Surface Height Distribution Research Articles

Microscopy-based infrared spectroscopy as a tool to evaluate the influence of essential oil on the surface of loaded bilayered-nanoparticles

Increasing interest in nanoparticles of technological application has been improving their fabrication processes. The encapsulation of essential oils as bioactive compounds has proved to be an excellent alternative to the use of less environment friendly compounds. However, the difficulty of identifying their constitution and interaction with carrier agents have aroused scientific interest and a problem to overcome. Bilayer-based nanoparticles were developed using gelatin and poly-ε-caprolactone (PCL) aiming the encapsulation of Piper nigrum essential oil. based on atomic force microscopy images and dynamic light scattering analysis, the size of the unloaded and loaded nanoparticles was found around (194 ± 40) and (296 ± 54) nm, respectively. The spatial patterns revealed that the surface of nanoparticles presented different surface roughness, similar shapes and height distribution asymmetry, lower dominant spatial frequencies, and different spatial complexity. Traditional infrared spectroscopy allowed the identification of the nanoparticle outermost layer formed by the gelatin carrier, but microscopy-based infrared spectroscopy revealed a band at 1742 cm−1 related to the carbonyl stretching mode of PCL, as well as a band at 1557 cm−1 due to the amide II group from gelatin. The combination of microscopy and spectroscopy techniques proved to be an efficient alternative to quickly identify differences in chemical composition by evaluating different functional groups in bilayer PLC/gelatin nanoparticles of technological application.

Research on wear characteristics of abrasive belt and the effect on material removal during sanding of medium density fiberboard (MDF)

Sanding is a key process for the manufacture and application of medium density fiberboard (MDF). In this paper, the wear characteristics of abrasive belt and the impact on material removal were studied. The topological features which included surface roughness and height distribution were statistically analyzed. Specifically, interference ratio $$\varphi$$ was introduced to evaluate the proportion of the actually involved grits, which was characterized by a significant correlation with the material removal. It was found that there were roughly three phases in the lifecycle of abrasive belt. Fracture and abrasion were the predominant wear patterns of the involved grits that was 68.6% on average. The grits dropping off the backing layer could be observed with 29.8%. Not involved grits accounted for roughly 31.4%. The grey relevancy analysis (GRA) indicated a morphology transfer phenomenon between the workpiece and the belt, while the surface roughness displayed a weak correlation with the material removal.

Mixed elastohydrodynamic lubrication model of rotary lip seal with non-Gaussian surfaces: experimentation verification and numerical analysis on effects of sealed pressure.

Many published models can be used to analyse the sealing performance of rotary lip seal. The surfaces are normally assumed to be periodic variation. However, the quasi-randomness of surface height distribution should be considered, especially the non-Gaussian distribution. Hence, a mixed elastohydrodynamic lubrication model with non-Gaussian surfaces is proposed and used to analyse the effects of sealed fluid pressure on the seal performance in this paper. Based on digital filter and Johnson's translator system, a rough surface simulation method is introduced to simulate non-Gaussian rough surface. Based on this method the mixed lubrication model with non-Gaussian surfaces is built. The proposed model is verified by comparing the simulation results to experimental observations. Furthermore, it is hardly to find the research focused on the effects of sealed pressure. Hence, the effects of sealed fluid pressure on the seal performance is focused.

Multifeature Extraction of Three‐Dimensional Topography of Carbon Steel Specimen during Fatigue Process

In order to investigate the variation of three‐dimensional metal surface topography during fatigue process, a three‐dimensional (3D) topography acquisition platform was built with an in situ tensile tester and a three‐dimensional profilometer. Q235 steel specimens were chosen as research objects, and the three‐dimensional surface topography information at various stages of fatigue damage was obtained. Through the characterization of three‐dimensional roughness, combined with surface height distribution and multifractal analysis, the variations of metal surface topography in the fatigue process were described. Results show that the arithmetic mean deviation of the surface (Sa), the width of the multifractal spectrum (Δα), and the mean value of surface height distribution (μ) and its standard deviation (δ) increase nonlinearly with the increase of fatigue cycles. The rate of fatigue damage is slow in the early stage and high in the middle and late stages. The surface height distribution amplitude (A) decreases with the increase of fatigue cycles, which indicates that the height data concentration decreases, and the metal surface becomes uneven. The Bayesian data fusion method was applied to establish a nonlinear mapping between the topography features and the damage, with the above five characteristic parameters (Sa, Δα, A, μ, and δ) as the data layer. Finally, a surface topography feature fusion method is proposed, and a case study is conducted to verify its applicability. The research results can provide reference for fatigue damage assessment.

