Advanced Materials Research Vols. 62-64

Abstract: With increased product dynamics world-wide, the average economic lifetime of production systems is falling. Industrial robots are widely assumed to be inherently flexible and therefore that they can function as a programmable building block of response production systems. This paper reviews common capabilities of contemporary industrial robotic systems and investigates their capability to extend the useful lifetime of production system by coping with different types of product dynamic. Also considered are relative capabilities of conventional programmable robots and an emerging generation of programmable and configurable component-based machines.

Abstract: To cope with high levels of complexity, competition and change requirements, manufacturing enterprises (MEs) need to continuously improve their process and resource system performances. Enterprise Modelling (EM) is considered a prerequisite for enterprise integration and performance improvement because it can be used to capture relatively enduring knowledge about any specific business environment in which production systems will be deployed. With this prerequisite in mind, EM principles were deployed to capture and develop ‘static’ models of an SME. This provided detailed descriptions of enterprise production operations and their precedence relationships. A discrete event simulation tool was then used to develop time dependent ‘dynamic’ models of selected process segments of the specific case Enterprise Model. This allowed the computer execution of alternative production system designs to be assessed under SME specific changing scenarios and enabled suggestions for potential improvements to be made.

Abstract: In this study, investigations were carried out on the corrosion behaviour of low carbon steel (mild steel) in the selected media which are cassava extracts, sodium chloride solution (brine), lubricating oil, distilled water and atmospheric air. The test pieces, after chemical analysis were machined to similar dimensions. Each of the specimens was immersed into equal volumes of the selected media except one for the atmospheric air which was placed in the open air. The weight and hardness measurements were carried out every five days for a period of twenty-five days and loss in weight and hardness of the specimens were determined in succession. The results obtained showed that mild steel was more susceptible to corrosion in cassava extracts, sodium chloride and distilled water, than in lubricating oil and atmospheric air. Follow up statistical test results showed that loss in weight is significant for cassava extracts when compared with other media.

Abstract: . Immobilization of an amine-containing peroxide macroinitiator APM onto solid mineral surfaces has been achieved via physical/chemical adsorption of its macromolecules from solution. A systematic variation of reaction parameters upon graft polymerization initiated by surface-attached APM including nature of monomer and solvent has been conducted. The effect of solvent and nature of monomer on the overall constant of polymerization, effective activation energy, initiation efficiency as well as other parameters of elementary stages of the process has been established. It has been revealed that the involvement of TiO2 particles with the surface-attached radicals in the heterogeneous polymerization process profoundly influenced all the elementary stages, particularly chain transfer and termination.

Abstract: Different methods of obtaining averages have been used to determine mean rolling temperatures from measured temperatures of various specimens during roll contact in hot flat rolling. The obtained mean rolling temperatures were used in turn in hot rolling simulation programs based on Sims, and Bland and Ford’s theories for calculating rolling loads and torque during hot flat rolling of steels at low strain rates (0.08 – 1.5 s-1). The hot rolling Bland and Ford’s (HRBF) Theory and Sim’s Theory gave similar results when any of the averaging methods of temperature is used to calculate rolling load and torque at high strain rates (1.5 –500s-1). However at low strain rates HRBF gave closer approximations to experimental results. Comparing the results with experimental values, the harmonic mean was found to give the best mean rolling temperature for hot flat rolling simulation at low strain rates compared to geometric mean, arithmetic mean and root mean square.

Abstract: Rubber seed oil monoglyceride was prepared by glycerolysis and characterized by chemical and spectroscopic methods. The monoglyceride was reacted with excess diisocyanates (hexamethylene -diisocyanate and toluene diisocyanate), and the network structures and molecular mass of the polyurethane were determined from swelling experiments in toluene and size exclusion chromatography respectively. The polyurethane films obtained were characterized in terms of their resistance to chemicals (water, brine, dilute acid and alkali) thermal stability and tensile and flexural strength and modulus. It was found that under the experimental conditions, conversion of the triglyceride content of the rubber seed oil to monoglyceride not quantitative less than 70%. The measured properties of the RSO-based polyurethanes were attributed to the degree of crosslinking and the observed superior properties of the polyurethane obtained with hexamethylene diisocyanate in comparison with polyurethane obtained with toluene diisocyanate were explained in terms of structure-property relationship. The measured properties of RSO-based polyurethanes compare favourably with the properties reported for polyurethanes derived from other vegetable oils.

Abstract: Divalent metal (barium, cadmium, calcium and zinc) soaps of rubber seed oil and their binary mixtures (Ba/Cd and Ca/Zn) and epoxidized rubber seed oil (4.5% epoxide content) and its admixtures with the single divalent metal soaps were evaluated as thermal stabilizer for dioctylphthalate plasticized PVC using changes in discolouration indices (yellowness index and UV absorption at 360nm) and initial rates of dehydrochlorination measured at 140 and 160oC. The results obtained showed that the divalent metal soaps were relatively effective in stabilizing the dioctylphthalate plasticized PVC against thermal degradation and that the binary soap mixtures enhanced the heat stabilizing effectiveness: marked reduction in the values of the discolouration indices; longer dehydrochlorination induction period and smaller values of rate constant of initial rate of dehydrochlorination. It was found that epoxidized rubber seed oil was less effective in comparison with the divalent metal soaps in stabilizing plasticized PVC against thermal degradation. These results show that the bio-based additives are compatible with dioctylphthalate plasticized PVC, stable to heat within the range of temperature used in the processing of plasticized PVC, inhibit/retard dehydrochlorination and reduce the extent of degradation.

Abstract: This paper investigates the microstructural induced hardness variation in multirun welded plain carbon steel at different interpass time. Beveled 16mm thick mild steel samples were welded in 2 and 4 passes at interpass time of 90, 120 and 240s respectively via manual metal arc. The result showed that the differences in hardness values of the fusion zone and heat affected zone reduce as interpass time increases for both 2 and 4 runs. The effect was however quite distinct in the 4 runs welding cycle. In the 2 run cycle, the fusion zone and heat affected zone merge at 100 seconds; while in the 4 runs cycle, the merging occurred at 25 seconds; indicating that the higher the multipass, the shorter the time required to produce uniformity in hardness and structural homogeneity. Thereby increasing the resistance of the weld to crack susceptibility and failure. At these instances, the microstructure revealed fine grained pearlite interpassed in martensite.

Abstract: Powdered activated carbons were produced from palm kernel shells, corn cobs and cow bones by carbonization, pulverization and activation. The resulting granule has a surface area of 430.04 m2/g, 4022.15 m2/g and 733.60 m2/g respectively with controlled pore size. The characterized surface area enables the carbon to absorb vapors from gases, and substances from liquids. The surface properties are function of the base materials used in the preparation. Determinations of their adsorptive capacities show that activated carbon prepared from corn cobs has the highest adsorptive capacity. The surface properties are function of the base materials used in the preparation. Determinations of their adsorptive capacities show that activated carbon prepared from corn cobs has the highest adsorptive capacity.

Abstract: In this work, the permeability characteristics of Nigerian coal seams were determined and these properties were used to investigation the applicability of water infusion in the coal seams to solve coal-mining problems. The experimental work was conducted with Triaxial Compression Machine adapted for the permeability test comprising of Hoek cell, a self- developed water piston, pressure gauge and an overhead water tank. The results of the investigation showed that the permeability measurements of the coals were consistent at the different sites and locations of the coalmines. It also revealed that the difference in coal seam permeability was relatively small in Nigeria.