Papers by Keyword: Mullins Effect

Abstract: A stress softening known as the Mullins effect is observed usually in rubberlike material after the first load. This paper describes an experimental test method for defining the nonlinear properties of rubber materials used for finite element analysis. Experimental observations have shown that the Mullins effect induces a permanent set and some anisotropy. To test the Mullins effect the mechanical preconditioning is suggested to stabilize the properties of rubber material. A stress-strain curve will change significantly when the rubber material is strained greater than the previous stabilized level. Therefore, material properties at maximum strain level are obtained to predict behavior of rubber products. To obtain the rubber material constants used for finite element analysis to understand the characteristics of automotive rubber parts, mechanical properties tests such as uniaxial tension, equ-biaxial tension and pure shear tests are required. When the load was repeatedly applied to the rubber specimen, the stress-strain relationship was greatest in the first and second cycles, and the larger the strain range, the more the stress was reduced. The material constants were obtained using the stress-strain data after the rubber specimen was stabilized. The value of stiffness decreased as the maximum strain range increased. The static stiffness of an automotive engine mount is calculated by nonlinear finite element analysis using the experimentally determined material constants and compared with the experimental results considering the mechanical preconditioning effect resulting in a good correlation.

Abstract: In this paper, experimental results that illustrate stress softening in carbon filled natural/styrene-butadiene blend rubber (NSBR) together with Mullins effect are introduced firstly. Then, based on these data, the Ogden constitutive model is derived. The theory of pseudo-elasticity is used in the model. It is found that theory of pseudo-elasticity and Ogden constitutive model is applicable in this composite.

Abstract: This paper presents the Mullins effect on the laminated rubber-metal spring analytically modeled using lumped parameter system. The general form of the equation is developed to represent the multi-degree-of-freedom system for layer of embedded metal plates. The Mullins effect can be observed when a compression load is applied to the spring. It is shown that by increasing the embedded metal plate, the Mullins effect inside the rubber is reduced due to the improved stiffness in vertical direction.

Abstract: Most important macroscopic inelastic phenomena of filled elastomers are due to microscopic damage processes inside the rubber network. For example, the Mullins effect can be explained by debonding of polymer chains from the carbon black aggregates. In turn, the damage and following recovery of aggregates are responsible for the hysteresis. All these effects also induce anisotropy of an initially isotropic material. In the present contribution, we show how these effects can be quantified experimentally and simulated by a micro-mechanical model. The model is based on the decomposition of the rubber matrix into a purely elastic polymer, a polymer-filler and a filler cell network. The polymer-filler network model takes into account the debonding of polymer chains from filler aggregates and is thus able to predict the strain induced damage and the permanent set. The filler cell network model describes breakage and recovery of filler aggregates and is responsible for the hysteresis. The presented model is in accord with a broad range of experimental observations.

Abstract: PBX is known to exhibit highly nonlinear behaviors of deformation such as the Mullins effect of stress softening, hysteresis, residual strain, and frequency dependant responses. This paper proposes a phenomenological energy-based model for PBX considering the Mullins effect for isotropic, incompressible, hyperelastic, particle-filled materials. Uniaxial compressive loading and unloading tests at quasi-static states were undertaken in order to obtain the mechanical properties of the PBX simulants. The phenomenological energy-based model by Ogden-Roxburgh is, then, modified to make it consistent with the test result of PBX simulants in the case that the Mullins effect is dominant. Prediction with the new model shows a good correspondence to the experimental data demonstrating that the model properly describes the Mullins effect and the loading-unloading behavior of deformation.

Abstract: Static and quasi-static isothermal experiments were carried out on vibration isolation rubber sample pieces whose main raw material were nitrile rubber, Enhanced nitrile rubber and reclaimed rubber, then analysis and comparison on the acquired experimental data were carried out in detail. The causes of these phenomena were analyzed from macromolecules structure system entropy change. Mathematical model of the third time static loading of the above vibration isolation rubber sample pieces was established based on polynomial constitutive theory, considering softening effect and utilizing nonlinear data fitting technique. Mechanical performance parameters of the vibration isolation rubber material were studied in quasi-static cyclic loading condition, and vibration isolation performance was compared and analyzed.