Impact of surface morphologies of substrates on the epitaxial growth of magnetron-sputtered (ZnO)x(InN)1-x films

The effects of substrates on the growth of sputter-deposited (ZnO)x(InN)1-x (called “ZION” hereinafter) films have been investigated. We defined the figure of merit (FOM) of ZION films as the reciprocal of the product of full width at half maximum of X-ray rocking curves and root mean square (RMS) roughness. No clear correlation between the FOM and the RMS roughness of the substrates is observed; however, interestingly, a strong correlation between the FOM and the “skewness” of the surface height distribution of the substrates is observed. A possible reason for this is that the existence of a small portion of spikes on the surface, which appear as tiny tails in the distribution but are not reflected in the RMS roughness, limits the migration of adatoms and/or leads to secondary nucleation, degrading the quality of the subsequently grown ZION films. In addition, an atomically flat single-crystalline ZION film is grown on a ZnO template with a small skewness of 0.04.

Big-and-dull or small-and-sharp: A comparison of specific energy, wheel wear, surface-generation mechanisms and surface characteristics when grinding with Al2O3 and CBN to achieve a given surface roughness

• For the same R a , small & sharp give much lower specific energies than big & dull. • For the same R a , small & sharp give slightly lower R t values than big & dull. • Ground surfaces are Gaussian, for all grit sizes and dressing. • The normalized grit shear stress is the force per grit per unit grit area. • Larger, dull-dressed CBN requires frequent dressing. An investigation was made into the effect of grit size and dressing conditions on specific energy, surface-finish characteristics and wheel wear, with a focus on whether smaller, sharp-dressed grits and larger, dull-dressed grits produce different specific energies and surface-finish distributions, even for the same R a surface-roughness. Grinding tests were performed and measurements were made of grinding forces, wheel wear, R a , R t and surface-height distributions. Observations were made of SEM photos of ground surfaces. Results show that, for a given R a surface roughness, smaller, sharp-dressed Al 2 O 3 grits give significantly lower specific energies and slightly lower R t values than larger, dull-dressed grits over a large range of grit sizes. This has significant implications in terms of thermal-damage risk and cycle times. Also, using larger, dull-dressed CBN grits requires too-frequent dressing in order to maintain surface roughness. A new concept is developed, the nominal bond shear stress , which can be used to quantify the risk of grit fracture or bond fracture in a single grit. The fundamental relationships between grit size, grit sharpness and contact mechanisms are discussed and practical recommendations are given.

Finite Element Study of the Effect of Internal Cracks on Surface Profile Change due to Low Loading of Turbine Blade

Turbine blades for thermal power plants are exposed to severe environments, making it necessary to ensure safety against damage, such as crack formation. A previous method detected internal cracks by applying a small load to a target member. Changes in the surface properties of the material were detected before and after the load using a digital holographic microscope and a digital height correlation method. In this study, this technique was applied in combination with finite element analysis using a 2D and 3D model simulating the turbine blades. Analysis clarified that the change in the surface properties under a small load varied according to the presence or absence of a crack, and elucidated the strain distribution that caused the difference in the change. In addition, analyses of the 2D model considering the material anisotropy and thermal barrier coating were conducted. The difference in the change in the surface properties and strain distribution according to the presence or absence of cracks was elucidated. The difference in the change in the top surface height distribution of the materials with and without a crack was directly proportional to the crack length. As the value was large with respect to the vertical resolution of 0.2 nm of the digital holographic microscope, the change could be detected by the microscope.

