Friction Coefficient Test Research Articles

KARAKTERISASI BAHAN KAMPAS REM SEPEDA MOTOR DARI KOMPOSIT SERBUK KAYU JATI

Commonly the prime material for brake pad of the commercial motorcycle using asbestos, these materials cause a disease like as cancer of respiration if the abrasive particles were sniffed. The SKJ ( Serbuk Kayu Jati ) brake pad is alternative to replacement the asbestos brake pads. The mechanical test includes a wear test, hardeness test, friction coefficient test, and heat resistant test. The hot press process for SKJ as main material of brake pad based by variation of temperature there are 160ºC, 170ºC, and 180ºC. The optimum test result of SKJ brake pads is a variation of 180ºC with wear test result is 3,36 x 10-7 mm 2 /kg, the hardeness result is 25,1 BHN, the friction coefficient test is 0,59 and not damaged on the heat resistant test with a temperature of 300ºC during an hour.

Thermo-Mechanical Properties of Motor Vehicle Brake Pad Using Periwinkle Shell and Treated Cow Bone as Filler

Brake pad was produced using periwinkle shell and treated cow borne as base materials, phenolic resin as binder, material, aluminum oxide, copper oxide and zinc oxide as abrasive, and graphite as friction modifier. The particulate size of the filler materials considered was 250µm, Five samples were produced (Samples A, B, C, D and E) witht composition ratios of 60/25, 55/30, 40/35, 45/40 and 40/45 cow bone/periwinkle shell hybrid filler respectively. The produced brake pad samples were evaluated by testing the mechanical, thermal and physical properties. The hardness test showed that as the filler loading increases, there was a steady increase in hardness strength of the material and sample E showed (100.0) most closest hardness value to the required standard (101.0 Shore). The abrasion resistance showed a decrease with increasing filler loading, which could be due to poor interfacial adhesion between binder (PR) and other components due to poor distribution ratio of the filler quantity in the matrix (binder). The impact strength test result revealed that the higher the filler loading, the lower the average impact strength and samples A, B and C met the required standard brake pad impact strength; except for samples D and E, which could be due to the decrease in the quantity of binder (PR). The water absorption test result showed progressive increase in water absorption with increasing filler loading. Samples A and B with water absorption of 5.56% and 6.25% respectively were found to fall wthin the range of the required standard of 4.5%. The coefficient of friction test result showed a steady decrease as the filler loading increased, however, sample E with 0.36µ exhibited a coefficient of friction within the required standard range for automobile vehicles with a coefficient of fiction range of 0.35 – 0.42 µ. The Therrmo Gravimetric Analysis (TGA) test result for sample A was chosen because it proved to give superior performance over others. Sample A showed a percent weight loss as the temperature increased from 299.00°C to 88714°C. Sample A showed thermal stability at 299°C with degradation setting in at 470.07°C and with a percent weight loss of 24.715%.

Laboratory evaluation on functional characteristics of open-graded epoxy asphalt mixture

Epoxy asphalt binder is one kind of thermosetting asphalt binder composed by epoxy resin and asphalt mixed with curing agent in a certain temperature and a certain proportion. Relying on its excellent high temperature stability performance and strength characteristics, in recent years, epoxy asphalt has achieved successful application on many multi-span steel bridge deck pavement projects in China. In order to better grasp the functional characteristics such as drainage, noise reduction and anti-skid performance of open-graded epoxy asphalt mixture, this paper selects the epoxy asphalt as a cementing material to form OGFC4.75 and OGFC13 asphalt mixture. The permeable performance test, the pendulum test, the dynamic friction coefficient test and acoustic absorption coefficient test were applied to research the functional properties of epoxy asphalt mixture, the test results show that the larger size of OGFC gradation mixture has better permeability performance, then permeability performance of PG64 is slightly better than that of epoxy asphalt mixture. The pavement anti-skid performance of epoxy asphalt binder is better than that of PG64 asphalt binder. The acoustic absorption coefficient test shows that the epoxy asphalt can improve the noise reduction performance.

