Cracking the code for crack propagation in rubbery materials – sciencedaily
Understanding the fracture behavior of rubber materials is essential for a variety of industrial applications, including the improved design of reliable products. A Japanese team has identified the origin of a phenomenon that occurs when rubber materials under stress break rapidly and showed that this sudden breakage occurs in many viscoelastic materials.
The mechanism of the speed jump – a phenomenon in which the initial slow crack in a rubbery material in tension develops sharply and rapidly – has been a mystery for years despite its importance in the design of durable materials. Now there is evidence to support a new theory to explain this unique event.
In a study published this month in Physical examination documents, researchers at the Institute of Industrial Sciences at the University of Tokyo constructed a simplified mathematical model that merges two previous analyzes to reveal the stress-strain behavior of rubber materials during failure, thus supporting their theoretical analysis with a series experimental studies.
“The phenomenon of the speed jump in crack propagation has gone unresolved for more than 30 years,” says lead study author Atsushi Kubo. “Our step-loading model is designed to reproduce the non-monotonic mechanical behavior as the rubber material undergoes this abrupt transition of fracturing near the tip of the crack. Because it does not have to directly reproduce the complex process of fracturing. crack propagation, which involves several phenomena, this allows us to build a simplified model that successfully exhibits the speed jump. “
Using their simplified step-loading model, the researchers showed that the mechanical behavior observed from one analysis approximated the phase transition mechanism described in the other proposal, merging the two separate analyzes.
“For the staged loading model, we used linear viscoelasticity to mimic the mechanical behavior near the tip in the material. We have also implemented a stepwise function without taking into account the geometry of the crack to model the external force applied quickly to the tip of the crack. »Explains Yoshitaka Umeno, lead author. “This simplification allowed us to realize a mechanical model for the crack tip as a ‘point mass connected to a viscoelastic element under stepped load’.”
The combined theoretical and experimental study of the research team also showed that the phenomenon of speed jumping can be found in other materials.
“Our results suggest that the speed jump can occur in general viscoelastic and polymeric materials, in addition to rubbery solids. Having this integrated understanding of the mechanism is crucial to spur the development of more robust polymeric materials that are essential to many different industries, ”Kubo says.
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Material provided by Institute of Industrial Sciences, University of Tokyo. Note: Content can be changed for style and length.