Investigation of the Impact of Pad Surface Texture from Different Pad Conditioners on the CMP Performance

Chemical mechanical polishing (CMP) is a common method for planarization/polishing materials during integrated circuits (IC) fabrication. Pad conditioning is a critical component of a CMP process. Herein, the impact of surface textures created by different types of pad conditioners (PC) such as coarse, mid-coarse, and fine PC on the solid pads are studied. Additional surface texture parameters such as surface height distribution, skewness, Dale Void Volume are used to determine an optimum surface texture that gives desired CMP performance such as material removal rate and within-wafer non-uniformity. It was determined that an optimum surface texture on a solid CMP pad can be obtained with a mid-coarse disk. It is further demonstrated that by the addition of porosity to the pads, it is possible to recreate an optimum surface texture and desired CMP performance, similar to that obtained with a mid-coarse disk and a solid pad. Tribological mechanisms of the different pad and PC combinations are presented using the coefficient of friction. It is concluded that porous pad and fine PC pairing can tackle the issues of slurry transport limitations, lack of asperity contact, and process stability over pad life.

Validation of ICESat-2 Surface Water Level Product ATL13 with Near Real Time Gauge Data

The NASA’s Ice, Cloud, and land Elevation Satellite (ICESat) mission uses laser altimetry measurements to determine the elevations at point levels of Earth. ICESat-2, which is a successor to the ICESat-1 satellite mission is a continuation of this series and carries a sensor namely Advanced Topographic Laser Altimeter System (ATLAS). The key advancement of ICESat-2 is that it generates individual laser foot prints of nearly 14 m (in diameter) on the Earth’s surface, with each footprint separated by only 70 cm, a much higher resolution and sampling than the earlier mission. ATLAS works under the concept of multi-beam approach containing three pairs of strong and weak beams that produce data products containing global geolocated photon data and height data from land-ice, sea-ice, land/terrain, canopy, ocean surface, and inland water-bodies. From the Level 2 master product called ATL03 numerous sub-data product are generated and are made available to the public through the National Snow and Ice Data Center. One of the products namely ATL13 is a specialized geophysical data product that gives along-track and near-shore water surface height distribution within the water masks. In this article, results after validating ATL13 data product with 46 observations made with near real-time gauged data for 15 reservoirs/water bodies have been presented. The maximum uncertainty observed for this data product is at centimeter-level. A significant observation made from this study is that the heights of surface water level computed from strong beams (gt1r, gt2r, and gt3r) and weak beams (gt1l, gt2l, and gt3l) are occasionally having a variation of 5 to 10 centimeters relatively.

Effect of Bispectrum on Radar Backscattering From Non-Gaussian Sea Surface

The upwind-downwind asymmetry in normalized radar backscattering cross section (NRBCS) from ocean surface is well known; one acceptable and convincing reasoning is explained by the fact that the surface height distribution deviates from Gaussian one, which causes a nonzero skewness function, and consequently affects the radar cross section in up and down wind directions. Specific forms of skewness function, in between Gaussian and exponential, have been proposed in previous studies to account for the upwind/downwind asymmetry in radar backscatter. Attempt is made, through numerical simulation, in this article to examine the impact of these two types of skewness functions on NRBCS. The simulated NBRCSs, with and without skewness contributions, are compared with measured data in upwind and downwind directions at L-, C-, and Ku-bands for different wind speeds. The results indicate that the Gaussian-type skewness function works better to account for the upwind/downwind asymmetry of NBRCS by choosing an appropriate root mean square (RMS) height appearing in skewness function and as the wind speed or radar frequency increases, the RMS height increases but regardless of wind direction and radar incidence angle.

Resistance of curved surfaces to the cavitation erosion produced through high-pressure submerged waterjet

The aim of the present study is to reveal fundamental cavitation erosion characteristics of the curved surface. The submerged waterjet was used to produce cavitation. An experimental work was performed on a standard cavitation erosion test rig. The Al 5083 specimens with three curvature radii, 7.0, 9.0 and 10.0 mm, were selected as the target specimens. The flat surfaces were tested for comparison. The mass loss of the eroded specimens was measured. The cumulative erosion rate was calculated. Morphology of the eroded surfaces was observed using techniques of scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The root mean square (RMS) surface roughness of the eroded specimen was obtained. The results indicate that the curvature radius has a significant effect on the cavitation erosion intensity. The surface with the largest radius of curvature exhibits the weakest resistance to the cavitation erosion. No explicit relevance is recognized between the curvature radius and the extent of the cavitation erosion. In the early stage of the cavitation erosion, the central region of the target surface is less eroded. As the cavitation erosion progresses, the mass removal in the central area manifests a layer-by-layer pattern. Large erosion pits are evidenced in such a region. The specimen of R = 9.0 mm, with the highest resistance to the cavitation erosion, is featured by a sharp decline of the skewness of surface height distribution in the early stage of the cavitation erosion.

