Tribology Letters

http://link.springer.com/journal/11249

List of Papers (Total 148)

The Influence of Aluminium–Silicon Alloy on ZDDP Tribofilm Formation on the Counter-Surface

In order to reduce vehicle weight and thus improve fuel economy, aluminium (Al) alloys have been increasingly adopted as contact surfaces such as piston skirts and cylinder liners in current engines. In general, hypereutectic Al–Si alloys are used, in which hard silicon grains are embedded in a softer Al–Si single phase matrix. It is reported that after rubbing, the matrix is ...

The Influence of Base Oil Properties on the Friction Behaviour of Lithium Greases in Rolling/Sliding Concentrated Contacts

This study investigates the influence of base oil type and viscosity on the frictional behaviour of lithium-thickened bearing greases. A series of model lithium greases were manufactured by systematically varying viscosity and type of base oil, so that the influence of a single base oil property could be studied in isolation. In addition, selected greases were blended with oleic ...

Meeting the Contact-Mechanics Challenge

This paper summarizes the submissions to a recently announced contact-mechanics modeling challenge. The task was to solve a typical, albeit mathematically fully defined problem on the adhesion between nominally flat surfaces. The surface topography of the rough, rigid substrate, the elastic properties of the indenter, as well as the short-range adhesion between indenter and ...

Positron Annihilation Studies of the Near-Surface Regions of Niobium before and after Wear Treatment

The positron annihilation studies of well-annealed niobium samples after dry sliding or sandblasting are reported. These treatments modify surface and subsurface regions introducing crystalline defects, which are extended beneath the surface of the sample at a depth of about 140 µm for the highest applied load of 50 N. These defects can be identified as dislocations with jogs or ...

Pin-on-Disc Testing of Low-Metallic Friction Material Sliding Against HVOF Coated Cast Iron: Modelling of the Contact Temperature Evolution

Pin-on-disc (PoD) testing is widely used to investigate the sliding behaviour of materials and relevant wear mechanisms under different tribological conditions. The approach has been also profitably applied to the characterization of materials for brake systems to obtain specific information on the wear mechanisms. In the present study, the transient thermal analysis of a pin made ...

Study of Permanent Shear Thinning of VM Polymer Solutions

The ultrashear viscometer (USV) has been adapted and employed to investigate the permanent shear thinning of polystyrene solutions in a series of phthalate ester base fluids. The permanent shear stability index based on viscosities measured at 106 s−1, PSSI(106), has been found to be a convenient way to express the magnitude of permanent shear thinning. When comparing permanent ...

Atomistic Insights on the Wear/Friction Behavior of Nanocrystalline Ferrite During Nanoscratching as Revealed by Molecular Dynamics

Using embedded atom method potential, extensive large-scale molecular dynamics (MD) simulations of nanoindentation/nanoscratching of nanocrystalline (nc) iron have been carried out to explore grain size dependence of wear response. MD results show no clear dependence of the frictional and normal forces on the grain size, and the single-crystal (sc) iron has higher frictional and ...

Texture Design for Reducing Tactile Friction Independent of Sliding Orientation on Stainless Steel Sheet

Surface texture is important for contact mechanical and tribological phenomena such as the contact area and friction. In this research, three different types of geometrical microstructures were designed and fabricated by pulsed laser surface texturing as semi-symmetric (grooved channel), asymmetric fractal (Hilbert curve), and symmetric patterns (grid). A conventionally finished ...

Lubricating Grease Flow in a Double Restriction Seal Geometry: A Computational Fluid Dynamics Approach

In this paper, numerical simulations of lubricating grease flow in the grease pocket of a double restriction seal geometry using computational fluid dynamics are presented. The grease is treated as a single-phase Herschel–Bulkley fluid with different rheological properties corresponding to NLGI grade 00, 1 and 2. The numerical code and rheology model have been validated with a ...

The Role of Temperature and Frequency on Fretting Wear of a Like-on-Like Stainless Steel Contact

The influences of environmental temperature and fretting frequency on the mechanisms and rates of wear in a like-on-like 304 stainless steel contact were examined and mainly attributed to changes in the mechanical response of the bulk material and to changes in the behaviour of the oxide debris formed in the fretting process. At low temperatures, wear proceeds by continual oxide ...

Influence of NO x and Air on the Ageing Behaviour of MoDTC

Molybdenum dialkyldithiocarbamates (MoDTCs) are very effective friction modifier additives for use in engine oils and other lubricants. However, as engine oils age during extended drain intervals, MoDTCs can lose some or all of their ability to reduce friction and this is generally believed to result from their oxidative degradation. In this study, MoDTC solutions in base oil have ...

