The Relationship between Crack Tip Opening Displacement and Stretch Zone Width

The relationships between WSZ/δ value and properties of materials proposed by some investigations are discussed by using experimental data of several materials whose yield strength is in a range of 138-878 MPa.The influences of strain-hardening exponent and yield strength on WSZ/δ value suggested by Prantl do not have a good agreement with experimental data.The major reason should be that some assumptions used in the deduction process are contradictory.The WSZ/δ value seems to be linear instead of proportional to flow stress.