Wear Process Research Articles

Reliability modelling with uncertain threshold and fractional differential degenerate equation in uncertain environment

A dependent competitive failure model of Caputo uncertain fractional differential equation (UFDE) degradation with uncertain threshold is proposed. There are two main reasons for the failure of an equipment or system, long-term natural wear and the impact of external loads. Each shock will cause a sharp increase in wear. In the absence of fault data, the natural wear process is driven by a Caputo type of UFDE, and the external load is an uncertain renewal reward process. Three different shock models are considered and calculated the belief reliability of device according to uncertainty theory, taking the jet pipe servo control valve as an example, the proposed model is simulated, and the results show that the proposed model is effective.

Supplementation of Energy Drinks with Green Tea Extract: Effect on In Vitro Abrasive/Erosive Dentin Wear.

To investigate the effect of the supplementation of energy drinks with green tea extract on abrasive and erosive dentin wear. Six groups, each comprising 15 bovine dentin samples, were prepared, yielding a total of 90 samples. Erosion was performed by immersing the samples in Red Bull and Red Bull light with and without green tea extract. Tap water with and without green tea extract was used as the control groups. The samples were subjected to abrasive/erosive cycling for five days. The following cycling was performed daily: toothbrush abrasion (20 brushstrokes; 2.5 N); eight erosive cycles (2 min storage in the respective solutions); in between the erosive cycles, storage in artificial saliva (60 min) and again toothbrush abrasion (20 brushstrokes; 2.5 N). During the night, samples were again stored in artificial saliva. Abrasive/erosive dentin wear was measured using a stylus profilometer (µm, accuracy = 40 nm). The measured dentin loss results from the vertical position shift on the y-axis from base to final profile after the wear process in 2D. Pairwise comparisons between the groups were carried out using Wilcoxon signed-rank test. The following dentin wear (median [IQR]) was measured: Red Bull: 1.9 µm (0.5); Red Bull Light: 1.3 µm (0.3); Red Bull with green tea extract: 0.8 µm (0.3); Red Bull Light with green tea extract: 0.3 µm (0.5); Tap water with green tea extract: -0.2 µm (0.7); Tap water: -1.0 µm (1.2). The comparison of all tested groups to each other proved to be statistically significant (p < 0.05). The supplementation of energy drinks with green tea extract provide a protective effect against erosive/abrasive wear in vitro.

Effects of TiC on the Microstructure, Mechanical Properties, and Wear Behavior of E690 Steel Prepared by Laser Cladding

For this study, E690 steel claddings with different contents of TiC were prepared by laser cladding for revealing effects of TiC on microstructure, mechanical properties, and wear behavior of the cladded steel. The microstructure and mechanical properties of the cladded alloys were observed and measured. The wear resistance of the cladded alloys was tested using a ball-on-disc tribometer. The experimental results showed that TiC refined the grain of the cladded alloy obviously. However, excessive TiC could lead to the network-like distribution of submicro TiC particles in the claddings. The microhardness of the cladded alloy with 1% TiC increased to 418.5 ± 10.7 HV500, and yield strength and ultimate tensile strength (UTS) increased by 11% and 7% compared with those of the cladded alloy without TiC. Excessive TiC decreased the tensile properties to an obvious degree. The addition of TiC improved the wear resistance of the cladded alloy significantly. When normal loads were 5 N and 10 N, the cladded alloy with 5% TiC exhibited high wear resistance, and the wear rates decreased by 59% and 78% compared with those of the cladded alloy without TiC. However, when normal load was 20 N, the cladded alloy with 1% TiC possessed superior wear resistance, and its wear rate decreased by 81% compared with that of the cladded alloy without TiC. The main wear mechanism of the cladded alloys was abrasion wear when normal load was low, but serious plastic deformation played a role in the wear process when normal load was high.

