The Mechanical Behavior of Polystyrene under Pressure,
CASE WESTERN RESERVE UNIV CLEVELAND OHIO DEPT OF MACROMOLECULAR SCIENCE
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Tensile deformation of polystyrene carried out under pressure up to 4 kb has shown that the pressure-transmitting fluid silicon oil acts as a stress crazing and cracking agent. Analysis of the stress-strain curves for the sealed specimens indicated that the pressure dependency of the craze initiation stress differs from that of shear band initiation stress. The brittle to ductile transition occurs when the initiation stresses of both processes become equal. The principal stress for craze initiation showed almost no pressure dependency, suggesting that crazes initiate when the principal stress level of the tensile specimen reaches a critical value irrespective of the applied hydrostatic pressure. Similarly, no pressure dependency was observed for the principal ductile fracture stress. The pressure dependency of yield stress agreed well with a non-linear pressure dependent von Mises yield criterion.
- Solid State Physics