A new type of fatigue striation on PMMA immersed in organic agents

Fatigue crack growth tests of PMMA were undertaken at 295 K in organic agents with relatively high viscosity. Regular wavy striations, the wave length and amplitude of which were dependent on the characteristics of the agent, appeared on the fracture surfaces at low values of the stress intensity factor ranges. This type of striation has not been reported elsewhere. The formation mechanism of these was analysed based on the two dimensional viscous-fluid flow through a narrow gap between the crack planes. The theoretical suggestion that the wave length of the striation tends to increase with increase in the surface tension of the liquid and a decrease in its viscosity was in good agreement with the experimental trend.