Douglas Hargreaves

Analysis of water-lubricated journal bearings with multiple axial grooves

Abstract The steady state and dynamic characteristics including whirl instability of water-lubricated journal bearings having three axial grooves are obtained theoretically. The Reynolds equation is solved numerically by the finite difference method satisfying the appropriate boundary conditions. The dynamic behaviour in terms of stiffness and damping coefficients of film and stability are found using a first-order perturbation method. It has been shown that both load capacity and stability improve when smaller groove angles are used.

Surface waviness effects on the load-carrying capacity of rectangular slider bearings

Abstract An experimental and theoretical study has been performed to investigate the influence of surface waviness on the stationary surface of rectangular slider bearings, in particular the effect on the load-carrying capacity. It is shown that surface waviness can enhance the load-carrying capacity, the degree of enhancement being dependent on the particular type of surface waviness as well as the degree of bearing tilt. Over 500 experimental pressures obtained from a modified plint tilting pad test rig were compared with theoretical predictions. The deviation between theory and experiment varied with operating conditions, the mean discrepancy being about 7%.

Does pedagogy still rule

Abstrack Theories on teaching and learning for adult learners are constantly being reviewed and discussed in the higher educational environment. Theories are not static and appear to be in a constant developmental process. This paper discusses three of these theories: pedagogy, andragogy and heutagogy. It is argued that although educators engage in many of the principles of either student-centered (andragogy) and self-determined (heutagogy) learning, it is not possible to fully implement either theory. The two main limitations are the requirements of both internal and external stakeholders, such as accrediting bodies and requirements to assess all student learning. A reversion to teacher-centered learning (pedagogy) ensues. In summary, we engage in many action-oriented learning activities but revert to teacher-centered approaches in terms of content and assessment.

Review of test methods for abrasive wear in ore grinding

Abstract Maintenance costs associated with wear in coal grinding mills operating in Queensland pulverised coal-fired power stations are in excess of

Performance of environment-friendly hydraulic fluids and material wear in cavitating conditions

10m per year. In other fuel-ore and mineral-ore processing industries metal wastage through wear and corrosion is also a major component of maintenance cost. The aim of this paper is (1) to define the relevant terminology applicable to abrasive wear and wet-grinding, and (2) to review the more commonly used test methods for examining wear associated with ore grinding. The test methods considered simulate open three-body abrasive wear and were compared in terms of their tribo-mechanical characteristics, general wear theory concepts such as wear coefficient and wear susceptibility, and the correlation of wear rate with pilot-scale and full-scale mill wear rates. The paper also reviews the application of statistical distributions as a means of interpreting wear rate data from laboratory test mills and production mills. A need for improved correlation between laboratory test results and production mill wear rates based on a more fundamental understanding of the wear processes involved was identified. This review outlines a basis for detailed work leading to this end.

Water lubricated bearings

The cavitation performance of various metals and hydraulic fluids used in a hydraulic system was evaluated using the vibratory test method. Mineral oil, vegetable oil and oil-in-water emulsions were used in the experiments. The materials were selected based on the general components employed in a hydraulic system—AA 5005 aluminium alloy, ASTM A536-84 ductile spheroidal graphite (SG) cast iron, ASTM A48-83 grey cast iron, AISI 303 stainless steel and BS 1400 LG2 bronze. It was observed that vegetable oil exhibits the best medium for erosion resistance for all metals due to its high viscosity index. Emulsions having higher oil concentration produced lesser erosion damage. It was seen that an increase in viscosity led to a decrease in the rate of growth and collapse of bubbles and hence reduced erosion on the surfaces of the specimens. The experiments also revealed that materials with high hardness had less cavitation damage for all lubricants. A comparison of cavitation performance revealed that materials and hydraulic fluids have a dependent relationship. Results indicate that AISI 303 stainless steel would be the best choice in the construction of a hydraulic system and this is especially the case when using a hydraulic fluid that has a high viscosity index.

A new model for combined Couette and Poiseuille flows in the transverse groove of a plane inclined slider bearing

The increasing ecological awareness and stringent requirements for environmental protection have led to the development of water lubricated bearings in many applications where oil was used as the lubricant. The chapter details the theoretical analysis to determine both the static and dynamic characteristics, including the stability (using both the linearised perturbation method and the nonlinear transient analysis) of multiple axial groove water lubricated bearings. Experimental measurements and computational fluid dynamics (CFD) simulations by the Tribology research group at Queensland University of Technology, Australia and Manipal Institute of Technology, India, have highlighted a significant gap in the understanding of the flow phenomena and pressure conditions within the lubricating fluid.

Numerical Investigation of Hammer Erosive Wear due to Particle Impact

Abstract Although extensive research has been performed on the grooving of hydrodynamic bearings, there is much to be done on the flow interactions near to and in axial grooving. This work was initiated when the pressure boundary conditions were unknown for the case of a journal bearing with multiple axial grooves each being fed by an external lubricant source. This work is a forerunner to a more extensive research programme using journal bearings. A new technique has been devised to calculate the pressure profile across and along an axial groove. There is a strong pressure flow along the groove and Couette and pressure flow in the direction of sliding. Good correlation between experimental results and theoretical predictions for a wide range of operating conditions has been achieved.

A Basis for Inquiry into Policy Considerations for Increasing the Application of Biophilic Urbanism

Hammers are the key machine element of high-speed hammer mills which lead to the coal pulverisation process. Progressive material loss from the hammer occurs due to the mechanical interactions between the coal particles and the hammer surface. Coal pulveriser industries implement extensive efforts to combat against premature material loss from the hammer surface due to coal particle impact which may result in premature failure. This work investigates the erosion wear mechanism through computational simulation. A numerical model is developed using Abaqus® to simulate the solid coal particle impacting onto the hammer (target).The Abaqus/Explicit® dynamic simulation solver is used for this analysis. The interactions between the solid coal particles and the target are modelled using the Abaqus/Explicit® element deletion method. The Johnson and Cook plasticity model is employed to analyse the flow stress behaviour of ductile materials during impact. The developed stress and plastic strain are analysed through simulation on the impact surface. This model is applied to different ductile alloys to determine the best erosion wear resistance hammer material for extending the operating life of hammers in the coal pulverisation process.

Development of a postgraduate engineering management program for the Asia-Pacific region

Urban design that harnesses natural features (such as green roofs and green walls) to improve design outcomes is gaining significant interest, particularly as there is growing evidence of links between human health and wellbeing, and contact with nature. The use of such natural features can provide many significant benefits, such as reduced urban heat island effects, reduced peak energy demand for building cooling, enhanced stormwater attenuation and management, and reduced air pollution and greenhouse gas emissions. The principle of harnessing natural features as functional design elements, particularly in buildings, is becoming known as ‘biophilic urbanism’. Given the potential for global application and benefits for cities from biophilic urbanism, and the growing number of successful examples of this, it is timely to develop enabling policies that help overcome current barriers to implementation. This paper describes a basis for inquiry into policy considerations related to increasing the application of biophilic urbanism that captures and integrates knowledge from lived experience around the world. The paper draws on research undertaken as part of the Sustainable Built Environment National Research Centre (SBEnrc) in Australia. The paper discusses the emergence of a qualitative, mixed-method approach that captures lived experiences and extends beyond the literature and documented journeys of international cities that have encouraged biophilic urbanism. Stakeholder workshops provide context and scope to research to ensure it is targeted, and a meta-narrative is developed to extract key learnings of relevance.