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

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2960
Author(s):  
Aleksandra Rewolińska ◽  
Karolina Perz ◽  
Grzegorz Kinal
Keyword(s):  
Surface Roughness ◽  
Steel Surface ◽  
Friction Pair ◽  
Expanded Graphite ◽  
Initial Surface ◽  
Layer Formation ◽  
Material Transfer ◽  
Surface Geometry ◽  
First Case ◽  
Ring Pin

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.

Yield and shear of rough interlocked faults: analytical solution and experimental observations

2020 ◽  
Author(s):  
Amir Sagy ◽  
Vladimir Lyakhovsky ◽  
Yossef H. Hatzor
Keyword(s):  
Surface Roughness ◽  
Analytical Solution ◽  
Normal Stress ◽  
Laboratory Experiments ◽  
Three Dimensional ◽  
Elastic Half Space ◽  
Interface Roughness ◽  
Displacement Rate ◽  
Initial Surface ◽  
Surface Geometry

<p>Natural fault surfaces are interlocked, partly cohesive, and display multiscale geometric irregularities. Here we examine the nucleation of deformation and the evolution of shear in such interlocked surfaces using a closed-form analytical solution and a series of laboratory experiments.  The analytical model considers an interlocked interface with multiscale roughness between two linear elastic half-space blocks. The interface geometry is based on three-dimensional fault surfaces imaging. It is represented by a Fourier series and the plane strain solution for the elastic stress distribution is represented as a sum of the constant background stress generated by a uniform far-field loading and perturbations associated with the interface roughness. The model predicts the critical stress necessary for failure and the location of failure nucleation sites across the surface, as function of the initial surface geometry.</p><p>A similar configuration is adopted in laboratory experiments as carbonate blocks with rough interlocked surfaces generated by tensional fracturing are sheared in a servo-controlled direct shear apparatus. Resistance to shear and surface roughness evolution are measured under variable normal stresses, slip distances and slip rates.  We find that the evolution of surface morphology with shear is closely related to the loading configuration. Initially rough, interlocked, surfaces become rougher when normal stress and displacement rate are increased. Under a fixed, relatively low normal stress and fixed displacement rate however, the surfaces become smoother with increasing displacement distance.  </p><p>The shear of the interlocked slip surfaces is associated with volumetric deformation, wear and frictional slip, all of which are typically observed across natural fault zones. We suggest that their intensities and partitioning are strongly affected by the initial surface roughness characteristics, the background stress, and the rate and magnitude of shear displacement. </p>

On the Prediction of Transient Wear

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Vahid Mortazavi ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Steady State ◽  
Wear Rate ◽  
Linear Relationship ◽  
Coefficient Of Friction ◽  
Friction Pair ◽  
Wear Loss ◽  
Initial Surface ◽  
Pi Theorem ◽  
Tribological Parameters

During the running-in process, a friction pair experiences drastic evolution in many of its tribological parameters, such as surface roughness, wear rate, and coefficient of friction until steady-state is attained. In this paper, we present a model for predicting the behavior of the running-in process. Specifically, we determine a general relationship between the wear loss and surface roughness during the running-in stage and test the validity of its prediction of wear rate by comparing to available experimental results. We show, by using a dimensional analysis and applying the Buckingham Pi theorem, that there exists a linear relationship between the transient dimensionless wear, the dimensionless initial surface roughness, and dimensionless running-in time.

Nonlinear instability of liquid jets with thermocapillarity

1995 ◽  
Vol 283 ◽  
pp. 97-123 ◽  
Author(s):  
F. Mashayek ◽  
N. Ashgriz
Keyword(s):  
Ambient Temperature ◽  
Liquid Jets ◽  
Stable Configuration ◽  
Initial Surface ◽  
Breakup Mechanism ◽  
Capillary Flows ◽  
First Case ◽  
Satellite Drops ◽  
Thermal Disturbance ◽  
Surface Disturbance

