Influence Of Surface Topography Research Articles

Examination of Interface Asperity and Particle Shape on the Mechanical Behavior of Soil-Structure Interfaces Using 3D Printed Models

The influence of surface topography on the mechanical behavior of soil-structure interfaces over a range of particle sizes and shapes is systematically investigated in this research. 3D printed interfaces with different topographies and uniformly graded 3D printed soil particles and two types of natural sands (Ottawa sand 20/30 and Dolomite sand #1, #2 and #3) were employed and tested. Laboratory investigations showed that the shear strength and volume change responses of the 3D printed interfaces are positively influenced with the increase of the inclination of asperities. The proposed wedge friction model successfully explained the distinct mechanical behaviors of soil-structure interfaces under shearing. A “turning point” was found for the interface shear resistance with the increase of the inclination of asperities. When the surface topography produces passive resistance to the soil, the change of the surface topography has little effect on the interface mechanical behavior. The findings from this research will provide insights for soil-structure interface design and discrete element method (DEM) simulations in considering the mechanical behavior of soil-structure interfaces.

Porous Membranes with Special Wettabilities: Designed Fabrication and Emerging Application

Porous materials have become a burgeoning research interest in materials science because of their intrinsic porous characteristics, versatile chemical compositions, and abundant functionalities. Re...

Estimating Terrain Slope from ICESat-2 Data in Forest Environments

The global digital elevation measurement (DEM) products such as SRTM DEM and GDEM have been widely used for terrain slope retrieval in forests. However, the slope estimation accuracy is generally limited due to the DEMs’ low vertical accuracy over complex forest environments. The Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) mission shows excellent potential for slope estimation because of the high elevation accuracy and unique design of beam pairs. This study aimed to explore the possibility of ICESat-2 data for terrain slope retrieval in the United States forests. First, raw ICESat-2 data were processed to obtain accurate ground surfaces. Second, two different methods based on beam pairs were proposed to derive terrain slopes from the ground surfaces. Third, the estimated slopes were validated by airborne LiDAR-derived slopes and compared with SRTM-derived slopes and GDEM-derived slopes. Finally, we further explored the influence of surface topography and ground elevation error on slope estimation from ICESat-2 data. The results show that the ground surface can be accurately extracted from all scenarios of ICESat-2 data, even weak beams in the daytime, which provides the basis for terrain slope retrieval from ICESat-2 beam pairs. The estimated slope has a strong correlation with airborne LiDAR-derived slopes regardless of slope estimation methods, which demonstrates that the ICESat-2 data are appropriate for terrain slope estimation in complex forest environments. Compared with the method based on along- and across-track analysis (method 1), the method based on plane fitting of beam pairs (method 2) has a high estimation accuracy of terrain slopes, which indicates that method 2 is more suitable for slope estimation because it takes full advantage of more ground surface information. Additionally, the results also indicate that ICESat-2 performs much better than SRTM DEMs and GDEMs in estimating terrain slopes. Both ground elevation error and surface topography have a significant impact on terrain slope retrieval from ICESat-2 data, and ground surface extraction should be improved to ensure the accuracy of terrain slope retrieval over extremely complex environments. This study demonstrates for the first time that ICESat-2 has a strong capability in terrain slope retrieval. Additionally, this paper also provides effective solutions to accurately estimate terrain slopes from ICESat-2 data. The ICESat-2 slopes have many potential applications, including the generation of global slope products, the improvement of terrain slopes derived from the existing global DEM products, and the correction of vegetation biophysical parameters retrieved from space-borne LiDAR waveform data.

The Influence of Surface Topography and Wettability on Escherichia coli Removal from Polymeric Materials in the Presence of a Blood Conditioning Film.

