Creep Of Rubber Research Articles

Rubber Creep Model and Its Influence on Mounting Stiffness

The mount of the engine will creep under the action of long-term load. Creep will change its original structure, resulting in changes in static and dynamic characteristics and fatigue life. In order to solve the problem of mounting rubber creep, the creep characteristics were studied in this paper. In order to study the influence of creep characteristics on engine mounting stiffness, a theoretical model of mount creep was established based on the creep mechanism of rubber. The effects of different loads on the creep characteristics of engine mount were studied. The static viscoelastic parameters and creep analysis of rubber mounting were analyzed numerically. The creep variation law of suspension under different loads is obtained. By analyzing the static and dynamic characteristics of no creep, 2.98 mm creep and 3.83 mm creep of engine mount, the creep characteristics and the variation law of mount stiffness of rubber mount were revealed. The results show that the static stiffness of suspension increases with the increase of creep. When the frequency is constant and the creep increases, the dynamic stiffness of the suspension increases obviously. In this paper, the creep characteristics of rubber mount are analyzed, and the results of the analysis provide a design method for rubber mount design.

Theoretical-Experimental Method for Determining the Short- and Long-Term Creep Parameters of Technical Rubber in Shear

A technique is developed for identifying the hereditary properties of technical rubber in short-term shear creep from the experimental shift the center of damped flexural vibrations of a vertically fixed three-layer test specimens of symmetrical structure with a technical rubber midlayer after their preliminary holding in a static bent state. This technique is based on the finite element method and integral equations of the hereditary viscoelasticity theory with the Koltunov–Rzhanitsyn heredity kernel. For identifying the rheological parameters of this kernel an objective function is constructed. To minimize the function, the direct zero-order search is used, which does not require the calculation of its gradient. The rheological parameters found are compared with experimental data of the long-term shear creep of the rubber. Noted is the unfoundedness of the direction, developed by some researchers, where only equations of the theory of hereditary viscoelasticity is used to model the vibration processes and the energy dissipation. The parameters of rubber creep kernel were identified in a long-term regime at a constant shear stress, and results showed that this type of testing is inapplicable to studying the short-term creep of rubber in shear.

A general hyperelastic‐time model for numerical prediction on rubber relaxation and experimental validation under different environments

All the methods developed for rubber creep and relaxation are validated to specific environments for now. In general, for each new loading case and new component, a data fitting procedure has to be performed to obtain different suitable parameters. This limitation has restricted developments of the theories and their applications. This article investigates a possibility to predict the time‐dependent response from data of known conditions using the time‐dependent hyperelastic approach. A number of hypotheses are proposed for considered conditions, i.e., loading, material hardness, and different components, and are validated with experimental data using a dumbbell specimen and a typical industrial anti‐vibration product. It has been proved that the concept of effective strain is a good criterion to bridge two different rubber components for time‐dependent predictions. Hence, the application restriction of the hyperelastic‐time model is successfully lifted. For the first time, it is possible to predict, not to simulate only, rubber creep/relaxation based on known parameters. By combination with previous work on temperature effect, a general hyperelastic‐time model with multiple capabilities can be established and used to predict time‐dependent response of rubber components. It is desirable to apply this approach on more engineering cases for further verification. POLYM. ENG. SCI., 59:2159–2168, 2019. © 2019 Society of Plastics Engineers

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 simulation and experiment for rubber springs

Rubber creep, as a time-dependent deformation, is one of the critical factors when considering engineering design and applications for anti-vibration structures. A function based on material damage with a variable T (time elapsed) and an invariant [Formula: see text] is introduced to hyperelastic constitutive models based on strain energy density for polymer creep prediction. The concept is to link rubber creep to its structure change, leading to degradation of the materials over the elapsed time. Hence, hyperelastic models, widely available in industry, can be extended to include the variable time T so that a creep evaluation for rubber structures can be performed at a design stage and in the service. A typical rubber-to-metal bonded component, which is used in industrial applications, is selected to validate the proposed approach. Verification shows that the proposed approach predicts nearly identical experimental results, and the method can be used for engineering design and industrial applications.