Effect of Surface Topography Parameters on Friction and Wear of Random Rough Surface.

In order to explore the relationship between the surface topography parameters and friction properties of a rough contact interface under fluid dynamic pressure lubrication conditions, friction experiments were carried out. The three-dimensional surface topography of specimens was measured and characterized with a profile microscopy measuring system and scanning electron microscope. The friction coefficient showed a trend of decreasing first and then increasing with the increase in some surface topography parameters at lower pressure, such as the surface height arithmetic mean Sa, surface height distribution kurtosis Sku, surface volume average volume Vvv, and surface center area average void volume Vvc, which are the ISO 25178 international standard parameters. The effects of surface topographic parameters on friction were analyzed and the wear mechanism of the worn surface was presented. The wear characteristics of the samples were mainly characterized as strain fatigue, grinding, and scraping. The results provide a theoretical basis for the functional characterization of surface topography.

Experimental validation of contact models for cold-rolling processes

Many functional properties of a cold rolled strip such as wear resistance, friction in a forming process, and optical properties depend on its surface finish. Accurate modelling of the real contact area is critical in predicting the surface finish of strips after cold rolling processes. The aim of this work is to experimentally verify existing contact models to predict the surface finish of industrially cold rolled strips. For this purpose, rolling trials were done on a two high mill under boundary lubricated conditions at several combinations of thickness reduction, rolling speed, and roll and strip roughness. The surface finish of the rolled strip for a given rolling condition is predicted using selected contact models. Further, a new deterministic approach to calculate the average asperity slope is proposed. Statistical properties of the three dimensional surface topography of rolled strips are compared with surfaces predicted employing selected contact models. The surface finish of measured and model-predicted surfaces showed very good agreement for strips rolled with a smooth roll. However, for strips rolled with rough rolls, a significant difference was observed in the surface height distribution between the measured and model-predicted surfaces. It was shown in these experiments that a non-uniform rise of valleys plays an important role on the surface finish of strips rolled with a rough roll.

Effects of loading conditions on free surface roughening of AISI 420 martensitic stainless steel

Free surface roughening affects the tribological behavior of contacting bodies in multistage metal forming processes. This phenomenon was investigated on sheets of AISI 420 martensitic stainless steel by applying uniaxial and radial straining modes via tensile and Erichsen cupping tests, respectively. By means of focus variation microscopy, the free surface roughness evolution was studied for each sample at different values of strain. Moreover, the microscopic deformation of grains was visualized using scanning electron microscopy and differential interference contrast microscopy. The results show that the free surface roughening rate in the uniaxial strain mode is higher than that in the radial one. Furthermore, the surface height distribution of the deformed surfaces was found to be dependent on the deforming strain and tended toward a Gaussian one at higher strains. Grain boundaries and chromium carbide particles were found to be responsible for the peaks formed in the roughened free surfaces. Analyses of the deformed free surfaces showed distortion of the grain morphology, which is the mechanism responsible for free surface roughening.

Topology Optimization of Composite Materials for Wear: A Route to Multifunctional Materials for Sliding Interfaces

Predicting and optimizing the wear performance of tribological systems is of great interest in many mechanical applications. Wear modeling based on elastic foundation models can be used to predict the wear behavior of composite materials. Topology optimization has previously been used to improve the wear performance of a bi‐material composite surface without direct experimental validation. In this paper, three multi‐material composite wear surfaces are presented and fabricated that are the product of topology optimization. The wear surfaces are designed for optimal wear performance including minimized run‐in wear volume lost. In this work, the designs are evaluated with high‐accuracy simulations prior to fabrication. Extensive testing is conducted including for wear volume, wear rate, surface height distribution, and profile measurements throughout the wear process. The effects of boundary conditions and the importance of taking wear sliding directionality into account in the modeling process are discussed.