The reduction of biofouling and the reduction of cross-contamination in the food industry are important aspects of safety management systems. Polymeric surfaces are used extensively throughout the food production industry and therefore ensuring that effective cleaning regimes are conducted is vital. Throughout this study, the influence of the surface characteristics of three different polymeric surfaces, polytetrafluoroethylene (PTFE), poly(methyl methacrylate) (PMMA) and polyethylene terephthalate (PET), on the removal of Escherichia coli using a wipe clean method utilising 3% sodium hypochlorite was determined. The PTFE surfaces were the roughest and demonstrated the least wettable surface (118.8°), followed by the PMMA (75.2°) and PET surfaces (53.9°). Following cleaning with a 3% sodium hypochlorite solution, bacteria were completely removed from the PTFE surfaces, whilst the PMMA and PET surfaces still had high numbers of bacteria recovered (1.2 × 107 CFU/mL and 6.3 × 107 CFU/mL, respectively). When bacterial suspensions were applied to the surfaces in the presence of a blood conditioning film, cleaning with sodium hypochlorite demonstrated that no bacteria were recovered from the PMMA surface. However, on both the PTFE and PET surfaces, bacteria were recovered at lower concentrations (2.0 × 102 CFU/mL and 1.3 × 103 CFU/mL, respectively). ATP bioluminescence results demonstrated significantly different ATP concentrations on the surfaces when soiled (PTFE: 132 relative light units (RLU), PMMA: 80 RLU and PET: 99 RLU). Following cleaning, both in the presence and absence of a blood conditioning film, all the surfaces were considered clean, producing ATP concentrations in the range of 0–2 RLU. The results generated in this study demonstrated that the presence of a blood conditioning film significantly altered the removal of bacteria from the polymeric surfaces following a standard cleaning regime. Conditioning films which represent the environment where the surface is intended to be used should be a vital part of the test regime to ensure an effective disinfection process.

Theoretical and experimental investigation on the influences of misalignment on the lubrication performances and lubrication regimes transition of water lubricated bearing

The paper investigates the influences of misalignment on the lubrication performances and lubrication regimes transition of water lubricated bearing. A modified lubrication model considering the influences of journal misalignment is proposed in the paper. Surface topography and thermal balance effects are incorporated in the theoretical model. Influences of misalignment with different surface roughness and radial clearances on lubrication performances are explored systematically. Experimental results verified the correctness of the lubrication model. Results indicate that the maximum pressure and shear stress increase, the minimum film thickness decreases and the eight dynamic coefficients increase with the misaligned angle. The region of boundary lubrication arises, the region of mixed lubrication and hydrodynamic lubrication decreases. Misaligned angle deteriorates the lubrication performances on the interface. Research results have guiding significance for further study of influences of surface topography on the structure design and optimization for such bearings.

Influence of surface modification of Ti6Al7Nb alloy on adhesion of poly (lactide-co-glycolide) coating (PLGA)

The paper presents the results of studies on the influence of surface topography and wettability of a Ti6Al7Nb alloy substrate on the adhesion of a PLGA coating. The alloy surface was modified using a mechanical pre-treatment including: grinding, vibration treatment, mechanical polishing, sandblasting and anodic oxidation. The polymer coating was applied to the metal substrate by a dip-coating method. The scope of the research included microscopic observations of the substrate and polymer coating using SEM and acoustic microscopy. In addition, studies on the wettability and topography of the polymer coating and the metal substrate, the thickness of the polymer coating as well as qualitative and quantitative testing of the adhesion of the polymer coating to the substrate were carried out. Coating adhesion tests were conducted for samples in the initial state and after 6 weeks exposure to Ringer's solution.Analysis of the results indicates the influence of the method used to modify the metal substrate on its topography and wettability. These parameters affect the thickness of the obtained polymer coating. Regardless the parameters of the metal substrate, a qualitative analysis of the adhesion of the coating applied to the substrate of the Ti6Al7Nb alloy did not show any delamination for both samples exposed and non-exposed to Ringer's solution. On the other hand, quantitative scratch-test studies showed different adhesion of the polymer coating to the substrate depending on the surface topography obtained by various modification methods.The cytotoxicity test conducted by the indirect method using extracts confirmed that the surface modification does not affect cell growth.The complex methods of surface pre-treatment of the alloy together with the kind of polymer selected for the study allowed to develop well adhered PLGA layers on Ti6Al7Nb intended for short term implants. The lack of delamination of the layer during 6 weeks was proved, what allows for maintaining the protection function of the layer during this period and contribute to improving biocompatibility.

