technique. The bonded samples are tested using ultrasonic flaw detector for the soundness of the joints. The ratio between the amplitude of interface wall echo to amplitude of surface echo is calculated and correlated with the bonded area fraction.
Keywords: Diffusion bonding, Ultrasonic, Ti-6Al-4V, Strength ratio
Indian
Journal of Engineering & Materials Sciences
Vol.
16, October 2009, pp. 335-340
Growth and characterization of tetravalent doped LiCoO2 thin film cathodes
M
C Rao & O M Hussain
Titanium-doped LiCoO2 thin
films are grown by pulsed laser deposition technique on silicon substrates.
Structure, AFM, FTIR and Raman are studied with respect to their deposition
parameters, i.e., substrate temperature (Ts)
and oxygen partial pressure (pO2) in the deposition chamber. The
films deposited in pO2 = 100 mTorr showed good crystallinity on
silicon substrates maintained at Ts = 700°C. It is found that such a film crystallizes in the layered α-NaFeO2 structure. The influence
of titanium doping on particle size and morphologies has been
clearly studied. FTIR spectra displayed the
characteristic IR dominant bands at 246 and 550 cm–1 for titanium
doped LiCoO2 thin films. The Raman peaks observed for the films at
594 cm-1 and 485 cm-1 are ascribed to Raman active
modes A1g and Eg respectively. The
electrochemical measurements were carried out on Li//LiTiyCo1-yO2 cells. The Li//LiTiyCo1-yO2cell delivered a specific capacity of 225 mC/mm cm2. The influence of titanium doping on
the structural and electrochemical properties has been systematically
studied.
Keywords: Ti doped LiCoO2 PLD films, XRD, AFM, Raman and electrochemical
Vol. 16, October 2009, pp. 341-346
Innovative
low pressure borophosphosilicate glass processes for nano devices
T Jagadeesha, Louis Kim,
Joseph Gonsalvis & Thammaiah Gowda
Doping of oxide with phosphorous can trap mobile ions and reduce the re-flow temperature. By adding boron the reflow temperature can be reduced further without excessive phosphorous, which may cause metal corrosion. Borophosphosilicate glass (BPSG) and phosphosilicate glass (PSG) processes are mainly used for premetal dielectric (PMD) applications. In the present study, a new low pressure BPSG process has been developed which can be used for Flash memory and Logic devices. It is shown that films with phosphorus and boron concentrations in the range of 1.85-9.15 elemental wt% are deposited with film thickness 6000 Å BPSG and 100 Torr process has been found to achieve more stable film thickness. Decreasing the deposition pressure from 200 to 100 Torr results in a 50% increase in the deposition rate of twin-wafer SACVD BPSG and has zero effect on film properties. Throughput has been improvement by 20% on SACVD PMD BPSG application.
Keywords: BPSG, PSG, Low pressure BPSG
Indian
Journal of Engineering & Materials Sciences
Vol.
16, October 2009, pp. 347-354
Preparation, characterization and conductivity studies of
NaAlSb(PO4)3 and HAlSb(PO4)3
NaAlSb(PO4)3 and HAlSb(PO4)3 are prepared by solid-state and
metathesis reactions respectively. They are characterized by powder XRD, IR
and solid-state 31P-MAS NMR spectroscopy. These two compounds crystallize
in the hexagonal NASICON structure with the space group of
. Their infrared spectra exhibit characteristic vibrational
bands of PO4 tetrahedra. The 31P-MAS NMR spectra of
NaAlSb(PO4)3 and HAlSb(PO4)3 are
characterized by a symmetric single peak around 9 ppm suggesting only one
type of phosphorous in the hexagonal lattice. The activation energies for
conduction and relaxation are more for NaAlSb(PO4)3 compared to the values of HAlSb(PO4)3. The isothermal
conductivity of NaAlSb(PO4)3 is higher than the
conductivity of HAlSb(PO4)3. The imaginary parts of the
impedance, (Z¢¢)
and electric modulus (M¢¢)
against log frequency show single peaks in both Z¢¢ and M¢¢ spectra.
Indian
Journal of Engineering & Materials Sciences
Vol.
16, October 2009, pp. 355-363
Charge transport and ammonia sensing response in poly (aniline-co-1-amino-2-naphthol-4-sulphonic acid)
Vineet Bansal, M C Bansal
& S K Dhawan
The paper reports the synthesis of tubes of poly (aniline-co-1-amino-2-naphthol-4-sulphonic acid) using para toluene sulphonic acid as a dopant. The copolymers have the conductivity of the order of 0.348 S/cm to 0.198 S/cm depending on the ratio of the co-monomers present in the feed ratio. The morphology of the copolymers was studied by scanning electron microscope. Electrical conduction have been studied in the temperature range from 300 K to 30 K. Charge transport has been attributed as tunnelling in the range 30 K to 70 K. Above 70 K, charge transport is represented by Mott’s three-dimensional variable hopping. The copolymer has been found to be a better ammonia vapour sensing material and can be used for detection for varying concentration.
Keywords: Conducting polymer, Polyaniline, Copolymer, Nanotubes, Scanning electron microscopy, Charge transport
Indian
Journal of Engineering & Materials Sciences
Vol.
16, October 2009, pp. 364-366
Critical assessment of Flory’s approach
for estimating miscibility gap in binary monotectic systems
Sanjay Chaubey
Flory’s solution approach, which gives
expression for the free energy of mixing of binary alloys whose constituent
atoms differ largely in size, has been used to find the required model
parameters in terms of which expressions for critical temperature
and critical
composition (
have been derived. Model parameters are capable of
describing the thermodynamic behavior of the liquid phase and are useful in
constructing the miscibility gap in binary monotectics. Within the limits
fairly good agreement has been observed between theoretically calculated and
experimentally observed values of
and
along with the
reasonable data for the various thermodynamic functions at the desired
temperature in four binary monotectic systems chosen for the present study.