Surface Profile Research Articles

Phase-field simulation study on dendritic growth behavior during bilateral directional solidification

The directional solidification technique can uniform the crystal growth direction within the material, but does not remove the lateral side branches of the axial main arm during the growth process. The influence of such lateral side branches existing in the directionally solidified dendritic organisation on the mechanical properties of the material cannot be neglected. In this paper, based on the Kim-Kim-Suzuki (KKS) phase-field model, the competitive behaviour of lateral secondary dendrites between the two main arms under different boundary conditions and non-synchronous growth conditions is investigated for Fe-0.5 %C alloys. In addition, the diffusion and enrichment rules of solutes are analysed by the distribution of solutes. The results show that the molten pool is spherical without external force, and the size distribution of the molten pool is as follows: dendrite tip collision zone > dendrite root > dendrite wall, and the solute segregation rule is the same; The spacing of the main arms has little effect on the concentration values between the dendrites, and the solutes are very symmetrically over the entire computational region; The dendrite tip interface concentration during the stable phase of dendrite growth is 0.89 %. Without considering the initial liquid-phase concentration, the concentration in the collision zone at the dendrite tip is approximately twice the concentration at the tip of the dendrite in the stable period, which is 1.28 %, when the bilateral dendrites are encountered. Dendrites always collide preferentially on the centreline of the included angle under non-parallel conditions, and solute-enriched zones also occur on the centreline of the included angle; During the curved surface bilaterally directional solidification process, when the left and right sides have the same shape of surfaces, the solute enrichment at the end of solidification is on the centreline. For the case of a single planar boundary, the solute-enriched region is influenced by the curved surface and is similar to the initial curved surface profile.

Modeling and identification of clamping contact stiffness

The dynamics of thin-walled parts are highly affected by the clamping conditions. Clamping stiffness is a function of c lamping force and surface roughness profiles of the clamp and part. Since the surface profiles cannot be altered, estimating clamping stiffness as a function of the clamping force is essential to simulate vibrations of the machined thin-walled parts. This paper presents the modeling of clamping stiffness as a function of the applied clamping force and material properties. Surface profile parameters are estimated from the identified contact stiffnesses evaluated using the Finite Element (FE) model. The contact stiffnesses are either predicted directly from the proposed mechanics model of the part or estimated from the Fractal surface parameters. It is shown that an average clamping stiffness can be predicted from the Fractal surface parameters, or directly and more accurately from the static model of the clamped part.

Analysis of the Mechanical and Physical Behaviors of 3D-Printed PEEK Structures under Different Parameters

In this study, the mechanical and physical properties of polyetheretherketone (PEEK) material produced through three-dimensional (3D) printing under different production parameters were investigated. For this purpose, the results obtained by applying heat treatment to the produced samples were examined. Comparisons based on mechanical properties were supported by 3D surface profiles and XRD analyses. According to the obtained results, low nozzle diameter and high printing temperature led to an increase of up to 8% in the elastic modulus and up to 33% in tensile strength of the samples. The heat treatment applied in the study increased tensile strength by up to 8% and elastic modulus by up to 9% in samples produced with a low-diameter nozzle. In conclusion, this study aims to provide a dataset for 3D PEEK designs, intending to enhance the performance of PEEK materials that can be used in medical and industrial applications.

Investigating the effects of calcination temperature on porous clay heterostructure characteristics

This study focuses on finding the optimal calcination temperature for synthesizing porous clay heterostructures (PCH). PCH was prepared using montmorillonite at different temperatures (200–800 °C) in a closed N2 environment. Samples were characterized via N2-physisorption, scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) to investigate the influence of calcination temperature. Characterizations show that the PCH composite exhibits an increasing surface profile observed by increasing specific surface area, changes in crystalline phases, porous surface, and varied particle size distribution. The position (degree and wavelength) and intensities of minerals and functional groups in PCH shift with temperature, as observed in both FTIR and XRD. This shows that variables such as heating rate, calcination temperature, and environment affect the structural changes in the clay material. In terms of active phase development, structural behavior, and material strength, the correct calcination temperature proved to be crucial.

