Friction Coefficient Test Research Articles

Development of a Ultrasonic System for Nano-Surface Reformation Process

In this article, a 20 kHz Titanium (Ti) ultrasonic waveguide system for a nano-surface reformation process was designed and fabricated. First, finite element analysis using ANSYS software was performed to find the optimal dimensions. The obtained anti-resonance frequency for the Ti transducer with the piezoelectric device was 20.0 kHz, which value agreed well with the experiment result of 20.1 kHz (0.5% error). To test the system, chromium molybdenum steel (SCM) 435 was chosen as a test-piece. The result proved that the reformed depth was 36 μm. In addition, hardness was measured before and after the process. The value was changed from 14 HRC to 21 HRC, which is 50% increasing rate. Finally, the friction coefficient test result showed that the surface coefficient was reduced from 0.14 to 0.10 (28.6% reduction). Based on the results, the Ti ultrasonic equipment is regarded as a useful device for nano-scale surface reformation.

Development of Standardized Material Testing Protocols for Prosthetic Liners.

A set of protocols was created to characterize prosthetic liners across six clinically relevant material properties. Properties included compressive elasticity, shear elasticity, tensile elasticity, volumetric elasticity, coefficient of friction (CoF), and thermal conductivity. Eighteen prosthetic liners representing the diverse range of commercial products were evaluated to create test procedures that maximized repeatability, minimized error, and provided clinically meaningful results. Shear and tensile elasticity test designs were augmented with finite element analysis (FEA) to optimize specimen geometries. Results showed that because of the wide range of available liner products, the compressive elasticity and tensile elasticity tests required two test maxima; samples were tested until they met either a strain-based or a stress-based maximum, whichever was reached first. The shear and tensile elasticity tests required that no cyclic conditioning be conducted because of limited endurance of the mounting adhesive with some liner materials. The coefficient of friction test was based on dynamic coefficient of friction, as it proved to be a more reliable measurement than static coefficient of friction. The volumetric elasticity test required that air be released beneath samples in the test chamber before testing. The thermal conductivity test best reflected the clinical environment when thermal grease was omitted and when liner samples were placed under pressure consistent with load bearing conditions. The developed procedures provide a standardized approach for evaluating liner products in the prosthetics industry. Test results can be used to improve clinical selection of liners for individual patients and guide development of new liner products.

Experimental study and isolation mechanism analysis on emulsion wax curing agent used on cement-stabilized granular base

Abstract Based on the analysis in the mechanism of emulsion wax curing agent (EWCA) which was regarded as bond-breaking layer of concrete pavement, tests for shear stress, penetration test, pendulum friction coefficient test and sliding friction coefficient test are operated. Indexes for tests are measured after the spraying of EWCA on cement-stabilized granular base (CSGB). Compared with base do not have bond-breaking layer, test results indicated that bond stress, friction coefficients and permeability coefficients had been separately reduced by 64, 62 and 9 % with the help of EWCA. As a result it will improve the impermeability of CSGB. Pendulum friction coefficient test and sliding friction coefficient test are conducted, on cement-stabilized base’s surface with different texture depth 3 days after the spraying of EWCA. According to variation of sliding friction coefficient and British Pendulum Number (BPN), it can be concluded that they will decrease as increasing of spraying dosage and tend to stable finally. Field interlayer tangential bond force test with EWCA being sprayed on lean concrete base (texture depth <0.3) is performed. The results indicates: spraying time has significant effect on jacking force; wearing after form the film and rainfall have less effect on jacking force. The experimental results indicate that longer the time interval (from spraying the EWCA to pouring the pavement), the worse the effect of isolation. As a conclusion of engineering, the construction of isolation layer should be finished a few days before the construction of pavement.

