720 research outputs found

    Capillaroscopy in 2016 : new perspectives in systemic sclerosis

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    Systemic sclerosis (SSc) is an autoimmune disorder of unknown etiology characterized by early impairment of the microvascular system. Nailfold microangiopathy and decreased peripheral blood perfusion are typical clinical aspects of SSc. The best method to evaluate vascular injury is nailfold videocapillaroscopy, which detects peripheral capillary morphology, and classifies and scores the abnormalities into different patterns of microangiopathy. Microangiopathy appears to be the best evaluable predictor of the disease development and has been observed to precede the other symptoms by many years. Peripheral blood perfusion is also impaired in SSc, and there are different methods to assess it: laser Doppler and laser speckle techniques, thermography and other emerging techniques

    An experimental-numerical methodology for the nondestructive assessment of the dynamic elastic properties of adhesives

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    In the last years, lightweight design has become a priority in many industrial sectors, like as the aerospace and the automotive industry, mainly due to the strict regulations in terms of gas emission and pollution. Together with lightweight materials, the use of adhesives to join different parts permits to significantly reduce the weight of mechanical assemblies. For a proper design of the joints, the mechanical properties of adhesives should be correctly experimentally assessed. However, the experimental assessment of the adhesive mechanical properties can be complex, since they can be hardly estimated from traditional experimental tests on lap joint or butt-joint specimens. The development of an experimental procedure for the assessment of the adhesive properties is therefore of interest. In the present paper, a methodology for the assessment of the dynamic elastic properties of adhesives, i.e., Young's modulus and the loss factor, is proposed. The procedure is based on the Impulse Excitation Technique and Finite Element Analyses (FEA). An automated routine has been written to assess the elastic properties by minimizing the difference between the frequency response obtained experimentally and through FEA. The proposed methodology has been experimentally validated to estimate the mechanical properties of an epoxy adhesive for automotive applications

    Blunt notch effect on the fatigue response up to 10^9 cycles of selective laser melting Ti6Al4V specimens

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    In this paper, the influence of a blunt notch on the VHCF response of SLM Ti6Al4V specimens is investigated. Ultrasonic fully reversed tension-compression tests up to 10(9) cycles were carried out on unnotched specimens and specimens with a blunt notch. Unnotched specimens show a slightly larger fatigue response, with limited differences. All fatigue failures originated from defects, which are bigger in unnotched specimens, mainly due to the different risk volume of the tested specimens and the related size effect. Interactions between notch, stress gradient, and defect size distribution must be considered to properly assess the influence of notch on the VHCF response

    Comparison between Fractal and Statistical Approaches to Model Size Effects in VHCF

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    Size effects concern the anomalous scaling of relevant mechanical properties of materials and structures over a sufficiently wide dimensional range. In the last few years, thanks to technological advances, such effects have been experimentally detected also in the very high cycle fatigue (VHCF) tests. Research groups at Politecnico di Torino are very active in this field, observing size effects on fatigue strength, fatigue life and fatigue limit up to the VHCF regime for different metal alloys. In addition, different theoretical models have been put forward to explain these effects. In the present paper, two of them are introduced, respectively based on fractal geometry and statistical concepts. Furthermore, a comparison between the models and experimental results is provided. Both models are able to predict the decrement in the fatigue life and in the conventional fatigue limit

    Intersections of self-gravitating charged shells in a Reissner-Nordstrom field

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    We describe the equation of motion of two charged spherical shells with tangential pressure in the field of a central Reissner-Nordstrom (RN) source. We solve the problem of determining the motion of the two shells \textsl{after} the intersection by solving the related Einstein-Maxwell equations and by requiring a physical continuity condition on the shells velocities. We consider also four applications: post-Newtonian and ultra-relativistic approximations, a test-shell case, and the ejection mechanism of one shell. This work is a direct generalization of Barkov-Belinski-Bisnovati-Kogan paper.Comment: 21 pages, 1 figure;v3 added reference
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