Browsing by Author "Silveira, E."
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Item Failure analysis of a set of compressor blades(2008-09) Silveira, E.; Atxaga, G.; Irisarri, A. M.; Caracterización y Validación. Materiales; EXTREMAT; Tecnalia Research & InnovationThis paper analyses the root causes of the failure of a set of blades belonging to the high pressure compressor of an aircraft engine. All these blades were manufactured using a 718 nickel base alloy. The performed study consisted in a fractographic analysis by scanning electron microscopy and a microstructural study using both scanning and optical microscopy. Phases which were present in the fracture surfaces were identified by means of X-ray energy dispersive spectrometry. As a result of this labour the failure was attributed to the impact of sand and stones; that is the so-called foreign object damage mechanism.Item Failure analysis of two sets of aircraft blades(2008) Silveira, E.; Atxaga, G.; Irisarri, A. M.; Caracterización y Validación. Materiales; EXTREMAT; Tecnalia Research & InnovationThis paper analyses the failure of two blades, coming from different aircraft engines. The first one corresponds to the high pressure compressor manufactured in a 718 nickel base superalloy. The failure analysis carried out on this blade points towards foreign object damage (FOD). The second set belongs to the high pressure turbine of another engine. Scanning electron microscopy attributes the first fail to the premature failure by a thermo-mechanical fatigue mechanism of one blade with an inadequate microstructure. The remaining blades of this set, which possess a correct microstructure, failed due to the impacts of the debris generated by the fracture of the first one.Item Failure analysis of two sets of aircraft blades(2010-04) Silveira, E.; Atxaga, G.; Irisarri, A. M.; Caracterización y Validación. Materiales; EXTREMAT; Tecnalia Research & InnovationThis paper describes the methodology employed for the failure analysis of aircraft blades and its application to two premature failed sets. The first one corresponds to the high pressure compressor manufactured in a 718 nickel base superalloy. The failure analysis carried out on this blade points towards foreign object damage (FOD). The second set belongs to the high pressure turbine of another engine. Scanning electron microscopy attributes the first fail to the premature failure by a thermo-mechanical fatigue mechanism of one blade with an inadequate microstructure. The remaining blades of this set, which possess a correct microstructure, failed due to the impacts of the debris generated by the fracture of the first one.Item Influence of the level of damage on the high temperature fatigue life of an aircraft turbine disc(2009-03) Silveira, E.; Atxaga, G.; Irisarri, A. M.; Caracterización y Validación. Materiales; EXTREMAT; Tecnalia Research & InnovationThis paper analyses the effect induced by those scratches produced during the handling and mounting of an aircraft turbine disc on their fatigue life. Fatigue tests were performed at 300 and 600 °C on specimens without and with various levels of damage. At 600 °C, an inverse relationship between the depth of the scratches and the fatigue life was found. However, at 300 °C no effect of these scratches on fatigue life was detected, obtaining very similar results in all of them. Examination of the failed specimens revealed that failure originated away from the scratch. Measurement of residual stresses helps to find an explanation to this apparently anomalous behaviour. It was observed that machining of the specimens induced high tensile residual stresses. At 600 °C, these stresses are relieved and failure at the scratched zone is promoted.Item Study of the failure of one machining tool(2010-03) Irisarri, A. M.; Silveira, E.; Tecnalia Research & Innovation; Caracterización y Validación. MaterialesThis paper presents the study of the failure of one tool that was broken in two pieces inducing a serious damage in the component that was being machined. The main difficulty for this analysis came up against the need of keeping the broken tool in the as-received condition due to legal requirements. Due to this situation it was not possible obtaining tensile test specimens to determine the strength and ductility of the material or metallographic samples which could reveal its microstructure. Consequently, the study was restricted to observing the fracture surfaces in the scanning electron microscope and identifying by X-ray energy dispersive spectrometry, the nature of the substances which could have played a role in the failure process. This analysis allowed identifying the failure origin was sited on a notch induced on the periphery of the tool in a zone where a section change and a marked stress concentration existed. This notch was covered by a dark substance whose composition was near the same than that of the blueing coating, indicating that it was already opened when this surface treatment was applied. These results, leaded to a conclusion blaming the machining operation previous to the blueing coating for the failure.Item Study on the distortion of steel worm shafts(2009-06) Silveira, E.; Irisarri, A. M.; Caracterización y Validación. Materiales; Tecnalia Research & InnovationThis paper analyses the root causes for the distortion observed in some C45E grade steel worm shafts during the last steps of machining. Research carried out on two round bars of the steel where distortion was observed and two other ones of a batch machined without distortion were studied. Moreover, two worm shafts in the last steps of the machining process were also analysed. Residual stresses measurements revealed lower and more homogeneous distribution in the bars which do not exhibit the problem. Yield stress and ultimate tensile stress values recorded in the steel of these bars were also lower than those measured in the bars which presented the problem. Metallographic study of the first ones revealed a broken morphology of cementite in the pearlite pointing towards a material stress relieved after the rolling process, eliminating, at least partially, those stresses generated during the deformation of the bar. On the other hand, the pearlite in the steel which suffers distortion looked to be formed during the cooling process after rolling and no given posterior stress relief heat treatment. A stress relief heat treatment of the bars and/or a kinder machining are recommended.Item Study on the root causes for the premature failure of an aircraft turbine blade(2009-03) Silveira, E.; Atxaga, G.; Erauzkin, E.; Irisarri, A. M.; Caracterización y Validación. Materiales; EXTREMAT; Tecnalia Research & InnovationA study on the root causes of the premature failure of a set of blades belonging to the high pressure turbine of an aircraft engine has been carried out. These blades were manufactured using a precipitation hardened nickel base alloy. The study consisted in a fractographic analysis by scanning electron microscopy and a microstructural examination by optical and scanning electron microscopy, identifying those phases which were present by means of X-ray energy dispersive spectrometry. Fractographic analysis revealed that failure of the first blade was due to thermo-mechanical fatigue, initiated at the internal cooling cavities. The presence of large size, cracked, hafnium and tantalum primary carbides on the fracture surfaces indicates that they have played an important role on the failure process, accelerating it. The other blades failed later by the impacts of the fragments lost from the first one.Item Titanium composite materials for transportation applications(2008-11) García de Cortazar, M.; Agote, I.; Silveira, E.; Egizabal, P.; Coleto, J.; Le Petitcorps, Y.; CIRMETAL; EXTREMAT; Caracterización y Validación. Materiales; Tecnalia Research & Innovation; MercadoDiscontinuously reinforced titanium alloys containing in-situ formed TiB needles are emerging as candidate materials for advanced applications. This new family of titanium composites presents technical advantages, and it can be less expensive and easily amenable for net-shape manufacturing relative to titanium metal-matrix composites developed to date. The production of a master compound by a novel and cost-effective process called self-propagating high-temperature synthesis (SHS) has been studied, This master compound could be subsequently used in an investment casting process to obtain TiB-reinforced net-shape titanium-matrix composites. The SHS technique and its features were investigated in depth before a suitable master compound was defined and produced. Cast samples obtained from the addition of the master compound have been produced and the most important issues concerning the processing, microstructure, and mechanical properties are highlighted in this paper.