Friction Materials Research Articles

Synthesis and Thermal Adsorption Characteristics of Silver-Based Hybrid Nanocomposites for Automotive Friction Material Application

Advances in friction materials are imposed on developing multiceramic reinforced hybrid nanocomposites with superior tribomechanical properties. The silver-based matrix metals are gained significance in various applications like bearing, ratchet, and electrical contacts due to their high frictional resistance and good thermal and chemical stability compared to traditional metals. The present research is to develop silver-based hybrid nanocomposites containing alumina (Al2O3) and silicon carbide (SiC) nanoparticles of 50 nm mixing with the ratio of 0 wt% Al2O3/0 wt% SiC, 5 wt% Al2O3/0 wt% SiC, and 5 wt% Al2O3/5 wt% SiC via the semisolid vacuum stir-cast technique. The vacuum technology minimizes casting defects and increases composite properties. The casted composite samples are subjected to study the effect of reinforcement on thermal adsorption, conductivity, diffusivity, and frictional resistance. The composite containing 5 wt% Al2O3np/5 wt% SiCnp is to find optimum thermal and frictional behaviour. The thermal adsorption and frictional resistance are increased by 30% and 27% compared to unreinforced cast silver. The Ag/5 wt% Al2O3np/5 wt% SiCnp hybrid nanocomposite is recommended for automotive friction-bearing applications.

Влияние свойств дискового тормоза с термоизолированными узлами трения на коэффициент трения покоя

The article is devoted to analytical determination of dependences of the static idle friction coefficient of a disc brake with thermally insulated friction nodes on influencing factors and experimental confirmation of the final result obtained. The design of the new disc brake provides two friction units, each of which uses materials with different operating temperatures. A characteristic feature of the brake is the thermal insulation of friction units, which allows each pair of friction to provide its own temperature conditions. Carbon and steel are used as friction materials. The characteristics of contact interaction of the working elements of the disc brake are calculated: the dependence of a contour contact area on the radius of curvature of the tops of undulation waves, contour pressures on complex roughness criteria, the integral coefficient of friction of the disc brake with thermally insulated friction nodes on influencing factors. Experimental verification of the obtained results was carried out on a full-scale facility, which allows measuring the forces of static friction under conditions of real forces, pressures and geometry of the contact area. As a result of the study, it was found that the stress strain state of the contact area under conditions of static force interaction corresponds to an elastic unsaturated contact. In this case, when calculating the static friction, the mechanical component of the friction coefficient can be neglected. It has been experimentally confirmed that with the increase in the normal pressing force of the disc brake elements, the coefficient of static friction decreases, which indicates the elastic nature of the interaction of micro-dimensions. Carbon-based friction material is characterized by lower values of the static friction coefficient for all specified values of the clamping force.

Investigation of structural and thermal analysis of clutch facings with different friction materials

Almost every part of an automobile has been upgraded due to technological progress over the previous century. The automobile industry is a significant contributor to environmental degradation. Automobile engineers have a responsibility to develop innovative approaches to safety and environmental protection. The importance of determining the influence of stress and heat wear on transmitted torque has grown as interest in studying clutches has grown. Composite materials that are safer for the environment make it easier for vehicle developers to provide greater alternatives. This article investigates the potential for replacing conventional clutch facing materials with composites and other suitable materials like sintered metal, Kevlar, and hard steel. Clutch facings composed of base material have been modelled and analysed in Solid Works and ANSYS Workbench, respectively, to achieve this goal. The mechanical characteristics of clutch facings made of three materials have been compared.

Influence of rare earth oxide and graphite on the mechanical and tribological properties of Fe/Cu based sintered friction materials

Fe/Cu-based sintered friction materials are proven potential materials for heavy-duty applications. The current research explores the influence of rare earth oxide (Nd2O3) and graphite on the tribological characteristics of Fe/Cu-based friction materials. The constituents present in the friction material are Fe, Cu, Cg (1%, 3%, 5%, 7%), BaSO4, and Nd2O3 (5%). Optical microscopy and elemental mapping studies reveal the homogeneous distribution of elements in the matrix. Sintered density of the specimens showed a maximum of 70% of the theoretical density measured by Archimedes' principle. XRD analysis shows no new phase formation in all the sintered specimens. A peak microhardness result of 96 HV is obtained in specimen NG-01. The pin-on-disc tribotests are performed at an axial load of 50 N at a sliding velocity of 5.5 m/s. Specimen NG-03 with 3% graphite exhibited an optimum wear rate with a friction coefficient of 0.45. The surface morphology and elemental composition of the worn specimens are investigated. The morphological features inferred that the wear mechanism is predominantly mixed abrasive and adhesive.

