Role of transformed martensite in the cracking of stainless steel plumbing lines

Austenitic stainless steel AISI 321 is used to fabricate plumbing lines to transfer cryogens from storage to output collector of propulsion system. Cracks were found in some of such tubes during one of the qualification tests of pipelines. The crack occurred at the bent region of the fuel feed pipeline along its neutral axis. Detailed metallographic investigations revealed presence of numerous longitudinal fine cracks on the inner surface of the tube that resulted from improper extrusion of the tube. Further, deformation induced martensitic transformation occurred, as the tube was bent at liquid nitrogen temperature. The transformed martensite, in presence of fine cracks on inner surface of the tube, due to improper extrusion, resulted in crack opening. This paper highlights the details of investigations carried out.     

Optimization of bead geometry in electron beam welding using a Genetic Algorithm

Bead-on-plate welds were carried out on austenitic stainless steel plates using an electron beam welding machine. Experimental data were collected as per central composite design and regression analysis was conducted to establish input–output relationships of the process. An attempt was made to minimize the weldment area, after satisfying the condition of maximum bead penetration. Thus, it was posed as a constrained optimization problem and solved utilizing a Genetic Algorithm with a penalty function approach. The Genetic Algorithm was able to determine optimal weld-bead geometry and recommend the necessary process parameters for the same.     

Non-destructive determination of acid–brix ratio of tomato juice using near infrared spectroscopy

Consumer's acceptance of tomato juice depends on its sourness to sweetness ratio and measuring this is important for quality control and marketing. Traditional methods destroy the samples, are time consuming and cannot be used in continuous packing or bottling systems. A non‐destructive method of quality evaluation, using near infrared (NIR) techniques, was tested, by using a portable NIR measuring unit. Spectra of tomato juice of known acid and brix values were determined and, in the wavelength range 703–1124 nm (NIR), a calibration model for acid–brix ratio (ABR) was developed, by using unscrambler software. When used to predict ABR of tomato juice statistical analysis showed minimal standard error (0.009) and satisfactorily high correlation coefficients (0.92) over the wavelength range 1059.5–1124.8 nm, for both calibration and prediction. These values were hardly different from analytical results and the NIR model has potential for non‐destructive prediction of ABR of tomato juice.     

Effect of age on P300 wave

A case of unicystic ameloblastoma which recurred after 15 years showing unusual histological features is reported. The prominent pseudo-glandular features present are described. This case highlights the importance of extensive histological examination for more characteristic features of ameloblastoma to reach a correct diagnosis.     

Novel geodesic splitting on paraboloid of revolution with applications to ray-theoretic analysis

Computer simulations have shown a novel geodesic splitting on the paraboloid of revolution leading to a multiplicity of surface ray paths. Such a phenomenon would have wide ramifications for wave propagation problems in general, besides applications in target-detection problems and the computational requirements of ray-theoretic formulations such as the UTD, in computing the antenna characteristics in the high-frequency domain.<>     

Java implementation of policy‐based bandwidth management

We describe a Java implementation of a policy based bandwidth management system using the standard policy protocols and an interface to the Linux Diffserv implementation. The useful features, such as extensibility and object orientation, of the Java implementation is illustrated by directly referring to the relevant programming codes. Through two practical experiments, we demonstrate the capability of our implementation in supporting policy‐based dynamic resource allocations in enterprise networks. Copyright © 2003 John Wiley &Sons, Ltd.     

Phase Constitution During Sintering of Red Mud and Red Mud–Fly Ash Mixtures

The phase constitution during the sintering of pure red mud and red mud–fly ash mixtures was studied in the temperature range of 900°–1250°C. The phases formed at different sintering temperatures were analyzed by X-ray powder diffraction. The phases that are likely to form at equilibrium at any isotherm were predicted using the Gibbs free energy minimization technique and the databases provided in the FactSage software. Although the thermodynamic prediction is in reasonable agreement with the experimental results for the major phases, there is some disagreement regarding the minor phases, especially the more complex phases. The major limitation of the thermodynamic approach presently is the non-availability of thermodynamic data for several complex and multi-component solution phases.     

A higher-order shear and normal deformation functionally graded plate model: some recent results

A higher-order shear and normal deformations plate theory is employed for stress analysis and free vibration of functionally graded (FG) elastic, rectangular, and simply (diaphragm) supported plates. Although functionally graded materials (FGMs) are highly heterogeneous in nature, they are generally idealized as continua with their mechanical properties changing smoothly with respect to the spatial coordinates. This idealization is required in order to obtain the closed-form solutions of some fundamental solid mechanics problems and also simplify the evaluation and development of numerical models of the structures made of FGMs. The material properties of FG plates such as Young’s moduli and material density are considered in this case to vary continuously in the thickness direction according to the volume fraction of constituents and mathematically modeled as exponential and power law functions. Poisson’s ratio is assumed to be constant. The effect of variation of material properties in terms of material grading index on the deformations, stresses, and natural frequency of FG plates is studied. The accuracy of the presented numerical solutions has been established with the solutions available of other models and the exact three-dimensional (3D) elasticity solutions.     

Structural,electronic, and optical properties of orthorhombic and triclinic BiNbO4 determined via DFT calculations

We performed ab initio calculations using the FPLAW method with the local density approximation (LDA) implemented in the WIEN2 k code for the orthorhombic (α) and triclinic (β) phases of BiNbO₄. The modified Becke–Johnson exchange potential (mBJ)-LDA approach was also used to improve the electronic properties. The lattice constants calculated for both structures using the LDA are in good agreement with the experimental values. For the band structure calculations, the mBJ-LDA approach provides reasonable agreement for the band gap value compared with the LDA. The estimated (mBJ)-LDA band gap values are 2.89 eV (3.73 eV) and 2.62 eV (3.15 eV) for the α and β phases of BiNbO₄, respectively. Significant optical anisotropy is clearly observed in the visible-light region. We also calculated and evaluated the electron energy loss spectrum for BiNbO₄. This work provides the first quantitative theoretical prediction of optical properties and electron energy loss spectra for both the orthorhombic and triclinic phases of BiNbO₄.     

Enhancement of electrical properties and blue emission due to nanostructuring of BaZr0.05Ti0.95O3 ferroelectric ceramics

Nano-structuring of various ferroic materials has tailored the existing properties in their bulk counterpart. Keeping this fact in view, nano-crystalline barium zirconate titanate (BaZr_0.05Ti_0.95O₃) ferroelectric ceramics were prepared by mechanical activation process using high-energy planetary ball milling followed by the sintering process. In the present work, effect of milling duration (15, 30 and 45 h) on structural and microstructural properties has been observed with the help of X-ray diffraction, scanning electron microscopy and transmission electron microscopy (for optimized milling duration). The crystallite size of the milled specimen decreases to 14.17 nm on increasing the milling duration from 15 to 45 h. A comparison with its bulk counterpart showed significant enhancement in di-, ferro-, piezo- and pyro-electric properties with strong blue emission in UV light (265 nm). The blue emission in UV light makes it a potential candidate for LEDs and optical devices.