Characteristics Of Surface Layer Research Articles

Structure and mechanical properties of a composite based on titanium and a bioactive coating with a two-level surface relief

Abstract To develop bone implants using Ti materials, the issue of creating bioactive coatings that ensure their rapid engraftment to the bone is acute. The rate of fusion of Ti implants with bone tissue is significantly influenced by the degree of modification of the coating surface based on changes in the relief, chemical composition of the surface layer and mechanical characteristics of the implant. The structure and mechanical properties of a Ti-based composite with TiO2/Ag/HAp coating of an island-like type were investigated, which showed high bioactive properties of the sample. The paper shows that the application of an island-like coating on the Ti surface with a height difference of 0.7 microns does not lead to a deterioration in the mechanical characteristics of the Ti implant, and the hardness increases by 15%.

Vibration behavior prediction of submerged nanobeams with axially traveling supports: numerical, analytical, and machine learning approaches

This work surveyed the vibration behavior and stability analysis of an underwater moving flexible nanosize beam, implementing numerical and analytical methods as well as tree-based machine learning (ML) algorithms. Dynamic modeling is performed based on the nonlocal stress-strain gradient theory (NSSGT), incorporating variable environmental conditions, surface energy, and rotational inertia effects. The natural frequencies and instability threshold are computed numerically. The exact closed-form mathematical expression for the critical towing velocity of the nanosize beam is determined analytically. Also, decision tree regression and least-squares boosting tree (LSBT) regression algorithms are exploited to predict stability boundaries and the fundamental vibration frequency, and their efficiency is surveyed accordingly. Comparative studies and parametric investigations are conducted. The impressions of geometry, added mass coefficient, scale ratio parameter, surface layer characteristics, fluid mass ratio, humidity, temperature rise, and external magnetic field intensity on the nanosystem dynamics are examined and illuminated. It is detected that the results of the analytical method and ML-based approaches are consistent with those reported by the numerical technique and literature. The results asserted that the proposed ML algorithms have acceptable performance and excellent effectiveness in computational time and cost. It is comprehended that the dynamic features of submerged traveling nanobeams drastically depend on the rotational inertia effects and thickness-dependent scale effects. The stability of the immersed movable nanoscale beams is perceived to improve by increasing the scale ratio parameter and the added mass coefficient. From the perspective of the optimal design of engineering instrumentation tools, the outcomes of the current article can be applied as an inclusive benchmark.

Study of Surface Layer Characteristics in the Presence of Suspended Snow Particles Using Observational Data and Large Eddy Simulation

Study of Surface Layer Characteristics in the Presence of Suspended Snow Particles Using Observational Data and Large Eddy Simulation

The Role of Air in Laser-Induced Thermal Emission of Surface Layers of Porous Carbon Materials

The influence of the surrounding air on the amplitude and shape of thermal radiation pulses (at a wavelength of 430 nm) during the heating of the surface layer of a porous carbon material (to temperatures of the order of 2000–3000 K) by the radiation of a Q-switched neodymium laser is studied. When the pressure of the surrounding air is reduced to forevacuum conditions, the experiments showed a one-and-a-half-fold increase in the amplitude of pulsed signals of thermal radiation and an increase in the decay time of the glow by about a third. Numerical calculations of the dynamics of the temperature field in the surface layer of the material during the irradiation by nanosecond laser pulses are carried out. An improved model is used in the calculations, which accounts for (i) the porosity of the material and (ii) the temperature dependence of the coefficients of thermal conductivity and the heat capacities of carbon and air. To calculate the thermal conductivity of the porous material, a model of a cubic array of intersecting square rods is used. The satisfactory consistency of calculation results with experimental data is obtained. The above-mentioned improvements of the calculation model made it possible to reconcile the estimates of the thermal characteristics of surface layers of carbon, obtained from the emission decay data, with the reference data published in the literature.

