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81.
L. Bamoulid D. De Caro A. Ben Bachir S. El Hajjaji F. Ansart 《Surface & coatings technology》2008,202(20):5020-5026
In the present work, a novel process has been developed to improve the corrosion properties of ferritic stainless steels. Titanium oxide coatings have been deposited onto stainless steel by sol-gel process after a pre-functionalization of the substrate in a conversion bath. Gel titania was prepared by hydrolysis of a titanium butoxide through a sol-gel process. Duplex systems “conversion layer/uniform TiO2 coating” have been prepared on stainless steels using a dipping technique and thermal post-treatments at 450 °C. The preparation of sol-gel coatings with specific chemical functions offers tailoring of their structure, texture and thickness and allows the fabrication of large coatings. The morphology and structure of the coatings were analysed using scanning electron microscopy with field effect gun (SEM-FEG), Mass spectroscopy of secondary ions (SIMS) and X-ray diffraction (XRD). The anticorrosion performances and the ageing effects of the coatings have been evaluated in neutral and aggressive media by using several normalized tests.The results show that the conversion layer was not sufficient to protect steel but sol-gel TiO2 coatings, anchored on the metal substrate via the conversion layer, show good adhesion with the substrate and act as a very efficient protective barrier against corrosion. So, duplex layers with TiO2 nanoparticle coatings on steels exhibit an excellent corrosion resistance due to a ceramic protective barrier on metal surface. Analysis of the data indicates that the films act as geometric blocking layers against exposure to the corrosive media and increase drastically the lifetime of the substrate. 相似文献
82.
Abdelylah Benazza Abdelkader Ziadi Boualem Serier Belabbes Bachir Bouiadjra Benali Boutabout 《Journal of Materials Science》2007,42(3):834-840
The rolls in the finishing stands must have good resistance to both wear and fire cracks. The use of high-speed steel at the
finishing stands has shown satisfactory results. The composition of this high-alloyed steel is an important parameter as the
most significant change lays on the type, morphology, and volume fraction of the eutectics carbides. The heat treatment of
these products consists of high temperature austenization followed by quenching and two temperings, as required in order to
increase their overall hardness and to completely eliminate residual austenite. The influence of tempering temperatures on
the mechanical properties of these products, determined using tensile, hot compression and fracture toughness tests, was studied
in this research work. Their corresponding failure micromechanisms were defined by means of the analysis of fracture surfaces. 相似文献
83.
A mixed mode crack growth model taking account of fracture surface contact and friction 总被引:1,自引:1,他引:0
Fracture surface interactions, of whatever origin, can significantly affect the stress intensity factor, and consequently,
can also be relevant to fatigue crack propagation. In the occurrence of interaction between fracture surfaces, the effective
loading cycle experienced by material near the crack tip may be very different from that evaluated on the basis of the external
loadings only. The purpose of the work described in this paper is to obtain the effective mode II stress intensity factor,
k
IIeff, in a surface cracked elasto-plastic plate with a factory roof fracture surface subjected to an in-plane shear (mode II)
loading. A new model estimating the magnitude of the frictional mode II stress intensity factor, k
f, arising from the mismatch of the fracture surface roughness during in-plane shear, is developed. Furthermore, the results
of this study are employed in modeling the fatigue response of the surface cracked plates subjected to mixed mode loading. 相似文献
84.
Sallai Ben-Oumrane Tounsi Abedlouahed Mechab Ismail Bachir Bouiadjra Mohamed Meradjah Mustapha Adda Bedia El Abbas 《Computational Materials Science》2009,44(4):1344-1350
In this paper, an elastic, rectangular, and simply supported, sigmoid functionally graded material (S-FGM) beam of thick thickness subjected to uniformly distributed transverse loading has been investigated. The S-FGM system consists of ceramic (Al2O3) and metal (Al) phases varying through the thickness of beam. Major classes of representative theories such as classical laminate beam theory (CLBT), first-order shear deformation theory (FSDT) and high-order theories (HOTs) have been considered and a unified kinematic formulation is then proposed. The Poisson’s ratio of the thick S-FGM beam is assumed to be constant, but their Young’s moduli vary continuously throughout the thickness direction according to the volume fraction of constituents defined by sigmoid function. The numerical illustrations concern bending response of S-FGM rectangular beams. Qualitative and quantitative assessments of displacement and stress fields have been presented and discussed. 相似文献
85.
