A STEADY PSEUDO-COMPRESSIBILITY APPROACH BASED ON UNSTRUCTURED HYBRID FINITE VOLUME TECHNIQUES APPLIED TO TURBULENT PREMIXED FLAME PROPAGATION

A pseudo-compressibility method for zero Mach number turbulent reactive flows with heat release is combined with an unstructured finite volume hybrid grid scheme. The spatial discretization is based on an overlapped cell vertex approach. An infinite freely planar flame propagating into a turbulent medium of premixed reactants is considered as a test case. The recourse to a flamelet combustion modeling for which the reaction rate is quenched in a continuous way ensures the uniqueness of the turbulent flame propagation velocity. To integrate the final form of discretized governing equations, a three-stage hybrid time-stepping scheme is used and artificial dissipation terms are added to stabilize the convergence path towards the final steady solution. The results obtained with such a numerical procedure prove to be in good agreement with those reported in the literature on the very same flow geometry. Indeed, the flame structure as well as its propagation velocity are accurately predicted thus confirming the validity of the approach followed and demonstrating that such a numerical procedure will be a valuable tool to deal with complex reactive flow geometries

A new method for the identification of cohesive laws under pure loading modes

In this work, a new and simple methodology is proposed to identify the cohesive law of composite materials submitted to pure mode I and II loading. This methodology combines the experimental measured crack opening displacement and corresponding strain energy release rate with numerical simulation, using finite element method including cohesive zone modelling. The proposed procedure was tested and validated numerically, considering the determination of cohesive laws with different shapes for pure mode I and II loading. This was accomplished using the double cantilever beam (mode I) and end-notched flexure (mode II) tests. It was verified that the proposed methodology points towards the unicity of the identified solution and reproduces well the cohesive laws used as input.The first and third author acknowledges the Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020. The second author acknowledges FCT for the conceded financial support through the reference projects PTDC/EME-SIS/28225/2017 and UID/EEA/04436/2019. The fourth author acknowledges the “Laboratório Associado de Energia, Transportes e Aeronáutica”(LAETA) for the financial support by the project UID/EMS/50022/2013, and to the funding of Project NORTE-01-0145-FEDER-000022 - SciTech - Science and Technology for Competitive and Sustainable Industries, co-financed by Programa Operacional Regional do Norte (NORTE2020), through Fundo Europeu de Desenvolvimento Regional (FEDER)

Fracture characterization of wood under Mode I loading using the SEN-TPB Test

Mode I fracture characterization was induced in wood (Picea abies L.) using the single-edge-notched beamloaded in three-point-bending. A developed data reduction scheme based on the equivalent linear elasticfracture mechanics was used to evaluate the Resistance-curve instead of classical methods. The method isfound on beam theory and crack equivalent concept taking into account the triangular stress relief regionthat develops in the crack vicinity. The method dispenses crack length monitoring in the course of theloading process, providing a complete Resistance-curve which is essential for a clear identification of thefracture energy. The validation of the procedure has been performed numerically using a bilinear cohesivedamage model, thus allowing the simulation of both damage initiation and growth. The numerical modelalso provided the critical specimen dimensions that permit the attainment of accurate evaluation of thefracture toughness in wood

Family conference: a quality tool in the communication process in palliative care

info:eu-repo/semantics/publishedVersio

Friction and wear behaviour of bacterial cellulose against articular cartilage

Bacterial cellulose (BC) is a natural and biocompatible material with unique properties, such as high water holding capacity, ultra-fine fibre network and high strength that makes it an attractive material for the repair of articular cartilage lesions. However, data on the tribological properties of BC is very scarce, particularly if natural articular cartilage is involved in the contact. In this work, unmodified BC pellicles were grown from Gluconacetobacter xylinus in order to be used as tribological samples against bovine articular cartilage (BAC) in the presence of phosphate buffered saline (PBS). The tribological assessment of the sliding pairs was accomplished using reciprocating pin-on-flat tests at 37ºC. The reciprocating sliding frequency and stroke length were kept constant at 1 Hz and 8 mm, respectively. Contact pressures ranging from 0.80 to 2.40 MPa were applied. The friction coefficient evolution was continuously monitored during the tests and the release of total carbohydrates into the lubricating solution was followed by means of the phenol-H2SO4 method as an attempt to evaluate wear losses. The morphology of worn surfaces was characterized by SEM/EDS and the main wear mechanisms were identified. Low friction coefficient values (~ 0.05) combined with the preservation of the mating surfaces (BC and BAC) indicate the potential of BC to be used as artificial cartilage for articular joints.Fundação para a Ciência e a Tecnologia (FCT

Galactooligosaccharides production by β-galactosidase immobilized onto magnetic polysiloxane–polyaniline particles

Magnetized polysiloxane coated with polyaniline (mPOS–PANI) was used as a support for β-galactosidase immobilization via glutaraldehyde. The galactooligosaccharides (GOS) production by this derivative was investigated under different initial lactose concentrations (5–50%) and temperatures (30–60 °C). The initial lactose concentration in the reaction media affected the total amounts of produced GOS and their time course production was described as a “bell-shaped” curve as a result of the balance between transgalactosylation and hydrolysis. No significative difference was observed for the free and immobilized enzymes. The reaction rates for lactose hydrolysis and GOS formation increased with increasing temperature from 30 °C to 60 °C, but GOS production at all lactose conversion levels was almost unchanged with changing temperature. The mPOS–PANI matrix was also characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), thermomagnetization, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).European Union Programme of High Level Scholarships for Latin America - Programme Alban ((Scholarship No. E05D057787BR)Brazilian National Research Council (CNPq

Mode I fracture characterization of wood using the SEN-TPB test

The single-edge-notched beam loaded in three-point-bending has been numerically analyzed to validate its adequacy tocharacterize wood fracture under pure mode I loading. This specimen geometry has been chosen since it is particularlyuseful to perform tests in those fracture systems impossible to be tested with the double cantilever beam (DCB). Thestudy revealed several aspects avoiding the direct measurement of fracture toughness in wood due to confinement of thefracture process zone (FPZ) under loading. This has been confirmed analyzing stress profiles of different specimensizes, differently affected by compression due to bending

Mode II Fracture of Cortical Bone Tissue

In this work a numerical study has been performed to verify the adequacy of the End Notched Flexure (ENF) test todetermine the fracture toughness under mode II loading of cortical bovine bone tissue. In this work a detailed numericalanalysis using the finite element method and a cohesive damage model was performed in order to optimize thespecimen geometry when applied to bone fracture characterization under mode II loading. A data reduction schemebased on specimen compliance and crack equivalent concept was used to overcome the difficulties inherent to crackmonitoring during its growth. It was verified that a judicious selection of the geometry allows a rigorous estimation oftoughness in mode II

Determination of Mode I Fracture Toughness of Cortical Human Bone using the DCB Test

The fracture behaviour of human cortical bone was analysed considering a miniaturized version of theDouble Cantilever Beam (DCB) test. A specific data reduction scheme based on crack equivalentconcept was used to obtain the resistance curves. The definition of the cohesive laws mimicking thefracture process was performed measuring the crack tip opening displacement by digital imagecorrelation during the test. The differentiation of the relation between the strain energy release rate andcrack tip opening displacement allows to define the experimental cohesive law. In order to validate theprocedure, trapezoidal cohesive laws with bilinear softening were adjusted to the experimental ones.The DCB tests were simulated by finite element analysis including cohesive zone modelling with theadjusted laws. The resulting numerical load-displacement and resistance curves were compared withthe numerical ones. Good agreement was obtained which validates the proposed procedure