Traditional Rubber Research Articles

Seismic performance of buildings with novel self‐centering base isolation system for earthquake resilience

AbstractThis study presents a novel self‐centering (SC) base isolation system enabled by traditional lead rubber bearing (LRB) incorporating superelastic shape memory alloy (SMA) U‐shaped dampers (hereinafter referred to as SMA‐LRB). This system is particularly suitable for some important structures (e.g., hospital buildings) that require high seismic performance and rapid recovery of normal serviceability after a severe earthquake. The working mechanism of the SMA‐LRBs is first illustrated, followed by a comparative experimental study on the traditional LRB and the emerging SMA‐LRB. Test results confirm the satisfactory flag‐shaped hysteresis loops of SMA‐LRB associated with significantly reduced residual deformation under cyclic loading. Subsequently, a refined numerical modeling strategy for these bearings is developed. The seismic performances of the SMA‐LRBs are examined systematically through two comparative reinforced concrete (RC) frame buildings, namely, the traditionally isolated and the SC isolated cases under far‐ and near‐field earthquakes. Seismic fragility analyses are further carried out through incremental dynamic analysis (IDA). The seismic responses demonstrate that the SC isolated building can match or improve the behavior of the traditional isolated buildings. Compared with the considerable residual deformation of the traditional isolated system under some earthquake events, the SC isolated system exhibits negligible residual deformation that can significantly avoid normal serviceability disruption while achieving the high‐performance objectives. The SC base isolation system can provide a promising type of advanced seismic protection device for earthquake resilient design.

Pyridine terminated polyurethane dendrimer/chlorinated butyl rubber nanocomposites with excellent mechanical and damping properties

Due to the special viscoelastic property, traditional rubber with high performance has been widely used in human life and production. However, it is challenging to improve the damping property without sacrificing the extensibility. In this work, a novel type of second-generation polyurethane dendrimer terminated with pyridine (G2-Py) was synthesized by using thiolactone chemistry and subsequently complexed with Zn ions. The structure and morphology of G2-Py were characterized. G2-Py-Zn2+ was then mixed with chlorinated butyl rubber (CIIR) by a two-roll mill. A series of CIIR/G2-Py-Zn2+ elastomers were obtained through vulcanization. CIIR/G2-Py-Zn2+ elastomers could achieve high stretchability (a strain of ∼1035%), high mechanical strength (a tensile stress of 7.64 MPa). This was benefitted from the friction between G2-Py and CIIR as well as variety of non-covalent bonds provided by G2-Py-Zn2+, which can dissipate energy to further improve the strength and extensibility. The coordination of Zn2+-pyridine was confirmed by Fourier transform infrared spectroscopy, stress relaxation and cycle tensile test. To further investigate the morphology and damping properties of the elastomers, scanning electron microscopy and dynamic mechanical analysis were performed. CIIR-5 showed the best damping performance with higher tanδmax and wider effective damping temperatures. Therefore, this dendrimer modification technology provides wider applications for CIIR elastomers in daily life.

Implementation of effective distribution channels in the marketing of traditional rubber plantation in Tambang District, Kampar Regency, Riau

Rubber marketing carried out by rubber farmers still involves several related institutions or does not sell rubber directly to factories so it provides several marketing channels for rubber in Tambang District. Factors which influence marketing channels are market considerations, product considerations, producer considerations and retail considerations. This research is expected to answer the channel research objectives and the factors that influence rubber marketing channels by using quantitative research methods, namely research that emphasizes analysis of numerical data (numbers) processed with statistical methods that can produce research results for each variable. The method of data collection is done by questionnaire, interview and observation. Based on the results of the study, there are four rubber marketing channels in Tambang District, namely marketing Channel I (farmer-trader-factory collector) of 42,19%. Marketing channel II (farmer, trader, wholesaler, factory) amount to 23,44%. Marketing channel III (farmer-trader-factory) of 26,56%. Marketing channel IV (farmer-farmer group-wholesaler-factory) by 7,81%. The results of the study of market considerations and producer judgment indicators are not good while the indicators of product valuation and considerations are good. The marketing channels in rubber marketing in Tambang District are in the unfavourable category with a total score of 1.112 and with a percentage of 48,23% from 64 respondents.

