Friction Pads Research Articles

Seismic performance and damage analysis of RC frame–core tube building with self-centering braces

This paper examines the seismic responses of a reinforced concrete (RC) frame–core tube building with pre-pressed spring self-centering energy dissipation braces (PS-SCEDBs). The PS-SCEDB is a passive energy dissipation device with disc springs and friction pads. Parameters of PS-SCEDBs installed on the structure are designed according to the principle of equivalent stiffness, based on the parameters of a buckling-restrained brace (BRB) equipped on the original RC frame–core tube structure. The constitutive models of self-centering flag-shaped and bilinear elastoplastic hysteresis for PS-SCEDBs and BRBs, respectively, are developed and experimentally verified. The seismic performance of RC frame–core tube structures with PS-SCEDBs and BRBs, respectively, are studied and compared using non-linear time history analysis. Results show that the PS-SCEDB can substantially reduce residual drift ratios of a concentrically braced building while still capable of effectively controlling the peak inter-story drift ratio and damage of components adjacent to braces under rare earthquakes. The structure with PS-SCEDBs can effectively dissipate seismic energy without increasing damage to beams, columns, and shear walls.

Feasibility study of using a semiactive electromagnetic friction damper for seismic response control of horizontally curved bridges

Semiactive control systems have been found to be more effective than passive and active control systems for seismic protection of bridges because of their reliable and adaptable characteristics. This paper presents a comprehensive investigation on the modeling and design of a semiactive electromagnetic friction damper (SEMFD) for the seismic response control of horizontally curved bridges. The proposed SEMFD possesses a simple configuration consisting of a ferromagnetic plate and two arrays of ferromagnetic core coils (FCs) attached to the two sides of the ferromagnetic plate through two friction pads. The attractive magnetic interaction between the FCs arrays and the ferromagnetic plate creates the normal force, which generates friction force as the friction pads and the ferromagnetic plate move relative to each other. The magnitude of this force can be controlled by varying the control current passing through the FCs. This semiactive controller, designed based on the optimal linear quadratic Gaussian control method, is capable of reducing the undesirable effects of stick–slip motion in the damper, while restoring the piston of the SEMFD to its initial position at the end of the excitation. The capability of the proposed SEMFD to mitigate the rigid-body motion of decks of horizontally curved bridges is demonstrated by implementing it into the dynamic model of a horizontally curved bridge prototype. The numerical results indicate that the proposed SEMFD is effective in limiting the motion of the deck and thereby preventing it from unseating, which is one of the most common modes of failure among horizontally curved bridges.

Seismic Performance Test of a Steel Frame with Multi-action Hybrid Dampers

In this study, the effectiveness of a multi-action hybrid damper (MHD) composed of lead rubber bearing (LRB) and friction pad was verified in terms of seismic performance improvement of a frame structure. The LRB and the friction elements are connected in series, so the LRB governs the intial small deformation and the friction determines large deformation behavior. Cyclic loading tests were conducted by using a half scale steel frame structure with the MHD, and the results indicated that the structure became to have the stable trilinear hysteresis with large initial stiffness and first yielding due to the LRB, and the second yielding due to the friction. The MHD could significantly increase the energy dissipation capacity of the structure and the hysteresis curves obtained by tests were almost identical to the analytically estimated ones.

A Novel Actuator System Combining Mechanical Vibration and Magnetic Wheels Capable of Rotational Motion Using Shape Memory Alloy Coils

In every country, large steel bridges, such as cable-stayed bridges, are actively being constructed, and the number of such bridges has been progressively increasing. These bridges are often inspected using drones, but inspection techniques have not been established because of strong winds and thunder. Therefore, robots capable of working in difficult environments are desired. In the present study, a prototype of a rotary actuator system combining two iron disks and two electromagnetic-vibration-type actuators was fabricated. A new operation principle was developed that drives the system using the reaction force of the vibration-type actuator. Two shape memory alloy coils and two friction pads were integrated into the system to enable it to carry out turning operations, which were successfully demonstrated. The proposed actuator system can thus move in any direction. In addition, with this actuator system, both slide-on-ceiling and wall-climbing motions are possible.

