Rubber Block Research Articles

Hydraulic investigation of stilling basins of the barrage before and after remodelling using FLOW-3D

Abstract The hydraulic performance of stilling basins is affected by their size and geometry. Taunsa Barrage, Pakistan, was constructed in 1958 and remodelled in 2008. In remodelling, baffle and friction blocks were replaced by chute blocks and dentated sill. After remodelling, sounding, and probing data during 2010–2014 revealed that flexible apron in front of some bays was washed away. This study quantified hydraulic parameters such as free surface, flow depth, Froude number, roller length, velocity, hydraulic jump efficiency, and turbulent kinetic energy for stilling basins before and after remodelling using FLOW-3D. Comparing results with the literature showed that results in the old stilling basin were closer to the literature results. The results of old stilling basin showed linear trends of tailwater depths with Froude number and roller lengths. Results of the new stilling basin deviated from the literature results because relatively weak trends of tailwater depths with the Froude number and roller lengths were revealed; velocities were higher on the basin's floor; energy dissipation was less, and there was more turbulent kinetic energy on downstream. In conclusion, hydraulic studies for other discharges, tailwater levels, and turbulence models have to be conducted to analyze hydraulic issues in the new stilling basin.

Rubber-ice friction

We study the friction when a rectangular tire tread rubber block is sliding on an ice surface at different temperatures ranging from −38 to −2 °C, and sliding speeds ranging from 3 µm/s to 1 cm/s. At low temperatures and low sliding speeds we propose that an important contribution to the friction force is due to slip between the ice surface and ice fragments attached to the rubber surface. At temperatures above −10 °C or for high enough sliding speeds, a thin premelted water film occurs on the ice surface and the contribution to the friction from shearing the area of real contact is small. In this case the dominant contribution to the friction force comes from viscoelastic deformations of the rubber by the ice asperities. We comment on the role of waxing on the friction between skis and snow (ice particles).

Friction-induced vibration and noise characteristics, and interface tribological behavior during high-speed train braking: The effect of the residual height of the brake pad friction block

A tribology test was carried out on a test device to simulate the braking performance of a high-speed train and investigate the effect of the friction block's residual height on friction-induced vibration and noise (FIVN) characteristics and interface tribology behavior. A finite element model (FEM) of the test device was established using the real boundary conditions and component material parameters. A wear simulation of the friction block was performed, and the Archard wear equation was used to obtain the surface wear of the friction block after stable friction had occurred. Complex eigenvalue analysis (CEA) and implicit dynamic analysis (IDA) were carried out. The effect of the friction block's height on the surface wear level, the complex mode and dynamic response, and the interface contact behavior are discussed. The results show that the friction block wears at an angle due to the friction force at the braking interface. Thus, the contact stress occurs predominantly at the leading edge of the friction block, leading to significant wear, high temperatures, and eccentric wear of the friction block. The taller the friction block, the larger the inclination angle is, and the more significant the eccentric wear degree is. Excessive wear at the leading edge causes debris to enter the brake interface. As a result, the wear surface of friction block is significantly damaged, including large contact plateaus and extensive exfoliation and ploughing. This damage increases the complexity of the braking interface's tribological behavior and causes high-intensity FIVN. However, the inclination angle decreases as the friction block's height decreases, resulting in better wear behavior of the friction interface and lower FIVN intensity. Although the friction block height significantly affects the intensity and evolution of FIVN, it does not change the system's inherent frequency.

Prediction Methodology Which Represents Friction Properties of Rubber Blocks on Ice (Part 2)

Prediction Methodology Which Represents Friction Properties of Rubber Blocks on Ice (Part 2)

The effect of wheel polygonal wear on temperature and vibration characteristics of a high-speed train braking system

To study the effect of wheel polygonal wear (WPW) on temperature and vibration behaviours of a high-speed train braking system, a rigid-flexible coupled vehicle system dynamics model and a thermo-mechanical coupled finite element (FE) model of a braking system are developed in this study. The accuracy of the vehicle dynamics model and FE model are verified by line and bench tests, respectively. The dynamic interactions between different vehicle components, and the nonlinear factors such as wheel − rail interactions, non-linear damper and disc − block frictions are comprehensively considered in the model, which is able to more realistically reflect the service environment of a vehicle system and accurately capture the vibration, temperature and disc − block contact status of a braking system during braking process. Based on the established models, the dynamic behaviours of the braking system excited by WPW is systematically investigated. The results indicate that the standard deviation (SD) of contact area, the root mean square (RMS) values of vibration and the temperature of friction block interface with WPW are much higher compared to those without WPW. Besides, the braking system experiences more intense vibration with the increment of WPW order.

