Development of empirical model for abrasive wear volume of sisal fibre–epoxy composites

Abstract

In this paper, an empirical model was developed for high stress abrasive wear behaviour of unidirectional sisal fibre reinforced epoxy composites under varying operating parameters, for which a number of experiments were carried out to determine the abrasive wear behaviour of the composites. Polysulphide modified epoxy resin was used to make composites having three different sisal fibre concentrations in three different fibre orientations, namely longitudinal, transverse and normal. Abrasive wear of composites depends on operating parameters, such as applied load, grit size, sliding distance and weight percentage of sisal fibre. The abrasive wear data have been analysed using statistical analysis, and empirical relations are proposed.     

Cold model study of metal droplet descent through fluids including a treatment of the non-Newtonian behaviour as exhibited by molten slag system

Abstract

In the context of several high temperature metallurgical processes including blast furnaces, a cold model study simulating a metal droplet descent through the surrounding fluid system is presented. The study comprises an experimental programme employing wide range of fluids exhibiting both Newtonian and non-Newtonian behaviour. Such fluid systems are encountered in slag–metal droplet systems where viscosity of the slag system has a significant effect on the kinetics of refining reactions. Slag systems generally possess random network structures comprising internal regions of weak ordering and the presence of these regions may result in non-Newtonian behaviour of the slag. As the viscosity of the slag is very sensitive to structure, a treatment of non-Newtonian behaviour as exhibited by some molten slag systems is therefore required. Two parameters have been identified and estimated that help to determine the rheological characteristics of fluids in relation to their network structure. The underlying principle of the model development has been that the external pressure exerts a driving force that affects the motion of the fluid to a degree dependent on the rheological behaviour and the network structure of the fluid. The paper also describes some results of a cold model study of the momentum transfer to the fluid system by correlating the drag Reynolds number with the modified drag coefficient for non-Newtonian fluids

(N*_Rem)^½?n′ = (N _Rem)^½?n′ (1/2C _Dm )^½     

Scrap melting in continuous process rotary melting furnace Part 1 – Bench scale furnace trials

Abstract

A heat transfer model was developed for scrap melting in an oxyfuel fired continuous process rotary melting furnace (CPRMF), which was envisioned as a replacement for the electric arc furnace in minimill steelmaking. The results are presented in a two part series. This first paper describes the bench scale CPRMF, the experimental procedure, and the operational results which will be used to validate the model. Two groups of copper melting trials were performed to explore aspects of furnace operation such as oxygen enrichment and slag thickness. The experimental results indicated that furnace thermal efficiency was significantly improved by moving from 37 to 80% oxygen in the combustion air and, extrapolating the results, would be ～30% for oxy fuel firing. With the constant oxygen level of 53%, the introduction of a slag layer significantly lowered the efficiency from 22 to 18% for 1·3 cm slag and 12% for 2·5 cm slag.     

Experimental research on effect of control model on lubrication for slab continuous casting mould

Abstract

In casting the control model relation between casting speed and frequency plays an important role in the optimisation of process parameters and the improvement of lubrication condition. The mould friction between mould and strand can directly describe the powder lubrication situation in a mould. In the present research, based on the slab continuous caster equipped with hydraulic oscillators, the transient friction forces were obtained by the differences between the monitored driving forces of casting and the calculated driving forces of no casting at same oscillation parameters. According to the trends of friction force with different control models, the characteristics and disadvantages of the traditional positive control model, and the improved positive control model and the inverse control model are discussed. This experimental study contributes to studying the frictional behaviour in mould under different control models, as well as selecting reasonable control model for high speed continuous casing.     

Cold model studies of mixing and mass transfer in steelmaking vessels

Abstract

Room temperature model studies using water to simulate 'metal' and paraffin oil (when required) as 'slag' were conducted to study the extent of mixing and the rate of mass transfer between metal and slag in the 130 t basic oxygen furnaces (BOFs) in operation in Tata Steel. Several systems of gas injection including top blowing, combined blowing and exclusive bottom purging were investigated. Similar work was undertaken in a room temperature model of an 80 t energy optimising furnace (EOF), in operation for a brief period earlier in Tata Steel. Details of the optimum blowing conditions, including the number/distribution of bottom tuyeres for the BOFs, are elaborated in the present paper. How mixing/mass transfer in an EOF compares with the BOF case(s) is also highlighted.     

