Scatter of measured KIC related to the scatters of local parameters Xf,σf and εpc

摘要

42 values of KIC measured at -100℃ are related to the measured values of local fracture stress σf and the fracture distance Xf by the formula: KIC= β-(N+1)/2Xf 1/2[σf (1+N)/2N/ σy (1-N)/2N].The scatters of KIC caused by σf or Xf are assessed separately at constant values of Xf or σf.It is found that at a constant Xf the scatter of KIC induced by the scatter of σf accounts for only 20％ of the total scatter,while at a nearly constant σf the scatter of KIC caused by the scatter of Xf can reach almost 100％ of the total scatter of KIC.It means that the effect of the scatter of Xf on the scatter of KIC is much larger than that of σf.This idea is opposite to the assumption widely accepted in local approach that the distribution of various sizes of the carbide particles which present various values of σf is the main event in the statistical calculation.Instead,the random distribution of (Xf) of weakest particles with the lowest values of σf should be considered as the determining factor in statistical assessment for the cleavage fracture.