Исследование усталостной долговечности пружин боковых скользунов тележки модели 18-9891

Purpose: To conduct comprehensive experimental studies on the fatigue strength of side bearing springs for freight bogies, evaluating the effectiveness of thermal and shot peening treatments during their manufacturing process. Methods: The method of stand endurance (fatigue) testing of constant contact side bearing springs has been applied, allowing for obtaining endurance characteristics of actual components. Metallographic studies of spring steel have been conducted to investigate the influence of strengthening operations during spring manufacturing on their fatigue strength, with the assessment of mechanical characteristics of surface layers in various zones of the helical spatial beam. Results: Experimental force characteristics of spring sets for side bearings of an innovative freight bogie with a load of 25 tons (245 kN) on the axle have been obtained. Fatigue curves of the springs have been presented in a probabilistic aspect, enabling the determination of load factor for fatigue strength of the springs considering operational loading, as well as justifying the compliance of the spring sets with the regulatory requirements. Practical significance: Based on the research results, the considered constructive-technological variant of the constant contact side bearing spring for the freight bogie has been put into serial production. The test results allow us to reasonably determine the warranty mileage of the responsible assembly of the bogie and to conduct further work on the design modernization with the aim of increasing operational life.

Distinctive performance evolution of surface layer in TC4 alloy oxidized at high temperature: Softening or hardening?

The characteristics of metal surface layer at high-temperature significantly affect the service performance of TC4 titanium alloy components, so that the evolution mechanism of mechanical properties of metal surface layer under high-temperature oxidation conditions is an important scientific issue. In the present work, the mechanical behavior and the relevant mechanism of metal surface oxidized at the temperatures of 500 ℃, 700 ℃, and 900 ℃ for different times have been systematically investigated. The experimental results show that with the increase of temperature, the oxidation kinetics curve of the alloy changes from parabolic law to linear law, and the oxidation reaction changes from diffusion control to interfacial reaction control. Furthermore, as the temperature increases from 500 °C to 900 °C, the feature of oxide scale changes from the single-layer structure to the multi-layer alternating structure, and the thickness of oxide scales and depth of alpha case increased with increasing temperature. The surface oxide scale is mainly composed of low valent oxides such as Ti3O and Ti6O during low-temperature oxidation as well as short-term high temperature oxidation. After long-term high temperature oxidation, the oxide scale is mainly composed of high valent oxides such as TiO2, Al2O3, and TiVO4. Simultaneously, significant changes occur in the composition, microstructure and properties of metal surface layer. In general, the microstructure and mechanical properties of the surface-layer metal are strongly dependent upon the competitive influence of the outward diffusion of Al and the inward diffusion of O. In the temperature range of 500–900ºC, when the temperature is relatively low, the softening effect caused by the outward diffusion of Al is stronger than the strengthening effect caused by the inward diffusion of O, and a surface softening effect thus occurs. On the contrary, when the temperature is high, the strengthening effect caused by the inward diffusion of O is stronger than the softening effect caused by the outward diffusion of Al, and a surface strengthening effect accordingly happens.

On the value of the von Kármán constant in the atmospheric surface layers over urban surfaces

Large-eddy simulations of turbulent boundary flow over different urban-like surfaces in neutrally stratified conditions are performed to study the atmospheric surface layer characteristics over urban areas. A simple method based on the vertical profile of the dimensionless velocity gradient is used to identify the inertial sublayer (ISL) in all cases. The results show that the mean wind profiles in the different urban ISLs can all be generally described by the logarithmic wind profile. However, for the idealized urban surfaces composed of regular building block arrays and the realistic urban surface case, the von Kármán constant (κ) in the ISL is found to be significantly smaller (in the range of 0.21–0.27) than the typically adopted value of 0.4. As κ is a key constant in the parametrizations of urban surface flows and is usually assumed to be ≈0.4 in existing surface parametrization models, a significantly smaller κ implies that large uncertainties may exist in the predictions of the momentum, heat, and scalar turbulent fluxes over urban surfaces using these models.

A comparison study of using polyethylene terephthalate and limestone fillers on porous asphalt mixture behaviours

