fe analysis of single bolt composite bolted joint by means of a simplified modeling technique

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a novel composite bolted joint element application to a single bolted joint

Abstract Based on an analytical solution of the theoretical reference model of the composite bolted joint undergoing in-plane loads, a modeling technique for this kind of demountable connections is presented. The novel composite bolted joint element substitutes a region of the original model, comprising the bolt and the peripheral area, with a set of radially arranged beams: the cross-section properties are opportunely tailored in order to establish a stiffness equivalence between the theoretical reference model and the presented finite element through the resolution of a system of algebraic equations. The in-plane load condition is considered in this work because of its prevalence in comparison with other ones in many practical applications as the double lap shear joint. Numerical case studies are provided to validate the novel composite bolted joint element comparing FE models of circular plates, featuring a quasi-isotropic lay-up, with an internal rigid core or with the presented FE tool

An original FE modelling of a longitudinal multi-passes seam welding

Abstract Both finite element and analytical methods for simulation of welding are essential to predict residual stress and distortions of welded components. Best FE modelling is obtained by using solid elements for thermo-structural simulation with high computational cost. In this contest, an equivalent modelling of plates based on shell elements is proposed in order to streamline the simulations. The equivalent model is composed of n levels of shell elements, centered on the weld seam, in order to evaluate rotations and translations typical of a multi-pass weld. There are as many levels as the number of the weld passes that compose the seam. The interconnection between the n shell levels is realized by rigid beam elements. The latter ones are connected to shell elements by constraint equations. Solid brick models of the plates are used as a benchmark for the equivalent models in thermal and mechanical simulations. The equivalent modelling is in good agreement with solid results, showing a strong decrease of computational burden, enabling the simulation of large welded models in operative conditions

structural health monitoring algorithm application to a powerboat model impacting on water surface

Abstract In naval field, live monitoring of local strains and displacements in the hull is the basis for dynamic studies such as checking the design limits, sea-keeping tests in smooth and rough seas, fatigue life estimation and damage detection. Vessels sailing on water are subject to impulsive loadings and local deformations; in these conditions the damage detection in real time becomes crucial. In this paper, a numerical methodology is proposed to measure the deformation of the whole structure of a powerboat entering the water free surface starting from local strain measurements, obtained numerically in a FE simulation. A modal decomposition approach has been used to reconstruct the structural response of the whole boat body. The reconstruction algorithm is calibrated for this study by means of the normalized modal strains matrix obtained through a FEA. A transient FE analysis is implemented to generate local strain signals from virtual sensors. In this analysis hydrodynamic loading resulting from well-known models are applied. The positioning and number of the virtual reference and control sensors are investigated. Virtual control sensors are utilized to compare strains with respect to the reconstructed quantities. Subsequently, the structural health monitoring algorithm has been applied to the powerboat model with a localized damage on the structure. The results reported in the paper reveal the capability of the method to detect the damage in real time

Design, analysis and optimization of anisogrid composite lattice conical shells

A methodology for structural analysis and optimal design of conical anisogrid composite lattice shell structures subject to different external loads concurrently applied and multiple stiffness constraints is presented. The critical buckling load of the anisogrid lattice conical structure is exactly assessed, independently of the buckling failure mode, by means of a discrete approach. The method makes use of a full FE parametric modeling technique able to manage all the geometrical parameters of the anisogrid composite lattice structure. Additionally, the genetic algorithm NSGA-II is employed to set up an optimization procedure which allows to analyze different sets of geometrical variables, both continuous and discrete, to reach the optimal solution in terms of mass amount and fulfilling of structural and stiffness requirements, aiming at the preliminary design of an actual structure. Numerical case-studies are outlined in order to demonstrate the practical usefulness and versatility of the proposed procedure to industrial cases where the anisogrid lattice conical structure undergoes multiple external loads and various stiffness constraints must be satisfied

Analysis of Scat for Gut Microbiome Identification in Wolves from a Mediterranean and an Alpine Area

The gut microbiome can play a fundamental role in several processes associated with an organism’s ecology, and research on the microbiota of wild animals has flourished in the last decades. Microbiome composition can vary across and within species according to taxonomy and environmental variability, including the availability of food resources. Species with a large distribution may exhibit spatial patterns acting at local/regional scales. We considered one of the most widespread and ecologically important predators in the world, i.e., the grey wolf Canis lupus, for which microbiome data is unduly limited. We studied four packs in different ecological conditions in Italy—two packs from a Mediterranean coastal area and two packs from an Alpine range—using an amplicon sequencing barcoding approach. Overall, our results are consistent with food habits entailing a diet largely based on wild prey and agree with findings obtained on other species of canids. If confirmed through a larger sample, they would support the hypothesis of an influence of the shared evolutionary history across canids on the composition of the gut microbiome. Some emerging differences were observed among packs in terms of species composition (Jaccard) and diversity, providing partial support to recent indications on pack identity as a significant determinant of microbiome composition. These results should be considered preliminary results of gut microbiome composition in our study areas

Totally laparoscopic approach for treatment of early and advanced gastric cancer

[No abstract available

Thermomechanical Analysis of a PFC Integrating W Lattice Armour in Response to Different Plasma Scenarios Predicted in the EU-DEMO Tokamak

Despite the high performance exhibited by tungsten (W), no material would be able to withstand the huge loads expected with extreme plasma transients in EU-DEMO and future reactors, where the installation of sacrificial first wall limiters is essential to prevent excessive wall degradation. The integration of W lattices in the architecture of such components can allow for meeting their conflictual requirements: indeed, they must ensure the effective exhaust of the nominal thermal load during stationary operation; when transients occur, they must thermally insulate and decouple the surface from the heat sink, promoting prompt vapour shielding formation. Starting from the optimised layouts highlighted in a previous study, in this work, a detailed 3D finite element model was developed to analyse in depth the influence of the actual features of the latticed metamaterial on the overall performance of the EU-DEMO limiter PFC on the basis of a flat tile configuration. Its main goal is to help in identifying the most promising layout as a preconceptual design for the fabrication of a small-scale mock-up. For this purpose, the complex geometry of a W-based lattice armour was faithfully reproduced in the model and analysed. This allowed for a detailed assessment of the thermally induced stresses that develop in the component because of the temperature field in response to a number of plasma scenarios—above all, normal operation and ramp down. Structural integrity was verified through the acceptance criteria established for ITER. The two optimised layouts proposed for the PFC were able to effectively meet the requirements under normal reactor operating conditions, while they missed some requirements in the ramp-down case. However, the first HHF tests will be performed in order to benchmark the analyses