Evolution Of Surface Roughness Research Articles

Cu thin film growth on stepped Si substrate: Effects of incident energy and thermal annealing

The existence of defects on the substrate surface is unavoidable and has a significant impact on the determination of surface properties. Among the prevalent types of defects, steps play an important role. In this study, molecular dynamics simulations are employed to explore the growth process of a thin film of Cu on a Si (001) substrate with a step. This research investigates how incident energy and thermal annealing affect the growth mode, surface roughness, film-substrate interface, and dislocation evolution. The results indicate that during the initial stage of the growth, the nucleation phenomenon was observed on terraces. The simulation indicates that the Cu atoms occur in an island growth mode on the stepped substrate. It is found that when the incident energy is increased and thermal annealing is performed, the surface curvature and roughness are reduced. Furthermore, the intermixing thickness at the interface increases due to the variation of the incidence energy. A dislocation analysis revealed that some dislocations disappeared before and after annealing, and a perfect dislocation appeared by increasing the incident energy.

Surface roughness evolution law in full-aperture chemical mechanical polishing

Ultra-high precision revolution surfaces are crucial to mechanical components like bearings but are difficult to achieve using conventional machining. Meanwhile, it is challenging to predict the surface roughness evolution law during processing. Accordingly, this study proposed an ultra-precision full-aperture chemical mechanical polishing (CMP) method for processing revolution surfaces. More importantly, a theoretical surface roughness Ra model was established by assuming that the three-dimensional surface morphology can be simplified to two-dimensional identical triangles, each peak can be uniformly removed, and the material removal at the valleys can be neglected compared to that at the peaks. The model provides an intuitive understanding of the Ra evolution law during the full-aperture CMP. Interestingly, Ra first decreases parabolically, determined by the initial surface roughness Ra0, the material volume removal rate MRRV, and the polishing time t. Then, it stabilizes. In addition, the theoretical MRRV model was summarized. The cylindrical guiding surface of a bearing was polished with the developed full-aperture CMP method. In 6 min, Ra can be significantly reduced from the initial 201.09 nm to 1.50 nm almost parabolically and stabilizes. Experimental results basically validate the theoretical Ra model, except that a slow decreasing stage appears intermediately because the real surface cannot be perfectly uniform. Additionally, the roundness error RONt is reduced by 34%. Furthermore, the full-aperture CMP method and Ra model are successfully applied to other revolution surfaces. This study provides mechanistic insight into Ra evolution modelling pertaining to the manufacturing process.

Evolution of Surface Roughness of Wrought and Additively Manufactured Inconel 718 During Centrifugal Disc Finishing

Evolution of Surface Roughness of Wrought and Additively Manufactured Inconel 718 During Centrifugal Disc Finishing

On the unusual R-ratio dependence of the high cycle fatigue performance of precipitate strengthened Al alloys

The high cycle fatigue (HCF) performance of precipitate strengthened Al alloys is important for their use in moving structures applications such as transportation. It was first shown in the 1950′s, and has been confirmed multiple times since, that sometimes the weaker underaged alloys can show longer high cycle fatigue lives under R = -1 loading than the stronger peak aged materials. However, under alternative R-ratio loadings (e.g. R = 0.1), the underaged alloys tend to show the same, or even worse, HCF performance as the peak aged alloys. This unusual R-ratio dependence is studied in this work using a combination of fatigue testing on smooth samples, optical profilometry of the evolution of surface roughness during cycling, and transmission electron microscopy.We demonstrate that the unusual R-ratio effect is really an effect of the maximum applied stress, and the critical role that this has in determining the strain localization that occurs during the first cycle of loading. This initial strain localization sets the path for subsequent plasticity accumulation which eventually leads to fatigue failure. The maximum applied stress plays a stronger role in determining the initial strain localization than either the applied stress amplitude or R-ratio and this is the critical factor determining the fatigue life of the precipitate strengthened Al alloys considered in this study.

