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Karia Ba Mohamed, Morocco

Fergani O.,Norwegian University of Science and Technology | Fergani O.,Georgia Institute of Technology | Pan Z.,Georgia Institute of Technology | Liang S.Y.,Georgia Institute of Technology | And 2 more authors.
Procedia CIRP | Year: 2016

During machining and due to the thermo-mechanical load, the material properties of the component are expected to evolve because of the changes in the microstructure attributes. Crystallographic texture is important as it defines the anisotropy and influences directly the fatigue behavior. In this work, we propose a systematic approach to predict the texture evolution in machined workpiece using combined FEM and Visco Plastic Self Consistent (VPSC) methodologies. The prediction tool implementation is described in details and tested for bearing steel during hard turning. The output this model will help to develop meta-models capable of assisting the machining process planning to achieve desired properties and functionalities. © 2016 The Authors. Source

Aguilar F.J.,University of Almeria | Nemmaoui A.,University of Almeria | Aguilar M.A.,University of Almeria | Chourak M.,University of Mohamed i | And 2 more authors.
Forests | Year: 2016

A quantitative assessment of forest cover change in the Moulouya River watershed (Morocco) was carried out by means of an innovative approach from atmospherically corrected reflectance Landsat images corresponding to 1984 (Landsat 5 Thematic Mapper) and 2013 (Landsat 8 Operational Land Imager). An object-based image analysis (OBIA) was undertaken to classify segmented objects as forested or non-forested within the 2013 Landsat orthomosaic. A Random Forest classifier was applied to a set of training data based on a features vector composed of different types of object features such as vegetation indices, mean spectral values and pixel-based fractional cover derived from probabilistic spectral mixture analysis). The very high spatial resolution image data of Google Earth 2013 were employed to train/validate the Random Forest classifier, ranking the NDVI vegetation index and the corresponding pixel-based percentages of photosynthetic vegetation and bare soil as the most statistically significant object features to extract forested and non-forested areas. Regarding classification accuracy, an overall accuracy of 92.34% was achieved. The previously developed classification scheme was applied to the 1984 Landsat data to extract the forest cover change between 1984 and 2013, showing a slight net increase of 5.3% (ca. 8800 ha) in forested areas for the whole region. © 2016 by the authors. Source

Nekkal F.,University of Mohamed i | Aouraghe H.,University of Mohamed i
Research Journal of Applied Sciences | Year: 2016

Archaeological research conducted during the past two decades in the Eastern Rif region have allowed the discovery of several sites of prehistoric settlements whose occupations date back mainly to the different phases of the Holocene. The excavations carried out in some of them have yielded new data on the economy of the first agro-pastoral societies of Morocco and to identify their different cultural aspects. This study presents, the results of the preliminary study of milling and grinding tools discovered in the site of Ifri Ouzabour whose main occupation levels date back to the Early and Late Neolithic. The site is marked by a considerable amount of this kind of objects in comparison with the surrounding sites. The set of available tools is taken into account and actual selection could be highlighted in the selection of materials and shapes according to the use of the objects. © Medwell Journals, 2016. Source

Atmani Z.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Atmani Z.,University of Mohamed i | Haddag B.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Nouari M.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Zenasni M.,University of Mohamed i
Procedia CIRP | Year: 2015

In metal machining, the workmaterial undergoes severe thermomechanical loading, which has a consequence on the microstructure change at different zones in the machined workpiece (chip, tool tip zone, machined surface). In this paper, a multi-physics modelling in machining OFHC copper was proposed. The plastic flow stress of the workmaterial is described by the so-called Mechanical Threshold Stress (MTS) model. For comparison purpose the classical Johnson-Cook (JC) thermo-viscoplastic flow stress model is also introduced. In order to predict the microstructure change, precisely the grain size evolution in the workmaterial during machining, a physical-based Dislocation Density (DD) model was coupled with the MTS model in the framework of an Arbitrary Lagrangian Eulerian (ALE) Finite Elements (FE) approach. The ALE-FE model is developed for the orthogonal cutting process simulation in 2D case. Coupled MTS-DD material models were implemented in Abaqus/Explicit software via a user-material program. The first part of the multi-physics model is validated by comparison of predicted cutting force components with experimental ones and those predicted by the JC model. In the second part, the grain refinement during the cutting process is predicted, revealing zones where the microstructure is highly affected, particularly in the depth of the newly formed surface. This allows estimating the thickness of the effected subsurface by the cutting process. © 2015 The Authors. Published by Elsevier B.V. Source

Haddag B.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Atlati S.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Atlati S.,University of Mohamed i | Nouari M.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Zenasni M.,University of Mohamed i
Heat and Mass Transfer/Waerme- und Stoffuebertragung | Year: 2015

This paper deals with the modelling and identification of the heat exchange at the tool–workpiece interface in machining. A thermomechanical modelling has been established including heat balance equations of the tool–workpiece interface which take into account the heat generated by friction and the heat transfer by conduction due to the thermal contact resistance. The interface heat balance equations involve two coefficients: heat generation coefficient (HGC) of the frictional heat and heat transfer coefficient (HTC) of the heat conduction (inverse of the thermal contact resistance coefficient). Using experimental average heat flux in the tool, estimated for several cutting speeds, an identification procedure of the HGC–HTC couple, involved in the established thermomechanical FE-based modelling of the cutting process, has been proposed, which gives the numerical heat flux equal the measured one for each cutting speed. Using identified values of the HGC–HTC couple, evolution laws are proposed for the HGC as function of cutting speed, and then as function of sliding velocity at the tool–workpiece interface. Such laws can be implemented for instance in a Finite Element code for machining simulations. © 2015, Springer-Verlag Berlin Heidelberg. Source

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