Rubber Block Research Articles

Low velocity impact resistance of thin and toughened carbon fibre reinforced epoxy

This study investigates the effect of core-shell rubber nanoparticle and block copolymer matrix modifications on the low velocity impact resistance of thin (∼1.6 mm), multi-axial carbon fibre reinforced epoxy laminates. The results demonstrate a strongly enhanced damage resistance predominantly to impact energies of 9 J and 13 J. Lower impact energies do not sufficiently activate the energy dissipating capabilities of the applied toughening agents. In the case of 9 J impacts, it is found that the damage resistance increases with increasing modifier concentration by a successive reduction of the indentation depth. Once the impact causes large-scale fibre fracture (13 J), the damage mode changes and an increasing matrix toughness leads to a strong reduction of the damage area. However, a proper bonding between matrix and the embedded fibres is a mandatory precondition to take advantage of a core-shell rubber and block copolymer toughened matrix.

Accumulated wear degradation prediction of railway friction block considering the evolution of contact status

In this work, a simulation methodology with the combination of finite element modeling, Archard theory, and Arbitrary Lagrangian-Eulerian (ALE) technique is proposed for the accumulated wear degradation prediction of railway friction block. The validation is conducted with a test bench from the perspectives of tribological and dynamic behaviors during the running-in and formal testing processes. The friction pair comprises a forged steel brake disc and a Cu-based powder metallurgy friction block. The results indicate that the contact area increases during the running-in process and the average contact pressure decreases first and then fluctuates around a stable value. In the formal testing process, although the accumulated wear mass and the wear mass per cycle increase with the number of braking cycles, the increase rate of friction block wear mass decreases rapidly in the first few cycles and then decreases slowly. The prediction error of the proposed method for the accumulated wear mass is less than 5%. The research in this work is helpful to have a deep understanding of the wear degradation mechanism of friction block and can provide an effective method for the prediction of friction block wear degradation.

Analiza konstruktivnih rešenja elastičnih točkova lakih železničkih vozila - pravci razvoja i upotrebe sa gledišta vibroakustičnih performansi

The paper analyzes the constructive and usable characteristics of resilient wheels with rubber blocks and rubber "V" ring used on light railway vehicles in urban traffic conditions in order to reduce vibration and noise. These vibrations and noise have an impact on passenger comfort and create serious problems for buildings and residents near city transit lines. The sources of noise generated by train wheels due to their vibrations and possible ways of transmitting noise caused by wheel/rail interaction are stated. The paper examines and analyzes the results of previous research that have give contribution to a better understanding and adoption of the resilient wheel structure and rubber parameters in order to achieve the best noise and vibration reduction effects. Through the paper, it was found that resilient wheels can effectively reduce the rolling noise of wheel on the track by a value of 3[dB] and significantly reduce ground vibrations in a certain frequency range.

Prediction Methodology Which Represents Friction Properties of Rubber Block on Ice (Part 1)

Prediction Methodology Which Represents Friction Properties of Rubber Block on Ice (Part 1)

A Dynamic Modeling Method for the Bi-Directional Pneumatic Actuator Using Dynamic Equilibrium Equation

Dynamic modeling of soft pneumatic actuators are a challenging research field. In this paper, a dynamic modeling method used for a bi-directionaly soft pneumatic actuator with symmetrical chambers is proposed. In this dynamic model, the effect of uninflated rubber block on bending deformation is considered. The errors resulting from the proposed dynamic equilibrium equation are analyzed, and a compensation method for the dynamic equilibrium equation is proposed. The equation can be solved quickly after simplification. The results show that the proposed dynamic model can describe the motion process of the bi-directional pneumatic actuator effectively.

Contact mechanics between a holey rubber block and a rigid plane

When a rigid plane compresses a rubber block containing an array of holes, the adjacent holes collapse in orthogonal directions, depending on the compression level. To demonstrate the buckling tunability to the contact interface, we examined how the flexible hinge size between holes affects the contact responses by finite element analysis. We found that the apparent friction coefficient can drastically decrease with increased compression levels due to the local buckling, while a rubber block without holes maintains a constant friction coefficient. This tunability is reflected in the contact area decreasing at the compression level, changing the contact pressure profile. We also found that there exists a flexible hinge size to minimize the apparent friction coefficient. Our findings offer the possibility of designing tunable contact interfaces.