The breakup mechanism of a capillary jet with thermocapillarity is investigated. Effects of the heat transfer from the liquid to the surrounding ambient, the liquid thermal conductivity, and the temperature-dependent surface tension coefficient on the jet instability and the formation of satellite drops are considered. Two different disturbances are imposed on the jet. In the first case, the jet is exposed to a spatially periodic ambient temperature. In addition to the thermal boundary condition, an initial surface disturbance with the same wavenumber as the thermal disturbance is also imposed on the jet. Both in-phase and out-of-phase thermal disturbances with respect to surface disturbances are considered. For the in-phase thermal disturbances, a parameter set is obtained at which capillary and thermocapillary effects can cancel each other and the jet attains a stable configuration. No such parameter set can be obtained when the thermocapillary flows are in the same direction as the capillary flows, as in the out-of-phase thermal disturbances. In the second case, only an initial thermal disturbance is imposed on the surface of the liquid while the ambient temperature is kept spatially and temporally uniform.

scholarly journals The behaviour of composites, glass ionomers and compomers in erosive conditions – in vitro study

2014 ◽  
Vol 60 (5) ◽  
pp. 200-203
Author(s):  
Andreea Borş ◽  
Cristina Molnar-Varlam ◽  
Melinda Székely
Keyword(s):  
Surface Roughness ◽  
Wear Resistance ◽  
Erosive Wear ◽  
In Vitro Study ◽  
Vitro Study ◽  
Initial Surface ◽  
Dental Filling ◽  
Filling Materials ◽  
Restorative Materials

Abstract Objective: The aim of this in vitro study was to evaluate the influence of erosive conditions on the wear resistance of aesthetic direct restorative materials. Methods: Six dental filling materials were tested: two composites (Filtek Z550 and X-tra fil), two compomers (Dyract Extra and Twinky Star) and two glass ionomers (Ketac Molar and Fuji II LC). Twenty disks (10mm×2mm) of each material were prepared (n=120) and kept in artificial saliva at 37˚C for 24 hours. Specimens were cycled in acidic soft drink (Coca-Cola) 5×/day, for 5’, over 30 days. Initial surface roughness ISR (Ra-μm) and final surface roughness FSR were measured using a profilometer. The wear rate was calculated as difference of final minus the initial roughness (ΔSR=FSR-ISR). For statistical analysis t-test and one-way ANOVA test were used by GraphPad Prism version 5.03 statistical software. The level of significance was set at p<0.05. Results: The erosive wear rates (mean±SD, μm) after exposure to acidic beverage were: 0.30±0.03 (Ketac Molar), 0.28±0.04 (Fuji II LC), 0.27±0.00 (Filtek Z550), 0.23±0.01 (X-tra fil), 0.20±0.00 (Twinky Star) and 0.14±0.01 Dyract Extra, respectively. There were significant differences between the tested materials (p<0.05). Conclusions: Dental filling materials had different behaviour under the same erosive condition, however all investigated aesthetic restorative materials showed surface degradation. These findings suggest that erosive wear resistance of tooth coloured restoratives could influence their longevity in intraoral acidic conditions. Acknowledgements: The study was supported by the Internal Research Grant no. 5/30.01.2013 of the University of Medicine and Pharmacy of Tirgu Mureş.

Dynamic transmission of oil film in soft-start process of HVD considering surface roughness

2018 ◽  
Vol 70 (3) ◽  
pp. 463-473 ◽  
Author(s):  
Fangwei Xie ◽  
Jie Zhu ◽  
Jianzhong Cui ◽  
Xudong Zheng ◽  
Xinjian Guo ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Friction Pair ◽  
Maximum Temperature ◽  
Force Model ◽  
Content Type ◽  
Oil Film ◽  
Soft Start ◽  
Viscous Torque ◽  
Start Process

Purpose The purpose of this paper is to study the dynamic transmission of the oil film in soft start process of hydro-viscous drive (HVD) between the friction pairs with consideration of surface roughness, and obtain the distribution law of temperature, velocity, pressure, shear stress and viscous torque of the oil film. Design/methodology/approach The revised soft-start models of HVD were derived and calculated, including average Reynolds equation, asperity contact model, load force model and total torque model. Meanwhile, a 2D model of the oil film between friction pair was built and solved numerically using computational fluid dynamics (CFD) technique in FLUENT. Findings The results show that the maximum temperature gradually reduces from the intermediate range (z = 0.5 h) to the inner side of the friction pair along the direction of oil film thickness. As the soft-start process continues, pressure gradient along the direction of the oil film thickness gradually changes to zero. In addition, tangential velocity increases and yet radial velocity decreases with the increase of the radius. Originality/value In this paper, it was found that the viscous torque calculated by the numerical method is smaller than that by the CFD model, but their overall trend is almost the same. This also demonstrates the effectiveness of the numerical simulation.

