Influence of nitrogen addition on the microstructure and mechanical properties of duplex stainless steel weld metals

Duplex stainless steels find extensive applications in off‐shore, paper/pulp, refineries and petrochemical industries owing to their excellent combination of properties. Because of the thermal cycle experienced during the manufacturing/processing operations like welding, the weldment developed in this material is generally inferior in properties (mechanical and corrosion) when compared to the base material. The problem is more severe when the welding is done in the autogenous condition. The current work correlates the microstructure and property of UNS 31803 duplex stainless steel (material no. 1.4462) welded by autogenous GTA process with and without nitrogen in the shielding gas. It has been found that the nitrogen addition to the weld metal through the shielding gas mixture not only helps in achieving the proper phase balance but also improves the impact toughness of the resultant weld metal.     

Synthesis,structure and characterization of ceramic Ca4Bi2Ti4Nb6O30

The polycrystalline samples of Ca₄Bi₂Ti₄Nb₆O₃₀ (herein designated CBTN) were synthesized by the conventional ceramic method. Preliminary X-ray structural study of the compound showed the formation of a single phase solid solution having orthorhombic structure in the paraelectric phase. Measurements of the dielectric constant (ε) and dielectric loss (tan δ) as a function of temperature (−180–200°C) at 1 kHz and 10 kHz and also as a function of frequency (10² Hz to 10⁴ Hz) at five different temperatures [−180°C, −40°C, − 10°C 26°C (room temperature) and 75°C] have shown a dielectric anomaly and a phase transition at − 13 ±1°C in CBTN.     

Textural and microstructural developments during fabrication of Zr-2.5Nb pressure tubes

Zr-2.5wt%Nb pressure tubes, as used in the Indian pressurized heavy water reactors (PHWR), are fabricated through a combination of hot extrusion followed by two stages of cold pilgering and annealing. The present study makes an effort to systematically characterize the textural changes during the fabrication stages. The starting single-phase hcp martensitic structure was textured to start with and it also went through strong texture developments during hot extrusion. First and especially the second pilgering modified the texture. Such modifications were related to local discontinuity of the softer second phase, as an apparent continuity restricted lattice rotation in the primary hcp phase. Annealing caused discontinuity or spherodization of the bcc phase, but did not create recrystallization in the hcp matrix. The combination of two pilgering plus annealing operations, though the latter did not cause noticeable texture changes, however, reverted the final texture close to the parent hot-extruded texture.     

On self-healing digital system design

In recent years there has been a significant growth of interest in exploiting the principles of biological processes to create powerful methodologies for solving computational problems. This paper discusses how these features have been exploited in digital hardware design. It also introduces an architecture for implementing self-healing digital systems that is inspired by the antigen protection mechanism employed by the human immune system. In the proposed architecture, a spare cell is dedicated to replace one in a group of four functional cells. Once one of these four functional cells is found to be faulty, the spare cell is cloned as the faulty cell. This architecture is especially suitable for tolerating soft errors in functional cells or on interconnect lines. Another major advantage of this architecture is that the outputs of functional cells are connected to the inputs of other physically adjacent functional cells, thus making it appropriate for nanocomputing system design.     

The HLD Study of Surfactant Partitioning for Oilfield Corrosion Inhibitors

The partitioning of corrosion inhibitor (CI) products is a measure of their potential to protect oilfield pipelines. In this paper the hydrophilic–lipophilic deviation (HLD) model is first used to quantify their partitioning in terms of the characteristic curvature (C _c,act) of a series of anionic (alkoxylated phosphate esters) and cationic (alkoxylated amines, aromatic amines, imidazoline acetates and quaternary amines) actives. This parameter is expressed over a range of pHs within which pipeline corrosion occurs. The HLD model is next used to predict the partitioning of each active from water into toluene at increased salinities. Linear mixing rules are lastly used to predict the characteristic curvature of Product A (C _c,mix) as a function of the C _c,act of a subset of actives.     

