Brian Boswell

Effect of machining parameters on the surface finish of a metal matrix composite under dry cutting conditions

The machining of aerospace materials, such as metal matrix composites, introduces an additional challenge compared with traditional machining operations because of the presence of a reinforcement phase (e.g. ceramic particles or whiskers). This reinforcement phase decreases the thermal conductivity of the workpiece, thus, increasing the tool interface temperature and, consequently, reducing the tool life. Determining the optimum machining parameters is vital to maximising tool life and producing parts with the desired quality. By measuring the surface finish, the authors investigated the influence that the three major cutting parameters (cutting speed (50–150 m/min), feed rate (0.10–0.30 mm/rev) and depth of cut (1.0–2.0 mm)) have on tool life. End milling of a boron carbide particle-reinforced aluminium alloy was conducted under dry cutting conditions. The main result showed that contrary to the expectations for traditional machined alloys, the surface finish of the metal matrix composite examined in this work generally improved with increasing feed rate. The resulting surface roughness (arithmetic average) varied between 1.15 and 5.64 μm, with the minimum surface roughness achieved with the machining conditions of a cutting speed of 100 m/min, feed rate of 0.30 mm/rev and depth of cut of 1.0 mm. Another important result was the presence of surface microcracks in all specimens examined by electron microscopy irrespective of the machining condition or surface roughness.

Accuracy and finish during wire electric discharge machining of metal matrix composites for different reinforcement size and machining conditions

Electric discharge machining has been established as an effective alternative process to conventional material removal processes for machining reinforced metal matrix composites. Wire cut electric discharge machining holes were produced in a metal matrix composite (10 vol% of SiC in Al6061), which were then investigated to determine the machinability of the material using this process. It was observed that the input factors such as the size of reinforced particles, wire tension and pulse-on time significantly affect diameter error, circularity and surface roughness. Pulse-on time, the interaction between pulse-on time and wire tension contribute to the maximum diameter error. The wire tension is the most significant factor to circularity, which is followed by the interaction between pulse-on time. In particular, wire tension with low and high tensions results in poor circularity. It has been found that there are more surface defects encountered when particle sizes are smaller, and circularity is improved when particles are in a medium size. In addition, the surface defect is reduced as the particles increase the melting resistance of the surface. The higher pulse-on time leads to higher heat and more time to degrade the surface. Therefore, low pulse-on time and wire tension gave better surface finish.

Estimation of Internal Pit Depth Growth and Reliability of Aged Oil and Gas Pipelines— A Monte Carlo Simulation Approach

To estimate the internal pit depth growth and reliability of aged oil and gas pipelines, a Monte Carlo simulation approach was adopted. The average maximum pit depths of corroded pipelines were correlated with the operating parameters—temperature, CO2 partial pressure, pH, flow rate, sulfate ion concentration, chloride ion concentration, water cut, and wall shear stress via a multivariate regression analysis. Poisson square wave model was used to predict the time lapse of the pit depth growth using the statistical best fit of the maximum pit depth and operating parameters as boundary conditions. Weibull probability function was used to determine the failure intensity and survivability of the pipelines for different distribution types, whereas inspection data from a magnetic flux leakage in-line inspected transmission pipeline were used to test the application of the model. The future pit depth distribution, survivability, and failure rate of this transmission pipeline were also determined, with the result...

Sustainable cooling method for machining titanium alloy

Hard to machine materials such as Titanium Alloy TI-6AI-4V Grade 5 are notoriously known to generate high temperatures and adverse reactions between the workpiece and the tool tip materials. These conditions all contribute to an increase in the wear mechanisms, reducing tool life. Titanium Alloy, for example always requires coolant to be used during machining. However, traditional flood cooling needs to be replaced due to environmental issues, and an alternative cooling method found that has minimum impact on the environment. For true sustainable cooling of the tool it is necessary to account for all energy used in the cooling process, including the energy involved in producing the coolant. Previous research has established that efficient cooling of the tool interface improves the tool life and cutting action. The objective of this research is to determine the most appropriate sustainable cooling method that can also reduce the rate of wear at the tool interface.

Effect of cooling methods on hole quality in drilling of aluminium 6061-6T

The influence of cooling method and drilling parameters on hole production has been investigated experimentally and analytically by measuring the hole quality. A three-level, three-parameter experiment was conducted using design-of-experiment methodology. The three levels of independent input parameters were: for cooling method—flood drilling, minimum quantity lubrication (MQL) drilling and cryogenic drilling; for feed rate—0.2, 0.3 and 0.4 mm/rev; and for cutting speed—60, 75 and 100 m/min. The selected work and tool materials were aluminium 6061-6T and high speed steel (HSS), respectively. The measured output parameters were the three most widely used quality characteristics of drilled holes - diameter error, circularity and surface roughness. The results were analysed applying three methods: Pareto ANOVA, Taguchi method and traditional analysis. The findings revealed that the cooling method has a significant effect on diameter error (contribution ratio 88.27%), moderate effect on surface roughness (contribution ratio 41.74%) and relatively small effect on circularity (contribution ratio 23.64%). The best results for the dimensional accuracy and surface roughness were achieved by MQL drilling. Cryogenic drilling produced the best circularity results; however, in terms of dimensional accuracy and surface roughness it was the worst.

