Rubber Pad Research Articles

Seismic response of a model soil-pile-bridge system in cohesive soil

This paper investigates the dynamic response of a model pile-soil-bridge system subjected to seismic loading using a finite element model (FEM) developed in OpenSees. The numerical model is validated against shake table test data from a companion experimental study, which tested a piles-bridge model fabricated from organic glass. The bridge model comprised four piers, each supported by two-by-two pile groups, with edge piers featuring 60 × 60 mm rubber pads between the pier and deck. Two earthquake ground motions, El Centro and Tianjin, were applied at three intensity levels. The calculated and measured responses show good agreement. The validated FEM reveals that the El Centro earthquake typically induces higher acceleration and moment responses in structural elements compared to the Tianjin earthquake, while the Tianjin earthquake results in greater displacement responses. These findings highlight the impact of earthquake wave characteristics, such as predominant period, on the bridge system's response. Furthermore, the bending moments at the pier top for edge piers remain relatively consistent across different earthquake motions and intensity levels, indicating the role of rubber pads in mitigating seismic forces in the piers.

The influence of elastic pads deterioration in the fastening system on the dynamic characteristics of the vehicle-turnout system

The deterioration of the elastic pads in the fastening system in high-speed turnout areas increases longitudinal stiffness irregularities along the track, posing potential hazards to wheel-rail impact and train running safety. This paper takes the frog area of No. 18 turnout as an example and constructs a vehicle-turnout rigid-flexible coupling model considering the detailed structure of the fastener elastic pads. By increasing the stiffness of the rubber pad under the tie plate to simulate the deterioration of the elastic pads in the turnout area, the study investigates the effects of deterioration location, degree, and number on the dynamic characteristics of the vehicle-turnout system, providing theoretical guidance for stiffness optimization and maintenance of the turnout area. The results indicate that: 1) the deterioration of the elastic pads significantly affects wheel-rail interaction and safety indicators, while having a minor effect on vehicle running stability; 2) the 95th sleeper (point rail with a top width of 60 mm) is identified as the most critical location for the deterioration of elastic pads; 3) comprehensively considering, the stiffness replacement limit for elastic pads in ballastless turnout areas can be set to twice the design stiffness, which is 50 kN/mm.

Shaking Table Tests and Numerical Study on the Seismic Performance of Arc-Shaped Shear Keys in Highway Continuous-Girder Bridges

Typical forms of seismic damage to laminated-rubber-bearing girder bridges in the transverse direction are falling beams, girder displacement, and bearing damage. However, the damage to piers and foundations is generally lighter. This is mainly due to slippage of the bearings. Therefore, we propose a new type of arc-shaped shear key to improve the lateral seismic performance. A 1/12-scale highway continuous-girder bridge isolated by different shear keys was tested utilizing a 4 m × 4 m shaking table with six DOFs. The seismic responses of the bridge were analyzed in terms of phenomenon, displacement, strain, and acceleration. The main girder and pier exhibited different seismic responses because the bridge had different stops. A numerical simulation based on FEM showed that the established finite element model can well reproduce the displacement time history of the main girder and the cap girder. By analyzing the finite element model, the relative displacement of the bearing under different seismic waves was obtained. A comparison between the measured and FEM responses showed that the arc-shaped shear key can well limit the displacement of the main girder and the bearing. In addition, it does not significantly amplify the seismic response of the substructure. The arc-shaped shear key dissipates more energy while limiting the displacement of the main girder, and the comprehensive seismic performance is better than that of the rubber pad shear key.

Graphene nanoplatelets on recycled rubber: an experimental study of material properties and mechanical improvements.