The effect of interface modifications combination of multiple friction blocks on truck brake squeal

In order to study the effect of interface modifications combination of multiple friction blocks on truck brake squeal, a field test is carried out in this study. In the test, the vibration acceleration and the noise signals of the truck braking system are collected. The test results show that the high frequency squeal noise during braking is resulted from the frictional vibration of the braking system. A simplified finite element model of the heavy truck braking system is stablished to investigate the effect of slotting and chamfering of friction block on brake squeal. The results of complex eigenvalue analysis indicate that the interface modifications have a great influence on truck brake squeal. A proper combination of slotting and chamfering of friction blocks is useful for the reduction of brake squeal tendency. This study can provide guidance for the design and optimization of silent braking system.

Study on Frictional Force between Lining Concrete and Rubber Blocks

This paper mainly studies the friction coefficient between lined concrete and rubber blocks, designs the Friction resistance test device, puts forward two different Shaw hardness rubber blocks in different environments, and carries out the experimental research, obtains the corresponding coefficient of friction results, and provides the parameters and basis for the development of the special enclosure for the research of the subject.

The Influence of Friction Blocks Connection Configuration on High-Speed Railway Brake Systems Performance

The influence of friction blocks connection configuration on the interfacial tribology behavior and FIVN (friction-induced vibration and noise) of the high-speed railway braking system is systematically investigated with a scaled brake test bench. The potential relationship among interface contact status, friction, wear, pressure distribution, thermal response, and vibration noise of the system is studied under dragging test conditions. The results indicate that the connection configuration of the friction blocks has a significant impact on systematic interfacial tribology behavior, thermal response, and vibration noise. A floating connection mode can suppress the vibration noise of the brake system. The interfacial thermal response and systematic vibration noise are quite relevant with the contact status, interfacial wear, and pressure distribution. The increase of interfacial wear will lead to an expansion of pressure concentration area and an aggravation of vibration noise. This research is helpful for further design optimization and noise reduction of the railway brake system.

Study on the Ice-Coated Brake Disc for EMUs Based on Force Coupling

Based on the abnormal wear of the brake disc of Electrical Multiple Units (EMUs), considering the ice-coated friction pair, the finite element (FE) models of the brake disc, the friction blocks and ice impurity were established in ANSYS to explore the stress characteristics of the brake disc. For the ice-coated model, it is found that the maximum equivalent stress is 956.75MPa under the condition of pad stress of 25kN and initial braking speed of 250 km/h. The value of the maximum stress on brake disc surface decreased by 400MPa while removing the ice impurity. The maximum Z-displacement on the ice-coated disc is nearly 4.7mm, and with the contact point farther away, the smaller the deformation will be. The overall trend of the equivalent stress and Z-displacement of the brake disc increases with the braking pressure increasing. Droplet-like frictional blocks can improve the maximum stress and Z-displacement of the disc. Therefore, it is suggested that droplet -like frictional blocks are used for the braking equipment. For improving abnormal wear of the brake disc in extremely cold and snow environment, the analysis provides important reference and theoretical basis for engineering.

<b>Development of Improved Wheel Friction Block with Integrated Flange Lubrication and Tread Adhesion Functions</b>

<b>Development of Improved Wheel Friction Block with Integrated Flange Lubrication and Tread Adhesion Functions</b>

The effect of the friction block installation direction on the tribological behavior and vibrational response of the high-speed train brake interface

In this study, to investigate the effect of the hexagon friction block installation direction on the surface tribology and friction-induced vibration and noise (FIVN), tribological tests were carried out on a self-manufactured high-speed train brake dynamometer under different installation directions. Accordingly, a finite element (FE) model with material parameters and boundary conditions coinciding with the test rig was used to conduct complex eigenvalue analysis (CEA), and the Archard wear formula was employed to simultaneously study the wear and vibration. The results demonstrate that the installation direction has little effect on the frequency and mode shape of unstable modes, but the FIVN intensity, the phase-space characteristics of the friction noise, and the damping ratio of the brake system are changed. The contact stress and wear are found to be mainly distributed in the leading edge and the inner area of the friction block, leading to the severe eccentric wear phenomenon, and the friction heat is mainly concentrated in this area and the inner region of the disc friction area. The degree of uneven wear of the block is found to vary with the change of its installation direction, which also causes differences in the amount of wear debris flowing in the brake interface and the damage to the interface. Under the joint action of wear debris, friction heat, and contact stress, the brake interfaces of the brake systems with different block installation directions are found to exhibit different tribological behaviors, which affects the intensity of FIVN and the phase-space characteristics of friction noise. Therefore, it is necessary to consider the influence of the block installation direction on the tribological and dynamic behaviors of the brake interface of high-speed trains when designing the brake pad, which can aid in the development of a brake pad with excellent interface tribological behavior and friendly FIVN characteristics.