Regardless of their gradations, all varieties of asphalts pavement mixtures are smooth and impermeable, which reduces the safety of cars in different weather situations. Comfort and safety on the roads during various weather conditions are directly influenced by surface layer characteristics. Porous asphalt has quick surface drainage, eliminates splashing, and improves safety. Additionally, because water drains into the asphalt mixture's pores, the desired level of friction between the tire and the pavement will be guaranteed. This necessitates the production of permeable asphalt pavement mixtures for roads and highways that can handle heavy traffic loads. The primary objective of this study is to investigate the enhancement of stability and mechanical properties in porous mixtures by substituting conventional limestone filler with Polyethylene Terephthalate Waste Plastic (PET) powder. Simultaneously, the study aims to mitigate environmental pollution by utilizing PET materials, which take decades to decompose naturally. The PET used in the study was melted at 260 0C and then powdered using 7000, 18000, and 28000 rpm grinders to obtain filler that passed sieve no. 200. The ASTM D7064-based evaluation of the mixture's optimum asphalt content takes into account essential factors, including drain down, percentage of air voids, and optionally, the results of the Cantabro abrasion test, which was calculated to be 4.75%, decreased to 4.5% when polyethylene terephthalate powder was utilized as filler in place of limestone. The optimum limestone filler percentage was 3.0% based on National Asphalt Pavement Association (NAPA) gradation employed the same procedure in the optimum asphalt content evaluation. However, the results showed that the optimum amount when using PET powder reached 3.5%.The criteria used to investigate the newly proposed asphalt pavement mixture are the Marshall method, Drain down of binder, Cantabro loss test, and permeability of porous mixture. This research reveals that adding PET as an alternative filler to limestone reduces permeability, Drain Down, and Cantabro by 22.64%, 29.27%, and 16.33% respectively while increasing the stability by more than 15.5%. It is still promising that the permeability of the mixture stays within the desirable limit for comfort and safe driving. Filler replacement was tied to performance testing and was demonstrated to raise the deformation strength in the KIM test more than twice from 1.54 MPa to 3.63 MPa by employing a specialized head and Marshall loading machine as an alternative method to the wheel tracking test for evaluating rutting in the mixture. The index of retained stability by aging the samples in water bath at 25 °C from one to four days increased from 8.66 MPa by 33.1% to reach 12.57 MPa where filler replaced, and the indirect tensile strength based on ASTM D4867raised by 29.08% from 0.578 to 0.735 MPa for conditions samples and raised from 0.681 to 0.879 MPa to raise the unconditioned samples by 12.9%. It is also worth noting that the use of PET as a waste material has significant environmental benefits.

Construction of a Real-Time Forecast Model for Coastal Engineering and Processes Nested in a Basin Scale Model

A numerical model was developed using Delft3D to simulate the circulation dynamics in Port Everglades, FL, and the adjacent coastal area. The model was nested within the HYCOM (Hybrid Coordinate Ocean Model), while meteorological data were obtained from the NARR (North American Regional Reanalysis) model. To evaluate the model, model outputs were compared with observed data from the NOAA. Calibration experiments were conducted on the model parameters, including the bottom friction, wind forcings, and vertical layer specification. These experiments revealed that implementing a 10-layer model slightly improved the vertical stratification, while the utilization of 2-D wind data resulted in more pronounced surface layer characteristics in temperature and velocity profiles and employing moderate values of the Chezy coefficient produced optimal outcomes for the bottom roughness parameter. The model demonstrated satisfactory performance across major parameters, including water level, salinity, temperature, and currents. A real-time forecast system has been constructed with this nested model, providing up to 3-day forecasts that are updated daily. To facilitate automated forecasting without manual intervention, an automation system has been developed using a combination of bash, MATLAB, and Python scripts. This study provides a comprehensive documentation of the concepts and detailed methods involved in developing a real-time forecast model for estuarine and coastal regions.

Effect of abrasive water pressure on the surface layer characteristics of duplex stainless steel 2205

The martensitic stainless steel shot with a high number of cycles was applied to the abrasive water jet (AWJ) to study the effect of jet pressures on the surface layer characteristics of 2205 duplex stainless steel. The Almen strips (type A) quantitatively evaluate the AWJ intensity at jet pressures of 50 MPa, 60 MPa, and 70 MPa. The surface layer characteristics were comprehensively studied using scanning electron microscopy, laser scanning confocal microscopy, x-ray diffraction, electron backscatter diffraction techniques, and microhardness tester. It was found that with the increase of the jet pressure from 50 MPa to 60 MPa and 70 MPa, the AWJ intensity increased by 5.0% and 22% and the surface roughness for Ra increased by 16% and 37%. Residual compressive stresses existed in both phases to a depth of more than 200 μm. The austenite hardening rate is higher than that of ferrite, and the maximum residual compressive stress in austenite of the surface layer of the AWJ specimen occurred at the subsurface. The maximum residual compressive stress in ferrite occurred at the surface (50 MPa, 60 MPa) and subsurface (70 MPa). The hetero-deformation induced stresses formed during the plastic deformation of the heterostructured material made the austenitic residual compressive stresses in the surface layer slightly higher than those in ferrite. The surface grain refinement depth exceeded 150 μm, and the degree of austenite grain refinement was higher than that of ferrite. The fraction of deformation-induced martensite and the depth of phase transformation increased with the increase of jet pressure. These changes caused the surface hardening of the specimen, and the jet pressure had a significant effect on the depth of the hardened layer and the microhardness at depth greater than 50 μm.