Monitoring tooth wear

Tooth wear is a multifactorial condition leading to the irreversible loss of dental hard tissues. Although tooth wear is mainly a physiological process, it can become pathological if the wear process is accelerated for various reasons. Since this process is not linear, but can sometimes be inactive and sometimes active, a careful monitoring policy is necessary. The possible monitoring tools are described in this article, and a proposal is made with regard to the frequency of the systematic and periodic collection of information. CPD/Clinical Relevance: The prevalence of tooth wear is increasing and it now carries the third highest risk (after caries and periodontitis) for maintaining the natural dentition.

Improved Wear Profile Modeling of Planetary Roller Screw Mechanism With Thread Optimization

Abstract A systematic process of matrices-based wear profile modeling and a new optimization approach for planetary roller screw mechanism (PRSM) was proposed in this paper to improve the anti-wear performance with varied thread geometries. The wear evolution characteristics of thread surfaces for convex–concave contact and convex–straight contact were captured by incorporating updated axial clearances originated from accumulated thread wear, which provides a new perspective to predict the wear process of PRSM. The results show that the wear depth in convex–concave contact is 22% shallower than convex–straight contact with 105 numbers of cycles, which suggests thread wear can be limited with plausible geometrical parameters. Further analysis showed that as the surface roughness increases, the true equivalent pressure, the plastic strain, and the maximum wear depth become larger. In addition, the effect of the surface textures on the tribological properties of threads is also discussed to improve the applicability of the proposed methodology.

Identification method for unsteady friction of tool flank for high efficiency milling cutter

Under the cutting loads of high efficiency and intermittent, the friction status between the tool flank and transition surface has time-varying characteristics, which directly affects friction and wear performance of the milling cutter. The dynamic distribution of instantaneous friction on tool flank under milling vibration needs to be revealed. In this work, the effect of milling vibration on instantaneous cutting contact relationship between milling cutter and workpiece was researched, a calculation method for the instantaneous friction velocity and friction energy consumption on tool flank was proposed. The variation of instantaneous friction between tool flank and transition surface under milling vibration was identified and evaluated by power spectral entropy and cross-correlation function. A method for identifying the unsteady friction of tool flank was proposed. The response analysis and experimental verification were conducted. The results showed that the frequency domain parameter distribution of friction energy consumption on tool flank had a strong correlation with the wear depth distribution, and was obviously sensitive to the milling parameters. The above models and methods could be used to reveal the influence of key milling process variables on unsteady friction and wear process of milling cutter’s multiple tool flank.

Steady state analysis on sliding wear behavior of waste marble dust filled kenaf‐polyester composites

AbstractIn view of the rising demand of natural fiber reinforced polymers in engineering applications, the current research is taken on to study the effects of particulate filling in polyester‐kenaf fiber composite in terms of its sliding wear performance. A set of polyester‐based hybrid composites are fabricated with fixed kenaf fiber content and varied quantities of waste marble dust (0 wt. %, 16 wt. % and 32 wt. %). These composites are subjected to dry‐sliding wear trials as per ASTM G‐99 05 under different test conditions and the specific wear rate are estimated. The test results are analyzed to obtain the parametric appraisal of the wear process using response surface method. The analysis reveals that the filler content followed by sliding velocity, normal load and sliding distance has the detrimental impact on the specific wear rate of such hybrid composites. A morphological study is performed using a scanning electron microscope to identify prominent wear mechanisms and it is found that the wear loss is primarily due to the formation of wear tracks, cracks, craters, plastic deformation, wear debris and the removal of matrix layer etc. during the sliding process.

Numerical simulation of linear reciprocating wear mechanism of hybrid aluminum metal matrix composite using finite element method

This work aims to analyze the wear properties of the hybrid aluminum metal matrix composites (HAMMCs) using finite element analysis (FEA). A dry sliding linear reciprocating wear mechanism is analyzed using ANSYS 19.1. Aluminum 7075 alloy and HAMMC reinforced with ZrB2 (1, 3, and 5 wt.%) and fly ash (2 wt.%) is taken as sample material. A steel ball (EN 52100) is utilized as a counterpart in the dry sliding wear properties study. The deformation of the steel ball during the wear process is assumed to be negligible. Under various circumstances, a 3D point-to-surface connection is built to analyze the dry sliding wear process. The wear depth, contact pressure, and wear volume are analyzed using FEA. The analytical results are compared with the experimental results with the help of ANSYS to analyze the process parameters. The ANOVA analysis is employed for optimization, which exhibits that the load had the most significant impact on the material’s wear rate, followed by the material’s composition and temperature. The wear depth, wear rate, and contact pressure at optimum input parameters for the HAMMCs are 0.47 μm, 11.31 × 10−6 mm3 Nm−1, and 0.33 MPa, respectively. The Simulated results support the experimental results, and the average error is 9.82%.