Particle Surfaces to Study Macrophage Adherence, Migration, and Clearance

AbstractNanoparticle adsorption to substrates pose a unique challenge to understand uptake mechanisms as it involves the organization of complex cytoskeletal components by cells to perform endocytosis/phagocytosis. In particular, it is not well‐understood from a cell mechanics perspective how the adhesion of particles on substrate will influence the ease of material clearance. By using a particle model, key contributing factors underlying cell adhesion on nonporous silica particle surfaces, migration and engulfment, are simulated and studied. Following a 24 h incubation period, monocyte‐derived macrophages and A549 epithelial cells are able to adhere and remove particles in their local vicinity through induction of adhesive pulling arise from cell traction forces and phagocytic/endocytic mechanisms, in a size‐dependent manner. It is observed that such particle‐decorated surfaces can be used to address the influence of surface topography on cell behavior. Substrates which presented 480 nm silica particles are able to induce greater development and maturation of focal adhesions, which play an important role in cellular mechanoregulation. Moreover, under a chemotactic influence, in the presence of 30% fetal bovine serum, macrophages are able to uptake the particles and be directed to translocate along a concentration gradient, indicating that local mechanical effects do not substantially impair normal physiological functions.

On Waviness and Two-Sided Surface Features in Thermal Elastohydrodynamically Lubricated Line Contacts

Machine components are designed to endure increasingly severe operating conditions due to the strive for improved energy efficiency of mechanical systems. Consequently, lubricated non-conformal contacts must rely on thin lubricant films where the influence of surface topography on the lubricating conditions becomes significant. Due to the complexity of the multiphysical problem, approximate assumptions are often employed to facilitate numerical studies of elastohydrodynamically lubricated (EHL) contacts. In this work, the rough, time dependent, thermal EHL problem is solved with focus on two main analyses. The first analysis focuses on the influence of sinusoidal roughness and the difference between a thermal non-Newtonian approach and an isothermal Newtonian approach. The second analysis is focused on the lubricating mechanisms taking place when two-sided surface features overtake within the thermal EHL contact. The results indicate that the film thickness in the outlet of the contact may be significantly overestimated by an isothermal Newtonian approach and that differences in the high-pressure region may also occur due to viscosity variations in the inlet of the contact. Moreover, for the studied two-sided surface features, it became evident that not only the surface feature combination but also the overtaking position influence the film thickness and pressure variations significantly.

Mechanical properties and cell proliferation response of borided biomedical titanium alloys with different crystalline structures

A comparative study was conducted in order to investigate hardness, fracture toughness, adhesion and cell proliferation properties of boride layers produced on medical grade titanium materials with different crystalline structures. For this purpose, α type Cp-Ti, α + β type Ti-6Al-4V and β type Ti-45Nb were borided by using powder-pack boriding technique. Boride layers on titanium alloys exhibited hardness values up to 40.2 ± 2.7 GPa with low fracture toughness depending on the types of borides formed in boride layers. The adhesion tests showed that thickness, brittleness and morphology of boride layers have strong effect on adhesion of boride layers. However, no intensive failure developed on boride layers which proofs that adhesions of surface layers are sufficient. The influence of surface topography and chemical composition of boride layers on biocompatibility was examined. The proliferation of Saos-2 cells on each sample was quantified after 72 h by MTT assay. It was demonstrated that cell growth on borided Cp-Ti and Ti-6Al-4V alloy are less than their unborided ones (control). In comparison to Cp-Ti and Ti-6Al-4V alloy, Ti-45Nb alloy has increased number of cells proliferated on its both borided and unborided surfaces.

Cellular response (osteoblasts and fibroblasts) depending on the type of surface of dental implants.