Drill-in fluid loss mechanisms in brittle gas shale: A case study in the Longmaxi Formation, Sichuan Basin, China

Brittle gas shale consists of a high content of brittle mineral and developed natural fractures and has become the focus of petroleum industry in recent years. Lost circulation may easily occur due to the long soaking time and an overbalanced pressure difference during the drill-in process of the horizontal long section. The dynamic fracture width simulation induced by drill-in fluid invasion, plugging zone pressure containment test, friction coefficient test between lost circulation materials and shale surface, oil based drill-in fluid filtrate immersion test were conducted to investigate the drill-in fluid loss mechanisms in the brittle Longmaxi Shale in the Sichuan Basin of China. Results show that the fracture width at the fracture mouth increased from 2 μm to 239 μm for the two mutually perpendicular fractures connecting to the wellbore due to drill-in fluid invasion. Effective plugging for dynamic fractures was failed to be achieved for the original drill-in fluid. Fracture width increase induced by drill-in fluid invasion is the major cause of plugging failure of brittle gas shale. Instability of the brittle shale induced by oil phase lubrication and high pH drill-in fluid erosion further exacerbates lost circulation problems. Optimized LCMs considering the dynamic apertures of fractures should be selected and added into drill-in fluid to rapidly seal pre-exiting fractures and induced fractures for lost circulation control in brittle shale. The results serve as a guide for the drill-in fluid design of shale gas in brittle gas shale formation.

Effect of alloying elements on the microstructure, coefficient of friction, in-vitro corrosion and antibacterial nature of selected Ti-Nb alloys

Ti-Nb alloys having compositions Ti-24Nb-4Zr-8Sn, Ti-29Nb-13Ta-7Zr and Ti-35Nb-4Sn were synthesized by vacuum arc melting followed by ageing at 1273 K for 6 h in Ar atmosphere. The alloys were characterized by field emmision scanning electron microscopy (FESEM), transmission electron microscopy (TEM), micro X-ray diffraction, friction coefficient and nanohardness tests. In-vitro corrosion of the alloys were studied by potentiodynamic polarisation in body simulated fluid at 37 ○C. The alloy surfaces were exposed to staphylococcus aureus bacteria under controlled environment and the retention of the bacteria was examined by confocal laser scanning microscopy. The alloys had different ratios of α, β phases, different nature of inclusion, and dislocation pile-up resulting in high hardness. Alloys also had good resistance to in-vitro corrosion, low coefficient of friction and were resistant to bacterial growth as compared to commercially pure (CP) Ti. The coefficient of friction was lowest for Ti-24Nb-4Zr-8Sn and it increased with increasing Nb content. The resistance to bacterial growth on the surface increased with increasing volume fraction of β phase in the alloy.

Role of solid lubricant (MoS2 and graphite) variations on characteristics of brake lining composite

Solid lubricants have an essential role in brake lining composite. They can reduce wear that occurs either on the brake lining composite or the contact surface. In this study, the effect of solid lubricants (MoS2 and graphite) on brake lining composite at various sliding speeds and contact pressure has been investigated. Three brake lining composites were made with the same formulation except for the addition of the solid lubricants, all of which have 15% graphite, 12% graphite + 3% MoS2, and 9% graphite + 6% MoS2. The coefficient of friction test with various contact pressure and sliding speed was conducted by using a pin on disc tribometer. The result showed that coefficient of friction and specific wear was strongly influenced by the solid lubricant. Compared with graphite, MoS2 had a better lubrication performance. An increase in MoS2 content decreased the coefficient of friction either on contact pressure or sliding speed variation. MoS2 also reduced the specific wear as well as the temperature rise in the disc.

