Towards energy management during the machining of titanium alloys

The manufacturing industry needs to address challenges as regards to the machining process in the multifaceted context of sustainability. The current cost of energy and the reduction in material reserves highlights the need for machining systems to be more energy-efficient. This paper aims to provide a systematic overview of advanced approaches to manage energy and resource efficiency in cutting operations. The research experimentation focuses on the machining of a selected titanium alloy, Ti6Al4V, using carbide cutting tools. Tool wear, chip formation, cutting force and energy use were measured and analysed for selected cutting parameters. The experimental results illustrate the importance of selecting optimum cutting parameters and machining strategy. The results further help to define the boundary conditions for the various input parameters. Future research is also discussed

Investigating the effects of composite materials in solar cell encapsulation

In the past few decades our society’s increasing demands for energy have naturally resulted in increased utilization of renewable resources such as solar energy. Due to this strong demand the solar car endurance race was established to challenge researchers in this field. A competitive vehicle needs around six square meters of solar cells that produce approximately one kilowatt of power. This equates to 514 monocrystalline silicon half cells. The manufacturing challenge is to protect these cells from the terrestrial elements over a prolonged period of time. In this research study a composite encapsulation method was developed for solar cells and tested. Experiments were conducted to assess the processing of composite materials to improve the mechanical strength of the fragile solar cells. The effects of composites on reinforcement, electrical efficiency and thermal efficiency of the photovoltaic (PV) cells were evaluated. Impact testing to simulate a hailstone shows that the fibreglass sandwich panel structure will protect the surface of the cells, whilst reducing their efficiency by less than 5%

Residual stress depth profiling of commercially pure titanium subjected to high-speed machining using energy dispersive diffraction

Residual stress is well-known to influence the mechanical properties of machined components. The magnitude and distribution of these stresses are critical to determine the component’s life, specifically under fatigue loading. There exists a growing need to better understand the effects of cutting parameters on residual stress and to identify more innovative methods to evaluate residual stress. Titanium has been widely used, but many of the same qualities that enhance titanium’s appeal for most applications also contribute to it being one of the most difficult to machine materials. High-speed cutting experiments were conducted on commercially pure (CP) titanium and the residual stress depth profile was analysed using energy dispersive diffraction (EDDI). The residual stress depth profile of CP Grade 4 titanium was then evaluated. Experimental results show that cutting speed and depth of cut have a significant effect on the residual stress profile. At a low cutting speed, the surface residual stresses are largely compressive, becoming less compressive with an increase in cutting speed. An increase in depth of cut also introduces more compressive residual stresses into the material

A review of heat stress policies in the context of climate change and its impacts on outdoor workers: Evidence from Zimbabwe

Record-breaking summer heat events are increasing in frequency in Zimbabwe and 2016 was a particularly hot year with the country experiencing its worst heat wave event in decades. Currently, Zimbabwe has no coordinated public health response to deal with heat wave events and no specific data on heat-related morbidity and mortality. The country has no legislation for protecting workers against environmental heat exposure, particularly those most vulnerable who are employed in the informal sector. These workers are also at risk due to their outdoor work environments. The article outlines the state of climate and heat stresses in Zimbabwe, as benchmarked against other African countries and France. It further summarizes outdoor workers\u27 susceptibility to heat exposure and the need for the Zimbabwean Government to develop policies to ensure the health and safety of an increasing population of outdoor workers in Zimbabwe

Pan computed tomography for blunt polytrauma: Are we doing too many?

Background. Pan computed tomography (CT) is widely used in the evaluation of  patients with blunt polytrauma, but there is growing concern about the radiation risks imposed.Objectives. To ascertain whether we were possibly overutilising pan CT in our  trauma service, and whether we could safely cut down on scans without missing significant injuries.Methods. We audited all pan scans performed in the Metropolitan Trauma Service, Pietermaritzburg, South Africa, during the 12-month period 1 January - 31  December 2012. An analysis was done to determine what injuries were identified and how these findings influenced our management.Results. Of the 140 pan scans, 108 (77.1%) influenced management. These  included the following components: 62 brain scans (44.3%), 16 cervical spine scans (11.4%), 50 chest scans (35.7%) and 31 abdominal scans (22.1%). The remaining 32 pan scans (22.9%) did not influence management. However, it turned out that many of these ‘clinically negative’ scans were in fact clinically important, ruling out injury in patients in whom clinical assessment was regarded as unreliable: 3 patients (2.1%) were hypoxic and had to be sedated, intubated and ventilated; 14 (10.0%) had a Glasgow Coma Score (GCS) of <15; and 9 (6.4%) had major  distracting injuries. This left only 6 pan scans (4.3%) that were not regarded as clinically helpful.Conclusion. In our setting, the majority of pan scans influence management. By  ruling out significant injuries, clinically negative scans are valuable in patients who are obtunded, intubated and ventilated, or have major distracting injuries. In  patients with a GCS of 15, not sedated and ventilated and with no major distracting injuries, clinical assessment and alternative imaging modalities may suffice

