Microscopic Topography Research Articles

Three-Dimensional Evaluation of Microscopic Wheel Surface Topography in Creep Feed Grinding Using Ceramics Grinding Wheel

The surface topography of ceramic grinding wheels used in creep feed grinding is examined in this study. Creep feed grinding experiments are performed using seeded gel (SG) grinding wheels. The three-dimensional surface of the grinding wheel is observed using a two-dimensional high-definition laser displacement sensor, and the effective cutting-edge number is calculated based on three-dimensional surface observations. Microscopic wear behaviors of grain cutting edges are examined based on scanning electron microscope (SEM) images. The cutting-edge area percentage is calculated based on SEM images via the discriminant analysis method. Results show that the micro self-sharpening phenomenon can be evaluated quantitatively. Micro sharp cutting edges on grains and normal grinding forces are suppressed. Subsequently, the relationship between the grinding characteristics and behaviors of the SG wheel working surface is investigated.

Fractal Research on Surface Topography of Profile Milling CFRT

Carbon Fiber Reinforced Thermoplastic Composites (CFRT) are recognized as a new generation of advanced strategic materials due to their excellent mechanical properties and high recycling rate. However, in the milling process, affected by the coupling of force and thermal, the heat-sensitive resin in CFRP is easily softened and deformed, leading to difficulties in achieving high-quality material removal. Especially in the complex and long-period surface milling process, the processed surface has a complex and irregular microscopic topography, hard to be accurately characterized by traditional roughness measurement methods. To evaluate the surface quality of CFRT profile after milling more precisely, in this paper, the influence of cutting parameters on fractal dimension is systematically analyzed by solving the image gray surface based on the fractal dimension algorithm and calculating the fractal dimension of the surface after milling via the variational method. The experimental results show that the surface fractal dimension of thermoplastic composites processed by PCD milling cutter is between 2.46 and 2.52, and the sensitivity ranking of fractal dimension to cutting parameters is: v f<A e<A p.

Photo-induced stress relaxation in reconfigurable disulfide-crosslinked supramolecular films visualized by dynamic wrinkling

Stress relaxation in reconfigurable supramolecular polymer networks is strongly related to intermolecular behavior. However, the relationship between molecular motion and macroscopic mechanics is usually vague, and the visualization of internal stress reflecting precise regulation of molecules remains challenging. Here, we present a strategy for visualizing photo-driven stress relaxation induced by infinitesimal perturbations in the intermolecular exchange reaction via reprogrammable wrinkle patterns. The supramolecular films exhibit visible changes in microscopic wrinkle topography through ultraviolet (UV)-induced dynamic disulfide exchange reaction. In accordance with the trans-scale theoretical models, which quantitatively evaluate the chemical-dependent mechanical stresses in the supramolecular network, the unexposed disordered wrinkles evolved into highly oriented patterns and underwent subsequent mutations after thermal treatment. The stress-sensitive wrinkle macro-patterns can be repetitively written/erased through network topology rearrangement using different stimuli. This strategy provides an approach for visualizing and understanding the molecular behavior from dynamic chemistry to mechanical changes, and directly programming wrinkle patterns with regulated structures.

Synthesis of Ce0.1La0.9MnO3 Perovskite for Degradation of Endocrine-Disrupting Chemicals under Visible Photons

The UN Environmental Protection Agency has recognized 4-n-Nonylphenol (NP) and bisphenol A (BPA) as among the most hazardous chemicals, and it is essential to minimize their concentrations in the wastewater stream. These industrial chemicals have been witnessed to cause endocrine disruption. This report describes the straightforward hydrothermal approach adopted to produce Ce0.1La0.9MnO3 (CLMO) perovskite’s structure. Several physiochemical characterization approaches were performed to understand the Ce0.1La0.9MnO3 (CLMO) perovskite crystalline phase, element composition, optical properties, microscopic topography, and molecular oxidation state. Here, applying visible photon irradiation, the photocatalytic capability of these CLMO nanostructures was evaluated for the elimination of NP and BPA contaminants. To optimize the reaction kinetics, the photodegradation of NP and BPA pollutants on CLMO, perovskite was studied as a specification of pH, catalyst dosage, and initial pollutant concentration. Correspondingly, 92% and 94% of NP and BPA pollutants are degraded over CLMO surfaces within 120 and 240 min, respectively. Since NP and BPA pollutants have apparent rate constants of 0.0226 min−1 and 0.0278 min−1, respectively, they can be satisfactorily fitted by pseudo-first-order kinetics. The decomposition of NP and BPA contaminants is further evidenced by performing FT-IR analysis. Owing to its outstanding photocatalytic execution and simplistic separation, these outcomes suggest that CLMO is an intriguing catalyst for the efficacious removal of NP and BPA toxicants from the aqueous phase. This is pertinent for the treatment of endocrine-disrupting substances in bioremediation.