Influences of initial voltage and electrode size on propellant surface evolution in a coaxial pulsed plasma thruster

Coaxial pulsed plasma thrusters are well suited for microsatellites, but the discharge therein is radially nonuniform, resulting in uneven propellant ablation that ultimately degrades the thruster performance. This study investigates how the propellant surface evolves during 50 000 discharges in a coaxial pulsed plasma thruster with different outer electrode inner diameters and initial voltages, encompassing the propellant surface profile, concave depth of the propellant, and carbon deposition on the propellant surface. The results show that the propellant surface changes in real time throughout the 50 000 discharges. Increasing the outer electrode inner diameter leads to a proportional increase in the concave depth of the propellant, resulting in unstable ablation, and the increased inward concave depth increases the likelihood of discharge failure. Furthermore, increasing the initial voltage increases the energy density in a unit area of propellant, further contributing to the increase in the concave depth and discharge failure. The energy density distribution on the propellant surface is obtained via simulation, and by comparing the results with experimental data, the critical ablation threshold for the propellant is estimated as being ca. 0.7 J/mm2.

Development of the scientific and pedagogical school of the department “Ground Transport and Technological Complexes”

The scientific article reflects the main stages of the historical development of the scientific and pedagogical school of the cycle “Technology of structural metals. Materials Science”, which is one of the areas of the department “Ground transport and technological complexes”. Employees of the department made a significant contribution to solving practical problems in assessing the effectiveness of existing technological processes for restoring the tread surface profile of wheel pairs of wheels, the proposed processes of face milling and turning when restoring the wheel rim profile, including the use of preliminary induction annealing to improve machinability, optimization of cutting conditions wheels based on linear and nonlinear programming methods. A large amount of research and implementation work has been carried out to improve the repair technology and increase the reliability of the wheel-motor unit of rail crews of railway rolling stock. Issues related to surfacing operations during repairs and increasing the wear resistance of deposited surfaces were considered.At the same time, the teachers of the department conduct training sessions on disciplines at a high methodological level, without which it is impossible to imagine a modern engineer.Over the years of work of the cycle “Technology of Structural Metals. Materials Science” a large number of textbooks, teaching aids, guidelines and manuals on laboratory work and course design, as well as collections of scientific papers, articles and monographs on the main areas of research work were published.The historical digression presented in this article gives an idea of the scientific potential of the department accumulated over many years, which can serve as a reliable basis for further development of new scientific directions.

Axial Load Transfer Mechanism in Fully Grouted Rock Bolting System: A Systematic Review

The main objective of implementing primary ground-controlling methods, such as applying rock bolting systems, is to increase the strength of surrounding rock mass. Among all rock bolting systems, fully grouted rock bolting systems are the most popular and reliable retaining systems due to their simplicity, availability of materials, ease of installation in the field, and cost-effectiveness. While these types of rock bolts experience both axial and shear forces, understanding their response to axial loads remains complex and dependent on several factors. Extensive research has addressed the overall behaviour of the fully grouted rock bolting system, but a systematic review of the axial load transfer mechanism and its impact on overall performance is lacking. This study addresses this gap by employing a bibliometric analysis of 77 peer-reviewed publications to explore the current state of knowledge regarding the axial load transfer mechanism in fully grouted rock bolting systems. The analysis identifies influential journals, publishers, researchers, highly cited articles, and emerging keywords within this field. Furthermore, it reveals three key parameters significantly impacting the axial behaviour: (a) rock mass and boundary conditions, (b) mechanical behaviours of the grouts, and (c) the geometry and surface profile of the rock bolt. These parameters are subsequently discussed in detail, highlighting their influence on the axial performance of the system. Finally, this article concludes by suggesting promising directions for future research.

Corrosion protection characteristics of doped magnetite layers on carbon steel surfaces in aqueous CO2 environments

Magnetite (Fe3O4) corrosion product surface layers can limit uniform corrosion rates of carbon steel in aqueous carbon dioxide (CO2)-saturated environments. However, as Fe3O4 is a semiconductor, localised corrosion can proceed due to galvanic interaction between the Fe3O4 layers and bare steel. In this study, metal dopants were integrated into Fe3O4 layers to mitigate the effects of localised corrosion, whilst maintaining its protective barrier properties. Model Fe3O4 and metal-doped Fe3O4 layers were electrodeposited on carbon steel and immersed in a pH 5, 1 wt% sodium chloride (NaCl), CO2-saturated, 50 °C solution. Under the conditions studied, the incorporation of magnesium into the Fe3O4 layer resulted in reduced localised corrosion when the 3D surface profiles of the underlying carbon steel were measured using white light interferometry.

