Prediction of ductile fracture in anisotropic steels for pipeline applications

Large diameter steel pipelines for gas transportation may experience extreme overloads due to external actions such as soil sliding, faults movements, third part interactions. In these scenarios the material undergoes severe plastic strains which locally may reach the fracture limits. Due to the manufacturing process, the steels used in such applications have an anisotropic behavior both for plasticity and fracture. In this paper two steel grades have been characterized in view of anisotropic plastic fracture. Fracture tests have been planned to characterize the fracture behavior under different stress states and in different directions to define the anisotropic sensitivity. Finite element modelling, incorporating an anisotropic plasticity formulation, has been used to calculate the local fracture parameters in the specimens and to define the complete ductile fracture locus. An uncoupled damage evolution law has been finally used to evaluate the fracture limits on real pipelines failed in full scale laboratory tests. The strain to fracture prediction has been verified by local strain measurements on the fractured pipes. The model robustness has been also verified on global parameter predictions, such us the burst pressur

Implementation of a lode angle sensitive yield criterion for numerical modelling of ductile materials in the large strain range

Ductile metallic materials are usually mechanically characterized in the large strain range by means of conventional laboratory tests, namely tensile and torsion test. The identification of the elastic-plastic equivalent stress-strain relation is made by using the widely accepted J2 hypothesis and isotropic behaviour, but results of dedicated tensile and torsion tests on different steel grades showed that it does not seem possible to identify a unique stress-strain curve, as expected on theoretical ground. Curves obtained from dissimilar tests, even though perfectly matching at small plastic strains, start differing significantly from medium strains. Starting from the experimental observations, a general yield surface has been developed based on a well established framework, including beside the J2 invariant also the J3 one. The new yield function has been coded inside a general purpose finite element code by means of dedicated user routines. Implications on the parameters identification and examples of the new yield surface application are discussed in the paper

Podophyllotoxin as a probe for the colchicine binding site of tubulin

The binding of [3H]podophyllotoxin to tubulin, measured by a DEAE-cellulose filter paper method, occurs with an affinity constant of 1.8 x 106 M-1 (37° at pH 6.7). Like colchicine, ~0.8 mol of podophyllotixin are bound per mol of tubulin dimer, and the reaction is entropy-driven (43 cal deg-1 mol-1). At 37° the association rate constant for podophyllotoxin binding is 3.8 x 106 M-1 h-1, ~10 times higher than for colchicine; this is reflected in the activation energies for binding which are 14.7 kcal/mol for podophyllotoxin and 20.3 kcal/mol for colchicine. The dissociation rate constant for the tubulin-podophyllotoxin complex is 1.9 h-1, and the affinity constant calculated from the ratio of the rates is close to that obtained by equilibrium measurements. Podophyllotxin and colchicine are mutually competitive inhibitors. This can be ascribed to the fact that both compounds have a trimethoxyphenyl ring and analogues of either compound with bulky substituents in their trimethoxyphenyl moiety are unable to inhibit the the binding of either of the two ligands. Tropolone, which inhibits colchicine binding competitively, has no effect on the podophyllotoxin/tubulin reaction. Conversely, podophyllotoxin does not influence tropolone binding. Moreover, the tropolone binding site of tubulin does not show the temperature and pH lability of the colchicine and podophyllotoxin domains, hence this lability can be ascribed to the trimethoxyphenyl binding region of tubulin. Since podophyllotoxin analogues with a modified B ring do not bind, it is concluded that both podophyllotoxin and colchicine each have at least two points of attachment to tubulin and that they share one of them, the binding region of the trimethoxyphenyl moiety

The fate of spiral galaxies in clusters: The star formation history of the anemic Virgo cluster galaxy NGC 4569