The effects of humidity on the surface modification of wool fabric through atmospheric pressure plasma jet

Current research was carried out on hydrophilic wool fibers at three different humidity conditions through atmospheric pressure plasma jet (APPJ). Samples were taken to evaluate surface microscopic morphology, surface roughness, directional friction effect (DFE), and surface chemical composition. The scanning electron microscope (SEM) and fiber friction coefficient test (FFT) results show that wetting pretreatment has significant effect on surface etching and DFE, but very limited effect on surface roughness. Allworden reaction and X-ray photoelectron spectroscopy (XPS) results reveal that extra moisture changes C, O, N, S contents and their related characteristic functional groups, therefore increases etching degree on wool fiber surface scales. It was concluded that APPJ treatment is effective in processing wool fiber with high moisture contents.

Microstructure and wear resistance of in situ porous TiO/Cu composites

An in situ porous TiO/Cu composite is successfully prepared using powder metallurgy by the reaction of Ti2CO and Cu powder. Morphological examination of the composite shows that the porosity of composites lies in the range between 10.2% and 35.2%. Dry sliding un-lubricated wear tests show that the wear resistance of the composite is higher than that of the Cu-Al alloy ingot. The coefficient of friction test shows that, as the volume fraction of the reinforced phase increases, the coefficient of friction decreases. The wear rate variation trend of the oil-lubricated wear test results is similar to that of the un-lubricated wear test results. The coefficient of friction for oil lubrication is similar for different volume fractions of the reinforced phase. The wear resistance of the composite at a sliding velocity of 200 rpm is slightly larger than that at 50 rpm. The porosity of the composites enhances the high-velocity oil-lubricated sliding wear resistance.

The amphoteric effect on friction between the bovine cartilage/cartilage surfaces under slightly sheared hydration lubrication mode

The amphoteric effect on the friction between the bovine cartilage/cartilage contacts has been found to be highly sensitive to the pH of an aqueous solution. The cartilage surface was characterized using a combination of the pH, wettability, as well as the interfacial energy and friction coefficient testing methods to support lamellar-repulsive mechanism of hydration lubrication. It has been confirmed experimentally that phospholipidic multi-bilayers are essentially described as lamellar frictionless lubricants protecting the surface of the joints against wear. At the hydrophilicity limit, the low friction would then be due to (a) lamellar slippage of bilayers and (b) a short-range (nanometer-scale) repulsion between the interfaces of negatively charged (PO4⿿) cartilage surfaces, and in addition, contribution of the extracellular matrix (ECM) collagen fibers, hyaluronate, proteoglycans aggregates (PGs), glycoprotein termed lubricin and finally, lamellar PLs phases. In this paper we demonstrate experimentally that the pH sensitivity of cartilage to friction provides a novel concept in joint lubrication on charged surfaces.

Design and manufacture of automated controlled test machine detecting braking characteristic of brake lining in vehicles

This study has been carried out in order to measure friction coefficient of friction materials used in autos through computer program. Variants such as speed, temperature, and pressure have been discussed and the effect of these variants on friction materials of autos. Variants such as speed, temperature, and pressure resulting from various effects in autos have been discussed, the effects of these variants on friction materials have been examined and their friction coefficients have been detected. In the test device whose manufacturing has been completed, temperature value between surface of brake lining and disc used during tests a machinery has been prepared in a way that temperature values are 0–400 ℃, speed values are 0–1400 rev/min, pressure values are 0–1.05 Mpa. In consideration of these dates, it has become possible to constitute friction coefficient–temperature, friction–time and temperature–time diagrams. By benefiting from the tests to be performed through friction coefficient test device, enhancement or progress will be ensured in material selection, technology and theory. Control pf parameters such as speed, temperature, pressure, force, and friction coefficient to be measured are performed easily through test device; moreover, thanks to electronically sensitivity of electronically and mechanical materials used in test device, it is ensured that you can reach the values you want to reach correctly. Friction tests have been carried out on samples having different properties in auto regulative test device. Friction coefficient values of automotive brake linings in the new system design and manufacturing which is carried out, have been in conformity with SAE-J661 Standard and TSE 555-9076 Standard (Turkish Standards Institution). Test results obtained are in parallel with the literature.

