1,721,058 research outputs found
Effetti Della Corrosione Sulle Proprietà Meccaniche Di Sinterizzati In Acciaio Inossidabile
No full textQuesto lavoro si propone di analizzare gli effetti di un ambiente corrosivo su campioni in acciaio inossidabile 316L sinterizzato. In particolare, si è analizzata la relazione esistente tra resistenza alla corrosione e peso, densità e proprietà meccaniche a trazione. Sono stati studiati tre gruppi di acciaio inossidabile 316L sinterizzato, diversi tra loro per potenza laser e per velocità di scansione. Per ogni gruppo sono stati preparati 9 provini e su tutti sono state eseguite misure sia di peso che di densità. Un provino per ogni gruppo è stato testato a trazione senza aver subito alcun trattamento corrosivo, i restanti 8 esemplari di ogni gruppo sono stati sottoposti ad atmosfera con soluzione salina neutra (NSS) per valutare la resistenza alla corrosione del materiale oggetto di studio. Sono stati definiti quattro diversi periodi di esposizione selezionati tra quelli previsti nella normativa di riferimento. Alla fine di ogni periodo di esposizione, due provini per gruppo sono stati rimossi dalla camera di corrosione e analizzati al fine di studiare e registrare tutte le modifiche subiteThis paper aims to analyze the effects of a corrosive atmosphere on sintered stainless steel (316L) samples. In particular, the relationship between resistance to corrosion and weight, density and tensile mechanical properties were investigated. Three groups of sintered stainless steel (316L) were studied, each of them characterized by laser power and scanning speed. For each group 9 specimens were prepared. For all of them, measurements of both weight and density were performed. One specimen for each group was tested, as received, for tensile mechanical test; the remaining 8 specimens of each group were subjected to a neutral salt spray (NSS) to evaluate the corrosion resistance of the studied material. Four different exposure periods were selected from the standard. At the end of each exposure period, two specimens per group were removed from the corrosion chamber and analyzed in order to study and record all the changes that were made
Effect of ElectroSpark process parameters on the WE43 magnesium alloy deposition quality
No full textThis research aims to investigate the effects of process parameters on the quality of WE43 coatings deposited on homologue substrate by ElectroSpark Deposition (ESD) technology. ESD is new technology used to apply coatings or for the restoration and refurbishment of worn or damaged high valued parts. The depositions were processed using five different levels of Energy input (Es, Spark Energy). The microstructure of both the base material and deposits cross-section were characterized by optical and scanning electron microscopies. Also, X-ray diffraction technique was used. In addition, stereological studies of the through-thickness heterogeneities of the deposits (e.g., voids) were performed. The mechanical properties were evaluated by Vickers micro-hardness. The results show that the deposits exhibited a fine grained microstructure due to the rapid solidification. The average micro-hardness values of the deposits are lower than that of the substrate and distributed in a small range (49-60 HV). The lower hardness of the deposits respect to the base material is due to the presence of defectiveness such as spherical, laminar and random shaped voids. The defects area percentage inside the deposits remains well below than 11%. All the deposits were mainly affected by laminar morphology defects. The results indicate that the deposits defectiveness decreases as the energy input increases
Acoustic Emission Analysis On CFRP Laminates Subjected To Open Hole Testing
No full textCarbon Fiber Reinforced Plastic materials (CFRP) are widely used for aeronautical and aerospace applications since they offer high specific mechanical properties. However, their damaged behavior is quite concerning and, if these damages are not visible on the surface their use could become deeply dangerous if not properly monitored. It is therefore essential to detect, evaluate and analyze the several types of propagation of damage caused by static, cyclic and environmental effects. Acoustic Emission technique (AE) is an innovative practice that is providing good results in detecting and identifying CFRP damages. In this paper, the AE technique was applied to CFRP specimens subjected to open hole testing
Superficial Stress Reduction By Laser Annealing: Preliminary Study
No full textMost of the manufacturing processes introduce a locked-in stress state in the material that can have strong effect on the lifetime of the component. The presence of residual stress must be conveniently taken into account during the design process and minimized when possible. Thermal processing of the component is also possible in order to relax residual stress. If a proper thermal cycle is designed for the specific material it can be possible to reduce and even eliminate the state of stress. In this paper we explored an alternative approach to obtain stress relaxation based upon the focusing on the surface of an Al 5068 aluminium alloy of a high power diode laser (HPDL) source. In this way it is possible to obtain a localized effect of stress relaxation limited to the neighbourhood of the area irradiated by the laser beam. Final results, however, depend upon several factors, such as the adopted wavelength, the reflectivity of the material at that specific wavelength, the power of the HPDL source, the mode distribution and the duration of the irradiation. In this work temperature field distributions are calculated for the case of interaction with a point source, a Gaussian source and a double-Gaussian source. For these two, in particular, the influence of the HPDL power was studied. Results obtained by the double-Gaussian distribution analysis were used to set the proper experimental parameter for the experimental study. Finally, repeated annealing cycles were performed and the sample and the obtained stress reduction was evaluated by X-Ray diffraction
