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Structural strengthening with FRPs is widely used in many engineering applications. In the field of Civil Engineering, composites are commonly bonded to extrados or intrados of beams. However, the application of this technique to constructions requires the satisfaction of a large number of requirements especially about the adhesive joining durabili ty and reliability. Thus, a proper description of mechanical behavior of the reinforcement interface and the prediction of debonding failure is necessary in order to realize a correct design phase of adhesively bonded structures. Within structural rehabilit ation with external bonded FRP systems, the debonding failure mode generall y occurs, due to dominant mode II fracture . In this work, mode II fracture behavior of concrete specimens, reinforced with pultruded FRP, has been experimentally investigated by the authors. Shear tests have been performed at the Structural Engineering Testing Hall of the University of Salerno by using both tradi tional equipment and non contact (Digital Image Correlation) technique. Starting from the experimental data, the experimental evaluati on of the J-integral and of specimens' fracture toughness has been performed. Subsequently, by means of theoretical approach proposed by Rice, a cohesive law was associated to the J-integral and thus identified by comparison with experimental data. The proposed CZ model can be adopted in a Finite Element code for simulating the debonding phase in complex structures.

The numerical simulation of rocket engine thrust chambers is very challenging as several damaging phenomena, such as plasticity, low-cycle-fatigue (LCF) and creep occur during its service life. The possibility of simulating the thermostructural behavior of the engine, by means of non-linear finite element analyses, allows the engineers to guarantee the structural safety of the structure. This document reports the numerical simulations developed with the aim of predicting the thermostructural behaviour and the service life of the thrust chamber of a liquid-propellant rocket engine. The work represents a step ahead of previous researches by the authors, with particular reference to the addition of the Smith-Watson-Topper (SWT) fatigue criterion, and to the implementation of a sub-modelling technique, for a more accurate assessment of the most critical section of the component. It was found that the equivalent plastic strains in the most critical nodes obtained through the sub-modelling technique were about 20% lower than those calculated without sub-modelling. Consistently with experimental tests from literature conducted on similar geometries, the most critical areas resulted to be on the internal surface of the chamber. The analyses demonstrated that the LCF damaging contribution was significant, with a life prediction for the thrust chamber of about 3400 cycles.

The paper deals with a FEM-DBEM hybrid methodology applied to crack propagation simulations. The method allows to simulate cracks propagation by means of Finite Element Method (FEM) and Dual Boundary Element Method (DBEM), coupled in a procedure that optimise computational effort and accuracy. FEM is used for stress evaluation of the uncracked domain, whereas, the fracture analysis on a submodel embedding the cracked zone is demanded to DBEM. In particular, a DBEM submodel is extracted from the FEM model, a crack is introduced and traction boundary conditions are transferred from global FEM analysis to the crack surfaces of DBEM submodel (this will result the only needed boundary conditions to work out the DBEM analysis). The aforementioned tractions are those corresponding to the stresses calculated by a FEM global analysis along the virtual path traced by the DBEM advancing crack; consequently, a continuous exchange of data between FEM and DBEM environments is needed during the step by step crack propagation simulation. The proposed case study is based on a shaft/hub coupling undergoing three different loading conditions: combined “bending” and “press-fit”, “shear” and “torque”. The material is a common steel with isotropic mechanical properties, whose Paris’ parameters are calibrated at room temperature. J-integral and Minimum Strain Energy Density (MSED) methods are chosen for Stress Intensity Factors (SIFs) and crack path assessment respectively. A sound agreement is shown among SIFs calculated with the proposed Loaded Crack (LC) method and those evaluated by a “classical” FEM-DBEM approach, where displacement or traction boundary conditions, again retrieved from a FEM analysis of the uncracked global model, are applied on all DBEM submodel cut surfaces.

Hybrid mechanical joints are achieved by the simultaneous use of multiple connection mechanisms such as bolting and bonding. This technique allows to obtain advantages in terms of mechanical properties compared to simple joints such as longer fatigue life and operability in critical environmental conditions. Many parameters influence the structural behavior of the hybrid junctions in this perspective numerical simulation can play a decisive role to the cause. Using hybrid joints allows generally to obtain a more homogeneous stress distribution than bolted ones which is why, over the years, such type of joint is widely used in the automotive and naval industries as well as in the avionics, with particular reference to the residual strength in partially damaged components. In the present work, a numerical model representative of tensile tests on single lap joints characterized by adherends of different nature is presented.