Research and modeling of tire cornering characteristics considering tread wear based on UniTire model

In view of the complexity of tire structure and working conditions, tire models are often based on complete and accurate test data. In combined with the theory of tire dynamics, the empirical and semi-empirical tire models are built. In order to accurately measure the tire mechanical properties, it is necessary to strictly control the wear state of the tire tread during the tire test. But there is still a certain amount of wear, which does not guarantee the consistency of the data. In order to study the influence of wear on the mechanical properties of the tire, based on the tire footprint pressure distribution model and brush model theory, combined with the brush model theory and the rubber block shear stiffness deformation theory, the tire cornering stiffness model under different wear conditions is established. The footprint pressure distribution model is built based on the results of footprint test under different wear conditions. And combined the test result with different tread wear conditions and the theory of brush model, the tire brush model considering tread wear conditions is built. Based on the above theoretical model, the UniTire tire cornering slip model considering the tread wear state is established. To verify the accuracy of the model, the UniTire cornering slip model is obtained by using the cornering slip data in three tread wear states, and the tire mechanical properties of the other tread wear conditions are predicted. The error between the simulation results of the model and the experimental results is small, which effectively prove the predictive ability of UniTire cornering slip model considering tread wear. This study will help to improve the UniTire tire model and provide theoretical and technical support for the UniTire indoor and outdoor expansion applications.

A Neural Network Based Dynamic Control Method for Soft Pneumatic Actuator with Symmetrical Chambers

Dynamic modeling and control of the soft pneumatic actuators are challenging research. In this paper, a neural network based dynamic control method used for a soft pneumatic actuator with symmetrical chambers is proposed. The neural network is introduced to create the dynamic model for predicting the state of the actuator. In this dynamic model, the effect of the uninflated rubber block on bending deformation is considered. Both pressures of the actuator are used for predicting the state of the actuator during the bending motion. The controller is designed based on this dynamic model for trajectory tracking control. Three types of trajectory tracking control experiments are performed to validate the proposed method. The results show that the proposed control method can control the motion of the actuator and track the trajectory effectively.

Transient abrasion on a rubber sample due to highly dynamic contact conditions

Abrasive processes, primarily the local slip, are the dominant contributor to friction and wear of vehicle tires in service. The time history of forces accompanying acceleration, braking, and cornering in particular, lead constantly to changing contact conditions under the tire. Consequently, a laboratory test taking into account not only surface texture but also tire contact times (in the range of milliseconds) as well as realistic contact forces in a freely controllable temporal sequence is desirable. This paper presents the study of the dynamic contact between a rubber block and the abrasive surface at conditions close to those in a tire footprint. In our case, the test samples are a miniaturized tread block allowing to reproduce the intermittent tire contact including correct contact timings, pressure and friction coefficients in dependence on the driving maneuver to be tested. An analysis and comparison of friction and wear mechanisms for continuous contact and defined contact times is presented surpassing the characterization capabilities of DIN abrasion testers.Two different compounds with a variation of stiffness are examined. The grip and wear rates are analyzed and compared. It is shown that understanding the dominant mechanisms and quantifying tire tread friction and wear in detail require the consideration of realistic transient dynamics of a tire tread block impacting the road at each revolution of the tire.