This study presents an experimental investigation of the mechanical behaviour of recycled rubber pads coated with graphene nanoplatelets. The investigation is part of an effort to develop a novel rubber-based composite that aims to reroute rubber from end-of-life tyres from illegal landfills and incineration back into the market in the form of a novel composite for vibration isolation. Graphene nanoplatelets were deposited on rubber pads via ultrasonic spray coating. The pads were made of a combination of recycled rubber (from tyres) and virgin rubber. A comprehensive analysis of the structural and chemical properties of the graphene coating, ensuring its integrity on the rubber substrate, was performed by combining surface topography, Raman and Fourier-transform infrared (FTIR) spectroscopy. Stacked coated pads were cured and tested dynamically in compression and shear under cyclic loading. Results showed promising improvements in the mechanical properties, in particular, in compressive stiffness and damping of the coated specimens with respect to their uncoated counterparts, laying the foundation for using graphene-enhanced recycled rubber as a novel composite.This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

Development of Power Operated Garlic Peeler

Garlic bulbs are highly valued for their flavor and hold significant commercial importance due to their extensive medicinal properties and applications in food and pharmaceutical preparations. One of the essential preliminary steps before any subsequent processing activity is garlic peeling. Traditional methods such as hand peeling, flame peeling, oven peeling, and chemical peeling are commonly used in processing industries, large restaurants, hotels, and kitchens. However, these methods are laborious, time-consuming, cost-intensive, and limit the speed of processing activities. Due to its unique shape, mechanical peeling of garlic has not yet been effectively addressed by process engineers. Additionally, this task requires special care and skill to minimize material damage. With this in mind, a study was conducted to develop a power-operated garlic peeler aimed at alleviating the issues associated with traditional peeling methods and enhancing the processing and export of garlic and its products. The developed garlic peeler features a feed hopper, rubber pad, concave mechanism, and power transmission system. Its performance was evaluated at various combinations of shaft speed, feed rate mechanism, and operating speed. Based on the results, optimal values for the study variables were recommended for the prototype garlic peeler, considering peeling efficiency and the yield of peeled and unpeeled garlic cloves. The performance of the prototype garlic peeler with the recommended specifications was then evaluated. The developed garlic peeler achieved an effective peeling efficiency of 71.93%, with a minimal percentage of damaged garlic at a speed of 850 rpm and an operating time of 80 seconds, with a capacity of 2.88 kg/hr at 850 rpm. Additionally, it was observed that the cost of operation for the developed garlic peeler was Rs. 1.89 per hour to peel 1 kg of garlic, which is lower than the cost associated with hand peeling.

Test-retest reliability of postural sway on foam and natural rubber pads in healthy adults

Test-retest reliability of postural sway on foam and natural rubber pads in healthy adults

Shake table tests on a rigid block isolated with high-damping unbonded fiber-reinforced elastomeric isolators

Fiber-reinforced elastomeric isolators (FREIs) represent a relatively recent type of elastomeric device. In contrast to traditional steel-reinforced elastomeric isolators (SREIs), FREIs are constructed with multiple layers of rubber pads and fiber layers instead of steel laminas. This choice is aimed at cost reduction during the manufacturing and installation process. To enhance cost-efficiency, FREIs can also be used in unbonded applications (UFREIs), where the device is placed between the foundation and the superstructure without bonding or fastening. This approach helps to further minimize installation expenses. Furthermore, the lateral rollover deformation, a characteristic feature of this configuration, improves energy dissipation. This study investigates the seismic isolation capabilities of high-damping unbonded FREIs for low-rise masonry buildings. Specifically, unidirectional cyclic and shake table tests of a rigid block isolated with two UFREIs are discussed. The primary goals of this experimental study include evaluating the effectiveness of UFREIs in reducing seismic demands, analyzing the response of UFREIs under unidirectional ground-motion excitation, confirming the ability of UFREIs to withstand major unidirectional excitation without sustaining damage, and exploring the limitations of this isolation system under a range of seismic inputs and low axial loads.