Surface roughness evolution and heterogeneous plastic deformation of austenitic stainless steel during micro deep drawing: Modeling and experiment

The present work involves the numerical simulation and experimental study on the surface roughness evolution and heterogeneous plastic deformation (strain localization and concomitant surface morphology evolution) in grain scale of micro deep drawn parts of austenitic stainless steel (ASS) 304 foils. A three-dimensional modeling framework was used to simulate the micro deep drawing (MDD) process. The simulation involved the development of a Voronoi-based polycrystalline geometry model (VPGM), a multi-stress-strain response model, and a crystal plasticity finite element methods (CPFEM) model. The results indicate that CPFEM model exhibits higher accuracy in the localized stress and strain, thickness distribution fluctuation and surface roughness evolution of the fabricated parts compared to multi-stress-strain response model. Therefore, the plastic deformation heterogeneity in MDD is in-depth discussed based on CPFEM model. The results show that the coarse-grained foils correspond to the intense strain localization, which is the main cause of surface roughening. Considering the average grain size is close to the thickness of ASS foils, mounding features on the rough surface may readily develop further into potentially fractured sites during deformation. On the other hand, crystal orientation influence plastic deformation by affecting the slip behavior of materials. The effect of crystal orientations including {011} 〈211〉 (Brass), {011} 〈100〉 (Goss), and {112} 〈110〉 components on deformation is discussed. The results indicate a strong correlation between the magnitude of the Schmid's factor and the ease of deformation. Additionally, variations in Schmid's factor across different directions result in differences in deformation accumulation, which affects the thickness distribution along the radial direction and the distribution of earrings and wrinkles along the circumferential direction of the fabricated micro parts.

A frequency-domain simulation method for the evolution of rail corrugation in curves

Rail corrugation remains a major problem in many railways and metros, leading to high noise and vibration levels as well as potential damage to the track and vehicle. A frequency domain simulation method is proposed for the evolution of the rail surface roughness, which can simulate the formation and development of rail corrugation in curves. A coupled vehicle-track dynamic model is established in the frequency domain to calculate the dynamic vertical and lateral wheel-rail contact forces and the associated vibration. The wheel-rail contact state is determined by using a multi-body dynamics model. The frictional-work wear model is used to calculate the roughness change caused by wheel-rail dynamic interaction. The method is verified by comparing the results with those of on-site testing on a 300 m radius curve of a metro line. It is shown that the main causes of rail corrugation are associated with the peaks in the vertical wheel-rail forces in the frequency domain, generated by the interaction between the wheel and rail. At short wavelengths the corrugation is associated with the wave reflections in the rail between adjacent axles. The phase relationship between the vertical wheel-rail force and the initial roughness has a strong influence on the roughness growth trend, leading to preferential growth in certain wavelength bands. The wheel-rail contact state and friction parameters affect the rate of development of the corrugation. Finally, a corrugation index is proposed to allow quick evaluation of the wavelength and growth rate of corrugation.

Evolution of the mixed mode FPZ and fracture roughness of Beishan granite after coupled thermo-hydro-mechanical treatment

Deep surrounding rocks contain a network of longitudinally intersecting fissures. Exploration of their fracture process zone (FPZ) size evolution during mixed loading and fracture surface roughness after failure has always been a hot topic, especially for coupled thermo–hydro–mechanical (THM) treatment. This study takes Beishan granite as the research object. The fracture surface roughness and FPZ length were obtained using Grasselli statistical and mixed strain–displacement methods. Finally, an electron microscope was employed to observe the fracture surface after failure at different temperatures and loading angles. Results reveal a notable temperature and load dependence of the fracture surface roughness and FPZ length evolution. In the low-temperature stage (25°C–300°C), the mineral primarily exhibited transgranular fractures and the average fracture surface roughness showed a slightly decrease with increasing temperature. In the high-temperature stage (500℃–650℃), the degree of internal damage to the prepared specimens substantially increased, with intergranular fractures being the dominant fracture mode, and rapid roughness growth occurred. Under the same temperature condition, the roughness value was in the order of mode I > mixed mode > mode II. The FPZ length increased, stabilized, and decreased as the load increased. In the low-temperature stage, the FPZ length reached its maximum value at the maximum load, whereas in the high-temperature stage, the FPZ length was fully developed before the peak load. Under the same loading angle condition, the FPZ lengths corresponding to the three loading modes followed the order of mode I < mixed mode < mode II.

Ultra-Smooth Polishing of Single-Crystal Silicon Carbide by Pulsed-Ion-Beam Sputtering of Quantum-Dot Sacrificial Layers.