Evaluating the impact of ultraviolet C exposure conditions on coliphage MS2 inactivation on surfaces.

The COVID-19 pandemic has raised interest in using devices that generate ultraviolet C (UVC) radiation as an alternative approach for reducing or eliminating microorganisms on surfaces. Studies investigating the efficacy of UVC radiation against pathogens use a wide range of laboratory methods and experimental conditions that can make cross-comparison of results and extrapolation of findings to real-world settings difficult. Here, we use three different UVC-generating sources - a broad-spectrum pulsed xenon light, a continuous light-emitting diode (LED), and a low-pressure mercury vapour lamp - to evaluate the impact of different experimental conditions on UVC efficacy against the coliphage MS2 on surfaces. We find that a nonlinear dose-response relationship exists for all three light sources, meaning that linear extrapolation of doses resulting in a 1-log10 (90%) reduction does not accurately predict the dose required for higher (e.g. 3-log10 or 99.9%) log10 reductions. In addition, our results show that the inoculum characteristics and underlying substrate play an important role in determining UVC efficacy. Variations in microscopic surface topography may shield MS2 from UVC radiation to different degrees, which impacts UVC device efficacy. These findings are important to consider in comparing results from different UVC studies and in estimating device performance in field conditions.

Characterization of diffractive relief structures over large areas by stitching interference microscopic topography

The development of diffractive optical elements (DOEs)enables fascinatingly compact design and chromatic aberration correction. Fabrication errors of DOEs include periodic pattern error, relief profile error and roughness which affect imaging quality and diffraction efficiency. Characterization of the DOE requires thus multi-scale measurement of the surface topography over the full aperture of 10 mm scale. This paper presents a method based on the white light interferometry in combination of subaperture stitching. Firstly, the principle of measurement and subaperture layout design is introduced. The measuring system is easily set up by integrating a scanning platform with the interference microscope. Subaperture stitching algorithm is developed based on the surface height change related to the scanning motion error. The slope of the relief profile is used to model the deviations of overlapping point pairs induced by lateral shift and rotation. Finally, the topography and fabrication error of a Fresnel lens surface are experimentally obtained and characterized over the full aperture through stitching of totally 67 subapertures.

Vibration Characteristics of Rotor System with Loose Disc Caused by the Insufficient Interference Force

The rotating parts looseness is one of the common failures in rotating machinery. The current researches of looseness fault mainly focus on non-rotating components. However, the looseness fault of disc-shaft system, which is the main work part in the rotor system, is almost ignored. Here, a dynamic model of the rotor system with loose disc caused by the insufficient interference force is proposed based on the contact model of disc-shaft system with the microscopic surface topography, the vibration characteristics of the system are analyzed and discussed by the number simulation, and verified by the experiment. The results show that the speed of the shaft, the contact stiffness, the clearance between the disc and shaft, the damping of the disc and the rotational damping have an influence on the rotation state of the disc. When the rotation speed of the disc and the shaft are same, the collision frequency is mainly composed of one frequency multiplication component and very weak high frequency multiplication components. When the rotation speed of the disc and the shaft is close, the vibration of the disc occurs a beat vibration phenomenon in the horizontal direction. Simultaneously, a periodical similar beat vibration phenomenon also occurs in the waveform of the disc-shaft displacement difference. The collision frequency is mainly composed of a low frequency and a weak high frequency component. When the rotation speed of the disc and the shaft has great difference, the collision frequency is mainly composed of one frequency multiplication, a few weak high frequency multiplication components and a few low frequency multiplication component. With the reduction of the relative speed of the disc, the trajectory of the disc changes from circle-shape to inner eight-shape, and then to circle-shape. In the inner eight-shape, the inner ring first gradually becomes smaller and then gradually becomes larger, and the outer ring is still getting smaller. The obtained research results in this paper has important theoretical value for the diagnosis of the rotor system with the loose disc.

