Rubber Gasket Research Articles

Multi-scale modeling for low-temperature sealing performance of fuel cell

A unit cell of proton exchange membrane fuel cell (PEMFC) contains a special ‘sandwich’ sealing structure composed of membrane electrode assembly (MEA), the metal bipolar plate (BPP), and a rubber gasket, which is easily influenced by external impacts, vibrations, or temperature loads. In particular, PEMFCs have to go through low-temperature loads in using environments making the lifetime and reliability of the PEMFC reduced. The temperature-shrinkage at the macro-scale and the morphology change at the micro-scale of the rubber gasket are both going to appear if the temperature is low and the PEMFC sealing performance is going to be obviously affected. The macroscopic temperature-shrinkage which includes the size-variation and the spring-back weakening is considered to establish the actual compression ratio model mathematically for low-temperature sealing of rubber gaskets in this paper. Then the influence of gasket microscopic morphology on contact behaviors is studied to reveal the interfacial sealing mechanism by using numerical simulation methods. Finally, the multi-scale model for low-temperature sealing performance of PEMFC has been constructed in this paper. The accuracy of the multi-scale model could be verified by comparing experimental contact pressure results between the rubber gasket and the metal plate.

Prediction on the time-varying behavior of tunnel segment gaskets under compression

The compression force is a critical indicator for assessing the waterproofing capability of ethylene propylene diene monomer (EPDM) rubber gaskets, and the relaxation of EPDM gaskets under compression is a key factor contributing to water leakage in shield tunnels. In this study, detailed accelerated aging tests of gaskets with different precompression openings were conducted. Analytical method and simulation method for predicting the long-term performance of EPDM gaskets considering their different compression states were proposed. First, the compression curve of the gasket was divided into three stages to analyze the mechanism of compression force degradation in depth. Under the action of a compression force, the unrecoverable deformation caused by open holes shortened stage III of the compression curve, which constituted the primary factor influencing gasket compression force relaxation. In addition, the Arrhenius equation was used to establish a conversion relationship between the accelerated aging test conditions and actual service time, and an analytical expression (AE) method for predicting the compression force degradation pattern of gaskets was proposed. Finally, a finite element (FE) method based on the relaxation constitutive model was proposed, enabling simulation of deteriorating tunnel segment gasket performance under complex compression states. Then, the effectiveness and accuracy of the proposed relaxation model were validated by comparing the compression force curves and deformation states obtained from experiments and simulations. Based on the time-varying relaxation constitutive parameters, the variation in the compression force of EPDM gaskets with different joint openings over time was simulated. The results show that the minimum compression force retention rates of gaskets after 100 years of service predicted by the AE method and FE method are 28.5 % and 30.6 %, respectively. This study provides two effective means for predicting the long-term mechanical performance of compressed EPDM gaskets, offering pivotal insights for long-term waterproofing design of shield tunnel joints.

Study on the Seepage Mechanism of Gaskets at the Joints of Shield Segments Based on Coupled Euler-Lagrangian Method

In the construction and operation stage of urban shield tunnels, joint leakage of shield is always an urgent problem to be solved. In order to further explore the waterproof performance of elastic rubber gaskets at segment joints, the finite element software ABAQUS (2022) was used to establish a fluid-solid coupling calculation model. The dynamic simulation of the leakage process at the segment joints under water pressure revealed the whole process of leakage at the segment joints and the instant water pressure value when the waterproof system failed. The results show that during the whole process from segment assembly to joint leakage, the elastic rubber gasket has experienced four key stages: gasket compression, confined water pushing, water wedge and final leakage. When the opening amount of the gasket is 6 mm and 10 mm, the contact stress between the gasket shows a “W” symmetrical distribution of high at both ends and low in the middle, and the peak of the contact stress at both ends of the interface is about twice as much as that in the middle. The waterproof threshold of the gasket is closely related to the opening amount of the gasket, and the waterproof threshold has the same trend with the initial contact stress between the gaskets.