Background. There are many strategies for modifying the surface of implants to create optimal conditions for the development of bone tissue. At the same time, the question of correlation of the effect of surface roughness or surface chemical composition on cell activity or osteogenesis processes remains open. Objective. The study of cellular mechanisms of osseointegration using cell cultures that occur after implantation of implants with a different type of alloy and the nature of their surface. Methods. To analyze the adhesion and cell proliferaiton, the resazurin reduction method was used, scanning electron microscopy was used to determine the distribution of cells on the sample surface and the type of cell interaction with surface. Results. Cell adhesion is observed in all studied groups, and the degree of cell adhesion is directly related to the presence of hydroxyapatite on the surface. A growing trend in the proliferation of osteoblasts is noted, while fibroblast proliferation slows down from the 3rd to the 7th day. At the same time, slow cell proliferation occurs on the surface of the implants without modification, and the percentage the reduction of resazurin does not exceed 23.5%. It should be noted that there is no difference between the types of alloys, which proves the predominance of the influence of surface topography on the proliferative activity of osteoblasts. Scanning electron microscopy on the 7th day revealed the presence of osteoblasts and fibroblasts in all studied samples. However, in the absence of hydroxyapatite, the cells are unevenly located on the surface of the sample, they are large in size and have long processes that do not have a clear orientation, and on the surface with hydroxyapatite coating there is a higher cell growth density, which predominantly has 2 processes and oriented in the same direction. Conclusion. The use of hydroxyapatite coating significantly increases the ability of cells to adhere to the surface of the implant. The presence of calcium and phosphorus mainly stimulates the proliferation of osteoblastic dipheron cells and almost does not affect the ability of fibroblasts to proliferate.

Enhanced Protein Crystallization on Nafion Membranes Modified by Low-Cost Surface Patterning Techniques

In this work, the influence of surface topography on protein crystallization over Nafion® is investigated. Two types of Nafion® based membranes were modified by soft lithographic techniques in orde...

Numerical inversion of magma chamber pressurization in volcanic areas: A case study of Changbaishan volcano

Volcanoes are commonly associated with significant topographic relief; however, most analytical models of volcanoes consider the Earth's surface as flat and use half-space solutions. Finite element method can take into account topography; we applied the equivalent body force method to the Changbaishan volcanic area to account for the influence of topographic effects on the inversion of magma chamber pressurization and to calculate the influence of the magma-induced stresses on the stability of the surrounding faults. The influence of surface topography should not be ignored when calculating the surface deformation caused by the magma chamber pressurization in a volcanic area. The shallower the burial depth, the closer the surface maximum radial displacement ur to the center of the magma chamber. When the slope reaches 30°, the maximum vertical displacement uz is no longer directly above the magma chamber. An ellipsoidal pressurization was used to satisfactorily simulate the GPS and leveling measurements at the Changbaishan volcanic area from 2002 to 2003. The superposition of the magma-induced stresses and the regional tectonic stresses likely cause the present stress directions around the Changbaishan volcano, which are dominated by the EW direction to the west of Tianchi Lake and the NW-NNW direction to the north of Tianchi Lake. The Coulomb failure stress change caused by the magma chamber is conducive to the distribution of the NW-trending earthquake swarms that mainly occur to the southwest and northeast of Changbaishan crater.

The Influence of Surface Topography on the Weak Ground Shaking in Kathmandu Valley during the 2015 Gorkha Earthquake, Nepal.

It remains elusive why there was only weak and limited ground shaking in Kathmandu valley during the 25 April 2015 Mw 7.8 Gorkha, Nepal, earthquake. Our spectral element numerical simulations show that, during this earthquake, surface topography restricted the propagation of seismic energy into the valley. The mountains diverted the incoming seismic wave mostly to the eastern and western margins of the valley. As a result, we find de-amplification of peak ground displacement in most of the valley interior. Modeling of alternative earthquake scenarios of the same magnitude occurring at different locations shows that these will affect the Kathmandu valley much more strongly, up to 2–3 times more, than the 2015 Gorkha earthquake did. This indicates that surface topography contributed to the reduced seismic shaking for this specific earthquake and lessened the earthquake impact within the valley.

Electron Beam Structuring of Ti6Al4V: New Insights on the Metal Surface Properties Influencing the Bacterial Adhesion.