Annual soil loss assessment of smallholder rubber growing lands in the Kalutara District, Sri Lanka using the RUSLE model in GIS

Soil loss resulting from various land management practices in traditional rubber-growing areas of Sri Lanka has been a major issue of concern and one of the factors responsible for declining rubber land productivity. There is no or limited information on the spatial variability of soil loss from rubber lands in Sri Lanka's traditional rubber growing areas. This constraint has had a significant impact on the effective management of soil conservation in rubber-growing lands. This study focuses on assessing the soil loss from the smallholder rubber-growing lands in the Kalutara District using remotely sensed satellite image-based Digital Elevation Model (DEM), rainfall grid data, and prepared soil maps with ground-level surveys by Natural Resource Management Centre (NRMC) Sri Lanka. The factors including rainfall, topography, land area and the crop-specific coefficient for the rubber-growing lands in the study area were analyzed using the Revised Universal Soil Loss Equation (RUSLE) and Geographic Information System (GIS). The study revealed that about 30% of smallholder rubber-growing lands fall under the risk to severe risk categories of soil loss while about 60% of rubber lands are under the low-risk category. About 8,500 ha of smallholder rubber lands can be categorized as risk to severe risk for soil loss whilst about 15,000 ha are under the low-risk category for soil loss. The findings of this study are useful in the implementation of an effective soil conservation management plan and has the potential in applying this methodological approach in other areas of Sri Lanka for various crops.

Research on seismic performance of new bridge pier seismic reduction isolation system based on shaking table test

In view of the current poor seismic performance of bridges, this paper started with the vibration isolation and reduction mechanism of the bearing, and deduced the coordination relationship between the stress and the deformation of the bearing under the vibration isolation and vibration reduction working conditions. Combined with the shaking table test, the defect that the traditional rubber bearing has poor seismic isolation effect was analyzed. Based on this, a base-bearing double reduction system was proposed and its vibration reduction and isolation effect was compared with the traditional bearing. The shaking table test results showed that, compared with the traditional bearing, the proposed vibration reduction system had better energy dissipation effect and could weaken the apparent cracking damage of the pier under the action of earthquake. Under the 125 m/s2-750 m/s2 peak acceleration excitation of the EI-Centro wave, the proposed vibration reduction system could greatly reduce the displacement variation of the upper main beam by 20 %-47 %. Moreover, the results of dynamic amplification factor measured at the corresponding height of the two types of piers also verified that the proposed base-bearing double vibration reduction system had greater competitiveness when the peak acceleration of seismic waves was less than 500 m/s2.

Boronic ester-based vitrimeric methylvinyl silicone elastomer with “solid-liquid” feature and rate-dependent mechanical performance

Vitrimer chemistry can integrate reprocessability, recyclability, self-healing and good creep-resistance into polymers through covalent adaptive network structure. In particular, reactive processing shows great potential to convert commercial polymers into vitrimers in industrial scale. In this work, vitrimeric silicone elastomer was successfully prepared in a one-step peroxide-induced thiol-ene click reaction between thiol-terminated boronic ester and vinyl groups of commercial methylvinyl silicone rubber (MVQ) via reactive processing. It was found that MVQ vitrimer elastomer shows good reprocessability, self-healing property, excellent elasticity and a similar gel content to that of traditional peroxide-crosslinked MVQ rubbers. Based on classical Arrhenius theory, the calculated activation energy (Ea) of B–O dynamic bond in MVQ vitrimer is 28.5 kJ/mol along with a topology-freezing transition temperature (Tv) of 6.4 °C. Intriguingly, the fabricated MVQ vitrimer shows a strongly rate-dependent mechanical response, i.e., larger mechanical strength at higher deformation rate, which is mainly due to fast bond-exchange rate of the B–O bonds even at room temperature. MVQ vitrimer shows a “solid-liquid” feature, that is, exhibiting liquid-like behavior at longer obeservation time or when stretched at low strain rate while acting as solid elastomer at high strain rate. Notably, the tensile toughness (@500% strain) can obtain nearly 1.6-fold increase to 47.59 MJ/m3 from 18.58 MJ/m3 when increasing tensile speed, indicating an excellent energy-dissipative behavior especially at high deformation rate. Therefore, our work can provide guidance for molecular design and reactive processing of high-performance vitrimeric silicone elastomers toward industrial applications.

