Effect Of Initial Surface Roughness Research Articles

Effects of Initial Surface Roughness and Sliding Speed Study on the Tribological Characteristics of AA6061 and CuZn37Pb2 Alloys

Effects of Initial Surface Roughness and Sliding Speed Study on the Tribological Characteristics of AA6061 and CuZn37Pb2 Alloys

Effect of initial surface roughness on the cyclic oxidation behavior of an austenitic stainless steel

Effect of initial surface roughness on the cyclic oxidation behavior of an austenitic stainless steel

Effect of Steel Surface Roughness and Expanded Graphite Condition on Sliding Layer Formation.

The aim of the research was to evaluate the influence of the initial roughness of a steel pin cooperating with a graphite ring—dry and wet—on the mechanism of sliding layer formation. A ring–pin friction pair was used for the study, where the rings were made of expanded graphite, while the pins were made of acid-resistant steel. In the first case, the steel pin interacted with a dry graphite ring, and in the second case, the graphite rings were moist. To determine the effect of initial surface roughness, the pins were divided into three roughness groups. To determine changes in surface geometry due to material transfer, the Ra and Rz parameters were measured. This project investigated how the initial roughness value of the steel surface pin cooperating with expanded graphite influences the formation of the sliding layer. Increasing the initial roughness of the steel surface interacting with the graphite contributes to faster layer formation and reduced roughness. The state of the expanded graphite—dry and wet—influences the formation of the sliding layer of graphite—a wet graphite component causes a faster smoothing of the steel surface. The running time of the wear apparatus has an effect on the resulting layer. The highest roughness group is the most favorable from the viewpoint of sliding layer formation.

Effect of initial surface roughness on the actual intensity of laser shock processing

We prepared samples with different surface roughnesses, which were subjected to laser shock treatment using the same laser parameters. We then investigated the effect of initial surface roughness on the actual intensity of laser shock. The results show that, after laser shock treatment, the lower the initial surface roughness of the target, the higher the degree of plastic deformation of the material. A smoother target surface allowed laser-induced shock waves to introduce a higher residual compressive stress on the material’s surface. The proposed reason for the above phenomenon is the change in the absorption per unit area of the laser energy by materials of different surface states. Thus, these results provide a different method for improving the actual impact intensity of laser shock. In fact, laser shock can be a highly feasible and economical method to achieve a more obvious laser shock strengthening effect by reducing the initial surface roughness of the target surface.

On the Role of Material Transfer in Friction Between Metals: Initial Phenomena and Effects of Roughness and Boundary Lubrication in Sliding Between Aluminium and Tool Steels

In the absence of a lubricant, the friction we measure in sliding contact between metals is typically high and quite erratic, with rapid fluctuations. If we filter out these rapid fluctuations, we can typically also notice slower trends, which can lead to quite dramatic friction changes. Unless careful studies are performed, the cause to this behaviour cannot be understood. How come a material couple cannot be characterised with a specific coefficient of friction? The present paper sets out to add understanding to this area, by conduction and analysing an experimental series involving sliding between a needle-like aluminium tip against tool steel flats. The load is high enough to cause substantial plastic deformation of the aluminium needle; its tip becomes formed by the contact against the tool steel. These small-scale, low sliding distance tests facilitate detailed studies of the initial stages of various friction trends, and the effects of initial surface roughness and shifts of this roughness caused by material transfer between the sliding surfaces. Specifically, the effects on the transfer and friction behaviour from presence or absence of a boundary lubricant film and atmospheric oxygen were studied. It was found that very smooth sliding surfaces can offer low-friction conditions for these metal types. However, the smooth sliding interface is very fragile. In all unlubricated cases tested, it very rapidly (in less than a few mm sliding) became ruined due to transfer, and the friction level correspondingly increased. The boundary lubricant could only offer low friction in cases where the flat steel surface was very smooth. The lubricant also facilitated smoothening of transferred aluminium. As long has been well known, boundary lubrication films typically do not totally hinder direct metallic contact in solid to solid contact. The present results strengthen this view and further suggests that in these direct contacts one of the major friction reducing effects of the lubricant is to efficiently limit transfer, which otherwise acts to make the sliding surface rough.