Research on Dynamic Characteristics and Compensation of Wire Rope Tension and Load Measurement Based on Hydraulic Connection Device

During the operation of hoist, the speed and acceleration of each wire rope are inconsistent and the inertia force is changed due to the wear of the friction pad on the drum, which makes an impact on the cylinder of the tension balance hydraulic connection device and aggravates the flow pressure loss. It results in the nonlinear friction force between the piston and cylinder and affects the accuracy of wire rope tension and load measured by an oil pressure sensor which is installed on the tension balance hydraulic connecting device. In this paper, the simulation model of the tension balanced hydraulic connecting device is established by AMESim software, and the hydraulic dynamic response under different pressures, flow rates, and speed of a single hydraulic cylinder and tension balanced hydraulic connecting device is analyzed. The Leuven friction model is used to compensate the pressure loss along the course and local pressure loss and calculate the friction force, where specific parameters are determined by experiments. The real‐time compensation experiment of the tension balance hydraulic connecting device proves that the device effectively improves the accuracy of wire rope tension and load monitoring.

Complementary effect of attachment devices in stick insects (Phasmatodea).

Stick insects are well adapted in their locomotion to various surfaces and topographies of natural substrates. Single pad measurements characterised the pretarsal arolia of these insects as shear-sensitive adhesive pads and the tarsal euplantulae as load-sensitive friction pads. Different attachment microstructures on the euplantulae reveal an adaptation of smooth euplantulae to smooth surfaces and nubby eupantulae to a broader range of surface roughness. However, how different attachment pads and claws work in concert and how strong the contribution of different structures is to the overall attachment performance remains unclear. We therefore assessed combinatory effects in the attachment system of two stick insect species with different types of euplantular microstructures by analysing their usage in various posture situations and the performance on different levels of substrate roughness. For comparison, we provide attachment force data of the whole attachment system. The combination of claws, arolia and euplantulae provides mechanical interlocking on rough surfaces, adhesion and friction on smooth surfaces in different directions, and facilitates attachment on different inclines and on a broad range of surface roughness, with the least performance in the range 0.3-1.0 µm. On smooth surfaces, stick insects use arolia always, but employ euplantulae if the body weight can generate load on them (upright, wall). On structured surfaces, claws enable mechanical interlocking at roughnesses higher than 12 µm. On less-structured surfaces, the attachment strength depends on the use of pads and, corroborating earlier studies, favours smooth pads on smooth surfaces, but nubby euplantulae on micro-rough surfaces.

Tribological behavior and mechanism of a magnetic conductive brake pair under action of alternating magnetic field

Abstract Tribological experiments of a brake pair consisting of magnetic conductive organic friction pad and HT250 disc were conducted on a test bench of disc brake. SEM and EDS were used to reveal influence mechanisms. Results showed that both magnetic induction intensity and frequency have important influences on tribological performance. Friction temperature increases slightly with increasing of magnetic induction intensity. Debris is gradually refined and oxidation reaction becomes intensified, which promotes formation of friction layer on worn surface. Braking torque is then increased and braking process becomes more stable. Friction temperature increases greatly with increasing of magnetic field frequency. Increased magnetic frequency could improve wear resistance, but once frequency reaches a high enough value, dislocations aggregates and wear resistance declines.

Development and validation tests of an assembly self-centering energy dissipation brace

This investigation develops and experimentally studies an assembly self-centering energy dissipation (ASCED) brace that consists of an energy dissipation device composed of friction pads, a self-centering device composed of disc springs, and bracing members. The ASCED brace has attractive assembly and adjustment abilities and uses simple mechanics. Cyclic test results of the energy dissipation device demonstrated that it had stable energy dissipation capability without deterioration of the friction pads or loosening of the high-strength bolts. A large-scale ASCED brace specimen was designed, fabricated, and tested under cyclic loadings, and the results verified the adjustability of the ASCED brace and confirmed the cooperation performance of the energy dissipation device and the self-centering device. Repeatable flag-shaped hysteretic responses and a smooth transition of stiffness between different stages were observed. These results demonstrated the favorable seismic performance of the brace. The residual deformation was negligible when the pre-pressed force of disc spring was greater than the friction force provided by the energy dissipation device.