Studio dell’insorgenza di fenomeni corrosivi in campioni di bronzo mediante tecnica di proiezione di frange,
No full textMechanical Comparison Of New Composite Materials For Aerospace Applications
Full text linkComposite materials are becoming the most useful material for aircraft structures. Their main advantage is connected to the possibility of deeply reducing weight and costs by maintaining high performances in terms of strength and security. The second major advantage in using this them depends on the possibility they could be proper designed to guarantee services they are made to. Many ways to combine them lead to the necessity of planning experimental tests in order to evaluate the real both elastic and plastic mechanical properties and to compare their variability as function of the fiber type, matrix type and manufacturing technology involved for realizing them. In this paper, a comparison between two innovative Carbon Fiber Reinforced Plastic materials was done. They differ, one from each other, for the matrix type (PEEK and BENZOXAZINE) and for the manufacturing process used to assemble the matrix with the reinforcement (Compression Molding and Resin Transfer Molding). On the other hand, the resin percentage weight content of both materials is maintained constant for all the tests: it is 42% for PEEK matrix and 64% for BENZOXAZINE matrix. The aim of the work is to critically analyze the results in order to get useful information for choosing the best one intended for designing and making the back section of fuselage of a regional aircraft. The component will consist of a front portion with structural aims (zoom phase) and a back part able to withstand to elevated temperatures
Analisi Delle Forme D’onda Associate Ad Emissioni Acustiche In Provini In CFRP Sottoposti A Test Di Delaminazione Modo I
No full textStatic and Fatigue Characterization of Titanium Alloy Welded Joints
No full textTitanium and its alloys presents an elevated strength/weight ratio, good mechanical properties at high temperatures, elevated resistance to corrosion and to most part of acid attacks. These characteristics, thanks to recent improvements in welding techniques that allow the realization of high quality welded joints, makes this material attractive for numerous applications. Naval industry, for which the corrosion constitutes a discriminating element in the choice of materials, is studying new applications for the titanium. Fatigue strength of titanium alloys is the most important information needed for naval structural applications, but none official standard similar to Eurocode exists and data available in literature are still not sufficient for a reliable fatigue design. This work is focused on the study of static and fatigue behavior of butt welded joints in titanium grade 2 and grade 5, all obtained by laser welding technique. The experimental results of fatigue tests are presented both in terms of nominal stress amplitude σa and local strain amplitude εa
The influence of stitching and unconventional fibres orientation on the tensile properties of CFRP laminates
No full textIn the typical structures of carbon-fibre-reinforced plastics (CFRP), multiple layers are stacked together with a particular sequence in order to give specific mechanical characteristics. Layers are organized with different angles, different sequences and different technological processes to obtain innovative materials. This paper introduces a new parameter, able to improve mechanical properties of composites. It analyses an unconventional fibres orientation combined with the through-the-thickness stitching on the in-plane mechanical properties of CFRP. Conventional carbon fibres orientation is generally referred to a Cartesian coordinate system, in which fibres are arranging in bundles along different angle orientations respect to the zero lamina. In this paper a polar coordinate system of continue carbon tow is introduced to create specimens as well as complex geometry components in an easy way. Five different configurations are studied: two are classified as traditional composites (unstitched and Cartesian orientation of woven carbon cloth), three are defined as innovative composites (stitched laminates and continue carbon tow organized in polar or Cartesian system). The application of this technique aims to introduce some advantages in the material's manufacturing process and if compared with the conventional strategy seems to be very promising since it appears to be very efficient in stopping delamination phenomenon
Espi analysis of thermo-mechanical behavior of electronic components
No full textThermo-mechanical aspects must be conveniently taken into account when designing electronic components and devices. Reliability issues can in fact arise due to stress induced by thermal field acting on materials with different coefficients of thermal expansion. In this paper an optical system based upon Phase Shifting Electronic Speckle Interferometry (PS-ESPI) was developed; it allows analyzing the in-plane displacement map experienced by the tested component during its working operation as a consequence of the Joule’s effect. The adoption of an optical technique allowed to get the measurement without contact with the component that is to say without altering the capability of thermal dissipation of the component. The system was demonstrated to be effective in analyzing asymmetries in the displacements along the component and in evaluating how different kinds of constraints can drastically affect the thermo-mechanical behavior of a given component. Furthermore the system was used to compare the thermo-mechanical response of the same component in presence or in absence of a critical defect. It was verified the ability of the set up designed to detect the very different thermomechanical response of a damaged electronic component with respect to an undamaged one
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