Numerical research of elastic-plastic fracture toughness of aged ferritic-martensitic steel

Experimental test methods are used to determine material properties and fracture parameters. However, due to cost, lack of test material, etc., experimental tests cannot always be conducted. Therefore, there is a need for alternative methods to determine material properties and fracture parameters. In this paper, a numerical methodology for determination of the elastic-plastic fracture toughness of steel P91 is suggested. For this purpose the universal finite element software ABAQUS was used. J-integral resistance curves (J-R) were constructed by numerical simulation of tension experiment of compact tension (CT) specimen and by using the suggested quadratic polynomial expression for the calculation of the crack length extension of steel P91. The suggested method was validated by experimental tests. The secondary aim of the work is to evaluate the ageing effect on the elastic-plastic fracture toughness of steel P91. Thermal ageing of the steel was carried out in an electric furnace at 600, 650 and 700 degrees C for up to 20 000 h. Research has revealed that J(Q) values decrease by up to 20%, determined experimentally, and by up to 22%, determined numerically, when the steel is aged up to similar to 10900 h at 650 degrees C.