Application of the load separation criterion to the study of the plastic deformation behaviour of an ABS resin during a fracture process

The plastic deformation behaviour of an elastic-plastic material, during a fracture process, can be described by the material plastic deformation function, whose construction is based on the load separation criterion. This function is dependent on the plastic deformational properties of the material under analysis, as well as on the constraint at the notch tip. With the aim to study this function in depth, in the present work, the relationships between i. the material plastic deformation function, ii. the engineering yield stress and iii. the plastic deformation mechanisms are researched for an acrylonitrile-butadiene-styrene (ABS) resin, at different temperatures and loading rates. A simple innovative procedure based on the use of blunt-notched specimens was employed for the construction of the material deformation function, allowing the investigation both at low and at moderately high (impact) loading rates. The effects of the testing conditions on the material deformation function were related to those observed for the engineering yield stress, measured by uniaxial tensile tests. Moreover, scanning and transmission electron microscopy analyses (SEM and TEM, respectively) were performed on the plastically deformed zones, to study the different plastic deformation mechanisms occurring at the various testing conditions. The results indicate that the influence of temperature and loading rate on the material plastic deformation function of an ABS resin is governed by the temperature and time dependence of the engineering yield stress, and that this function seems to be directly related to the plastic deformation mechanisms taking place during the fracture process.