Cooper-Carbon Nanostructured Composite Coatings with Controlled Structure

Samples of the Cu-C composite coatings were produced by high-speed ion-plasma magnetron sputtering (HiPMS) with mosaic target (MT). Nanostructure, roughness, mechanical properties as well as electric properties of coatings depend on carbon-cooper ratio. So 10% - 15% cooper con centration (atomic) results in to dry friction coefficient decrease up to 0.1 and wear resistance increase up to 10-17 m3/N·m. The HiPMS method allowed us to effectively sputter very different materials like carbon and cooper at the same velocity with required proportion. At the same time, one could obtain a uniform mixture of ingredients on the atomic level. The coating corresponds to a mixture of nano-sized phases of carbon and cooper. Crystalline dispersion of samples depends on carbon concentration. The obtained products are characterized by XRD, UV (257 nm) and visible (514 nm) Raman spectroscopy. The morphologies are studied with TEM and AFM. Mechanical properties were investigated with friction coefficient and micro hardness tests. There was no chemical interaction during Cu-C precipitation on hot substrate (625 - 725 K). The mechanical properties can be explained by free electrons capture with carbon nanostructures and space charge formation.

Research on Shear Bearing Capacity and Sliding Performance of Modified Mortar Isolation Sliding Layer for Rural Construction

This paper studied the cracking and sliding working performance of modified mortar isolation sliding layer in a sliding isolation technique suitable for the rural construction. The technology realizes the sliding isolation by setting the up and down ring beams at the outdoor ground bonded by low-grade modified mortar and the shear deformation limit by setting rubber beams. Through the compression-shear tests on different grades of modified mortar which mixed with graphite and talc, the horizontal shear strength of different modified mortars have been acquired. the friction performances of different modified mortars have been Compared by the friction coefficient tests,. Through calculating, the sliding performances of modified mortar layer under the seismic actions of different seismic fortification intensities have been achieved. The research shows that the modified mortar sliding layer has well sliding performance, and it is able to meet the demand of sliding isolation of the rural construction.

Experimental investigation on the friction and sealing characteristics of narrow end-face seal ring with spiral grooves for wet clutch

Purpose – The purpose of this paper is to investigate the friction and sealing characteristics of narrow end face seal ring with spiral grooves for wet clutch by experiment. Design/methodology/approach – The shallow spiral grooves are machined in the end face of narrow seal ring by laser, and all of other parameters of specimens are the same with the actual production. The investigation of friction and sealing characteristics are carried out by comparing the experiment results of end face seal ring with spiral grooves with the conventional seal ring without spiral grooves through friction coefficient test, volume leakage rate test and pv value test. Findings – Comparing with conventional seal ring without spiral grooves, seal ring with spiral grooves experiences boundary lubrication, mixed lubrication and fluid film lubrication with the increase of rotation speed, whereas the conventional seal ring only experiences mixed lubrication. Besides this, the volume leakage rate is slightly larger, but the pv value is much larger than that of conventional seal ring. Originality/value – Effect of spiral grooves on the friction and sealing characteristics of narrow end face seal ring for wet clutch is investigated. The improved lubrication performance can be achieved by shallow spiral grooves even if the distance of radius difference used to machine grooves is very small.

Forensic investigation of the cause(s) of slippery ultra-thin bonded wearing course of an asphalt pavement: influence of aggregate mineralogical compositions

The cause(s) of slippery ultra-thin bonded wearing course (UTBWC) of an asphalt pavement was investigated. Petrographic analysis showed that the aggregate used in the UTBWC is mainly limestone with an average acid-insoluble residue of 5.1%. Coefficient of friction tests were performed both on a comparative UTBWC from Virginia with a different aggregate mineralogy VA-UTBWC and on slabs extracted from the slippery UTBWC pavement overlay. The tests clearly showed that the slippery UTBWC overlay sharply declined throughout the polishing process, consistent with the aggregate mineralogical composition and its low amount of acid-insoluble residue. In contrast, the comparative VA-UTBWC mix showed a gradual increase and then decrease in friction with continued polishing. This investigation clearly showed that the cause of the slippery asphalt pavement problem of the road mainly attributed to limestone aggregate polishing.