Formulation of Presliding Domain Non-local Memory Hysteretic Loops Based Upon Modified Maxwell Slip Model

In this paper, we investigate formulation of non-local memory effect hysteretic loops in presliding domain of friction by examining the dynamic responses of a single-degree-of-freedom friction oscillator. We modify the Maxwell slip model introducing characteristic features of asperities and perform detailed examination of the system from two perspectives. The first one, termed by ...

A Deterministic Stress-Activated Model for Tribo-Film Growth and Wear Simulation

A new model was developed for the simulation of growth and wear of tribo-chemical films by combining a boundary element method-based contact model and a stress-activated Arrhenius tribo-film growth equation. Using this methodology, it is possible to predict the evolution and steady-state thickness of the tribo-film (self-limitation) at various operating conditions. The model was ...

Influence of Different Application of Lubricants on Wear and Pre-existing Rolling Contact Fatigue Cracks of Rail Materials

Rolling contact fatigue (RCF) of rail can be a significant problem affecting safety and maintenance. Rail materials have been optimized to reduce it, but not enough is known about how friction management products applied to the rail affect crack growth. This study presents experimental results carried out to explore the influence of different lubricants and application orders on ...

Development of a Tribological Test Programme Based on Press Hardening Simulations

Press hardening is widely utilized to form ultra-high-strength steels characterized by a high strength-to-weight ratio for automotive components. Press hardening processes include heating boron–manganese steels to austenite phase, forming the steels at a high temperature, and cooling the formed blanks until the martensite phase is reached . However, press hardening processes lead ...

Influence of Post-treatment on the Microstructural and Tribomechanical Properties of Suspension Thermally Sprayed WC–12 wt%Co Nanocomposite Coatings

The potential to improve the tribomechanical performance of HVOF-sprayed WC–12Co coatings was studied by using aqueous WC–12Co suspensions as feedstock. Both as-sprayed and hot-isostatic-pressed (HIPed) coatings were studied. Mathematical models of wear rate based on the structure property relationships, even for the conventionally sprayed WC–Co hardmetal coatings, are at best ...

Positron Annihilation and Complementary Studies of Stainless Steel Exposed to Sandblasting at Different Angles

Defect studies in subsurface zone in stainless steel 304 AISI samples exposed to sandblasting were performed using positron annihilation spectroscopy techniques. Samples were sandblasted with a different impact angle. Conventional experiments based on positrons emitted directly from the radioactive source allowed us to detect vacancies on the dislocation edges in all samples; ...

Study of the Falling Friction Effect on Rolling Contact Parameters

The existence of a wheel–rail friction coefficient that depends on the slip velocity has been associated in the literature with important railway problems like the curving squeal and certain corrugation problems in rails. Rolling contact models that take into account this effect were carried out through the so-called Exact Theories adopting an exact elastic model of the solids in ...

Quantitative Viscosity Mapping Using Fluorescence Lifetime Measurements

Lubricant viscosity is a key driver in both the tribological performance and energy efficiency of a lubricated contact. Elastohydrodynamic (EHD) lubrication produces very high pressures and shear rates, conditions hard to replicate using conventional rheometry. In situ rheological measurements within a typical contact are therefore important to investigate how a fluid behaves under ...

Studies of the Influence of Temperature and the Energy State of the Surface Layer of Adsorbents on Wall Effects in Soap-Based Greases

This paper presents the results of studies of wall effects in commercial soap-based greases LT4-S2 and HUTPLEX EP-2, thickened with, respectively, lithium 12-hydroxystearate and overbased calcium sulfonate. The studies were conducted in the presence of five different materials: copper alloy C11000, bronze B476, EPDM rubber and PTFE and PU thermoplastics. The influence of the energy ...

Indentation Hardness Measurements at Macro-, Micro-, and Nanoscale: A Critical Overview

The Brinell, Vickers, Meyer, Rockwell, Shore, IHRD, Knoop, Buchholz, and nanoindentation methods used to measure the indentation hardness of materials at different scales are compared, and main issues and misconceptions in the understanding of these methods are comprehensively reviewed and discussed. Basic equations and parameters employed to calculate hardness are clearly ...

Effect of Base Oil Structure on Elastohydrodynamic Friction

The EHD friction properties of a wide range of base fluids have been measured and compared in mixed sliding–rolling conditions at three temperatures and two pressures. The use of tungsten carbide ball and disc specimens enabled high mean contact pressures of 1.5 and 2.0 GPa to be obtained, comparable to those present in many rolling bearings. The measurements confirm the importance ...

Elastic Waves of a Single Elasto-Hydrodynamically Lubricated Contact

Elastic waves are widely used for condition monitoring of rolling element bearings through vibration or acoustic emission measurements . While vibration signals are understood to a high degree due to many scientific investigations as well as a long history of usage in the field, acoustic emission signals of rolling element bearings are poorly understood. Therefore, this ...