Single-crystal silicon carbide has excellent electrical, mechanical, and chemical properties. However, due to its high hardness material properties, achieving high-precision manufacturing of single-crystal silicon carbide with an ultra-smooth surface is difficult. In this work, quantum dots were introduced as a sacrificial layer in polishing for pulsed-ion-beam sputtering of single-crystal SiC. The surface of single-crystal silicon carbide with a quantum-dot sacrificial layer was sputtered using a pulsed-ion beam and compared with the surface of single-crystal silicon carbide sputtered directly. The surface roughness evolution of single-crystal silicon carbide etched using a pulsed ion beam was studied, and the mechanism of sacrificial layer sputtering was analyzed theoretically. The results show that direct sputtering of single-crystal silicon carbide will deteriorate the surface quality. On the contrary, the surface roughness of single-crystal silicon carbide with a quantum-dot sacrificial layer added using pulsed-ion-beam sputtering was effectively suppressed, the surface shape accuracy of the Ø120 mm sample was converged to 7.63 nm RMS, and the roughness was reduced to 0.21 nm RMS. Therefore, the single-crystal silicon carbide with the quantum-dot sacrificial layer added via pulsed-ion-beam sputtering can effectively reduce the micro-morphology roughness phenomenon caused by ion-beam sputtering, and it is expected to realize the manufacture of a high-precision ultra-smooth surface of single-crystal silicon carbide.

Effect of Electrochemical Surface Oxidation on Intrinsic Activity Towards the Hydrogen Evolution Reaction of Ultra-Smooth Nanocrystalline Ni Thin Films

Green hydrogen has emerged as a leading contender in the pursuit of a sustainable energy transition, driving the need for optimized catalysts in hydrogen production. Therefore, considerable effort is taken to replace the highly active, yet expensive Pt-group metals with non-noble alternatives such as Ni. Understanding the hydrogen evolution reaction (HER) mechanism on well-performing Ni surfaces is essential for gaining fundamental knowledge and implementing this in practical applications. While high surface area structures are typically designed for enhanced efficiency, there is limited research available on the fundamental aspects of thin films and smooth surfaces, which are crucial for benchmarking intrinsic catalytic activity and elucidating catalytic mechanisms. To address this gap, we perform a combined microstructural and electrochemical evaluation of smooth Ni thin film electrodes to analyze HER in alkaline media.This study aimed to evaluate the intrinsic catalytic properties of nanocrystalline Ni thin films and the effect of electrochemical oxidation on the catalytic behavior, while precisely monitoring the evolution of the film surface state and roughness. In addition to experimental work, Density Functional Theory (DFT) calculations and Kinetic Monte Carlo (KMC) simulations are used to understand HER on oxide-modified Ni surfaces and the role of different elementary processes involved in the HER mechanism.Nanocrystalline low-roughness Ni electrodes for HER were produced via magnetron sputter deposition to minimize the difference between geometrical and electrochemical surface area. This means we find intrinsic material properties directly, bypassing the need for additional measurements for real surface area determination. The analysis of catalyst activities towards HER as well as the oxidation process [1] was performed via cyclic voltammetry, using a three-electrode setup. Within the conducted studies, we can report a significant lowering of the overpotential for HER upon in-situ oxidation of the electrodes due to the existence of NiO, and Ni(OH)2 on the Ni catalyst surface [2], leading also to a limitation of the deactivation processes. Further analysis including topography evaluation (AFM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) in combination with selected area diffraction (SAED) of the as-deposited and oxidized electrodes confirmed that the observed effect can be assigned to the availability of oxides on the surface assuredly (Figure 1). Additionally, theoretical calculations and simulations (DFT, KMC) support the experimental data and derived theories.In conclusion, the beneficial effect of NiO and Ni(OH)2 presence on Ni surfaces was examined and successfully proven by a combination of electrochemical measurements, material characterization, theoretical calculations, and a careful experimental design that minimizes the influence of interfering factors, such as surface roughness.

Controlled Growth of WO3 Photoanode under Various pH Conditions for Efficient Photoelectrochemical Performance.