An atomic force microscope-like dual-stage force controlled fast tool servo for in-process inspection of micro-structured surfaces

This study presents the development of a dual-stage force sensor integrated fast tool servo (FS-FTS) for in-process inspection of micro-structures. With the cutting tool serving as a probe, the measurement principle of the FS-FTS is similar to that of an atomic force microscope (AFM). The force modulation method, inspired by the tapping mode AFM, is employed to detect the weak contact between the cutting tool and the workpiece. The primary stage of the dual-stage FTS is responsible for tracking the surface profile of the micro-structures while the secondary stage offers the high-frequency oscillation to modulate the force signal. An experimental method is proposed to determine the optimal oscillation frequency. The transfer function of the FS-FTS, from the input voltage of the primary stage to the output force of the force detection module, is identified, and a notch filter integrated feedback controller is designed for the force control. With the designed dual-stage FS-FTS and force controller, the tip of the cutting tool could follow the unknown workpiece contour with a specified constant contact force, and the surface profile is obtained through the measured displacement of the primary stage. The feasibility and superiority of the developed system are validated through the in-process inspection of micro-lens with a depth of 19μm. The results demonstrate that the developed FS-FTS realizes the sub-micron profile measurement with a scanning speed of 150μm/min, and the depth of the resulting surface scratches is less than 20 nm.

Controlling the Friction Coefficient and Adhesive Properties of a Contact by Varying the Indenter Geometry

In the present paper, we describe a series of laboratory experiments on the friction between rigid indenters with different geometrical forms and an elastic sheet of elastomer as a function of the normal load. We show that the law of friction can be controlled by the shape of the surface profile. Since the formulation of the adhesive theory of friction by Bowden and Tabor, it is widely accepted and confirmed by experimental evidence that the friction force is roughly proportional to the real contact area. This means that producing surfaces with a desired dependence of the real contact area on the normal force will allow to “design the law of friction”. However, the real contact area in question is that during sliding and differs from that at the pure normal contact. Our experimental studies show that for indenters having a power law profile f(r) = cnrn with an index n < 1, the system exhibits a constant friction coefficient, which, however, is different for different values of n. This opens possibilities for creating surfaces with a predefined coefficient of friction.

Reconstruction of rough surfaces from a single receiver at grazing angle

AbstractThis article develops a method for recovering a one‐dimensional rough surface profile from scattered wave field, using a single receiver and repeated measurements when the surface is moving with respect to source and receiver. This extends a previously introduced marching method utilizing low grazing angles, and addresses the key issue of the requirement for many simultaneous receivers. The algorithm recovers the surface height below the receiver point step‐by‐step as the surface is moved, using the parabolic wave integral equations. Numerical examples of reconstructed surfaces demonstrate that the method is robust in both Dirichlet and Neumann boundary conditions, and with respect to different roughness characteristics and measurement noise.

Late Holocene relative sea-level records from coral microatolls in Singapore

Late Holocene relative sea-level (RSL) data are important to understand the drivers of RSL change, but there is a lack of precise RSL records from the Sunda Shelf. Here, we produced a Late Holocene RSL reconstruction from coral microatolls in Singapore, demonstrating for the first time the utility of Diploastrea heliopora microatolls as sea-level indicators. We produced 12 sea-level index points and three marine limiting data with a precision of < ± 0.2 m (2σ) and < ± 26 years uncertainties (95% highest density region). The data show a RSL fall of 0.31 ± 0.18 m between 2.8 and 0.6 thousand years before present (kyr BP), at rates between − 0.1 ± 0.3 and − 0.2 ± 0.7 mm/year. Surface profiles of the fossil coral microatolls suggest fluctuations in the rate of RSL fall: (1) stable between 2.8 and 2.5 kyr BP; (2) rising at ~ 1.8 kyr BP; and (3) stable from 0.8 to 0.6 kyr BP. The microatoll record shows general agreement with published, high-quality RSL data within the Sunda Shelf. Comparison to a suite of glacial isostatic adjustment (GIA) models indicate preference for lower viscosities in the mantle. However, more high quality and precise Late Holocene RSL data are needed to further evaluate the drivers of RSL change in the region and better constrain GIA model parameters.

Instrumentation and testing for road condition monitoring – A state-of-the-art review

The sensing instrumentation and testing operations routinely implemented in-situ to monitor the condition of both paved (flexible, rigid) and unpaved roads are critically reviewed: image acquisition, appraisal of surface profile and skid resistance, measurement of stress, strain and deflection, execution of tomography tests, evaluation of environmental parameters as well as determination of traffic volume. Further, this state-of-the-art review sheds light on the financial aspects and cost spectra of the different diagnostic procedures. Finally, a systematic literature review highlights trends in recent research and documents that scientific studies have mainly focused on remote imaging, deflection and tomography measurements.