An Inchworm-inspired Robot Based on Modular Body, Electronics and Passive Friction Pads Performing the Two-anchor Crawl Gait

We have created an inchworm robot capable of the two-anchor crawl gait on level ground and inclined plane. The main novelty is in the design of the inchworm: (1) three-part body that is 3D printed and actuated by two servo motors to allow a looping and lengthening action, (2) passive friction pads to anchor the feet, each of which may be disengaged using a servo motor actuated lever arm, and (3) modular body and electronics. The robot is about 2 feet (61 cm) in length, has a mass of about 4 kg, and uses an open-loop controller to achieve steady crawling gait. The inchworm robot achieved a speed of 2.54 cm·s−1 on level ground as well as on an incline plane of 19°. The energy usage as measured by the Mechanical Cost of Transport (a non-dimensional number defined as the energy used per unit weight per unit distance moved) is 3.34. Our results indicate that simple robotic designs that copy the basic features of natural organisms provide a promising alternative over conventional wheeled robots.

EXPERIMENTAL RESEARCHES OF ENERGYLOADING OF FRICTION PAIRS OF DISC BRAKES OF VEHICLES (part three)

The friction process in metal-polymer friction pairs of disk brakes is related to high-energy phenomena. For its implementation, it is necessary to supply a lot of energy from outside. The tribosystem is considered to be electro- and thermal-dynamically stable when it has a minimum reserve of internal energy. Thus, in order to ensure electro-dynamic and, as a consequence, thermal-dynamic conditions for the operation of the tribounit, it must dissipate the supplied thermal energy so that the materials of the friction pads do not reach the allowable surface temperature. This thermodynamic state is the criterion for stabilizing the process of friction and wear. At the same time energy dissipation proceeds through mechanical, physical and chemical processes that occur in the surface and near-surface layers of metal-polymer friction pairs of the disk brake. However, this is not enough and therefore the friction pairs of the disk brake must be cooled by counter flows of air when the vehicle is moving. In the materials of the article, the energyloading of the serial brake discs and with the cooling elements of self-ventilated brake discs used in the subcategories of trucks is estimated. The efficiency of forced air cooling of brake friction pairs of vehicles is established. In this publication, the following questions are considered: features of carrying out of experimental researches of disk brakes of vehicles; means for carrying out experimental researches of disk brakes; results of the assessment of the energyloading of friction pairs of disk brakes of vehicles.

Experimental analysis of beam-to-column joints equipped with sprayed aluminium friction dampers

In this paper, the results of an experimental analysis regarding beam-to-column joints equipped with friction dampers are presented. Even though the overall concept is not new, the connection structural detail and the friction pad material are different from previous proposals. In particular, the beam is connected to the column with a classical fixed T-stub fastening the upper flange and a friction damper located at the beam lower flange. The friction damper is composed of a stack of steel plates conceived to assure symmetrical friction. The friction pads are made of steel plates coated with thermally sprayed aluminium. The friction damper is designed in order to slide for a force level equal to or lower than the ratio between the nominal flexural resistance of the connected beam and the lever arm, i.e. the distance between the top T-stub and the friction damper. In this way, it is possible to obtain connections able to dissipate the seismic input energy almost without any damage to the steel elements, provided that all the joint components are designed with sufficient over-strength with respect to the actions corresponding to the friction damper sliding force. In this paper, such approach is validated reporting the results of an experimental campaign.

Relationship between shear energy input and sedimentation properties of exopolysaccharide-producing Streptococcus thermophilus strains

Besides fermentation, the production of bacterial starter cultures includes another crucial step, namely, the separation of the bacteria cells. This separation is most commonly carried out with disc stack separators and needs to be adjusted to the respective strain to obtain a high cell recovery rate. Exopolysaccharides (EPS) produced by several starter cultures, however, have a large negative impact on the separation properties of the cells. These EPS can be divided into cell-bound capsular EPS or free EPS that are released into the surrounding fermentation medium. To improve the separation step, shear forces were applied after fermentation with a gear ring disperser to simulate the impact of a homogenizer and the influence on the separation properties of six Streptococcus thermophilus strains was examined. In case of capsular EPS, the sedimentation velocity of the bacteria increased due to shearing off the capsular EPS layer. Shearing media with free EPS resulted in a viscosity decrease and, hence, in a higher sedimentation velocity, as was determined using a disc centrifuge and a LUMiSizer. Sediment compression as measured with the LUMiSizer was also affected by the shearing step. The results of this study suggest that a defined shear treatment of EPS producing bacterial starter cultures leads to improved separation properties and, hence, higher bacteria yields. We assume that both EPS types affect separation efficiency of the bacteria cells, free EPS because of increased media viscosity and capsular EPS because they act like a friction pad.