THE INFLUENCE OF UNIAXIAL COMPRESSION ON THE FRICTION COEFFICIENT (POLYMER–STEEL PAIR), WEAR, AND HARDNESS IN SELECTED THERMOPLASTICS

Plastic plain bearings are deformed during assembly. According to one of the leading manufacturers of plastic sliding elements, the bushing’s internal diameter may be reduced by up to 2.5%. Moreover, plastic sliding elements are increasingly used in harsh conditions (e.g., under high pressure). However, there are no papers that describe the influence of deformation under compression on the tribological properties of plastics. Specimens made of PTFE, PA6, and PE-HD were deformed while conducting the current research, and this deformation was maintained during cooperation with steel. The results of microhardness, wear, and the coefficient of friction tests were compared to data gathered during tests of non-deformed specimens. During deformation under compression (e ≈ 6%), microhardness lowered by up to 30% (PTFE). A significant reduction of hardness (by up to 15%) was observed when strain was only 2%, and up to this value of strain, there is mainly elastic deformation in the polymer. Changes of the coefficient of friction values were insignificant. In terms of PTFE and PE-HD, during deformation under compression up to e ≈ 6% , the block scar volumes were 20% and 40% larger, respectively, than the non-deformed form of specimens. In terms of PA6, the change in block scar volume was insignificant. It may seem that tension and compression ought to cause totally different effects. However, the comparison of the current results and the results described in the previous paper exposes that these two different processes led to the same effects – reducing hardness and increasing wear. Deformation of plastic sliding components as an effect of assembly appears to be minor; however, it affects polymer microhardness and wear resistance.

Tribological study of low friction DLC:Ti and MoS2 thin films

Purpose: The purpose of this article is to characterize and compare the microstructure and tribological properties of low friction DLC:Ti and MoS2 thin films deposited on the austenitic steel X6CrNiMoTi17-12-2 substrate. Design/methodology/approach: In the research, the samples of the DLC:Ti and MoS2 thin films deposited by PACVD technology and magnetron sputtering method respectively were used. Observations of topography were made using atomic force microscope (AFM). Adhesion of the coating to the substrate material was verified by the scratch test. The friction coefficient and wear rate of the coating were determined in the ball-on-disc test. Findings: AFM as well as adhesion and friction coefficient tests confirmed low friction nature of MoS2 and DLC:Ti coatings. During the research information on the behaviour of coatings under tribological load was obtained. The investigated coating reveals high wear resistance and good adhesion to the substrate. Practical implications: The area of testing of low-friction thin films is widely studied due to their practical application. Intensive development of new technologies requires the introduction of corresponding layers of both full protective functions and reducing friction. Originality/value: Growing area of low-friction coatings with specific properties requires thorough tribological and topographical research, which is closely related to these properties.

Optimizing grafting thickness of zwitterionic sulfobetaine polymer on cross-linked polyethylene surface to reduce friction coefficient

The purpose of this study involves reducing the friction coefficient of cross-linked polyethylene (CLPE) by optimizing the grafting thickness of zwitterionic poly(2-(methacryloyloxy)ethyl dimethyl-(3-sulfopropyl)ammonium hydroxide) (PMEDSAH) via a photo-induced free radical polymerization process. Cross-sectional TEM images and XPS spectra indicated that the PMEDSAH layers were successfully grafted on the CLPE. The grafting thickness increased when UV-irradiation time, UV-irradiation energy, and MEDSAH monomer concentration increased. The contact angle data indicated that the PMEDSAH layers successfully imparted hydrophilicity (below 20°) on the CLPE surface. The friction coefficient test and the resulting 3-D confocal images confirmed a significant decrease in the friction coefficient with increases in the grafting thickness. A minimum grafting thickness of 200 nm PMEDSAH was required to minimize the friction coefficient in an aqueous medium. However, a PMEDSAH-grafting thickness of approximately 40 nm was sufficient to reveal the minimized friction coefficient in simulated body fluids (ionic buffer solution) due to the salt-induced hydration effect. The results defined the minimum required thickness of PMEDSAH grafting to minimize the friction coefficient on CLPE surface that can potentially be applied for artificial hip joints.