A fractal model of rough surfaces based on ellipsoidal asperities

PurposeThis study aims to use fractal theory to investigate the contact mechanics of two bidirectional anisotropic surfaces, taking into account the friction coefficient of the contact interface. This study introduces a model that centers on normal contact load and contact stiffness, providing an extensive framework to elucidate the interactions between these surfaces.Design/methodology/approachThe research adopts the Weierstrass–Mandelbrot (W-M) function for simulating bidirectional surface profiles. Through the application of elastic-plastic contact theory, it evaluates the contact area and load of a singular asperity across elasticity, elastoplasticity and plasticity phases. The contact load and stiffness of the rough surface are determined using a refined asperity density distribution function, and these findings are juxtaposed with extant models to validate their precision and rationality.FindingsThe study delineates the influence of fractal dimension (D), surface roughness (G), ellipse eccentricity (e) and friction coefficient (µ) on the contact area, load and stiffness. It reveals that the contact area enlarges with the fractal dimension (D) yet diminishes with increased eccentricity (e), roughness (G) and friction coefficient (µ). These elements considerably affect the contact load and stiffness, underscoring their significance in comprehending surface interactions.Originality/valueThis study applies fractal theory to analyze the contact mechanics of bidirectional anisotropic surfaces, considering the geometry and mechanics of ellipsoidal asperities on rough surfaces to develop a contact mechanics model. This model clarifies the deformation of an asperity in normal contact, presenting a more rational alternative to current models.

Adaptive-tracking laser differential confocal freeform surface measurement with high accuracy

This study introduces an adaptive-tracking method for high-precision measurement of freeform surfaces with unknown angles and normal directions. By integrating the laser differential confocal technology with the normal tracking method through a position sensitive detector (PSD), the proposed method achieves precise fixed-focus scanning over large angles. Subsequently, by establishing the zero-crossing and normal constraints, an adaptive-tracking method based on the height and normal direction of the freeform surfaces is presented to realize the adaptive-tracking measurement of freeform surface profiles. Experimental results demonstrate that the peak-to-valley (PV) (3σ) and the root-mean-square (RMS) (3σ) of surface profiles are superior to 39 nm and 13 nm, respectively. This method provides an effective approach for the high-precision and large-angle measurement of freeform surfaces without known expression equations.

Electrochemical Polishing of Ti and Ti6Al4V Alloy in Non-Aqueous Solution of Sulfuric Acid.

This paper reports the results of our study on electrochemical polishing of titanium and a Ti-based alloy using non-aqueous electrolyte. It was shown that electropolishing ensured the removal of surface defects, thereby providing surface smoothing and decreasing surface roughness. The research was conducted using samples made of titanium and Ti6Al4V alloy, as well as implant system elements: implant analog, multiunit, and healing screw. Electropolishing was carried out under a constant voltage (10-15 V) with a specified current density. The electrolyte used contained methanol and sulfuric acid. The modified surface was subjected to a thorough analysis regarding its surface morphology, chemical composition, and physicochemical properties. Scanning electron microscope images and profilometer tests of roughness confirmed significantly smoother surfaces after electropolishing. The surface profile analysis of processed samples also yielded satisfactory results, showing less imperfections than before modification. The EDX spectra showed that electropolishing does not have significant influence on the chemical composition of the samples.

Numerical simulation study of combined shot peening and laser shock peening on surface integrity of Ti-6Al-4V titanium alloy

Combined shot peening and laser shock peening (CSP) can introduce high surface compressive residual stress (CRS) and deep CRS layer, and reduce the high surface roughness caused by shot peening. The relationship between CSP sequences and surface integrity, including CRS and surface roughness, is far from satisfying the actual demand. In this paper, we construct a finite element model considering initial surface profile features. The experimental results agree with the simulated results. Based on the simulation results, axial and longitudinal stress wave transfer effects on surface CRS and depth CRS are investigated. Compared with shot peening (SP) and laser shock peening (LSP) alone, CSP treatment can increase CRS depth and CRS magnitude by 1060 μm and 50 ∼ 80Mpa, respectively. In addition, the roughness following CSP treatment is lower than that observed after SP treatment alone, and the roughness varies depending on the sequence of CSP treatment. Specifically, the roughness values for SP, SP + LSP, and LSP + SP are 0.938 ± 0.031 μm, 0.982 ± 0.11 μm, and 1.168 ± 0.093 μm, respectively. The surface morphology, hardness, and simulation results are combined to reveal the reasons for the reduction of surface roughness after CSP treatment. The changes of peaks and valleys after CSP treatment compared with single SP treatment were studied, and the variation trend of surface roughness was further explained.

