MODELLING PLASTIC DEFORMATION OF STAINLESS STEEL PIPES

Plastic deformation is the most common technique adopted to manufacture complex shape pieces in the most efficient way. Even higher requirements need to be faced in the different applications. In order to target such requirement quality and compliance tests are carried out aimed to guarantee that these standards are faced; this often means a waste of material and economic resources. A far as concerns welded stainless steel pipes many criticises affecting the general trend of subsequent machining need to be considered. In this paper the effects of different process parameters and geometrical constrains on austenitic stainless steel pipe forming are studied by Finite Elements Method (FEM) simulations. The model sensitivity to input parameters is reported. The feasibility of the simulated process is evaluated through the use of Forming Limit Diagrams (FLD). </p

effect of thermo mechanical processes on microstructure evolution in austenitic stainless steels

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Analysis of Forming Parameters Involved in Plastic Deformation of 441 Ferritic Stainless Steel Tubes

A welded stainless steel tube is a component used in several industrial applications. Its manufacturing process needs to follow specific requirements based on reference standards. This calls for a predictive analysis able to face some critical issues affecting the forming process. In this paper, a model was adopted taking into account the tube geometrical parameters that was able to describe the deformation process and define the best industrial practices. In this paper, the effect of different process parameters and geometric constraints on ferritic stainless steel pipe deformation is studied by finite element method (FEM) simulations. The model sensitivity to the input parameters is reported in terms of stress and tube thinning. The feasibility of the simulated process is assessed through the comparison of Forming Limit Diagrams. The comparison between the calculated and experimental results proved this approach to be a useful tool in order to predict and properly design industrial deformation processes

Mechanical and Metallurgical Evaluation of 3 Different Nickel-Titanium Rotary Instruments: An In Vitro and In Laboratory Study

An in-depth evaluation of the mechanical and metallurgical properties of NiTi instruments is fundamental to assess their performance and to compare recently introduced instrument with widespread ones. According to this, since there are no data on this topic, the aim of the study was to mechanically and metallurgically evaluate an instrument recently introduced into the market (ZenFlex (ZF)), by comparing it with two well-known instruments with similar characteristics: Vortex Blue (VB) and EdgeSequel Sapphire (EES). According to this, 195 instruments were selected: 65 ZF, 65 VB and 65 EES. Each group was divided in subgroups according to the mechanical tests (i.e., cyclic fatigue resistance, torsional resistance and bending ability; (n = 20)) and the metallurgical test (differential scanning calorimetry (n = 5)). A scanning electron microscopy was performed to verify the causes of fracture after mechanical tests (cyclic fatigue and torsional tests). According to results, VB showed the highest flexibility and cyclic fatigue resistance in comparison to the other instruments, with a statistically significant difference (p &lt; 0.05). Regarding torsional resistance, EES showed the lowest value of torque at fracture, with a statistically significant difference, whilst the comparison between ZF and VB showed no statistically significant difference (p &gt; 0.05). DSC analysis pointed out that VB had the highest austenite start and finish temperatures, followed by ESS and then ZF. ESS sample showed the highest martensite start and finish temperatures followed by VB and ZF. Considering the results, it can be concluded that VB showed the best mechanical performance during static tests in comparison to ESS and ZF. This is fundamentally due to the interaction of parameters such as instrument design and heat-treatments that are able to enhance its mechanical performance

Austenitic stainless steels manufacturing by laser powder bed fusion technique

In this paper we report about the possibility to process stainless steels by laser powder bed fusion (L-PBF) systems. Austenitic stainless steels are analysed showing the possibility to successfully process them, targeting different applications. In particular, it is shown that stainless steels can be successfully processed and their mechanical behaviour allow them to be put in service. Porosities inside manufactured components are extremely low and comparable to conventionally processed materials. Mechanical performances are even higher than standard requirements. Micro surface roughness typical of the as-built material can act as crack initiator, reducing the strength in both quasi-static and dynamic conditions

Analysis of plastic forming parameters in AISI 441 stainless steel

Plastic deformation is the most common technique adopted to manufacture complex shape pieces in the most efficient way. Even higher requirements need to be faced in the different applications. In order to target such requirement quality and compliance tests are carried out aimed to guarantee that these standards are faced. This often means a waste of material and economic resources. A far as concerns welded stainless steel pipes many criticises affecting the general trend of subsequent machining need to be considered. Such critical issues are more evident in the case of ferritic stainless steel with respect to austenitic ones. Therefore, the study of operating and geometric parameters is fundamental in the production process of ferritic stainless-steel tubes, whose use is mainly for the automotive industry. The possibility to simulate by finite element method (FEM) allows to evaluate the effect of geometric parameters and process constraints on plastic deformation tubes capability, thus allowing to properly fit the plastic deformation process to the target shape as a function of the adopted steel

