An energy dissipation approach on complete loading-unloading and dynamic impact predictions with experimental verification for rubber anti-vibration component

Accurate evaluations of a completed loading-unloading cycle and dynamic impact response for rubber anti-vibration components have been very challenging for industry over many years. In this article, we have altered the classic hyperelastic models to predict complete loading-unloading response using an energy dissipation approach. In addition, we proposed NFR (Natural Frequency Region) approach to simulate a dynamic impact event instead of using the usual viscoelastic methodology, as results from different viscoelastic models may vary widely and to avoid complex parameter fitting procedures. The proposed approaches have been validated in laboratory experiments using industrial anti-vibration components. We have also detailed a procedure for engineers to implement this approach in commercial finite element software without writing intricate user subroutines, as simulation based on finite element method has been routinely used in industry to support design of new products. It is suggested that these methodologies could be used for a design stage in engineering applications.     

Numerical prediction and experiment on rubber creep and stress relaxation using time-dependent hyperelastic approach

Rubber is an excellent material for anti-vibration components in industry with a long term service. However, its time-dependent behaviour is undesirable in engineering applications. This article presents an engineering approach to evaluate the time-dependent responses, i.e., creep and stress relaxation, for rubber anti-vibration components. A time-dependent damage function was introduced into hyperelastic models. This function can be expressed in three forms. A typical rubber product and a dumbbell specimen were selected to validate the proposed approach. It has been shown that the predictions obtained from this method are consistent with the experimental data. It has also been established that the time-dependent response of industrial products can be predicted based on the responses from simple specimens, e.g., dumbbell specimen. In addition, it is possible to obtain a creep response based on a relaxation response and vice versa (by changing K value only) using the proposed approach, which has also been observed experimentally in the literature. The proposed function can also be easily incorporated into commercial finite element software (e.g., Abaqus). It has been demonstrated that the proposed method may be used at an appropriate design stage. Finally, the readers can select one of the three forms presented to perform assessments on the time-dependent responses evaluations for rubber anti-vibration products.     

Creep loading response and complete loading–unloading investigation of industrial anti-vibration systems

This article presents engineering approaches to evaluate creep loading response and a complete loading–unloading procedure for rubber components used as anti-vibration applications. A damage function for creep loading and a rebound resilience function for mechanical unloading are introduced into hyperelastic models independently. Hence, a hyperelastic model can be extended for both creep and unloading evaluations. A typical rubber product and a dumbbell specimen were selected to validate the proposed approaches. It has been demonstrated that the predictions offered by the new models are consistent with the experimental data. In addition, a loading procedure using the same final value, with and without involving unloading, prior to a creep test can produce different results. The proposed approach can capture this phenomenon which was observed in the literature. The proposed approach can also be easily incorporated into commercial finite element software (e.g., Abaqus). It is demonstrated that the proposed method may be used for anti-vibration products at an appropriate design stage.     

Pragmatic Approach to the Evaluation of the Polymer-Mediated Force and Stability Ratio of Nano-Fillers Immersed in Rubber Materials

We used self-consistent field theory to derive the expression for the potential of the polymer-mediated forces acting between non adsorbing and weakly adsorbing nanoparticles in generic excluded volume polymer systems. By way of analyzing the physical structure of the obtained exact result for the polymer-mediated potential, we developed a pragmatic approach to evaluating this potential and associated filler flocculation stability ratio in dense rubber systems. The thus obtained theoretical approximation expresses the polymer-mediated potential acting between nanoparticles immersed in rubber through the relevant experimentally accessible quantities: filler immersion free energy, compressibility, and density correlation length of a rubber. By making use of the developed pragmatic approach, we have evaluated the polymer-mediated potential and the associated filler flocculation stability ratio for selected practically important filler and rubber materials.     

一种基于分子链统计理论的橡胶超弹性混合本构模型

橡胶材料因其独特的超弹性在实际中广泛应用,通过解析应力-应变关系可以为橡胶力学性能的工程应用提供理论指导.为了更准确地描述橡胶材料力学性能,提出一种适用于橡胶材料的超弹性混合本构模型.新模型基于Gaussian模型与八链模型,引入有关拉伸比的权重函数将二者耦合,在拉伸比较小的情况下,新模型退化成Gaussian形式,在...     