Investigation of a measurement-based dosimetry approach to beta particle-emitting radiopharmaceutical therapy nuclides across tissue interfaces

Objective. In this work, we present and evaluate a technique for performing interface measurements of beta particle-emitting radiopharmaceutical therapy agents in solution. Approach. Unlaminated EBT3 film was calibrated for absorbed dose to water using a NIST matched x-ray beam. Custom acrylic source phantoms were constructed and placed above interfaces comprised of bone, lung, and water-equivalent materials. The film was placed perpendicular to these interfaces and measurements for absorbed dose to water using solutions of 90Y and 177Lu were performed and compared to Monte Carlo absorbed dose to water estimates simulated with EGSnrc. Surface and depth dose profile measurements were also performed. Main results. Surface absorbed dose to water measurements agreed with predicted results within 3.6% for 177Lu and 2.2% for 90Y. The agreement between predicted and measured absorbed dose to water was better for 90Y than 177Lu for depth dose and interface profiles. In general, agreement within k = 1 uncertainty bounds was observed for both radionuclides and all interfaces. An exception to this was found for the bone-to-water interface for 177Lu due to the increased sensitivity of the measurements to imperfections in the material surfaces. Significance. This work demonstrates the feasibility and limitations of using radiochromic film for performing absorbed dose to water measurements on beta particle-emitting radiopharmaceutical therapy agents across material interfaces.

Geo-constrained clustering of resistivity data revealing the heterogeneous lithological architectures and the distinctive geoelectrical signature of shallow deposits

For all applications, subsurface models should be consistent with all available geological and geophysical knowledge. Current practices for synergistic interpretation of geological and geophysical approaches often rely on purely qualitative comparisons, resulting sometimes in inconsistent findings. This study introduces a procedure for a statistical and geo-constrained clustering of electrical resistivity data derived from Electrical Resistivity Tomography (ERT) to address this gap, providing a quantitative parameterization for site-specific geoelectrical signatures of litho-stratigraphic architectures. Seventeen boreholes and three ERT surface profiles were employed to link geophysical inversion results to geological criteria. Core samples allowed grain size analyses, while geological-statistical clustering of electrical resistivity, driven by the observation of stratigraphic contacts in drilled boreholes, established a parametric relationship between geology and geophysics. The iterative clustering procedure, utilizing a classification algorithm, geological boundary constraints, and granulometric analyses, discriminated six distinct lithological clusters, capturing the lateral and vertical heterogeneity of shallow deposits. Subsequent spatial grouping of anthropogenic materials delineated lithological structures and facilitated the classification and identification of filling materials, silty sands, clayey sands, and clays and silts, each exhibiting distinct resistivity variations. The geo-driven geophysical clustering revealed complex lithological structures, especially paleo-channels, capturing their unique geoelectric footprints. The iterative clustering of geo-constrained resistivity data emerges as a powerful tool for subsurface exploration, contributing significantly to understanding lithological heterogeneity, quantifying statistically-based geoelectrical parametrization of shallow sediments, and evaluating the resistivity signature of different deposits. By bridging the gap between geology and geophysics, this data-driven approach establishes a benchmark for future applications. For instance, in the context of contaminated sites, it can be applied to identify pollutants versus geological heterogeneities.

Fundamental optical constants and anti-reflection coating of melt-grown, polished CsPbBr3 crystals

AbstractLead halide perovskites are notorious for water-sensitivity and low hardness. Consequently, polishing CsPbBr3 crystals to achieve high-quality surfaces is challenging. We present a breakthrough mechanical polishing methodology tailored to the specific needs of these soft, moisture-sensitive semiconductors. Three-dimensional optical surface profiles over ~ 1 mm2 areas demonstrate high-quality surfaces with root-mean-square roughness values (&lt; 10 nm) that are unparalleled for melt-grown CsPbBr3. We additionally delve into the polished wafers’ fundamental optical constants and introduce an anti-reflection coating method, setting new standards for short-wave infrared transparency in CsPbBr3. These pivotal processing guidelines pave the way for advancing halide perovskite applications beyond academic curiosity. Graphical abstract