Influence of bedrock on viscoelastic responses and parametric back-calculation results for asphalt pavements and prediction of bedrock depth under FWD tests

Structural evaluation with a falling weight deflectometer (FWD) plays an essential role in the maintenance and rehabilitation of highways. Research on the influence of bedrock on the results of FWD tests and dynamic back-calculations for asphalt pavements has been a hot topic. In this study, the viscoelastic characteristics of the asphalt surface layer were described by the modified Havriliak-Negami (MHN) model rather than the layered elastic theory computing framework. The effects of bedrock on the deflection time history curves of viscoelastic asphalt pavement under the FWD test were investigated and analyzed by the spectral element method with fixed-end boundary conditions (B-SEM). The effects of bedrock on parametric back-calculation results for the viscoelastic asphalt surface layer and other elastic layers were explored by dynamic back-calculations. To exclude the impact of bedrock and improve the back-calculation accuracy, support vector regression optimized by the gravitational search algorithm (GSA-SVR) was adopted to predict bedrock depth. The viscoelastic responses and dynamic parametric back-calculation results were significantly influenced by bedrock beneath asphalt pavements, and the influence decreased (but was not eliminated) with increasing depth of bedrock. The GSA-SVR model provided excellent predictions of bedrock depth, and it can be applied for pavement performance assessment in road projects.

Study of micrometeorological characteristics of the atmospheric surface layer over a tropical coastal station in Goa

Study of micrometeorological characteristics of the atmospheric surface layer over a tropical coastal station in Goa

Analysis of surface layer characteristics after machining of a Ni-based superalloy

Analysis of surface layer characteristics after machining of a Ni-based superalloy

Identification of surface dyeing agents of two bookbinding leathers from 19th‐century Qajar, Iran, using LC–MS, μXRF and FTIR spectroscopy

AbstractIdentifying tanning and dyeing agents of historical leathers is one of the less studied subjects. Therefore, this study aims to distinguish the surface dyeing agent of historical leathers along with the tanning agents. It helps to better understand the leather‐making process of past centuries. For this purpose, two Iranian historical bookbinding leathers belonging to the Qajar era were investigated. The tannins were examined by ferric spot test and ATR‐FTIR spectroscopy after being extracted from the leather corium layer. ATR‐FTIR and μXRF spectroscopy were also used to study the characteristics of the leathers' surface, in both grain and corium layers. LC–MS was also used to analyze the extracts taken from the surface of the leather samples. The results showed the corium layer of leathers has a significant number of hydrolysable tannins, especially gallotannins, as tanning agents. The characteristics of their FTIR spectra are significantly similar to those of sumac. LC–MS results showed the presence of ellagic acid, as an indicator analyte, on the surface of the leathers. It indicates that tannin‐rich plants, such as oak, have been used for dyeing these leathers. Investigation of the structural properties of the grain and corium layers also revealed the accumulation of copper and iron on the surface of the leathers. Accordingly, copper and iron, which reacted with tannins to give a black color, were the main dyeing factor used in both historical leather samples.

