Papers by Keyword: C*

Abstract: Uniaxial creep tests on micro-regions of P92 steel base metal and welding HAZ specimens were carried out at 923 K and under different stress levels. The creep equation of index of B and n was obtained from the test data fitted by using least square method. Then, creep crack growth tests based on the reference stress method on P92 steel base metal and welding HAZ compact tensile samples were carried out at 923 K and under stress intensity factor K of 18 MPa·m^1/2. From the calculated and experimental data, it was found that a good relationship existed between the creep crack growth rate da/dc and high temperature creep fracture parameter C*. The reference stress method was verified to calculate the C* of compact tension specimens and can predict the creep crack growth rate of the P92 steel base metal and welding HAZ materials under steady state creep conditions. At the same time, high temperature defect evaluation parameters of D₀ and Φ were obtained by fitting the linear parts in the relation curves using the log-log method. This study provides tests data on the defects evaluation and life prediction of P92 steel welding materials.

Abstract: Creep crack growth (CCG) rate has been organized frequently by C* or Ct parameter However, crack behavior of early stage under unsteady state condition has not been explained. Crack energy density (CED), which has been proposed as a parameter that can provide a unified description of crack behavior with no restriction on constitutive equation, can give the general expression about creep crack growth rate. By applying Ct and the concept of CED to the results, we showed that creep crack growth rate for all ranges of creep can be explained in a unified way by CED and its derivatives. Moreover, the physical meaning of the Ct is clarified in the discussion.