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Laser direct metal deposition has wide application in the areas of rapid manufacturing, surface coating, and component repair. Defects of interlayer and intralayer porosity are often observed in laser deposited structures and repaired components. Interlayer porosity can be controlled to some extent by adjusting processing parameters, but there is still disagreement as to the source of intralayer porosity and whether process conditions, process parameters, or initial powder materials are the dominant causal factor. In this work, two samples of Ti–6Al–4V powder, prepared using gas-atomization and the plasma rotating electrode (PREP) process, were analyzed using laser diffraction and microcomputed tomography for any initial porosity content. A 1.5 kW diode laser with a coaxial deposition head was then used to deposit a number of thin-wall structures with the different powders at different processing parameters. The deposited structures were characterized using scanning electron microscopy and microcomputed tomography. The results show a clear positive relationship between initial power porosity and intralayer porosity in deposition samples. However, the effect of processing parameters is more complex and analysis reveals that other factors such as strong Marangoni flow, pool instability, and the surrounding atmosphere may have an effect. The main trends found are a reduction in porosity with increased power and high porosity at very low mass flow rates; thus, for high value parts, PREP powder, higher power, and moderate powder mass flow rate, as dictated by other process constraints, appears to be a practical combination.

Multiple analytical and numerical models of the laser metal deposition process have been presented, but most rely on sequential solution of the energy and mass balance equations or discretization of the problem domain. Laser direct metal deposition is a complex process involving multiple interdependent processes which can be best simulated using a fully coupled mass-energy balance solution. In this work a coupled analytical–numerical solution is presented. Sub-models of the powder stream, quasi-stationary conduction in the substrate and powder assimilation into the area of the substrate above the liquidus temperature are combined. An iterative feedback loop is used to ensure mass and energy balances are maintained at the melt pool. The model is verified using Ti–6Al–4V single track deposition, produced with a coaxial nozzle and a diode laser. The model predictions of local temperature history, the track profile and microstructure scale show good agreement with the experimental results. The model is a useful industrial aid and alternative to finite element methods for selecting the parameters to use for laser direct metal deposition when separate geometric and microstructural outcomes are required.

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Overweight and obesity have become a significant health hazard among adolescents on account of quick growth in its occurrence rate and its common comorbidities like cardiometabolic disease (CMD). The aim of this study was to evaluate the prevalence of adiposity and assess the risk of CMD among university students in Eastern Province, Saudi Arabia. A cross-sectional study was conducted during the academic year 2017–2018, in a sample of 310 subjects (127 males; 183 females). The measurements were taken using standardized instruments including Body Mass Index (BMI), Fat Mass Index (FMI), Body Fat Percentage BFP), Mass of Body Fat (MBF), Visceral Fat Area (VFA), Waist Circumference (WC), and Waist to Hip Ratio (WHR). Moreover, CMD risk indicators were calculated by Conicity index (C index), WC, and WHR. The findings showed that the majority was overweight and obese (16.8% and 21.6%, respectively). While evaluating obesity indicators, males were found to have higher adiposity (obese students 34.6%) compared to female students (12.6%; p < 0.001). Additionally, FMI showed that the mean was significantly higher among males (8.65 ± 6.06) compared to females (7.26 ± 3.30; p < 0.019). Analysis of the predictors’ indices for cardiometabolic risk score highlighted a significantly higher percentage of WC, WHR, and C index among male students (50, 38.5, 59) compared to females (16.9, 14.2, 34; p < 0.001). Significant positive correlations were observed between C index quartiles and BMI with the other cardiometabolic indices ( p < 0.001). This study highlighted a high prevalence of adiposity and CMD risk among university students. The prediction of CMD in early age is quite helpful in preventing adiposity related health issues. Decision makers need to spread awareness about healthy consumption as well as the relationship between physical inactivity and chronic diseases.

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