Nanofinishing of Microslots on Surgical Stainless Steel by Abrasive Flow Finishing Process: Experimentation and Modeling

2018 ◽  
Vol 6 (2) ◽  
Author(s):  
Sachin Singh ◽  
Deepu Kumar ◽  
Mamilla Ravi Sankar ◽  
Kamlakar Rajurkar
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Critical Role ◽  
Viscoelastic Model ◽  
Three Dimensional ◽  
Drug Eluting Stent ◽  
Initial Surface ◽  
Technological Advancement ◽  
Drug Eluting ◽  
Abrasive Flow Finishing

Miniaturization of components is one of the major demands of the today's technological advancement. Microslots are one of the widely used microfeature found in various industries such as automobile, aerospace, fuel cells and medical. Surface roughness of the microslots plays critical role in high precision applications such as medical field (e.g., drug eluting stent and microfilters). In this paper, abrasive flow finishing (AFF) process is used for finishing of the microslots (width 450 μm) on surgical stainless steel workpiece that are fabricated by electrical discharge micromachining (EDμM). AFF medium is developed in-house and used for performing microslots finishing experiments. Developed medium not only helps in the removal of hard recast layer from the workpiece surfaces but also provides nano surface roughness. Parametric study of microslots finishing by AFF process is carried out with the help of central composite rotatable design (CCRD) method. The initial surface roughness on the microslots wall is in the range of 3.50 ± 0.10 μm. After AFF, the surface roughness is reduced to 192 nm with a 94.56% improvement in the surface roughness. To understand physics of the AFF process, three-dimensional (3D) finite element (FE) viscoelastic model of the AFF process is developed. Later, a surface roughness simulation model is also proposed to predict the final surface roughness after the AFF process. Simulated results are in good agreement with the experimental results.

Effect of Initial Surface Roughness on Water Erosion Resistance of Last Stage Blade Substrate of Steam Turbine

2020 ◽  
Author(s):  
Fang Li ◽  
Shunsen Wang ◽  
Juan Di ◽  
Zhenping Feng
Keyword(s):  
Numerical Simulation ◽  
Surface Roughness ◽  
Steam Turbine ◽  
Water Droplet ◽  
Erosion Resistance ◽  
Water Erosion ◽  
Experimental Results ◽  
Initial Surface ◽  
Maximum Water ◽  
Last Stage

Abstract In order to study the effect of initial surface roughness on water droplet erosion resistance of last stage blade substrate of steam turbine, eight 17-4PH samples were grounded and velvet polished by different mesh metallographic sandpaper to establish sample with different initial surface roughness. The water droplet erosion experiments were carried out in the highspeed jet water erosion experiment system, and the mass and micro-morphology of each sample were measured by using precision electronic balance and ultra-depth of field microscope respectively at each experimental stage, and the measurement of water erosion trace width and maximum water erosion depth were also completed at the same time. On the basis of experiments, LS-DYNA was used for numerical simulation to verify the reliability of experimental results again. Results show that the smoother the initial surface of sample, then the smaller the mass loss, the stronger its water erosion resistance. On the contrary, the rougher the initial surface of sample, the more severe the surface irregularity, the more times the water droplets concentrated at the lowest point of pit when water droplets flow laterally after impact is completed, thus accelerating the formation of initial crack and lateral expansion, the poorer the water erosion resistance of sample. At same water erosion time, the smoother the sample surface, the later the complete erosion trace appear, the narrower the water erosion trace width. However, the maximum water erosion depth of sample is not affected by the initial surface roughness. The numerical simulation results are in good agreement with the experimental results.

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