Large-scale model test studies on a double-layer rubber dam

A new rubber dam with two layers of dam bodies anchored together into a rigid concrete base was proposed to improve the water-retaining capacity of a traditional rubber dam. A series of large-scale model tests was conducted to evaluate the static behaviour of a double-layer rubber dam under conditions of different internal and external water heads, anchoring distances and cross-sectional perimeters. It was found that the maximum tensile force of the Layer-1 dam is located at the anchoring point but that of the Layer-2 dam is located at the extruded free section. The optimal cross-sectional perimeter ratio was concluded as 0.8 with an optimal anchoring distance of 0.06 L1 and an internal water head in the upstream dam and in the downstream dam of 0.40 L1 and 0.36 L1, respectively, where L1 is the cross-sectional perimeter of the upstream dam.

Generic Recycling Strategy to Improve Robustness of Recycled Rubbers through Bioinspired Multiphase Network

Recycling of rubbers is extraordinarily important for the sustainable development of the rubber industry. However, the traditional rubber recycling processes do not only deteriorate the properties of recycled rubbers but also bring environmental pollution. Inspired by the structure of mussel byssus, our group designs bioinspired multiphase network to improve the robustness of recycled rubbers. Through increasing the content of dynamic S–S cross-links, we improve the interface interaction between isoprene rubber (IR) and waste rubber (WR). Further, the combination of IR with WR forms a dense network domain (DND) and a sparse network domain (SND), constructing the bioinspired multiphase cross-linking network. Such a multiphase network contributes to stress transfer. Upon stretching, the preferential rupture of DND improves the toughness through energy dissipation. Compared with the previous works, our designed recycled rubbers exhibit superior properties. This work presents a simple generic method to increase the robustness of recycled rubbers through bioinspired multiphase network.

Preparation of bio-based elastomer and its nanocomposites based on dimethyl itaconate with versatile properties

As the need for renewable and high-performance alternative elastomer grows, efforts have been made to develop bio-based elastic polymers for engineering applications. Herein, bio-based elastomers poly(dimethyl itaconate-co-butadiene)s (PDMIBs) were successfully synthesized by emulsion copolymerization of renewable monomer dimethyl itaconate (DMI) with partially petroleum-derived butadiene under mild conditions. It is an effective strategy to tailor PDMIB properties by comonomers with different feed ratios and to adjust the compositions and sequence distributions. The structure and thermal stability were investigated by FTIR, NMR, DSC analyses, etc. In terms of properties: (1) the vulcanizates showed excellent tensile strength (10.2 MPa), elongation at break (1146%) and toughness (37.6 MJ m−3) without filler reinforcement, which were obviously superior to the mechanical properties of most traditional petroleum-based synthetic rubbers; (2) Nanosilica-filled PDMIBs exhibited good mechanical properties, excellent abrasion resistance and oil resistance due to strong polarity in molecular chains; (3) Epoxy-functionalized poly(dimethyl itaconate-co-butadiene-co-glycidyl methacrylate) PDMIBG showed better silica dispersion and excellent dynamic mechanical properties. In summary, this new kind of bio-based elastomer PDMIBs can be used in multiple engineering applications, such as bio-based gloves, conveying belts, oil-resistant products and high-performance tire tread materials, etc. This study opens the door to the use of emulsion copolymerization and functionalization modification technology in the synthesis of new high-performance bio-based elastomer nanocomposites for the rubber industry.