Analysis of Mechanical Characteristics of Surface Layers of Nickel with a Sputtered Aluminum Film after Ion-Beam Mixing

Analysis of Mechanical Characteristics of Surface Layers of Nickel with a Sputtered Aluminum Film after Ion-Beam Mixing

The study of slag particle deposition process based on Monte Carlo simulation

The microscopic characteristics of particle deposition are critically important for the study of slag flow, particularly for semi-viscous particles. In this study, based on the disordered motion of particle deposition, a Monte Carlo (MC) simulation method was adopted to study the deposition, attachment and rebound process of particles. Considering the characteristics of the partial melting of semi-viscous particles, the collapse behavior and deposition probability of the deposition sequence were studied. The concepts of a rough surface layer and steady bottom layer were proposed. The results showed that the roughness of the deposition sequence increased with an increase in collapse height. Meanwhile, more particles were captured in the steady bottom layer; therefore, the time required for the steady bottom layer to stabilize increased. Considering the physical significance of the collapse height, the effect of the temperature on the deposition characteristics of the rough surface layer was studied.

Research on Surface Integrity of Mesoscopic Geometry Tool Milling Titanium Alloy

For the problem of poor surface quality of titanium alloy processing, the micro textures are placed on the flank face of the blunt circular cutting edge ball-end milling cutter, designed the experiments and study the influence rules of various mesoscopic geometric parameters on the surface integrity of titanium alloy milling. The results show that appropriate mesoscopic geometric parameters can significantly improve the surface integrity of titanium alloy workpieces. The parameters were optimized with the aid of particle swarm algorithm and according to the two directions of characterization morphology and the surface layer characteristics.

Study of qualitative characteristics of surface layer of steels after electromechanical treatment with dynamic deformation

The results of studies of the qualitative characteristics of the hardened surface layer of normalized medium-carbon steels after electromechanical treatment with the dynamic application of the deformation force (electromechanical coinage EMC) are presented. The influence of the dynamic electromechanical treatment current density on the structure, microhardness, and thickness of the hardened surface layer has been established. An increase in current density during EMС leads to a significant increase in the depth of hardening, and an increase in the maximum hardness of steels 40Kh, 45, 50Kh. The results obtained can be used to establish the connection between the qualitative characteristics of the surface layer and the electromechanical coinage modes for a targeted effect on the structure of the treated surface.

DESTRUCTION MECHANISMS OF CU-ETP COPPER GUIDES FOR SECTIONAL INSULATORS OF RAILWAY TRACTION

This article presents the results of a research on the operational damage to sectional insulator guides made of hard electrolytic copper Cu-ETP (Electrolytic Tough Pitch Copper). The guides were used on various rail routes, in real conditions, on which the trains ran at maximum speeds between 40 and 120 km/h for periods of 6 or 12 months. The microstructure of the surface, the working layer of the guide, which contacts the graphite plate of the current collector and the cross-section of the guide in the place where it was damaged was examined using the Olympus light microscope. The analysis of the chemical composition in the EDS micro-regions was performed using the Zeiss Supra 53 scanning electron microscope (SEM), while the qualitative X-ray phase analysis was performed with the use of the Panalytical X'Pert diffractometer. Scratches and deformations of the surface layer characteristic of the phenomenon of friction caused by the current collector were observed in the microstructure of the damaged parts of the guides of section insulators. The effect of a very intense oxidation process was also observed, as well as the effects of an electric arc, which according to the author, is the factor that has the most destructive effect on the condition of the guides.

Investigation of the effects of shot overlap and rigid body assumptions on surface layer characteristics in shot peening simulation

As an important mean of shot peening (SP) research, finite element simulation has been widely and successfully employed in estimating the surface characteristic and residual stress distribution after SP treatment. In this study, the effects of shot overlap and rigid body assumptions on dimple geometry and residual stress distribution in depth were discussed via the validated ordered dimple pattern and stochastic dimple pattern SP models for quenched and tempered 42CrMo steel. The results show that shot overlap assumption has a great influence on the surface plastic deformation of peened material. The simulated value of plastic deformation is much larger than the experimental value, which results in the residual stress of the overlapping shot SP model deviating from the actual result seriously. For the prediction of the residual stress distribution, the shot must be set as an elasto-plastic body when the number of shot is large. The shot can be set as a rigid body for the aim of reducing the calculation time when the number of shots is small. In addition, the influence of material hardness on residual stress and equivalent plastic strain (PEEQ) was investigated via simulating the residual stress and PEEQ of different hardness materials treated by SP process . • It is necessary to choose the non-overlapping shot in SP simulation when the dimple geometry and residual stress distribution is predicted. • It is more accurate to choose elasto-plastic shot in SP model for the dimple geometry prediction. • The shot can be set as a rigid body when the number of shot is small.