Influence of Bifilm Defects Generated during Mould Filling on the Tensile Properties of Al–Si–Mg Cast Alloys

Entrapped double oxide film defects are known to be the most detrimental defects during the casting of aluminium alloys. In addition, hydrogen dissolved in the aluminium melt was suggested to pass into the defects to expand them and cause hydrogen porosity. In this work, the effect of two important casting parameters (the filtration and hydrogen content) on the properties of Al–7 Si–0.3 Mg alloy castings was studied using a full factorial design of experiments approach. Casting properties such as the Weibull modulus and position parameter of the elongation and the tensile strength were considered as response parameters. The results suggested that adopting 10 PPI filters in the gating system resulted in a considerable boost of the Weibull moduli of the tensile strength and elongation due to the enhanced mould filling conditions that minimised the possibility of oxide film entrainment. In addition, the results showed that reducing the hydrogen content in the castings samples from 0.257 to 0.132 cm3/100 g Al was associated with a noticeable decrease in the size of bifilm defects with a corresponding improvement in the mechanical properties. Such significant effect of the process parameters studied on the casting properties suggests that the more careful and quiescent mould filling practice and the lower the hydrogen level of the casting, the higher the quality and reliability of the castings produced.

Corrosion resistance evaluation of carbon and vanadium-based sputtered coatings on steel substrates

Steels are in constant contact with fluids that could generate corrosion regardless the application in which this steel is located. AISI-SAE 1045 like steels is widely used in different applications in engineering, even several of these parts made of this steel suffers wear processes. The synergy between corrosion and wear phenomena exacerbates the detriment of some physical properties of the material conducing it to a failure. A potential alternative to avoid this issue is to coat the material surface with an anticorrosive material, and among different techniques to produce coatings, physical vapor deposition ones are environmentally friendly, secure and with excellent properties on the final product. We report the production of coatings based on vanadium and carbon on AISI-SAE 1045 steels substrates varying some of the deposition parameters in a sputtering coatings machine. A 23-factorial design of experiments was done with power applied to the vanadium target, power applied to the carbon target and temperature as active factors with two levels each one. A relevant effect of the power applied to V target and temperature on the anticorrosive properties of the coatings was found, thus increasing these factors levels always gives higher surface roughness and higher corrosion rates, this result together provides an important insight into the values that must be considered to achieve good anticorrosive properties on the material. Overall, these results indicate that with low V target power and room temperature, and high C target power the lowest corrosion rates and roughness of the group are achieved, both results agree.

Integrated Surrogate Optimization of a Vertical Axis Wind Turbine

In this work, a 3D computational model based on computational fluid dynamics (CFD) is built to simulate the aerodynamic behavior of a Savonius-type vertical axis wind turbine with a semi-elliptical profile. This computational model is used to evaluate the performance of the wind turbine in terms of its power coefficient (Cp). Subsequently, a full factorial design of experiments (DOE) is defined to obtain a representative sample of the search space on the geometry of the wind turbine. A dataset is built on the performance of each geometry proposed in the DOE. This process is carried out in an automated way through a scheme of integrated computational platforms. Later, a surrogate model of the wind turbine is fitted to estimate its performance using machine learning algorithms. Finally, a process of optimization of the geometry of the wind turbine is carried out employing metaheuristic optimization algorithms to maximize its Cp; the final optimized designs are evaluated using the computational model for validating their performance.

Experimental Investigation on the Effect of Carbon Fiber Reinforcements in the Mechanical Resistance of 3D Printed Specimens

In the last years, fiber-reinforced polymer composites have been under study for additive manufacturing. For this purpose, it is important to assess the behavior of these materials in terms of mechanical properties. The present experimental study evaluates the mechanical resistance of both PLA and carbon fiber reinforced PLA. The work used a full factorial Design of Experiments (108 tests) selecting as factors the infill density, infill pattern, material, number of perimeters and printing orientation. The main results highlight that the most influential factors on the tensile strength are both type of material and number of perimeters. In this study, the use of reinforcements did not improve the mechanical resistance attained by the corresponding virgin material. Particularly, for some selected specimens, the porosity measured in the fracture section is larger for the reinforced PLA specimens, so they showed a smaller cross-section.

Extrusion and Injection Molding of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx): Influence of Processing Conditions on Mechanical Properties and Microstructure

Biobased and biodegradable polyhydroxyalkanoates (PHAs) have great potential as sustainable packaging materials. However, improvements in their processing and mechanical properties are necessary. In this work, the influence of melt processing conditions on the mechanical properties and microstructure of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) is examined using a full factorial design of experiments (DoE) approach. We have found that strict control over processing temperature, mold temperature, screw speed, and cooling time leads to highly increased elongation at break values, mainly under influence of higher mold temperatures at 80 °C. Increased elongation of the moldings is attributed to relaxation and decreased orientation of the polymer chains together with a homogeneous microstructure at slower cooling rates. Based on the statistically substantiated models to determine the optimal processing conditions and their effects on microstructure variation and mechanical properties of PHBHHx samples, we conclude that optimizing the processing of this biopolymer can improve the applicability of the material and extend its scope in the realm of flexible packaging applications.

