Rubber Pad Research Articles

The Use of Under Sleeper Pads to Improve the Performance of Rail Tracks

In recent years, with the growing demand for both passenger and freight mobility, faster and heavier rail traffic has been the norm rather than the exception in many countries. As a result, track geometry and the safety of ballasted rail tracks have been adversely affected, leading to exacerbated maintenance costs. Increased stresses in granular foundation induce progressive track degradation, which can result in excessive vertical and lateral deformation, ballast and subballast fouling and impeded drainage. These effects tend to be more severe at specific locations, such as bridges, level crossings and tunnels (i.e. over stiff subgrade). Finding an economical strategy to mitigate ballast degradation has been a challenging task for practitioners, and the inclusion of energy-absorbing rubber pads underneath the sleepers (under sleeper pads—USPs) to minimise track damage is an attractive solution. This paper presents a laboratory study conducted at the University of Wollongong to investigate the use of USPs as resilient elements in ballasted rail tracks involving a stiff subgrade. Test results have shown a significant improvement in track performance resulting from the use of USPs, whereby it is demonstrated that ballast damage induced by the applied cyclic loads can be reduced due to the favourable damping characteristics of these rubber pads. A significant attenuation in particle breakage was observed along with a reduction in both the vertical settlement and lateral movement of the ballast layer, thereby suggesting that USPs can be an effective means of improving the stability and serviceability of the track system.

Design and Development of a Cooler used for Air Cooling and Refrigeration

In this research paper we have discussed the utilization of a cooler for air cooling as well as refrigeration. The purpose of this paper is to design modification of the existing design of, in which a refrigeration box is made of mild steel is attached inside the cooler tank and this tank of cooler is insulated by rubber pad from outside to avoid any loss of heat. All the surfaces of the box are in contact with tank water except the front face which is door of a refrigeration box. The proposed model is experimentally validated by conducting a series of experiments in a controlled atmosphere inside a room in the climate of Raipur, Chhattisgarh, India. Box is loaded with fruits / vegetables and parallel to this, the same quantities of fruits / vegetables are kept outside in the room and daily weight loss is measured.

An Extensive Review on Advance Forming Methods

Giving it a shape and making it a useful component defines the process of forming. Years of research have given new methods to this process. In various industries like automobile and aeronautics, the goal is to achieve complicated shapes with properties like high energy absorption, high rigidity at a lower cost. These aspects can be achieved by Advance Forming Methods (AFM), major work is being done on the hydroforming process as this process provide shapes that otherwise require a greater number of processes. The idea of flexible forming is something where the efforts are reduced along with a number of trials by introducing rubber pads into the sheet metal forming process and the complexity of tool design automatically reduces. Other than these processes, the process of rapid prototyping which is incorporated in the laser forming process is being used in the fabrication of metallic components. The areas of work which is being done are to reduce the number of failures by optimizing the process parameters to achieve better results at a low cost

Study of Vertical Characteristics with Changes in Prepressure of Rubber Pad Used by High‐Speed EMU

Rubber spring plays an important role in improving train performance, so the study of rubber spring is one of the focuses of train dynamics. The vertical characteristic parameters of rubber spring are affected by prepressure significantly, as a result of varying parameters of static stiffness, dynamic stiffness, periodic energy consumption, damping coefficient, and so on. In order to use the theoretical method to calculate the precise static stiffness and predict the dynamic characteristics and to reduce the workload of the rubber spring performance test, this paper takes the annular rubber pad as an example to study with different prepressures. In this paper, the convexity coefficient correction formula (simply called the CCCF) for static stiffness calculation and the dynamic fiducial conversion coefficient (simply called the DFCC) method based on different prepressures are proposed. Through further analysis, the accuracy of CCCF and DFCC is proved both theoretically and experimentally. The results have shown precise prediction of the variation of prepressure on rubber spring parameters by using CCCF and DFCC and can be used as the reference of accurate vertical dynamic‐static characteristics of the rubber spring.

