A full factorial numerical investigation and validation of precision end milling process for hardened tool steel

Tool steel materials have poor machinability, as the high hardness of the material will cause high cutting forces, premature failure of the cutting tools, and is also associated with machining induced tensile stresses within the work piece. Due to high experimental costs, there is no recent research on end milling tool steel, using full factorial experimental or numerical design. A 3D FE-model of a precision end milling process with a two flute ball nose cutter were established in this paper. The FE-Model used a subroutine to model hardening realised through the Johnson-Cook model, additionally were a material removal criteria developed and implemented. Through full factorial numerical simulations the influence of cutting parameters on cutting force of H13 tool steel was studied. Depth of cut was found to be the most influential machining parameter on cutting forces followed by feed rate and surface speed. Four milling experiments were carried out to validate the simulation results. It was found that the simulation and the experiments had a good agreement on the cutting forces. The validated FEA model can be used for further studies on residual stress or temperatures and to optimise the cutting process

Prehospital critical care is associated with increased survival in adult trauma patients in Scotland

Background Scotland has three prehospital critical care teams (PHCCTs) providing enhanced care support to a usually paramedic-delivered ambulance service. The effect of the PHCCTs on patient survival following trauma in Scotland is not currently known nationally. Methods National registry-based retrospective cohort study using 2011-2016 data from the Scottish Trauma Audit Group. 30-day mortality was compared between groups after multivariate analysis to account for confounding variables. Results Our data set comprised 17 157 patients, with a mean age of 54.7 years and 8206 (57.5%) of male gender. 2877 patients in the registry were excluded due to incomplete data on their level of prehospital care, leaving an eligible group of 14 280. 13 504 injured adults who received care from ambulance clinicians (paramedics or technicians) were compared with 776 whose care included input from a PHCCT. The median Injury Severity Score (ISS) across all eligible patients was 9; 3076 patients (21.5%) met the ISS>15 criterion for major trauma. Patients in the PHCCT cohort were statistically significantly (all p < 0.01) more likely to be male; be transported to a prospective Major Trauma Centre; have suffered major trauma; have suffered a severe head injury; be transported by air and be intubated prior to arrival in hospital. Following multivariate analysis, the OR for 30-day mortality for patients seen by a PHCCT was 0.56 (95% CI 0.36 to 0.86, p=0.01). Conclusion Prehospital care provided by a physician-led critical care team was associated with an increased chance of survival at 30 days when compared with care provided by ambulance clinicians

Numerical investigation of mechanical induced stress during precision end milling hardened tool steel

Hardened tool steels are widely used materials for forming dies, due to their increased strength and hardness. However, their machinability is very poor, due to the high hardness of the material, which leads to high cutting forces and premature failure of the cutting tools. This is also associated with machining induced tensile stresses within the work piece. No full factorial design has been performed when end milling tool steel, due to the high associated costs. Instead of physical experiments, numerical models are commonly used to save cost and time. However, most of the recent research focus was only on 2D FE-Models. 2D model can be used for simulation of some simplified process, however, the results are not sufficient for accurate prediction. Therefore, a 3D FE-model of a precision end milling process with a two-flute ball nose cutter were established in this paper, in order to build a multi cutting edge model. In the FE-Model, a subroutine was implemented to model work piece hardening during the cutting process. The subroutine realised an accurate prediction of the residual stress and cutting forces. In addition, a material removal criterion was developed and implemented. The influence of cutting parameters on cutting force for end milling H13 tool steel was studied, through full factorial numerical simulations, to evaluate the effectiveness of this FEA model. Subsequently, after validation of the FEM model through machining trials, empirical models were developed for predicting cutting forces and residual stress. The cutting parameters evaluated were cutting speed, feed rate and depth of cut. In summary, it was found that the simulation and the experiments had a good agreement on the value and trend of the residual stress. The FEM model can be effectively used to predict residual stress in the machined surface

Remanufacturing H13 steel moulds and dies using laser metal deposition

The exploitation of Additive Manufacturing (AM) in the repair and remanufacture of industrial components, such as moulds and dies, has become an emerging research area due to the expected reduction of replacement cost and the promise of better mechanical and wear resistance properties – moreover, the use of remanufacturing standards ensures a greater than or equal to warranty part quality. Further studies plan to utilize Laser Metal Deposition (LMD) to remanufacture artificially worn H13 Steel samples, allowing benchmarking studies to be conducted in order to compare the mechanical and wear resistance performance of LMD against current welding repair technologies. The specimens will be subjected to an accelerated pressure and elevated temperatures schedule, simulating the loading cycles during the use of the die sets. The effects on the resulting part properties of different process parameters setup, including the type and characteristics of the deposited powder will be studied

Wear behaviour of laser cladded Ni-based WC composite coating for Inconel hot extrusion : practical challenges and effectiveness

In forging, tooling costs make up a significant percentage of the total manufacturing cost. To combat tool failure, forging dies can be manufactured using or including layers of high wear-resistant alloys. The present work compares the manufacturing process challenges and wear response of traditional Nitriding to laser cladding using Ni-based WC on an H13 substrate for IN718 extrusion. The results have shown that machining of NiCrSiB + WC matrix material is problematic, both with regards to cutting tool wear and achievable surface finish. Assessment of pre- and post-extrusion Nitrided H13 and NiCrSiB + 30%WC laser clad dies shows more significant wear features in the case of the additively coated die. Crack formation and surface discontinuities attributed to the effects of material porosity and die heating are also discussed

HBV and HCV test uptake and correlates among men who have sex with men in China: a nationwide cross-sectional online survey.

