Sliding Velocity Research Articles

Wear behaviour analysis on aluminium alloy 7050 with reinforced SiC through taguchi approach

Aluminium alloy is the popular material in the world to produce lot of light weight parts with high strength, in additionally reinforcement is consider to these alloy is improve its strength. In this investigation consider the AA7050 aluminium alloy as a base material with reinforcement of Silicon Carbide (SiC) at various percentage level like as 0%, 4 % and 6 %. The wear of this composites are analysed through the design of experiments (Taguchi approach) for optimize the process parameters. This wear study is considered the parameters are Sliding velocity in m/s (1, 2 and 3), Sliding distance in m (1000, 1400 and 1800) and percentage of composition (0%, 43% and 6%). For this experimental investigation the sliding distance as most significant factor among three. The microstructure analysis demonstrated that there is a SiC particles which reduces wear of the samples.

Control of Sliding Velocity in Robotic Object Pivoting Based on Tactile Sensing

Abstract Control of robots manipulating objects using only the sense of touch is a challenge. In-hand motion of the manipulated object highly depends on the friction forces acting at the contact surfaces. Soft contacts allow torsional frictions as well as friction forces, therefore robots can perform more complex manipulation abilities, like object pivoting. Control of the pivoting sliding motion is very difficult especially without any visual feedback. The paper proposes a novel method to control the sliding velocity of the object by using a simple parallel gripper endowed with force/tactile sensors only. The strategy is based on a nonlinear observer that estimates the sliding velocity from force/torque measurements and a model of the sliding dynamics.

Simultaneous optimization of slide velocity and back-pressure in forging

Simultaneous optimization of slide velocity and back-pressure in forging

Effect of Sliding Velocity and Normal Applied Load on Wear Behavior of Al-Ti- Sic Composites for Automobile Brake Pad System Under Dry Sliding Condition

The wear and coefficient of friction (COF) behaviour of aluminium titanium (Al-Ti) alloys with varying of silicon carbide (SiC) are used as reinforcement material in the present research work. Automobile brake pads were developed by stir casting technique with 15, 20 and 25wt.% of SiC in Al-Ti alloys, respectively, instead of the traditional CI (cast iron) brake drum used for a chase machine. The normal applied load and sliding velocity varied to simulate vehicle running condition. It has been observed from the results the wear and COF for silicon carbide MMC is effectively than the CI material. The wear is varied with both sliding velocity and normal applied load. The experimental results reveals that the low wear was observed at 25wt.% of SiC than 15 and 20 wt.% of SiC. With increase of normal applied load, the wear was observed to increase whereas the COF decreases.

Effect of TiB2/Gr Hybrid Reinforcements in Al 7075 Matrix on Sliding Wear Behavior Analyzed by Response Surface Methodology

Al 7075 alloy matrix reinforced with different weight percentage of titanium borides (TiB2, 0, 1.5, 3, 4.5 and 6 wt%) and 1 wt% graphite (Gr) hybrid composites were synthesized by in-situ liquid metallurgy route, then the sliding wear characteristics were performed and investigated in this research work. TiB2 reinforced as 0, 1.5, 3, 4.5 and 6 wt% by the in situ chemical reaction of KBF4 and K2TiF6 salts and 1 wt% Gr with the Al 7075 matrix were added constantly in the melt. Several experiments were carried out to examine the wear behavior of the fabricated composite specimens through a tribometer at ambient temperature. The weight percentage of reinforcement (TiB2 particles), the applied load, the sliding velocity (SV), and the sliding distance (SD) were selected as process parameters at five different levels. The response surface methodology (RSM) was used to conduct the experiments as RSM is the feasible and accurate method employed for optimizing to set the parameters. To check the significance of the developed model by RSM, ANOVA and confirmatory tests were also accomplished. FESEM surface morphology was also carried out to illustrate the uniform dispersion of the TiB2–Gr particulates in Al 7075 matrix. The predicted wear characteristics from the developed model were well agreed with the experimental results. The obtained results were explained that both the increase in the percentage of RF and SV have dropped the wear loss (WL) curve whereas the load at all SVs and the SDs were uplifted the WL. The worn surface morphology explained that the adhesive mechanisms were dominated during the sliding wear test. Further, severe and mild wear occurred during higher load and lower load respectively.