Time-varying compressive properties and constitutive model of EPDM rubber materials for tunnel gasketed joint

The stress relaxation of ethylene propylene diene monomer (EPDM) rubber material in a compressed state significantly increases the risk of water leakage at tunnel precast segmental joints. Additionally, EPDM rubber gaskets typically experience a complex precompression strain state, further complicating the prediction of long-term stress relaxation. Therefore, it is imperative to propose a novel constitutive model that realistically reflects the stress relaxation of rubber with arbitrary precompression strain, providing a reference for the long-term waterproof design of shield tunnels. In this study, the time-varying properties of EPDM rubber at material level were studied in detail. At first, a comprehensive set of accelerated aging tests were conducted on EPDM rubber samples with varying precompression strains. The hardening effect of rubber without precompression and the stress relaxation effect of rubber with precompression were explored. The time-varying law and mechanism governing rubber properties under these two effects were analyzed. Subsequently, a conversion relationship between the EPDM rubber test conditions and the actual service time was established. The predicted hardening coefficient for uncompressed EPDM after 100 years is 1.468, whereas the relaxation coefficient for compressed EPDM is 0.359. Comparative analysis revealed that the compression set index do not consider the beneficial effects of hardening, resulting in a 54.1% overestimation of the design water pressure. Finally, the analytical study on the constitutive model of EPDM rubber material was carried out. The error in compression curve for unaged sample obtained from empirical formulas exceeded three times that of the analytical model, underscoring the need to study time-varying constitutive models. An interpolation method was employed to extend the test curve, leading to the development of a new constitutive model that represents the stress relaxation characteristics of EPDM materials under arbitrary precompression strain states. By combining the proposed constitutive model with the timetemperature conversion relationship, the time-varying expressions of the constitutive parameters for relaxation and hardening effects during the service life were derived. In comparison with existing models, the proposed model demonstrates wider applicability, effectively captures the time-varying characteristics of EPDM materials under arbitrary precompression strains, offering an efficient approach for studying the long-term stress relaxation prediction of rubber gaskets in shield tunnels under complex precompression strain states.

From Formulation to Application: Effects of Plasticizer on the Printability of Fluoro Elastomer Compounds and Additive Manufacturing of Specialized Seals.

This work investigated material extrusion additive manufacturing (MatEx AM) of specialized fluoroelastomer (FKM) compounds for applications in rubber seals and gaskets. The influence of a commercially available perfluoropolyether (PFPE) plasticizer on the printability of a control FKM rubber compound was studied using a custom-designed ram material extruder, Additive Ram Material Extruder (ARME), for printing fully compounded thermoset elastomers. The plasticizer's effectiveness was assessed based on its ability to address challenges such as high compound viscosity and post-print shrinkage, as well as its impact on interlayer adhesion. The addition of the PFPE plasticizer significantly reduced the FKM compound's viscosity (by 70%) and post-print shrinkage (by 65%). While the addition of the plasticizer decreased the tensile strength of the control compound, specimens printed with the plasticized FKM retained 34% of the tensile strength of compression-molded samples, compared to only 23% for the unplasticized compound. Finally, the feasibility of seals and gaskets manufacturing using both conventional and unconventional additive manufacturing (AM) approaches was explored. A hybrid method combining AM and soft tooling for compression molding emerged as the optimal method for seal and gasket fabrication.

Usulan Perbaikan Kualitas pada Produksi Flanges Pipe dan Rubber Gasket Guna Mengurangi Produk Cacat (Studi Kasus : CV Anugerah Sukses Sejahtera Surabaya)

CV Anugerah Sukses Sejahtera is a company that operates in the field of manufacturing flanges and rubber gaskets. The company's production process sets a defect tolerance at 5%. In the production flow there is a process failure or defect that occurs in the production process and increases the tolerance amount above a predetermined limit. From the data that has been collected, researchers can identify the types of defect characteristics using the SPC (Statistical Process Control) method and analyze them using fishbone diagrams, as well as provide suggestions for improvements to the company. Based on the Pareto diagram, it was concluded that the highest percentage of defects was in burry defects at 43.2%, the highest rubber attribute defects were in wrinkles at 36.7% and variable flanges defects were in flatness defects at 44.1%. Based on the processing of samples 1-8, it was found that sample proportions exceeded the control limits of the P flange control chart, namely UCL at week 5 and LCL at week 6, while the other proportions were still in the control stage. The dominant cause of this problem is employees' lack of control over the job desk and lack of maintenance on machines. Thus, the proposed improvement given to the company is to carry out On Job Training for new employees, check the rubber raw materials and flanges raw materials, add LED lighting to each machine and carry out regular machine maintenance scheduling