The tangential view described by Moneim to demonstrate scapholunate dissociation: an update

PurposeScapholunate dissociation is a common and significant injury to the wrist. Radiographs are important in the diagnosis of this injury and in the planning of treatment. The tangential radiograph view was described almost 40 years ago as a method for accurately measuring scapholunate gaps. The hand is positioned on a 20° foam rubber block and the thumb on the cassette, which positions the scaphoid and lunate articular surfaces parallel, without patient discomfort or effort. The goal of this study was to review this method with more recent data and in a larger group of patients.MethodsRadiographs of 31 patients who had scapholunate interosseous ligament tears and surgical repair over a 9 year period were retrospectively evaluated. Each of the four authors independently measured scapholunate gaps for posteroanterior and tangential views.ResultsThe tangential view gaps were significantly greater than the posteroanterior gaps overall. Similar results were found for borderline cases where the posteroanterior gap was less than 3 mm. Every tangential view gap measurement was greater than its respective posteroanterior gap with good inter-rater reliability.ConclusionThe tangential view is a reliable radiographic method to identify scapholunate gaps. It should be obtained when there is clinical concern for scapholunate dissociation, especially in patients with borderline posteroanterior gaps.

Grating‐like anechoic layer for broadband underwater sound absorption

AbstractTo address the challenging task of effective sound absorption in the low and broad frequency band for underwater structures, we propose a novel grating‐like anechoic layer by filling rubber blocks and an air backing layer into metallic grating. The metallic gratings are incorporated into the anechoic layer as a skeleton for enhanced viscoelastic dissipation by promoting shear deformation between rubber and metal plates. The introduction of an air backing layer releases the bottom constraint of the rubber, thus intensifying its deformation under acoustic excitation. Based on the homogenization method and the transfer matrix method, a theoretical model is developed to evaluate the sound absorption performance of the proposed anechoic layer, which is validated against finite element simulation results. It is demonstrated that a sound absorption coefficient of the grating‐like anechoic layer of 0.8 can be achieved in the frequency range of 1294–10 000 Hz. Given the importance of sound absorption at varying frequencies, the weighted average method is subsequently used to comprehensively evaluate the performance of the anechoic layer. Then, with structural density taken into consideration, an integrated index is proposed to further evaluate the acoustic properties of the proposed anechoic layer. Finally, the backing conditions and the boundary conditions of finite‐size structures are discussed. The results provide helpful theoretical guidance for designing novel acoustic metamaterials with broadband low‐frequency underwater sound absorption.

Tribological improvement of a high-speed train brake system and friction-induced vibration energy harvesting via a sandwich damping piezoelectric structure

A sandwich damping piezoelectric structure (SDPS) was designed to improve the wear and friction, reduce the friction-induced vibration and noise (FIVN) of high-speed train brake system, and convert friction-induced vibration (FIV) energy into electrical energy. Tribological tests were carried out to investigate the effect of the SDPS on the tribological behavior and the conversion efficiency of FIV energy into electrical energy. The results show that the proposed SDPS can convert FIV energy into electrical energy due to deformation, and the perforated structure produces greater deformation and a higher output voltage. The SDPS installed in the braking system improves the contact and wear behavior of the friction block, which reduces the FIV intensity, and can transform FIV energy into electrical energy.

A new non-contact method for calculating deformation resistance of tire tread rubber material under rolling condition

Background70% energy consumption of automobile tyre comes from the energy consumption generated by the viscoelasticity of tread rubber.The non-contact calculation method of rolling resistance of tire tread rubber block is studied, and the relationship between rolling resistance and global strain is analyzed. Materials and methodsA non-contact test bench for mechanical property of rubber tread block is developed.Stress-strain relationship and full-field distribution characteristics are obtained by means of digital image correlation under the influence of load and velocity.A Fourier series model is proposed to describe the non-linear viscoelasticity of rubber material.The model parameters is identified by using non-linear least squares. On this basis, the rolling resistance and the rolling resistance coefficient are calculated. ResultsThe experimental results show that the nonlinear fitting error of Fourier series model is less than 3%.The rolling resistance coefficient of rubber tread decreases with the increase of speed and increases with the increase of wheel load.The low strain areas is distributed at the trailing edge of contact zone, but the high strain is distributed at the leading edge of contact zone. ConclusionA new method for calculating the rolling resistance of rubber materials is presented. The results show that the rolling resistance is positively correlated with the high strain distribution of tread under the influence of velocity. Under the influence of load, it is positively correlated with the transverse deformation of tread.