The influence of the graphene additive on mechanical properties and wear of hot-pressed Si3N4 matrix composites

Abstract The study concerns silicon nitride based composites with an up to 10 wt% graphene nonoflakes (GNP) addition. An XRD and Raman analysis of hot-pressed prepared composites were conducted. The microstructural SEM observations supported by element EDS analysis were also made. Elastic and mechanical properties (Knoop hardness, bending strength, fracture toughness) were measured. The manufactured sinters were put to friction coefficient and wear tests. Wear scars on discs after the abrasion tests were observed by optical and SEM microscopy. Performance examinations of hot-pressed cutting tools were performed.

Dynamic friction coefficient of two plastics against aluminum under impact loading

We present a new dynamic friction coefficient testing device modified from the conventional split Hopkinson pressure bar (SHPB). In the experiment, the normal pressure and friction force are applied to the tribo pair simultaneously via the wedge structure of the incident bar. The geometry of tribo pairs can be cylindrical or cuboid which can be as simple as the samples in SHPB experiments, and the time-resolved interfacial friction coefficient can be directly calculated without any assumptions or theoretical derivation. The interfacial friction between two plastics and aluminum was tested by the novel setup, the normal pressure and friction force histories were measured, and the time-resolved dynamic friction coefficient was obtained.

Interfacial Sliding Properties of Bone Screw Materials and Their Effect on Screw Fixation Strength

This study examined the effect of interfacial sliding and test material properties on the fixation strength and insertional properties of self-tapping bone screws. Various substitute materials (polyacetal [POM], poly(methyl methacrylate) [PMMA] and E-glass-filled Epoxy [Sawbones®]) for human bone were evaluated, and the results were compared with the findings for cadaver bone. Initial coefficient of friction (CoF) of the screw material stainless steel AISI316 was tested using a pin-on-disk apparatus, and the screws were exposed to pullout tests after insertion torque tests. The effect of a smooth diamond-like carbon (DLC) coating was studied by applying the coating on both CoF test balls and bone screws. Mechanical properties of test blocks strongly correlated to both pullout strength and insertion torque of the screws: for noncoated 2.7-mm screws, tensile strength correlated to pullout strength and insertion torque, with Pearson correlation coefficients r=0.977 and r=0.738, respectively. In contrast, CoF correlated strongly to screw insertion torque but not to pullout strength in bone substitute materials (for noncoated 2.7-mm screws, r=0.652 and r=0.248, respectively). There were no significant differences in CoF using noncoated and DLC-coated screw materials against bone substitutes. Proper materials for in vitro testing help in evaluating the biomechanics of the implants in advance. However, choosing the material needs attention, as their ability to model human bone depends on test type.

Finite element analysis of monofilament woven fabrics under uniaxial tension

Mechanical behavior of woven fabrics under tensile load is complex because their deformation could result from the combined effects of tension, compression, bending, and shear. In this study, the tensile behavior of woven fabrics is simulated using finite element method. The input parameters are the mechanical properties of constituent yarns obtained from tensile and friction coefficient tests and the geometry of woven fabric repeating unit. First, a 3D geometric model of the repeating unit based on Pierce’s model was built using computer-aided design tools. Then, finite element analysis which incorporates material properties, frictional contact, and periodic boundary conditions was implemented using ANSYS. A non-linear mechanical behavior was defined. Frictional contact algorithm for the cross-sectional zone of the repeating unit and periodic boundary conditions to the contour of the repeating unit was implemented. Numerical simulation data and experimental data were compared, which showed good agreement.

