Novel fracture mechanics concepts in elastomer fatigue to model the influence of temperature

Research output: ThesisDoctoral Thesis

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Abstract

Failure of elastomers is often related to fatigue. In fact, the mechanical properties of these materials make them suitable in applications in which cyclic loading overlaps with large static loads. Due to the peculiar mechanical properties, namely hyperelasticity and viscoelasticity, the investigation of elastomers¿ mechanical and fatigue properties is not a trivial task. Temperature strongly influences the mechanical and fatigue behavior of elastomers. Despite the awareness of the effects of temperature dating back to the early studies of rubber fatigue, only little effort has been made to rationalize this behavior and develop a systematic model that allows this effect to be taken into account. Thus, this thesis aims to analyze the fatigue of a non-crystallizing elastomer and specifically to investigate the effect of temperature in order to create a model able to improve the fatigue predictions. At first, the influence of self-heating upon cyclic loading due to heat build-up was assessed considering different frequencies, and interesting observations about the temperature evolution during crack propagation were made. Furthermore, an equation for the evaluation of temperature in the thickness of samples was described. Second, the fatigue crack propagation of a filled elastomer was analyzed, considering several mechanical parameters and among them, the most influential for non-crystallizing elastomers was found to be frequency. Based on these findings, the influence of temperature on the mechanical behavior was investigated in terms of large and small deformations, evidencing a strong role of fillers on the overall mechanical properties. Moreover, the fatigue crack propagation at high temperatures was studied and a model to reduce the data to a fatigue master curve was developed. Finally, fatigue lifetime investigations were correlated with initial defect size and crack propagation results. This was possible by exploiting the fatigue master curve applied according to the surface temperature monitored in the fatigue tests as a consequence of heat build-up. These results were then verified through the particle size obtained from microtomography measurements. Finally, a hyperelastic J-integral equation for notched specimens was developed, correlating the fatigue lifetime independently of the geometry.
Translated title of the contributionNeue bruchmechanische Konzepte für die Ermüdung von Elastomeren zur Modellierung des Temperatureinflusses
Original languageEnglish
QualificationDr.mont.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Sto¿ek, Radek, Assessor A (external), External person
  • Agnelli, Silvia, Assessor B (external), External person
  • Marano, Claudia, Co-Supervisor (external), External person
  • Pinter, Gerald, Supervisor (internal)
Award date21 Oct 2022
Publication statusPublished - 2022

Bibliographical note

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Keywords

  • Elastomer
  • fatigue
  • temperature
  • heat build-up
  • fracture mechanics

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