Effect of alumina pickup on mould flux viscosity in continuous slab casting

Abstract

Mould flux samples were taken from a continuous slab caster mould at various stages during casting sequences. These confirmed that the amount of alumina pickup reaches a steady state level within the first 40 min of casting (in agreement with a simple model of alumina pickup). The steady state level was 3–4 mass-% higher than the original alumina content of the flux. Viscosity measurements carried out on two commercial mould fluxes, with different levels of alumina added, showed that the viscosity increase as a result of a 4 mass-%increase in alumina is not likely to affect mould behaviour. Comparison of the measured viscosities with predictions from literature models showed that no single literature model corresponds consistently to the measured values.     

Dissolution of alumina particles in CaO-Al2O3-SiO2-MgO slags

Abstract

The dissolution behaviour of alumina particles in CaO-Al₂O₃-SiO₂-MgO slags was studied by confocal scanning laser microscopy. Three different slag systems were investigated to evaluate the effect of changing the MgO content in a high silica tundish slag, and the effect of decreasing the silica content when dissolving the particles in a ladle slag. A particle of 80 mum diameter dissolved in 50 s in a simulated ladle slag but needed 100 s to dissolve in a high silica slag at the same temperature. When the silica content was decreased, a decrease in the alumina particle dissolution time was noted. During dissolution of alumina particles in a slag containing MgO, the alumina particle reacts with the slag to form an MgAlO₄ layer. No reaction layer was observed during the dissolution of alumina particles in slags that did not contain MgO. This work suggests that the dissolution time of large alumina particles is significant, increasing with particle size and with decreased temperature.     

Sonar Map Construction for Autonomous Mobile Robots Using a Data Association Filter

This paper presents a method for building a probability grid map for autonomous mobile robots with ultrasonic sensors using a data association filter (DAF). The method is based on evaluating the possibility that the acquired sonar data are all reflected by the same object. The DAF is able to associate data points with each other. Data affected by specular reflection are not likely to be associated with the same object, so they are excluded from the data cluster by the DAF, thereby improving the reliability of the data used for the probability grid map. Since the corrupted data are not used to update the probability map, it is possible to build a good quality grid map even in a specular environment. The DAF was applied to the Bayesian and the Orientation probability models, which are typical models used to build grid maps, to verify its effectiveness. Experimental results were also obtained using a mobile robot in a real-world environment.     

Hatfield Memorial Lecture 2007 Railways and materials: synergetic progress

Abstract

Railways were originally uniquely identified with the material of their initial construction and now are technically identified by the characteristic contact of 'steel wheel on steel rail'. Over 160 years ago failures of iron railway axles led to research into what we now know as metal fatigue. Accidents throughout the ages have acted as catalysts for research and improvements: this lecture will identify some key incidents. The change from iron to steel, following Bessemer's discovery of a method of bulk production and its implementation in Sheffield, resulted in fewer materials failures and enabled greater loads to be carried at greater speeds. Today's railways rely on a wide variety of materials from all the major classes of materials. The requirements of cost, weight, reliability, crashworthiness, maintainability and inspection are often in conflict as the service loadings imposed by the modern railway on materials have become more severe. It is not therefore surprising that despite our advances in knowledge and capabilities, costly failures still occasionally occur. Nevertheless, railways have benefited from, and contributed to, advances in material engineering way beyond the initial emphasis on iron.     

Evaluation of safety of French type B package designs in severe accident environments other than regulatory

Abstract

Packages used to transport radioactive materials in France must be designed to meet the safety performance requirements when subject to the test conditions set forth in the International Atomic Energy Agency (IAEA) Regulations. During actual use, the packages may be subject to quite different accident conditions. The Institut de Radioprotection et de Sûreté Nucléaire (IRSN) has evaluated the behaviour of typical packages designed to transport spent fuel, high activity waste, fresh mixed oxide (MOX) fuel and plutonium oxide powder under realistic conditions of mechanical impact and fire. The studied designs remain safe after impact onto targets present in the real environment of transport. The energy absorption by the package ancillary equipment (transport frame) compensates for the kinetic energy increase by comparison to the energy expended during the regulatory tests. New software was developed to correctly simulate the thermal behaviour of the neutron shielding materials. The studied package designs exhibit large margins of safety concerning resistance to fire. The results obtained have been used to develop tools in support of the appraisal of emergency situations.