Slip and fall accidents are a major occupational health concern. Important factors affecting shoe-floor friction is critical to identifying and resolving unsafe surfaces and designing. Experimental studies have indicated that several factors including floor roughness, sliding speed and shoe materials affect shoe-floor friction although the precise nature of the mechanism behind this phenomenon is not well understood. In addition, recent studies have suggested that boundary lubrication is highly relevant to slipping and that adhesion and hysteresis are the main contributing factors to boundary lubrication. The purpose of this study is to perform the numerical simulations to analyze the effects of floor roughness (asperity height), sliding speed and material properties on ratio of real area of contact and normal force (relevant to adhesion friction) and hysteresis friction for a viscoelastic shoe material interacting with a hard floor surface. A 3D shoe model and 3D vinyl floor model was simulated with speed 0.01 m/s, 0.5 m/s, 0.75 m/s and 1 m/s in three different floor surfaces. The material property was also varied in the numerical simulations. The study showed that roughness affects both the hysteresis and adhesion friction whereas sliding speed and material property affects the adhesion friction only. The dependence of adhesion and hysteresis friction on roughness, sliding speed and material property is useful in understanding the shoe-floor friction phenomenon and development of slip resistant sports and work shoes.
In the present investigation, sliding experiments were conducted using pins made of pure Al, Al-4Mg alloy, Al-8Mg alloy, Mg-8Al alloy and pure Mg against steel plates of various surface textures using a pin-on-plate apparatus under both dry and lubricated conditions. The primary focus of the study was to investigate the influence of alloying elements on the coefficient of friction and transfer later formation in Al-Mg systems. The morphologies of the worn surfaces of the pins and the formation of transfer layer on the counter surfaces were observed using a scanning electron microscope. It was observed for a given surface texture that the alloying element addition decreased the average coefficient of fiction to lower values under both dry and lubricated conditions. For a given material pair, the coefficient of friction and formation of transfer layer depend on the surface texture of the hard surfaces.
Abstract Natural oils exhibit effective lubricating properties, such as low friction, high viscosity, and improved wear resistance, making them suitable for a range of applications in automotive, industrial machinery, and aerospace systems. Their superior lubricating performance, combined with their eco-friendly nature, aligns with the growing need for sustainable solutions in the face of stringent environmental regulations. In addition to the base natural oil, addition of a particulate to the natural lubricant can further boost the tribological performance. In the current investigation, the tribological performance of the avocado oil with different solids lubricant additives of different particle sizes from 70 nm to 5 µm and their combinations were evaluated by a pin-on-disk setup. A strong influence of particle type was observed where only hBN and MoS2 in the avocado lubricant mixture provided superior tribological properties compared to neat avocado oil. Results also confirmed that the smaller particle sizes of hBN and MoS2 are beneficial to reduce coefficient of friction and wear. The influence of particle size was further analyzed by mixing multi-particle type and size that confirms that smaller particles, particularly 70 nm hBN can provide lower friction and wear when mixed with coarser hBN or MoS2 particles. A fractal dimension was also defined to quantify the relationship between the initial surface roughness and partice size of the hBN solid lubricants in the lubricant mixture.
Surface texture influences friction and transfer layer formation during sliding. In the present investigation, various kinds of surface texture with varying roughness were produced on steel plates. Pins made of Mg-8Al alloy were then slid against the prepared steel plates using inclined pin-on-plate sliding tester to understand the role of surface texture of the harder surface and load on coefficient of friction and transfer layer formation under both dry and lubricated conditions. Normal loads were varied from 1 to 120 N during the tests. Tests were conducted at a sliding velocity of 2 mm/s in ambient conditions. Scanning electron micrographs of the surfaces in contact for both the pins and plates were obtained to understand the morphology of the transfer layer. Surface roughness parameters of the steel plate were measured in the direction of the sliding on the bare surface away from the wear tracks using an optical profilometer. It was observed that the coefficient of friction and transfer layer formation are strongly dependent on surface texture and independent of surface roughness (Ra) of steel plate. Among the surface roughness parameters, the mean slope of the profile was found to explain the variations best. The plowing component of friction was highest for the surface that promotes plain strain conditions while it was lowest for the surface that promotes plane stress conditions near the surface.