IMFREE: A versatile software tool for modelling machining processes with particle methods

The current state-of-the-art for the simulation of machining process is the application of the FEM (finite element method). Nevertheless, the cost of FEM analyses for such problems is high due to their complex multi-physics nature, mesh regeneration issues, and small time-length scales. In contrast, particle methods are an alternative numerical approach well-suited for large deformations as in material's chip formation. In this work, the key features and simulation capabilities of iMFREE are presented, which is a massively parallel and robust particle-based code for machining simulations developed at the ETH Zürich. Various applications of iMFREE are shown, where the efficiency is demonstrated in orthogonal cutting simulations for the optimisation of material removal rates, a chip formation study, the inverse identifications of friction law parameters and material constitutive law parameters. Further, the applicability to single and multiple grain grinding simulations of Ti6Al4V and silicon is shown.

An advanced constitutive model for transversely isotropic rock - Evaluation of two different regularization approaches

The mathematical description of the material behavior of rock is a demanding task in engineering practice. Rock is classified as a frictional cohesive material characterized by highly nonlinear mechanical behavior with irreversible deformation, strain hardening, strain softening and degradation of stiffness. In addition, depending on the origin of a particular rock type, the orientation of minerals and grains as well as the formation of stratification planes lead to inherent anisotropic behavior. Especially in stratified rock types like shales or phyllites, often the special case of transversely isotropic material behavior is encountered. In a previous work, a novel continuum-based material model for describing both, the highly nonlinear and transversely isotropic material behavior of rock, denoted as TI-RDP model, was presented. By means of the linear mapping of the Cauchy stress tensor into a fictitious isotropic configuration, an established isotropic damage plasticity model for rock was extended. In this contribution two different regularization approaches, which are well established for isotropic models, i.e., the mesh-adjusted softening modulus and the implicit gradient-enhancement, are adopted for the TI-RDP model. Based on uniaxial tension and triaxial compression tests considering different orientations of the principal material directions with respect to the direction of axial loading, their capabilities are assessed in terms of predicting the direction-dependent mechanical behavior in a mesh-insensitive manner.

COMPARATIVE FRICTION TESTS OF BRONZE COATINGS FROM SECONDARY MATERIALS

Comparative tribotechnical studies of coated samples based on secondary composite materials on a friction machine is an important direction in the development of technologies to increase wear resistance and reduce friction in various industrial sectors. Secondary composite materials are obtained from production waste, which reduces costs and reduces the environmental burden. One of the examples of these materials are coatings obtained by welding and surfacing methods of electroerosive powders based on copper or a hard alloy from waste of tool industries or waste of non-ferrous metals and alloys. (Research purpose) The research purpose is performing a comparative analysis of tribotechnical properties of samples coated by secondary composite materials on a friction machine. (Materials and methods) Samples with a coating based on secondary materials and samples without a coating were produced for comparative studies. A machine was used to test materials for friction and wear AI 5018. (Results and discussion) It was found that coated samples based on secondary composite materials have higher wear resistance and less friction compared to uncoated samples. The coating based on secondary composite materials has a higher hardness and resistance to wear. It was found that with increasing load and sliding speed, the difference in wear resistance and friction between coated and uncoated samples increases. The coating based on secondary composite materials is particularly effective in conditions of high loads and sliding speeds. (Conclusions) Thus, comparative tribotechnical studies of coated samples based on secondary composite materials on a friction machine have shown that such coatings can be an effective way to increase wear resistance and reduce friction in various industrial sectors.

Investigation on Low Metallic NAO Brake Friction Material for Minimization of Non-Exhaust Pollution

Investigation on Low Metallic NAO Brake Friction Material for Minimization of Non-Exhaust Pollution

Experimental characterization of friction properties of materials for innovative beam-to-column dissipative connection for low-damage RC structures