Seismic protection of unreinforced masonry buildings by means of low cost elastomeric isolation systems

Thousands of rural houses in developing countries with high seismicity were built without adequate seismic protection due to economical reason. This paper discusses a possibility to improve the seismic protection of typical unreinforced masonry in developing regions using low cost base isolation devices. The proposed isolation system involves fibre reinforced elastomeric isolators (FREIs) having small dimensions and few layers of rubber pads to reduce the fabrication cost. A series of 3D FE simulations are carried out to investigate the performances of the proposed FREIs utilised in the isolation of a one story masonry house prototype. The model is assumed subjected to several accelerograms to have an insight into the sensitivity of the isolation system against different earthquakes. The results reveal that the proposed low cost FREI system provides significant damage mitigation to the masonry house with good applicability of the FREI devices.

Probabilistic analysis of exterior hanging scaffold strength under impact load

Mega bridges require maintenance after long-term service. Exterior hanging scaffolds are widely employe to ensure that traffic is not disrupted during the construction. The working platform, composed of the light steel beam and wooden plane, is usually eccentrically hanged under the deck. Additional horizontal support fixed on the girder is needed to balance the huge moment, i.e. rubber pad or spring bearing. With the eccentric structure, the impact load is an important factor that affects scaffolding failure during the construction process. This study focused on the safety of typical exterior hanging scaffolds used in the rehabilitation of the Nanjing Yangtze River Bridge. First, on-site impact tests were carried out. The proposed regression model for the impact force history achieved satisfactory precision in comparison with the monitoring results. To carry out further probabilistic analysis, a numerical model of this scaffold was developed with the ABAQUS software, and was verified with the on-site monitored acceleration history under an impact load. Based on this model, the Latin hypercube sampling method was adopted to calculate the probability of the fall-induced impact stress in the scaffold. Additionally, a partial correlation coefficient was used to evaluate the sensitivity of the random parameters. In the random simulations, the location of the maximum stress was always close to the rubber pads regardless of the impact location. The variability in the maximum stress of the steel beams was smaller than that of the wooden plane. As the falling weight increased, the failure probability of the steel beams increased faster than that of the wooden plane. To this end, the key component in the exterior hanging scaffold moved from the wooden plane to the steel beams when the falling weight was larger than 200 kg.

A mechanism for overcoming the effects of the internal resonances of coil springs on vibration transmissibility

Internal resonances in suspension springs can result in significantly increased vibration transmission at the corresponding natural frequencies. Particularly for the case of metal coil springs used in vehicle suspensions, these internal resonances can be as low as 50 Hz and can lead to increased structure-borne noise in certain frequency bands. Although, in practice, this can be mitigated to some extent by using rubber pads in series with the coil springs, high vibration transmission in the vicinity of the internal resonance frequencies remains an important issue. In this paper, a mechanism is identified that can overcome the increased vibration transmission due to the internal resonances. This involves the use of a pivoted arm with a pivot bushing that is relatively stiff for translational motion. The quasi-static load is primarily carried by the suspension spring but the dynamic load at higher frequencies is also transmitted through the pivot bushing. By appropriate selection of parameters, in particular the moment of inertia of the pivoted arm and the stiffness of the pivot bushing, it can be arranged that the dynamic loads acting through the spring and the bushing largely cancel each other out at the spring natural frequency. It is shown that this mechanism is contained within common designs of railway vehicle primary suspension. Nevertheless, their design is largely based on their quasi-static behaviour and this principle of dynamic load cancellation has not previously been explained. The dynamic behaviour of different suspension arrangements is compared and the selection of suitable parameter values that can achieve this dynamic load cancellation is explained. Field measurements are also presented which confirm this behaviour.

Mechanical behaviour of the new pinned connection under out-of-plane horizontal load

The behaviour of the pinned connection under horizontal force in the out-of-plane direction is often neglected in engineering, causing failure of the lugs under such load. Adding annular laminated rubber pads in the pinned connection changes the uncertainty under the out-of-plane force. Numerical and experimental investigations are performed to research the mechanical behaviour of the connection. A finite-element model for the new pinned connection considering the contact interfaces and existence of rubber pads is established to understand yield mechanism, transmission pattern of load and the main factors affecting ultimate bearing capacity. Experiments are carried out to verify the accuracy of the finite-element model. The results show that the numerical study helps to detect the mechanical behaviour of the new connection under out-of-plane load with sufficient accuracy. The new connection has sufficient bearing capacity and stable deformation ability under horizontal load in the out-of-plane direction; meanwhile, friction and the stiffness of rubber pad were important factors affecting ultimate bearing capacity.