Analysis of the influence of small quantity secondary lubricant on water lubrication

The use of water-lubricated bearings has increased dramatically in recent years because of environmental concerns. However, due to its low viscosity water generates easily broken lubrication film, which may cause wear and noises when water-lubricated bearings are subjected to short-time sever working conditions, e.g., low speeds and impact loads. A block-on-ring test rig is used in our work to simulate working conditions of water-lubricated bearings under the mixed lubrication regime and the coefficient of friction (COF) is monitored during the experiment. After the COF is stable between the rubber block and the stainless-steel ring lubricated by water, a small quantity of secondary lubricating medium (#5 white oil) is injected into the contact region. The COF decreases accordingly and its stable value is smaller than that under water-lubricated condition. The flow of water and #5 white oil, as well as the interaction between these two phases, are examined by CFD simulation. The results show that #5 white oil can break though the reverse water flow at the inlet and enter into the contact region to participate into the lubrication, and small oil droplets are formed during the injection, which are distributed throughout the contact area and stuck on the block and the ring to improve the lubrication performance. Therefore, the injected #5 white oil could enhance the film-forming ability of water, reduce the COF and improve the tribological behaviors of the water-lubricated contacts. Our work thus provides a new lubrication method to alleviate the friction and wear of water-lubricated bearings when subjected to short-time severe working conditions.

Enhancing brush tyre model accuracy through friction measurements

Accurate tyre models are important to ensure valid and reliable simulation of vehicle behaviour. To this purpose, the Magic Formula (MF) became the de facto standard for vehicle dynamics simulations, despite requiring many empirically derived coefficients. This paper shows how the accuracy of a simple physical-based brush-type tyre model can be enhanced to simulate tyre behaviour that closely matches MF results. To do so, the real, highly complex rubber friction characteristics are incorporated into the brush model. The friction characteristics were obtained from friction measurements with a tread rubber block. The developed model is validated against experimental tyre data obtained on a flat-track test rig and the corresponding MF model. Results show that the inclusion of friction characteristics allow accurate simulation of longitudinal and lateral slip conditions over a wide range of normal loads with the simple brush model. At extreme loading scenarios, the simulation accuracy deteriorates because of the significant influence of highly nonlinear deformation behaviour of the tyre that is not accounted for in the brush model formulation.

Rubber Wear and the Role of Transfer Films on Rubber Friction on Hard Rough Substrates

We study the influence of rubber transfer films on the sliding friction between rectangular rubber blocks and a concrete surface. We present experimental results for the friction coefficient for a rubber compound sliding on a concrete surface contaminated by another rubber compound, for two different pairs (A, B) and (C, D) of rubber compounds. For the same rubber compounds, we present theory results which illustrate the relative importance of the viscoelastic and adhesive contribution to the sliding friction. We correlate the calculated rubber friction with the nature of the observed transfer films (or wear processes).Graphical

Effect of Surface Modification on the Tribological Properties of Friction Blocks in High-Speed Train Brake Systems

Commercial high-speed train friction blocks with a hole in the middle of the surface and perforated blocks filled with additive materials are introduced in drag brake experiments conducted on a customized small-scaled braking dynamometer. These additive materials include Cu-based powder metallurgy material, composite material, and a Mn–Cu damping alloy. The results indicate that the filling materials significantly influence the wear behavior of a braking interface and the characteristics of friction-induced vibration. Under the same experimental conditions, the perforated blocks filled with different materials produce different types of wear debris and exhibit different wear evolutions, markedly changing the wear debris distribution and surface morphology. These changes lead to variations in thermal distribution on the surfaces of both the friction block and brake disc. The study also shows that as a filling material, the Mn–Cu damping alloy can suppress the friction-induced vibration of the brake system, resulting in the lowest level of brake noise among all brake systems. However, the original friction block (i.e., the block without any filling material) can trap wear debris because of its perforated structure. The structure produces less friction-induced vibration and noise, compared with the block filled with powder metallurgy material. The noise performance of the composite material block is superior to the noise performance of the block without any filling material (i.e., the original block) and the block with powder metallurgy material but inferior to that of the block filled with the Mn–Cu damping alloy. Finite element analysis indicates that the properties of the filling materials exert no effect on the unstable vibration intensity of the brake system. Therefore, the wear debris behavior of the filling materials and the interface wear characteristics influence the friction-induced vibration and noise of the brake system.

Examination of Stick-Slip motion analysis of rubber block by Discrete Element Method

Examination of Stick-Slip motion analysis of rubber block by Discrete Element Method