Protection of Reinforced Concrete Columns from Pounding-Induced Effects in Adjacent Buildings

The pounding damage is one of the most common seismic damages observed after past earthquakes in adjacent reinforced concrete (RC) buildings having insufficient gap in-between. Particularly in highly populated regions, there are numerous adjacent RC buildings, in which pounding can cause severe damage or total collapse. Many previous reconnaissance reports following earthquakes have emphasized severe column damage due to pounding with the slab of adjacent building. In this paper, a retrofitting method is presented to reduce the seismic damage caused by pounding on existing RC structural elements in cases where collision is unavoidable. Pounding effects are investigated by using 4- and 7-story RC buildings with unequal floor elevations. As a retrofitting solution for pounding, steel columns and neoprene rubber pads are placed at the mid-height of the story so that the pounding takes place between the neighboring slab and added steel columns instead of existing RC columns. The mid-column pounding of existing RC buildings with and without retrofitting are numerically investigated. In the numerical model, buildings are connected by link elements to reproduce the pounding in-between. Nonlinear response history analyses are performed using 11 different real ground-motion records. Pounding forces, peak floor accelerations, inter-story drift ratios, story shear force distributions, and plastic hinge distributions are obtained and compared for each of the pounding conditions. The analysis results revealed that the proposed retrofitting method protects the existing RC columns from brittle type of shear failure and reduces the destructive effects of pounding.

Experimental Study on the Boundary Reflection Effect of Stress Wave Propagation Based on the Newly Developed Test Apparatus

There is a ubiquitous boundary reflection effect of stress wave propagation in the indoor experimental studies. It is critical to improve the validity of waveform data by optimizing boundary materials to absorb reflection waves. In the present study, a calculation method for the optimal wave impedance of boundary materials was proposed based on the transmission and reflection principle of one-dimensional stress waves at the interface of different media. By using the calculation method, the optimal wave impedance value of the boundary material was obtained. A one-dimensional stress wave propagation test apparatus was developed for exploring the improvement effect of absorbing materials on the boundary reflection effect. One-dimensional stress wave propagation experimental studies in the complete red sandstone samples were carried out by setting various boundary absorbing materials such as pine pad, rubber pad, and steel pad. The results indicated that the experimental test results were consistent with the theoretical calculation results. In the stress wave propagation tests, the optimal wave impedance value of the boundary material was 1.12 × 106 kg/m2·s. When the pine pads were used as boundary absorbing materials, the suppression effect of boundary reflection effects is relatively the best. The present study provides references for analyzing the characteristics and mechanism of stress wave propagation and attenuation.

Experimental Study on the Cyclic Performance of Novel Seismic Base Isolators Made by Scrap Tire Rubber Pads

Experimental Study on the Cyclic Performance of Novel Seismic Base Isolators Made by Scrap Tire Rubber Pads

A New Design of Vibration Damping Structure for Positive Displacement Motor

Positive displacement motor (PDM) is a downhole power drilling tool, and the bottom of the drilling tool is directly connected to the drill bit. During the drilling process, the drilling tool will be directly affected by the impact load caused by the drill bit breaking the rock. Severe vibration can easily cause drill tool bearings to break and fail, threads to trip and other problems. The new PDM vibration damping structure uses wear-resistant and heat-resistant metal rubber instead of disc springs as energy-absorbing materials, and designs a "keyway type" vibration damping structure; a two-degree-of-freedom "spring - mass" model is established based on actual working conditions. , determine the basic size of the metal rubber pad based on the metal rubber stress-strain curve, and bring it into the drilling tool dynamics equation to verify that the stiffness and damping parameters of the metal rubber pad will not resonate; finally, compare the drilling conditions under different excitations in the dynamics simulation software The amount of impact the tool receives. Finally, the dynamics simulation of the new vibration-damping drilling tool under different frequency excitations was carried out in Adams simulation software, and it was concluded that in the common working environment of 6-15 Hz, the new vibration-damping drilling tool can effectively reduce the stress on the drilling tool. Impact force, the new vibration-damping drilling tool can reduce the impact force by about 40% when excited at 12 , 15 Hz . The conclusions drawn from the study have reference value for the development of long-life drilling tools and the design of drilling tool vibration damping structures.

