Dynamic Fatigue of Rubber and the Mechanism of Failure by Repeated Deformations

Abstract

Dynamic fatigue is thn reduction of the maximum tensile strength of a material by repeated periodic loads or deformations. The dynamic fatigue of vulcanized rubber is basically the result of chemical oxidation processes, destruction during repeated deformations taking place by rupture of the chains throughout the rubber as a result of mechanically activated chemical processes. Physical factors also influence dynamic fatigue. However, the question of the nature and mechanism of dynamic fatigue of vulcanized rubber has not yet been explained ; nor has the relation between fatigue and tensile strength of rubbers been clarified. The results of studies which make it possible to establish the fundamental laws of dynamic fatigue of rubbers and the destruction mechanism during repeated deformations are presented below. Two widely used sinusoidal systems of repeated deformation were studied: (1) constant (maximum) elongations or deformations, ε = const.; (2) constant (maximum) loads or conventional stress, f = const. The number N of cycles before failure and the time before breaking, or the life of a specimen, were determined in these tests. In the first system, the breaking load, fixed by the apparatus, was less than the initial maximum load, owing to the process of “dynamic relaxation“, and in the second system they were equal. The breaking load divided by the initial cross-section and the cross-section at break gives, respectively, the conventional f and the true dynamic tensile strength σ of the specimen.

Fatigue life prediction and fracture mechanism of styrene-butadiene-styrene thermoplastic elastomer under uniaxial tension

“…Bartenev 28 found that molecular chain fracture in static fracture is a physical process, while fatigue fracture is a combination of physics and chemistry. Wang 29 found that it is easy to form multiple macro cracks under small tensile ratio through the fatigue fracture of rubber with different tensile ratio under displacement control; When the tensile ratio is large, only one main macro crack is formed, which inhibits the formation of cracks and micro cavities in the nearby area.…”

Simple quantification of elastomers’ deformation-induced entropy changes through maxwell relation implementation

“…The form of compensation depends on the individual's materialistic properties. For high-elastic materials such as rubber, Bartenev and Ogly [28] suggests a linear relation between tension and time on a log-log diagram within the maximum 2500 loading cycles; as the stretching frequency in their study is held constant, it generalizes to a linear relation between tension and loading cycles.…”

“…Despite the accuracy of Mooney-Rivlin fits and carefully controlled experimental conditions, the fatigue effect is an unneglectable phenomenon for materials under repeated periodic loads. Although the static fatigue effect could be reduced to inconsequential by avoiding very high tensions and maintaining a relaxed state between tension measurements, the dynamic fatigue effect cannot be avoided in repetitive stretching [28], which gives rise to systematic error. Therefore, a linear-form segmented compensation function is deduced to correct the data of tension.…”

“…(4) Rubber: The rubber bands applied in this study are the Natural Rubber fibers, which fall within the class of short fiber reinforced polymers and are similar to those used by Ogly [28]. Thus, they are assumed to largely satisfy the linearity in compensation function.…”

Relationship between macromolecular network and fatigue properties of unfilled polychloroprene rubber

“…Indeed, the first significant publication dedicated to elastomer fatigue was published in 1940 [1], whereas the first major work on metals was published in 1847 by Wöhler, that is, almost a century prior. The majority of works on elastomer fatigue published in the last 80 years use an experimental approach, most frequently in relation to natural rubber due to its extensive range of applications [2][3][4][5][6]. It has been highlighted that the fatigue life (defined here as the number of cycles before breakage) of rubbers largely depends on a range of parameters such as mechanical loading conditions [7][8][9].…”