Grinding is regularly conducted on railway tracks to prevent crack propagation and surface deterioration. However, grinding can introduce roughness on rail surfaces, potentially leading to stress and strain concentration that increase the likelihood of crack initiation. This paper proposes the utilization of surface roughness obtained by replicating the ground rail surface to assess its impact on train wheel-rail interactions. A novel approach which integrates the replicated roughness into an elastoplastic contact model, allows for a detailed assessment of its effects on contact pressure, and residual strain and stress distributions. The findings highlight the importance of considering surface roughness in predictive maintenance planning for railway infrastructure, as it can significantly influence the structural integrity and long-term performance of the track system.

Many mechanical systems including rolling/sliding parts, require traction data across a spectrum of operating conditions to predict their motion effectively. Numerous studies have examined the thermal effects and shear-thinning concerning the traction curve, but only a few have focused on the traction coefficient in the linear isothermal regime for low SRR. In this work, we investigate traction coefficient characteristics of EHL point contacts in the linear isothermal regime, over a wide range of operational conditions. To this end, we conduct numerical simulations utilizing a fully-coupled finite element-based model, resulting in a prediction formula for the traction coefficient slope. With this formula, the traction coefficient slope could be predicted for the operating conditions considered.

This paper introduces an optimized computational domain for fully flooded circular elastohydrodynamic lubrication (EHL) contacts, enhancing the accuracy of numerical calculations of pressure and oil film thickness. First, the computational domain was configured based on Kapitza's analytical solution. Then, a resolution sensitivity study for the mesh of the 2D computational domain for the Reynolds equation was conducted to investigate the effect of mesh resolution on the accuracy of the numerical solution. Subsequently, the impact of the size of the full 3D computational domain on the simulation's accuracy and computational efficiency was analyzed. The main result is the 3D computational domain, which automatically adapts to operating conditions within the piezoviscous rigid, the isoviscous rigid, the piezoviscous elastic, and the isoviscous elastic regions, as well as in the transition regions between them. This results in a model which provides accurate predictions across a wide range of operational conditions. Another outcome is a new approximate expression for the central oil film thickness, showing a maximum relative difference of less than 4.6% compared to the numerical model.

Archard’s wear law encounters challenges in accurately predicting wear damage and volumes, particularly in complex situations like asperity–asperity collisions. A modified model is proposed and validated, showcasing its ability to predict wear in adhesive contacts with better accuracy than the original Archard’s wear law. The model introduces an improved wear coefficient linked to deformation energy, creating a spatially varying relationship between wear volume and load and imparting a non-linear characteristic to the problem. The improved wear model is coupled with the Boundary Element Method (BEM), assuming that the interacting surfaces are semi-infinite and flat. The deformation energy is calculated from the normal contact pressure and displacements, which are the common outputs of BEM. By relying solely on these outputs, the model can efficiently predict the correct shape and volume of the adhesive wear particle, without resorting to large and often slow models. An important observation is that the wear coefficient is expected to increase based on the accumulated deformation energy along the direction of frictional force. This approach enhances the model’s capability to capture complex wear mechanisms, providing a more accurate representation of real-world scenarios.

Increasing engine power to volume density is under investigation and being analysed extensively. Turbocharger, which is used to boost volumetric efficiency, also raises cylinder temperature and pressure, thus resulting in thermal distortions and reducing clearances in tribo-contacts, thereby compromising engine life. Thermal barrier coatings (TBCs) have shown potential to provide remedies to reduce heat losses, hazardous emissions, and heat flow toward the piston skirt in an internal combustion engine. In this study, a detailed thermo-mechanical analysis was performed for a diesel engine piston with a novel yttrium barium zirconate (YBZ) coating and then compared with other TBCs with varying thicknesses. The results revealed a notable decrease in piston substrate surface temperature when coated with various TBCs, with YBZ coating demonstrating superior performance over others. The 0.2 mm coating of YBZ-coated piston exhibited significant reductions of 15% and 10.3% in temperature and thermal stress respectively, thus enhancing piston durability. The better performance of the novel YBZ coating could be attributed to its stable thermal and elastic properties and lower thermal conductivity than other TBC materials. YBZ coating provides a promising solution to improve engine efficiency while extending engine life, making it an attractive option for the automotive industry.