橡胶在动态载荷下的能量损耗分析

以交联密度不同的同类轮胎胎面胶A1和A2为研究对象,通过动态拉伸实验得到储能模量及损耗模量随频率变化的曲线.建立了黏弹性广义Maxwell模型来定量分析不同温度的橡胶在不同频率的动态载荷下的能量损耗.采用非线性规划的方法分别在低频(10~25 Hz)及高频(25~60 Hz)下拟合模量-频率曲线,得到黏弹性广义Maxwell模型的参数值.采用有限元软件Abaqus模拟胎面胶动态拉伸过程并计算胎面胶的损耗角正切,得到不同温度下胎面胶的损耗角正切随激振频率的变化规律,通过和实验结果的比较证明文中所述黏弹性广义Maxwell模型及其参数获取方法可准确应用于胎面胶的动态拉伸性能分析.预测了在不同温度及频率下每一循环载荷周期中胎面胶的应力-应变迟滞回线以及单位体积胶料的能量损耗,阐释了不同温度下的胎面胶的能量损耗随频率的变化规律,同时结合2种胎面胶的交联密度测试数据分析了胶料的构效关系.     

Understanding the reinforcement and dissipation of natural rubber compounds filled with hybrid filler composed of carbon black and silica

The performance of reinforced rubber compounds depends on the filler composition while the reinforcement and dissipation mechanisms still remain unclear.Herein linear and nonlinear dynamic rheological responses of carbon black/silica hybrid filler filling nature rubber compounds are investigated.The rheological contributions of dynamically retarded bulk phase and filler network are revealed to be crucial at high and low frequencies,respectively,and the bulk phase is shown to be of vital importance for the occurrence of nonlinear Payne effect at mediate frequencies.A framework for simultaneously solving reinforcement and dissipation varying with filler composition and content is suggested,providing a new perspective in understanding the filling effect for manufacturing high-performance rubber materials.     

Investigation on effects of dynamic fatigue frequency,temperature and number of cycles on the adhesion of rubber to steel cord by a new testing technique

The effects of dynamic fatigue frequency, temperature and number of cycles on the adhesion of rubber to steel cord in a carcass recipe were examined. A new test method with special rubber/steel cord specimens was developed for the dynamic fatigue measurements which were carried out on a De Mattia Rubber Flexometer. It was found that the dynamic “pull-out forces” decreased with increase of fatigue frequency, but first increased and then decreased with increasing temperature and the number of fatigue cycles. The adhesion failure mainly occurred in the rubber phase rather than at the rubber/steel cord interface. The covered rubber on the “pulled-out” cord after fatigue appeared to form a screw thread and the greater pull-out force corresponded to more uniform and clearer screw threads in the rubber remaining on the cord. Steel cord with an outer wrapping wire had greater static adhesion force and better adhesion after fatigue; the adhesion failure mainly occurred in the rubber phase but some occurred at the contact point of the outer wrapping wire and the wrapped main steel wires. The screw threads of rubber coverage appeared along the twist direction of the outer wrapping wire. SEM indicated that un-dispersed filler agglomerates may initiate adhesion failure.     

聚合物共混物脆韧转变性能研究 Ⅳ橡胶粒子的分布对PVC/NBR共混物脆韧转变的影响

根据作者已建立的准网络形态模型和推导出的基体层厚度计算公式，从实验上研究了橡胶粒子的分布对聚氯乙烯（ＰＶＣ）／丁氰橡胶（ＮＢＲ）共混物脆韧转变的影响．结果表明，不仅无规形态ＰＶＣ／ＮＢＲ共混物存在脆韧转变主曲线，而且准网络形态ＰＶＣ／ＮＢＲ共混物也存在脆韧转变主曲线．但是两条主曲线明显不重合，表明橡胶粒子的分布对ＰＶＣ／ＮＢＲ共混物脆韧转变有显著影响．而且准网络形态ＰＶＣ／ＮＢＲ共混物的临界基体层厚度比无规形态ＰＶＣ／ＮＢＲ共混物的临界基体层厚度大得多，表明准网络形态比无规形态明显有利于增韧．因此临界基体层厚度不仅是基体的特征参数，还是界面粘结和橡胶粒子分布的函数．     

Effect of CTBN rubber inclusions on the curing kinetic of DGEBA-DGEBF epoxy resin

The curing kinetics of an epoxy resin matrix, based on diglycil ether of bisphenol A and F (DGEBA-DGEBF), associated with an anhydride hardener, at different carboxyl-terminated copolymer of butadiene and acrylonitrile liquid rubber (CTBN) concentration (0-10 phr) are studied using a differential scanning calorimetry (DSC) and a stress-controlled rheometer in isothermal and dynamic conditions. The aim of this work is to correlate the presence of the rubber phase with the transition phenomena that occur during the curing process. The CTBN rubber induces a catalytic effect on the polymerization of the pure resin clearly observed by a significant enhancement of the curing rate. Calorimetric and rheological analysis also evidences that gelation and vitrification times take place not punctually but in a wide range of time. Rheological data show that the presence of rubbery phase induces a higher rate of gel formation during the early stages of the reactions, confirming the calorimetric results. Finally the results are compared with theoretical models evidencing a good fitting between experimental and predictive data.     

