On the significance of diffuse crack width self-evolution in the phase-field model for residually stressed brittle materials

The Phase-Field method is an attractive numerical technique to simulate fracture propagation in materials relying on Finite Element Method. Its peculiar diffuse representation of cracks makes it suitable for a myriad of problems, especially those involving multiple physics and complex-shaped crack patterns. Recent literature provided linear relationships between the width of the diffuse crack and the material intrinsic fracture toughness, through a material characteristic length. However, lately, it was shown how the existence of a residual stress field can affect the represented crack width even for fully homogeneous materials, in terms of toughness. In this short note, the authors tried to shed some light on the factors influencing the width of the diffuse crack representation. By simulating crack propagation in several residually stressed brittle materials, it was shown how the width of the diffuse crack is affected by the ratio between the driving force - due to the externally applied load - and the driving force required to propagate the crack. In other words, the diffuse crack extent can be linked to the degree of crack propagation stability/instability. Monitoring the evolution of the studied quantity can be of great interest to rapidly assess crack instability circumstances, under displacement control

Strain-controlled fatigue loading of an additively manufactured AISI 316L steel: Cyclic plasticity model and strain–life curve with a comparison to the wrought material

Low cycle fatigue (LCF) regime was experimentally studied for a 316L steel additively manufactured by laser-powder bed fusion (L-PBF), a material widely used in sectors that require a reliable durability analysis. Material cyclic elastoplastic behavior is described by the Chaboche–Voce combined plasticity model, which displayed a great degree of accuracy. The fatigue life was modeled by both invoking the Manson–Coffin curve and other simplified models derived from static properties of the material; some of which showed remarkably good accuracy. A quantitative comparison with a wrought-processed 316L steel displayed a markedly different cyclic elastoplastic response but comparable fatigue strengths

Cyclic plasticity and low cycle fatigue of an aisi 316l stainless steel: Experimental evaluation of material parameters for durability design

AISI 316L stainless steels are widely employed in applications where durability is crucial. For this reason, an accurate prediction of its behaviour is of paramount importance. In this work, the spotlight is on the cyclic response and low-cycle fatigue performance of this material, at room temperature. Particularly, the first aim of this work is to experimentally test this material and use the results as input to calibrate the parameters involved in a kinematic and isotropic nonlinear plasticity model (Chaboche and Voce). This procedure is conducted through a newly developed calibration procedure to minimise the parameter estimates errors. Experimental data are eventually used also to estimate the strain–life curve, namely the Manson–Coffin curve representing the 50% failure probability and, afterwards, the design strain–life curves (at 5% failure probability) obtained by four statistical methods (i.e., deterministic, “Equivalent Prediction Interval”, univariate tolerance interval, Owen’s tolerance interval for regression). Besides the characterisation of the AISI 316L stainless steel, the statistical methodology presented in this work appears to be an efficient tool for engineers dealing with durability problems as it allows one to select fatigue strength curves at various failure probabilities depending on the sought safety level

How difficult is to raise money in turbulent times?

This book features contributions from leading researchers into the effect of the recent financial crisis on lending in the banking sector. They explore the emergence of alternative methods of firm financing, including crowdfunding, firm network financing and venture capital, and analyse the performance of listed European innovative firms. The book discusses related topics such as the role of loan dynamics and structure for Central and Eastern European economic growth, the liquidity policy of the European Central Bank during the Euro crisis, sovereign pensions and social security reserve funds. Lending, Investments and the Financial Crisis addresses the ways in which the strategies of institutional investors have been impacted by the crisis. The study focuses on Western, Central and Eastern Europe, while providing a wider context in terms of comparison with the Chinese banking system

Valutazione dell'attenzione selettiva in pazienti con sclerosi laterale amiotrofica mediante "eye tracking system"

Il grave deficit motorio impedisce in p. con SLA in fase avanzata, la somministrazione di test neuropsicologici carta e penna. Si presenta un sistema computerizzato alternativ

Low cycle fatigue behaviour of cellular materials: Experimental comparative study of strut-based and gyroid structures made of additively manufactured 316L steel

Cellular materials are an attractive option to improve mechanical properties in lightweight design. Given their complex geometry, cellular materials present small features at the meso-scale that make them highly susceptible to fatigue failures. Fatigue of these materials has been receiving adequate attention only in the last few years, nevertheless, studies of low cycle fatigue (LCF) behaviour are extremely scarce and fragmented. In this study, 316L steel strut-based (FBCCZ) and gyroid cellular specimens were successfully manufactured by laser-powder bed fusion and tested in the LCF regime, considering their post-manufacturing morphological characteristics. The cyclic elastoplastic response revealed a higher stiffness for the strut-based than the gyroid cellular structure. The latter, in contrast, exhibited higher fatigue strength in strain-control mode, thanks to the absence of severe stress and strain raisers when compared to the strut-based counterpart. Overall, strain-life curves of both types of cellular materials are shifted to lower number of cycles to failure with respect to the base material. Detailed fractographic analyses revealed complex and tri-dimensional fracture surfaces for the gyroid specimens, whereas the strut-based lattice displayed planar fracture surfaces

Studio Multicentrico prospettico osserva zionale sui sintomi muscolo scheletrici all\u2019esordio in oncologia pediatrica e i fattori predittivi nella diagnosi differenziale con l\u2019atrite idiopatica giovanile. Analisi preliminare.

Studio prospettico di confronto tra i sintomi d'esordio di leucemia acuta e tumore e malattie reumatich