Research on Skid Resistance and Noise Reduction Properties of Cement Concrete Pavements with Different Surface Textures

AbstractThe present study discusses the use of the new windscreen pavement/tire noise testing method and the lateral friction coefficient test vehicle to test the skid resistance and noise reduction properties of cement concrete pavements with different surface textures and to analyze the skid resistance and noise reduction mechanisms of pavements with different surface textures. The tests show that the improved noise testing equipment can effectively check the interference of outside noise and ensure the accuracy of test data. In addition, by improving the common surface texture of cement concrete pavements, the pavement noise can be reduced and skid resistance is increased. The noise of porous, exposed aggregate, and longitudinally grooved cement concrete pavements is equal to that of asphalt pavements and all of them display good skid-resistant effect.

Research for Sliminess Ratio Control System Based on High Speed On-Off Valve

Airport runway friction coefficient test vehicle is the key equipment to test the runway friction coefficient, it's test precision directly affects the safety of aircraft. The international civil aviation organization prescribed slip ratio is 12%.How to maintain this value is a key part. This thesis aims to do research for this slip ratio control system. High speed on-off valve is its core part. The traditional friction coefficient testing vehicle adopt servo valve. But servo valve is high demanding on its operating environment and its expensive. Using high speed on-off valve is good to avoid these disadvantages. The simulation results show that the method is reliable and effective.

Thermal and Fade Aspects of a Non Asbestos Semi Metallic Disc Brake Pad Formulation with Two Different Resins

The formulation of a brake pad requires the optimization of multiple performance criteria. To achieve a stable and adequate friction (µ), the brake pad materials should have low fade and higher recovery characteristics coupled with less wear and noise. Among the properties mentioned, resistance to fade is very difficult to achieve. The type and amount of resin in the friction material is very critical for structural integrity of the composites. The binder should not deteriorate under any diverse conditions. The thermal stability of friction materials and its capacity to bind its ingredients collectively under diverse conditions depend upon the quality and proportion of resin. The current work evaluates the fade and recovery behaviour of developed friction composites from two different resins which are traditional straight phenolic resin and the alkyl benzene modified phenolic resin. Two brake pads with these different resins were fabricated as per Industrial Standard. TGA is carried between 150 – 4000 C as this zone of temperature is very critical which accounts for the weight loss (Thermal degradation). Friction and wear studies were carried out on a friction coefficient test rig as per SAE J661a standard. The results showed that the fade and wear of the friction materials were closely related to the thermal decomposition of the binder resin and durability of the contact plateaus, which were produced by the compaction of wear debris around hard ingredients on the rubbing surface. It was clearly observed that the friction materials with modified resin showed significant reduction in fade %. Friction materials made with higher thermal stability showed resistance to fade. However wear didn’t show much noticeable changes.

The Friction Coefficient Testing Method of Metallic Sheet and Strip

The research background and the generation of friction are introduced. The importance of the coefficient of friction test in sheet metal forming field is indicated. Standards of coefficient of friction of metallic sheet and other related materials testing method are described. The experimental principle, the size and preparation of testing sample, testing equipment and procedure, result data processing method are presented.

Optimization of Organic Fibres%[Kevlar/Arobocel/Acrylic] in NAO Brake Pad Application and its Effect on Thermal Stability & Friction Characteristics

Organic fibres (Kevlar/ Arbocel / Acrylic) have good thermal stability, higher surface area and bulk density. The optimization of organic fibres percentage for thermal behaviour is considered using TGA. The temperature raise during brake application will be between 150-4000 C and this temperature zone is very critical to determine the fade characteristics during friction testing. Hence, three different friction composites are developed with the same formulation varying only the Kevlar, Arbocel and Acrylic fibres which are compensated by the inert filler namely the barites and are designated as NA01, NA02 and NA03 respectively. After the fabrication, the TGA test reveals that the composite NA03 has minimum weight loss. The friction coefficient test rig is then used to test the friction material as per SAE J661a standards. The results prove that the brake pad with minimum weight loss during TGA has higher friction stability. Thus, we can correlate the thermal stability with the stability of friction.