Coal strength measurement by stereo digital image correlation

Correct estimation of coal mechanical properties, including Young\u27s modulus and Poisson\u27s ratio, play a crucial role in on-site coal mining design and numerical simulations of coal behaviour. Traditionally, these parameters are determined through laboratory testing of cylindrical samples using strain gauges. However, such methods have limitations due to the potential errors from strain gauge misplacement, localised measurements at the gauge placement area, and difficulty in preparing a standard-size sample from coal. To overcome these challenges, this paper assesses the applicability of the Digital Image Correlation (DIC) technique on Brazilian-sized disc-shape coal specimens. Several benchmark tests were first conducted under uniaxial compression conditions at varying loading rates to verify the technique with known materials. While more verification tests need to be conducted to account for coal intrinsic heterogeneity, the conducted trials provide promising results and demonstrate that 3D DIC of Brazilian coal samples is a simpler yet effective method for determining coal Young\u27s modulus and Poisson\u27s ratio

Brittle-ductile transition in coal pillar failures

Factor of Safety (FoS) is the most widely used empirical criterion in coal pillar design. The increased vertical stresses associated with deep mining are resulting in pillar sizes much larger than those used in the development of the empirical strength formula. It is not uncommon to see pillars with over 50 m solid widths based on the established design criteria, which reduces overall reserve recovery and development productivity. Previous research revealed that pillars will transform from brittle to ductile failure with strain-hardening behaviour when their w/h ratio exceeds a certain critical value. However, the actual failure mechanics of pillars with different w/h ratios have largely been understudied. This paper discusses whether a coal pillar with a critical w/h ratio and reduced FoS can achieve functionality to allow more flexibility in pillar design for mine layout optimization. Using the more advanced laboratory testing and monitoring equipment that is now available, the failure mechanics of coal samples with different dimensions are investigated through uniaxial compression tests. The w/h value at which in situ pillar behaviour would be expected to transform from brittle to ductile is then considered and discussed further, including the research program that would enable the findings to be safely applied in deep underground mines

The complex spaces of co-production, volunteering, ageing and care

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record The care of older people is being radically reformulated by placing the individual at the centre of care process through the introduction of individual care plans. This marks a significant transition for the care of older people away from acute responsive clinical care towards a greater emphasis on co-produced preventative health and social care and relations of care “with” older people. Geographies of volunteerism are yet to consider the effect of co-production as a dominant rhetoric in UK health and social care. In this paper we show that the Health and Social Care Act (2012) and the Care Act (2014) has the potential to fundamentally alter discourses of care by introducing new spatialities to older people's care. New spatialities of care will not only rely on the reciprocity and interdependence of care between individuals and organisations but also the mobilisation of a voluntary care-force to be attentive to individuals. Spatialising co-production reveals the institutional and professional boundaries that prevent the type of open partnership that sits at the heart of the rhetoric. Our ethnographic and qualitative methodology was developed to understand how our case study of Living Well (Cornwall, UK), as a philosophy of care, is realised in practice and to consider the main collaborators’ views of different methods of co-production involving volunteers. We discuss two principal spaces of co-production, highlighting the opportunities provided for, and barriers to, co-production expressed by volunteers and other partners by attending to the relations of care that are recognised through: (1) formal meetings and coffee mornings, which provide spaces for volunteers to contribute, and (2) multi-disciplinary team (MDT) meetings, in which volunteers are largely absent.National Endowment for Science, Technology & the Arts (NESTA

Ab initio investigations of the interfacial bond of Fe(001)/Al(001)

Density functional theory-based ab initio simulations were performed to investigate the bond strength of an Fe (001)/Al(001) coherent interface, its atomic configuration, oxidation at the interface, and mechanical deformation along the lateral direction of the interface. The bcc-type interface exhibited the highest bond strength in terms of the work of separation, but the bond strength decreased significantly when oxygen was introduced. The fracture of the bare interface initiated at the Al matrix under tensile loading, whereas that of the oxidized interface began at the interface because oxygen deteriorated the high bond strength between the Fe and Al atoms. Additionally, the bond strength of the interface was investigated under different biaxial strains to understand the effect of the residual stress generated during the joining process of Fe(001)/Al(001). Based on our findings, the mechanical deformation along the lateral direction does not significantly impact the bond strength

