Search results for " and Structure"
showing 10 items of 42 documents
Graduate employment and the returns to higher education in Africa
2013
http://cemapre.iseg.utl.pt/educonf/2e3/files/submissions_to_web/Barounia%20Mahdi_Broeckeb%20%20Stijn.docx; In this paper, we estimate the return to higher education for 12 African countries using recent data and a variety of methods. Importantly, one of our methods adjusts for the effect of higher education on the rate of joblessness, which is substantial in most African countries, and particularly for women. Our results confirm that Mincerian coefficients cannot be interpreted as a true rate of return, and that the latter (even after taking into account the employment effect) is considerably lower than what has previously been suggested in the literature (less than half). For Sub-Saharan A…
Investigation of thick sheet AHSS springback in combined bending under tension
2012
In this paper, we investigate the springback behavior of several advanced high-strength sheet steels (TRIP, Dual-Phase, ferrite-bainite) with thicknesses up to 4 mm. Samples were tested by means of the bending-under-tension (BUT) test. The BUT has been extensively applied, in the literature, to relatively thin (1 mm and thinner) sheet metals for automotive applications; the applicability of several guidelines from the literature was investigated in this work in the context of thick advanced high strength steel (AHSS) sheets and using a sample width of 12 mm. The monotonic decrease of springback as back force increased was confirmed for this category of sheet steels, and a general trend for …
Numerical modelling of low velocity multi-impact test on different stacking sequences
2019
The use of composite materials in the industrial field has been growing significantly for many years. This increase is explained by the fact that the industry, especially aeronautics which was pioneering in this field, is interested in the lightening of structures in order to be able to take up the new environmental challenges. Whether in the aeronautical field or in the land transport sector, structural elements may undergo multi-impactsor impact. Even at low velocitypose a threat to the integrity of the material and the structure itself. The objective of this work is to propose a numerical model to determine the damage within a composite structure subjected to low energy multi-impact. The…
Determination of dynamic properties of flax fibres reinforced laminate using vibration measurements
2017
International audience; Experimental and numerical methods to identify the linear viscoelastic properties of flax fibre reinforced polymer (FFRP) composite are presented in this study. The method relies on the evolution of storage modulus and loss factor as observed through the frequency response. Free-free symmetrically guided beams were excited in the dynamic range of 10 Hz to 4 kHz with a swept sine excitation focused around their first modes. A fractional derivative Zener model has been identified to predict the complex moduli. A modified ply constitutive law has been then implemented in a classical laminates theory calculation (CLT) routine. Overall, the Zener model fitted the experime…
Promoting self-employment: Does it create more employment and business activity?
2021
International audience; We assess the economic impact of reforms promoting self-employment in the three countries that have implemented such reforms since the early 2000s: the Netherlands, the United Kingdom and France. To that end, we use an unbalanced cross country-industry dataset of 4,226 observations, including 12 OECD countries and 20 market industries, over the 1995-2016 period. We first observe, using country-level data, that the share of self-employed workers in total employment is quite stable or declines over the period in all countries in our dataset, except in the three countries where large reforms promoting self-employment have been implemented, and only after these reforms. …
Mechanical characterization of bio-based composite/metal laminates for an application in street furniture
2019
In this work, it is proposed to study the influence of three manufacturing parameters in the development of bio-basedcomposite/steel hybrids. These parameters arethe methodof assembly between composite and metal, the distribution of composite and steellayers throughthe thicknessof the hybrid,and the stacking sequence of the composite part of the hybrid. The study was conducted through impact tests at different energies and quasi-static three-point bending tests. For each of these parameters, the influenceon the mechanical properties of the hybrid is evaluated.The results show that these properties depend essentially on the relative distribution of steel and composite through the thickness.
Higher Education Institutions Quality and Graduate Wages in Tunisia
2017
International audience; We estimate the effect of university characteristics on the return to higher education in Tunisia. We use a variety of administrative data from the Ministry of Higher Education and Research, the Ministry of Vocational Training and Employment and the National Social Security Fund. We consider econometric approaches based on multilevel modeling, which distinguishes more precisely between the effects of individual factors and institutional factors on earnings. Our findings confirm the relationship between the income and some university characteristics such as the number of permanent teachers, the selectivity of the higher learning institutions at the academic orientatio…
Microstructure-oxidation resistance relationship in Ti3AlC2 MAX phase
2020
International audience; Spark Plasma Sintering and Hot Isostatic Pressing were used to synthesize coarse-grained and fine-grained Ti3AlC2 specimens. Moreover, Spark Plasma Sintering processing parameters were modified in order to vary the TiC, Al2O3 and TixAly impurity and the porosity contents in the fine-grained samples. The influence of the Ti3AlC2 microstructure on the oxidation resistance was assesed. It is demonstrated that the grain size can drastically modify the oxidation resistance. The higher density of grain boundaries, in fine-grained specimens, increases the number of Al diffusion paths and leads to the formation of a protective alumina scale. In coarse-grained sample, Al diff…
Tensile behaviour of patch-repaired CFRP laminates
2011
The present study examines the tensile behaviour of composite structures repaired by bonding external patches. Various patches of different stacking sequences placed on both sides of the parent plate were considered. Damage development and the failure process of the repaired plates were analyzed and a parent plate fracture model has been proposed. Optimised patch repairs were calculated by finite element modelling. It was found that high stress concentration along the longitudinal edges of circular patches and/or at the transverse edges of the hole leads to early damage initiation in the parent plate. However, the position of damage initiation and the process of damage progression depend pa…
Two multilayered plate models with transverse shear warping functions issued from three dimensional elasticity equations
2014
Abstract A multilayered plate theory which uses transverse shear warping functions is presented. Two methods to obtain the transverse shear warping functions from three-dimensional elasticity equations are proposed. The warping functions are issued from the variations of transverse shear stresses computed at specific points of a simply supported plate. The first method considers an exact 3D solution of the problem. The second method uses the solution provided by the model itself: the transverse shear stresses are computed integrating equilibrium equations. Hence, an iterative process is applied, the model is updated with the new warping functions, and so on. Once the sets of warping functio…