197,741 research outputs found
Fretting wear of alloy steels at the blade tip of steam turbines
No full textIn order to reduce blade resonant vibration amplitude in turbomachinery, blades are assembled with a mutual interlocking at the tip. The aim of this study is to investigate the wear mechanism at the contact interface of the blade shroud in steam turbines. Experimental data are available concerning the wear mechanism at interfaces of aircraft engines blades, while the literature regarding the same effect on steam turbines is less rich. Moreover, the transposition of the results from the aero-engine to the steam turbine is difficult, because materials and working conditions are different. To overcome this lack of knowledge an experimental campaign was set up to investigate this wear mechanism under the specific conditions and with the distinctive materials used in steam turbines.
Two base materials (alloy steels) were tested under different conditions: surface treatment (with and without laser quenching), temperature and normal load. Dissipated energies were determined from the hysteresis loops measured during the tests and were correlated to the test conditions. Profiles of worn surfaces were measured, and volume losses were accurately computed with a procedure that takes into account the roughness of the surfaces.
Experiments were conducted both at room and low temperature (150 °C). At room temperature the surface temperature increased to 60-70 °C, due to the heat generated in the wear process. Comparison of volume losses at room and low temperature showed that at 150°C the volume losses decreased dramatically. This behavior was explained with a brittle-ductile transition. In other words, the same wear mechanism, adhesion and abrasion respectively in stick and gross slip condition, give very different results for a small softening effect of the material. Moreover, experimental results showed much more sensitive wear rates to the heat treatment than to the steel type
Nora III. Prospezione a Nora 1993
No full textProgetto Nora. Ricognizioni nell'area suburbana.Progetto Nora. The suburban area od the Phoenicia cit
Nora II. Prospezione a Nora, 1992
No full textProgetto Nora. Primo contributo sulle ricerche di superficie nell'area urbana colonialeProgetto Nora. The first paper on the survey on the urban colonial area
Sobre alguns poemas de António Botto dispersos na imprensa brasileira/ About some of António Botto’s poems dispersed in the brazilian press
No full textResumo: Entre 1947 e 1959, António Botto viveu no Brasil um exílio voluntário e publicou diversos textos literários, principalmente poesia e narrativas curtas, em diferentes periódicos do país durante esses anos. Entretanto, tal produção literária, dispersa na imprensa, continua praticamente desconhecida. Por isso, o artigo visa resgatar e analisar alguns dos poemas que foram publicados em jornais e que se mantém inéditos na obra conhecida do poeta, revelando que os anos brasileiros foram também um momento notável de criação literária. Assim, a reflexão acerca desse conjunto de textos permite compreender as transformações no estilo e na temática da escrita bottiana, principalmente quando comparadas com seus primeiros trabalhos.Palavras-chave: António Botto; poesia portuguesa; imprensa.Abstract: Between 1947 and 1959, António Botto lived a voluntary exile in Brazil and published several literary texts, mainly poetry and short narratives, in different periodicals in the country during those years. However, such literary production, dispersed in the press, remains virtually unknown. Therefore, the article aims to rescue and analyze some of the poems that were published in newspapers and remain unpublished in the known work of the poet, revealing that the Brazilian years were also a remarkable moment of literary creation. Thus, the reflection about this set of texts allows us to understand the transformations in style and theme of Botto’s writing, especially when compared with his early works.Keywords: António Botto; Portuguese poetry; press
Fretting wear damage mechanism of CoMoCrSi coatings
No full textSuperalloy coatings of the CoMoCrSi family (e.g. Tribaloy® T800) are applied to mitigate wear effects at high temperature. These coatings are extensively used on the contact surfaces of the shroud of turbine blades. If severe wear occurs on these contact surfaces the blade interlocking decreases, reducing the stiffness of the assembly, altering its dynamic behaviour, and increasing the risk of fatigue failure. Fretting is the expected damage mechanics on these mating surfaces. The study presented in this paper investigates the fretting damage mechanism of interfaces coated with CoMoCrSi alloys. The experimental plan includes fifteen combinations of the test parameters: two contact geometries, three deposition processes, four temperatures, three normal loads and three strokes. Wear at different number of cycles was also explored. Moreover, two types of contact geometries were investigated, namely point contact (sphere-on-flat) and flat-on-flat. The friction coefficient was computed using the hysteresis loops measured during the fretting tests. The topography of the contact surfaces was measured at different fretting wear cycles to estimate the volume loss. Wear grooves were observed by scanning electron microscopy. Results of point contact experiments at room temperature exhibited a steady friction coefficient independent of the normal load. Wear volumes showed a sharp increasing in wear rate at high dissipated energy while the trend was linear at lower dissipated energy. Oxidation was found more dependent on substrate than on temperature, stroke and wear cycles. Wear volumes and wear rate on flat-on-flat specimens coated with welded T800 were higher at 400 C than at room temperature and at high temperature (800 C). At room temperature, wear volumes of welded T800 applied by single layer were much higher than in dual layer. At room temperature and at low dissipated energy the wear rate of the point contact geometry was lower than flat-on-flat. At high energy, the wear rate of point contact tends to the flat-on-flat wear rate
Swallowing and spitting out the red pill: young men, vulnerability, and radicalization pathways in the manosphere
No full textDuring the last decades, new forms of men's rights activism have emerged, commonly referred to as the 'manosphere'. This loosely connected, misogynistic online movement particularly attracts young men. Its shared ideology is the Red Pill, a neoconservative ideology that adopts essentialist notions of gender and sexuality, and selectively employs evolutionary psychology to support male supremacy. While the discourses of the manosphere have been mapped, little research exists on how and why young men join and leave such misogynist groups. This article contributes to critical youth and feminist scholarship by analysing the gendered dynamics of online misogynist radicalization pathways. Based on narratives shared on a Reddit community for former 'redpillers', this article explores 30 young men's experiences of entering and exiting the manosphere and details the essential role of vulnerability in these processes. The stories are synthesized into three phases to illustrate the paths in and out of the manosphere
Su che cosa si regge la comunità politica? Discussioni e itinerari di ricerca
No full textA vent'anni dalla pubblicazione di "The Politics of Recognition" di Ch. Taylor e in occasione del bilancio tracciato al riguardo da N. Rengger, il saggio si interroga sul possibile fondamento delle odierne comunità politiche "plurali" e sul soggetto della democrazia, delineando alcune nuove piste di ricerca, suggerite anche dalla rilettura del neoliberalismo di J. Rawls operata da M. CangiottiTwenty years after the publication of 'The Politics of Recognition' by C. Taylor and in relation to Rengger's critical remarks, this essay investigates a possible foundation for contemporary 'plural' political communities and reflects on the subject of democracy. The essay, moreover, draws new research lines, inspired also by M. Cangiotti's reading of J. Rawls' neo-liberalism
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