We present a new method for studying the star formation history of late-type cluster galaxies undergoing gas starvation or a ram pressure stripping event by combining bidimensional multifrequency observations with multizone models of galactic chemical and spectrophotometric evolution. This method is applied to the Virgo Cluster anemic galaxy NGC 4569. We extract radial profiles from recently obtained UV GALEX images at 1530 and 2310 Å, from visible and near-IR narrow (Hα) and broadband images at different wavelengths (u, B, g, V, r, i, z, J, H, and K), from Spitzer IRAC and MIPS images, and from atomic and molecular gas maps. The model in the absence of interaction (characterized by its rotation velocity and spin parameter) is constrained by the unperturbed H-band light profile and by the Hα rotation curve. We can reconstruct the observed total gas radial density profile and the light surface brightness profiles at all wavelengths in a ram pressure stripping scenario by making simple assumptions about the gas removal process and the orbit of NGC 4569 inside the cluster. The observed profiles cannot be reproduced by simply stopping gas infall, thus mimicking starvation. Gas removal is required, which is more efficient in the outer disk, inducing radial quenching in the star formation activity, as observed and reproduced by the model. This observational result, consistent with theoretical predictions that a galaxy cluster-IGM interaction is able to modify structural disk parameters without gravitational perturbations, is discussed in the framework of the origin of lenticular galaxies in cluster

SEeD for Change: The Systemic Event Design Project Applied to Terra Madre Salone del Gusto for the Development of Food Communities

In the contemporary era, food plays a key role in balancing environmental, social, and economic balances, not only due to its primary identity as a resource that nourishes living beings and the planet but also through the processes triggered by stakeholders who act at the internal local food systems. In the latter, an orientation towards sustainability is increasingly urgently required, capable of achieving a widespread creation of shared value. In this scenario, the International Slow Food Association operates, which also, through the Terra Madre Salone del Gusto initiative, coordinates communities and events located throughout the world on the theme of “good, clean and fair” food. This article aims to analyze, through the lens of the systemic approach, the interesting and multifaceted impacts of this event, as an opportunity to disseminate and contagion of ideas, attitudes, and behaviors around the themes of sustainability and biodiversity, but also as a moment of consolidation and creation of relationships between and within local food systems and local communities. The research project presented, entitled “SEeD for Change”, was coordinated by the University of Gastronomic Sciences of Pollenzo with the University of Turin and helped to focus on the actors, relationships and contexts that actually and virtually hosted the event: places in which through a common and shared language, change has been generated

Calibration and prediction assessment of different ductile damage models on Ti6Al4V and 17-4PH additive manufactured alloys

Nowadays, metal additive manufacturing is becoming always more popular, being able to deliver complex shaped high quality products. Though many studies have been conducted on the high cycle fatigue behavior of these materials, yet ductile failure has still not been completely investigated, to identify the failure limits under static complex stress states. In the present study, the calibration of three ductile damage models on two popular additive manufactured alloys was carried out. The selected alloys were Ti6Al4V, processed via Electron Beam Melting, and 17-4PH fabricated with Selective Laser Melting technology; both broadly used in actual industrial applications. For each material a set of samples, was fabricated to perform a thorough static mechanical characterization, involving tensile tests on round smooth bars, notched bars, tests under plane strain conditions and torsion tests. The stress state in the critical points was retrieved relying on FEM simulations, and the data collected via the hybrid experimental-numerical procedure subsequently used to tune the damage models. Specifically, the selected models are the Rice and Tracey, the Modified Mohr-Coulomb by Wierzbicki and the one proposed by Coppola and Cortese. While the former does not take into account the effect of Lode parameter, the latter two consider its influence on fracture onset. A minimization algorithm was used for their calibration, and different optimization strategies were adopted to check the robustness of identified parameters. The resulting strains to fracture as a function of damage parameters were plotted for each formulation. The failure prediction accuracy of all models was assessed and compared to the others

Analysis of the micro-voids fraction in structural steels and its evolution during plastic deformation until failure

In this work the results of an experimental analysis performed on different steels of commercial use having different microstructure and yield value are reported. The materials were characterized by performing tensile and torsion tests, bringing the material up to rupture. The specimens were extracted according to different orientations to verify the influence of anisotropy on the size and distribution of micro-voids present in the broken material. After the mechanical tests, an analysis was made of the amount of micro-voids present in the original, not deformed material and in the deformed material until failure. The results obtained show that for all the analyzed steels the initial fraction of micro-voids is negligible, and no growth or formation of further voids is observed as the applied plastic deformation increases, even for strain values close to rupture