Hoisting-Rope Continuous Retracting and Releasing Device With Constant Locking Force and Small Impact

Background: With the continuous exploitation of shallow mineral resources, the shallow resources are increasingly exhausted. Therefore, the application of multi-rope friction machine in ultradeep, high speed, heavy load mine will be more widely used. The diameter and dead weight of the hoisting-rope in this heavy-duty deep well are larger, and the internal torsion and bending load are more complex, which makes the replacement of the hoisting rope more difficult. According to the "coal mine safety regulations", the working life of the hoisting-rope is not more than two years, and the hoistingrope of friction hoist is not more than eight months in a harsh environment. Although the existing hoisting- rope replacing methods are mature, there are some problems, such as high labor intensity, long replacement time and low safety, which affect the mine production and are not suitable for deep mine hoisting-rope replacement operation. Objective: The purpose of this patent is to provide a new mechanism for safely and efficiently replacing the hoisting-ropes of multi-rope friction hoists. In addition, the dynamic simulation analysis of the key parameters of the mechanism is carried out, and reasonable design suggestions are given. Methods: A new device is designed to achieve continuous retracting and releasing ropes with constant locking force and small impact, which is mainly composed of sprocket, chain, friction block, mechanism of clamping hoisting-rope and so on. Results: The designed new mechanism can efficiently and safely replace the hoisting-rope of various hoisting equipment and realize the continuous hoisting-rope replacement, limiting the load impact to a great extent. The mechanism is responsible for clamping and releasing the new hoisting-rope and retracting the old hoisting-rope during the whole hoisting-rope replacement process. In the condition of some hoisting-rope with large dead weight, it can also provide enough clamping force, and there will be no phenomenon of hoisting-rope sliding. Conslusion: The device not only realizes the synchronous replacement of the old and new hoistingrope, but also greatly improves the replacement efficiency and safety of the hoisting-rope. The patent effectively solves the existing problems in the process of hoisting-rope replacement and greatly improves work efficiency.

Experimental assessment for the thermal performance of scrap tire blocks as external wall insulators

In this article, the advantage of reusing scrap tires in scrap rubber block (SRB) to improve thermal insulation in buildings was examined experimentally. By testing the use of SRB in black and white colors as external wall insulators and comparing their performance with walls without insulation. The results indicated that a wall with scrap tire blocks gave the best thermal insulation results when the outer face was painted white. The decrement factor ( f $$ f $$ ) and the rate of heat loss increase, while the rate of heat gain decreases. This was done through the mechanisms of heat transfer by conduction through the layers of the wall and the effect of adding the rubber block on its thermal properties. The results showed that the use of rubber blocks reduces the temperature of the inner surface of the wall by 3–4°C lower than the traditional wall. The thermal diffusion inside the wall was determined effectively in the case of a wall with the rubber block, where the temperature of the inner surface reaches its maximum value by about 0.5-h difference from the traditional wall in the case of the wall with the rubber block in black color, and 9.5-h in the case with the white block.

Experimental study on the evolution of friction and wear behaviours of railway friction block during temperature rise under extreme braking conditions

The temperature-related evolution law of friction and wear behaviours of copper-based powder metallurgy friction block on forged steel brake disc under extreme braking conditions are studied. The results indicate that the friction and wear behaviours of the friction block have certain randomness with temperature rise, but the overall trend is definite. The friction coefficient at room temperature is 0.33, starts to rise when the temperature exceeds 170℃, reaches its maximum value of 0.43 at 240℃ and remains stable until 400℃. After that, the friction coefficient starts to decrease significantly. The wear rate starts to increase significantly when the temperature reaches about 100℃. When the temperature reaches 500℃, the wear rate increases by an order of magnitude compared with that at room temperature. When the temperature rises from room temperature to nearly 500℃, the wear mechanism gradually changes from abrasive wear to oxidative wear, and finally to adhesive wear.

Impact of rubber block end-face corner radius on the friction coefficient between rubber blocks and a glass plate under dry and lubrication conditions

The friction between a glass plate and rubber blocks with different end-face corner radii was investigated. Under dry conditions, rubber blocks with a large end-face corner radius (r = 0.83 mm) exhibited greater friction coefficients than those with a small end-face corner radius (r = 0.11 mm). Conversely, friction coefficients for r = 0.11 mm were greater than those for r = 0.83 mm under lubrication conditions. Further, the friction coefficients for r = 0.11 mm increased as the sliding velocity and lubricant viscosity increased owing to the formation of the fluid-free gap at the contact interface.

Simulation and Experimental Study on Abrasive Wear of Brake Discs

High-speed train brake discs are prone to abnormal wear in low temperature and heavy snow, which affects the safety of train operation. In this article, a staged braking strategy was proposed to improve the performance of train brake system in extremely cold climate by optimizing the relationship between operating speed and braking pressure. First, based on a brake bench test study, it was found that the average friction coefficient between the friction pairs increases significantly when the friction block holes were filled with quartz sand, and it was determined that the rigid particles introduced between the friction pairs at low temperatures are the direct cause of brake disc scratches. Then, a single abrasive wear model of the brake disc was established based on the Lagrangian finite-element method, and the damage characteristics of the brake disc under different braking modes were simulated and analyzed by the proposed model. The simulation results show that the braking mode with low speed and high pressure causes the most severe brake disc wear, which is consistent with the test results. According to the experiment and simulation results, the wear depth of the brake disc can be reduced by about 40% with the proposed staged braking strategy, which is of great significance to the safety of train operation in extremely cold weather.

