Fatigue strength of plastics components made in additive manufacturing: first experimental results

Evolution of additive manufacturing (AM) techniques is making these innovative technologies more and more available and known to a larger audience. This allowed components built with AM techniques, especially metallic ones, to be effective in substituting similar components made with traditional technologies; with all the advantages of AM that make these components even more interesting in terms of performance. With plastics this process is relented also due to the chronic lack of established knowledge of the plastic materials, both in terms of strength, design criteria, both in long term behavior but also in static short-term properties. This work tries to give some useful information about the fatigue behavior of one class of material widely used with the mostly widespread AM technique for plastics, that is filament deposition modeling (FDM). The material considered is acrylonitrilebutadiene-styrene (ABS), used in countless components (electronic devices, household appliances, medical tools, and others) due to its excellent mechanical performances and relatively good workability. The property mainly analyzed in this work is fatigue behavior. Fatigue tests were performed in plane bending on specimen very similar to the type proposed and used by Nicoletto (2018) in different manufacturing and loading conditions. The obtained results offer an interesting insight into the properties of small components in ABS made by FDM and the effects of some influencing parameters: different stress-ratios were considered, as well as technological variations such as deposition direction. Experiments reveal that the scatter of fatigue data, even with the manufacturing uncertainties and defects typical of AM, can be controlled and within reasonable limits

An improved model to describe the repeated loading-unloading in compression of cellular materials

Cellular materials, often referred as foams or structural foams when used for energy absorption, are largely used to protect people and goods in the case of shocks and impacts. The detailed knowledge of their behavior is fundamental to design components for this aim. Peroni et al. (2008)-(2009) proposed a model able to describe the mechanical compression behavior of some polymeric material. Such model, based on the work by Rusch (1970), described the stress-strain curve as a sum of two contributions, the first for the elastic part and the second for the densification. More recently Avalle and Belingardi (2018) presented a more general model where the stress is calculated as a sum of three terms, one for the elasto-plastic phase, the second for the plateau, and a third for the densification. The model could include effects like density and strain-rate. However, those models allow to describe only the monotonic compression behavior: in several situations repeated impacts can happen with unloading followed by further reloading. Unfortunately unloading cannot be described by a linear relation between stress and strain (as is usually considered for metals). Unloading follows a non-linear law with a variable relation between stress and strain in the successive cycles: this requires a particularly complex model. In this work, a new model able to effectively reproduce the compression behavior of some polymeric cellular materials is presented. The model is validated and tuned on the basis of experimental tests with specimen subject to complex cycles of repeated loading and unloading. The model describes both the loading from different levels of residual compression and unloading from any value of compression level. The application to several materials justifies the generality of the method

D-mannose: a promising support for acute urinary tract infections in women. A pilot study

Urinary tract infections still represent a significant bother for women and result in high costs to the health system. D-mannose is a simple sugar; it seems able to hinder bacteria adhesion to the urothelium. The present study aimed to determine whether D-mannose alone is effective in treating acute urinary tract infections in women and its possible utility in the management of recurrences

Influence of Start-up Management on the Residual Life of a Large Steam Turbine Shaft

The liberalization of electricity market in Europe led to a growing competition between energy producers, making crucial the ability to optimize the management strategies of power plants. Combined Cycle Power Plants (CCPP) have to operate in a flexible way, with frequent and rapid variations of the power produced, in order to quickly adapt to the frequent changes in load imposed by the demand. Nowadays, they typically operate in cycling mode with daily start-up and shut-down. The components of the plant are subjected to great cyclical variations in temperature, which induce stresses on materials, especially during the start-up phases. The present activity concerns the assessment of life consumption -caused by these operations- on the rotor of the steam turbine of the CCPP (800 MW) inside the Tirreno Power thermal plant located in Vado Ligure, Italy. The aim is to draw a set of curves representing the percent life expended per cycle as a function of rate of steam temperature change and magnitude of the overall temperature increase. These curves are called Cyclic Life Expenditure curves (CLE). In the future, the developed methodology will be used to reduce the start-up times, keeping under control the life consumption of the rotor and optimizing the maneuvers that generate thermal transients

The use of low pressure plasma surface modification for bonded joints to assembly a robotic gripper designed to be additive manufactured

The paper explores how different surface preparations modify the mechanical performance of bonded joints on components made in acrylonitrile butadiene styrene (ABS) processed by fused filament fabrication (FFF) additive manufacturing. Two alternative treatments are considered: surface abrasion compliant to the standard ASTM D2093-03 (17) and using low pressure plasma, an innovative solution. The assessment is performed on standard lap shear test specimens and structural epoxy adhesive. The bonding layer with abraded surfaces shows adhesive failure while after the low-pressure plasma treatment shows adherends failure. As case of study the bonding solution to perform the assembly is considered a jaw finger of a robotic gripper for the picking of garments from a table. The redesign of the finger availing of the performance of bonding with the new plasma treatment is proposed and discussed. Experimental testing assessed the feasibility of this innovative technical solution