Surface topography influences friction and transfer layer formation during sliding. In the present investigation, various kinds of surface topography were produced on steel plates. Pins made of metals (pure Al, Cu and Pb) and alloys (Al-4Mg and Al-8Mg) were then slid against prepared steel plates using inclined pin-on-plate sliding tester to understand the role of surface topography of harder surface and load on friction and transfer layer formation under both dry and lubricated conditions. It was observed that the transfer layer formation and coefficient of friction along with its two components, namely adhesion and plowing, are strongly dependent on surface topography and independent of surface roughness (Ra). The plowing component of friction was highest for the surface that promotes plane strain conditions and lowest for the surface that promotes plane stress conditions near the surface.
Graphene oxide (GO), a derivative of graphene, has attracted significant attention in tribological applications due to its unique structural, mechanical, and chemical properties. This review highlights the influence of GO and its composites on friction and wear performance across various engineering systems. The paper explores GO’s key properties, such as its high surface area, layered morphology, and abundant functional groups. These features contribute to reduced shear resistance, tribofilm formation, and improved load-bearing capacity. A detailed analysis of GO-based composites, including polymer, metal, and ceramic matrices, reveals those small additions of GO (typically 0.1–2 wt%) result in substantial reductions in coefficient of friction and wear rate, with improvements ranging between 30–70%, depending on the application. The tribological mechanisms, including self-lubrication, dispersion, thermal stability, and interface interactions, are discussed to provide insights into performance enhancement. Furthermore, the effects of electrochemical environment, functional group modifications, and external loading conditions on GO’s tribological behavior are examined. Despite these advantages, challenges such as scalability, agglomeration, and material compatibility persist. Overall, the paper demonstrates that GO is a promising additive for advanced tribological systems, while also identifying key limitations and future research directions.
When frictional sliding is initiated, the coefficient of friction is often high during the initial transient running-in process. After that, the coefficient of friction reaches its stationary value. Running-in is interpreted as friction-induced self-organization stage in that two sliding surfaces adjust to each other due to surface roughness evolution. Shannon entropy was proposed as a surface roughness parameter, and its decrease can be used as a simple test for self-organization. Sliding experiments were conducted on the hard steel plate using a soft Al-Mg alloy pin under both dry and lubricated conditions. Based on the results of the surface profile evolution, obtained by an optical profilometer, during running-in, we discuss change of Shannon entropy for various surface textures. Various textures which are characterized in terms of roughness parameters were produced on the steel plates. We compare how self-organization occurs for different textures during running-in stage.
This study investigates the effects of Laser Shock Peening (LSP) on residual stress distribution and surface deformation using a Finite Element Method (FEM) model. LSP is a surface treatment process that generates compressive residual stress by applying high-energy laser pulses over nanosecond timescales. The study aims to analyze the impact of key parameters, specifically laser spot overlap rate and power density, on the induced residual stress and surface deformation. A Design of Experiment (DOE) approach was used to systematically vary these parameters. These simulations were performed using the ANSYS Explicit Dynamics FEM with a Johnson-Cook material model to capture the nonlinear constitutive behavior. The research analyzes the distribution of residual stress and surface deformation caused by LSP. Increasing laser spot overlap and power density leads to higher compressive residual stress and surface deformation, revealing two distinct behavioral outcomes: either deep compressive stress with minimal deformation or a transition from compressive to tensile stress followed by significant surface deformation and a subsequent return to compressive stress. The results demonstrate strong agreement with existing experimental data presented in the literature. This study contributes novel insights into the interaction between LSP parameters and their effects on material properties, with implications for understanding LSP techniques in practical applications. The triangular pulse model and dual-overlap analysis offer a novel simulation strategy for optimizing LSP parameters in stainless steel.
Understanding the fundamental tribology associated with the cutting of rock under extremely high pressure and high temperature (HPHT) conditions are extremely important in mining and drilling operations. In this paper, a rock fragmentation process is simulated during mechanical cutting of rock using an explicit finite element code, LS-DYNA. In the simulation, a cutting tool is orthogonally moved against a stationary rock material. Rock material properties have been incorporated using an advanced damage constitute material model. Simulations were performed for various rake angles at different cutting velocities and cutting depths. The variation of cutting forces, stresses, rock fragment morphology and the character of fragment formation have been investigated. Overall, the results indicate that the explicit FEM is a powerful tool for simulating rock cutting and the fragmentation process. More specifically, the separation of rock fragments from the base rock slab was accurately predicted using the numerical model. The cutting forces and rock fragment characteristics were strongly influenced by rake angel when compared to cutting tool velocities for a given depth of cut. This information is shown to be highly pertinent to better understanding cutting rates and tool wear.
