This study is an investigation of the impact of grinding-generated surface roughness on the wear and fatigue life of rails. The grinding process, essential for rail maintenance, creates a rough surface that significantly influences wheel/rail contact conditions. Using a combined experimental and numerical approach, this work replicates and integrates grinding-generated roughness into an elastoplastic rolling contact model. To evaluate the effects of surface roughness on rail degradation, Archard's wear equation is applied for wear assessment, while fatigue is analysed using the Jiang-Sehitoglu fatigue parameter. The results show that rough surfaces induce localised high stresses and plastic strains, accelerating material degradation, particularly in early rolling cycles. In contrast, smoother surfaces exhibit more stable plastic strain evolution over fewer cycles. Additionally, the grinding-generated roughness significantly increases the damage accumulation, highlighting its role in reducing rail life. These findings emphasize the need to incorporate surface roughness into predictive maintenance models and optimise grinding practices to ensure rail longevity and operational reliability.

Recent advances in modeling have enhanced our ability to make quantitative predictions for tribological phenomena, thereby unraveling relevant mechanisms. Algorithmic innovations, including those based on multiscale methods and machine learning, have been especially impactful, for example in overcoming long-standing bottlenecks that hinder simulations of systems with strong coupling across disparate scales. However, traditional modeling approaches, such as boundary-element techniques, have also progressed and continue to yield new insights. This article reviews developments from the past decade, examining how both new and established methods have deepened our understanding of experimental results and have furthered theoretical approaches in key tribological areas, including contact mechanics, lubrication, metal friction, and tribo-chemistry. Selected applications, such as tunable interfaces and energy harvesting, illustrate the broad influence of recent developments on fields beyond tribology itself.

A simplified model is derived for pressure-driven flow between adjacent surfaces of materials modeled as seemingly viscoplastic or truly viscoplastic. The material response to external forces is traditionally described by constitutive relations in which the extra stress tensor $S$ is expressed as a function of the symmetric part of the velocity gradient $D$. However, for viscoplastic materials, $S$ cannot, in general, be written as a function of $D$, whereas $D$ can be expressed in terms of $S$. Motivated by this observation, a model based on constitutive relations of the form $D = f(S)$ is proposed, leading to a system of first-order partial differential equations. A local Poiseuille law is also formulated, and a reduced-dimensional equation for the pressure is derived. Explicit velocity profiles are obtained for selected cases.

Understanding contact between rough surfaces undergoing plastic deformation is crucial in many applications. We test Persson's multiscale contact mechanics theory for elastoplastic solids, assuming a constant penetration hardness. Using a numerical model based on the boundary element method, we simulate the contact between a flat rigid surface and an elastic-perfectly plastic half-space with a randomly rough surface. The theory's predictions for elastic, plastic, and total contact area agree quantitatively with the numerical results. The simulations also support the boundary conditions assumed in the theory, namely that the stress probability vanishes at both zero and yield stress. These findings reinforce the validity of the theory for systems with constant hardness.

Introduction: Understanding how skiers and ski technicians perceive snow conditions and ski preparation is essential for optimising glide performance in cross-country (XC) skiing. While tribological research has established how snow microstructure, water-film formation, and ski-snow interactions influence friction, comparatively little is known about how skiers and ski technicians interpret these mechanisms in practice.

Methods: We therefore conducted a nationwide questionnaire study (n = 249) to quantify perceptual consensus on ten topics related to snow type, glide determinants, ski preparation, and skier-equipment interaction. Responses were analysed using van der Eijk's agreement coefficient for ordinal data and Cliff's delta to evaluate expert (n = 20) versus non-expert (n = 229) differences.

Results: Agreement varied systematically across topics: the highest consensus was found for perceived ski speed on different snow types and structure selection, while the lowest was observed for glide determinants, paired glide tests involving skier mass, and double-poling positioning. Experts showed higher within-group agreement for perceived ski speed in skate-skiing and on moist transformed snow, and they consistently rated ski camber as more important than non-experts did.

Discussion: These findings highlight empirically developed know-how within the skiing community, such as shared heuristics for snow-type assessment and preparation, and systematic expertise-related differences in prioritising fundamental ski characteristics (e.g., camber). As such, they can be used for targeted education and to inform future applied tribology research.