Mechanical Model and Seismic Response Analysis of a Track Type Combined Isolation Device

In view of the weak isolation and shock absorption effect of ordinary isolation bearings at present, a new track damping negative-stiffness device was designed based on the principle of negative stiffness. The principle of negative stiffness was applied to base isolation, and a new isolation system was proposed in which the track-type NSD device and the common isolation layer were connected in parallel. The track-type NSD had the characteristics of clear force transmission, simple structure, and self-resetting ability. The theoretical model of orbital NSD was established, and its hysteretic performance was simulated. The seismic response of a six-story reinforced-concrete-frame isolation structure system with a new track-type-damping negative-stiffness device was analyzed. The seismic responses of the traditional lead rubber bearing isolation model (LRB), the new track-type negative stiffness and lead rubber bearing combined isolation model (NSD), and the new track-type-damping negative stiffness and lead rubber bearing combined isolation model (DNSD) were compared. The results show that, in the same case, compared with the LRB model and NSD model, the DNSD model will further reduce the superstructure acceleration response and displacement response of the isolation system, and the greater the peak value of the input seismic wave, the more obvious the isolation effect of the structural system. The new track damping negative-stiffness device enhances the energy dissipation capacity of the structural system and plays a role in controlling the displacement of the isolation layer. The displacement response of the isolation layer and the ground motion response of the superstructure are reduced at the same time, and the isolation efficiency is improved.

Turning lignin into treasure: An innovative filler comparable to commercial carbon black for the green development of the rubber industry

Driven by the global carbon neutrality action, biomass-derived functional materials have been applied in many fields to alleviate the pressure brought by the depletion of fossil energy. However, due to the complex structure, lignin faces many difficulties in its high-value utilization. The second largest biomass in the world has become the largest “natural waste”. In this paper, the lignin-based biochar-silica (LB-S) hybrid nanoparticles were prepared via a combination of two-step acid precipitation and carbonization using lignin black liquor extracted from xylose residue and sodium silicate as raw materials. The effects of carbonization temperature and lignin-based biochar (LB) content on the reinforcing properties of LB-S were studied. The results show that the particle size, specific surface area, pore characteristics, and surface polarity of LB-S all affect the mechanical properties of the final vulcanizates. The reinforcement performance of the best sample (LMB500-S) with “high structure” characteristics can be comparable to that of commercial carbon black (CB) N550. This study shows that LMB500-S hybrid nanoparticles with economic benefits possess the potential to completely replace commercial CB, which can turn lignin waste into treasure and promote the green development of traditional rubber industry in the context of carbon neutrality.

Lead-rubber-bearing with negative stiffness springs (LRB-NS) for base-isolation seismic design of resilient bridges: A theoretical feasibility study

Advanced seismic isolation devices and systems have been recognized as promising measures toward resilient design of bridge structures. This paper proposes a base isolation system using lead rubber bearing with negative stiffness springs (LRB-NS), which is composed of traditional lead rubber bearing (LRB) and pre-compressed springs, installed at the bottom of bridge columns. These springs contain dual functionalities: (1) provide negative stiffness (NS) and negative restoring force during slight shakings and elongate the structural period that is determined by LRB products; and (2) offer significant restoring forces to prohibit excessive peak deformation and protect bearings from failure when subjected to strong earthquakes. Theoretical and analytical studies are first conducted to illustrate fundamental mechanics of the proposed LRB-NS device, followed by a series of parametric analyses to understand the influential factors of this device on structural behavior. Moreover, fragility analyses of typical highway bridges are conducted to demonstrate the feasibility of LRB-NS device via comparisons with non-isolated and traditional LRB systems. The results show that the LRB-NS device can be well designed to mitigate seismic demands of bridge columns, as well as highly effective to suppress the excessive deformation in bearings that often occurs in the traditional LRB system under strong excitations. The LRB-NS device can be used to facilitate the resilient seismic design of bridge structures.