Evolution law of the friction coefficient and fatigue test of the hold-down spring model for nuclear reactor vessel internals

A reactor pressure vessel may be opened as much as 200 times during its design lifetime of 60 years. A preloading operation is required when a Hold-down Springs (HDS) are opened and closed; hence, the size of a load is essential for the safe operation of a reactor. The friction coefficient of the HDS and the container flange significantly affect the preload. In this study, a mathematical model of the axial load P and the friction coefficient f are established based on the mathematical derivation of a physical model of the HDS. A set of test devices for simulating the preloading process of the HDS is designed according to similarity criteria. Results of the cyclic loading test indicate that the amount of deformation decreases, whereas the friction coefficient increases, as the times of cyclic loading increases under the same loading condition. The friction coefficient increases from approximately 0.3 at the initial loading to approximately 0.6 at the 200th cyclic loading. The results show that enveloped areas are present in the loading and unloading curves of the HDS because of the instability and slip of the ring structure and the hysteresis of the load. Moreover, an increase in the opening times of the reactor pressure vessel will lead to the same displacement; thus, preload will also increase. The evolution law of the fatigue cycle, the friction coefficient, and the mathematical model of the load provide an effective method for accurately calculating preload. An effective preload ensures the safe and reliable operation of a reactor.

EXPERIMENTAL EVALUATION OF DRAW BEAD COEFFICIENT OF FRICTION

In this paper the results of both friction coefficient and springback testing using a drawbead test are presented. Deep drawing quality steel sheet (DC04 according to EN 10130:2009 standard) was used as the test material. The experimental investigations were carried out using a special device that allows a change in the degree of deformation of the sheet metal on the drawbead. The friction tests were carried out for different values of tool surface roughness, specimen widths and degrees of sheet deformation. Three lubrication conditions were analysed: dry friction, machine oil lubrication and lubrication using methacrylic resin. The springback values were determined based on digital image analysis for selected friction conditions. It was found that the effectiveness of reducing the value of the friction coefficient during the pulling of a sheet on the drawbead depends not only on the lubricant used, but also on the degree of sheet deformation (displacement of the middle roll). The sheet widths influence the friction coefficient value through the character of sheet deformation during the pulling of the sheet through the drawbead.

Formation mechanism and mechanical properties of surface nanocrystallized Ti–6Al–4V alloy processed by surface mechanical attrition treatment

In the present work, surface mechanical attrition treatment (SMAT) was proposed to achieve surface nanocrystallization on Ti–6Al–4V surface via high-energy planetary ball milling method using a planetary ball mill. The characteristics of microstructure were studied using different methods. Surface nanocrystallization is achieved on Ti–6Al–4V substrate. The process of refinement could be summarized into four steps. During the refinement process, the reticular continuous beta phase performs a significant role, it cracked, broke up and moved to each side along the grain boundaries. The movement of beta grains has the capabilities of effectively optimizing the grain orientation and accelerating the further refinement of alpha grains. Twinning also plays an important role during the refinement. The grain orientation between different types of grains seems to be larger than that of same type grains. The interface will be divided into smaller nanocrystalline grains once the dislocation density breaks the threshold. Then, the balance will be achieved again and owns a higher critical value which cannot be broken, then a stable grain size can be achieved ultimately. The results of microhardness, friction coefficient and wear mass loss tests of SMAT samples indicate that the mechanical behaviors of substrate are greatly enhanced after this novel SMAT treatment.

Tribological Characteristics of Silicon Carbide – Epoxy Nanocomposites

The applications of polymer nanocomposites have been increased in fast, in technological applications and engineering materials for seal and sliding components in many machines, devices, tools and variance vehicles. In this research friction and wear coefficients of epoxy reinforced by nanoparticles silicon carbide in terms of variance volume fractions have been tested. Mechanical – layup method with ultrasonic technique for the dispersion of the nanoparticles within the polymer matrix are used. Wear and friction coefficient tests are created out using pin -on-disc technique. The results showed significant improvement in wear resistance and low coefficient of friction for 10 vol. % nanocomposites compared with the matrix alone. It can be concluded from scanning electron microscopy (SEM) results before and after the tests that the wear was transformed from the severe to the moderate.

