This study focuses on the dynamic and tribological characterisation of a single‐layer graphene sheet (SLGS). A 10 × 10 nm graphene model is developed, which is modally analysed for both zigzag and armchair lattices, thus enabling the examination of chirality effect on the SLGS' eigenfrequencies. The tribological analysis consists of the same SLGS model and a carbon atom simulating the graphene tip. The carbon atom is set to move on multiple paths to examine the importance of the path's position over the sheet. The friction forces applied on the tip during its movement can be calculated. The carbon atom tip is interlinked with the graphene atoms via the Lennard‐Jones model, characterising the real contact area. Spring elements mimic the interatomic forces, while beam and mass elements simulate the graphene's C─C covalent bonds and atoms, respectively, on a finite element simulation verified by the Prandtl‐Tomlinson model. It is perceived a strong stick‐slip effect on the friction force's areal pattern, which can be verified by the Prandtl‐Tomlinson theory of the atomic scale friction. It also became clear the effect of chirality, on graphene's tribological behaviour, after the differences in the calculated friction forces. Finally, an increase in the coefficient of friction analogous to the increase of the vertical load, due to graphene's deformation, is determined, while in the zigzag lattice, the coefficient of friction appears to be significantly lower that the armchair one.

Purpose The purpose of this paper is to focus on the creation of an isothermal elastic ring-liner model to highlight, through stresses, the occurrence of the plastic deformation in certain crank angles under extreme dry lubrication conditions. Design/methodology/approach The stresses that are exported from this analysis are pointing out not only the necessity for an elastoplastic model to be created, but also the importance of predicting the correct friction coefficient, as pointed out by both the contact surface stress and that in depth of the two bodies in contact. Findings The comparison between the finite element model and the adhesion mathematical model of Johnson, Kendall and Roberts seals the importance to calculate the interaction forces, acting on the common solid surface, in the pursuit of defining a propriate contact patch. Additionally, a three-dimensional ring model is built, highlighting the importance of the modeling surface’s micro asperities for a solid stress analysis. Also, numerical experiments are conducted, in contact with the cylinder and a piston ring made of an iron alloy and of two different plating materials, such us Chromium (Cr) and Chromium‒Nickel Alloy (CrN). The ability to calculate the stress concentration factor is also described. Originality/value A three-dimensional ring model is built, highlighting the importance of the modeling surface’s micro asperities for a solid stress analysis. Also, numerical experiments are conducted, in contact with the cylinder and a piston ring made of an iron alloy and of two different plating materials, such us Chromium (Cr) and Chromium‒Nickel Alloy (CrN). The ability to calculate the stress concentration factor is also described.

Up-to-date predictive rubber friction models require viscoelastic modulus information; thus, the accurate representation of storage and loss modulus components is fundamental. This study presents two separate empirical formulations for the complex moduli of viscoelastic materials such as rubber. The majority of complex modulus models found in the literature are based on tabulated dynamic testing data. A wide range of experimentally obtained rubber moduli are used in this study, such as SBR (styrene-butadiene rubber), reinforced SBR with filler particles and typical passenger car tyre rubber. The proposed formulations offer significantly faster computation times compared to tabulated/interpolated data and an accurate reconstruction of the viscoelastic frequency response. They also link the model coefficients with critical sections of the data, such as the gradient of the slope in the storage modulus, or the peak values in loss tangent and loss modulus. One of the models is based on piecewise polynomial fitting and offers versatility by increasing the number of polynomial functions used to achieve better fitting, but with additional pre-processing time. The other model uses a pair of logistic-bell functions and provides a robust fitting capability and the fastest identification, as it requires a reduced number of parameters. Both models offer good correlations with measured data, and their computational efficiency was demonstrated via implementation in Persson’s friction model.

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This study focuses on the creation of an isothermal elastic model to highlight, through stresses, the occurrence of plastic deformation in certain crank angles under extreme dry conditions inside an internal combustion engine. The stresses that are exported from this analysis are pointing out not only the necessity for an elastoplastic model to be created, but also the importance of predicting the correct friction coefficient, as pointed out by both the contact surface stress and those in depth of the two bodies in contact. A comparison between two coefficients of frictions and one frictionless case is conducted. The comparison between the finite element model and the adhesion mathematical model of Johnson, Kendall and Roberts (JKR), seals the importance of the interaction forces, acting on the common solid surface, in the pursuit of defining a propriate contact patch. Furthermore, a three-dimensional model is proposed for further investigation, highlighting the importance of modelling surface’s micro asperities for a solid stress analysis.