Understanding the contact between rough surfaces undergoing plastic deformation is crucial in many applications. We study the effect of plastic deformation on the surface separation between two solids with random roughness. Assuming a constant penetration hardness, we propose an iterative smoothing procedure (akin to elastoplastic “shakedown”) within Persson's multiscale contact mechanics theory to obtain the average surface separation by applying the elastic formulation to an effective power spectrum that accounts for plastic smoothing. Deterministic numerical simulations based on the boundary element method are used to validate the procedure and show good agreement with the theoretical predictions. The treatment also provides a route to incorporate plastic stiffening of the roughness as the stress state becomes increasingly hydrostatic at large plastic deformation.

Elite performance in Olympic winter sports depends on the interplay among the athlete, equipment, and the snow or ice. This naturally evolves with temperature, humidity, wind, preparation, and contact between the equipment and its surface. Together, these factors continuously rebalance the forces of gravity, aerodynamic drag, and friction, requiring athletes, coaches, and organizers to adapt technique, equipment, and surface management, e.g., snow grooming and salting, ice resurfacing or pebbling, and rink climate control. This narrative review (SANRA-guided) synthesizes the scientific literature across four domains: (i) the evolution of equipment and athlete–surface interaction; (ii) the physics of resistive forces and targeted countermeasures; (iii) sensing and monitoring with robust, field-validated technologies and analytics; and (iv) the digitalization of coaching, officiating, and broadcasting. We integrate design and validation with sport regulations and governance. This includes the ban on fluorinated waxes, geometry and mass limits, and principles for data stewardship, model transparency, and fairness. A central component of this review is the assessment of quality aspects of technologies, including the assessment of ecological validity under field-specific conditions before their use in high-stakes coaching, medical, or officiating decisions. We conclude with actionable recommendations for Milano–Cortina 2026: (i) align equipment and surface preparation with expected regimes of drag and friction; (ii) deploy sensors and analytics with demonstrated accuracy, precision, and reliability; (iii) quantify uncertainty in key performance indicators; and (iv) treat federation rules as a priori design constraints. This approach enables innovation to deliver faster, safer, and more equitable outcomes in winter sport at Milano–Cortina 2026 and beyond.

With 62% of medals at the upcoming 2026 Winter Olympics in Milano-Cortina to be awarded in skiing disciplines and the remaining 38% in ice-based events, understanding the determinants of performance is critical. Despite extensive examination of athletes’ physiological, biomechanical, and psychological attributes, the role of tribology—particularly in understanding friction on snow and ice—has received less attention. This is a scientific perspective article outlining key tribological factors and highlighting their importance in Olympic winter sports. In skiing, optimising the ski–snow interaction requires a comprehensive understanding of how friction is influenced by snow crystal morphology, temperature, ski base material and structure, ski stiffness, skier technique, and environmental conditions. For ice-based events, friction is determined by a combination of ice surface roughness, temperature, and sport-specific preparation techniques, as well as equipment design (e.g. blade material and geometry, the running surface finish of curling stones) and athlete technique (e.g. angle of attack in speed skating, sweeping in curling). Ice preparation techniques further influence friction, with specific conditions tailored to each sport. In conclusion, advancements in Olympic winter sports have been significant. However, future breakthroughs in performance may lie in applying tribological insights to optimise the complex interactions between athletes, equipment, and the unique properties of snow and ice. This perspective article aims to guide future research by synthesising current understanding and identifying emerging challenges in winter sports tribology.

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.

Cross-country skiers employ various techniques, where the ski is exposed to different forces during the motion. This study utilized a novel sled tribometer to investigate the combined effects of load and positioning of the skier on the coefficient of friction (COF) between the skis and snow. Three different loads (40 kg, 80 kg and 120 kg) were applied to the sled, and the center of mass was systematically varied between three positions behind the binding position: 70mm (leaning forward), 140mm (centered) and 210mm (backward). A variety of skis were used, including different models of skate skis and one classic-style ski with grip wax. The results consistently demonstrated that increasing the load on the sled reduced the COF by up to 15% (from the lowest to highest load), regardless of the position of the center of mass. The position of the center of mass had a minimal effect on COF in most tests. An exception was observed when using grip wax, where a forward-leaning position combined with a heavy load significantly increased the COF (~ 8%) compared to what is expected without grip wax. This load-dependent reduction in the COF was observed across different skis and test sessions. The ski camber profile was measured for all skis in all configurations. In general, increasing the load increases the glide zone length but at the same time increasing the average pressure. The position of the center of mass has little to no effect on the rear glide zone but slightly alters the length and position of the front glide zone. While the mechanisms of friction are discussed, a complete understanding of these mechanisms has not yet been reached.