The borides and silicides of the platinum metals and rhenium

Imperial Users onl

The Metallurgy of Commercially Pure Titanium Alloys Welded with a Pulsed Laser Beam

This thesis examines the effect of welding on the microstructure and properties of commercially pure titanium welded with a pulsed laser beam. Among other applications, pulsed laser welding is widely used in the construction of dental implants from pre-fabricated wrought components and also for the repair of both wrought and cast implants. In practice these devices experience an increased number of failures due to fracture of the laser welded titanium framework compared to traditional gold prostheses. The numerous studies which have focused on improving the properties of such welds, however, tend to be more clinically focused with only limited investigations into understanding the fundamental weld metallurgy. In the present work this issue is addressed with detailed investigation into the effect of alloying elements, external contamination from welding and changing process parameters. In addition, micros tensile testing and wave-dispersive spectroscopy techniques are developed to try and improve the characterisation of pulsed laser welds. Modern wave dispersive spectroscopy techniques were successfully employed to measure bulk oxygen content in titanium on a small area 100x100m with good agreement with the bulk ASTM standard technique down to oxygen contents of 500ppm. The technique was still not localised enough however to be applied to the intended application of laser welds. An all-weld longitudinal micro tensile test was successfully developed with the ability to accurately evaluate the elongation of the welds. It was identified however that the significance of such tensile test results could not be appreciated without further investigation into the weld metallurgy to develop a greater understanding of the cause of the measured changes in properties. Investigations into the weld metallurgy revealed that alloy composition and external contamination have the most significant effect on the weld microstructure and hardness of the weld with the effect of process parameters being more subtle. The welds consist of a fusion zone and a HAZ region which has undergone significant grain growth and morphology change due to heating above the beta transus. At low alloy contents the fusion zone and HAZ undergo a massive transformation on cooling which transits to a martensite transformation with increased alloy content. Iron was found to have the largest effect on weld microstructure, being a strong suppressor of the massive phase and promoting the martensitic transformation. Oxygen and nitrogen do not affect the nature of the allotropic beta to alpha phase transformation as much as iron but have a more pronounced effect on hardness due to solid solution strengthening. The transition from massive to martensitic transformation occurs at lower alloy contents in the fusion zone compared to the HAZ due to the higher cooling rate it experiences. A wide range of process parameters were trialled with little affect on the nature of the allotropic phase transformation. The main effect of process parameters was to coarsen the microstructure due to changes in the cooling rate linked mainly to changing energy per pulse. The hardness of high solute content alloys was more sensitive to changes in process parameters than low solute content alloys due to the effect solutes have on increasing the gradient of the Hall-Petch relation. For higher pulse energy welds an additional HAZ was identified associated with slow early stage recrystallization in the alpha phase field. This region requires a large number of dislocation to form however so is only present for welds on deformed substrates

A Continuing Roof and Floor Monitoring Systems for Tailgate Roadways

Moranbah North Mine has employed the use of Remote Reading Tell Tale Systems (RRTT Systems) since 2012 for the purposes of ensuring accurate, continuous and real time roof movement monitoring for critical infrastructure roadways. Recently an integrated monitoring system was installed in the tailgate roadway of LW112 to monitor and record the continuous ground movement outbye of the retreating longwall face to better understand both the roof and floor movement. Vertical convergence of the tailgate roadway during longwall retreat is typically managed by installing both active support elements and standing support at Moranbah North Mine. The data has provided significant insights into the magnitude of both roof and floor movement outbye of the longwall which has enhanced the understanding of the required densities of standing support at various locations throughout the tailgate. The system has also demonstrated its potential to be used as a management tool, e.g. during extended face stoppages. Once installed, the monitoring system is entirely automated and the data is automatically collected and transferred to the surface via an optical fibre cable. The system and real-time communication are flexible and can be tailored to meet site specific monitoring needs. The system includes: an RRTT System, real time convergence monitoring probes and a real time data acquisition, communication and reporting system. The system enables Moranbah North to be able to measure total vertical roadway convergence and roof displacement continuously without having to access the tailgate at regular intervals. The combined data can be used to investigate: required standing support capacity and density; tailgate roadways ‘zones’ of increased vertical loading associated with intersections; the influence of strata and structural variation; and the optimum support strategy for ensuring roadway stability outbye of the longwall face. The analysis and results produced indicate that standing support densities appear to exceed the required support loads and with continued monitoring providing more data, it may prove possible to optimise support spacings