Influence of environmentally friendly curing system on properties of railway rubber pad

AbstractImproving the aging resistance and elasticity of rubber materials can increase the service life of rubber pads and reduce railway operation costs. The purpose of this work was to improve aging resistance, decrease compression set and ratio of dynamic stiffness to static stiffness (Rd/s) of railway rubber pads by using environmentally friendly accelerators N‐t‐butyl‐2‐benzothiazole sulfenimide (TBSI) and tetrabenzylthiuram disulfide (TBzTD). The influence of the curing system on the properties of rubber pads was assessed using multiple techniques. Compared to sulfur/tetramethylthiuram disulfide (TMTD) /N‐cyclohexyl‐2‐benzothiazole sulfenamide (CZ), compression set of S/TBSI/TBZTD decreased to 29.5% from 35.7%, retention of elongation at break after hot air aging increased to 77.7% from 66.1%, and Rd/s decreased to 1.82 from 1.85. Thermogravimetry (TG) and derivative thermogravimetry (DTG) analysis indicated that maximum thermal decomposition temperature of TBSI/TBZTD was higher, which was the reason for the good aging resistance and low compression set results. Rubber processing analysis (RPA) demonstrated that the loss factor of TBSI/TBZTD was smaller. The rubber cured by TBSI/TBZTD had a higher crosslinking density and smaller loss factor, which decreased the Rd/s. This study provides a reference for preparing of environmentally friendly rubber pads with a low Rd/s and long service life.

Elastic acupuncture needle: a set of one-piece elastic double-blind placebo acupuncture.

The Elastic acupuncture needle, a set of clinical device used in randomized controlled trials of acupuncture is developed, which may potentially obtain the double-blind placebo control. This kind of acupuncture device consists of a real needle and a sham one (placebo needle) with a identical appearance. Either of the needle is composed of an integrated cap-type handle and needle body, and a sterile double-sided adhesive pad is designed on the bottom for fixation. A spring with miniature low profile is built in sham needle. During operation, the real needle can be normally inserted, while the sham one be retracted because of the elasticity generated by the pressure on the skin, but deqi can still be felt by patients whenever the force difference between the skin and the spring reaches a certain balance. The rubber pad designed in this acupuncture needle can simulate the "resistance" felt by operators during needle insertion so that the double blinding is actualized in terms of the appearance and sensations.

Characterization and prediction of micro channel depth of ultra-thin bipolar plates for PEMFCs

In this study, a combination of experimental and statistical methods were employed to precisely determine the micro channel depth in ultra-thin metallic bipolar plates fabricated from 316 stainless steel with a thickness of 0.1 mm. The investigation centers on the rubber pad forming process and its role in the production of these critical components for Proton Exchange Membrane Fuel Cells (PEMFCs). To advance the understanding of this manufacturing process, experimental tests were designed using a Design of Experiment (DOE) technique and subsequently developed a predictive model using Response Surface Methodology (RSM). The research reveals a direct, quantifiable relationship between the channel depth in metallic bipolar plates and the magnitude of the applied force. Also, the pivotal role of rubber thickness as a dominant factor influencing channel depth was explored. Furthermore, it is revealed that augmenting the channel depth in these plates is attainable through a reduction in rubber hardness and an increase in rubber thickness. However, the benefits diminish once the rubber layer thickness exceeds a specific threshold. Moreover, the results underscore that the primary influential factors in this process include force, hardness, thickness, as well as the interplay between force and rubber thickness. The proposed model's accuracy is reaffirmed through an average error rate of approximately 5.39%, signifying its reliability in predicting microchannel depth. This research contributes novel insights into the manufacturing of ultra-thin metallic bipolar plates for PEMFCs, shedding light on the critical parameters influencing channel depth and their interrelationships. The significance and engineering value of this work lies in its potential for enhancing the design and manufacturing of metallic bipolar plates for PEMFCs. Precise control of microchannel dimensions is crucial for enhancing PEMFC performance and efficiency. This research not only advances clean energy technology but also contributes to the broader goal of achieving sustainable energy solutions, making it a noteworthy and timely contribution to the field.