PEMFC sealing modeling relating to fractal characteristics of gasket-BPP interface based on micro-contact

The interface leaking of the gasket-BPP sealing structure affects the efficiency, safety, and reliability of PEMFCs. Aiming to reveal the basic cause of interface leaking and predict the leakage rate, the contact behavior at the micro-scale had been researched by FEM with the fractal multi-scale method, which could eliminate the negative influence of a single observation scale on the gasket-BPP rough interface modeling. Furthermore, in order to relate the contacting behavior at the micro-scale to the leakage rate at the macro-scale of PEMFCs, the mapping model had been established to analyze the sealing performance of the entire interface through the self-affine and self-similar characteristics of the fractal multi-scale contacting model of the gasket-BPP. Not only macroscopic properties of gasket rubber materials are considered in this model, but also microscopic morphologies are taken in to investigate the interface leakage rate, which had not been studied in traditional macroscopic research. By comparing the compression curves and interface leakage rates of the flange sealing device in testing and calculating approaches, the accuracy and reliability of the mapping model had been verified, leading to the analysis and the prediction of the PEMFC interface leakage rate rapidly.

Improvement of the Cracking Moment-Based Asphalt Mixture Splitting Test Method and Splitting Strength Research

The asphalt mixture splitting test is one of the most important methods for measuring asphalt’s tensile properties. To characterize the limitations of the traditional splitting test and the influence of the specimen size and loading conditions on the accuracy of the test, the factors affecting the strength of the splitting test were analyzed to reveal the splitting failure state and establish a unified representation model between the splitting and direct tensile tests. Initially, the moment of specimen cracking was taken as a key indicator, combined with image processing technology, to establish a set of criteria to judge the splitting test. Subsequently, standardized splitting tests were conducted and compared to tests of different specimen sizes and loading methods. Based on the octahedral strength theory, the stress points before and after the improved test were compared to the existing failure criteria. Direct tensile and splitting tests were conducted at different rates, and a unified strength–rate function model was established, realizing the unified representation of direct tensile and splitting tests. The research results indicate that the standardized splitting test is prone to the phenomenon wherein the specimen end face cracks before the center, affecting the accuracy of the test and potentially leading to redundant material strength evaluations. Using a loading method with a “35 mm specimen thickness” and a “0.3 mm rubber gasket + 12.7 mm arc-shaped batten” can essentially achieve the test hypothesis of “cracking at the center first”, resulting in less discrete outcomes and closer alignment to the three-dimensional stress failure state. The tensile and splitting strengths are both power function relationships with the rate as the independent variable, establishing a unified function model of the tensile and failure strengths. The research provides a more reliable testing method and calculation model for asphalt pavement structure design, and it also provides an effective basis for the improvement of splitting tests on materials such as concrete and rock.

Investigation of Long-Term Waterproof Performance and Hardness Change of EPDM Rubber Gasket Used for Shield Tunnels

Investigation of Long-Term Waterproof Performance and Hardness Change of EPDM Rubber Gasket Used for Shield Tunnels

Piezoelectric sensing method for segmental joint contact stress during shield tunnel construction

The emergence of curved shield tunnels poses a significant construction challenge. If the quality of the segment assembly is not guaranteed, many segment cracks and damage will result from the stress concentration. Sensing the contact stresses between segmental joints is necessary to improve the quality of segments assembled for shield tunnel construction. Polyvinylidene difluoride (PVDF) piezoelectric material was chosen for the sensor because it can convert contact stresses into electrical signals, allowing the state of the segmental joints to be effectively sensed. It matches the working environment between the segmental joints of the shield tunnel, where flexible structures such as rubber gaskets and force transfer pads are present. This study proposes a piezoelectric sensing method for segmental joints in shield tunnels and conducts laboratory tests, numerical analyses, and field tests to validate the feasibility of the method. The results indicate that the PVDF film sensor can effectively sense the entire compression process of the gasket with different amounts of compression. The piezoelectric cable sensor can effectively sense the joint offset direction of the gasket. For differently shaped sections, the variation in the force sensed by the piezoelectric cable sensors was different, as verified by numerical simulation. Through the field test, it was found that the average contact stress between the segmental joints was in the range of 1.2–1.8 MPa during construction of the curved shield tunnels. The location of the segmental joints and the type of segment affect the contact stress value. The field monitoring results show that piezoelectric sensing technology can be successfully applied during assembly of the segments for effective sensing of the contact stress.