Soft tissue adhesion and infection prevention are currently challenging for dental transmucosal or percutaneous orthopedic implants. It has previously been shown that aligned micro-grooves obtained by Electron Beam (EB) can drive fibroblast alignment for improved soft tissue adhesion. In this work, evidence is presented that the same technique can also be effective for a reduction of the infection risk. Grooves 10–30 µm wide and around 0.2 µm deep were obtained on Ti6Al4V by EB. EB treatment changes the crystalline structure and microstructure in a surface layer that is thicker than the groove depth. Unexpectedly, a significant bacterial reduction was observed. The surfaces were characterized by field emission scanning electron microscopy, X-ray diffraction, confocal microscopy, contact profilometry, wettability and bacterial adhesion tests. The influence of surface topography, microstructure and crystallography on bacterial adhesion was systematically investigated: it was evidenced that the bacterial reduction after EB surface treatment is not correlated with the grooves, but with the microstructure induced by the EB treatment, with a significant bacterial reduction when the surface microstructure has a high density of grain boundaries. This correlation between microstructure and bacterial adhesion was reported for the first time for Ti alloys.

Influence of surface topography on the friction and dynamic characteristics of spur gears

As an important excitation source of gear dynamic problems, the time-varying friction of tooth surface is closely related to its topography. Considering the friction characteristics of tooth surface is of great significance to improve the calculation accuracy of gear dynamic characteristics. In order to solve the problem that the variation of tooth friction coefficient was simplified too much in the previous gear dynamics research, the time-varying tooth friction coefficient is obtained by fitting the results of twin-disc test in this research. To investigate the influence of tooth surface topography on the friction and dynamic characteristics of spur gears, the relationship between surface topography and friction coefficient under line contact condition is studied using twin-disc tester and analyzed by 3D topography parameters in ISO 25178. The time-varying friction coefficients of spur gears with different tooth surface topographies during meshing are fitted with the experimental results. The influence of time-varying friction coefficient caused by the tooth surface topography on the dynamic characteristics of spur gears under different operating conditions is examined by substituting the fitting curves of time-varying friction coefficient into the multi-degree-of-freedom dynamic model of spur gears. The results show that this influence is mainly embodied in the off-line-of-action direction, which is the direction of friction force acting on the tooth surface. The dynamic characteristics of gears with different surface topography are obviously different under various working conditions. The method presents in this paper simplifies the application of tooth contact analysis in the study of time-varying tooth friction characteristics, which will provide a new way for the gear dynamics research considering the tooth surface topography.

Influence of surface topography on brightness temperature of the regions along the road

Internal temperature of the road is one of the important indicators to evaluate the safety of the road, and the microwave radiometer data is only efficient way to acquire the internal temperatures. This study is to evaluate the influence of the surface topography on the brightness temperature (TB) measured the microwave radiometer data. The results are as follows. (1) The surface slope (θ) and its direction play the important roles on the TB. (2) The influence of θ on TB is weaker compared to that of the surface temperature. (3) At least in low latitude regions, the influence of topography on the TB can be neglected in macro scale. The conclusions are essential to better understand the internal physical parameters of the road with the microwave radiometer data.

Influence of bearing raceway surface topography on the level of generated vibration as an example of operational heredity

In this paper, an influence of surface topography of ball rolling bearing raceways of the vibration values has been examined. Experiments have been preferment using series of bearing types 6304. Surface topography of bearing raceways has been measured using a stylus profilometer Talysurf PGI 1230. The 2D and 3D roughness and waviness parameters have been analyzed. The vibration measurements of ball rolling bearings have been carried out using a measuring device ―Anderonmeter‖. The concept of technological heredity and operational (exploitation) heredity in the aspect of production and operation of rolling bearings has been presented. Based on experimental study, an operation heredity analysis of ball bearings has been carried out. It has shown that the condition of surface texture of rolling bearing raceways directly affects the values of vibration generated by bearing units.