We consider pressure-driven flow between adjacent surfaces, where the fluid is assumed to have constant density. The main novelty lies in using implicit algebraic constitutive relations to describe the fluid’s response to external stimuli, enabling the modeling of fluids whose responses cannot be accurately captured by conventional methods. When the implicit algebraic constitutive relations cannot be solved for the Cauchy stress in terms of the symmetric part of the velocity gradient, the traditional approach of inserting the expression for the Cauchy stress into the equation for the balance of linear momentum to derive the governing equation for the velocity becomes inapplicable. Instead, a non-standard system of first-order equations governs the flow. This system is highly complex, making it important to develop simplified models. Our primary contribution is the development of a framework for achieving this. Additionally, we apply our findings to a fluid that exhibits an S-shaped curve in the shear stress versus shear rate plot, as observed in some colloidal solutions.

Of the medals awarded during the Winter Olympics Games, most are awarded for sports involving cross-country (XC) skiing. The Double Poling (DP) technique, which is one of the sub-techniques used most frequently in XC skiing, has not yet been studied using simulations of the ski–snow contact mechanics. This work introduces a novel method for analysing how changes in the distribution of pressure on the sole of the foot (Plantar Pressure Distribution or PPD) during the DP motion affect the contact between the ski and the snow. The PPD recorded as the athlete performed DP, along with an Artificial Neural Network trained to predict the geometry of the ski (ski-camber profile), were used as input data for a solver based on the boundary element method, which models the interaction between the ski and the snow. This solver provides insights into how the area of contact and the distribution of pressure on the ski-snow interface change over time. The results reveal that variations in PPD, the type of ski, and the stiffness of the snow all have a significant impact on the contact between the ski and the snow. This information can be used to improve the Double Poling technique and make better choices of skis for specific snow conditions, ultimately leading to improved performance.

The nature of snow and the ever-changing environment makes measuring friction on snow and ice challenging. Additionally, due to the low friction involved, the equipment used must exhibit high sensitivity. Previous investigations of ski–snow friction have ranged from small-scale model experiments performed in the laboratory to experiments with full-sized skis outdoors. However, few have been conducted under conditions similar to those encountered during actual skiing. Here, we present a novel sled tribometer which provides highly reproducible coefficient of friction (COF) values for full-sized skis gliding at relevant speeds (approximately 5.9 m/s) in a controlled indoor environment. The relative standard deviation (RSD) of the COF is as low as 0.5%. The continuous recording of velocity allows for innovative investigations into COF variations when skis are permitted to free-glide in a natural setting. Different methods of analysing the results are presented which shows that the precision is not a single number, but a function of the range of velocities over which the average COF is calculated.

Wear is a complex phenomenon taking place as two bodies in relative motion are brought into contact with each other. There are many different types of wear, for example, sliding, fretting, surface fatigue, and combinations thereof. Wear occurs over a wide range of scales, and it largely depends on the mechanical properties of the material. For instance, at the micro-scale, sliding wear is the result of material detachment that occurs due to fracture. An accurate numerical simulation of sliding wear requires a robust and efficient solver, based on a realistic fracture mechanics model that can handle large deformations. In the present work, a fully coupled thermo-mechanical and meshfree approach, based on the momentum-consistent smoothed particle Galerkin (MC-SPG) method, is adapted and employed to predict wear of colliding asperities. The MC-SPG-based approach is used to study how plastic deformation, thermal response, and wear are influenced by the variation of the vertical overlap between colliding spherical asperities. The findings demonstrate a critical overlap value where the wear mechanism transitions from plastic deformation to brittle fracture. In addition, the results reveal a linear relationship between the average temperature and the increasing overlap size, up until the critical overlap value. Beyond this critical point, the average temperature reaches a steady-state value.