Polyvinyl chloride(PVC) specimens were subjected to three-point bending.The results of test and measurement show that there is a relationship of positive correlation between roughness of fracture surface and break energy per unit area.On the other hand

a certain degree of data deviation can be seen in the relationship.The deviation is principally affected by the ratios of real area of the characteristic zones on fracture surface because the effects of every characteristic zone on break energy are different.By using the synthetic effect of roughness and the characteristic zones on break energy

the degree of deviation can be sharply reduced. So

break energy can be quantitatively analysed by combining the effects of fracture surface roughness and fracture characteristic zones.