Análise de falhas em um elastômero empregado na prática de exercícios físicos

Abstract

Failure analysis makes it possible to determine the physical, human and latent roots involved in the process, as well as identify those responsible, present solutions and avoid the reproduction of similar failures. In this work, the failure analysis of an elastomer used in the practice of physical activities, fractured in service, was performed. Visual analysis of the elastomers made during investigations of storage conditions showed that the new articles had permanent fold marks on their surface, possibly caused by folding inside their packaging. These marks are discontinuities and act as favorable regions for the nucleation and propagation of fatigue cracks. Three new elastomers, similar to the failed one, were acquired with the purpose of simulating the storage conditions for 4, 6 and 14 months, with and without exposure to the sun, and to evaluate the influence of this conditioning on the mechanical properties through the tensile test. The results showed that the bending of elastomers in environments without exposure to the sun for 14 months reduces the mechanical tensile strength of the material, whereas in the case of bended elastomers exposed to the sun for 4, 6 and 14 months, the deterioration of this property was also observed. In addition to these tests, the elastomers were characterized by Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR). The results indicated that the materials analyzed are styrene-based thermoplastic elastomers (TPS). Fractography of the fractured component, performed through stereoscopy, revealed the presence of rib marks at the origin of the fracture and pointed to the fatigue mechanism as the physical root of the failure.