Study on Surface Integrity and Surface Roughness Model of Titanium Alloy TC21 Milling Considering Tool Vibration

Due to its excellent strength, plasticity, and fracture toughness, titanium alloy has been widely used in the aerospace field. The specificity of its application environment places high demands on the surface quality of titanium alloy. In this paper, we study the effects of different lubrication methods on the microscopic topography, surface roughness, and microhardness of titanium alloy TC21 during the milling process. The lubrication methods include dry, high-pressure air cooling, and minimum quantity lubrication (MQL). Compared with dry milling and high-pressure air cooling conditions, the MQL environment can effectively suppress plastic deformation and surface defects of titanium alloy TC21. MQL is significant for improving the milling process of titanium alloy TC21. In addition, a surface roughness model considering milling vibration is developed. According to the results of orthogonal experiments, the prediction accuracy of the surface roughness model is acceptable, and the prediction errors are all below 20%.

Study on the effect of ultrasonic vibration-assisted polishing on the surface properties of alumina ceramic

Due to the excellent biocompatibility and chemical durability, alumina ceramics are widely used in biomedical fields such as dentistry. Meanwhile, the high hardness and brittleness of the alumina ceramic causes difficulties in ensuring the processing quality of conventional machining methods. Ultrasonic vibration-assisted polishing (UVAP) can effectively improve the surface quality of hard and brittle materials as a novel machining method. The surface properties of the alumina ceramic for different ultrasonic amplitudes are obtained in this study. The evaluation of the surface properties includes microscopic topography, frictional property, surface hardness, microscopic strain, and surface roughness. In addition, a surface roughness model of the alumina ceramic is built based on the UVAP machining mechanism. The model considers the effect of different types of abrasive particles (free and fixed abrasive particles) on the material removal mechanism. The experimental results show that the errors of the predicted model are less than 20%. This work will provide some ideas for the subsequent UVAP processing.

Ta2O5-doped TiO2 nanotubes on Ti6Al4V alloy with improved cytocompatibility to endothelial cells

Microscopic topography and chemical composition of implant surface play critical roles in cellular response. In this work, Ta2O5-doped TiO2 nanotubes (Ta2O5/TiO2 NTs) were prepared on Ti6Al4V (TC4) to improve its cytocompatibility to endothelial cells. Firstly, a Ta diffusion layer on TC4 (Ta/TC4) was designed by plasma surface Ta-alloying. Then, a Ta2O5/TiO2 NTs film was grown on Ta/TC4 by anodization. The surface morphology, phase composition, and microstructure of the obtained samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Ta incorporation leads to the lamellar microstructure (α'+β) of Ta/TC4 and the lamellar distribution of Ta2O5/TiO2 NTs. In vitro assays demonstrate that the synergistic effect of Ta2O5 addition and biomimetic nanostructure is responsible for the enhanced proliferation, adhesion, cytoskeletal assembly, and spreading of endothelial cells on Ta2O5/TiO2 NTs. The excellent cytocompatibility of Ta2O5/TiO2 NTs highlights its potential in biomedical applications.

A novel multiscale model for contact behavior analysis of rough surfaces with the statistical approach

This paper presents a contact model to describe the normal and tangential contact behaviors of the rough interface with multiscale topographies. The coupling effect of macroscopic profile deviation and mesoscopic roughness on the contact behaviors is taken into account. First, an improved force expression of single contacting asperity is proposed to characterize the continuous and monotonic feature in the whole deformation process. By adopting the statistical summation, the contact model for the surface with microscopic topography is established. Second, the mesoscopic waviness deformation is characterized with microscopic asperities through multiscale modeling. The macroscopic geometric deviation is defined as a linear shape function. By combining the macro-, meso-- and microscopic topographies, the multiscale normal contact model is established. Then, in terms of tangential model, the Jenkins element is applied to express the slip-stick behavior of asperity. Based on the normal contact model and Coulomb law, the distribution function of the yield slip force is obtained to establish the tangential contact model. Furthermore, the predicted contact responses are compared with experiments and finite element model to validate the effectiveness of the proposed model. Finally, the influences of the multiscale topographies are analyzed, presenting the variation tendencies of contact responses. This work provides a feasible and effective way for studying the contact response of rough interface with multiscale surface topographies.

A Hybrid Crack Detection Approach for Scanning Electron Microscope Image Using Deep Learning Method.

