Textile injection process characterisation by means of a spiral mould

New developments are being carried out within the injection moulding field, such as gas injection, bi-injection, co-injection, sequential injection, compression injection or textile injection processes. These techniques require new developments as they highly modify design and process conditions. In this work, the influence over the plastic material flow of the introduction of different film textiles into the mould is measured. A specific measurement system consisting of a monitorised spiral mould with pressure sensors has been used to measure the influence of different tissues over the mould pressures. As an application of this measurement system, a viscous model is generated to characterise the rheological behaviour of the thermoplastic and textile joint. The viscous model obtained is applied on a conventional CAE tool for the simulation of textile injection pressure results for the different film textiles analysed

A new look at blood shear-thinning

Blood viscosity decreases with shear stress, a property essential for an efficient perfusion of the vascular tree. Shear-thinning is intimately related to the dynamics and mutual interactions of red blood cells (RBCs), the major constituents of blood. Our work explores RBCs dynamics under physiologically relevant conditions of flow strength, outer fluid viscosity and volume fraction. Our results contradict the current paradigm stating that RBCs should align and elongate in the flow direction thanks to their membrane circulation around their center of mass, reducing flow-lines disturbances. On the contrary, we observe both experimentally and with simulations, rich morphological transitions that relate to global blood rheology. For increasing shear stresses, RBCs successively tumble, roll, deform into rolling stomatocytes and finally adopt highly deformed and polylobed shapes even for semi-dilute volume fractions analogous to microcirculatory values. Our study suggests that any pathological change in plasma composition, RBCs cytosol viscosity or membrane mechanical properties will impact the onset of shape transitions and should play a central role in pathological blood rheology and flow behavior

Analysis of self-lubrication enhancement via PA66 strategies: Texturing and nano-reinforcement with ZrO2 and graphene

Graphene nanoflakes and zirconium dioxide (ZrO2) were added to polyamide 66-based composites with glass fibre in order to improve their self-lubricating properties and make them suitable for high-performance bearing applications. The influence of texturing the surfaces was also investigated. The tribological behaviour was analysed for different combinations of hybrid polymeric composites, percentages of additive, and texturing geometries. The results show that the lowest low friction coefficients are obtained for PA66 + 30GF with 5% graphene. Worn surfaces, analysed by scanning electron microscopy and optical microscopy confirm the enhancement of the tribological properties with the addition of graphene. Texturing results under dry lubrication are not relevant for tribological purposes

The influence of environmental conditions on the dimensional stability of components injected with PA6 and PA66

The design of assembly components requires special attention to aspects related to their dimensions to ensure their functionality. The goal of this paper is to analyse the influence of case-based environmental conditions, including extreme hydrothermal conditions, on the dimensional stability of a component made from different polyamides throughout the component''s working life. The results support the conclusion that components made from PA6 have a higher capacity to absorb humidity than those made from PA66 and, on the other hand, a higher capacity to lose this humidity, which implies a more significant effect on the average error in the dimensions considered (12% for PA6 in comparison to 3% for PA66). With regard to assembly dimensions, components remain within dimensional tolerances under average and extreme humidity conditions and average temperature conditions. Components injected with P66 are more stable for all of the situations analysed

Enhancement of tribological behavior of rolling bearings by applying a multilayer ZrN/ZrCN coating

This paper focuses on the tribological behaviour of ZrN/ZrCN coating on bearing steel substrates DIN 17230, 100Cr6/1.3505. Coatings are applied at room temperature processes by means of Cathodic Arc Evaporation (CAE), a kind of Physical Vapor Deposition (PVD) technique. In order to achieve a satisfactory compromise between coating-substrate adhesion and the surface roughness requirement of the bearing rings, a polish post-processing is proposed. Different polish post-processing times and conditions are applied. The coated and polished bearing rings are tested under real friction torque test protocols. These tests show that the application of the coating does not entail a significant improvement in friction performance of the bearing. However, fatigue tests in real test bench are pending to evaluate the possible improvement in bearing life time

Dimensional Stability and Process Capability of an Industrial Component Injected with Recycled Polypropylene

The usage of recycled polymers for industrial purposes arises as one of the most promising methods of reducing environmental impact and costs associated with scrapping parts. This paper presents a systematic study of the dimensional stability of a raw and 100% recycled polypropylene subjected to realistic environmental conditions occurring along its working life. The component studied is an internal part of an induction hob assembly. Industrial samples manufactured with both materials, in the same mold, and in the same injection machine, are subjected to ejection conditions, storage conditions (50 °C), and extreme performance conditions (80 °C). Induced dimensional changes are registered and analyzed using a coordinate measuring machine, and a tactile sensing probe. To verify the process capability of the samples manufacturing, Cp and Cpk values are calculated to evaluate the suitability of the recycled material as an alternative. Results conclude that, although the use of recycled material implies slight differences in terms of dimensional stability due to the changes induced in the polymer structure, these differences are not significant enough to affect the injection process capability. Therefore, recycling arises as one effective method to reduce both overruns associated with the consumption of raw polypropylene material and its environmental impact