Study on the Coupling Relationship between Wear and Dynamics in Planetary Gear Systems

The occurrence of wear is hard to avoid in gear systems because of their transmission principle. Wear will lead to a deviation of the system’s performance from the design objectives or even failure. In this paper, a dynamic wear prediction model considering the friction and wear of all meshing gears is proposed for planetary gear systems. The differences between different wear prediction methods are compared. The interactions among the wear, the dynamic response, and the uniform load performance of the planetary gears are investigated. The results show that considering friction and wear on all tooth surfaces can significantly reduce errors in the simulation. Wear mainly affects meshing stiffness in the double tooth contact region. The degree of fluctuation of stiffness and meshing force increases significantly with wear. The load-sharing factor in the dedendum and addendum regions decreases. Accordingly, the position of maximum wear on the tooth surface moves slowly towards the pitch line. Early wear improves the dynamic performance of the system. As the wear deteriorates, the higher harmonics of the meshing frequency increase significantly. The uniform load performance of planet gears exhibits the same trend of dynamic response as the others during the wear process.

Single asperity nanoscale wear of carbides and matrix of wrought high carbon CoCrMo alloy

High carbon CoCrMo alloy has been widely used in orthopedic implants. Carbides improve the strength of the material and influence wear resistance. An atomic force microscopy (AFM)-based single asperity tribology method was developed to investigate the wear performance of individual carbides and base metal matrix of high carbon CoCrMo alloy. Sub-nano to nanoscale wear on single carbides was performed and quantified. Nanowear behavior of two types (Cr-rich and Mo-Rich) of carbides was stress-dependent (from 7.8 GPa to 9.8 GPa) and influenced by chemical composition. The lower wear depth of both Cr-rich and Mo-rich carbide compared to the matrix alloy shows higher wear resistance compared to metal matrix. Cr-rich carbides exhibit significantly smaller wear depth (p < 0.05) compared to Mo-rich carbides after nanowear at the same contact stress (9.8 GPa). The entire region of Cr-rich carbide shows high wear resistance without fracture after nanowear at 14.7 GPa. The AFM-based nanowear methods used are able to detect sub-nanometer wear depths on worn regions as small as 0.2 μm and provide abilities to study local nanometer wear processes in complex alloy systems.

Tribological Behavior of SiC and Al2O3 Reinforced Aluminium Metal Matrix Composite

Stir casting offers greater benefits than other techniques for creating metal matrix composites. Using the high-energy stir casting process, the aluminium alloy Al5052 was strengthened with SiC and Al2O3 particles in varied weight percentages (0, 2, 4, and 6 wt.%). Through the use of XRD and SEM, the structural characterization was carried out. Investigations were made into mechanical characteristics such as hardness, tensile strength, and wear. To conduct wear studies, the load was changed while all other factors remained constant. SEM analysis was used to study the wear process. This study found that SiC and Al2O3 added to aluminium composites made them more resistant to wear. The findings demonstrated that when compared to base materials, the percentage of SiC and Al2O3 contained in the samples enhanced the mechanical characteristics, wear resistance, and hardness.