Low-damage design of structures in seismic-prone areas is becoming an efficient strategy to obtain “earthquake-proof” buildings, i.e. buildings that, even in the case of severe seismic actions, experience a low or negligible amount of damage. Besides the safeguard of human lives, this design strategy aims also to limit the downtime of buildings, which represents a significant source of economic loss, and to ensure an immediate occupancy in the aftermath of an earthquake. In this context, focusing on moment-resisting frames (MRFs), several solutions have been developed for the beam-to-column connections (BCCs) of steel and precast/prestressed concrete structures, but very few for cast-in-situ reinforced concrete (RC) structures. This paper focuses on a recently-proposed friction-based BCC for MRFs made with hybrid steel-trussed concrete beams (HSTCBs). The latter are made by a spatial lattice built using V-shaped rebars and a steel bottom plate, which eases the introduction of a friction dissipative device. HSTCBs are usually characterized by a small effective depth, which leads to a large amount of longitudinal rebars. The latter, together with a small-sized beam-column joint, make it potentially subjected to severe damage, which reduces its dissipative capacity. The shear force acting on the joint can be reduced by endowing the BCC with a friction device, with the aim of increasing the lever arm of the bending moment transferred between beam and joint, preventing the latter from damage. To evaluate the mechanical performance of the above connection, two experimental programs have been carried out at the Structures Laboratory of the University of Palermo. The first one focused on the characterization of the friction properties of two different materials (thermal sprayed aluminum and brass), by means of a linear dissipative device subjected to cyclic load. The second one tested a beam-to-column subassembly endowed with the recently-proposed connection in which the dissipative device was made with the best performing friction material tested before. The results of the cyclic tests are presented and commented, showing the promising performance of such connection in providing a low-damage behavior and a satisfactory dissipative capacity.

Selection of materials formulation for non-asbestos friction materials using entropy weight-based TOPSIS and COPRAS multi-criteria decision making

Selection of materials formulation for non-asbestos friction materials using entropy weight-based TOPSIS and COPRAS multi-criteria decision making

Effect of compression molding temperature on the characterization of asbestos-free composite friction materials for railway applications

<abstract> <p>Brake pads significantly affect the braking performance of railways under both normal and emergency operating conditions. In previous studies, brake pads were made using the hand lay-up method and produced the best properties on specimens with epoxy, rice husk, Al<sub>2</sub>O<sub>3</sub> and Fe<sub>2</sub>O<sub>3</sub> compositions of 50%, 20%, 15% and 15%. However, the resulting density does not meet the density standard set by PT Industri Kereta Api Indonesia (PT INKA), which is 1.7–2.4 g/cm<sup>3</sup>. To date, there has been limited research into the utilization of the compression hot molding method for the production of asbestos-free composite friction materials composed of epoxy, rice husk, Al<sub>2</sub>O<sub>3</sub> and Fe<sub>2</sub>O<sub>3</sub> for railway applications. In this study, we aimed to determine the effect of compression molding temperature on the characterization of composite brake pads for railway applications. The brake pad specimens were made of epoxy resin, rice husk, Al<sub>2</sub>O<sub>3</sub> and Fe<sub>2</sub>O<sub>3</sub> with a composition of 50%, 20%, 15% and 15%, respectively. The manufacture of composites in this study used the compression molding method with a pressure of 20 MPa for 15 min holding time. The mold temperature used were 80, 100, 120 ℃. Density, hardness, tensile, wear, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) tests were performed to evaluate the properties of the specimens obtained. The results demonstrated that an increase in molding temperature improved the characterization of the brake pads, with the best results achieved at a molding temperature of 120 ℃ (SP-3 specimen). SP-3 specimens had the best density, hardness, tensile properties and thermal properties compared to other specimens.</p> </abstract>

Influence of alkali pre-treatments on the physio-mechanical, tribological and thermal performance of hemp fiber reinforced phenolic brake friction material

Influence of alkali pre-treatments on the physio-mechanical, tribological and thermal performance of hemp fiber reinforced phenolic brake friction material

Analysis of the influence of different carbon fibre content on the performance of automotive brake friction materials

Analysis of the influence of different carbon fibre content on the performance of automotive brake friction materials

Analysis of the influence of different carbon fibre content on the performance of automotive brake friction materials

Analysis of the influence of different carbon fibre content on the performance of automotive brake friction materials

Numerical Simulation of Wear in Aircraft Carbon-Carbon Composite Disk Brake​

Friction and wear are two major factors affecting the disk brake service life. Carbon-carbon composite materials have good stable friction properties, which enable them to operate as friction material in aircraft brakes application. This article discusses a wear simulation method for predicting the wear amount of c/c composite aircraft brakes under simulated operating conditions. A modified version of Archard’s wear equation is used in 2-D axisymmetric finite element model in order to predict the disk brake friction surfaces wear progression. The finite element commercial software COMSOL Multiphysics 5.5 is used to simulate wear and is presented in this paper. Wear law was implemented as a boundary ordinary differential equation (ODE) in a COMSOL Multiphysics simulation, considering wear depth (thickness) as the independent variable. Frictional heat generation is simulated as heat affects on material thermal properties and as a result surface deformation. Element removal technique is used to simulate the brake disk geometry thickness change due to the material loss during wear. Wear progression with time is presented. Wear model is verified using experimental work from literature.