The scanning electron microscope (SEM) is widely used in the analysis and research of materials, including fracture analysis, microstructure morphology, and nanomaterial analysis. With the rapid development of materials science and computer vision technology, the level of detection technology is constantly improving. In this paper, the deep learning method is used to intelligently identify microcracks in the microscopic morphology of SEM image. A deep learning model based on image level is selected to reduce the interference of other complex microscopic topography, and a detection method with dense continuous bounding boxes suitable for SEM images is proposed. The dense and continuous bounding boxes were used to obtain the local features of the cracks and rotating the bounding boxes to reduce the feature differences between the bounding boxes. Finally, the bounding boxes with filled regression were used to highlight the microcrack detection effect. The results show that the detection accuracy of our approach reached 71.12%, and the highest mIOU reached 64.13%. Also, microcracks in different magnifications and in different backgrounds were detected successfully.

Enhanced lubrication performance of triethanolamine functionalized reduced graphene oxide on the cold‐rolled surface of strips

Triethanolamine functionalized reduced graphene oxide (rGO‐TEA(s)) nanocomposites have been synthesized by the hydrothermal method. The physical and chemical properties of rGO‐TEA(s) with different degrees of functionalization were characterized by transmission electron microscopy, X‐ray powder diffraction, Raman spectroscopy, and X‐ray photon spectroscopy. The cold rolling lubrication of the rGO‐TEA(s) prepared as nano‐lubricant additives were investigated using a two‐high rolling mill. The microscopic topographies of rolled strips were measured and evaluated by several physical characterizations. The results showed that the increase of functionalization time was favored to the reaction of triethanolamine and C–O–C groups on the GO surface, whereas the defects and disorder in graphene structure were repaired according to the intensity ratio of the D band to G band from 1.154 to 1.130. The cold rolling experiment results demonstrated that rGO‐TEA(s) exhibited excellent lubrication properties, especially the rolled surface lubricated by rGO‐TEA‐10h presented few defects and minimum roughness value. The admirable lubrication performance of rGO‐TEA‐10h was attributed to the formation of absorption film and consecutive carbonaceous protective film.

Insect Antiadhesive Surfaces Using Electrosprayed Wrinkled Ethyl Cellulose Particles.

A range of plants developed leaves, the surfaces of which prevent or diminish insect adhesion due to their microscopic topography. Well known examples include the leaves of the lychee tree (Litchi chinensis). Here, we report a method to coat substrates with ethyl cellulose microparticles that exhibit wrinkled surfaces, resulting in surface morphologies that closely resemble those of insect repelling plants, i.e., Litchi chinensis. The microparticles were prepared by electrospraying, a method that allowed tuning of the particle size and surface morphology. By measuring the traction forces of Colorado potato beetles walking on these surfaces, the wrinkly microsphere parameters were optimized, resulting in biomimetic surfaces that surpass the antiadhesive properties of the biological role model. This study may pave the way to sustainable, nontoxic insecticide replacements.

Effect of acid and alkali solutions on micro-components of coal

To solve the problem of crack closure and low porosity in the deep rock strata of the energy industry, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy experiments were conducted on coal samples soaked in hydrochloric acid and sodium hydroxide. The effects of strong acids and alkalis on organic functional groups and material changes with coal are studied. Microscopic scale surface topography changes of coal bodies were studied. The results showed that both hydrochloric acid (HCl) and sodium hydroxide (NaOH) could effectively dissolve kaolinite in coal samples. The higher the concentration of the solution, the more pronounced the erosion effect on the coal. However, neither of them can eliminate kaolinite. Hydrochloric acid is mainly sensitive to the carboxyl and oxygen-containing structural, functional groups in coal. Sodium hydroxide is primarily sensitive to the hydroxyl and aromatic structures. The hydrochloric acid has less influence on the surface topography of the coal body and can effectively remove surface particles on the coal body, thus making the surface smoother. Sodium hydroxide can remove surface particles; it also produces a large amount of sediment attached to the surface. Solution holes were created on the surface of the coal body.

Analysis of complex modal instability of a minimal friction self-excited vibration system from multiscale fractal surface topography

In order to reveal the stability and nonlinear characteristics of the friction self-excited vibration system from the perspective of microscopic multiscale fractal surface topography, a minimal two-degree-of-freedom mathematical model of the disc brake system is established in this paper. Considering the fractal characteristics of rough surface topography, the fractal contact stiffness of contact surfaces is introduced into the system model from the perspective of microscopic contact, and the effects of two important surface fractal parameters, fractal dimension D and fractal roughness G, on the stability and nonlinearity of the system are analyzed. Further finite element analysis and brake noise test improve the analysis of system stability and noise intensity by different surface topographies. The results show that the system stability can be improved with the increase of fractal dimension within a certain range, and the system will be in a stick state with the further increase of fractal dimension. With the increase of fractal roughness, the unstable modal coupling region of the system is increasing, which can reduce the stability of the system. The unstable region of the system is dependent on fractal dimension and fractal roughness, and has different sensitivity to them.