Herein, the effects of the precursor solution's acidity level on the crystal structure, morphology, nucleation, and growth of WO3·nH2O and WO3 nanostructures are reported. Structural investigations on WO3·nH2O using X-ray diffraction and Fourier-transform infrared spectroscopy confirm that the quantity of hydrate groups increases due to the interaction between H+ and water molecules with increasing HCl volume. Surface analysis results support our claim that the evolution of grain size, surface roughness, and growth direction on WO3·nH2O and WO3 nanostructures rely on the precursor solution's pH value. Consequently, the photocurrent density of a WO3 photoanode using a HCl-5 mL sample achieves the best results with 0.9 mA/cm2 at 1.23 V vs. a reversible hydrogen electrode (RHE). We suggest that the improved photocurrent density of the HCl-5 mL sample is due to the efficient light absorption from the densely grown WO3 nanoplates on a substrate and that its excellent charge transport kinetics originate from the large surface area, low charge transfer resistance, and fast ion diffusion through the photoanode/electrolyte interface.

The influence of laser beam shaping on surface roughness, surface figure and mid-spatial frequency of fused silica glass in CO2 laser smoothing

CO2 laser with Gaussian and top-hat laser intensity distribution, were utilized to process fused silica with 50 mm diameter in raster scanning path to explore the evolution of surface roughness, waviness and surface figure. The results show that surface roughness can be decreased to < 10 nm with both Gaussian and top-hat CO2 laser smoothing; Top-hat laser will cause higher PSD2 value compared with Gaussian, but Gaussian has led to added mid-spatial frequency at 0.4395 mm−1 (2.28 mm) with 75 % overlap rate (raster scanning distance is 2.327 mm); The surface profile of fused silica has evolved from the initial convex to concave profile after being irradiated by both CO2 lasers. From experiments, improper overlap rate will cause greater distortion, and higher power density can result in serious damage to the PV value of surface figure.

Morphology, phase composition, surface roughness evolution and growth mechanism of hot-dip aluminum coating on Mo substrate

The Al-rich hot-dip aluminum composite coatings were synthesized on Mo surface by hot-dip aluminizing under different deposition processes. The aluminide coatings present a very smooth dense coating structure with a lower surface roughness and fine grain size, the average surface roughness (RSa) values are only 0.118–0.869 μm, and the corresponding surface area growth rate (Sdr) values are 3.85–80.19 %. Increasing the deposition temperature is beneficial for the transition of low melting point compounds of the coating surface to high melting point compounds, and extending the hot dip time is profit for the diffusion and enrichment of Al atoms on the coating surface. Besides, increasing the deposition temperature or time can also promote the growth of Al4Mo grains, thereby significantly increasing the coating thickness. When the deposition temperature is 750 °C, the thicknesses of Al4Mo and Al8Mo3 layers increases in a parabolic law with deposition time, and the Kp values both of them are 3.46 × 10−13 m2/s and 1.47 × 10−15 m2/s, respectively. The growth of the coating depends on the continuous diffusion of Al atoms towards the substrate direction, and the difference in chemical potential between Al atoms in each phase is the main driving force for coating growth.

Using Electropulsing to Control the Surface Quality of Casts

This paper reports on the mechanisms and provides worked examples of using pulsed electric current to improve the surface properties of conductive materials during solidification. A rough surface is formed via the freezing of thermomechanical fluctuations and external disturbances during solidification. Pulsed electric current provides an extra driving force for the fluctuations to relax in a shorter duration toward the equilibrium state before the material loses the fluidity during cooling. This additional mechanism is associated with the electric current free energy, which depends on the current density distribution at various materials geometries, including the surface profile. The mechanism has been validated by experimental characterization of the surface roughness evolution with and without electropulsing treatment.

Effects of cyclic fatigue loads on surface topography evolution and hydro-mechanical properties in natural and artificial fracture

This work investigated permeability evolution for fluid flow through natural fractures and artificial fractures in granite and the evolution of failure surface under cyclic fatigue loads condition. We revealed and compared a clear distinction between two types of fracture surfaces before and after the test, and analyzed the evolution of fracture surface roughness and other parameters which can characterize their topography feature, as well as the relationship between fracture surface topography and permeability. The studies indicated that artificial fractures show the higher roughness and subtler variations of surface topography than those of natural fractures, however, the surface topography of natural fractures was more susceptible to cyclic fatigue loads. The initial permeability and average permeability of nature fractures were both higher than those of artificial fractures during the stress-seepage coupling test and the permeability of artificially fracture was more sensitive to normal stress changes. Moreover, the experimental results were in line with theoretical predictions and the research results can provide reference for preventing the failure of rock engineering.

