A two-scale extended finite element method for modelling 3D crack growth with interfacial contact

3D fatigue crack growth problems are nowadays handled using X-FEM coupled with level set techniques. It is also well established that such an approach allows mesh-independent crack modelling and no remeshing during crack propagation. However, when contact and friction occur along the crack faces, a discretization of the internal variables linked to the interface law is necessary. The interface discretization is generally constructed from the finite elements cut by the crack. As a consequence, a mesh dependency between the bulk discretization and the interface discretization is introduced. However, the dimension of the possible non-linearities arising at the crack interface (like confined plasticity or unilateral contact with friction) may be several orders of magnitude finer than the crack size. A finer discretization is thus required to accurately capture these non-linearities. The aim of the present paper is to develop a method considering the 3D cracked structure and the crack interface as two independent global and local problems characterized by different length scales and different behaviors. Here, the interface is seen as an autonomous entity with its own discretization, variables and constitutive law. A formulation involving three-fields is used. The interface is linked to the global problem in a weak sense in order to avoid instabilities in the contact solution. Two iterative strategies are considered to solve the contact problem. Two-dimensional and three-dimensional numerical examples are presented to demonstrate the ability of the model to solve the contact at the crack interface with or without propagation at a given level of accuracy.     

Diffusion Coefficient Measurements Under Reduced Gravity Conditions by Means of the Shear Cell Technique. The Impact of Free Surfaces

A recent computational methodology is applied here in order to analyze the impact of free surfaces on the measurement of the interdiffusion coefficients if shear cells are used. Calculations indicate that the above-mentioned impact depends on the intensity of the solutal Marangoni convection but mainly on the number of active Marangoni segments, that is to say, on the extent of the free surface considered. Bulk solutal convection due to reduced gravity levels is not relevant if the gravity vector acts orthogonally to the gradient of concentration.     

Preparation of novel distinct highly aromatic liquors using fruit distillates

This work describes the preparation of aromatised liquors using deodorised and concentrated fruit distillates. The raw spirits were improved by making a partial deodorisation, using activated charcoal, followed by concentration, using a distiller. The liquors were prepared by a maceration process. The procedure is exemplified using fig distillates to prepare myrtle berry liquors. The acidity, copper, polyphenol and anthocyanin indexes and volatile and anthocyanin profiles were monitored in each preparation step. The concentration process increased the ethanol proof to 75% v/v and decreased the acidity and the copper content. The partial deodorisation decreased the levels of high molecular weight volatiles, while the content of lower molecular weight compounds that contribute to flavour was maintained. Delphinidin‐3‐O‐glucoside, cyanidin‐3‐O‐glucoside, petunidin‐3‐O‐glucoside and malvidin‐3‐O‐glucoside were the major anthocyanins.     

Sintering and conductivity of BaCe0.9Y0.1O2.95 synthesized by the sol-gel method

Ceramic powders of BaCe_0.9Y_0.1O_2.95 (BCY10) have been prepared by the sol-gel method. Barium and yttrium acetate and cerium nitrate were used as ceramic precursors in a water solution. The reaction process studied by DTA-TG and XRD showed that calcination of the precursor powder at T ≥ 1000 °C produces a single perovskite phase. The densification behaviour of green compacts studied by constant heating rate dilatometry revealed that the shrinkage rate was maximal at 1430 °C. Sintered densities higher than 95% of the theoretical one were thus obtained below 1500 °C. The bulk and additional blocking effects were characterized by impedance spectroscopy in wet atmosphere between 150 and 600 °C. A proton conduction behaviour was clearly identified. The blocking effect can be related to a space-charge depletion layer of protons in the vicinity of grain boundaries.     