Microstructure Image-Based Finite Element Methodology to Design Abradable Coatings for Aero Engines

Upgrading abradable or wearable coatings in the high-temperature zone of aero engines is advised to increase the efficiency and high-density power in gas turbine engines for military or commercial fixed-wing and rotary-wing aircraft. The development of these coated materials is also motivated by minimization of the number of failures in the blade, as well as increasing their resistance to wear and erosion. It is suggested that abradable coatings or seals be used to accomplish this goal. The space between the rotor and the shroud is minimized thanks to an abradable seal at the blade’s tip. Coatings that can withstand abrasion are often multiphase materials sprayed through thermal spray methods, and which consist of a metal matAzmeerix, oxide particles, and void space. The maintenance of an ideal blend of qualities, such as erosion resistance and hardness, during production determines a seal’s effectiveness. The objective of this research is to develop microstructure-based modelling methodology which will mimic the coating wear process and subsequently help in designing the abradable coating composition. Microstructure modelling, meshing, and wear analysis using many tools such as Fusion360, Hyper Mesh, and LS-Dyna, have been employed to develop an abradable coating model and perform wear analysis using a simulated rub rig test. The relation between percentage composition and morphology variations of metal, oxide, and voids to the output parameters such as hardness, abradability, and other mechanical properties is explored using simulated finite analysis models of real micrographic images of abradable coatings.

Mechanical and tribological characteristics of hypo eutectic Al-7Si alloy-based composite reinforced with Sn metal powder and Al2O3 using bottom pouring stir casting technique

The present work highlights the significant effects of varying wt% of Sn metal powder in the hypo eutectic Al-7Si/10 wt% Al2O3 composite. The composites were manufactured through a multi-stage stir casting route and characterized for mechanical and wear behavior using ASTM standards. The results revealed that the increase in Sn content up to 4 wt% in the matrix enhanced the microhardness, tensile properties, and reduced the porosity. The Al-7Si/10 wt% Al2O3 composite with 4% Sn particle reinforcement shows the highest tensile strength and hardness of 132 MPa and 90 BHN, respectively. All composites exhibited a ductile mode of failure, as evidenced by the tear ridges and dimples on the tensile fracture surface. By adding of Sn metal powder to the material system, the wear rate and coefficient of friction were reduced. At 1000 m of sliding distance and 1 ms−1 of sliding velocity, the wear loss of 8 wt% Sn composite was decreased by 88.8% as compared to Al-7Si base alloy at a normal load of 10 N whereas, at 40 N of normal load, the wear loss was decreased by 66.6%. During the wear process, the Sn metal powder surfaced and formed a thin tribo film that mechanically mixed with the surface, resulting in reduced friction. The layer at the interface prevented direct contact between asperities on the mating surface, which reduced wear loss. The composites without Sn metal powder exhibited adhesive wear and delamination as the primary wear mechanisms, while composites with Sn showed predominantly adhesive wear. Regression analysis followed by a desirability function approach was carried out to develop the model and optimize the operating conditions of the experiments.

Annealing Effect on Mechanical and Tribological Behaviors of Nanoscale Mechanics of Zr60Cu25Al5Ag5Ni5 Thin-Layer Metallic Glasses for Engineering Materials Applications.

A new and unique alloy formulation design strategy has been developed in order to fabricate thin-layered metallic glasses (TLMGs) with superior fracture resistance and low coefficient of friction (COF) during the nanoscratching test. Due to the outstanding properties, TFMG could be applied for different uses, such as for surface coating, biomedical, bioimprinting, electronic devices, spacecraft, and railway, all of which need surface fracture resistance. The fabricated Zr-based metallic glass was prepared from Zr, Al, Cu, Ni, and Ag above 99.9 Wt % in purity by arch melting techniques. TFMGs were coated on silicon wafer by sputtering the vapor deposition method from bulk metallic glass then annealed below glass transition temperature Tg ∼ 450 °C for 10, 30, and 60 min. Nanoindentation and nanoscratch tests were used to investigate nanomechanical and nanotribological properties, and atomic force microscopy (AFM) was used to examine the surface morphology and microstructures of TLMG. The nanoindentation data indicated that the average hardness of metallic glasses increased from 9.75 (as-cast MG) to 13.4 GPa (annealed for 60 min). Coefficients of friction for the cast sample, annealed for unannealed, 10, 30, and 60 min, were 0.062, 0.049, 0.039, and 0.03, respectively, as well as the wear depths were 201.56, 148.43, 37.32, and 25.27 nm, respectively. These studies show that the coefficient of friction and wear rate decreases when the annealing time increases as a result of atomic reordering and structural relaxation that occurred at longer annealing times. Furthermore, continuous wear process, wear depth, wear track volume, and contact area decrease with increasing annealing time. This study can be used to design protocols to prepare novel TLMGs, which have outstanding mechanical and tribological properties for engineering materials applications.