Creep of Sand–Rubber Mixtures

This technical note documents an experimental study conducted to examine the time-dependent mechanical response of specimens composed of sand and granulated tire rubber, loaded in one-dimensional compression. The results indicate that sand–rubber creep is significant and may be reasonably estimated with the use of an available soil creep model. The swelling of granulated tire rubber due to oil absorption reveals the potential for its use as a stabilizing engineering material.

Influence of physical aging on creep of rubber

The effect of physical aging on the creep response of chloropren rubber filled with carbon black was studied. The method of reduced variables and analytical method of determination of influence of physical aging on the creep compliance in short creep time test are proposed.

Creep of Rubber under Repeated Stressing

Abstract Under conditions of high stresses and/or strains it is not possible to predict cyclic creep behavior by combining a knowledge of Boltzmann's superposition principle with a knowledge of the static creep. Although experiments here have been restricted to tensile measurements, the effect is likely to occur also in other modes of deformation. It may be of significance in applications where alternating stresses are applied to rubber components and indicates a further reason for keeping working stresses low and designing to avoid fully relaxed conditions.

Systems Manifesting Superposed Elastic and Viscous Behavior

Abstract Actual substances exhibit a very complicated behavior under mechanical stresses which cannot be described by classical elasticity theory nor by the classical theory of the hydrodynamics of viscous fluids. A general molecular theory describing the behavior of matter under stress is discussed and related to previous investigations and to experimental observations. Particular attention is devoted to rubberlike substances for which the classical theories are definitely inadequate. Experimental results on relaxation and creep of rubbers are interpreted in terms of modern structural concepts. It is found that these substances exhibit three regions of stress-temperature-time dependence. At intermediate temperatures there is a region of relative stability in which the statistical-thermodynamic theory of rubber elasticity is valid. At elevated temperatures, relaxation and creep are caused by chemical changes involving the rupture and formation of primary valence bonds. These chemical changes, which are responsible for the aging of rubber, can be isolated and studied by appropriate experimental techniques. At low temperatures relaxation and creep are caused by the slipping of secondary interchain bonds which are breaking and reforming in times comparable to experimental times of measurement. Theories are advanced to explain the observed stress-temperature-time behavior of rubbers over the entire temperature range studied.

Systems Manifesting Superposed Elastic and Viscous Behavior

Actual substances exhibit a very complicated behavior under mechanical stresses which cannot be described by classical elasticity theory nor by the classical theory of the hydrodynamics of viscous fluids. A general molecular theory describing the behavior of matter under stress is discussed and related to previous investigations and to experimental observations. Particular attention is devoted to rubberlike substances for which the classical theories are definitely inadequate. Experimental results on relaxation and creep of rubbers are interpreted in terms of modern structural concepts. It is found that these substances exhibit three regions of stress-temperature-time dependence. At intermediate temperatures there exists a region of relative stability in which the statistical-thermodynamic theory of rubber elasticity is valid. At elevated temperatures relaxation and creep are caused by chemical changes involving the rupture and formation of primary valence bonds. These chemical changes, which are responsible for the aging of rubber, can be isolated and studied by appropriate experimental techniques. At low temperatures relaxation and creep are caused by the slipping of secondary interchain bonds which are breaking and reforming in times comparable to experimental times of measurement. Theories are advanced to explain the observed stress-temperature-time behavior of rubbers over the entire temperature range studied.

Compression Creep of Rubber and Rock

A compressible solid may overcome resistance to its bodily movement by a piecemeal operation if the mass involved has dimensions permitting sufficient linear compression. Because resistance, such as friction, may be overcome locally and in successive stages, a small fraction of the force needed for an immediate effect will, given enough time, bring about the same bodily movement. This slow kind of movement against outside resistance, named ''compression creep, suggests the view that the rate of geological deformation is correlated better with small forces operating through long time, than with mighty forces in critical periods. A laboratory demonstration of the principle is made possible by the use of rubber sheets. Since this material has noTable compressibility from forces needed to overcome friction, it serves admirably as a model of a great rock sheet. Application of the principle of compression creep is made to problems involved with the overcoming of friction along the soles of overthrusts, with th...