Recent developments in multi-parametric three-dimensional stress field representation in plates weakened by cracks and notches

The paper deals with the three-dimensional nature and the multi-parametric representation of the stress field ahead of cracks and notches of different shape. Finite thickness plates are considered, under different loading conditions. Under certain hypotheses, the three-dimensional governing equations of elasticity can be reduced to a system where a bi-harmonic equation and a harmonic equation have to be simultaneously satisfied. The former provides the solution of the corresponding plane notch problem, the latter provides the solution of the corresponding out-of-plane shear notch problem. The analytical frame is applied to some notched and cracked geometries and its degree of accuracy is discussed comparing theoretical results and numerical data from 3D FE models

Notch Stress Intensity Factors Applied to U and V-Shaped Radiused Notches under In-plane Shear Loading

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Brittle failure of inclined key-hole notches in isostatic graphite under in-plane mixed mode loading

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Densità di energia di deformazione locale e resistenza a fatica di giunti saldati di geometria complessa

A recent criterion based on the local strain energy density (SED) averaged over a given control volume is applied to well-documented experimental data taken from the literature, all related to steel welded joints of complex geometry. This small size volume embraces the weld root or the weld toe, both regions being modelled as sharp (zero notch radius) V-notches with different opening angles. The SED is evaluated from three-dimensional finite element models by using a circular sector with a radius equal to 0.28 mm. The data expressed in terms of the local energy fall in a scatter band recently reported in the literature, based on about 650 experimental data related to fillet welded joints made of structural steel with failures occurring at the weld toe or at the weld root

Fracture behaviour of notched round bars made of PMMA subjected to torsion at -60 °C

This paper presents seventy new experimental results from PMMA notched specimens tested under torsion at 60 C. The notch root radius ranges from 0.025 to 7.0 mm. At this temperature the non-linear effects previously observed on specimens of the same material tested at room temperature strongly reduce. The averaged value of the strain energy density over a control volume is used to assess the critical loads to failure. The radius of the control volume and the critical strain energy density are evaluated a priori by using in combination the mode III critical stress intensity factor from cracked-like specimens and the critical stress to failure detected from semicircular notches with a large notch root radiu

Un "osservatore e testimone attento". L'opera di Remo Ceserani nel suo tempo

Il volume studia dal punto di vista storico-critico e teorico l'apporto di Remo Ceserani al dibattito culturale e teorico-letterario non solo italiano

Caratterizzazione a fatica di provini in acciaio C40 soggetti a trazione e torsione combinate, in fase e fuori fase

Il lavoro sintetizza i risultati di una serie di prove di fatica multiassiale su provini intagliati in acciaio C40 normalizzato, soggetti a carichi combinati di trazione e torsione, in fase e fuori fase (?=0 e ?=90°). I test sono stati effettuati con due diversi rapporti nominali di ciclo, R=-1 e R=0, mantenendo costante e pari all’unità il rapporto di biassialità, ?=?a/?a. Gli intagli circonferenziali a V presentavano un raggio di raccordo di 0.5 mm, una profondità di 4 mm e un angolo di apertura di 90 gradi. Ai risultati di fatica multiassiale si aggiungono quelli ottenuti a trazione e torsione pura su provini lisci e intagliati e quelli a sola torsione su di un alberino con spallamento. Per queste serie è sempre stato usato un rapporto nominale pari a –1. Dopo aver presentato le curve di Wöhler per i singoli casi, tutti i dati relativi alle provette intagliate vengono sintetizzati in due curve, la prima basata sulla densità di energia totale di deformazione, all’apice dell’intaglio, la seconda basata sulla densità di energia di deformazione deviatorica

The triaxial ellipsoid dimensions, rotational pole, and bulk density of ESA Rosetta target asteroid (21) Lutetia

We seek the best size estimates of the asteroid (21) Lutetia, the direction of its spin axis, and its bulk density, assuming its shape is well described by a smooth featureless triaxial ellipsoid, and to evaluate the deviations from this assumption. Methods. We derive these quantities from the outlines of the asteroid in 307 images of its resolved apparent disk obtained with adaptive optics (AO) at Keck II and VLT, and combine these with recent mass determinations to estimate a bulk density. Our best triaxial ellipsoid diameters for Lutetia, based on our AO images alone, are a x b x c = 132 x 101 x 93 km, with uncertainties of 4 x 3 x 13 km including estimated systematics, with a rotational pole within 5 deg. of ECJ2000 [long,lat] = [45, -7], or EQJ2000 [RA, DEC] = [44, +9]. The AO model fit itself has internal precisions of 1 x 1 x 8 km, but it is evident, both from this model derived from limited viewing aspects and the radius vector model given in a companion paper, that Lutetia has significant departures from an idealized ellipsoid. In particular, the long axis may be overestimated from the AO images alone by about 10 km. Therefore, we combine the best aspects of the radius vector and ellipsoid model into a hybrid ellipsoid model, as our final result, of 124 +/- 5 x 101 +/- 4 x 93 +/- 13 km that can be used to estimate volumes, sizes, and projected areas. The adopted pole position is within 5 deg. of [long, lat] = [52, -6] or[RA DEC] = [52, +12]. Using two separately determined masses and the volume of our hybrid model, we estimate a density of 3.5 +/- 1.1 or 4.3 +/- 0.8 g cm-3 . From the density evidence alone, we argue that this favors an enstatite-chondrite composition, although other compositions are formally allowed at the extremes (low-porosity CV/CO carbonaceous chondrite or high-porosity metallic). We discuss this in the context of other evidence.Comment: 9 pages, 8 figures, 5 tables, submitted to Astronomy and Astrophysic

COVID-19 and surgical training in Italy: Residents and young consultants perspectives from the battlefield

COVID-19 is seriously affecting Italy, putting the health system under extreme pressure. Training of medical students and residents is also suffering from this with the suspension of lectures and clinical rotations. What solutions have been taken to deal with the issue