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The grooved lip effect on reciprocating hydraulic rod seal performances in transient condition: elastohydrodynamic lubrication

Bahi Y., El Gadari M., Rahmoune M.

International Journal of Applied Mechanics and Engineering

2020

Vol. 25, no. 2

11--21

It is commonly known that the sealing performance of dynamic seals is significantly influenced by the surface finish. To reduce friction effect and leakage ratio, new generations of grooved lip or shaft have emerged, but only two computational models were performed up to now with a textured elastomeric lip: spiral groove in the axial direction or micro-cavities according to the circumferential direction. However, if the numerical results have confirmed the slight effect of the grooved lip on the rotary lip seal performances, it seems relevant to investigate the influence of such grooves on the reciprocating hydraulic rod seal behavior. Thus, the scope of this work is to perform a parametric study of the grooved lip throughout a one-dimensional elastohydrodynamic model by taking into account the elasticity of the lip and the shaft roughness. After confirming the validity of the current model, numerical simulations have been performed and compared with experiments. The effect of lip grooves on the hydraulic rod seal behavior in outstroke and instroke shaft motion has been underlined. Thereby, it is shown that the leakage and the average film thickness are sensible to both the depth and the density of the lip groove. Additionally, a slight effect of the pattern shape is observed on the friction force.

The effect of pressure and alloying on half-metallicity of quaternary Heusler compounds CoMnYZ (Z = Al, Ga, and In)

Rahmoune M., Chahed A., Amar A., Rozale H., Lakdja A., Benhelal O., Sayede A.

Materials Science Poland

2016

Vol. 34, No. 4

905--915

In this work, first-principles calculations of the structural, electronic and magnetic properties of Heusler alloys CoMnYAl, CoMnYGa and CoMnYIn are presented. The full potential linearized augmented plane waves (FP-LAPW) method based on the density functional theory (DFT) has been applied. The structural results showed that CoMnYZ (Z = Al, Ga, In) compounds in the stable structure of type 1+FM were true half-metallic (HM) ferromagnets. The minority (half-metallic) band gaps were found to be 0.51 (0.158), 0.59 (0.294), and 0.54 (0.195) eV for Z = Al, Ga, and In, respectively. The characteristics of energy bands and origin of minority band gaps were also studied. In addition, the effect of volumetric and tetragonal strain on HM character was studied. We also investigated the structural, electronic and magnetic properties of the doped Heusler alloys CoMnYGa1-xAlx, CoMnYAl1-xInx and CoMnYGa1-xInx (x = 0, 0.25, 0.5, 0.75, 1). The composition dependence of the lattice parameters obeys Vegard’s law. All alloy compositions exhibit HM ferromagnetic behavior with a high Curie temperature (TC).