Modelling the influence of the process inputs on the removal of surface contaminants from Ti-6Al-4V linear friction welds

The linear friction welding (LFW) process is finding increasing interest from industry for the fabrication of near-net-shape, titanium alloy Ti–6Al–4V, aerospace components. Currently, the removal of surface contaminants, such as oxides and foreign particles, from the weld interface into the flash is not fully understood. To address this problem, two-dimensional (2D) computational models were developed using the finite element analysis (FEA) software DEFORM and validated with experiments. The key findings showed that the welds made with higher applied forces required less burn-off to completely remove the surface contaminants from the interface into the flash; the interface temperature increased as the applied force was decreased or the rubbing velocity increased; and the boundary temperature between the rapid flash formation and negligible material flow was approximately 970 °C. An understanding of these phenomena is of particular interest for the industrialisation of near-net-shape titanium alloy aerospace components.EPSRC, Boeing Company, Welding Institut

Improved Hydrogeophysical Parameter Estimation from Empirical Mode Decomposition Processed Ground Penetrating Radar Data

Various techniques have been designed to maximize the use of ground penetrating radar (GPR) as an exploration tool. Improvements in signal processing are expected to further facilitate the accuracy of parameters derived from using GPR in certain geologic environments. Common-offset GPR data were collected at the Marine Corps Air Station (MCAS) in Beaufort, South Carolina, and dielectric constants were calculated following the application of the empirical mode decomposition (EMD) for dewowing GPR traces. Conventional signal processing is applied to the GPR traces to provide hydrogeophysical parameter estimates such as volumetric water content, porosity, and hydraulic conductivity. The results are validated using a coincident vertical radar profile, existing hydraulic data from direct measurements, and comparing EMD derived parameters with those non-EMD derived. The results of the comparison between the EMD and non-EMD methods show improved hydrogeophysical estimations from the EMD processed data. Dielectric constant (k) values from the non-EMD method are outside the range of the values for all geologic materials (k#40). The subsequent parameter estimates using dielectric constants derived from non-EMD processed data yield erroneous results therefore justifying the use of EMD as a method in dewowing GPR data for quantitative analyses

Empirical Mode Decomposition Operator for Dewowing GPR Data

Signal processing tools available to ground penetrating radar data used for shallow subsurface imaging and hydrogeophysical parameter estimation are significantly handled using the same tools available to seismic reflection data. Overall, the same tools produce interpretable images from both data types, but particular noise (wow noise) in electromagnetic data must be removed before stable and accurate quantitative results can be produced. Wow noise is an inherent, nonlinear electromagnetic interference and a significant component of GPR data. Further, the nonlinear and non-stationary nature of wow noise provides a strong argument for preprocessing radar traces with time-domain operators. Time-domain operators designed for nonlinear signals are under increasing development for both electromagnetic and acoustic signal processing. This work demonstrates optimal wow noise removal from ground penetrating radar data using the empirical mode decomposition. The technique provides a data-driven approach to empirically dewowing GPR data

Wire + Arc Additive Manufacturing

Depositing large components (>10 kg) in titanium, aluminium, steel and other metals is possible using Wire + Arc Additive Manufacturing. This technology adopts arc welding tools and wire as feedstock for additive manufacturing purposes. High deposition rates, low material and equipment costs, and good structural integrity make Wire+Arc Additive Manufacturing a suitable candidate for replacing the current method of manufacturing from solid billets or large forgings, especially with regards to low and medium complexity parts. A variety of components have been successfully manufactured with this process, including Ti–6Al–4V spars and landing gear assemblies, aluminium wing ribs, steel wind tunnel models and cones. Strategies on how to manage residual stress, improve mechanical properties and eliminate defects such as porosity are suggested. Finally, the benefits of non-destructive testing, online monitoring and in situ machining are discussed

Structural and Stratigraphic Control on the Migration of a Contaminant Plume at the P Reactor Area, Savannah River Site, South Carolina

Geophysical methods, including a shallow seismic reflection (SSR) survey, surface and borehole ground-penetrating radar (GPR) data, and electrical resistivity imaging (ERI), were conducted at the Savannah River site (SRS), South Carolina, to investigate the shallow stratigraphy, hydrogeophysical zonation, and the applicability and performance of these geophysical techniques for hydrogeological characterization in contaminant areas. The study site is the P Reactor area located within the upper Atlantic coastal plain, with clastic sediments ranging from Late Cretaceous to Miocene in age. The target of this research was the delineation and prediction of migration pathways of a trichloroethylene (TCE) contaminant plume that originates from the northwest section of the reactor facility and discharges into the nearby Steel Creek. This contaminant plume has been migrating in an east-to-west direction and narrowing away from the source in an area where the general stratigraphy along with the groundwater flow dips to the southeast. Here, we present the results from a stratigraphic and hydrogeophysical characterization of the site using the SSR, GPR, and ERI methods. Although detailed stratigraphic layers were identified in the upper approximately 50 m (164 ft), other major findings include (1) the discovery of a shallow (∼23 m [75 ft] from the ground surface) inverse fault, (2) the detection of a paleochannel system that was previously reported but that seems to be controlled by the reactivation of the interpreted fault, and (3) the finding that the hydraulic gradient seems to have a convergence of groundwater flow near the area. The interpreted fault at the study site appears to be of upper Eocene age and may be associated with other known reactivated faults within the Dunbarton Triassic Basin. The coincident use of the SSR and ERI methods in conjunction with the complementary 50-, 100-, and 200-MHz GPR antennas allowed us to generate a detailed geologic model of the shallow subsurface, suggesting that the migration of the TCE plume is constrained by (1) the paleochannel system with respect to its migration direction, (2) the presence of an inverse fault that may also contribute to the paleochannel growth and structural evolution, and (3) the local groundwater flow volume with respect to its longer and narrower shape away from the source updip stratigraphic bedding