Tissue transglutaminase is involved in the inflammatory processes of active chronic gastritis

Since tissue transglutaminase-2 (TG2) can represent a marker of inflammation for some gastrointestinal (GI) diseases, we aimed to evaluate TG2 and inflammatory markers? mucosal content in gastric antrum biopsies to shed light on the histological and biochemical background of chronic gastritis inflammation. Fifty-one of 78 patients who underwent upper GI endoscopy (UGIE) for dyspeptic symptoms, had a gastric biopsy. The symptom profile was assessed by a GI symptom rating scale (GSRS) score. Thirty-five patients (69%) showed chronic gastritis. TG2, interleukin-6 (IL)-6, IL-8, IL-10, tumor necrosis factor (TNF)-?, lipopolysaccharides (LPS) and toll-like receptor (TLR)-4 were evaluated in serum and the culture medium of gastric biopsies. TG2, IL-8, IL-10, TLR-4 and TNF-? were significantly higher in active chronic gastritis than in the inactive one and were linked to macrophage concentration. IL-6 was significantly lower in the active form of chronic gastritis than in the inactive one and negatively correlated with TG2. Lastly, IL-10 significantly correlated with the macrophage score. TG2 can exert an active role in chronic gastritis pathogenesis by cooperating with different markers of inflammation. It seems that TG2 can represent a possible therapeutic target for modulating inflammation and disease progression

Vaccine hesitancy: An overview on parents' opinions about vaccination and possible reasons of vaccine refusal

Background. Vaccine hesitancy has increased worldwide with a subsequent decreasing of vaccination rates and outbreaks of vaccine-preventable diseases (i.e. measles, poliomyelitis and pertussis) in several developed countries, including Italy. Design and Methods. We conducted a survey to investigate the attitudes of a parents’ sample about vaccinations by the distribution of questionnaires in six lower secondary schools of the Italian city of Messina. Results. Regarding vaccinations carried out on children, the declared vaccination coverage rates ranged widely between good coverage percentages for some vaccinations (Measles-Mumps-Rubella, Diphtheria-Tetanus-Pertussis), and very low coverage rates for others, especially for “new” vaccinations (HPV, meningococcal, pneumococcal). The vaccinations carried out correlated negatively with both parents’ age and their level of education. Moreover, a favourable parents’ opinion was strongly influenced by a favourable opinion of the physician, while an unfavourable parents’ opinion seemed conditioned by a direct or indirect knowledge of people harmed by vaccines. In addition, our data show that parents do not often know or partially know the real composition of the vaccines and the diseases prevented by vaccinations. Conclusions. Data analysis shows that parents are, theoretically, favourable towards vaccinations but have little knowledge of such practices, sometimes not being unaware of the types of vaccines administrated to their children. Health education and communication of correct information are certainly the cornerstones to improve the situation and to fight the widespread and non-grounded fears about vaccines

Antidepressant activity of fingolimod in mice

Recent findings indicate that fingolimod, the first oral drug approved for the treatment of multiple sclerosis (MS), acts as a direct inhibitor of histone deacetylases (HDACs) and enhances the production of brain-derived neurotrophic factor (BDNF) in the CNS. Both mechanisms are relevant to the pathophysiology and treatment of major depression. We examined the antidepressant activity of fingolimod in mice subjected to chronic unpredictable stress (CUS), a model of reactive depression endowed with face and pharmacological validity. Chronic treatment with fingolimod (3\ua0mg\ua0kg(-1), i.p., once a day for 4\ua0weeks) reduced the immobility time in the forced swim test (FST) in a large proportion of CUS mice. This treatment also caused anxiogenic-like effects in the social interaction test without affecting anxiety-like behavior in the elevated plus maze or spatial learning in the water maze. CUS mice showed reduced BDNF levels and enhanced HDAC2 levels in the hippocampus. These changes were reversed by fingolimod exclusively in mice that showed a behavioral response to the drug in the FST. Fingolimod treatment also enhanced H3 histone K14-acetylation and adult neurogenesis in the hippocampus of CUS mice. Fingolimod did not affect most of the parameters we have tested in unstressed control mice. The antidepressant-like activity of fingolimod was confirmed in mice chronically treated with corticosterone. These findings show for the first time that fingolimod exerts antidepressant-like effect acting in a "disease-dependent" manner, and raise the interesting possibility that the drug could relieve depressive symptoms in MS patients independently of its disease-modifying effect on MS