Evolution of surface roughness of notched steel details under fatigue loading

A fatigue crack initiates on the surface of the steel members, which can be attributed to the extrusions and intrusions caused by cyclic loading. The surface roughness parameters, including the statistical surface roughness and maximum surface roughness parameters, can characterize the increase in extrusion and intrusion. Six notched specimens were loaded with cyclic loading, and the evolution of the surface roughness parameters was monitored during the test to explore the characteristics of the surface roughness during the fatigue loading procedure in the high-cycle fatigue regime and clarify the effects of the initial surface finish and load ratio on the surface roughness evolution. Based on the test results, it was found that the 3D average surface roughness Sa and 3D root-mean-square surface roughness Sq were preferable for detecting the onset of fatigue cracks compared with the 2D average surface roughness Ra and 2D root-mean-square surface roughness Rq. The 3D maximum valley depth, Sv, was an effective indicator of the fatigue crack initiation location, except for compression-dominant fatigue loading. The evolution patterns of the 3D average surface roughness, Sa, and 3D root-mean-square surface roughness Sq during fatigue loading can be classified into three phases: instant response, damage accumulation, and crack-induced response. In addition, surface polishing is recommended for evaluation using 2D surface roughness parameters. However, it is not mandatory for evaluations using 3D surface roughness parameters. The effects of typical load ratios (0.1, −1, and 10) on the evolution pattern of the 3D statistical surface roughness parameters, especially in the instant response phase, were also investigated.

Rolling contact fatigue failure mechanism of bearing steel on different surface roughness levels under heavy load

It is inherent knowledge that rolling contact fatigue (RCF) failure of subsurface-initiated spalls usually occur under optimum surface under heavy load. However, our previous work has revealed surface-initiated RCF failure mechanism under heavy load and initial high roughness surface. The formation of surface crack caused by RCF is a complicated phenomenon that is accompanied by surface morphology and lubrication condition, as well as stress distribution and microstructure evolution. To clarify the main failure mechanism, this study carried out systematic RCF tests with different surface roughness specimens and conducted characterization of superficial microstructure for specimens of pre-service and post-service by Focused Ion Beam (FIB). The results clearly suggest precursor of collapsed morphology and nanocrystalline layer are the main factor that causes the RCF life with high roughness is lower than that with low roughness. While the spalling failure initiating from low roughness surface under heavy load are strongly relied on surface plastic deformation. Two main plastic deformation mechanisms are conductive to formation of surface cracks: the micro-plastic deformation and the local severe plastic flow. A newly failure mechanism that spalling failure initiates from surface has been proposed to link surface roughness and microstructure evolution.

Prediction of surface roughness based on fused features and ISSA-DBN in milling of die steel P20

The roughness of the part surface is one of the most crucial standards for evaluating machining quality due to its relationship with service performance. For a preferable comprehension of the evolution of surface roughness, this study proposes a novel surface roughness prediction model on the basis of the unity of fuse d signal features and deep learning architecture. The force and vibration signals produced in the milling of P20 die steel are collected, and time and frequency domain feature from the acquired signals are extracted by variational modal decomposition. The GA-MI algorithm is taken to select the signal features that are relevant to the surface roughness of the workpiece. The optimal feature subset is analyzed and used as the input of the prediction model. DBN is adopted to estimate the surface roughness and the model parameters are optimized by ISSA. (Reviewer 1, Q1) The separate force, vibration and fusion signal information are brought into the DBN model and the ISSA-DBN model for the prediction of surface roughness, and the results show that the accuracy of the roughness prediction is as follows, respectively DBN: 78.1%, 68.8% and 84.4%, and ISSA-DBN: 93.8%, 87.5% and 100%.

