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In this study, the lubricated friction and wear associated with diamond-like coatings (DLCs) of amorphous hydrogenated carbon (a-C:H) and hydrogen-free tetrahedral amorphous carbon (ta-C) were comparatively analyzed. The effects of load and sliding distance on the wear and friction behaviors of the coatings were studied under a boundary-lubrication condition using a poly-alpha-olefin base oil. The...
The replacement of cutting tools is important when shield tunneling in abrasive soils. The task is performed based on an assessment of the degree of cutting tool wear. The wear of cutting tools is influenced by many factors, such as the soil abrasiveness, shield machine operational parameters, and tool sliding distance. The representation of the uncertainty in these factors is the primary problem...
In this work, TiB2 particulate reinforced copper matrix composites were fabricated by casting method, based on in situ precipitation reaction between B and Ti elements to form TiB2 particles in molten copper. The microstructures of the Cu-TiB2 composites were characterized using SEM and TEM. The results show that TiB2 particles are successfully formed in the copper matrix and the interfaces between...
The erosion behavior of EB-PVD thermal barrier coatings (TBCs) with real morphology was investigated based on finite element (FE) simulation. Firstly, an FE modeling method was developed to establish a geometric numerical model using a scanning electron microscope. Secondly, an empirical correlation between the depth of penetration and some characteristic parameters of the erodent particle (i.e. diameter,...
Employing a broad parameter study, friction and wear properties of amorphous carbon coatings (a-C), tetrahedral amorphous carbon coatings (ta-C) and single crystalline diamond were investigated in boundary lubrication regime, using an oscillating ball-on-flat test setup with engine oil, glycerol, and glycerol monooleate (GMO) lubrication. Ultra-low friction (µ < 0.04) was confirmed with glycerol...
In this study, the effects of refurbishing on rolling contact fatigue (RCF) in case carburized AISI 8620 steel were experimentally and analytically investigated. A thrust bearing test apparatus (TBTA) was designed and developed to simulate RCF. Initial RCF tests were conducted on AISI 8620 steel specimens to determine the baseline for pristine. Then new specimens were exposed to fatigue cycles equal...
An ultrasonic nanocrystal surface modification (UNSM) technique has been used to treat AISI 52100 steel specimens and thrust ball bearing raceways. Tribological performances of untreated specimens were compared to UNSM-treated specimens in reciprocating sliding and rolling/sliding contact under boundary lubricated conditions. Friction and wear coefficients, micropitting, and changes in surface profiles...
The erosion of a surface by a sediment-laden flow is an inherently multiscale phenomenon which includes physical interactions covering many orders of magnitude in both length and time scales. Conforming to the nature of the problem, we propose a novel multiscale model for simulating this complex process. On the one hand, a macroscale model encompassing the whole domain of interest solves the turbulent...
Wear debris analysis (WDA) is an effective machine health monitoring technique in which wear debris attributes can reveal wear mechanisms and particle colours can be used to detect oxidation. However, most of the existing approaches to WDA are based on analytical ferrography. Online wear debris typing is still difficult to achieve because of the low resolution of online particle images. In this work,...
The goal of this work is to increase understanding of plastic deformation of the pearlitic microstructure in the wheel/rail contact. The tridimensional gradient of microstructure below the running band of a worn R260 rail is investigated using multi-scale approach based on microstructural observations by optical and Scanning Electron Microscopy (SEM-FEG), microindentation and Electron BackScatter...
This paper looks into the influences of solution treatment on the cavitation erosion and corrosion resistances of a CrMnNi austenitic stainless steel. Cavitation erosion pit formation is mainly associated with twin boundaries, slip lines and martensite traces (ε and α′). These pits subsequently grow both across slip lines and martensite traces and along twin boundaries, eventually coalescing to form...
The surface roughness of a chemical mechanical polishing (CMP) pad provides microscopic asperities where the actual polishing takes place. Thus, the roughness should be maintained in a proper regimen to obtain stable CMP process quality. A conditioner is a key consumable in the CMP process because it maintains the roughness of the CMP pad surface against surface glazing or flattening during polishing...
The third body formed in a contact between HS25 cobalt-based superalloy versus ceramic under fretting wear (small reciprocating displacements) was investigated. This tribomaterial, commonly called “glaze layer”, was created from nanosized, compacted and sintered wear debris and adheres on both rubbed parts. The glaze layer was investigated both from tribological and rheological points of view. In...
The null characteristics of hydraulic spool valves change significantly due to solid particle erosion. In the present work, a numerical model has been established to predict the material removal rate and the worn profile evolution with erosion in hydraulic spool valves. The particle trajectories are solved by a stochastic separated flow model based on eddy interaction, and the squeeze film is included...
Polygonization wear (PolyW) is a form of wear observed on railroad wheels that is characterized by a change in the morphology of surface features from circular to non-circular due to eccentricity of wheel motion and the wheels’ rotational inertia. Thus, PolyW tends to form under conditions of vertical/horizontal vibrations between wheels and rails. The current experimental investigation in rolling...
Traditional metal-polymer sliding bearings have low cost and may operate under conditions of dry sliding friction; however, the wear rate of such bearings can be unacceptably high. This work tests the hypothesis that applying a layer of bulk oriented, polymer-based nanocomposites can reduce both the friction coefficient and wear rate. Bulk oriented nanocomposites based on ultra-high molecular weight...
The aim of this paper is to accurately predict the evolution of wheel profile wear and related vehicle dynamics for high-speed trains by considering the stochastic wheel/rail interactions, which experience quite variants with time and along long distant high-speed lines in China. These variants include the rail profiles, track geometries, track irregularities and interface characteristics associated...
The longevity of metal-on-polyethylene prosthetic hip joint bearings, in which a CoCrMo femoral head articulates with a polyethylene liner, is often limited by polyethylene wear and osteolysis caused by polyethylene wear particles. Current approaches to reduce polyethylene wear include improving the mechanical properties of the polyethylene liner, and/or manufacturing ultra-smooth articulating surfaces...
The use of polyethylene (PE) liners for protection against wear has become of interest in applications dealing with abrasive slurries, for example in the minerals processing industry. The present study aims at studying the influence of various operating conditions on the erosive wear by slurry of low-density polyethylene and high-density polyethylene samples, manufactured by either rotational molding...
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