Roughness of Deposited Carbon-Based Coatings and Its Statistical Characteristics at Nano and Microscales

Topography of surfaces may influence many processes in tribology including friction and adhesion. Its influence is usually taken into account in various statistical models of rough surfaces. Most of these models are based on an explicit or implicit assumption of normality of the asperity heights or similar assumptions that involve Gaussian distributions. Recently it has been shown that the height distribution of surfaces prepared by grinding are not Gaussian at both nano and micro-scales, while topography of epoxy resin replicas of polishing papers having nominal asperity sizes up to several micrometers, was Gaussian. Here we study roughness of carbon-based coatings deposited by direct current pulsed magnetron sputtering with and without substrate bias voltage at micro and nano-scale. Hardness measured using a Berkovich indenter tip gave 43 (biased) and 14 (non-biased) GPa, respectively. First the heights of the nano-asperities were determined by AFM (Atomic Force Microscopy). Then the heights of the micro-asperities were measured by a profilometer (a stylus). Finally the same regions measured by stylus were again studied by AFM. Standard statistical parameters of surfaces are determined at each scale. It has been also shown that the stylus measurements did not cause plastic deformations of the harder (biased) sample because the distributions of heights at nano-scale were the same. Using the experimental data obtained, the assumption of the normal distribution for the roughness heights has been studied by application of various modern tests of normality. Measurements of surfaces by stylus and by AFM with the 117 nm steps showed that the surfaces satisfy the assumption of normality of the heights. However, further studies with the 10 nm AFM steps showed that the roughness of the non-biased sample is not normal. Hence, the applicability of the standard statistical models of adhesive contact between rough solids to the non-biased sample may be questionable.

Numerical simulation of melting dynamic process and surface scale properties of two-dimensional honeycomb lattice

Graphene and other materials have a typical two-dimensional (2D) honeycomb structure. The random fuse model is a statistical physics model that is very effective in studying the fracture dynamics of heterogeneous materials. In order to study the current fusing process and the properties of the fractured surface of 2D honeycomb structure materials such as graphene, in this paper we attempt to numerically simulate and analyze the fusing process and melting profile properties of the 2D honeycomb structure random fuse network. The results indicate that the surface width exhibits a good scaling behavior and has a linear relationship with the system size, and that the out-of-plane roughness exponent displays a global value of <inline-formula><tex-math id="M5003">\begin{document}$\alpha = 0.911 \pm 0.005$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20181774_M5003.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20181774_M5003.png"/></alternatives></inline-formula> and a local value of <inline-formula><tex-math id="M5004">\begin{document}${\alpha _{{\rm{loc}}}} = 0.808 \pm 0.003$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20181774_M5004.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20181774_M5004.png"/></alternatives></inline-formula>, approximate to those of the materials studied. The global and local roughness and their difference indicate that the fusing process and the fracture profile exhibit significant scale properties and have a strange scale. On the other hand, by analyzing the extreme values of the fused surface with different system sizes, the extreme heights can be collapsed very well, after a lot of trials and analysis, it is found that the extreme statistical distribution of the height of the fused surface can well satisfy the Asym2sig type distribution. The extreme height distributions of fracture surfaces can be fitted by Asym2Sig distribution, rather than the three kinds of usual extreme statistical distributions, i.e. Weibull, Gumbel, and Frechet distributions. The relative maximal and minimum height distribution of the fused surface at the same substrate size have a good symmetry. In the simulation calculation process of this paper, the coefficient matrix is constructed by using the node analysis method, and the Cholesky decomposition is performed on the coefficient matrix, and then the Sherman-Morrison-Woodbury algorithm is used to quickly invert the coefficient matrix, which greatly optimizes the calculation process and calculation. The efficiency makes the numerical simulation calculation and analysis performed smoothly. The research in this paper indicates that the random fuse model is a very effective theoretical model in the numerical analysis of the scaling properties of rough fracture surfaces, and it is also applicable to the current fusing process of the inhomogeneous material and the scaling surface analysis of the fusing surface. In this paper, it is found that materials with anisotropic structure can also find their fracture mode by energization, and the properties of fracture surface can provide reference for the study of mechanical properties of honeycomb structural materials. It is a very effective statistical physical model, and this will expand the field of applications of random fuse models.