Characterization of holding brake friction pad surface after pin-on-plate wear test

This article concerns the metrological characterization of the surface on a holding brake friction material pin after a pin-on-plate (POP) wear test. The POP test induces the formation of surface plateaus that affect brake performances such as wear, friction, noise and heat. Three different materials’ surfaces have been characterized after wear from data obtained with a focus variation 3D microscope. A new surface characterization approach with plateau identification is proposed, using the number of plateau on the surface, equivalent diameter, length and breadth as measurands. The identification method is based on determining and imposing ISO 27158-2 lower plateau limit (LPL) in material probability curves; and on applying a combined criterion of height segmentation threshold and equivalent diameter threshold. The method determines the criterion thresholds for each material since LPL appears typical by material. The proposed method has allowed quantifying the surface topography at two different levels of wear. An expanded measurement uncertainty of 3.5 µm for plateau dimensions in the range 50–2000 µm and one of 0.15 µm for plateau heights up to 10 µm have been documented.

Aplicação de Técnicas de Planejamento de Experimentos para Otimização do Comportamento Tribológico e Térmico de Materiais de Atrito Durante o Processo de Frenagem

RESUMO Sistemas de freio têm a finalidade de reduzir ou manter a velocidade de um veículo, levá-lo à imobilidade ou mantê-lo imóvel. O princípio básico dos sistemas de freios por atrito é a conversão da energia cinética do veículo em energia térmica. Neste estudo, buscou-se analisar os parâmetros de operação de um sistema de freio a disco para motocicletas utilizando-se um banco de ensaios baseado no procedimento Krauss, descrita pela norma ABNT NBR 6143/1995. Optou-se por conduzir um Experimento fatorial completo 2³, em que os três fatores de controle considerados (tipo de disco de freio, tipo de pastilha e o valor da pressão de acionamento da manete de freio) foram alterados deliberadamente em dois níveis cada. Analisou-se as propriedades dos materiais envolvidos novos e após um determinado tempo de uso, denominado materiais assentados. Para avaliar o desempenho do sistema de freio durante o processo de frenagem, analisaram-se duas variáveis de resposta simultaneamente: coeficiente de atrito e temperatura final. A partir dos experimentos, o desempenho tribológico mais satisfatório ocorreu para os materiais constituintes do par de atrito, disco e pastilhas, assentados, e um menor valor de pressão de acionamento da manete de freio. Já para a temperatura, o melhor resultado ocorreu para os materiais do par de atrito novo e um menor valor de pressão. Com o intuito de encontrar a melhor combinação dos níveis de cada fator que otimize o desempenho global destas duas variáveis resposta, foi proposta uma técnica de otimização de múltiplas respostas. Como resultado, obteve-se os níveis assentados do par de atrito e o menor valor de pressão como os capazes de otimizar as duas variáveis resposta simultaneamente. Por fim, o banco de ensaios foi adaptado com um motor de maior potência, o que possibilitou evidenciar e esclarecer mais sobre o efeito brake fade.

Development of a Multiaction Hybrid Damper for Passive Energy Dissipation

A multiaction hybrid damper (MHD) is designed to have independent hysteretic characteristics under small and large loading conditions, and its control performance for building structures excited by wind or earthquake load is verified. The MHD is composed of steel elements, two friction pads, and two lead rubber bearings (LRBs). Because the friction pads and the LRBs are in series connection, only the LRBs deform before the friction pad slippage occurs. After the friction slippage, the damper deformation concentrates on the friction pads. The initial stiffness and hysteresis are dependent on the properties of the LRB, and the maximum force is determined by the friction pad. Accordingly, the load‐deformation behaviors before/after the friction slippage can be independently designed to show optimal performance for a building structure subject to wind and earthquake loads. The cyclic loading tests of a full scale MHD were conducted to evaluate the multiaction behaviors and energy dissipation capacity of the MHD. The control performance of the MHD damper is analytically investigated by using a 20‐story steel structure subject to wind loads and a 15‐story RC structure excited by earthquake loads. The MHD damper showed good performance for reducing both the linear wind‐induced and nonlinear earthquake‐induced responses.