Tribological and wear performance of centrifuge cast functional graded copper based composite at dry sliding conditions

Non lubricated slide performance of functional grade copper matrix composite, fabricated using horizontal centrifuge cast technique was investigated using pin-on-disc tribo-tester. Rate of wear and friction coefficient of the inner wall thickness of hollow cylindrical cast specimen was analyzed using Taguchi based L27 orthogonal array, where the percentage of graphite particles were observed higher. Variable process parameters those influenced the rate of wear directly or indirectly were: applied load (15, 25 and 35 N), slide velocity (1.5, 2.5 and 3.5 m/s) and slide distance (750, 1500 and 2250 m). Rate of wear and friction coefficient showed a proportional dependency with applied load and slide distance, whereas showing a decline during intermediate slide velocity. Signal-to-Noise ratio predicted the minimal tribo-condition, on ‘smaller-the-better’ basis. Analysis of Variance technique quantified the influence of affecting parameters, along with their interactions. Regression analysis was utilized for the validation of the experimental data. Micrographs and scanning electron microscopy exhibited the wear mechanisms and mechanically mixed layer formation during worn surfaces analysis.

Friction in Cold Ice Within Outer Solar System Satellites With Reference to Thermal Weakening at High Sliding Velocities

AbstractThe icy shells of Enceladus and Europa consist from top down of cold (~100 K) ice at low (<0.1 MPa) pressure, cold ice at high pressure up to ~10 MPa, and warm ice near 273 K the base. The pressure ~10 MPa and temperature near 273 K of basal ice within Enceladus and Europa are similar to that within terrestrial glaciers that are known to have seismicity (icequakes). Warm ice easily melts during sliding so its icequakes are qualitatively explained and expected on these satellites if the macroscopic strain rates are comparable to those within terrestrial glaciers subjected to oceanic tides. However, cold ice at high pressures does not readily macroscopically melt during sliding. A dynamic weakening mechanism for crustal faults in rock may be applicable to Enceladus and Europa. Micron‐scale real contacts support ~0.4‐GPa shear tractions and normal tractions on rapidly sliding ice faults. At sliding velocities above ~0.1 m/s, the asperity tips of the contacts become hot and weak in ice. The macroscopic friction depends on the average strength of the asperity tips during the lifetimes of contact. The strength of the asperity tips self‐organizes so that frictional heating balances the heat lost from the asperity tip by conduction. The macroscopic coefficient of friction at coseismic sliding velocities decreases to a modest fraction of the low‐velocity coefficient of friction, but does not approach zero. This velocity‐weakening mechanism likely allows major icequakes within the cold interiors of Europa and Enceladus.

Mechanical Characteristics of High-Entropy Alloys and Their Constituent Metals in Friction Conditions at Low Sliding Velocities

The mechanical characteristics of high-entropy alloys and their constituent metals were examined by dry friction against diamond at low sliding velocities in air. The friction tests were performed at a velocity of 16 mm/sec and a diamond load of 2.2 N. With increasing friction coefficient, the wear rate of the metals and alloys tends to become higher. The linear wear ranges from 1.06 · 10–7 for chromium to 12.76 · 10–7 for aluminum. In addition, the linear wear of multicomponent alloys is lower than that of their constituent metals and ranges from 0.35 · 10–7 to 4.38 · 10–7. The linear wear of high-entropy alloys is a half to a quarter of the linear wear of individual metals because they differ in hardness, the friction coefficients being equal.

Characterization of centrifuge cast TiC reinforced functional grade composite of copper

This research analyses physical and anti-wear properties of a functional grade Cu–Ni–Si/TiC, manufactured using horizontal- centrifuge cast process. The microstructural analysis conducted radially at wall thicknesses 1, 8 and 13 mm from outer, showed an increasing gradient of particle distribution providing 41% improved hardness at the inner p eriphery and NiSi2 phase formation was determined by XRD analysis. Outer (1–8 mm) and inner (9–15 mm) wall thicknesses of composite was tested against tensile load; later fractural analysis showed ductility for the outer and brittleness for inner. Resistance to wear of inner was experimented using pin-on-disc tribometer. Variable parameters were fixed according to Taguchi’s L27 array. Optimal tribo-parameters (10 N, 2 m s−1, 500 m) for minimum rate of wear were determined using ratio of Signal to Noise. Contribution of each influential parameter and their interactions are predicted using Analysis of Variance. Results depict that slide velocity had the highest influence (45.56%) over rate of wear, followed by applied load (21.82%) and slide distance (14.63%). Wear analysis on tested specimen revealed Mechanical Mixed Layers; later confirmed by EDX.