On Gram-positive-and Gram-negative-bacteria-associated canine and feline skin infections: a 4-year retrospective study of the university veterinary microbiology diagnostic laboratory of Naples, Italy

A 4-year retrospective study (2016–2019) of selected routine bacteriological examinations of the veterinary microbiology laboratory of the University Veterinary Teaching Hospital of Naples (Italy) was carried out. A total of 189 bacteriological samples were collected from 171 dogs and 18 cats suffering from skin infections. In dogs, the most common cutaneous infection was otitis externa, while pyoderma was found to be prevalent in cats. The number of recorded Gram-positive strains over the study period did not vary considerably from year to year and was always significantly higher (p-value = 0.0007) in comparison with Gram-negative bacterial isolations. In dogs, Staphylococcus pseudintermedius was the most common identified Gram-positive bacterium (65%), while Pseudomonas aeruginosa (36%) was the one among the isolated Gram-negative bacteria. In cats, coagulase-negative staphylococci were the most predominant isolated bacteria (47%). The phenotypic profiles of antibiotic resistance showed that most of the strains were resistant to amoxicillin–clavulanate, penicillin, clindamycin, and trimethoprim–sulfamethoxazole. Several multi-drug-resistant strains (35%) were detected in canine isolates. An updating of antibiotic resistance profiles of the main Gram-positive and Gram-negative bacteria principally associated with skin infections of pet animals is necessary to improve stewardship programs of veterinary hospitals and clinics

obesity weight loss and heart failure

Background The current scientific data controversially indicate obesity both as a risk factor for developing congestive heart failure (CHF) and a positive prognostic factor. Aims The present study evaluated the impact of weight loss on clinical and instrumental parameters in a selected group of obese patients with CHF. Methods An overall population of 560 HF patients was sub-grouped on the basis of the Body Mass Index (BMI): 8.2% were underweight (BMI 31). Of the 46 overweight and obese patients, 28 (55.2% men, age 51–80 years) accepted a tailored low-caloric dietary program for at least 4 months. The 28 patients belonged to both obese and overweight groups (BMI>27.8) and were in NYHA classes II–III. Mean follow-up was 5 months. Results The mean loss of body weight was 4 kg in 81.4% of patients, versus 3 kg mean increase in whole (560 patients) population (72.5–75.5 kg). In the 28 patients we recorded a significant ( p <0.05) improvement of NYHA class, better control of arterial blood pressure and statistically significant ( p <0.05) lowering of total cholesterol and triglyceride levels. Conclusions Tailored dietetic program may improve clinical and instrumental parameters in patients with CHF

THERMAL AND OPTICAL DATA FUSION SUPPORTING BUILT HERITAGE ANALYSES

Abstract. The recent developments of passive sensors techniques, that have been able to take advantage of the technological innovations related to sensors technical features, sensor calibration, the use of UAV systems (Unmanned Aerial Vehicle), the integration of image matching techniques and SfM (Structure from Motion) algorithms, enable to exploit both thermal and optical data in multi-disciplinary projects. This synergy boost the application of Infrared Thermography (IRT) to new application domains, since the capability to provide thematic information of the analysed objects benefits from the typical advantages of data georeferencing and metric accuracy, being able to compare results investigating different phenomena.This paper presents a research activity in terrestrial and aerial (UAV) applications, aimed at generating photogrammetric products with certified and controlled geometric and thematic accuracy even when the acquisitions of thermal data were not initially designed for the photogrammetric process. The basic principle investigated and pursued is the processing of a photogrammetric block of images, including thermal IR and optical imagery, using the same reference system, which allows the use of co-registration algorithms. Such approach enabled the generation of radiance maps, orthoimagery and 3D models embedding the thermal information of the investigated surfaces, also known as texture mapping; these geospatial dataset are particularly useful in the context of the built Heritage documentation, characterised by complex analyses challenges that a perfect fit for investigations based on interdisciplinary approaches