The PS specimens were subjected to three point bending under different loading rate.Through the analysis of experimental results

the forming process of the mirror zone and the rib zone is the principal process of energy consumption.With the increase of loading rate

the size of mirror zone decreases and tends towards constant progressively.At the same time

the rib width decreases while the roughness of rib zone increases.A minimum appearing at the loading rate 2.5m/min exists in the relationships between energy consumption and loading rate.When loading rate below 2.5m/min

the fracture surfaces were chiefly made up by the mirror zone and the last fracture zone.The change of break energy is mainly decided by the change of the size of mirror zone.When the loading rate beyond 2.5m/min

the fracture surfaces were conposed of the mirror zone

the rib zone and the last fracture zone.The change of energy consumption is primarily decided by the roughness of rib zone.