Controlling isolation system of initial combustion engines

To evaluate the effect of the engine vibration on the vehicle's ride comfort and improve the vehicle's ride comfort, three types of engine’s isolation systems including the traditional rubber mount (TRM), hydraulic mount (HM), and semi-active HM controlled by the PID control (SHM) are proposed. A dynamic model of the inline 4-cylinder engine is established to determine the excitation force of the engine. By the combination of the random excitation of the vehicle floor affecting the engine isolation system, the isolating performance of the TRM, HM, and HM is then simulated and evaluated on isolating the engine vibration and improving the vehicle’s ride comfort. Both the root mean square (RMS) values of the engine acceleration response (aRMSe) and isolation force (FRMS) of engine isolation systems are given as the objective functions. The research results show that the engine vibration combined with the excitation of the road surface roughness significantly affects the vehicle’s ride comfort. By using the SHM, both the engine acceleration and isolation force are significantly reduced in comparison with the TRM. Especially, the values of the aRMSe and FRMS are remarkably decreased by 9.32 % and 9.69 % in comparison with the TRM. Thus, to improve the vehicle's ride comfort and reduce the effect of the engine's vibration on the ride comfort, the engine isolation system used by the TRM needs to be replaced by using the SHM.

Effect of Time of Tapping on Latex Yield of Rubber (Hevea brasiliensis) in Kalutara and Moneragala Districts of Sri Lanka

Low productivity is one of the major concerns in rubber plantations and therefore, efforts should be made to exploit the maximum potential yield from a rubber tree sustainably. The exploitation of latex (tapping), which is the most important operation in rubber crop and plantations, is normally done in the morning (around 06:00-08:30) in traditional rubber growing areas in Wet and Intermediate Zones and around 05:00-07:30 in the nontraditional areas in Intermediate Zone. Some smallholders, planters and other people/groups believe or suggest that night or early morning tapping could increase the latex yield in rubber trees. Therefore, this study was aimed at exploring the effect of time of taping on the latex yield of H. brasiliensis. Rubber trees of clone RRIC 121 were used with a plot size of 15 trees and six treatments to represent times of tapping [03:00, 04:00, 05:00, 06:00 (control), 07:00 and 08:00)] at d2 frequency at Galewatta division of the Rubber Research Institute, Agalawatta, Kalutara District and 02:00, 03:00, 04:00, 05:00 (control), 06:00 and 07:00 at a smallholder field, Yudaganawa, Moneragala District for one year. Weather and latex volume data were recorded and total crop and g/t/t (gram/tree/tapping) were calculated/estimated. No significant differences were recorded for the mean total crop and g/t/t values for the trees tapped at different time intervals in both Kalutara and Moneragala districts. Models were fit to estimate the crops that could be obtained at different time durations using these data. Accordingly, a 0.04% increase in the total crop was estimated for trees tapped during 5:00-7:30 when compared to those tapped during 06:00-08:30 in the Kalutara District. Conversely, 1.6%, 3.3%, and 5.1% increase in yield were recorded in trees tapped during 04:00- 06:30, 03:00-05:30 and 02:00-04:30 respectively when compared to those tapped during 05:00-07:30. Therefore, night/early morning tapping may not be an effective or a practical strategy/solution to increase the productivity in rubber plantations in Kalutara District, while tapping during 02:00-04:00 in Moneragala District may contribute to an increase in latex crop upto around 5%. Large-scale assessments are required for further confirmation of these results.
 Keywords: Hevea brasiliensis, Latex, Morning, Rubber, Tapping

Green Routes toward Cross-Linkable and Robust Elastomers Derived from Biobased Fumaric Acid