HNBR and NBR gasket rubbers for plate heat exchangers: Thermo‐oxidative aging and service lifetime prediction

AbstractAmong several available rubbers used in gaskets for plate heat exchangers, the selection of the appropriate material for each operation window is crucial. This work evaluated nitrile butadiene rubber (NBR) and hydrogenated butadiene rubber (HNBR) gaskets aged at high temperatures for up to 60 days. The properties assessed of compression set (CS), hardness, and cross‐link density demonstrated superior degradation rates for the NBR specimens. Fourier transform infrared analysis showed that the hydrogenation process predominantly affected CC double bonds. Compress stress relaxation highlighted the impact of aging on the counterforce of rubber over time. Furthermore, indentation modulus profile analysis showed heterogeneous degradation for both materials at 140°C for NBR and 170°C for HNBR. The end‐of‐life criteria of 79% CS for both materials were determined through sealing tests of the aged samples. The service lifetime prediction, using the time–temperature superposition and Arrhenius methods through the CS evolution curves, demonstrated a higher degradation resistance of HNBR gaskets, that have a superior service lifetime of at least 3.5 times at 80°C concerning those of NBR, proving a superior behavior for the hydrogenated elastomer. In addition, the evaluation of the lifetime prediction enables the verification of which rubber gasket is recommended for each operational condition in terms of material cost, service lifetime, and maintenance costs.

Sealing characteristics of aramid fiber reinforced rubber gasket with scratch depth and width defects

AbstractNon‐asbestos gaskets have high tensile properties, good permeability resistance, and resilience. Compared with traditional asbestos gaskets, non‐asbestos gaskets have the advantages of less pollution and no harm to human body. This manuscript presented an experimental and theoretical study of aramid fiber reinforced non‐asbestos gaskets. The tensile strength of gaskets with different fiber orientations and tensile rate were conducted in order to meet the industrial standard. The leakage rates of nondestructive non‐asbestos gaskets with different sizes under different medium pressures and pretightening load were investigated. The results showed that the leakage rate can reach the industrial standard when the pretightening load reached 30 MPa and medium pressures was less than 2 MPa. The artificial scratch defects were made on non‐asbestos gaskets, and the effect of the width and depth of the scratch defect on leakage rate was further investigated. The sealing failure would occur when the scratch depth reached 0.1 mm. The modified model containing defect factors was established. The results showed that the modified model can well characterize leakage rate of gasket.

Особливості використання гуми як конструкційного матеріалу під час створення вузлів стикування систем термостатування

Explosive bolts are widely used as actuating devices in the spacecraft separation systems. Explosive bolt body is divided into parts as a result of engagement of the pyromixture placed inside. Activated explosive bolts have negative mechanical effect on the interface elements and sensitive electronic devices installed nearby owing to explosive behavior of the pyromixture combustion, generating shock front with high pressure and velocities, impacts and collisions of the structural units. Cumulative effect of the above factors on the separated objects is called pyroshock. For separation systems with increased requirements to external actions and cleanliness, authors developed a shear explosive bolt or pyrobolt, divided into parts, cutting the body walls in segments, which are set in motion by action of the pressure of gases, released as a result of pyrocartridge activation. The basic sources of pyroshock for these shear explosive bolts with segments are: combustion of pyromixture, internal impacts of structural units against the bolt body; cutting of body wall in segments, release of preliminary deformed interface after activation. Structural solutions are presented to reduce the pyroshock per each of the components. Vibration impulsive loading during pyromixture combustion is reduced by optimization of explosive quantity, finding its minimum to provide the reliable activation of the device. To reduce the impact on the explosive bolt elements and shock front interface the rubber gasket is installed in the path of shock wave distribution, partially disseminating and absorbing its kinetic energy. Damper, made of easily deformable aluminum alloy, is also installed to decrease the internal impact of the rod against the explosive bolt body. Functional testing of the device, using the pendulum suspension and measuring separation speed and vibration impulsive loading, showed that body parts of the shear explosive bolt with segments are separated without significant impact loads and discharge of high-temperature gases and debris, providing reliable separation of compartments and units without damaging the sensitive equipment. Obtained values of the mechanical momentum, I = 0,4÷0,7 N•s and shock load spectrum – g-load 1950 g at the frequency range up to 5000 Hz, meet the up-to-date requirements to pyrotechnical devices. Key words: explosive bolt, pyroshock, shock wave, pyrocartridge, high-temperature gases, damper.