OBJECTIVES: Hepatitis B virus (HBV) and hepatitis C virus (HCV) cause substantial morbidity and mortality in low-income and middle-income countries, including China. WHO guidelines recommend men who have sex with men (MSM) receive HBV and HCV screening. The purpose of this study was to determine the proportion of MSM in China who have HBV and HCV tested and identify correlates of test uptake. METHODS: We conducted an online cross-sectional survey of young MSM in China. Respondents were asked to report previous HBV and HCV testing, sociodemographic information, sexual risk factors for hepatitis infection, other STI testing and primary care physician (PCP) status. Associations were analysed by logistic regression. RESULTS: 503 eligible MSM completed the survey. 41.0% (206/503) of MSM had HCV tested, and 38.2% (60/157) of MSM with no or uncertain HBV vaccination had HBV tested. In multivariate analysis, HCV testing was correlated with HBV testing (adjusted OR (aOR) 22.98, 95% CI 12.11 to 43.60), HIV testing (aOR 3.64, 95% CI 1.92 to 6.91), HIV-positive status (aOR 1.78, 95% CI 1.07 to 2.98) and having a PCP (aOR 2.40, 95% CI 1.44 to 3.98). Among MSM with no or uncertain HBV vaccination, HBV testing was correlated with HCV testing (aOR 80.85, 95% CI 20.80 to 314.33), HIV testing (aOR 5.26, 95% CI 1.81 to 15.28), HIV-positive status (aOR 3.00, 95% CI 1.22 to 7.37) and having a PCP (aOR 2.69, 95% CI 1.00 to 7.26). CONCLUSIONS: Our data suggest many young MSM in China have not received hepatitis testing. HCV testing rates were lower than those recently reported among MSM in Australia and the USA. The strong correlation between HBV and HCV testing suggests bundled testing interventions may be useful for MSM in China. Men with a PCP were more likely to have received hepatitis testing, consistent with literature demonstrating the importance of primary care in expanding access to testing

Physical activity, well-being and needs satisfaction in eight and nine-year-old children from areas of socio-economic disadvantage

Background: Need-supportive environments have been shown to contribute to children’s physical activity levels, and in a few cases, well-being. Grounded in Self-Determination Theory (SDT), the aim of this study was to determine the influence of psychological needs (competence and social relatedness) satisfaction on physical activity levels and well-being in children from areas of social and economic disadvantage.Method: A total of 211 children aged 8-9 years from areas of low socio-economic status wore an accelerometer for one week, and completed a questionnaire assessing psychological needs satisfaction and well-being. Confirmatory Factor Analysis (CFA) and path analysis was conducted to assess the factor structure of the measures, and test for theory predicting significant relationships between psychological needs, physical activity and well-being. Results: The factor structure of the instruments was supported, and a significant positive relationship was found between athletic competence and physical activity (β=.19). Athletic competence (β=.19), along with parental relatedness (β=.32), positively predicted children’s well-being. Physical activity alone, did not predict well-beingConclusions: Practitioners may want to consider components of SDT, reflective of need-supportive environments, when designing physical activity interventions. Interventions aimed at supporting children’s perceptions of competence, and the involvement of parents, may offer the opportunity to increase well-being. <br/

Investigating relationships between laser metal deposition deployment conditions and material microstructural evolution

Additive Manufacturing can be utilised for the repair and remanufacture of metallic components with reduced replacement costs and with the potential for better mechanical and wear resistance properties ensuring remanufactured components are better than or equal to originals. This paper presents the current data concerning Laser Metal Deposition deployment conditions and their relationship to material microstructure evolution and mechanical properties. The study highlights the need for experiments involving scan path geometry and topology and details the experiments currently in preparation

A single transcription factor is sufficient to induce and maintain secretory cell architecture

We hypothesized that basic helix–loop–helix (bHLH) MIST1 (BHLHA15) is a “scaling factor” that universally establishes secretory morphology in cells that perform regulated secretion. Here, we show that targeted deletion of MIST1 caused dismantling of the secretory apparatus of diverse exocrine cells. Parietal cells (PCs), whose function is to pump acid into the stomach, normally lack MIST1 and do not perform regulated secretion. Forced expression of MIST1 in PCs caused them to expand their apical cytoplasm, rearrange mitochondrial/lysosome trafficking, and generate large secretory granules. Mist1 induced a cohort of genes regulated by MIST1 in multiple organs but did not affect PC function. MIST1 bound CATATG/CAGCTG E boxes in the first intron of genes that regulate autophagosome/lysosomal degradation, mitochondrial trafficking, and amino acid metabolism. Similar alterations in cell architecture and gene expression were also caused by ectopically inducing MIST1 in vivo in hepatocytes. Thus, MIST1 is a scaling factor necessary and sufficient by itself to induce and maintain secretory cell architecture. Our results indicate that, whereas mature cell types in each organ may have unique developmental origins, cells performing similar physiological functions throughout the body share similar transcription factor-mediated architectural “blueprints.