In the rubber industry, the substitution of traditional engineering rubbers derived from fossil resources with novel biobased elastomers is considered for sustainable development, which largely relies on a straightforward and environmentally friendly synthesis procedure and the availability of material properties. In the research, semi-biobased elastomers, poly(dibutyl fumarate-co-butadiene)s (PDBFBs), were prepared by redox emulsion polymerization of dibutyl fumarate obtained from fumaric acid esterified with n-butanol and partially petroleum-derived butadiene. The microscopic structures of PDBFBs were verified by FTIR, NMR, and GPC analyses. The Tg values of PDBFBs were in the range of −73 and −58 °C. Additionally, the reactivity ratios of two comonomers in PDBFBs were evaluated by two methods: the Fineman–Ross and Kelen–Tüdös methods. The macroscopic properties of semi-biobased elastomers, such as thermal and mechanical performances, were meticulously regulated via molecular design. To achieve the desired properties, silica was incorporated into the PDBFBs to prepare strong nanocomposites. These nanocomposites displayed adequate tensile strength (14.3–31.6 MPa), adequate elongation at break (338–457%), low rolling resistance, and excellent thermoresistant oxygen aging performance. These results showed that PDBFB nanocomposites possessed quite good properties and had the potential for practical applications. This work provides a facile, efficient, solvent-less green synthesis route to design new-generation promising sustainable engineering elastomers for the rubber industry.

Dampak Pandemi Covid-19 Terhadap Permintaan Impor Karet Alam Indonesia di Negara Pengimpor Utama

Natural rubber is an important commodity in the manufacturing industry and world trade. Natural rubber as a primary commodity is traded in larger quantities than processed rubber products, but with a smaller value. Several countries have become Indonesian traditional natural rubber markets such as the United States, Japan and East Asian countries as well as European Union countries. The purpose of the study was to analyze the impact of the COVID-19 pandemic on Indonesia's natural rubber import demand in the United States, Japan and European Union (EU-28) markets. The analysis uses the Regression Discontinuity Design (RDD) model to describe the behavior and demand curve for Indonesia's natural rubber imports (especially TSNR) before and during the covid-19 pandemic. The impact of the covid-19 pandemic caused a discontinuity of the demand curve for natural rubber imports in the period before and during the pandemic at the Cut-off point. Based on the estimation results of the RDD model, the magnitude of the impact of the COVID-19 pandemic on the demand for Indonesian natural rubber in the main importing countries can be assessed. The results of the analysis show that the COVID-19 pandemic has reduced the number of requests for imports of natural rubber from Indonesia in the Japanese market by an average of 22.34 percent, the United States by 10.25 percent, and the EU-28 by 4.49 percent per month during the pandemic.

Implementation of Regulation Processing Materials Standard Indonesian Rubber in South Sumatra

This study aims to determine the implementation of the Governor’s Regulation Number 4 of 2019 concerning Instructions for Processing and Marketing of Standard Indonesian Rubber Processing Materials Traded in South Sumatra Province and its variables. variables that affect the process of implementing this policy. This study uses a qualitative method with a descriptive research approach. The process of collecting data in the form of interviews, observations, and documentation. Source triangulation technique is used to check the validity of research data. The collected data is then analyzed using the theory of process or flow policy implementation proposed by Thomas B. Smith. The results show that this policy is still experiencing obstacles at the rubber farmer group level. There was a tension at the farmer group level with the applicable regulations. This is because traditional rubber farmer groups are still bound by debts and services to collectors or brokers of rubber processing materials, so they cannot join the Bokar Processing and Marketing Unit (UPPB) formed by the government. In addition, economic factors such as the need for additional costs to process rubber in accordance with the recommendations are difficult for low-income farmers to implement.