Spatial temperature characteristics of CRTS III slab track of railways on plateaus

With the construction of railways on plateaus, the slab tracks of railways are facing rigorous temperature challenges and adverse thermal effects. This paper analyzed the temperature field and thermal effects of the CRTS III slab track on plateaus. Firstly, the pivotal thermal parameters of the geotextile and rubber pad of the slab track were obtained by tests. Subsequently, a coupled thermal-fluid-solid model for the CRTS III slab track on plateaus was established, followed by experimental validation. Based on the model, the temperature field and thermal effects of the slab track on Tibetan Plateau were revealed. The main conclusions are as follows: the thermal conductivity, specific heat capacity, and heat flux of the rubber pad and geotextile were very small, resulting in poor heat conductivity. The temperature of the track on plateaus showed obvious non-uniformity along both lateral and vertical directions, and changed with time significantly. Compared with that on the plain, the CRTS III slab track on the plateau had low temperature and large temperature variations. Compared with the conventional simplified temperature load, the spatial temperature field can fully reflect the non-uniform thermal effects of the slab track on plateaus. The method and conclusions presented in this paper can provide scientific guidance for the construction, operation, and maintenance of railways on plateaus.

High-damping fiber-reinforced elastomeric seismic isolator in different boundary conditions: An experimental insight

Seismic isolation reduces structural vulnerability and is an effective retrofitting solution. The commonly used steel-reinforced elastomeric isolators (SREIs) consist of several rubber pads interspersed with steel laminas for vertical reinforcement. However, SREIs are expensive, making them economically-unjustified for ordinary residential buildings, especially in developing countries. Fiber-reinforced elastomeric isolators (FREIs) offer a lighter alternative with thin fiber layers instead of steel laminas. FREIs can be applied to the structure in bonded (traditional), unbonded, or partially bonded configurations. Unbonded FREIs (UFREIs) are cost-effective as they are not bonded or fastened to thick connection steel plates. Furthermore, they are inherently more flexible in lateral directions and thus require relatively less rubber material to offer the same seismic isolation performance as traditional elastomeric isolators. However, UFREIs cannot resist tensile forces and may slip under certain loads, limiting their use in situations with overturning or high vertical accelerations. To address these limitations, partially bonded applications (PBFREIs) bond only a reduced area of the rubber device to the connection steel plates. PBFREIs retain beneficial characteristics of both unbonded and bonded applications, such as improved lateral flexibility, and resistance to uplift forces and slip. The possibility of UFREI applications remains promising, particularly in developing countries, due to their low cost, ease of fabrication and installation. This paper proposes a FREI made of high-damping rubber and glass fiber fabrics, and examines its performance in bonded, partially bonded, and unbonded applications. As a unique feature, the material and geometrical characteristics of the FREIs are identical. A comparative analysis, including experimental testing, highlights the strengths and weaknesses of each application typology. The paper also provides a detailed explanation of the design process, encompassing rubber compound development, fabrication, and experimental characterization of the device.

The protective performance of rubber pads for penetration fuze

To ensure the reliable functioning of hard target-penetration fuze on the battlefield, this study focuses on research related to fuze protective pads. The main factors causing fuze functional failure are summarized, and a simplified model of projectile penetration into target plates is established. The design conditions for the yield stress parameter of the fuze casing material are derived based on stress wave propagation theory. Modal analysis of the projectile is conducted using dynamic simulation software ANSYS to determine its vibration modes and low-pass filtering frequency. Static compression experiments are performed on different rubber materials (nitrile rubber, fluorine rubber, silicone rubber, and natural rubber) to obtain stress–strain curves and constitutive model parameters. Marshall hammer tests were carried out on rubber pads of different materials and thicknesses, confirming the validity of the simulation results and the feasibility of rubber filtering. The study indicates that when using a 2 mm thick rubber pad for protection, natural rubber provides the best protection. When using a 6 mm thick rubber pad, nitrile rubber shows the best protective performance. Under a 13-tooth tooling impact load, the best protection is achieved using a 2 mm thick natural rubber pad. When using a 6 mm thick pad, silicone rubber provides the best protection. Under a 15-tooth tooling impact load, fluorine rubber provides the best protection when using a 2 mm thick pad, while silicone rubber offers the best protection when using a 6 mm thick pad. Under a 17-tooth tooling impact load, natural rubber offers the best protection when using a 2 mm thick pad, and fluorine rubber demonstrates the best protection when using a 6 mm thick pad. The obtained research results provide a reference for protective methods of hard target-penetration fuze.