In vitro Candida albicans biofilm formation on different titanium surface topographies

Objectives To investigate if differences in titanium implant surface topography influence Candida albicans biofilm formation. Materials and Methods Titanium discs were prepared and characterized using a profilometer: Group A (R a 0.15 µm, smooth), Group B (R a 0.64 µm, minimally rough) and Group C (R a 1.3 µm, moderately rough). Contact angle and surface free energy (SFE) were determined for each group. Non-preconditioned titanium discs were incubated with C. albicans for 24 h. In additional experiments, the titanium discs were initially coated with human saliva, bovine serum albumin or phosphate-buffered saline for 2 h before incubation with C. albicans for 24 h. The amount of fungal biofilm formation was quantified using a colorimetric assay. Results C. albicans biofilm formation was significantly lower (p < 0.05) on the minimally rough titanium surface compared to smooth and moderately rough surfaces. The titanium surface displaying the lowest SFE (Group B) was associated with significantly lower (p < 0.05) C. albicans biofilm formation than the other two groups. Salivary coating resulted in greater adherence of C. albicans with increased surface roughness. Conclusions The minimally rough titanium discs displayed lowest SFE compared to smooth and moderately rough surfaces and showed the least C. albicans biofilm formation. This study demonstrated that C. albicans biofilm formation increased in a SFE-dependent manner. These findings suggest that SFE might be a more explanatory factor for C. albicans biofilm formation on titanium surfaces than roughness. The presence of a pellicle coating may negate the impact of SFE on C. albicans biofilm formation on titanium surfaces.

The Effects of Subcellular Nanograting Geometry on the Formation and Growth of Bacterial Biofilms.

Biofilm formation by bacteria protects them against environmental stresses such as desiccation, shear forces and antimicrobial agents, making them much harder to remove and increasing their virulence and persistence in industrial water systems and biomedical equipment. One promising method of disrupting biofilm formation and growth is to employ passive surface structures to inhibit bacterial adhesion and aggregation. However, most studies thus far have mainly focused on the early stages of biofilm formation and it is unclear if the influence of surface topography in the early phase will propagate to later stages. Here, we attempt to address this with an investigation into the biofilm formation of Pseudomonas aeruginosa on 25 different nanograting geometries, with dimensions that were systematically varied from subcellular to cellular sizes. The biofilms were characterized from the exponential growth phase to the decline phase, in intervals of 24 H over 4 days, using confocal scanning laser microscopy. Comparing the maximum volume of biofilm formed on each surface over 96 H, it was found that approximately 1/3 of the nanograting geometries exhibited 72 ± 16 % lower biovolume density than a flat surface. Bacteria on these nanogratings were also observed to form 40 ± 11 % smaller microcolonies that were 17 ± 6 % less compact than that found on the control surface. The majority of these nanogratings had deep trenches (i.e. depth ≥ 70% of the cell diameter). Furthermore, P. aeruginosa cells were observed to multiply at approximately twice the rate on almost all the nanogratings compared to flat surfaces, but these cell populations also began to decline 24 H earlier than those on a flat surface. Using available literature on P. aeruginosa, a qualitative model was put forth, attributing the results to increased cell motility, decreased exopolysaccharide formation and disrupted psl adhesin/signal trails on nanogratings. These factors, together, led to the net effects of reduced attachment, increased scattering of cells and rapid decline of the biofilms on nanogratings. The insights derived from this study suggest that passive surface geometries can be designed and optimized to successfully control/inhibit biofilm formation and growth.

Experimental research on the interface lubrication regimes transition of water lubricated bearing

Abstract This paper aims to experimentally investigate the influences of surface topography and operating conditions on lubrication regimes transition of water lubricated bearing in submarine. Simulations are also performed under the same settings and operating conditions. The calculated and experimental results agree well. Effects of surface roughness, external loads, radial clearances, the acceleration and deceleration process on the lubrication regimes transition are further investigated. Characteristic parameters of the lubrication regimes transition are summarized. Reasonable explanations are given to illustrate the results as well as the relative errors. It has certain guiding significance for further step investigation on influences of surface topography on lubrication regimes transition of such bearings.