Optimum distribution of steel slit-friction hybrid dampers based on life cycle cost

This study investigated the seismic performance of a hybrid damper composed of a steel slit plate and friction pads, and an optimum retrofit scheme was developed based on life cycle cost. A sample hybrid damper was tested under cyclic loading to confirm its validity as a damping device and to construct its nonlinear analysis model. The effectiveness of the optimum damper distribution schemes was investigated by comparing the seismic fragility and the life cycle costs of the model structure before and after the retrofit. The test results showed that the damper behaved stably throughout the loading history. Numerical analysis results showed that the slit-friction hybrid dampers optimally distributed based on life cycle cost proved to be effective in minimizing the failure probability and the repair cost after earthquakes.

A Study on Convergence Contact Behavior of Friction Heat and Pad on Disk Brake

A Study on Convergence Contact Behavior of Friction Heat and Pad on Disk Brake

Heat transfer problem analysis in three dimension tromol brake system problem

One of the physical problems that can be found in heat transfer is heat transfer to a vehicle brake. In this study a focused vehicle is a motorcycle. Where the heat transfer of the brake system on the motorcycle in this study was completed finite element method. The purpose of this study is to analyse one of the problems of displacement in the three dimensions of the motorcycle brake. So, the results obtained in the form of the best time in the braking for motorcycles. The settlement method is to use one of the partial differential equations for heat transfer. One of them is the Elemenisation model is the braking system. As is known braking system is a system used to slow and stop the vehicle. During the braking phase, the vehicle's kinetic energy will be converted into heat energy due to the friction action of the brake system. The heat flux produced by effects to the brake lining is ideally dissipated into the environment to avoid brake friction pad emissions. The heat produced has a tendency to evaporate the brake fluid and the disc brake surfaces will become hot. Based on the results obtained, when the braking system is in operation, the most significant heat transfer in t = 3.8s. This time is the best time to avoid excessive brake fluid evaporation and the rapid breakdown of the brake surface due to excessive heat.

Accurate Brake Torque Estimation With Adaptive Uncertainty Compensation Using a Brake Force Distribution Characteristic

This paper presents an adaptive individual brake torque estimation method based on the characteristic of front-to-rear brake force distribution ratio. Most previous studies on tire force estimation have assumed that brake torques can be calculated out of brake pressure and given fixed brake gains. However, brake gains are proportional to brake pad friction coefficients, which are influenced significantly by operating or weather conditions. In this paper, it is assumed that the pad friction coefficients are the only uncertainties of the wheel dynamics model since they vary significantly according to the driving conditions. Furthermore, the vehicle specific brake force distribution is used to obtain the additional information. Thus, more practical aspects can be considered when calculating the brake torque. The developed algorithm is verified through simulations and experiments using a production vehicle, and it confirms that the estimation performance is improved significantly compared with that without uncertainty compensation.

Design, construction and performance of a novel brake pad friction tester

Determination of the tribological behavior of brake pads under real environmental conditions is an important and critical task which can significantly impact the automotive industry. Most studies simulate or measure the variants by indirect methods and accept them as true results. The new computer-controlled, interactive brake pad friction tester presented in this study was developed for this purpose. The major components of the machine, which are operated simultaneously, include: a proportional pressure-controlled hydraulics power pack, a mechanical transmission system with electromagnetic clutch, and a brake and automation control with SCADA computer analysis interface. Compared to other friction testing machines, a very important innovation of the newly developed friction tester allows for the testing of the brake pad samples and measuring of the noise level both to be performed with high precision under real conditions. Moreover, this friction tester is capable of determining the friction coefficients; wear behavior, temperature, and life intervals of brake pad samples. This novel brake pad system is relatively cheaper and measures effective friction coefficients more accurately. The uncertainty in measurements for friction coefficient and wear rate was approximately calculated as ±0.0135 and ±0.170 in all of experiments, respectively. In this study, the machine performance was carried out to evaluate the friction behavior of non-asbestos brake pad samples reinforced with hazelnut shell powder according to the standard brake lining quality control testing procedure (SAE J661).