General Thin Rod Model for Preslip Bending Response of Strand

A general discrete thin rod model to study the preslip response of a strand of helical wires having wires-to-core friction contacts under constant curvature free bending has been developed for the case of Coulomb stick friction that considers together (a) all the three wire forces and three wire couples; (b) more appropriate equations for the wire shear forces; (c) the wire normal force as one of the contributors to strand bending moment; (d) wire external equilibrium; and (e) wire rolling with or without zero net shear on the strand cross section. The individual contributions of wire forces and couples to the strand bending moment for 10 models including EPRI model are compared. Several earlier models are shown to be special cases of the present general model.     

An investigation on the machinability of Al-SiC metal matrix composites using pcd inserts

The paper attempts to study the machinability issues of aluminium-silicon carbide (Al-SiC) metal matrix composites (MMC) in turning using different grades of poly crystalline diamond (PCD) inserts. Al-SiC composite containing 15%wt of SiC was used as work material for turning and PCD inserts of three different grades were used as cutting tools. Experiments were conducted at various cutting speeds, feeds and depth of cuts and parameters, such as surface roughness, specific power consumed, and material removal rate were measured. The worn surface of the insert was examined by scanning electron microscope (SEM). The surface finish observed was found to be much lower than the theoretical surface roughness. The influence of cut was examined for the different grades of PCD inserts. It was observed that the 1600 grade PCD inserts performed well from the surface finish and specific power consumption points of view closely followed by the 1500 grade.     

Prediction of tensile strength of friction stir welded aluminium matrix TiCp particulate reinforced composite

The usage of particulate reinforced metal matrix composite (MMC) is steadily increasing due to its properties such as high specific strength, high specific modulus and good wear resistance. Aluminium matrix composite (AMC) plays an important role to meet the above requirements. Effective utilization of AMC is based on not only its production but also on fabrication methods. Among AMCs, those based on particulate reinforcements are particularly attractive, due to their lower production costs. Aluminium matrix titanium carbide reinforced composite (Al–TiC_p) was produced in an inert atmosphere by indigenously developed Modified Stir Casting Process with bottom pouring arrangement (3–7% TiC by weight). Friction stir welding process (FSW) is employed to make weld joints. The welding parameters such as axial force, welding speed, tool rotational speed, percentage TiC addition etc., and profile of the tool were considered for analysis. In this study, an attempt is made to predict ultimate tensile strength (UTS) of the welded joints using a mathematical model. The FSW specimens without any post-weld heat treatment belonging to a different set of parameters tested, exhibited a high joint efficiency (most of them ranging from 90% to 98%) with respect to the ultimate tensile strength of the base material AA6061. It was found from the analysis of the model that the tool pin profile and the welding speed have more significant effect on tensile strength.     

Local inhomogeneity and surface degradation of Fe1.15Te and Fe1.03Te0.62Se0.38 single crystals

We have investigated the structural and magnetic properties of Fe_1.15Te and Fe_1.03Te_0.62Se_0.38 single crystals grown by slow cooling method using a specially designed double-walled quartz ampoule. X-ray diffraction reveals significant local inhomogeneity as a result of fractional substitution of Te site by Se in single crystal Fe_1.03Te_0.62Se_0.38. The existence of superconductivity is confirmed for Se substitution to the Te site of Fe_1.03Te_0.62Se_0.38 but with persistent Fe₇Se₈ impurity phase. Raman spectroscopy confirmed the surface structural instability when the samples were exposed to moderate laser irradiation in the atmospheric environment. With high intensity laser irradiation, Fe(Se,Te) compounds can be decomposed into Fe₂O₃ hematite phase.     

Grafting of glycidylmethacrylate onto demineralized xenogeneic bone in aqueous medium

Summary Demineralized xenogeneic bone (DXB) was prepared from bovine cortical tibia and graft copolymerized with glycidylmethacrylate (GMA) using a combination of potassium persulfate (K₂S₂0₈) and sodium metabisulfite (Na₂S₂O₅)as redox initiating system in aqueous medium. To optimize the reaction condition, the concentrations of backbone, monomer, initiator, temperature and time were varied. The percent grafting was found to increase initially and thereafter decrease in most of the cases. The optimum temperature and time were found to be 40°C and 180 minutes, respectively. The grafting results have been discussed and a reaction mechanism is proposed. Functional groups and structural changes of the graft copolymer were determined by Fourier transform infrared (FT-IR) spectroscopic method for proof of grafting and the results are discussed. Received: 12 August 2002/Revised version: 30 October 2002/ Accepted: 25 November 2002 Correspondence to R. Murugan     

Hybridization of genetic algorithm with immune system for optimization problems in structural engineering

Optimization is the task of getting the best solution among the feasible solutions. There are many methods available to obtain an optimized solution. Genetic algorithm (GA), which is a heuristic type of optimization method, is discussed in this paper. The focus of the paper is the use of GA for large dimensionality design problems, where computational efficiency is a major concern. The motivation of this paper is to hybridize GA with an immune system mechanism by avoiding the implementation of penalty constants, which are highly sensitive to the choice of algorithm parameters. The principal advantage of the immune system is in its seamless integration with GA-based search for optimal design. It is being hybridized with the immune system mechanism. The hybrid GA and immune system is applied for the design of the optimal mix of high-performance concrete (HPC), which is still based on trial mix and for which no rigorous mathematical approach is available. As such, to infer the values of strength and slump, a wavelet back propagation neural network or wavelet neural network is used for any HPC mix. It is necessary to minimize the cost of HPC/unit weight of HPC subjected to strength and slump constraints. The interwoven algorithm is also applied to obtain optimal sectional areas for minimum weight of space trusses subjected to static loading. Formian programming language is used for the generation of the space trusses, and Feast package is used for the static analysis of the trusses. In addition to the induction of immune system in the GA for constraint handling, it is being applied in this particular application for improving the search of GA in obtaining the best optimal solution. For obtaining the optimal sections of space trusses subjected to earthquake loading, SAP 90 package is used, and reliable results are obtained.     

Prediction of Humidification Power in Textile-Spinning Mills Using Functional and Neural Networks

The power required for the supply, pumping, and exhaust system of the humidification plant of a spinning department of a textile mill depends on many factors. The most important factors are power of motor driving machinery, lighting and heating load, number of people inside, temperature gradient, and relative humidity. The usual procedure is to train the back-propagation neural network (BPN) with the available data and, once it is trained, BPN will be used for inferring. Some other investigators have used different neural network architectures. In this article, we give a general methodology to build and work with functional network (FN), an alternative to neural network paradigm. In this architecture neural functions, instead of weights, are learned. In addition to data, domain knowledge can also be incorporated. It is shown by means of an example that this functional network architecture is successfully applied to predict power required for the humidification plants.     

A note on plotting curves

In this note it is pointed out that sometimes there may be difficulties in plotting a curve using the well known interpolation techniques, and in such cases, “isoparametric style of” interpolation may be used for better accuracy.