PENGARUH BANTALAN KARET TERHADAP MOMEN YANG TERJADI PADA LINK SLAB BETON

The use of link slab as a substitute for expansion joints is one of the innovations that can provide benefits for bridge life, user comfort, and maintenance cost efficiency. Link slab is a slab placed on the upper surface of the adjacent girder end which forms a continuous slab system with the slab deck. In the transition zone, link slab and girder are installed in hard rubber and soft rubber pads at some thick variations in each type of rubber. Moment on the link slab is obtained due to the effect of traffic load according to SNI 1725: 2016 with the condition of the link slab without and with rubber pads. The study of the use of link slab in this paper is carried out in a numerical approach on a finite element software-Abaqus. Link slab is modeled as a 3D solid model in compressive concrete variations. In this study, the addition of hard rubber pads on link slab can reduce the magnitude of moments compared to link slab without rubber pads. This is indicated by the percentage reduction moment between 39,20-83,42% on LS-1, LS-2, and LS-3 hard rubber pads with thichness 10 mm, 20 mm and 30 mm. While on link slab with soft rubber pads is found that moments are greater at the very thick pads This is indicated by the percentage difference in moments between 198,26 – 244,58% on LS-1, LS-2, and LS-3 soft rubber pads with thickness 10 mm, 20 mm and 30 mm. This large difference is due to the effect of moment change from negative moments (initial conditions) to positive moments after the addition of soft rubber pads.

Estimation and test assessment of the rail pads effect on the indicators of dynamic impact of the rolling stock on the track in the joint area

Increasing axial loads including the development of heavy movement on Russian railroads network require the best solutions for improvement of the railway track structure. Research by Russian and international scientists indicates that rail elastic pads reduce vibrations transferred from reinforced concrete sleepers to crashed stone, including the joint area. This study examines possibilities of using rail pads for reducing the dynamic effects of the rolling stock on the track in the joint area. Assessment of the rail pads construction material shock-absorbing properties was conducted considering the elastic properties of the rail support with static and dynamic loads. Results of mode ling the elastic properties of the rail support with rail pads of different rigidities using the software complex “Universal mechanism” are presented. The results were used as basis for calculation of indicators of dynamic interaction of the track and rolling stock at the joint using the coeffi cient establishing the link between bendings of the solid rail and the rail with joint. The expediency of using rail pads at the place of the joint is justifi ed based on assessment of the results.This study reveals that elastic rail pads based on isoprene rubbers are suitable for track structures that improve indicators of the track and rolling stock interaction. When using rubber pads, the growth of accelerations on the sleeper is less dependent on the speed, causing the track stability to increase. The results are supported by tests consistent with calculations and justify the necessity for further studies in this fi eld.

Cyclic Behavior of Wendelstein 7-X Magnet System During First Two Phases of Operation

The sophisticated large magnet system of the Wendelstein 7-X (W7-X) stellarator has been operated during first two experimental campaigns at the Max-Planck-Institute for Plasma Physics in Greifswald, Germany, for roughly 13 months. Its 70 superconducting coils (NbTi CCIC) are extraordinary not only due to complex 3D shapes of 50 non-planar coils, but also due to a non-linear support system. In addition, five big resistive coils with the aim to correct W7-X error fields are installed on the outer cryostat and use rubber pads in their supports to compensate thermal expansion of the coils. The structural behavior of the W7-X magnetic system is monitored and evaluated on the basis of the analysis of the signals from the extended set of mechanical and temperature sensors. Several cooldown/warming up and thousands of electromagnetic cycles with different loading patterns and with up to 70% design load magnitude have been performed by the system successfully. The focus of this paper is on the cyclic structural behavior of the W7-X magnet system and the comparison with finite element predictions. Several related issues such as bolts and rubber pads prestress degradation, support slippage development, evolution of mutual coil displacement, loading path dependence of stress levels, sliding weight support (cryoleg) adjustment, and sensor failure are addressed. Lessons learned so far are also briefly summarized.

Research of Different Processes for Forming Fiber Metal Laminates

The paper presents the results of forming rifts in five-layer fiber reinforced metal polymer laminates by electromagnetic forming. During the experimental studies the discharge energy of the electro-magnetic machine was varied in such a way as to achieve different depths of the rift. Samples obtained by electro-magnetic forming were compared with control samples obtained by forming using a rubber pad under static loading. The strain state of the samples was analyzed using an digital image correlation system Vic-3D. The experimental research of fiber reinforced metal laminates forming under the influence of pulse magnetic field has shown the possibility of formability increasing due to change of strain state: the rift zone is dominated by compressive circumferential strains, rather than tensile radial strains as during conventional rubber pad forming.