Predictive multiscale computational model of shoe-floor coefficient of friction

Understanding the frictional interactions between the shoe and floor during walking is critical to prevention of slips and falls, particularly when contaminants are present. A multiscale finite element model of shoe-floor-contaminant friction was developed that takes into account the surface and material characteristics of the shoe and flooring in microscopic and macroscopic scales. The model calculates shoe-floor coefficient of friction (COF) in boundary lubrication regime where effects of adhesion friction and hydrodynamic pressures are negligible. The validity of model outputs was assessed by comparing model predictions to the experimental results from mechanical COF testing. The multiscale model estimates were linearly related to the experimental results (p < 0.0001). The model predicted 73% of variability in experimentally-measured shoe-floor-contaminant COF. The results demonstrate the potential of multiscale finite element modeling in aiding slip-resistant shoe and flooring design and reducing slip and fall injuries.

Friction coefficient and limiter load test analysis by flexibility coefficient model of Hold-Down Spring of nuclear reactor vessel internals

Abstract The friction force between the contact surfaces of a reactor internal hold-down spring (HDS) and core barrel flanges can directly influence the axial stiffness of an HDS. However, friction coefficient cannot be obtained through theoretical analysis. This study performs a mathematical deduction of the physical model of an HDS. Moreover, a mathematical model of axial load P, displacement δ, and flexibility coefficient is established, and a set of test apparatuses is designed to simulate the preloading process of the HDS. According to the experimental research and theoretical analysis, P-δ curves and the flexibility coefficient λ are obtained in the loading processes of the HDS. The friction coefficient f of the M1000 HDS is further calculated as 0.224. The displacement limit load value (4,638 kN) can be obtained through a displacement limit experiment. With the friction coefficient considered, the theoretical load is 4,271 kN, which is relatively close to the experimental result. Thus, the friction coefficient exerts an influence on the displacement limit load P. The friction coefficient should be considered in the design analysis for HDS.

Investigation of drill-in fluids damage and its impact on wellbore stability in Longmaxi shale reservoir

The stability of the horizontal long section wellbore is the key factor of restricting the efficient development of shale gas. High clay mineral content and developed microfractures of shale reservoir make the problems of formation damage and horizontal wellbore stability more complex. OBDF (Oil-based drill-in fluid) is widely used to control formation damage and prevent wellbore instability in shale gas wells. However, high cost and serious environmental problem severely restrict the economic development of shale gas. In order to meet the requirement of cost reduction and environmental protection during shale gas drilling operation, drilling horizontal well with WBDF (water-based drill-in fluid) instead of OBDF has become one of the engineering technology problems to be solved urgently. The Longmaxi shale in Sichuan Basin of China and the associated drill-in fluids at the site are the object of our research. Evaluation experiments on liquid damage and sealing capacity of drill-in fluids were conducted to recognize and optimize the properties of oil-based and water-based drill-in fluids in shale reservoir. Combining the methods of particle size distribution, friction coefficient testing, alkali erosion, linear expansion and immersion test, we investigated the effect of drill-in fluids on formation damage and wellbore stability. Results show that the damage degree of OBDF filtrate on shale is more severe than that of WBDF filtrate. Fracture sealing and bi-directional pressure containment capacity of WBDF is also stronger than that of OBDF. Due to the invasion of OBDF with high pH value, the friction strength of the fracture surface decreases and frictional sliding will take place, which can cause the wellbore instability. With the WBDF immersion, microfractures initiate and propagate along the bedding surface for the shale hydrate expansion, and lead to wellbore instability. The results of our analysis suggest that OBDF does not completely solve the problems of formation damage and wellbore instability in shale reservoir, and reinforcing the sealing fracture and inhibiting hydration capacity of WBDF will contribute to its wider application in shale reservoir. This study provides a theoretical guidance for drill-in fluid selection and optimization during the operation of shale gas well drilling.

Modification of Silumin Using the Electroexplosive Method

Surface modification of silumin of the grade AK12 with plasma formed during an electrical explosion of aluminum foil with a sample of yttrium oxide powder placed in the explosion region (the electroexplosive doping method) is carried out. The thermodynamic analysis of the system Al-Si-Y-O is carried out. The phases formed in this system under equilibrium conditions are revealed. Investigations of the elemental and phase composition and the defective substructure are carried out. Mechanical (microhardness) and tribological (wear resistance and friction coefficient) tests of the modified material are performed. The physical mechanisms responsible for multiple enhancement of surface properties of the modified silumin samples are revealed.

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 &lt;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.