The viscoelastic behaviour of polybutene-1-polypropene blends has been studied in the molten state with respect to temperature, shear stress and shear rate. The corrections of experimental data have been carried out and the influence of the radius of capillary on these corrections was studied. The elasticity was investigated by means of Barus factor and the variation of viscosity versus composition of blends shows a minimum which might be interesting for the technology of plastic materials. 相似文献
86.
B. Mechab B. Serier B. Bachir Bouiadjra K. Kaddouri X. Feaugas 《International Journal of Pressure Vessels and Piping》2011
In this paper, the J integral was calculated for semi-elliptical surface cracks in pipes under bending using three-dimensional finite element analysis. The computations were performed for elastic and elastic-plastic behaviours. For the elastic case, the numerical results allowed the extrapolation of shape functions for analytical determination of the J integral. The results are in a good agreement with those in the literature if the ratio between the radius and the thickness of the pipe (R/t) is from 1 to 10. The analysis was extended to values of the ratio R/t higher than 10. For the elastic-plastic, the numerical results are in good agreement with the analytical solution found in the literature for thick pipes (R/t ≥ 10). The effect of the ratio R/t becomes sensible when the ratio of the applied moment to the moment of reference (M/Mor) exceeds 0.9. 相似文献
87.
Zúñiga-Aguilar C. J. Gómez-Aguilar J. F. Romero-Ugalde H. M. Jahanshahi Hadi Alsaadi Fawaz E. 《Engineering with Computers》2022,38(4):3085-3108
Engineering with Computers - Neuronal networks are used in different fields of science and technology due to their capacity to approximate nonlinear functions through the synaptic weights... 相似文献
88.
Damir Cavka Basma Harrat Dragan Poljak Bachir Nekhoul Kamal Kerroum Khalil El Khamlichi Drissi 《Engineering Analysis with Boundary Elements》2011,35(10):1101-1108
The paper deals with transient analysis of grounding grids using two different approaches, wire antenna theory and modified transmission line model. The Pocklington integro-differential equations, in frequency domain, arising from the wire antenna theory are numerically handled via the Galerkin–Bubnov variant of indirect Boundary Element Method (GB-IBEM), while the transient response was obtained using inverse Fourier transform. The modified transmission line equations are treated using the finite difference time domain (FDTD) method. Some illustrative numerical results are presented and discussed in the paper. 相似文献
89.
John Montesano Marina Selezneva Zouheir Fawaz Cheung Poon Kamran Behdinan 《Composites Part A》2012,43(9):1454-1466
The off-axis tensile fatigue behavior of a woven fiber/bismaleimide laminate is investigated at various temperatures. Emphasis was placed on characterization of the laminates and the development of an analytical fatigue damage model. Fatigue tests revealed that the material exhibits an atypical three-stage response in terms of stiffness degradation and permanent strain. Fiber yarn rotation was found to be a dominant mechanism in the initial stage of cycling causing high permanent strain and slight stiffness increase, while damage accumulation due to cyclic loading was dominant in the final stage causing rapid stiffness degradation. The mean strain variation during cycling was found to be proportional to the test temperature in each stage, and thus a more meaningful indicator for fatigue damage development. The corresponding analytical damage model was able to accurately capture the three-stage damage development. The current model can be used to determine damage development for cyclic loading at intermediate temperatures. 相似文献
90.
Bachir Dadda Saïd Abboudi Rida Zarrit Abderrahmane Ghezal 《International Journal of Hydrogen Energy》2014
Water transport in the membrane of a PEM fuel cell is provided essentially by a convective force, resulting from a pressure gradient, an osmotic force, due to a concentration gradient and an electric force caused by the protons migration from the anode to the cathode. Through these three types of force the two-dimensional behavior of electric potential has been studied in this paper. The adopted model in this work is based on the assumption of single phase and multi-species flow, supposed two-dimensional and transient in a porous medium. The species conservation equation is coupled with the energy equation through the diffusion coefficient of water and the heat convective flux. The set of governing equations in the form of convection–diffusion problem has been solved numerically using the finite volume method. The obtained results show the transient two-dimensional effect of heat and mass transfer on the voltage variation within the membrane. 相似文献