Lactobionic Acid as a New Synergist in Combination with Phosphonate-Zn(Ⅱ)System for Corrosion Inhibition of Carbon Steel

Studies on lactobionic acid introduced as a synergist in the presence of phosphonobutane-1,2,4-tricarboxylic acid(PBTC) and zinc ions for corrosion control of carbon steel in aqueous environment are presented.The investigations revealed that lactobionic acid(LBA) acts as an excellent synergist in corrosion inhibition.Optimum concentrations of all the three components of the ternary formulation are established by gravimetric studies.Potentiodynamic polarization studies indicate that the new ternary system is a mixed inhibitor.Impedance studies show that a protective film is formed on the metal surface in the presence of the inhibitor formulation.The film is found to exhibit its protective nature even at higher temperatures up to 60 °C.Analysis of the protective film by X-ray photoelectron spectroscopy(XPS) and reflection absorption Fourier transform infrared(FTIR) spectroscopy infers the presence of Zn(OH)_2,oxides and hydroxides of iron and the inhibitor molecules in the surface film probably in the form of a complex,[Zn(ll)—PBTC—LBA].The morphological studies by scanning electron microscopy(SEM) and the topographical studies by atomic force microscopy(AFM) also indicate the presence of protective film on the metal surface.A plausible mechanism of corrosion inhibition is proposed.     

Gurson model parameters for ductile fracture simulation in ASTM A992 steels

This study is concerned with the modelling the ductile fracture in ASTM A992 steels using the Gurson‐Tvergaard‐Needleman (GTN) model for high stress triaxiality regime. The GTN model for ASTM A992 structural steels is calibrated from the experiments performed on axisymmetrically notched tensile specimens. The experiments are designed to obtain a range of stress triaxiality and different fracture initiation locations. The non‐uniqueness in the constitutive parameters of the GTN model is illustrated in this study. The choice of a unique set of GTN constitutive parameters is made by choosing the nucleation strain (?_N) as a material constant. The process of estimating this material specific nucleation strain is provided. All the other GTN model parameters corresponding to the material specific nucleation strain (?_N) are evaluated to best fit the experimental results. The calibrated GTN model is shown to predict the load displacement behaviour, ductility and fracture initiation locations in the notched specimens. The calibrated GTN parameters are used to successfully predict the ductility of structural components: (a) bars with a hole; (b) plate with reduced section and (c) plate with holes; that are typically found in structural engineering applications.     

Drying of hot chilli using solar tunnel drier

A mixed mode type forced convection solar tunnel drier was used to dry hot red and green chillies under the tropical weather conditions of Bangladesh. The drier consisted of transparent plastic covered flat-plate collector and a drying tunnel connected in series to supply hot air directly into the drying tunnel using two fans operated by a photovoltaic module. The drier had a loading capacity of 80 kg of fresh chillies. Moisture content of red chilli was reduced from 2.85 to 0.05 kg kg⁻¹ (db) in 20 h in solar tunnel drier and it took 32 h to reduce the moisture content to 0.09 and 0.40 kg kg⁻¹ (db) in improved and conventional sun drying methods, respectively. In case of green chilli, about 0.06 kg kg⁻¹ (db) moisture content was obtained from an initial moisture content of 7.6 kg kg⁻¹ (db) in 22 h in solar tunnel drier and 35 h to reach the moisture content to 0.10 and 0.70 kg kg⁻¹ (db) in improved and conventional sun drying methods, respectively. The use of a solar tunnel drier and blanching of sample led to a considerable reduction in drying time and dried products of better quality in terms of colour and pungency in comparison to products dried under the sun. The solar tunnel drier and blanching of chilli are recommended for drying of both red and green chillies.     

Computation of entropy generation in dissipative transient natural convective viscoelastic flow

Entropy generation is an important aspect of modern thermal polymer processing optimization. Many polymers exhibit strongly non‐Newtonian effects and dissipation effects in thermal processing. Motivated by these aspects in this study, a numerical analysis of the entropy generation with viscous dissipation effect in an unsteady flow of viscoelastic fluid from a vertical cylinder is presented. The Reiner‐Rivlin physical model of grade 2 (second‐grade fluid) is used, which can envisage normal stress variations in polymeric flow‐fields. Viscosity variation is included. The obtained governing equations are resolved using implicit finite difference method of Crank‐Nicolson type with well imposed initial and boundary conditions. Key control parameters are the second‐grade viscoelastic fluid parameter (), viscosity variation parameter (), and viscous dissipation parameter (). Also, group parameter (), Grashof number (Gr), and Prandtl number (Pr) are examined. Numerical solutions are presented for steady‐state flow variables, temperature, time histories of friction, wall heat transfer rate, entropy, and Bejan curves for distinct values of control parameters. The results specify that entropy generation decreases with augmenting values of , , and Gr. The converse trend is noticed with increasing Pr and . Furthermore, the computations reveal that entropy and Bejan lines only occur close to the hot cylinder wall.