Optimization and Mathematical Modelling of Surface Roughness Criteria and Material Removal Rate when Milling C45 Steel using RSM and Desirability Approach

This work consists of studying the workability of C45 steel in face milling by using coated carbides (GC4040). The objective is to investigate the evolution of surface roughness (Ra, Ry, and Rz) and Material Removal Rate (MRR) according to cutting speed, feed rate, and depth of cut. A full-factorial design (43)was adopted in order to analyse the obtained experimental results via bothAnalysis of Variance (ANOVA) and Response Surface Methodology (RSM)design. The levels of cutting speed were as follows: Vc1=57 m/min; Vc2=111m/min; Vc3=222 m/min and Vc4=440 m/min. The ranges of feed rate werefz1=0.024 mm/tooth; fz2=0.048 mm/tooth; fz3=0.096 mm/tooth and fz4=0.192mm/tooth. As for the depth of cut levels, they included ap1=0.2 mm; ap2=0.4mm; ap3=0.6 mm, and ap4=0.8 mm. To determine mathematical models tomake predictions, a statistical analysis of the results by using RSM was appliedto obtain the main effects and interactions plot of the answer. Furthermore, amulti-objective optimization procedure for minimizing Ra and maximizing themetal removed rate using the desirability approach was also implemented.Therefore, the developed models can be effectively used to predict the surfaceroughness criteria and the material removal rate in machining C45 steel. Theresults indicated that feed rate is a significant factor affecting surfaceroughness (Ra: 52.37%, Ry: 80.97%, and Rz: 54.96%), followed by cuttingspeed (Ra: 37.88%, Ry: 12.90%, and Rz: 24.43%). Meanwhile, cutting speedand feed rate are the most significant parameters on the MRR with a contribution of 29.5% followed by the depth of cut with 11.62%.

Evolution of particle morphology of quartz sand during one-dimensional compression

Particle breakage alters particle size, shape, surface roughness, and co-ordination number, which in turn changes macro-mechanical behaviour including compressibility and shear strength. This study conducted a series of one-dimensional (1D) compression tests on quartz sands with different initial void ratios, ending the tests at various stress levels up to 13.5 MPa. The size and shape of particles were quantified using a dynamic particle shape analyser, while the surface roughness of thirty randomly selected particles for each sample was measured by an optical interferometer and quantified using flattened root-mean-square roughness (RMSf). The results demonstrate that a unique normal compression line is defined due to extensive particle breakage, with denser sample exhibiting a higher yield stress. Prior to yielding (vertical stress < 6 MPa), the changes in the three shape descriptors are limited, as the primary particle damage modes are abrasion and grinding. Conversely, at high stress level, a greater number of particles undergo splitting or explosive damage, leading to the creation of more irregularly shaped particles. The occurrence of plastic deformation at particle asperities under one-dimensional compression is identified, resulting in a decrease in surface roughness. This study highlights the significant role of the initial void ratio in shaping the evolution of surface roughness of particles under 1D compression.

Mass finishing of additively manufactured Ti6Al4V parts: An investigation of surface finish dependency on build orientation and processing conditions

Poor surface finish of as-built metal Additive Manufacturing (AM) remains a key challenge in fabricated parts. Metal AM parts typically require postprocessing to improve surface finish before application. Furthermore, different surface orientations and scanning strategies in Powder-Bed-Fusion (PBF) metal AM are prone to result in non-uniform surface roughness across different surfaces of a part. In recent years, Mass Finishing (MF) technologies, such as Centrifugal Disc Finishing (CDF), are gaining popularity in improving AM surfaces due to its fixture-free, batch-processing, and relatively low costs. There is a critical need to study the surface finish dependency on AM build orientation and MF processing conditions. In this study, Ti6Al4V ASTM-E8b tensile bars were fabricated in 45⁰ and 90⁰ orientation via Laser Powder Bed Fusion (L-PBF) to investigate the effects of CDF processing conditions on upward facing surface (up-skin), downward facing surface (down-skin), and side facing surface (side-skin). The surface roughness evolution on each type of surface were collected via laser scanning profilometry. It was found that both processing speed and processing time of CDF were statistically significant factors in improving AM surface roughness, however, processing time had higher impact. Furthermore, different build orientation demonstrated different surface roughness reduction rate and material removal rate. It was found that side-skin had the highest average roughness reduction, and the down-skin exhibited the least roughness reduction. In addition, this study found that the surface with the highest initial surface roughness (down-skin) had the least material removal rate, and that the highest material removal rate was observed in surface with higher periodicity (side-skin). Findings from this study will help the AM community in decision-making of CDF conditions to prevent over-finishing and under-finishing. In addition, the investigation of surface evolution dependency on AM build orientation can further improve the understanding of key mechanisms of AM + MF hybrid manufacturing system.