259 research outputs found
Liquid lubrication in sheet metal forming at mesoscopic scale
The lubricant entrapment and escape phenomena in metal forming are studied experimentally as well as numerically. Experiments are carried out in strip reduction of aluminium sheet applying a transparent die to study the fluid flow between mesoscopic cavities. The numerical strategy is based on a weak fluid/structure coupling involving the Finite ElementMethod and analytical calculations. It allows to quantify the final shape of the lubricant pocket
Roughness Signature of Tribological Contact Calculated by a New Method of Peaks Curvature Radius Estimation on Fractal Surfaces
This paper proposes a new method of roughness peaks curvature radii calculation and its application to tribological contact analysis as characteristic signature of tribological contact. This method is introduced via the classical approach of the calculation of radius of asperity. In fact, the proposed approach provides a generalization to fractal profiles of the Nowicki's method [Nowicki B. Wear Vol.102, p.161-176, 1985] by introducing a fractal concept of curvature radii of surfaces, depending on the observation scale and also numerically depending on horizontal lines intercepted by the studied profile. It is then established the increasing of the dispersion of the measures of that lines with that of the corresponding radii and the dependence of calculated radii on the fractal dimension of the studied curve. Consequently, the notion of peak is mathematically reformulated. The efficiency of the proposed method was tested via simulations of fractal curves such as those described by Brownian motions. A new fractal function allowing the modelling of a large number of physical phenomena was also introduced, and one of the great applications developed in this paper consists in detecting the scale on which the measurement system introduces a smoothing artifact on the data measurement. New methodology is applied to analysis of tribological contact in metal forming process
Productive restructuring and the reallocation of work and employment: a survey of the “new” forms of social inequality
O propósito do presente artigo consiste
em questionar a inevitabilidade dos processos de
segmentação e precarização das relações de trabalho
e emprego, responsáveis pela inscrição de
“novas” formas de desigualdade social que alicerçam
o actual modelo de desenvolvimento das economias
e sociedades. Visa-se criticar os limites da
lógica econômica e financeira, de contornos globais,
que configuram um “novo espírito do capitalismo”,
ou seja, uma espécie de divinização da
ordem natural das coisas. Impõe-se fazer, por isso,
um périplo analítico pelas transformações em curso
no mercado de trabalho, acompanhado pela vigilância
epistemológica que permita enquadrar e
relativizar as (di)visões neoliberais e teses tecnodeterministas
dominantes. A perspectivação de cenários
sobre o futuro do trabalho encerrará este
périplo, permitindo-nos alertar para os condicionalismos
histórico-temporais, para a urgência de
se desocultar o que de ideológico e político existe
nas actuais lógicas de racionalização e para os
processos de ressimbolização do trabalho e emprego
enquanto “experiência social central” na
contemporaneidade.The scope of this paper is to question
the inevitability of the processes of segmentation
and increased precariousness of the relations
of labor and employment, which are responsible
for the introduction of “new” forms of
social inequality that underpin the current model
of development of economies and societies. It
seeks to criticize the limits of global financial and
economic logic, which constitute a “new spirit of
capitalism,” namely a kind of reverence for the
natural order of things. It is therefore necessary
to conduct an analytical survey of the ongoing
changes in the labor market, accompanied by epistemological
vigilance which makes it possible to
see neoliberal (di)visions and dominant technodeterministic
theses in context. The enunciation
of scenarios on the future of work will conclude
this survey and will make it possible to draw attention
to both the historical and temporal constraints
and to the urgent need to unveil what is
ideological and political in the prevailing logic of
rationalization and processes to reinstate work
and employment as a “central social experience”
in contemporary times
Evolution of the ridges of Midelt-Errachidia section in the High Atlas revealed by paleomagnetic data
New paleomagnetic data (43 sites) from Mesozoic sediments are contributed in this work, verifying the presence of a pervasive syntectonic Early Cretaceous remagnetization in the easternmost area of the Moroccan High Atlas. Using the small circle intersection method, we have calculated the characteristic remagnetization direction (Dec: 337.3, Inc: 38.4) that fits with a 100-Ma age, according to the Apparent Polar Wander Path of Africa. The paleomagnetic vectors of remagnetization are used to obtain the geometry during the remagnetization stage (100Ma) of one of the most renowned geological cross sections of the High Atlas, the Midelt-Errachidia profile. The partial restoration of the cross section at 100Ma allows us to determine the dips of the beds at the remagnetization stage in five structures (ridges or anticlines). Our results indicate that the five ridges that configure the Midelt-Errachidia profile were initiated to different degrees prior to wholesale compressive deformation during the Cenozoic. This configuration can be explained according to two different scenarios that we discuss in this paper: transpression and diapirism. The geological model obtained, both at present and at 100Ma, indicates the existence of a Mesozoic cover substantially decolled from the Paleozoic basement, what strongly contrasts with previously published transects of the same area
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