Mind wandering in people with Multiple Sclerosis: A psychometric study

Background: Although mind wandering (MW) is associated with various psychological aspects frequently affected in people with Multiple Sclerosis (PwMS), there is lack of validated tools to assess MW in this clinical population.Objective: This psychometric study aimed to assess structural and construct validity and reliability of a brief Italian version of Mind Wandering (MW) Scale that measures two different dimensions of MW, i.e., spontaneous (MW-S) and deliberate (MW-D).Methods: Structural validity of the MW Scale was assessed by explorative factor analysis (EFA). To investigate construct validity, mood (Hospital Anxiety Depression Scale) and personality (10-items Big Five Inventory Test) were correlated with MW constructs. Reliability was assessed by Cronbach's alpha for internal consistency and intraclass correlation coefficients.Results: EFA confirmed two distinct constructs of MW, i.e., MW-S and MW-D, also in PwMS. This tool appropriately fits the graded response model, supporting validity (about 79% of hypotheses for convergent and discriminant constructs confirmed) and internal consistency (MW-S: Cronbach's alpha = 0.84; MW-D: Cronbach's alpha = 0.88).Conclusion: MW Scale could be a useful tool to measure MW also in PwMS. As MW seems to be connected to clinical manifestations of MS, a detailed assessment of MW should be encouraged in clinical practice

P63 modulates the expression of the WDFY2 gene which is implicated in cancer regulation and limb development

TP63 is a member of the TP53 gene family, sharing a common gene structure that produces two groups of mRNAs\u2019 encoding proteins with different N-terminal regions ( 06N and TA isoforms); both transcripts are also subjected to alternative splicing mechanisms at C-terminus, generating a variety of isoforms. p63 is a master regulator of epidermal development and homoeostasis as well as an important player in tumorigenesis and cancer progression with both oncogenic and tumour suppressive roles. A number of studies have aimed at the identification of p63 target genes, allowing the dissection of the molecular pathways orchestrated by the different isoforms. In the present study we investigated in more detail the p63 responsiveness of the WDFY2 (WD repeat and FYVE domain containing 2) gene, encoding for an endosomal protein identified as a binding partner of the PI-3K/AKT signalling pathway. We showed that overexpression of different p63 isoforms was able to induce WDFY2 expression in TP53-null cells. The p63-dependent transcriptional activation was associated with specific response elements (REs) that have been identified by a bioinformatics tool and validated by yeast- and mammal-based assays. Interestingly, to confirm that WDFY2 belongs to the p63 network of cancer regulation, we analysed the impact of WDFY2 alterations, by showing its frequent deletion in different types of tumours and suggesting its expression level as a prognostic biomarker. Lastly, we identified a chromosomal translocation involving the WDFY2 locus in a patient affected by a rare congenital limb anomaly, indicating WDFY2 as a possible susceptibility gene placed downstream p63 in the network of limb development

The Efficacy of Fractional {CO}2 Laser in the Treatment of Genitourinary Syndrome of Menopause. A Large Prospective Observational Study

Background: Genitourinary syndrome of menopause (GSM) majorly caused by the physiological decline in estrogen, affects up to 90% of menopausal women. Hormonal therapy seems to be an effective treatment, often not executable for contraindication or patient's low compliance to local or systemic medical therapy. Fractional CO2 laser therapy is an emerging and effective choice for women affected by vulvo-vaginal atrophy (VVA), promoting collagen regeneration and improving blood flow of the vaginal mucosa and elasticity of tissues. Methods: Ninety-two menopausal Patients affected by vulvo-vaginal atrophy (VVA) were considered for the present prospective observational study. All women were treated with Fractional CO2 laser Lumenis AcuPulse in a fractionated sequential mode laser pulse. Patients were requested to complete questionnaires regarding the Female Sexual Functional Index (FSFI), Female Sexual Distress Scale (FSDS) and severity of Most Bothersome Symptoms (MBS) at baseline (T0) and at three-month following three-treatment-sessions (T1). Results: Data indicated a significant improvement of MBS (vaginal itching (p < 0.0001), post-coital vaginal bleeding (p < 0.002), vaginal dryness (p < 0.0001), dyspareunia (p < 0.0001) and dysuria (p < 0.0001), higher Vaginal Health Index Score (VHIS) (4.1 +/- 1.21; 95% CI = 3.84-4.35) and reduces pH (-0.53 +/- 0.24; 95% CI = 0.48-0.58) after CO2 laser treatment. A significantly improvement of FSFI Total score (p < 0.0001) and FSDS (p < 0.0001) have been demonstrated. Conclusions: Fractional CO2 laser improves vaginal health as well as signs and symptoms associated with GSM, while significantly elevating quality of life and sexual functionality among postmenopausal symptomatic women