Deep subdomain generalisation network for health monitoring of high-speed train brake pads

Uneven wear at different locations in high-speed train brake pads creates inconsistent vibrations, which make the criteria learned by the intelligent model hard to standardise to determine friction block failure. Variable friction-induced vibration makes brake pad health monitoring a cross-domain diagnostic problem. This study proposes a deep subdomain generalisation network for online monitoring of the health status of train brake pads. In contrast to existing transfer learning methods, the proposed approach does not assume the availability of test data during training. The model is generalised using unsupervised learning to new scenarios with unknown specific locations of uneven wear. The network reduces the discrepancy explicitly among the distributions of relevant source subdomains using local maximum mean discrepancy, which helps subdomains with identical labels more accurately find an appropriate common subspace. Furthermore, Bayesian optimisation is used to unify feature extraction, domain generalisation and hyper-parameter optimisation into a framework. The vibration–acceleration signals of different friction blocks are collected, and generalisation experiments are performed on both braking-friction and rotating-machinery datasets. The results indicate that the proposed model outperforms the other domain generalisation approaches and accurately identifies the state of a target friction block.

A Comparative Study on the Behavior of Ride Quality Due to Deflated State of Air Spring Using Different Properties of Hyperelastic Material

Elastomers are widely used in various engineering applications due to their huge elasticity and good dynamic behavior. One of the elastomeric elements is rubber blocks, which are used in many applications, such as vibration isolators, bumpers, shock absorbers, dampers, etc. In this research, the impact on the ride index due to the deflated state of the air spring with various kinds of hyperelastic materials is analyzed by the finite element method. The stress–energy function of rubber materials is first diagnosed, and Poisson’s ratio defined the volumetric terms. The rubber isolator’s stress is studied based on the finite element model, and the structure is improved. It is observed that for the deflated state of the air spring, laminated rubber isolation diminishes the muscular amount of structural responses compared to the conventional rubber base structures, and improves the ride comfort. This study would assist in doing finite element analysis of the secondary suspension system and other vibration-damping components.

Deep-subwavelength elastic metasurface with force-moment resonators for abnormally reflecting flexural waves

The elastic metasurface with compact design and easy fabrication has provided some insight into applications of solid wave-based field owing to its novel wavefront-shaping functionality; Yet, the deep-subwavelength design remains a challenge. In this research, we propose a new design of deep-subwavelength elastic metasurface (DEM) (1/49.5 of the incident wavelength), composed of gradient force-moment resonators, to abnormally reflect flexural waves. The force-moment resonator is implemented by stacking up a lead block atop silicone rubber block. The analytical solution of the reflection coefficient is obtained based on the transfer matrix method (TMM) to predict the phase shift (full 2π span) of the reflected flexural wave. Further, a theoretically simplified two degree-of-freedom (2DOF) mass-spring model considering the stretching and rotational resonance modes of the resonator and the dynamic stiffness method (DSM) to calculate the reflection coefficient are developed to reveal the deep-subwavelength physical mechanism. Both the analytical solution and the DSM have excellent consistency with the finite element (FE) simulation. By extending 2D force-moment resonators to 3D ones, the DEM is theoretically designed based on the generalized Snell's law (GSL). FE simulations and corresponding experiments well validate the abnormal reflection performance of the present DEM. The study shows that the DEM that does not damage and is easy to install on the host plate can be effectively used for flexural wave manipulation, which has potential applications in vibration control, wave absorption and energy harvesting.

An energetic approach to model the relationship between tire rolling friction and road surface macrotexture

To investigate the relationship between tire rolling friction and road surface texture, a model based on the energy dissipated by a rubber block when it is deformed cyclically by road surface asperities is proposed. The effects of speed and temperature are considered using time-temperature superposition and the Williams-Landel-Ferry equations. The model is applied to texture profiles, measured using a laser profilometer, and filtered to simulate the envelopment of road surfaces by a tire, to estimate the dissipated energy and deduce the coefficient of rolling friction. The comparison between the model and the experiments, obtained by measurements performed on road samples in the laboratory, shows a fair correlation between the predicted and measured coefficients of rolling friction, this depending on the type of surface studied. Discussions are made to explain the gap between the model and the experiments and identify perspectives for future investigations.

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.