Influence of Flyash & Silicon Nitride on Mechanical & Tribological Properties of Aa 7075 Hybrid Composite

The main objective of this research work is to study the effect of Silicon Nitride (Si3N4) and Flyash on the mechanical and tribological properties of AA 7075 hybrid composite. The Stir casting technique has been used for the fabrication of composite material. sAA 7075 were reinforced with 2 wt. % of Silicon Nitride and 2.5, 5, 7.5 wt. % of Flyash. Pin-on-disc equipment is used to evaluate the wear rate of the base alloy and hybrid composite. Dry sliding wear test were performed with the contact load which is varied by 10, 20 & 30 N. Sliding velocity is varied by 1, 1.5 and 2 m/s. Sliding distance is kept constant at 1000 m. The Scanning Electron Microscope (SEM), Energy Dispersive X Ray Spectroscopy (EDAX) and X-ray diffraction (XRD) were used for the characterization of the composites. The maximum hardness of 173 HV is achieved for 5 wt% Flyash and 2 wt% of Silicon Nitride addition. The percentage increase in hardness is 155 % above the base metal. AA 7075 with the 5 wt % reinforcement of Flyash shows the minimum wear rate. With respect to the base the wear rate is reduced by 59 %.

Comparative study between tribological performance of carbide reinforced functionally graded copper composite and its alloy under the influence of process parameters

The functionally graded composite Cu-10Sn-5Ni/10 wt% B4C and its alloy, was manufactured (Φout100 × Φin85 × 100 mm) by stir casting route utilizing horizontal centrifuge cast technique. A comparative dry sliding tribological analysis was performed for interior (1–5 mm), intermediate (5–10 mm) and exterior (10–14 mm) zones of both composite and alloy, using pin-on-disc tribometer. A direct relation for rate of wear and friction coefficient (COF) was seen with variably hiking applied load and slide distances. Whereas for varied slide velocity, COF raised with a reduced slope along a directly related rate of wear. Worn surface analysis of the interior composite zone exhibited delamination and grooves, pointing the severing of wear which was normal. Functional grade composite mixed with B4C suggests its applicability in production of cylinder liners, automobile bearings, slide concave guide bars and electric switches.

Mechanical and tribological analysis of functionally graded aluminium hybrid composite using RSM approach

Functionally graded LM14 Al/12Si3N4/3Gr hybrid composite was developed through horizontal centrifugal casting with a wall thickness of 15 mm. Mechanical analysis like Vickers hardness (27%) and tensile strength (3%) were observed superior at Si3N4 rich outer zone than Gr rich inner zone. Rate of wear of Gr rich inner specimen (8–13 mm from outer) increases linearly with increase in applied load (10–50 N), non-linearly with slide distance (500–3000 m) and a slight decrease and a further increase in trend with slide velocity (1–4.5 m s−1) when studied based on Response Surface Methodology (RSM) five level run order, using pin on disc tribometer. Minimum rate of wear (0.0052 mm3 m−1) was observed at an optimum parametric influence of load, velocity and slide distance (10 N, 1 m s−1, 500 m). Worn composite surfaces were analyzed using Scanning Electron Microscope to understand the tribo-mechanisms, which led to deep groove formations and delamination at higher loads and shallow grooves at lower loads, along the sliding direction. Fabricated composite proves the ability to replace the conventional materials for automotive sliding applications like piston liners, which provides improved wear characteristics during dry sliding conditions.

