International audienceThis paper reports on the development of a new network alteration theory to describe the Mullins effect. The stress-softening phenomenon that occurs in rubber-like materials during cyclic loading is analysed from a physical point of view. The Mullins effect is considered to be a consequence of the breakage of links inside the material. Both filler-matrix and chain interaction links are involved in the phenomenon. This new alteration theory is implemented by modifying the eight-chains constitutive equation of Arruda and Boyce (J. Mech. Phys. Solids 41 (2) (1993) 389). In the present method the parameters of the eight-chains model, denoted C-R and N in the bibliography, become functions of the maximum chain stretch ratio. The accuracy of the resulting constitutive equation is demonstrated on cyclic uniaxial experiments for both natural rubbers and synthetic elastomers
ABSTRACT1. Characterizing the physical structure and assessing the habitat quality of rivers is becoming more important in the context of environmental planning, appraisal and impact assessment. In Europe the EC Water Framework Directive requires assessment of hydromorphological quality in establishing the ecological status of rivers.2. Hydromorphological quality assessment plays a crucial role in the Directive because it is used to determine 'undisturbed' and 'heavily modified' conditions of rivers. A common approach is needed to ensure comparability of classification outputs between EU Member States.3. Three hydromorphological and river habitat assessment methods, developed in Germany, France and the UK, were used for qualitative cross-comparison in 2001. Each was tested on river stretches in North-East France and in the French Pyr! e en! e ees.4. The type of features recorded by all three methods was broadly similar, but differences in survey strategy, data collection, and analysis resulted in variations in quality assessment. Different interpretation of what constitutes 'undisturbed conditions' has a major impact on outputs. There are also scale-related problems in comparing the different methods.5. Despite these differences, there is sufficient common ground to allow refinement of the methods and achieve better harmonization. This will require technical agreement on the terminology and definition of features, and a reach-based hierarchical framework for survey and reporting.6. An impact-based assessment centred on deviation from undisturbed hydromorphological conditions could be the best option for a simple, practicable classification scheme, but agreement is needed on the criteria used to define and calibrate such a system.7. Habitat quality assessment using the presence and diversity of features as a basis for classification needs to be improved. Assumptions used for diagnostic interpretation need to be tested
A detailed study of the initiation of fatigue cracks in carbon black–filled natural rubber is conducted. Interrupted fatigue tests are performed and fatigued samples are observed with a scanning electron microscope. This procedure first enables the quantification of the morphology, spatial distribution, and evolution of crack initiation sites for different strain levels, which gives some statistical data for each strain level. It also permits analysis of the chemical nature of inclusions inducing crack initiation thanks to energy dispersive spectrometry of X-rays. It is shown that fatigue damage initially occurs generally on carbon black agglomerates or oxides such as ZnO. However, those two types of inclusions correspond to different crack initiation mechanisms, and most of the time, only the initiations on carbon black agglomerates are followed by crack propagation that leads to failure. This difference is probably because carbon black agglomerates have a stronger cohesion than ZnO inclusions and a stronger adhesion to the matrix.
a b s t r a c tIn the present contribution, the relationship between the fatigue life of styrene-butadiene rubber (SBR) and the stretch amplitude was established. Focusing on the multiaxial loading effect on the life duration of SBR, experimental tests were conducted using cylindrical specimens subjected to tension and torsion loadings under constant and variable amplitudes. Based upon the continuum damage mechanics approach, a three-dimensional model was derived and coupled with the cracking energy density criterion to predict the fatigue life of SBR. The capabilities of the model, which requires only three damage parameters to be identified, were analysed and a good agreement between predicted values and experimental data were clearly highlighted for tension and torsion loadings both in constant and variable amplitudes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.