Finte element modeling of the behavior of polymethyl-methacrylate (PMMA) during high pressure torsion process

This work tackles crack propagation mechanisms of styrene butadiene and natural rubbers, both subject to cyclic loading under a positive load ratio. The experimental evidence is based on pure shear loading of notched specimens supported by SEM analysis of fracture surfaces. Relationship between crack growth rate and tearing energy is revisited. The experimental results show that the fatigue behaviour of studied vulcanisates can be clearly separated in the power-law regime. Furthermore, the reported results from the literature extend this statement to any load condition. Fracture surface observations reveal also differences in energy dissipation mechanisms inferred to structural mutations in the case of natural rubber. Alternation of rough and smooth fracture surfaces associated with change in crack growth rate is more likely to occur for styrene butadiene rubber. All observations suggest that crack branching is a secondary ranked dissipation mechanism for the studied materials compared to crack deviation.