Simulation of energy transfers in waves generated by granular slides

This paper presents a multi-fluid Navier-Stokes modeling of the waves generated by two granular slides (subaerial and submarine) which were previously studied experimentally and a pure synthetic submarine case used for results interpretation. In the numerical model, air and water are considered Newtonian fluids. The slide is modeled as a Newtonian fluid whose viscosity is adjusted to fit the experimental results. Once the viscosity is adjusted, the first and the second waves are shown to be accurately reproduced by the model even though the computed slide is slower. For the subaerial case, the viscosity value found is shown to be consistent with the granular μ(I) rheological law. The second part of this work focuses on the energy transfers between a slide and its generated waves. Energy balance is computed in each phase. The wave energy is evaluated in the wave propagation zone. Energy dissipation, kinematic and potential energies are taken into account in the computation of energy transfer ratio allowing for a better understanding of the phenomena. In light of these results, the wave train generation process is discussed as well as the importance of the slide dynamics in the wave generation stage. The amount of energy transferred to wave is not constant with time and the transfer rate depends strongly on the definition of this rate as well as the case considered. For instance, in the subaerial case simulated, the energy transferred to surface waves is 30% of the energy transferred to water at the time the transfer stops, but this conversion rate is only equal to 4% of the overall available potential slide energy at the end of the process. For the two submarine cases simulated, the corresponding values, equal in both cases, are 2% and 1%, respectively. The simulation results also show that the slide energy is transferred to the water in a short period of time at the beginning whatever the case considered. This observation may be related to the initial nil slide velocity (subaerial case) and the relatively large slope values considered (both cases). Nevertheless, the results illustrate the importance of accurate simulation of the slide dynamics within the wave generation process.

Design and Development of Surface Texture for Tribological Application

Surface texturing is a process of fabricating specific patterns on a surface to enhance surface properties such as friction, contact area, air aspiration, wear, hydrophobicity, etc. Fabricating surfaces with planned micro features is an effective method to improve tribological performance of the interacting surfaces. Laser surface texturing process is one of the best suitable processes for producing micro-patterns. Micro textures are imparted on HSS discs using CO2 laser, varying the shape and dimensions of the resulting dimples affecting the frictional coefficient and wear. Experiments have been accomplished to determine effects of textural variations such as areal density of dimples, dimple shape, area of dimples and depth of dimples on the Coefficient of Friction (COF) and Wear. Effects of lubrication conditions (Dry and Wet), pin material (MS, SS, EN31), applied load (25N, 50N, 75N) and Sliding velocity (400 rpm, 800 rpm and 1200 rpm) are evaluated on COF and Wear. Tests have been performed on pin-on-disk apparatus along guidelines of Taguchi L18 Orthogonal Array, keeping constant sliding distance of 940 m (about 10,000 cycles). Experimentally, it is found that wet lubricated, circular shaped dimples, with areal density 7.5%, dimple area 0.09 mm2 with MS material pin provides best results. This experimental analysis has been performed to test the applicability, efficiency and reliability of the textured surfaces.

Synthesis of Aluminium Composites Using Squeeze Casting and Investigating the Effect of Reinforcements on Their Mechanical and Wear Properties

The research aims to fabricate LM25 alloy and composites reinforced with 15 wt% TiB2, 15 wt% ZrO2 and 15 wt% WC using squeeze casting technique. The fabricated cylindrical castings were of dimensions 50 mm diameter and 150 mm length. Microstructural analysis revealed better distribution of reinforcement particles for each composite, which provided better hardness and tensile properties. Physical and wear properties were studied comparatively to understand the influence of reinforcements, and tungsten carbide (WC)-reinforced composites showed better performance. Fractographic analysis revealed ductile mode of failure for LM25 and a combination of ductile and brittle mode for its composites. Dry sliding performance of both alloy and composites was analysed under different sliding conditions of applied load (10–50 N), slide distance (500–2500 m) and slide velocity (1–5 m/s) using pin-on-disc tribometer. WC-reinforced composite improved resistance to wear by 70% compared to alloy. Wear analysis of composite using scanning electron microscope showed change in wear features from mild to severe at high loads. The developed LM25/WC composite was found to be most suitable for non-lubricated slide applications.