Comparison of reinforcing efficiency between Si-69 and Si-264 in a conventional vulcanization system

Silica has long been recognized as a reinforcing filler, especially for light colored products. The degree of reinforcement is noticeably increased when silica is used in combination with silane coupling agent. Therefore, various types of silane coupling agents are now commercially available. In the present study, two types of silane coupling agents, e.g., bis-(3-triethoxysilylpropyl) tetrasulfane (Si-69) and 3-thiocyanatopropyl triethoxy silane (Si-264) were selected for comparison of their reinforcing efficiency in a conventional vulcanization (CV) system. The results reveal that the addition of silane coupling agent not only improves compound processability, but also enhances the mechanical properties of the rubber vulcanizates. Compared with Si-69, Si-264 gives rubber compounds with better processability due to its greater ability to promote filler dis-agglomeration during mixing. In addition, Si-264 also imparts a greater degree of reinforcement. This might be attributed to the combined effects of better rubber–filler interaction, better filler dispersion and higher state of cure which are obtained when Si-69 is replaced with Si-264. The dynamic properties of the rubber vulcanizates are also improved with the presence of silane coupling agent. In this aspect, Si-69 performs better than Si-264 as it provides rubber vulcanizates with lower heat build-up.     

The correlation of tear deviation and resistance with the bound rubber content in rubber-silica composites

The tear strength (T_S) of rubber-silica composites is inevitably lowered by the reduction of viscoelastic dissipation imparted by the use of bifunctional silanes. It is of interest to find out whether promoting crack tip deviation represented by a slip-stick tearing can compensate for such a loss in the tear strength. Here, the phenomenon of crack growth in terms of the T_S and also the tearing type is considered for both the untreated and silane-treated silica rubber composites to figure out the microstructure parameters affecting the slip-stick tearing. It was realized that within a certain volume fraction of the reinforcing filler, deviation whether in the form of slip-stick or knotty tearing can be found for both cases. Tearing for silane-treated silica is more similar to a slip-stick tearing with an ordered pattern of deviation and re-initiation; whereas tearing in the composites with untreated silica is like a knotty one with random deviation and re-initiation. Interestingly, a dual role was identified between the bound rubber content and the tearing: on one hand, increasing the bound rubber directly augments the viscoelastic dissipation and the value of T_S, and on the other, it inversely suppresses the crack tip deviation. The second part of this work deals with applying strategies to promote crack tip deviation in treated silica systems. By increasing the degree of bonding at the rubber-silica interface and reducing the bound rubber, the tear deviation was successfully promoted. With a slip-stick type of tearing the crack had to proceed through a tortuous path, thereby enhancing the effective tear diameter and the subsequent tear strength. This roughening role of bound rubber is however insufficient to fully compete with the impact of bound rubber on the viscoelastic dissipation, and thus the decreased T_S of composites with treated silica cannot be totally compensated by this strategy.     

Mechanistic modeling of reversion phenomenon in sulphur cured natural rubber vulcanization kinetics

A novel kinetic model of natural rubber sulphur vulcanization is proposed. The modeling approach takes into account current knowledge on the different polysulfidic structures present during vulcanization, and the associated individual reactions. A simplified scheme is proposed, giving a mechanistic view of the reversion phenomenon, which results in a decrease of the elastic modulus (related to the sulphur crosslink density) for long vulcanization times at high temperature. The resulting set of differential equations is solved by an appropriate numerical method to predict the evolution of the degree of vulcanization for isothermal cure conditions.     

Suppression of ringing oscillations from high speed rubber compression curves through a detailed modal characterization of servo-hydraulic machines

System ringing is one of the most important factors affecting the quality of data obtained in high speed dynamic material tests using servo-hydraulic machines. This phenomenon is characterized by vibrations originated by the excitation of predominant modes of the machine during tests, producing distinctive waves in material curves that severely distort the required results. In the specialized literature, the quantitative study of these vibrations has mainly been carried out considering the testing machine as a single degree of freedom system, which has led to a general understanding of the variables involved in the process. However, discrepancies between analytical predictions and experimental observations have been detected using the single degree of freedom approach, so the need for further detailed study of machine dynamic characteristics has been reported. The work presented in this paper addresses this requirement by means of a detailed characterization of the dynamic behavior of a MTS 819.10 high rate testing system. Natural frequencies, mode shapes and damping factors have been obtained from an experimental modal analysis performed on the machine and a mathematical model of the process has been developed from these modal parameters. This model has been used to detect the modes that have the greatest influence in system ringing when testing rubber at high strain rates, and to predict quantitatively the amplitudes of vibrations produced in the process. Material curves have been corrected by subtracting the predicted undulations from the original measurements, obtaining smooth curves that adequately reflect the real material behavior at high strain rates and, thus, demonstrating the effectiveness of the proposed procedure. Although the research conducted in this work has been focused on rubber, the procedure can be extended equally to characterize other materials, thus constituting a valuable tool to correct experimental measurements contaminated by ringing.     