Triaxiality effects on hydrogen-assisted micro-damage (HAMD), notch tensile strength and hydrogen embrittlement of pearlitic steel

This paper offers a detailed analysis of the hydrogen-assisted micro-damage (HAMD) region in axisymmetric round-notched samples of high-strength eutectoid pearlitic steel under hydrogen embrittlement environmental conditions. Emphasis is placed on the microscopic appearance and the evolution of such a microscopic topography from the initiation (sub-critical) to the fracture (critical) point. The use of very different notched geometries —with the subsequent various triaxial stress distributions in the vicinity of the notch tip— allows an analysis of the influence of stress state on hydrogen diffusion and micro-cracking. In all cases, the microscopic appearance of the hydrogen-affected zone resembles micro-damage, micro-cracking or micro-tearing due to hydrogen degradation, thereby affecting the notch tensile strength and producing hydrogen embrittlement.

Microscopic scan-free surface profiling over extended axial ranges by point-spread-function engineering.

The shape of a surface, i.e., its topography, influences many functional properties of a material; hence, characterization is critical in a wide variety of applications. Two notable challenges are profiling temporally changing structures, which requires high-speed acquisition, and capturing geometries with large axial steps. Here, we leverage point-spread-function engineering for scan-free, dynamic, microsurface profiling. The presented method is robust to axial steps and acquires full fields of view at camera-limited framerates. We present two approaches for implementation: fluorescence-based and label-free surface profiling, demonstrating the applicability to a variety of sample geometries and surface types.

Influence of different rhombic surface textures on the tribological performance of water-lubricated bearings

Water lubrication has gradually replaced oil lubrication for a wide range of marine stern bearings. However, due to poor water carrying capacity, the tribological performances of water lubricated bearings can be improved by incorporating surface textures. In this work, rhombic textured thermoplastic polyurethane (TPU) specimens, 3D-printed with different heights/depths, 1 mm bulge, 0.5 mm bulge, 0.5 mm dimple, and 1 mm dimple, were tested for their tribological performances when they were lubricated by water and were compared to nontextured specimens. The friction coefficient, wear mass, and microscopic surface topography of the specimens were collected at a common working load (0.4 MPa) and speed (from 50 to 350 rpm), and at low-speed and heavy load (50 rpm and 0.8 MPa) conditions. Experimental results reflect that the rhombic surface texture can effectively improve the friction and wear performances of TPU materials. The friction coefficients of most textured specimens are smaller than those of non-textured specimens under various working conditions. The surface wear conditions of all textured specimens are superior to non-textured specimens, since the rhombic surface texture produces additional hydrodynamic lubrication by creating converge and cavitation effects and prevents abrasive particles from accumulating on the friction surface. Through experimental demonstration, the 1 mm bulge rhombic texture is the best of all the tested textured specimens. This finding can provide a reference for practical industrial applications.

Thermal contact conductance between balls and bearing rings

The thermal contact conductance (TCC) between balls and bearing rings is predicted by proposing the TCC model between the curved and spherical surfaces. The Weierstrass-Mandelbrot function is applied to characterize the microscopic topography of surfaces. The fractal contact model is constructed by considering the elastic, elastic-plastic, and plastic deformations of microprotrusions, and then an effective contact coefficient is built to modify the fractal contact parameters. Finally, the TCC modeling method is proposed by considering the elastic and plastic TCCs of different contacting microprotrusions with different sizes. The experiments of TCCs were conducted under different conditions to verify the validity of the proposed model. The results show that the predicted TCCs fit well with measured values and that the predictive accuracy can be improved greatly by considering the effective contact coefficient. Then the effect of critical factors on TCCs is discussed, and the TCC increases with the external load, and increases with the fractal dimension D and decreases with the scaling constant G. The TCC of the dynamic lubricated ball bearing is much greater than that of the static lubricated ball bearing and the TCC of the static lubricated ball bearing is much greater than that of the static non-lubricated ball bearing.