Blending polar rubber with polyurethane to construct self-healing rubber with multiple hydrogen bond networks

Preparation of traditional rubbers with excellent self-healing ability is a difficult issue in the field of polymer materials. In the current work, we proposed a new way to fabricate self-healing traditional rubber by blending the polar rubber (epoxidized natural rubber, ENR) with the other polar polymer (polyurethane, PU) containing CC bonds and 2-ureido-4[1H]-pyrimidinone (UPy) groups (PU-UPy). It was demonstrated that the ENR/PU-UPy blend exhibits high self-healing efficiency. During curing, slightly covalent network forms in the blend, which is beneficial for the improvement in the compatibility between the two polymers. Multiple hydrogen bond networks including intermolecular hydrogen bonds between the ENR chains and the PU-UPy chains and strong hydrogen bonds between the UPy groups determine the excellent self-healing ability of the blend. The current blending method provides new ideas for the design of new self-healing traditional elastomers.

Organosolv Lignin Improved Thermoplastic Elastomeric Behavior of Polyethylene/Polyisoprene Blend.

Thermoplastic elastomers are considered the fastest-growing elastomers in recent years because of their thermomechanical recyclability, in contrast to traditional thermoset rubbers. Polyolefins such as low-density polyethylene (LDPE) show low mechanical properties, particularly poor elongation when compared with an elastomer or rubber. In this study, LDPE resin is converted to highly ductile rubber-like materials with high elongation and low modulus properties on blending with polyisoprene rubber (IR), followed by treating with dicumyl peroxide as a curing agent and organosolv lignin as an additive. The technique of high shear melt-mixing, in conjunction with vulcanization or crosslinking using organic peroxide, is used to develop hybrid materials based on the LDPE/IR blend at a 70/30 mass ratio, where LDPE is replaced partly with lignin. Various characteristics such as tensile, viscoelasticity, melt flow, crystallinity, and phase morphology of the materials are analyzed. As expected, vulcanization with peroxide can improve the mechanical performance of the LDPE/IR blends, which is further improved with the application of lignin (2 to 5 wt. %), particularly tensile strain is profoundly increased. For example, the average values of the tensile strength, the modulus, and the ultimate elongation of neat LDPE resin are 7.8 MPa, 177 MPa, and 62%, respectively, and those of LDPE/IR/lignin/DCP 65/30/05/2 are 8.1 MPa, 95 MPa, and 238%, respectively. It indicates that the application of lignin/DCP has a profound effect on improving the ductility and elastomeric characteristics of the materials; thus, this material can have the potential to replace traditional rubber products.

Development of a magnetorheological elastomer rubber joint with fail-safe characteristics for high-speed trains

The stiffness of the train’s rubber joint at the primary suspension system has a crucial influence on the operation stability and curve-passing performance. As traditional rubber joint only provides unadjustable parameters, they cannot meet the conflicting stiffness requirements when the train is running at high speed on straight track and passing through the curve track. To solve this problem, this paper proposed a new rubber joint with fail-safe characteristics based on magnetorheological elastomer (MRE). The joint stiffness is controlled by a hybrid magnetic field generated by permanent magnets and electromagnets. With this hybrid magnetic field, the initial stiffness of the MRE joint can be designed to be hard so as to suppress the hunting motions and vibrations of wheelsets and thus keep the trains’ high-speed stability; furthermore, the stiffness can decrease by energizing the electromagnets when passing through a curve track. With this characteristic, the joint can guarantee the safety of the train at high operation speed even when the joint control system fails. The prototype of the MRE joint was fabricated and assembled. Stiffness controllability of the MRE joint was tested using a Material Testing Systems machine. The result reveals that the stiffness of this MRE joint can be controlled effectively. According to the testing results, a new phenomenological model was built to predict the joint’s dynamic performance. Then this established model was integrated into dynamic models of trains to numerically evaluate the new joint’s influence on the train’s stability and trafficability. The evaluation result shows that the proposed MRE joint is fully effective on providing controllable stiffness to satisfy the conflicting stiffness requirement with fail-safe characteristics.