The Challenge of Adopting Minimal Quantities of Lubrication for End Milling Aluminium

End milling is a very common metal cutting process used for the machining of most types of metal. The process is inherently intermittent causing the tool tip edge to constantly fluctuate between various levels of temperatures, specifically from cold to \(300\,\,^\circ \mathrm{C}\) when cutting Al alloy. During dry end milling cutting temperatures need to remain within the design specifications of the tool tip. Even working with Al alloy the tool tip is subjected to thermal cyclic stresses. Conventional wisdom states that it is essential to use flood cooling during end milling, as intermittent cooling increases the effect of thermal shock and build up edge. Al alloy—unlike other materials—needs cutting fluid to avoid smearing the insert edges and to improve the surface finish. Modern machining companies constantly face the challenges of environmental issues that affect the manufacturing costs of machined parts. New environmental manufacturing techniques need to be developed for companies to remain competitive in the future. The research presented in this paper represents the experimentation involved in determining a suitable environmental alternative to using copious amounts of cutting fluid during end milling of Al alloy. Previous experimental evaluation of Minimal Quantities of Lubrication (MQL) when applied to the machining of Al alloy has proved to be inconclusive.

Modelling the effects of production rates and physico-chemical parameters on pitting rate and pit depth growth of onshore oil and gas pipelines

To estimate the pitting rate of internally corroded oil and gas gathering pipelines, a multivariate regression modelling was carried out, using pitting rates and operating parameters. These operating parameters, temperature, pH, CO2 partial pressure, water cut, wall shear stress, chloride ion concentration, sulphate ion concentration, operating pressure, oil production rate, gas production rate and water production rate, were obtained from routine monitoring of the pipelines, whereas, the pitting rates (mean pit depths over time) were determined by the ultrasonic thickness measurement technique. The operating parameters and pitting rates were also used to estimate the pit depth growth of the pipelines using Monte Carlo simulation, and field data were used to test the developed models. The results obtained indicated that the pipelines under severe pitting corrosion rate were, more conservatively predicted than those under low, moderate and high pitting corrosion rates.

Predicting the Influence of the Machining Parameters on the Tool Tip Temperature

This research has indicated that, by using a computer model, a numerical method can be effective in predicting the tool tip temperature. This allows the effects of changes made to the machining parameters to be simulated. Temperatures through the tool tip can therefore be reduced by using the optimum cooling method for particular machining parameters.

Techno-Economic and Environmental Implications of Electricity Generation from Solar Updraft Chimney Power Plant in Meekatharra in Western Australia

A decentralised diesel power plant (DDPP) provides the electricity needs to Meekatharra, a remote Western Australia community. It consumes 476,000 l of diesel per annum, resulting in environmental and economic challenges which are due to the long transportation distances. A solar chimney power plant (SCPP) has been suggested to complement the diesel power plant, thereby reducing the reliance on diesel fuel to meet the electricity demand. An SCPP is a system that utilises a combination of hot air and a central updraft chimney to generate a convective flow to drive turbines to generate electricity. The solar radiation potential in Meekatharra is high (24 MJ/m2), which allows solar energy technology to be employed for power generation. The technical design for Meekatharra SCPP has been based on the performance of Curtin’s small solar chimney. A life cycle assessment has been applied to assess the economic and environmental implications of supplementing the DDPP with the SCPP. Finally, this paper endeavours to detail the long-term sustainability benefits for Meekatharra resulting from the implementation of an SCPP.

Reliability Analysis and Performance Predictions of Aged Pipelines Subjected to Internal Corrosion: A Markov Modelling Technique

To maintain the integrity of corroded oil and gas pipelines, the reliability at times of exposure over the lifecycle duration need to be understood. This paper describes the procedures for predicting the performance of internally corroded oil and gas pipelines using a probabilistic-based Markovian process. The Pipeline Corrosivity Index (PCI), which is expressed as a function of the retained pipe-wall thickness was used to describe the condition of the corroded pipelines at exposure durations for low, moderate, high and severe corrosion rates. The time variation of the predicted Pipeline Corrosivity Index (PCI) was compared with field measured Pipeline Corrosivity Indexes (PCIs) of corroded API X52 grade pipelines and the results indicate that the model developed in this research is viable for integrated management of aged corroded pipelines and remaining useful life predictions.Copyright