Wear behavior of different coated tools in MQL-assisted milling of magnesium-based rare-earth alloys

One of the most important and often employed indicators for describing machinability and machining quality is tool wear. While flank wear is commonly used to gauge the extent of a worn scar, tool wear is characterized more by its shape than its size. To quantify the wear shape, more specific data concerning the wear contour is required. With this aim, the present work addresses the fundamental wear mechanisms and failure modes of several coated tools used in the mechanical milling of rare-earth magnesium (Mg-RE) alloys. Uncoated, edge-strengthened, TiAlN-coated, and diamond-coated tools were tested under dry and minimal quantity lubrication (MQL) conditions. The cutting energy flow and consumption rules governing the tool wear processes were quantified using the exergy analysis theory. The results indicate that the cutting performances of tools and the surface quality are both enhanced by the MQL through reducing adhesion wear. For the unstrengthened tool, a tool wear reduction of 55% is achieved by the MQL. While for the TiAlN-coated tool, the tool wear can be furtherly suppressed by 49%.

ФЕНОМЕН «СВОЕЙ ВЕЩИ»: ПРАКТИКИ ФОРМИРОВАНИЯ ПРИВЯЗАННОСТИ К ОДЕЖДЕ

The article explores the experience of interacting with newly purchased clothes to describe the practices by which relationships are formed with our everyday clothes, the ones that we later consider part of our wardrobe. The process of constituting a phenomenon of “our own” clothing is based on the phenomenology of perception, the affect theory, and the responses of fifteen focus group participants who recalled stories about newly acquired garments. The formation of attachment relationships can be divided into two stages: pre-wearing interaction, which may include choosing the right place in the wardrobe, washing, fitting or even alteration, trying on and searching for combinations with other clothes in the wardrobe; and the wearing process itself, in which the formation of relationships with clothing is influenced both by its material qualities – length, width, density and details, and our impression of the process, mediated not only by bodily sensations, but by the image of the body and comments about it.

Aero-engine as the object of tribological research

During the operation of aero-engines (turbine and piston engines), wear processes occur in tribological nodes, which significantly affect the reliability and safety of flight operations. This paper presents aspects of tribological diagnostics of aircraft engines based on periodic testing of lubricant samples in laboratories. Firstly, the object of research with its design features, operating parameters and used lubricants is presented, as well as the theoretical basis of tribological testing. This was followed by a description of the testing methods used in tribological diagnostics of aero-engines, taking into account lubricant degradation and contamination processes, standards, testing methodologies and operating experience described in the literature, including the machine failure curve. Next, the capabilities of the testing methods are illustrated with results from periodic tribological testing of turbine engines, obtained at an accredited tribological systems diagnostics laboratory. In the following section, the role of trend analysis and statistical criteria in the process of diagnosing and managing the risk of operation of aero-engines, exploited according to both their technical condition and planned maintenance, was indicated. Then, the possibility of improving the reliability of tribological diagnostics of aero-engines on the basis of experience from industry - real-time monitoring of selected tribological parameters - was signalled. In conclusion, the high efficiency and role of tribological diagnostics in maintaining the operational safety of a fleet of different aircraft types is indicated.

Influence of scanning speed on the microstructure, nanoindentation characteristics and tribological behavior of novel maraging steel coatings by laser cladding