IMPROVEMENT OF VIBRATING EQUIPMENT FOR CLEANING CONTAMINATION OF PARTS AND UNITS IN AUTO REPAIR INDUSTRY

The paper considers the task of increasing the durability and safe operation of the device by eliminating the resonant beat of the vibration equipment during the starting torque. During the operation of automobiles, contaminants form on the surface of individual parts and assemblies, their high-quality cleaning is achieved by chemical and mechanical action on these contaminants. The use of more active chemicals is more costly and pollutes the environment. Therefore, it is desirable to achieve an increase in the efficiency of washing and cleaning by increasing the mechanical effect on pollution. It is proposed to improve the equipment for the vibrational cleaning of contamination of parts, which allows to ensure the elimination of resonant beating of the vibrating equipment during the application of the starting torque. The disadvantage of existing technologies is that during the washing and cleaning of parts with the help of vibrating machines, a phenomenon of resonance occurs, that is, a momentary beating occurs, which destroys bearing assemblies and seals, and there is a possibility of chemical liquid spilling out. To ensure the durability and safe operation of vibration devices, it is necessary to eliminate the resonant beating of the vibration equipment during the application of the starting moment. The technical result, which can be obtained when using a device for resonance-free vibration cleaning of contamination of parts, allows to ensure the elimination of resonant beating of vibrating equipment during the starting moment. The proposed technology for non-resonant vibration cleaning of contamination of parts, which contains a frame bath, flexible flange and membrane, metal washers, rubber gaskets and a vibration unit with a rotary hydraulic imbalance, in the process of operation, allows to increase the durability and safety of the device by eliminating the resonant beating of the vibrating equipment during starting moment.

Numerical Simulation of Assembly Process and Sealing Reliability of T-Rubber Gasket Pipe Joints

Underground pipelines are vital parts to urban water supply, gas supply, and other lifeline systems, affecting the sustainable development of cities to a great extent. The pipeline joint, which is a weak link, may be seriously damaged during natural disasters such as earthquakes. The failure of pipe joints can cause leakage accidents, resulting in system failure and interruption, and even some secondary disasters. Herein, based on uniaxial and plane tensile test results of a T-rubber gasket material, the assembly process and sealing performance of a T-rubber gasket joint of a ductile iron pipe are numerically simulated using the Ogden third-order strain energy density function to fit the material constant. The simulation accounts for severe nonlinearities, including large deformations, hyperelasticity, and complex contacts. The effects of the assembly friction coefficient, assembly depth, and radial clearance deviation of the socket and spigot on the seal contact pressure are analyzed. The results suggest that the entire history of the deformation and stress variations during assembly can be clearly visualized and accurately calculated. For the different friction coefficients, the assembly depth corresponding to the sliding friction condition of the spigot pipe was 74 mm, while the minimum pushing force required to assemble the T-rubber gasket joint of a DN300 ductile iron pipe was 6.8 kN at the ideal situation with a friction coefficient of 0. The effective contact pressure of the rubber gasket seepage surface under various operating conditions is much higher than the normal pressure of municipal pipelines, thus indicating that the rubber gasket joint exhibits the ideal sealing performance. Furthermore, a certain deviation, which is about 20 mm, is allowed for the assembly depth of the rubber gasket joint such that the axial displacement of the pipe joint can be adapted under an earthquake or ground displacement.

Chemical aging of sealing gasket of proton exchange membrane fuel cell

AbstractAs the key sealing part of proton exchange membrane fuel cell (PEMFC), the gasket is easily damaged in acidic solution and wet air for a long time in PEMFC, resulting in unsafe and unstable operation of PEMFC. In this paper, the regular solution (RS) and accelerated durability test (ADT) solution in PEMFC were prepared to study the aging damage process of silicone rubber gasket, and the attenuated total reflection Fourier transform infrared spectrometer (ATR‐FTIR) was used to analyze the surface changes of gaskets soaked in solutions. The results showed that the weight loss of samples increased with the soaking time in both ADT solution and RS solution, and the damage of samples in ADT solution was faster and more serious than that in RS solution. Meanwhile, the microstructure diagram also indicated that the damage of the samples in ADT solution was more serious than that in the RS solution. The ATR‐FTIR analysis results showed that the intensity of characteristic wave peaks of samples at 706, 787, 867, 1006, 1071, 1260, and 2961cm−1 in ADT solution decreased faster than that in RS solution, which was consistent with the results of weight analysis and microstructure analysis.