A pre-formulation study of tetracaine loaded in optimized nanostructured lipid carriers

Tetracaine (TTC) is a local anesthetic broadly used for topical and spinal blockade, despite its systemic toxicity. Encapsulation in nanostructured lipid carriers (NLC) may prolong TTC delivery at the site of injection, reducing such toxicity. This work reports the development of NLC loading 4% TTC. Structural properties and encapsulation efficiency (%EE > 63%) guided the selection of three pre-formulations of different lipid composition, through a 23 factorial design of experiments (DOE). DLS and TEM analyses revealed average sizes (193–220 nm), polydispersity (< 0.2), zeta potential |− 21.8 to − 30.1 mV| and spherical shape of the nanoparticles, while FTIR-ATR, NTA, DSC, XRD and SANS provided details on their structure and physicochemical stability over time. Interestingly, one optimized pre-formulation (CP-TRANS/TTC) showed phase-separation after 4 months, as predicted by Raman imaging that detected lack of miscibility between its solid (cetyl palmitate) and liquid (Transcutol) lipids. SANS analyses identified lamellar arrangements inside such nanoparticles, the thickness of the lamellae been decreased by TTC. As a result of this combined approach (DOE and biophysical techniques) two optimized pre-formulations were rationally selected, both with great potential as drug delivery systems, extending the release of the anesthetic (> 48 h) and reducing TTC cytotoxicity against Balb/c 3T3 cells.

Cold Gas Spray of Copper on Aluminum Nitride as Substrate for Power Electronics

Ceramic substrates for electronic packaging of high-power applications are growing in demand due to their robustness as power and thermal requirements increase. Aluminum nitride (AlN) has excellent thermal and electrical properties with copper currently being bonded to AlN via a direct bond copper (DBC) technique. However, substrates fabricated by DBC are subjected to thermo-mechanical fatigue during fabrication processes and power cycling. DBC substrate’s reliability is negatively affected by the large mismatch in coefficient of thermal expansion that hinders the possibility of thicker substrates, therefore limiting its use for applications above 20 kV. This work employed cold gas spraying (CGS) to mechanically bond Cu on AlN. CGS is a low-temperature additive manufacturing method that accelerates powder particles at near-supersonic velocities to impact a surface causing plastic deformation and mechanical bonding. On ceramic-metal systems CGS has not been widely studied owing to ceramics’ inability to deform plastically, therefore, surface functionalization was performed to enhance the mechanical interlocking mechanism. A factorial design of experiments (DOE) was used to assess the effect of factors: temperature, pressure, stand-off distance, angle of deposition, and travel speed on various substrate surfaces in the CGS fabrication process. These experiments resulted in a successful deposition of copper on AlN.

Advances in efficiency in the groove milling of aluminium EN AW 2024-T3 with zig-zag and trochoidal strategies

Manufacturing process engineers must continually take decisions to make the processes efficient. Manufacturing time, surface finish and energy consumption are aspects to be optimized in machining. This study analyzes the efficiency of groove milling in milling aluminum alloys EN AW 2024-T3 with zig-zag and trochoidal strategies. Dynamic milling is designed to maximize the removal rate and optimize the tool performance. This generates a discontinuous cutting with minimum of heat reducing build-up with an optimal chip removal minimizing cutting edge wear. The influence of lateral pitch, feed per tooth, cutting speed and coolant pressure has been analyzed. The depth of curt has been adapted for each strategy and tool type. The study was proposed through a factorial design of experiments by the Taguchi method. The machining time (T) and energy consumption (EC) show a strong influence of the lateral step (a e ) in conventional milling. A similar level of influence appears with the feed per tooth (f z ) on the trochoidal. The roughness (Ra) is more influenced by cutting speed (V c ) for conventional milling and by feed per tooth (f z ) and lateral pitch (a e ) for the trochoidal.

Prediction of bond strength in the fused shirt composites

Purpose Bond strength is an indicator of the quality of the fusing process. The study's primary purpose is to predict the bond strength using easily measurable variables. This study focuses on shirting fabrics fused with woven interlinings and changes in bond strength before and after washing. Design/methodology/approach This study attempts to model and predict bond strength of fused shirt composites using an initial screening design followed by full factorial design of experiments. After screening out, those found significantly affecting the bond strength are fabric fiber content, interlining areal weight and fusing temperature. This study proposes the regression models explaining the effect of the three variables on bond strength before and after washing the fused composites. Findings This study found that heavy interlinings (250 g/sq.m) require higher fusing temperatures than the lighter interlining (225 g/sq.m). After washing, the bond strength of samples fused at high temperatures reduced in some instances. Maintaining a high temperature without considering interlining weight can lower the bond strength after washing the fused composites. Originality/value A combination of screening and full factorial DOE is used to analyze and predict bond strength of composites comprising medium-weight shirting fabrics and heavier weight interlinings used in shirts.

Design of experiment-driven stability-indicating RP-HPLC method for the determination of tofacitinib in nanoparticles and skin matrix

Background Tofacitinib—an oral JAK inhibitor—has been recently approved by US FDA to treat moderate to severe RA. The delivery of tofacitinib to specific inflammation site at joint via topical route using nanoformulations helps in managing the potential adverse effects. The objective is to develop and validate a simple, specific, and sensitive stability-indicating HPLC method for quantification of tofacitinib in topical nanoformulations and different matrices (adhesive tape, and skin layers, i.e., stratum corneum, viable epidermis, and dermis). The major objective was to avoid use of instruments like LC–MS/MS and to ensure a widespread application of the method. Result A 32 factorial ‘design of experiments’ was applied to optimize process variables, to understand the effect of variables on peak properties. The calibration curve showed regression coefficient (R2) 0.9999 and linearity in the concentration range of 50 to 15,000 ng/mL, which is suitable for the analysis of conventional dosage forms and nanoformulations. Method validation was performed as per ICH guideline Q2 (R1). The accuracy by recovery studies ranged between 98.09 and 100.82%. The % relative standard deviations in intraday and interday precisions were in the range of 1.16–1.72 and 1.22–1.80%, respectively. Forced degradation studies indicated the specificity of method and showed stability-indicating potential for tofacitinib peak. Conclusion The validated method provides a quantification method of tofacitinib in the presence of formulation excipients, dissolution media, and skin tissues in detail. In addition, the method was successfully utilized for determination of various dermatokinetics profile of tofacitinib.