Tribological assessment of rice husk ash in eco-friendly brake friction materials

The tribological behavior of new green friction materials with rice husk (RH) and rice husk ash (RHA) is discussed in the current paper. Two formulations developed, one with 6% RH and one with 6% RHA, were compared with a reference formulation with alumina under the AK Master test, through a braking tribometer. Formulation with RHA showed tribological performance equal to or better than the reference material, especially in high temperature applications where the RHA particles assisted in the building of the contact plateaus. Adding RH reduced the abrasive action of the composite, allowing the formation of a more homogeneous tribofilm on the disc than in the other formulations.

DEVELOPMENT AND ANALYSIS OF FRICTION MATERIAL FOR ECO-FRIENDLY BRAKE PAD USING SEASHELL COMPOSITE

Asbestos has been banned in many countries as a result of its negative effects on the environment and human health. As a result, a human-friendly friction material is required to replace asbestos in brake pads. Hence, the powder metallurgy technique was undertaken to develop friction material from locally sourced asbestos-free materials. Seashell was used as base elements with other additives. The filler material considered had a particulate size of 300 µm, and epoxy resin was used as a binder. The produced brake pads were evaluated and compared to commercial brake pads in terms of their physical, mechanical, and tribological properties. According to the investigated properties of the developed brake pads, increasing the seashell content in the formulated brake pads resulted in a decrease in wear rate, and compressive strength. Water absorption, hardness, oil absorption, density, and thermal conductivity all varied differently at the same time. The coefficient of friction of the produced friction material ranges between 0.311-0.353. The results showed that seashell particles could effectively replace asbestos in producing friction material for brake pads in an automobile.

Fe3O4-Filled Cellulose Paper for Triboelectric Nanogenerator Application

Cellulose-based materials have recently drawn much interest due to their sustainability, biodegradability, biocompatibility, and low cost. In this present work, cellulose fiber paper (CFP) was fabricated from sugarcane leaves and used as a friction material for a triboelectric nanogenerator (TENG). Fe3O4 was incorporated to CFP triboelectric material to increase the dielectric constant of CFP for boosting power generation of TENG. The Fe3O4 filled CFP was synthesized using a facile one-pot co-precipitation technique. The effect of Fe3O4 content in CFP on dielectric property and TENG performance was investigated and optimized. The CFP filled with Fe3O4 nanoparticles exhibited the improved dielectric constant and possessed a superior TENG performance than pristine CF. The highest power density of 1.9 W/m2 was achieved, which was able to charge commercial capacitors serving as a power source for small electronic devices.

Analytical Study on the Frictional Behavior of Sliding Surfaces Depending on Ceramic Friction Materials

Friction material, as the main component in a bearing support, allows frictionless behavior between the two connected structures. Previous studies on friction material considered polytetrafluoroethylene (PTFE) and attempted to analyze the resulting friction behavior balance. However, aging PTFE loses its frictionless performances, because PTFE is crushed, causing it to tear, or the lubricant is removed. The performances of the friction material should thus be maintained to preserve the performance of structures. To overcome these issues, this study applies a ceramic friction material owing to its advantages of high strength, low friction, and low deformation. The frictional behavior is investigated on a full-scale model using Finite Element Analysis (FEA) according to the edge type of the ceramic friction material. The main design variables include four edge types, namely, general, camber, round and taper types. The results confirm that the modified edge types (camber, round and taper type) reduced the stress and deformation which, in turn, improved the friction behavior.

Self-powered liquid crystal lens based on a triboelectric nanogenerator

Liquid crystal (LC) is an intermediate state compound between liquid and crystal, which has the anisotropy of crystal molecules while having the fluidity of liquid. It is a cutting-edge technology in optoelectronics. The large-aperture LC lens require larger voltages, and there are certain safety issues and equipment requirements. This situation indicates a great need for a safe and portable low-power device. A triboelectric nanogenerator (TENG) can collect the energy in the environment and convert it into usable electric energy. It has the advantages of small size and convenient portability, and can realize the use of renewable energy. This paper proposes a novel feather TENG (F-TENG) using feathers as friction materials. The approximate values of open-circuit voltage and short circuit current of the manufactured F-TENG can reach 247 V and 27 μA, respectively. After simple processing of the device, the performance can be further improved. We realized the use of F-TENG to power a LC lens test system, thus providing a new application idea for the display field. This study provides a simple and inexpensive method for harvesting mechanical energy to power experimental test equipment and facilitate the large-scale, intelligent practical application of TENG systems.