Dry Sliding Wear Behavior and Mechanism of a Hot-Dip Aluminized Steel as a Function of Sliding Velocity

Fe-Al intermetallic coatings were prepared on AISI 1045 steel by hot-dip aluminizing and subsequent high-temperature diffusion. The dry sliding wear tests were performed for the aluminized steel with various substrate hardnesses in the velocity range of 0.75-4 m/s on a pin-on-disk configuration. The dry sliding wear behavior and mechanisms of the aluminized steel under various velocities were explored. It was found that the wear rate decreased substantially with an increase in sliding velocity from 0.75 to 1.5 and then slightly varied in the velocity range of 1.5-4 m/s. The wear behavior and mechanisms of the aluminized steel were noticed to be closely related with tribo-layers. As tribo-layers contained more oxides with Fe2O3, the wear resistance of the aluminized steel was markedly improved because of their protective function. The substrate hardness also changed the wear behavior of the aluminized steel by affecting the stability of tribo-layers because the substrate hardness was inversely proportional to the thermal stability of the substrate structure. Under a low velocity of 0.75 m/s, adhesive wear and abrasive wear prevailed owing to the metal-on-metal contact, resulting in a higher wear rate. At 1.5-4 m/s, mild oxidative wear prevailed due to the stable existence of tribo-oxides layers. However, at 1.5 and 4 m/s for the substrate hardness of 45 HRC, the wear rate was slightly increased because the protection of tribo-layers was weakened by a double-layered structure or more cracks in tribo-layers and coatings.

Thermal Weakening of Asperity Tips on Fault Planes at High Sliding Velocities

AbstractReal contacts on the scale of ~10 μm support gigapascal shear tractions and normal tractions on rapidly sliding faults. At sliding velocities above ~0.1 m/s, the asperity tips of the contacts become hot and weak. The macroscopic friction depends on the average strength of the asperity tips during their lifetimes of contact. The strength of the asperity tips does not go essentially to zero once they become weak because frictional heating would then cease and the tips would cool and strengthen. Rather, the contact retains finite strength so that frictional heating balances the heat lost from the asperity tip by conduction. Crudely, the macroscopic coefficient of friction at high sliding velocities decreases with the inverse of the square root of velocity rather than the inverse of the velocity in the widely used model of Rice (2006, https://doi.org/10.1029/2005/JB004006). Numerical thermal‐mechanical models support this inference. The finite strength of the asperity tips retards lateral extrusion of weakened material from the tips. Otherwise, extrusion would allow the sliding surfaces to converge establishing new contacts, which would renew the strength of the surface. The macroscopic coefficient of friction with somewhat weakened asperity tips remains high enough that the fault surface becomes hot on a millimeter scale in large crustal earthquakes. Fluid pressurization and eventually millimeter‐scale melting then reduce the macroscopic shear traction to lower values than does asperity tip weakening acting alone.

Simultaneous optimization of variable slide velocity and variable back-pressure profile in precision forging

Simultaneous optimization of variable slide velocity and variable back-pressure profile in precision forging

Multi-objective optimization of slide velocity and back-pressure for improving product quality and productivity in forging

Multi-objective optimization of slide velocity and back-pressure for improving product quality and productivity in forging

Perspectives of the Friction Mechanism of Hydrogenated Diamond-Like Carbon Film in Air by Varying Sliding Velocity

The purpose of the present work is to probe the friction mechanism of hydrogenated diamond-like carbon (H-DLC) film in air by varying sliding velocity (25–1000 mm/s). Friction tests of Al2O3 ball against H-DLC film were conducted with a rotational ball-on-disk tribometer. As the sliding velocity increases, both the friction coefficient and the surface wear of H-DLC film decrease, reach the minimum values, and then increase in the high sliding velocity region. Based on the observed results, three main friction mechanisms of H-DLC film—namely graphitization mechanism, transfer layer mechanism, and passivation mechanism—are discussed. Raman analysis indicates that the graphitization of worn surface on the H-DLC film has a negligible contribution to the variation of the friction coefficient and the surface wear. The origin of the sliding velocity dependence is due to the synergistic interaction between the graphitized transfer layer formation and the surface passivation. The present study will not only enrich the understanding of friction mechanism of H-DLC films in air, but will also help to promote their practical engineering applications.