Effect of Initial Surface Roughness on Cavitation Erosion Resistance of Arc-Sprayed Fe-Based Amorphous/Nanocrystalline Coatings

The arc spraying process was used to prepare Fe-based amorphous/nanocrystalline coating. The cavitation erosion behaviors of FeNiCrBSiNbW coatings with different surface roughness levels were investigated in distilled water. The results showed that FeNiCrBSiNbW coating adhered well to the substrate, and was compact with porosity of less than 2%. With increasing initial surface roughness, the coatings showed an increase in mass loss of cavitation erosion damage. The amount of pre-existing defects on the initial surface of the coatings was found to be a significant factor for the difference in the cavitation erosion behavior. The cavitation erosion damage for the coatings was a brittle erosion mode. The evolution of the cavitation erosion mechanism of the coatings with the increase of the initial surface roughness was micro-cracks, pits, detachment of fragments, craters, cracks, pullout of the un-melted particle, and massive exfoliations.

Quantitative analysis of surface roughness evolution in FCC polycrystalline metal during uniaxial tension

The purpose of this work is to present a quantitative description of surface roughness evolution in face-centered cubic (FCC) polycrystalline metal under uniaxial tension. The crystal plasticity model, in which the crystal plasticity constitutive law and the periodic boundary condition are incorporated, is established to analyze the effect of initial surface roughness, grain size and crystallographic orientation distribution on the surface roughness evolution. It is found that the surface topography during plastic straining can be divided into heterogeneous deformation surface and homogeneous deformation surface according to whether considering the heterogeneity of polycrystalline material or not. To quantitatively descript the surface roughness evolution during uniaxial tension, the concepts of equivalent grain size, which represents the comprehensive effect of grain sizes in different directions, and standard deviation of the direction cosines between crystal plane and rolling direction of grains (SD_cHR), which represents the effect of orientation distribution, are proposed. The roughness of the model with flat free surface depends approximately linearly on both the tension strain and the grain size, and exponential on the texture distribution. The uniaxial tensile test is performed to verify the accuracy of the established quantitative description of surface roughness evolution, which shows a favorable agreement with the predicted results.

The effect of initial surface roughness on water droplet erosion behaviour

Water droplet erosion (WDE) is defined as the progressive loss of original material from a solid surface due to continuous impingements of water droplets or jets. Several factors are known to influence the WDE process, such as impact speed and water droplet size. The initial surface roughness was not given enough attention in the literature as a factor that may influence the WDE behaviour of materials. In this work the effect of initial surface roughness on the WDE of a special martensitic stainless steel (12%Cr-steel) and Ti6Al4V is investigated. Experiments were done by varying three parameters: initial surface roughness, test speed, droplet size. It was concluded that the initial surface quality influences the length of the incubation stage, and may influence the maximum erosion rate. The amount of asperities and irregularities on the surface of samples was found to be the main reason for the difference in the WDE erosion behaviour. Moreover, the importance of reporting the initial surface of tested samples was emphasised, especially when comparisons between the WDE resistance of different substrate materials and/or treatments are held.

Effect of Initial Surface Roughness on the Force of Diamond Smoothing

Effect of Initial Surface Roughness on the Force of Diamond Smoothing

Optimization of Micro Cross Wedge Rolling and Surface Morphology of Micro Stepped Components

A novel microforming process - Micro Cross Wedge Rolling (MCWR) has been developed, which is promising for fabricating micro stepped components used in micro electro-mechanical systems. Numerical simulations have been established and the effect of geometrical and process parameters such as forming angle α, stretching angle β and reduction ΔA have been studied. Micro stepped components have been fabricated successfully on a MCWR testing rig by adopting flat wedge tools. The effects of initial surface roughness of tool, grain size and cross section area reduction on surface morphology have been assessed quantitatively.