Finite element modeling and durability evaluation for rubber pad forming process

Elastomer (or rubber pad) forming is a dieless forming process. The forming process has several advantages compared to general press forming process in terms of tool cost and scratch problem. However, when the elastomer is subjected to severe deformation during forming process, it can result in an expensive cost for the replacements of elastomer. Therefore, it is necessary to evaluate accurate tool life. In this study, the FE analysis was conducted for the rubber pad forming process and the fatigue life evaluation of the elastomer tool was investigated numerically using the reference experimental data. For the FE analysis, uniaxial and equibiaxial tension tests of natural rubber 50 were carried out in order to obtain the mechanical material properties of the elastomer. The hyperelastic behavior of the elastomer was characterized using Ogden model. The elastomer forming process was modeled using a commercial software LS-DYNA 3D. Two important factors of FE modeling were to calibrate the simulation conditions and to obtain the target product shape with a preformed elastomer. With the result of FE analysis, a durability of the elastomer was conducted focusing on fatigue life, because the elastomer is applied for repeated loadings during the forming process. Unlike general fatigue analysis, the fatigue life of the elastomer is predicted with respect to the strain measures due to Mullins effect. Furthermore, the Polar Effective Plastic Strain (PEPS) diagram [6] considering the strain path changes was used to check the failure of the blank during the forming process.

Role of somatosensory and/or vestibular sensory information in subjective postural vertical in healthy adults

The body's subjective postural vertical (SPV) has been thought to be affected by somatosensory information. How the SPV is perceived based on what types of somatosensory information has not been determined experimentally by manipulating somatosensory conditions. We investigated the effects of disturbing the somatosensory information from a seat pad and/or vestibular sensory information on the SPV in 15 healthy adults. Their SPV values were measured under four conditions (control, somatosensory, vestibular, and somatosensory + vestibular) in random order. The average and absolute SPV values were measured. In the somatosensory condition, a foam rubber pad was placed on the seating surface and the subject's SPV was measured. In the vestibular condition, the SPV was measured during galvanic vestibular stimulation (GVS). The somatosensory + vestibular condition was used to measure the SPV during combined somatosensory and vestibular stimulation. The mean SPV value was significantly increased in the somatosensory + vestibular condition compared to the other three conditions. The absolute value of SPV was significantly increased in the somatosensory and somatosensory + vestibular conditions compared to the control and vestibular conditions. There was no significant difference in the average or absolute SPV values in the vestibular condition compared to the other conditions. There was no significant difference between SPV errors when somatosensory information was disturbed or when somatosensory + vestibular information was disturbed. When the somatosensory information from the seat was disturbed, the SPV error increased, and it also shifted under the influence of the vestibular sensory information modulation. These results indicate that somatosensory information from the seat plays an important role in SPV in healthy adults.

Research of the driven capacity of pushers with rubber pads for oil equipment

The paper discusses the choice of the optimal shape and dimensions of pushers with rubber pads for injection heads intended for pushing cables into an oil well. To optimize the size and shape of the pushers, the finite element method was used. The obtained results were checked experimentally on a specially designed stand. The results of experiments on the evaluation of a number of rubber compositions according to their tribological properties and tractive capacity are presented.

Design and Analysis of the US ITER Central Solenoid Module Lifting Fixture

The central solenoid (CS) consists of six large high field superconducting magnets (also known as modules) approximately 4 m in diameter and 2 m tall that weigh approximately 120 tonnes each. These large and complex modules create challenges during assembly of the CS that require the development of custom assembly tooling such as the CS lifting fixture. The CS module lifting fixture is designed to lift and stack the six CS modules in the assembly building on the ITER site. Because of its unique design, fabrication, and assembly features, no lifting attachments could be incorporated within or under the CS modules. This limitation motivated the development of a friction-based lift fixture. The design and evaluation of the CS module lifting fixture considered both worker safety and investment protection, and the assessments were performed to international codes and standards. The CS module lifting fixture consists of two principal subassemblies: spider assembly and ring weldment. These subassemblies allow the frictional force to be augmented by the mechanical advantage of shallow-angle wedges. Large radial preloads created by both screw jack assemblies and the weight of a CS module develop frictional forces capable of performing a lift with a safety factor of at least 2. The design effort resulted in the use of low friction linear bearings on angle surfaces to ensure constant pressure, integrated jacks for pretensioning the fixture prior to lifting, and load pin strain gauges for monitoring the normal force. Testing of various materials and surface treatments led to the selection of laminated aluminum and rubber pads as the friction interface on the CS lifting fixture side and a grit-blasted Nitronic 50 stainless steel band on the CS module side. A redundant lifting method using the module slings between the spider and module is also utilized after the initial friction lift. The CS lifting fixture provides a safe and reliable solution for lifting and stacking the CS module during assembly.