Multiplex Real-time PCR for the Simultaneous Detection of Salmonella spp. and Listeria monocytogenes in Food Samples

In this study, we have developed a rapid method for the simultaneous detection of Listeria monocytogenes and Salmonella spp. in foods, combining culture enrichment and a multiplex real-time polymerase chain reaction (PCR). The assay used two pre-existing primer-probe sets, labelled with different reporter dyes to enable the direct distinction of the original contaminating agent. Amplification efficiency and inclusivity/exclusivity of the combined assay was successfully assessed. The overall process included the culture enrichment based on the ISO standard, consisting of 24 h incubation in appropriate media (Half Fraser Broth for Listeria and buffered peptone water (BPW) for Salmonella), followed by a single DNA extraction of mixed enrichment aliquots, and real-time PCR detection of the hly and bipA genes of L. monocytogenes and Salmonella spp., respectively. An internal amplification control, co-amplified during the PCR run, was included in the assay to verify the results. The tool was evaluated with a variety of artificially inoculated samples of fresh products and ready to eat and cooked dishes, allowing the identification of the target pathogens down to 5 CFU/25 g of food sample. Moreover, the analysis saved a considerable amount of time compared to the ISO standard, being performed in less than 2 working days. Specificity, sensitivity and accuracy were satisfactorily tested by comparison to the standard methods ISO 11290-2:1998 and ISO 6579:2002, suggesting that the tool has a great potential as a reliable alternative for food safety assurance providing rapid detection of both pathogens in food samples.     

Hydraulic characterization of the full scale divertor cassette prototype

In the frame of the activities related to ITER divertor R&D, ENEA C.R. Brasimone was in charge by Fusion For Energy (F4E) to perform the assembly, the hydraulic tests and the theoretical simulation of the hydraulic behavior of the full scale divertor cassette prototype. The objective of these activities was aimed at the investigation of the thermal-hydraulic behavior of the full-scale divertor cassette both under steady state condition and during draining and drying operational transient. In particular, the steady state tests were focused on finally check whether the hydraulic design of the divertor components is able to ensure a uniform and proper cooling for the plasma facing components, with an acceptable pressure drop; whilst the transient ones were aimed at defining proper procedures for draining and drying the divertor cassette as well as for refilling it with water.This paper presents the results of the steady state and transient hydraulic experimental test campaigns performed at ENEA C.R. Brasimone as well as the relevant numerical analysis performed at the Department of Nuclear Engineering of the University of Palermo adopting the RELAP5 Mod3.3 thermal-hydraulic system code.     

BEM analysis of damage progress in 0/90 laminates

The massive use of composites in primary structures of modern commercial aeroplanes is leading to the need for profound knowledge of the mechanisms of damage and failure of heterogeneous materials of this type. This knowledge requires a very fine evaluation of the stress state, which in turn is needed to calculate the parameters of fracture mechanics used to evaluate the integrity or damage tolerance of a particular component. In this paper, the initiation and growth of the damage in a typical [0/90]_S laminate is investigated. Using a BEM code allowing contact between the lips of interfacial cracks appearing in the damaged configuration and based on a former generalized plane strain formulation of the problem developed by the authors, the energy release rate (ERR) is calculated for different configurations corresponding to the different intermediate states that may occur in the process of damage generation. The numerical results obtained clarify some aspects of the progression of the damage and open up the possibility, using comparison with experimental results, of understanding, and consequently improving, the performance of composite materials.     

The Irritant Effects of Pharmaceutically Applied Surfactants

Dermal or transdermal medication may lead to irritant contact dermatitis. However, little information is available on the irritant effect of surfactants which are applied in topical formulations. Our aim was to examine the irritant effect of the most frequent compounds in topical products. A murine model was applied. The following compounds were examined: sodium lauryl sulphate (SLS), polyethoxylated (40EO) hydrogenated castor oil and sucrose laurate. SLS led to severe erythema, increase in transepidermal water loss (TEWL) and induced necrosis and accumulation of neutrophylic granulocytes and lymphocytes. Exposure to sucrose laurate resulted in an elevation of TEWL, but histology did not reveal impairment of the skin structure. Application of polyethoxylated (40EO) hydrogenated castor oil was not accompanied by tissue damage. Special attention should be paid to the irritant effect of SLS. Polyethoxylated (40EO) hydrogenated castor oil seems to be a non-irritant agent and sucrose laurate is also a promising candidate for application in topical preparations.