Evolution of the dynamic fatigue failure of the adhesion between rubber and polymer cords

The evolution of the dynamic fatigue of the adhesion in a tire carcass compound reinforced by polymer cords under cyclic loading was investigated using a self-developed fatigue test. The characteristic curves are used to explain the evolution of the fatigue failure of the adhesion between rubber and polymer cords. Three stages are identified during the evolution of the dynamic fatigue. Under stress-controlled mode by MTS-ETS (Mechanical Testing&Simulation–Elastomer Testing System), an equation to forecast the adhesion life of rubber/polymer cords composites has been developed. Under strain-controlled mode by MTS, a strain threshold value (87.8%) separating the evolution into two parts was identified. The effects of frequency on the adhesion were also investigated and suggest that, within the experimental range, regardless of the frequency, the adhesion life at a given stress amplitude is constant.     

Influence of reversion on adhesion in the rubber-to-metal vulcanization-bonding process

The vulcanization bonding process is used in a growing number of industrial applications where rubber-to-metal bonded assemblies are needed. The complexity of this process lies in the fact that the vulcanization of the rubber and curing of an adhesive previously coated on the metallic surface have to take place simultaneously during a single molding step.In the present work, we present an instrumented molding device allowing the production of adhesion peeling test samples under well controlled curing temperature cycles. Tests performed on a model natural rubber compound with a commercial adhesive system show that, for high cure temperatures, the quality of the rubber-to-metal bonding obtained is significantly reduced. The decrease of the peeling energy appears to be inversely proportional to the reversion undergone by the rubber during cure. Such a result points out the necessity of taking into account this phenomenon for optimization of the vulcanization bonding process.     

橡胶增韧塑料机理

综述了橡胶增韧塑料机理研究的发展与现状,着重探讨了橡增韧机理中有关脆韧转变的定量研究,同时也讨论了分散相的形态参数、界面相容性和韧性测试条件以及分散相与基体的性能等因素对橡胶增韧塑料性能及增韧的影响,最后提出了橡胶增韧塑料研究的发展趋势。     

Leakage behaviour of elastomer seals under dynamic unloading conditions at low temperatures

In technical applications, static seals are sometimes also subjected to dynamic loadings. Therefore, the leakage behaviour under dynamic conditions has to be evaluated as well. For this purpose, FKM elastomer seals have been tested by using newly designed equipment that allows for rapid partial release of the seal and simultaneous leakage rate measurement at a wide range of test temperatures. Furthermore, material characterisation was done by using Dynamic Mechanical Analysis, Differential Scanning Calorimetry and Compression Set. It was shown that, under static conditions, the leakage rate increased significantly during cooling at temperatures around 18 K lower than the glass transition range. On reheating, the seal's functionality was restored in the high temperature region of the glass rubber transition. In the subsequent dynamic release tests, that comprised a reduction of the seal compression within 1 s from 25% to 23%, increased leakage rates were observed in the high temperature region of the glass transition range. It was shown that the temperature that is critical for increased leakage is significantly lower under static conditions compared to dynamic conditions. The obtained leakage rates for static tests and dynamic release tests at different temperatures were analysed with reference to results of the material characterisation.     

聚合物共混物脆韧转变性能研究 V.橡胶粒子的分布对聚氯乙烯/丁腈橡胶共混物韧性刚性关系的影响

聚合物共混物脆韧转变性能研究Ｖ．橡胶粒子的分布对聚氯乙烯／丁腈橡胶共混物韧性刚性关系的影响刘浙辉朱晓光张学东漆宗能（中国科学院化学研究所工程塑料国家重点实验室北京１０００８０）蔡忠龙（香港理工大学应用物理系香港九龙）王佛松（中国科学院北京...     

Formation of Network by Carbon Black，Silica and Their Mixing Fillers in Isoprene Rubber北大核心CSCD

The network formed by fillers has great influence on the mechanical properties of rubber materials. To understand the formation of network by carbon black,silica,and carbon black/silica mixing fillers in rubber and its influence on the properties of rubber,isoprene rubber/filler composites with different filler loadings are prepared and their micromorphology,rheological and tensile properties are investigated. It is found that the dispersion of fillers is better in rubber after cure than that in rubber before cure for all three rubber systems,and the filler size of silica is smaller than that of carbon black,but the aggregation is more severe in silica filled rubber system. In mixed filler system,the two fillers tend to aggregate separately, leading to the low modulus at small strain than that in single filler system. With the increase of the filler loading,the tensile strength increases first and then decreases,the elongation at break decreases,and the temperature rise in compression flexometer tests increases. Moreover,the temperature rise in mixed filler system is higher than that in single filler system at high filler loading. © 2022, Science Press (China). All rights reserved.