The Research On The Relationship Between CTOD And J-integral Along With Their Critical Value δ_c And J_Ⅰc

CTOD (Crack Tip Opening Displacement) and J-integral are two important parameters in elastic-plastic fracture mechanics. CTOD is not a direct and close parameter for stress-strain field, so it is still difficult to define and measure CTOD, but because it can be used to solve the engineering problems effectively, it is widely used in the field of engineering. J-integral has noting to do with the integral line, so it can evade the complex stress-strain field near the crack tip, moreover, J-integral is a stress-strain field parameter with clear definition and close theory, so it is very popular to the field of mechanics. Because both of CTOD and J-integral can be used to evaluate structure security, there must be a relationship between them, this paper probes the relationship between CTOD and J-integral along with their critical value c and JIC on the basis of the fruits from the original.This paper elaborates CTOD and J-integral completely beginning with the basic concept of the two parameters, moreover, it performs an easy review to the relationship between them along with the computational methods and experimental means respectively. Laying equal stress on experiment and theory, this paper performs a research on three point bend specimens of DH40 steel with experimental means and computational method respectively. The test data and finite element calculation data were compared, moreover, the CTOD value from the experiment and the J value from the experiment and finite element calculation were related. The critical CTOD value and the critical J value were obtained by means of drawing CTOD resistance curve and J resistance curve, with which the description about the relationship between c and Jic is probed. An additional experiment is performed, and the weld specimens and heat effected zone specimens of DH36 steel are researched, through which the outcomes from the formulas of the standard and from other formulas is compared, which demonstrates the validity of standard test means for CTOD and J-integral.