Amorphous polymers, such as epoxy resins, are commonly used in the realization of adhesively bonded joints. In this paper an evaluation of mode I fracture toughness of bonded joints is presented. Moreover, an identification of cohesive zone model parameters via Rice's J-integral is described. Experimental tests are performed on double cantilever beam specimens and relative displacements between adherends are acquired by using the digital image correlation technique. The obtained interface law can be implemented in a finite element code for simulating the decohesion process of complex bonded structures.

By regulating the neocortical excitability, nicotinic acetylcholine receptors (nAChRs) control vigilance and cognition and are implicated in epileptogenesis. Modulation of gamma-aminobutyric acid (GABA) release often accompanies these processes. We studied how nAChRs regulate GABAergic transmission in the murine neocortex with immunocytochemical and patch-clamp methods. The cholinergic fibers densely innervated the somatosensory, visual, motor, and prefrontal cortices (PFC). Laminar distribution was broadly homogeneous, especially in the PFC. The cholinergic terminals were often adjacent to the soma and dendrites of GABAergic interneurons, but well-differentiated synapses were rare. Tonically applied nicotine (1-100 microM) increased the frequency of spontaneous GABAergic inhibitory postsynaptic currents (IPSCs) on pyramidal neurons in PFC layer V. The contribution of nAChR types was assessed by using 1 microM dihydro-beta-erythroidine (DHbetaE), to block heteromeric nAChRs, and 10 nM methyllycaconitine (MLA), to block homomeric nAChRs. Both inhibitors antagonized the effect of nicotine on IPSCs, suggesting that mixed nAChR types control pyramidal neuron inhibition in layer V. To determine whether nAChRs are expressed on basket cells' terminals, we studied miniature IPSCs (mIPSCs). These were revealed using 0.5 microM tetrodotoxin and 50 microM Cd(2+) to isolate the GABAergic terminals from the action potential drive. The nicotinic stimulation of mIPSCs was antagonized by DHbetaE, but not MLA, indicating that heteromeric nAChRs prevail in GABAergic terminals. Immunocytochemistry confirmed the expression of nAChRs on basket cells' somata and terminals. Finally, when the ionotropic glutamatergic transmission was blocked, nicotine partially inhibited the IPSCs, an effect counteracted by both DHbetaE and MLA. Therefore, a fraction of nAChRs are capable of activating GABAergic interneurons that in turn inhibit other GABAergic interneurons, thereby reducing the IPSCs. We conclude that heteromeric nAChRs control GABA release presynaptically, whereas mixed nAChRs regulate both excitation and inhibition of interneurons, the balance depending on the overall glutamatergic drive.

The 'NAFASSY' (NAtional FAcility for Superconducting SYstems) facility is designed to test wound conductor samples under high-field conditions at variable temperatures. Due to its unique features, it is reasonable to assume that in the near future NAFASSY will have a preeminent role at the international level in the qualification of long coiled cables in operative conditions. The magnetic system consists of a large warm bore background solenoid, made up of three series-connected grading sections obtained by winding three different Nb3Sn Cable-in-Conduit Conductors. Thanks to the financial support of the Italian Ministry for University and Research the low-field coil is currently under production. The design has been properly modified to allow the system to operate also as a stand-alone facility, with an inner bore diameter of 1144 mm. This magnet is able to provide about 7 T on its axis and about 8 T close to the insert inner radius, giving the possibility of performing a test relevant for large-sized NbTi or medium-field Nb3Sn conductors. The detailed design of the 8 T magnet, including the electro-magnetic, structural and thermo-hydraulic analysis, is here reported, as well as the production status. © 2015 IOP Publishing Ltd.

Idiopathic Pulmonary Fibrosis/Usual Interstitial Pneumonia (IPF/UIP) represents the most important interstitial pneumonia. A Th2 cytokine pathway predominance, favouring collagen deposition, associated to a deficit in IFN-γ network, seems to be involved in the pathogenesis of this disease. Nonetheless, few data are available about the potentially involved cells. Natural killer cells (NK), are one of the most important subsets implicated in the IFN-γ network. The aim of this study was to assess NK cells, both in BAL and peripheral blood of 11 patients suffering from IPF (group A) with respect to 11 patients with other interstitial pneumonia (Group B). Our results did not show any statistically significant difference in NK percentage in BAL between group A and B. On the contrary, patients with IPF showed a higher percentage of NK cells (t = 2.41; p < .05) and absolute number of cells (t = 2.32; p < 0.05) in peripheral blood, as well as a strong positive correlation between circulating and BAL NK cells (r = .69; p