Energy and force analysis of Ti-6Al-4V linear friction welds for computational modeling input and validation data

The linear friction welding (LFW) process is finding increasing use as a manufacturing technology for the production of titanium alloy Ti-6Al-4V aerospace components. Computational models give an insight into the process, however, there is limited experimental data that can be used for either modeling inputs or validation. To address this problem, a design of experiments approach was used to investigate the influence of the LFW process inputs on various outputs for experimental Ti-6Al-4V welds. The finite element analysis software DEFORM was also used in conjunction with the experimental findings to investigate the heating of the workpieces. Key findings showed that the average interface force and coefficient of friction during each phase of the process were insensitive to the rubbing velocity; the coefficient of friction was not coulombic and varied between 0.3 and 1.3 depending on the process conditions; and the interface of the workpieces reached a temperature of approximately approximately 1273 K (1000 °C) at the end of phase 1. This work has enabled a greater insight into the underlying process physics and will aid future modeling investigations.EPSRC, Boeing Company, Welding Institut

A pragmatic multi-centre randomised controlled trial of fluid loading in high-risk surgical patients undergoing major elective surgery - the FOCCUS study

Peer reviewedPublisher PD

Antimicrobials: A Global Alliance For Optimizing Their Rational Use In Intra-abdominal Infections (agora)

Intra-abdominal infections (IAI) are an important cause of morbidity and are frequently associated with poor prognosis, particularly in high-risk patients. The cornerstones in the management of complicated IAIs are timely effective source control with appropriate antimicrobial therapy. Empiric antimicrobial therapy is important in the management of intra-abdominal infections and must be broad enough to cover all likely organisms because inappropriate initial antimicrobial therapy is associated with poor patient outcomes and the development of bacterial resistance. The overuse of antimicrobials is widely accepted as a major driver of some emerging infections (such as C. difficile), the selection of resistant pathogens in individual patients, and for the continued development of antimicrobial resistance globally. The growing emergence of multi-drug resistant organisms and the limited development of new agents available to counteract them have caused an impending crisis with alarming implications, especially with regards to Gram-negative bacteria. An international task force from 79 different countries has joined this project by sharing a document on the rational use of antimicrobials for patients with IAIs. The project has been termed AGORA (Antimicrobials: A Global Alliance for Optimizing their Rational Use in Intra-Abdominal Infections). The authors hope that AGORA, involving many of the world's leading experts, can actively raise awareness in health workers and can improve prescribing behavior in treating IAIs.11NIAID NIH HHS [R01 AI117211

The Global Alliance for Infections in Surgery : defining a model for antimicrobial stewardship-results from an international cross-sectional survey

Background: Antimicrobial Stewardship Programs (ASPs) have been promoted to optimize antimicrobial usage and patient outcomes, and to reduce the emergence of antimicrobial-resistant organisms. However, the best strategies for an ASP are not definitively established and are likely to vary based on local culture, policy, and routine clinical practice, and probably limited resources in middle-income countries. The aim of this study is to evaluate structures and resources of antimicrobial stewardship teams (ASTs) in surgical departments from different regions of the world. Methods: A cross-sectional web-based survey was conducted in 2016 on 173 physicians who participated in the AGORA (Antimicrobials: A Global Alliance for Optimizing their Rational Use in Intra-Abdominal Infections) project and on 658 international experts in the fields of ASPs, infection control, and infections in surgery. Results: The response rate was 19.4%. One hundred fifty-six (98.7%) participants stated their hospital had a multidisciplinary AST. The median number of physicians working inside the team was five [interquartile range 4-6]. An infectious disease specialist, a microbiologist and an infection control specialist were, respectively, present in 80.1, 76.3, and 67.9% of the ASTs. A surgeon was a component in 59.0% of cases and was significantly more likely to be present in university hospitals (89.5%, p <0.05) compared to community teaching (83.3%) and community hospitals (66.7%). Protocols for pre-operative prophylaxis and for antimicrobial treatment of surgical infections were respectively implemented in 96.2 and 82.3% of the hospitals. The majority of the surgical departments implemented both persuasive and restrictive interventions (72.8%). The most common types of interventions in surgical departments were dissemination of educational materials (62.5%), expert approval (61.0%), audit and feedback (55.1%), educational outreach (53.7%), and compulsory order forms (51.5%). Conclusion: The survey showed a heterogeneous organization of ASPs worldwide, demonstrating the necessity of a multidisciplinary and collaborative approach in the battle against antimicrobial resistance in surgical infections, and the importance of educational efforts towards this goal.Peer reviewe