No abstract

No abstract

No abstract

This paper investigated the effect of the cutting parameters of a blade on the tillage force components using finite element modeling. A three-dimensional model was carried out with Abaqus Explicit in order to study the interaction between the tool and soil. The soil was modeled with linear forms of the Drucker-Pager model, while the tool was considered as a rigid body with a reference point taken at its tip. The effect of tillage depth and the width of a vertical blade were studied. It was found that the amounts of the draught and vertical forces increase linearly with a slope of 0.037 and 0.0143 respectively when the width increases. The narrow tool (width < 60mm) has a greater effect on the specific draught force than a larger tool. Draught and specific draught force increase with polynomial and linear curve respectively versus the depth. However, this effect was reduced for the vertical force. These results were in a good agreement with previously published works. The second part of this paper is focused on the oblique position of the blade to evaluate the effect of the attack angles on both the tillage forces (draught, lateral and vertical) and the cutting process of the soil during and after its failure. For all considered angles, the draught force presents the highest values compared to the vertical and lateral forces. Results showed that working with small cutting and an average rake angles (30°to 60°and 45°respectively) can produce a good soil inversion.Additional key words: FEM; oblique blade; force; attack angles.* Corresponding author: ayadi.ibrahmi@yahoo.fr; ayadiibrahmi@hotmail.fr Received: 16-02-14. Accepted: 10-10-14.Abbreviations used: CFD (computational fluid dynamics); DEM (discrete element method); FEM (finite element method); RF (reaction force); RF2 (vertical force); RF3 (draught force); α (cutting angle); θ (rake angle).

This study provides an experimental investigation on the corrosion behaviour of three carbon steels used for pipeline application. The susceptibility of these materials to corrosion damage was analysed in order to simulate its service conditions particularly under disbonded coating. Monitoring of open-circuit potential (E free ), polarization resistance (R p ) and measuring of the weight loss during immersion time were used to evaluate the corrosion behaviour of the studied materials. All the corrosion experiments were performed in two aqueous solutions: natural seawater and synthetic one (3 wt% NaCl solution). The morphology of the corrosion products was examined by optical microscopy. The results obtained from electrochemical tests have shown different behaviour for the studied steels into the retained corrosive environments: more stable potentials (E free ), higher R p -values with large fluctuations evolution were found in natural seawater. The gravimetric measurements have also shown a continuous variation of the weight loss throughout the exposure period in the sodium chloride solution. However, it seemed that a passive behaviour was observed in natural seawater. A little difference was observed between all the studied steels in terms of corrosion kinetics. The steel, having the little ferritic grain size, seems to be more resistant to corrosion damage. Qualitatively, a porous and non-adherent oxide film was observed on the corroded surface in the synthetic solution; while, the rust layer, which is formed in the natural seawater, has acted as a barrier of corrosion process. Finally, all the results obtained from both electrochemical tests and weight loss measurements were in reasonably good accordance. The important common point that can be concluded was that all the tested materials seem to be more suitable for natural seawater than 3 wt% NaCl solution. Also, they are not recommendable to be used in an environment where chloride attack is possible and important.