Matrix and reinforcement materials for low-cost building isolators: an overview of results from experimental tests and numerical simulations

During the last years several options to replace the conventional steel-reinforced isolators have been investigated using different materials for the matrix and reinforcement to implement isolation system in buildings. As alternatives to natural rubber, recycled elastomers derived from tires and industrial leftover, scrap tire rubber pads and nanocomposite rubber, have been proposed. Furthermore, with the goal of replacing the inflexible, thick steel plates, a wide variety of fabric reinforcements, such as nylon, carbon, polyester, polyamide, glass and thin flexible steel plates, have been investigated. The manufacturing process and connections between the devices and the structure (bonded, unbonded and partially bonded) have also been studied. This paper presents an overview of the results from investigations where the mechanical properties of prototypes were determined through horizontal shear and vertical compression tests and, in certain cases, through finite element analysis with hyperelastic models. In order to facilitate the visualization and comparison between investigations, the results are tabulated and plotted. The organization and presentation of the results allows to identify important aspects implemented in different experimental programs and analytical models developed for low-cost isolators.

Rubber Pad Sheet Metal Forming of Round Metal Blanks into Multi Shape Axisymmetric Cups by FEA and Experimental Methods

Rubber Pad Sheet Metal Forming of Round Metal Blanks into Multi Shape Axisymmetric Cups by FEA and Experimental Methods

Design Optimization of the Aeronautical Sheet Hydroforming Process Using the Taguchi Method

The aluminium alloy sheet forming processes forging in rubber pad and diaphragm presses (also known as hydroforming processes) are simple and economical processes adapted to aeronautical production. Typical defects of these processes are elastic recovery, necking, and wrinkling, and they present difficulties in control mainly due to property variations of the sheet material that take place during the process. In order to make these processes robust and unresponsive to material variations, a multiobjective optimization methodology based on the Taguchi method is proposed in the present study. The design of experiments and process simulation are combined in the methodology, using the nonlinear finite element method. The properties of sheet material are considered noise factors of the hydroforming process, the objective being to find a combination of the control factors that causes minimal defects to noise factors. The methodology was applied to an AA2024-T3 aluminium alloy sheet of 1 mm thickness stamping process in a diaphragm press. The results allowed us to establish the optimal pressure values, friction coefficient between sheet and block, and friction coefficient between sheet and rubber to reduce the elastic recovery variations and the minimal thickness before noise facts.

Generation mechanism and remedy method of rail corrugation at a sharp curved metro track with Vanguard fasteners

In Chinese metro lines, Vanguard fastener system is widely used as vibration damping fastener. However, the rails mounted with this fastener system are deeply affected by rail corrugation. The generation mechanism of corrugation wear at a metro track mounted with Vanguard fastening is revealed through the numerical simulation method. A finite element model including two rails, the track system, and a leading wheelset is set up. The parameter sensitivity analysis is conducted to identify the dominant factors affecting the rail corrugation. Then, the remedy method to suppress the corrugation wear is put forward on the basis of the parameter analysis results. The results indicate that the severe corrugation wear on the inner rail is attributed to the self-sustained vibration of the wheelset–track system aroused by the saturated wheel–rail creep force. The frequency of the rail corrugation calculated by the model is very close to the measured data. The elastic modulus and the damping coefficient of the rubber rest pad in the Vanguard fasteners have a high impact on rail corrugation. Increasing the elastic modulus and the damping coefficient can effectively restrain or even eliminate the rail corrugation. Bringing the damping coefficient of the rubber rest pad above 0.0001 can significantly alleviate the rail corrugation. The influence of the damping and stiffness of the rubber pad under the floating slab track bed is negligible.