Plastic waste in sandy beaches and surface water in Thanh Hoa, Vietnam: abundance, characterization, and sources.

The occurrence and characterization of marine debris on beaches bring opportunities to track back the anthropogenic activities around shorelines as well as aid in waste management and control. In this study, the three largest beaches in Thanh Hoa (Vietnam) were examined for plastic waste, including macroplastics (≥ 5mm) on sandy beaches and microplastics (MPs) (< 5mm) in surface water. Among 3803 items collected on the beaches, plastic waste accounted for more than 98%. The majority of the plastic wastes found on these beaches were derived from fishing boats and food preservation foam packaging. The FT-IR data indicated that the macroplastics comprised 77% polystyrene, 17% polypropylene, and 6% high-density polyethylene, while MPs discovered in surface water included other forms of plastics such as polyethylene- acrylate, styrene/butadiene rubber gasket, ethylene/propylene copolymer, and zein purified. FT-IR data demonstrated that MPs might also be originated from automobile tire wear, the air, and skincare products, besides being degraded from macroplastics. The highest abundance of MPs was 44.1 items/m3 at Hai Tien beach, while the lowest was 15.5 items/m3 at Sam Son beach. The results showed that fragment form was the most frequent MP shape, accounting for 61.4 ± 14.3% of total MPs. MPs with a diameter smaller than 500μm accounted for 70.2 ± 7.6% of all MPs. According to our research, MPs were transformed, transported, and accumulated due to anthropogenic activities and environmental processes. This study provided a comprehensive knowledge of plastic waste, essential in devising long-term development strategies in these locations.

Results of dynamic analysis of double-inlet screw conveyor machine assembly

The article presents the results of theoretical studies of vertical and deflecting vibrations of two-stroke screws with a wavy surface and conveyor screws with a curved base and an elastic element. Based on the analysis of the obtained graphs of the relations of laws and motion parameters, their optimal values are justified. Here, the options for applying rubber gaskets to bearing bearings are considered in two versions, that is, with the same and two different types of stencils. When the rubber bushings of the bearing supports are taken in two different elasticities, the change laws of the vibration of the screw are obtained depending on the size of the supports, the moment of inertia of the screw and the change of the technological resistance force. Introduction

Study of the effect of an additional layer of insulation on the rate of heat loss in the cabin of an electric vehicle in conditions of extremely low arctic temperatures

This article examines the reduction of speedand heat loss in the passenger compartment of an electric vehicle (EV) when installing an additional thermal insulation gasket on the doors. The study was conducted in conditions of extremely low outdoor temperatures that occur in the winter season in the northern and arctic regions. To conduct a series of observations, the doors of the passenger compartment of an electric car were equipped with an additional (second) heat-insulating rubber gasket. The results were recorded for two groups of measurements, at an outdoor temperature of -25 ... -30 0C and at outdoor temperature -35 ... -40 0C.

Experimental Study on Waterproofing Performance of Segments Based on Sealant Installation Methods

When constructing a tunnel using a shield Tunnel Boring Machine, segments are mainly used. Sealants are then installed at segments for waterproofing. Two types of sealants, a hydrophilic rubber waterstop and a rubber gasket, are mainly used. Sealants can be arranged in single or double layers in consideration of construction site conditions. In this study, waterproofing performance was experimentally evaluated based on the type of sealant and the number of layers. A total of five types of sealant installation methods were tested. Waterproofing performance tests were used to determine their relative waterproofing performances under the same experimental conditions. Results showed that the hydrophilic waterstop was relatively vulnerable to a gap and the gasket was relatively vulnerable to an offset. If double layers of sealants are to be arranged at the construction site, it is recommended to arrange double layers of different types of sealants rather than double layers of the same type of sealants. This study could be helpful for selecting the type of sealant and/or the number of arrays at a construction site.