Real-time temperature field and thermal deformation of slab track on cable-stayed bridge

This study aimed to master the real-time temperature fields of slab tracks on cable-stayed bridges and analyze the thermal deformations. The pivotal heat conduction parameters of the geotextile and rubber pad were obtained through testing, and the governing equations for heat conduction considering temperature variations were improved. A thermal-fluid-solid coupling model for slab track on cable-stayed bridge was proposed. The results indicated that the high temperatures of the track were concentrated within 0.05 m depth of the slab. Under the resistance of the isolation layer, the temperature on both sides of the geotextile isolation layer appeared obvious abrupt change. The time of maximum and minimum temperatures of the truss beam were the same as those of the air. The effects of real-time temperature change on the irregularity of the rail were obvious. In summer, the maximum vertical rail deformation was 201.88 mm and the transverse deformation was 17.87 mm. The temperature change in just one day caused vertical deformation of rail with a range of more than 60%. On a single day in summer, the maximum horizontal irregularity was 1.74 mm, which was less than the 2.0 mm specified in the code.

Experimental investigation of three-body wear for rubber seals in abrasive slurry environment

Three-body wear is a complex phenomenon occurring when abrasive particles present between two material surfaces. By developing a new experimental setup, we systematically study wear at the contact between stainless steel and three different rubbers (TPU, NBR and LSR) in a slurry environment, i.e. water containing sand particles. Results showed that wear on both metal and rubber pads increases exponentially with the sliding speed, while a weak correlation was observed with the applied normal load for the given range of load. Wear analysis showed that the stainless steel experienced the most wear when in contact with NBR and the least when in contact with LSR. The TPU rubber pads experienced the most wear, whereas the LSR pads barely exhibit any wear when in contact with the stainless steel. Furthermore, frictional measurements indicated an inverse relationship between the system coefficient of friction and the amount of wear observed on the rubber elements. These observations are discussed in terms of the probability of the sand particles being clung to the rubber pads, after which they abrade the steel surface. This probability is justified as a function of the rubber material properties and the system friction coefficient. The findings in this study suggest new directions for minimizing three-body wear at the contact between metals and rubbers.

Reliability analysis based on load spectrum: A structural improvement of Indian Railways three-piece freight bogie elastomeric pad

Dynamic characteristics and reliability of elastomeric pads are dominant components in the design methodology to satisfy the performance parameters under dynamic operations. The fatigue life of rubber pads fitted with elastomeric pads mainly depends upon elastomers; natural rubber, chloroprene, nitrile butadiene, silicon compounds, etc., additives, accelerators, activators, fillers, anti-degradants, and manufacturing processes. The performance of the elastomeric pad is evaluated based on service operation, simulation, and laboratory testing. New and failed elastomeric (EM) pads have been examined in the Indian Rubber Manufacturer’s Research Association IRMRA laboratory for detailed failure analysis of existing EM pads. Further, chemical and physical properties are also evaluated in M&C (Metallurgical and Chemical) and Testing Directorate of Research Designs and Standards Organization (RDSO), labs respectively. The fatigue life of the EM pad is estimated based on the results extracted from the Finite Element (FE) analysis of the EM pad. An attempt is made to modify the design of the EM pad by considering the results of detailed field trials, lab testing, and FE analysis. The modified design satisfies the dynamic characteristic during FE (Structural and Thermal) analysis and lab testing.