Femtosecond laser-induced ripple structures on magnesium

Two types of periodic surface structures including micro-ripples and nano-ripples were observed on magnesium after femtosecond laser irradiation, and the color effect was reported by scanning a single laser beam over a large area at near damage threshold fluence. Optical reflectance measurement revealed that the color effect was mainly attributed to the nano-ripples as diffraction gratings, and intensity of the color was affected by morphology of the micro-ripples. AFM and SEM images showed that orientation of the micro-ripples was parallel to laser polarization and the period of the micro-ripples increased with scanning numbers, while the orientation of the nano-ripples was perpendicular to laser polarization and the period of the nano-ripples kept constant as laser sub-wavelength with increasing scanning numbers. These results suggested that formation of the micro-ripples was due to the combined effect of initial surface roughness and near-field interference, while formation of the nano-ripples was caused by the near-field interference between incident light and surface plasmons being excited in the air and metal interface. The potential application of such an effect is further proposed.

Swift heavy ion induced topography changes of Tin oxide thin films

Monodisperse tin oxide nanocrystalline thin films are grown on silicon substrates by electron beam evaporation method followed by 100MeV silver ion bombardment with varying ion fluence from 5×1011 ionscm−2 to 1×1013 ionscm−2 at constant ion flux. Enhancement of crystallinity of thin films with fluence is observed from glancing angle X-ray diffraction studies. Morphological studies by atomic force microscopy reveal the changes in grain size from 25nm to 44nm with variation in ion fluence. The effect of initial surface roughness and adatom mobility on topography is reported. In this work correlation between ion beam induced defect concentration with topography and grain size distribution is emphasized.

Femtosecond Laser-Induced Surface Patterning on 4H-SiC

Femtosecond laser-induced periodic structures, so-called ripples, were systematically studied under various incident laser wavelengths and polarization properties. The effect of the excitation wavelength on the period of ripples was investigated from the infrared to ultraviolet laser pulses. The period of ripple on 4H-SiC correlated remarkably with the wavelength of the incident laser beam. This means that the period of ripples can be controlled by the wavelength of the laser beam. The irradiation of circular polarized femtosecond laser beam produced dot-like structures with the mean spacing of about 200 nm on the surface of 4H-SiC. The effect of initial surface roughness was also studied.

Effect of surface roughness on the properties of the layer formed on AISI 304 stainless steel after plasma nitriding

Experiments were performed with an aim of studying an effect of initial surface roughness with different gas compositions in plasma nitriding, using pulse D.C. glow discharge plasma in presence of nitrogen and hydrogen gas mixtures. Samples were prepared with different mechanical treatments: polishing, rough polishing, machining and grinding. Plasma nitriding was carried out on AISI 304 stainless steel at 560 °C under 4-mbar pressures for 24 h in presence of N 2 : H 2 in 20 : 80 and 80 : 20 ratios. After plasma nitriding, surface roughness, micro hardness, case depth and phase formation were evaluated by using stylus profilometer, Vickers micro hardness tester, optical microscope and X-ray diffraction techniques, respectively. After plasma nitriding, hardness and case depth variation are observed with variation in surface roughness as well as gas compositions. Maximum hardness i.e. 1325 HV and case depth i.e. 110 μm are achieved on mirror polished samples at 80N 2 : 20H 2. The diffraction patterns show the most dominant phase formation of CrN, Fe 4N and Fe 3N which is responsible for this increase.