Tribological performance of nylon composites with nanoadditives for self-lubrication purposes

A systematic study comparing the wear behaviour of composites with nylon matrix (PA66, PA46, PA12) and different nanoadditives and reinforcing additives (graphite, graphene, MoS2 and ZrO2) has been carried out in order to achieve a proper self-lubricant material for bearing cages. The wear characterisation was done using pin-on-disc tests, SEM and EDX analysis. The results show that better outcomes are obtained for composites based on PA12. The addition of ZrO2 offers negative values of wear due to the metallic particle transference from the counterface to the polymeric pin

Analytical solutions for radiation-driven winds in massive stars - II: The δ-slow regime

Accurate mass-loss rates and terminal velocities from massive stars winds are essential to obtain synthetic spectra from radiative transfer calculations and to determine the evolutionary path of massive stars. From a theoretical point of view, analytical expressions for the wind parameters and velocity profile would have many advantages over numerical calculations that solve the complex non-linear set of hydrodynamic equations. In a previous work, we obtained an analytical description for the fast wind regime. Now, we propose an approximate expression for the line-force in terms of new parameters and obtain a velocity profile closed-form solution (in terms of the Lambert W function) for the δ-slow regime. Using this analytical velocity profile, we were able to obtain the mass-loss rates based on the m-CAK theory. Moreover, we established a relation between this new set of line-force parameters with the known stellar and m-CAK line-force parameters. To this purpose, we calculated a grid of numerical hydrodynamical models and performed a multivariate multiple regression. The numerical and our descriptions lead to good agreement between their values.Fil: Araya, I.. Universidad Mayor; ChileFil: Christen, A.. Universidad de Valparaíso; ChileFil: Cure, M.. Universidad de Valparaíso; ChileFil: Cidale, Lydia Sonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Venero, Roberto Oscar José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Arcos, C.. Universidad de Valparaíso; ChileFil: Gormaz Matamala, A.. Universidad de Valparaíso; Chile. Universidad Adolfo Ibañez; ChileFil: Haucke, Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Escarate, P.. Universidad Austral de Chile; ChileFil: Clavería, H.. Pontificia Universidad Católica de Valparaíso; Chil

Orbital Elements and Individual Component Masses from Joint Spectroscopic and Astrometric Data of Double-line Spectroscopic Binaries*

Abstract We present orbital elements, orbital parallaxes, and individual component masses for 14 spatially resolved double-line spectroscopic binaries derived doing a simultaneous fit of their visual orbit and radial velocity curve. This was done by means of a Markov Chain Monte Carlo code developed by our group that produces posterior distribution functions and error estimates for all of the parameters. Of this sample, six systems had high-quality previous studies and were included as benchmarks to test our procedures, but even in these cases, we could improve the previous orbits by adding recent data from our survey of southern binaries being carried out with the HRCam and ZORRO speckle cameras at the SOAR 4.1 m and Gemini South 8.1 m telescopes, respectively. We also give results for eight objects that did not have a published combined orbital solution, one of which did not have a visual orbit either. We could determine mass ratios with a typical uncertainty of less than 1%, mass sums with uncertainties of about 1%, and individual component masses with a formal uncertainty of 0.01 M ⊙ in the best cases. A comparison of our orbital parallaxes with available trigonometric parallaxes from Hipparcos and Gaia eDR3 shows a good correspondence, the mean value of the differences being consistent with zero within the errors of both catalogs. We also present observational H-R diagrams for our sample of binaries, which, in combination with isochrones from different sources, allowed us to assess their evolutionary status and the quality of their photometry.</jats:p

The rkpU gene of Sinorhizobium fredii HH103 is required for bacterial K-antigen polysaccharide production and for efficient nodulation with soybean but not with cowpea

In this work, the role of the rkpU and rkpJ genes in the production of the K-antigen polysaccharides (KPS) and in the symbiotic capacity of Sinorhizobium fredii HH103, a broad host-range rhizobial strain able to nodulate soybean and many other legumes, was studied. The rkpJ- and rkpU-encoded products are orthologous to Escherichia coli proteins involved in capsule export. S. fredii HH103 mutant derivatives were contructed in both genes. To our knowledge, this is the first time that the role of rkpU in KPS production has been studied in rhizobia. Both rkpJ and rkpU mutants were unable to produce KPS. The rkpU derivative also showed alterations in its lipopolysaccharide (LPS). Neither KPS production nor rkpJ and rkpU expression was affected by the presence of the flavonoid genistein. Soybean (Glycine max) plants inoculated with the S. fredii HH103 rkpU and rkpJ mutants showed reduced nodulation and clear symptoms of nitrogen starvation. However, neither the rkpJ nor the rkpU mutants were significantly impaired in their symbiotic interaction with cowpea (Vigna unguiculata). Thus, we demonstrate for the first time to our knowledge the involvement of the rkpU gene in rhizobial KPS production and also show that the symbiotic relevance of the S. fredii HH103 KPS depends on the specific bacterium–legume interaction