Effect of Shaft Surface Roughness on the Performance of Radial Lip Seals

Reduction of leakage from the shaft–radial lip seal conjunction is critical in ensuring enduring performance of entire lubrication system. This paper investigates leakage from three types of shaft surfaces, finished using different manufacturing processes. The measurement of surface topography is conducted in order to determine the pertinent roughness parameters which correspond to the observed sealing performance in real practical applications. It is found that the skewness of the surface topography correlates well with the anecdotal leakage failure rate. To quantify this association, a hydrodynamic model, accounting for shaft roughness in a deterministic manner is developed. The results from the numerical analyses confirm that the lubricant mass flow rate is reduced in the case of negatively skewed surface height distributions, when compared with the positively skewed profiles.

Study on contact performance of ultrasonic-assisted grinding surface

The contact performance of ultrasonic-assisted grinding surface is studied in this paper. An improved simplified model of rough surface profile is proposed to find the microscopic feature parameters, such as the curvature radius of the asperity, which are suitable for contact analysis and calculation. Then a more accurate rough surface contact analysis model is obtained by combining the classical ZMC contact model. Based on the contact analysis model, the contact mechanism of ultrasonic-assisted grinding surface is studied. The contact stiffness and local maximum contact pressure of the surfaces under different cutting depths and ultrasonic amplitudes are calculated, and the correlation rule between the parameters of ultrasonic-assisted grinding and the contact performance of the machined surface is obtained: (1) With the increase of the cutting depth, the surface roughness of the workpiece increases; under the same load, the contact stiffness decreases and the maximum local contact pressure increases. (2) With the increase of the ultrasonic amplitude, the surface roughness of the workpiece first decreases and then increases. Under the same load, the contact stiffness increases first and then decreases, while the maximum local contact pressure resents an opposite variation trend. Under the experimental conditions, the surface contact performance of the workpiece is the best when the ultrasonic amplitude is 4 μm. Additionally, the contact performance of the ultrasonic-assisted grinding surface and the conventional grinding surface is compared: (1) When the ultrasonic amplitude is 4 μm, the surface roughness of the workpiece is at least 24% lower than that of the conventional grinding surface. (2) Under the same load, the surface contact stiffness of the ultrasonic-assisted grinding surface is increased by at least 68%, and the maximum local contact pressure is reduced by at least 17%. It is found that the interference motion of abrasive particles in the ultrasonic-assisted grinding process makes the surface height distribution more concentrated and the density of asperity increased, which results in a better contact performance compared with the conventional grinding surface.

Building up the database of the Level-2 Java Sea Ecoregion based on physical oceanographic parameters

The Java Sea (JS) is one of the sea with unique characteristic with especially in biodiversity and oceanographic condition. The purpose of this research is to identify the EL into level 2 in Java Sea based on oceanographic condition. The Java Sea, which covers an area of 467,000 Km2 with an average depth of 50m, is located on the Southeastern part of the Sunda Shelf. This research uses the temperature and salinity data provided by the INDESO, the sea surface height (SSH) data downloaded from the HYCOM website, and the level 2 Java Sea ecoregion shape file data from the Indonesian seas delineation team. The physical oceanographic conditions of the level 2 Java Sea ecoregions are influenced by the moonsun and their respective geographical positions. The results showed that the distribution of temperature, sea current, salinity, and Sea Surface Height differed in each Java Sea Ecoregion level 2 because it is influenced by the geographical and astronomical location of each Java Sea Ecoregion level and influenced by the monsoon that exists over Indonesia. In the east of Java Sea influence from Makassar Strait and in the west affected by Karimata Strait. Within the region, EL 6.1. (Sunda Strait), the physical oceanography condition is slightly different from other Java EL because it is strongly influenced by the Indian Ocean.