Runoff and sediment losses from rough and smooth soil surfaces in a laboratory experiment

Soil surface roughness may significantly impact runoff and erosion under rainfall. A common perception is that runoff and erosion are decreased as a function of roughness because of surface ponding and increased hydraulic roughness that reduces effective flow shear stress. The objective of this study was to measure the effects of initial surface roughness on runoff and erosion under controlled laboratory conditions. Initially, rough and smooth surfaces were exposed to five simulated rainfall applications at 5% and 20% slopes. In all cases, runoff was delayed for the case of the initially rough surface; however, this effect was temporary. Overall, no statistical differences in either total runoff or erosion were measured on the 20% slope. At 5% slope, runoff was less on the rough surface for the first rainfall application but greater on the final three, probably due to the formation of a depositional seal in that case. This resulted in an overall insignificant difference in runoff for the sum of the five rainfall applications. Erosion was greater on the rougher slope at 5% steepness, probably due to concentration of flow as it moved around the roughness elements on the rougher slope. These results indicate that commonly held perceptions of the impact of soil surface roughness on runoff and erosion may not be entirely correct in all cases.

Load-carrying capacity of surface-hardened gears. Influence of surface roughness on surface durability.

The influences of material, heat treatment, tooth profile and surface roughness on the surface durability of surface-hardened gears were investigated. First, the effect of surface roughness on rolling/sliding contact fatigue was studied in detail by using a 2-roller-type contact fatigue testing machine. The results show that the initial surface roughness has a remarkable influence on the surface durability of surface-hardened steels, and that the decrease in surface roughness with running time does not always have an advantageous effect. Secondly, the load-carrying capacities of case-carburized gears and induction -hardened gears were investigated by using a power circulating-type gear testing machine. The phenomenon of grey-staining, which consists of many micro-cracks and micro-pits, appears on the ground tooth surface under a heavy load. In these tests, it is clear that the surface failure grey-staining, which causes degradation of the tooth profile and spalling, is most influenced by the initial tooth surface roughness. Furthermore, the effect of initial surface roughness on the surface durability of surface-hardened gears can be estimated quantitatively.

Load-carrying capacity of surface-hardened gears (Influence of surface roughness on surface durability)

The influence of material, heat treatment, tooth profile and surface roughness on the surface durability of surface-hardened gears was investigated. First, the effect of surface roughness on rolling/sliding contact fatigue was studied in detail using a 2-roller-type fatigue testing machine. From these results, it is found that the initial surface roughness has a considerable influence on the surface durability of surface-hardened steel, and that the decrease of surface roughness with running does not always have an advantageous effect. Secondly, the load-carrying capacities of case-carburized gears and induction-hardened gears were investigated using a power circulating-type gear testing machine. The phenomenon of grey-staining, which consists of many micro-cracks and -pits, occurs on the ground tooth surface under a heavy load. In these tests, it is found that the grey-staining failure, which causes the degradation of tooth profile and the spalling, is most influenced by the initial tooth surface roughness. Furthermore, the effect of initial surface roughness on the surface durability of surface-hardened gears can be grasped quantitatively.

Rolling contact fatigue properties of Tuffritrided 0.2% C steel

The effects of initial surface roughness and lubricant viscosity on the rolling contact fatigue behaviour of a Tufftrided plain 0.2% C steel are reported. The Tufftriding treatment substantially improves the rolling contact performance. Improvement in the surface finish before Tufftriding is beneficial. Changes in lubricant bulk viscosity have no significant effect on the fatigue properties.

Failure Mechanisms in High-Density Polyethylene Rollers

This paper describes failure processes in plastic rollers that undergo rolling contact, and the effect of initial surface roughness upon wear and rolling fatigue. Experiments were performed with mating cylindrical rollers of high-density polyethylene (PE rollers) and chrome-plated cylindrical driving rollers. Surface roughness of the PE roller is affected by three successive transition processes. In the first period, the amount of wear can hardly be measured, although a reduction of surface roughness is noted. During the second period, wear occurs in proportion to the initial surface roughness. In the third period, wear becomes independent of the initial surface roughness, and increases in a manner exponential to load. At the end of this period, small cracks appear randomly, and grow into pits. Roller fatigue Life, defined by the time when cracks appear, is shown by an S-N curve. It is found that fatigue limiting stress, represented by Hertz stresses, is about 107pa.