The piston material choice is a major factor in the design stages of internal combustion engines for its importance to improving the durability and the operation reliability during the piston life cycle. Indeed, even as many researches have been conducted for a long time to improve the piston performances in the diesel engine, considerable numbers of piston damages still significantly occur. This research work is an assessment by the finite element method (FEM) of a set of piston materials for the purpose of being used in a direct injection diesel engine. The main objective is to predict stresses concentrations and the clearance between the piston and the cylinder (to avoid metal-metal adhesion) from thermomechanical solicitations. The stresses and deformations are evaluated in a 3D piston model by using ABAQUS software. A first assessment step is performed in heat convection/conduction modes to determine the temperature distribution. Then, this last one is coupled to the pressure field resulting from the gas combustion in order to compute stresses and the magnitude displacement. The obtained results show that the austenitic steel AS12UNG with fibre-reinforced possess low thermomechanical stress values compared to other material types. This material allows a minimum failure risk and therefore contributes to the enhancement of the piston design.
The aim of this research work is to simultaneously evaluate the effects of inhomogeneous plastic strain-induced and anisotropy on frictional behavior. The studied material is the cold-rolled steel grade DC06EK intended for sheet metal forming. To achieve this work, stretched and unstretched DC06EK strips following different rolling directions (0°, 45° and 90°) with different levels of equivalent plastic strain were used in microscratch tests. The findings show that the calculated coefficient of friction (COF) decreases as a function of the equivalent plastic strain for different rolling directions. The COF have a clear trend lines of regression except in the case for 45°. Trend lines of the COF following 0° and 90° converge to very closely values, since the effect of anisotropy disappears with the increase in the level of plastic strain.
Purpose After more than a century of agreement with the postulate of non-slip condition (adhesion to the wall), the study of fluid-solid boundary conditions has shown renewed interest over the past two decades. Although numerous studies have not yet been arrived to a complete description of slip phenomena, however, it appears that the influence of wetting and/or surface roughness results in a weak interaction between fluid and solid; thus, the presence of the slip phenomenon is observed at the fluid-solid interface. The purpose of this paper is to highlight the presence of the slip phenomenon at the lubricated piston skirt-cylinder contact. Design/methodology/approach For this proposal, a modified Reynolds equation and operating characteristics are determined by taking into account the slip conditions at the interface between oil-film and entire cylinder surface. Findings The findings indicate that the operating characteristics are strongly influenced when the slip conditions are taken into account at the interface between oil-film and cylinder surface. The friction force and dissipated power might be reduced to improve diesel engine performances. Originality/value Various research studies have been conducted to model the slip phenomenon in different lubricated contacts over the past two decades. However, there are no studies available concerning the piston-cylinder system. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2019-0483/
The aim of this work is to simultaneously evaluate the effects of inhomogeneous strain-induced and anisotropy on the friction during the deep drawing of DC06EK sheet metal. To do that, stretched and unstretched DC06EK strips in different rolling directions (0°, 45° and 90°) with different levels of equivalent plastic strain were used in microscratch tests under the same conditions as those used in deep drawing process (DDP) coming from a local industry. The findings show that the coefficient of friction (COF) decreases as a function of the equivalent plastic strain for different rolling directions. Two empirical friction laws are obtained depending on the equivalent plastic strain following 0° and 90° to the rolling direction. Since the COF have a clear trend of regression except in the case for 45°. Trend lines of the COF following 0° and 90° converge to very closely values, since the effect of anisotropy disappears with the increase in the level of plastic strain.
A x-dynamic factor of amplification for the longitudinal deformation; A θ:-dynamic factor of amplification for the radial deformation; [C]-matrix of rigidity; [D]-matrix of the compression forces; E-Young modulus; h-oil film thickness; H(x)-heaviside distribution; P(x,t)-hydrodynamic pressure; R-average radius of the bearing; t-time; U(x;t)-longitudinal displacement; V-linear speed; Vb-speed propagation of the longitudinal wave; Vp-speed propagation of the radial wave; W(x,t)-radial displacement; x-axial coordinate; []-deformation vector; x-longitudinal deformation; -radial deformation; -Poisson's ratio; -rod-bearing frequency; -density; x-longitudinal constraint; -transversal constraint; -angular position.
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