Manufacturing challenges for custom made solar vehicles in South Africa

Solar challenges are designed to test the reliability and efficiency of solar powered vehicles in endurance races. In the past these manufactured vehicles were technology drivers and led to advances in electric motors and solar cell efficiency. The speed in relation to power consumption is one of the main design considerations, with the only energy source being solar power. In the design and manufacturing of these vehicles a number of requirements need to be met in order to pass the safety standards. The Sasol Solar Challenge (SSC) created an opportunity for South African universities to design and manufacture custom made solar powered vehicles. This paper explores and discusses the challenges for manufacturing solar vehicles in South Africa. Key elements like the communication gap between design and manufacturing, the cost of lightweight solar encapsulation, the shortage of local suppliers and expertise in composite manufacturing are evaluated. These insights can be used as foundation for strategic decisions by future stakeholders

Visual symptom identification of grapevine leafroll-associated virus 3 in red berry cultivars supports virus management by roguing

Grapevine leafroll-associated virus 3 (GLRaV-3) is the most serious virus in New Zealand and South African vineyards. Its negative influence on berry development is reflected on wine quality, thus making GLRaV-3 control a priority. In red berry cultivars, changes in leaf colour could be useful for the visual identification of GLRaV-3-infected vines with a view to roguing (removing) such vines. We tested the efficacy of visual diagnosis as a potentially cost-effective alternative option to the enzyme-linked immunosorbent assay (ELISA) that is usually used for this purpose. All the vines, or a subsection of vines, in multiple vineyards in New Zealand or South Africa where annual roguing was being performed, were evaluated with the two methods. Of the 114,782 vines assessed visually for symptoms and tested by ELISA, the two methods were in agreement for 114,701 (99.9%) vines, with only 81 vines showing differing results. In 11 of the 44 annual vineyard analyses, visual detection of symptoms was perfectly correlated with ELISA results (sensitivity 100%). The specificity of visual symptom identification compared with ELISA was higher than 99.7% in 43 of the 44 annual vineyard analyses. Symptoms as a predictor of negative ELISA proved to be above 97.5% in all 44 annual vineyard analyses but as a positive predictor, was 100% in 10 of 19 annual vineyard analyses where this could be determined. We conclude that for the red-berried cultivars in this study, visual assessment of foliar symptoms should be adopted as a costeffective alternative to ELISA during implementation of roguing for GLRaV-3 control.This work formed part of the New Zealand Grape and Wine Research programme.New Zealand Winegrowers, the New Zealand Institute for Plant & Food Research Strategic Science Investment Fund and also Winetech and Vergelegen Wine Estate (South Africa).http://www.sipav.org/main/jpp/index.php/jpp2018-06-30am2017Forestry and Agricultural Biotechnology Institute (FABI)Microbiology and Plant Patholog

Risk perceptions of dust and its impacts among communities living in a mining area of the Witwatersrand, South Africa

Mining is a major economic activity in many developing countries. In South Africa, gold mining has played a significant role in the development and sustenance of the country's economy, with both positive and negative consequences. In gold mining areas, tailings dams and mine dumps are significant sources of ambient dust, known to be a nuisance, and health risk, to communities living near them and who must find appropriate coping mechanisms to protect themselves. A qualitative study based on five focus groups with sixty-two participants of different ages and sex was carried out in the Witwatersrand mining district of South Africa. All focus groups agreed that they had noticed dust in the air where they live, stating that the dust came largely from mine dumps but also from other sources. They agreed that the dust causes, among others, health problems, and both short-term and long-term coping mechanisms for protecting themselves against excess dust were mentioned yet considered inadequate, i.e. closing windows and doors, watering their yards, paving their yards and planting trees. Little support from government, mines and other organisations was identified as an important perceived barrier to resolving the dust problem. Means for communication of communities' perceptions of the impacts, risks and possible mitigation / adaption measures associated with dust need to be created and supported in a formal risk management plan

Habitat-based density models of pack-ice seal distribution in the southern Weddell Sea, Antarctica

Climate variability and changes in sea ice dynamics have caused several ice-obligate or krill-dependent populations of marine predators to decline, eliciting concern about their demographic persistence and the indirect ecological consequences that predator depletions may have on marine ecosystems. Pack-ice seals are dominant ice-obligate predators in the Antarctic marine ecosystem, but there is considerable uncertainty about their abundance and population trends. We modelled the density and distribution of pack-ice seals as a function of environmental covariates in the southern Weddell Sea, Antarctica. Our density surface modelling approach used data from aerial surveys of pack-ice seals collected in the 2013/14 austral summer. Crabeater seals Lobo don carcinophaga, the most numerous pack-ice seal we observed, occurred at the highest densities in areas with extensive sea ice near the continental shelf break, but were almost absent in areas of similar sea ice concentration in the southern extent of the Weddell Sea. The highest densities of Weddell seals Leptonychotes weddelli, which were less abundant than crabeater seals within the pack-ice habitat, were predicted to occur over the continental shelf, near the shelf break. The distribution of both seal species broadly corresponded with the distribution and relative abundance of their main prey (Antarctic krill Euphausia superba and Antarctic silverfish Pleuragramma antarctica) obtained from concurrent ecosystem surveys. Ross seals Ommatophoca rossii and leopard seals Hydrurga leptonyx were not detected at all and are apparently rare within the southern Weddell Sea. These results can contribute to biodiversity assessments in the context of marine protected area planning in this region of the Southern Ocean