This paper utilized a novel high-Mo maraging steel powder to prepare maraging steel coatings through laser cladding. The study investigated how scanning speed affects the microstructure, phase formation, nanoindentation properties, and wear properties of the resulting laser-clad maraging steel coatings. The experimental results reveal that the maraging steel coating consists of martensite and austenite phases. Moreover, diffraction peaks of Fe2Mo phase were observed at low scanning speeds. As the scanning speed increases, there is a gradual reduction in the austenite content, accompanied by a decrease in the Fe2Mo phase content. Moreover, both martensite and austenite exhibit an increase in lattice distortion. EBSD analysis demonstrates a reduce in grain size as the scanning speed increases, accompanied by the emergence of LAGBs and an increase in dislocation density, as indicated by the rising KAM value. TEM analysis confirms the presence of a Mo-rich precipitated phase, characterized by a dense hexagonal structure consisting of the Fe2Mo intermetallic compound. The Fe2Mo phase displays high hardness, thereby significantly enhancing the second precipitation strengthening effect of the coating. The nanoindentation characteristics of the S2 coating are exceptional, displaying remarkable values for nanohardness, HU, H/E ratio, and H3/E2 ratio. Specifically, the S2 coating exhibits a nanohardness of 4.843 ± 0.104 GPa, accompanied by an HU value of 0.2073 GPa. Additionally, the H/E ratio and H3/E2 ratio are reported as 0.0214 and 0.002218, respectively. Demonstrates excellent mechanical properties of S2 coating. Furthermore, the S2 coating demonstrates outstanding performance in terms of wear resistance and deformation resistance, exhibiting the lowest friction coefficient and specific wear rate, measuring at 0.438 and 1.381 × 10−5 mm3/N•m, respectively. The observed wear mechanisms in the S2 coating include adhesive wear, abrasive wear and oxidative wear. Notably, lower scanning speeds promote the precipitation of Fe2Mo particles, which play a supportive role in the wear process by weakening the tendency of oxidative wear. Overall, the remarkable properties exhibited by the S2 coating, such as nanohardness, wear resistance, and deformation resistance, position it as a promising candidate for various technological applications.

Nanoscale Wear Triggered by Stress-Driven Electron Transfer.

Wear of sliding contacts causes device failure and energy costs; however, the microscopic principle in activating wear of the interfaces under stress is still open. Here, the typical nanoscale wear, in the case of silicon against silicon dioxide, is investigated by single-asperity wear experiments and density functional theory calculations. The tests demonstrate that the wear rate of silicon in ambient air increases exponentially with stress and does not obey classical Archard's law. Series calculations of atomistic wear reactions generally reveal that the mechanical stress linearly drives the electron transfer to activate the sequential formation and rupture of interfacial bonds in the atomistic wear process. The atomistic wear model is thus resolved by combining the present stress-driven electron transfer model with Maxwell-Boltzmann statistics. This work may advance electronic insights into the law of nanoscale wear for understanding and controlling wear and manufacturing of material surfaces.

Effect of spherical crown texturing and ionized sulfur infiltration on the tribological performance of piston-cylinder liner

In this study, the piston-cylinder liner was treated with single glow photoionization sulfurization of a cast aluminum alloy (AlSi10Mg), and the effect of the spherical crown texture on frictional properties of the piston-cylinder liner were investigated before and after the sulfurization treatment. The treated specimens were characterized and evaluated via microscopic morphological analysis, three-dimensional morphological analysis, X-ray diffraction (XRD), thin film diffraction, microhardness testing, and friction wear experiments. Fluent fluid analysis software was used to develop a flow field simulation model for the spherical crown texture. Results of the study showed that the average friction coefficients of the specimens treated with sulfur infiltration were all lower than those of untreated specimens, and the low friction coefficients were closely related to the laminar structure and weak interfacial bonding of the sulfur infiltration layer. The spherical crown structure effectively affected the stree distribution on surface of the specimens uniformly, which improved the bearing capacity and durability of the specimens, and the surface texture helped reduce the contact area and store the debris generated during the wear process, thus improving the friction performance. Mechanical stamping caused material aggregation on the edges of the weave, which increased the hardness of the edges and thus reduces the increase in wear around the weave. The surface microstructure of the specimens was effectively improved after sulfurization treatment, leading to higher wear resistance for the sulfurized specimens. Given the relative lack of research on the composite ionic sulfurization of piston-cylinder liner spherical crown texture at home and abroad, this experiment provides data support for this direction. The results provide beneficial clues for the design and optimization of the piston-cylinder liner spherical crown structure.