13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Three-Dimensional Vacancy Diffusion Analysis Related to Micro Damage of C(T) Specimen for P92 Steel under Creep Condition Haruhisa Shigeyama1,*, A. Toshimitsu Yokobori, Jr.1, Ryuji Sugiura1, Takashi Matsuzaki1 1 Department of Nanomechanics, Tohoku University, Sendai 980-8579, Japan * Corresponding author: shigeyama@md.mech.tohoku.ac.jp Abstract In this study, interrupted creep crack growth tests were conducted using C(T) specimens with side-grooves of P92 steel. After the interrupted tests, to investigate the creep crack growth behavior of P92 steel under the multi-axial stress field, the creep crack growth path of the center of the thickness direction and near the side-groove were observed. From observational results, it was indicated that the creep crack preferentially grew near the side-groove. Additionally, creep crack growth forms were different between the center of the thickness direction and near the side-groove. For the center of the thickness direction, the creep crack growth behavior showed the periodic convexo-concave manner. On the other hand, the creep crack grew in a linear manner near the side-groove. To mechanically clarify the difference of creep crack growth forms, three-dimensional diffusion analysis of vacancies which related to the void formation and crack growth was conducted. From analytical results, vacancies accumulated at the corner of the bottoms of notch and side-groove. This result is in good agreement with the experimental result. Keywords P92 steel, C(T) specimen, Interrupted test, Creep crack growth, Three-dimensional stress induced vacancy diffusion analysis 1. Introduction The W-strengthened 9%Cr ferritic heat-resistant steel (ASME code case 2179, ASTM A335 P92) has been developed as a boiler material for the ultra-supercritical power plant. When a component is used in the actual plant, the multi-axial stress field is caused due to the complicated three-dimensional structure. It is known that the ductility of materials decrease with increasing the multi-axial stress and this phenomenon is called “structural brittleness” [1, 2]. The reduction of ductility makes the lifetime-prediction difficult. Therefore, it is important to clarify the creep damage progression behavior of P92 steel under the multi-axial stress field. It is reported that the initiation and growth of creep voids are accelerated due to the multi-axial stress field [3-6]. Additionally, the initiation and growth of creep voids were caused by the diffusion and accumulation of vacancies. Thus, it is necessary to clarify the diffusion behavior of vacancies under the multi-axial stress field. Actually, some authors proposed the numerical analytical method of two-dimensional stress induced vacancy diffusion [7-10]. In this study, interrupted creep crack growth (CCG) tests were conducted using C(T) specimens with side-grooves of P92 steel. After the interrupted tests, to investigate the CCG behavior of P92 steel under the multi-axial stress field, the CCG path of the center of the thickness direction and near the side-groove were observed. Then, three-dimensional stress induced vacancy diffusion analysis was conducted to clarify the diffusion behavior of vacancies for C(T) specimen with side-grooves.
RkJQdWJsaXNoZXIy MjM0NDE=