13th International Conference on Fracture June 16–21, 2013, Beijing, China 1 Analysis of Creep Crack Growth in Surface Cracked Specimens: Comparisons between Approaches of Fracture Mechanics and Continuum Damage Mechanics Jian-Feng Wen, Shan-Tung Tu* Key Laboratory of Pressure Systems and Safety (Ministry of Education), School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, PR China *Corresponding author: sttu@ecust.edu.cn Abstract The numerical approaches to simulate creep crack growth can be divided into two different categories. The first category is employing conventional fracture mechanics, in which the rate of crack growth is predicted by correlating it with a fracture mechanics parameter. The second category gaining much attention is on the basis of damage mechanics concept. In this paper, three dimensional analyses of creep crack growth are performed for 316 stainless steel specimens subjected to tension at high temperature with a semi-elliptical surface crack. Using two independent finite element analyses based on the fracture mechanics and continuum damage mechanics respectively, crack growth behaviors including crack profile development, crack size and propagation time are investigated and compared with each other and corresponding experimental data. The comparisons enable to show the different capabilities of the two approaches in predictions of creep crack growth. Keywords Creep crack growth, Fracture mechanics, Continuum damage mechanics, Finite element analysis 1. Introduction The increased computational power and programming capabilities have given impetus to the numerical prognoses of the structural integrity and service-ability throughout the lifetime of structures at high temperature. During the past decades, the numerical approaches to simulate creep crack growth have developed into two different groups. The first group is employing conventional fracture mechanics, in which the crack growth rate is predicted by correlating it with a fracture mechanics parameter such as stress intensity factor or C*-integral [1-4]. The second group is based on damage mechanics concept [5]. When the creep damage variable reaches a critical value, material failure is considered to occur, and thus crack growth can be characterized by a completely damaged element zone ahead of the initial crack tip [6-9]. Alternatively, a node-release technique has been employed to simulate the separation of the crack face [10-14]. However, little research has been successfully conducted in applying the two approaches to three dimensional analysis of creep crack propagation. Furthermore, there is a need for a better understanding of the different capabilities of the two approaches in predictions of crack growth under creep conditions. In this paper, three dimensional analyses of creep crack growth are performed for 316 stainless steel specimens subjected to tension at high temperature with a semi-elliptical surface crack. Section 2 briefly describes the conventional fracture mechanics models and a damage-based model recently proposed by the authors. The main idea of the two approaches in conjunction with the finite element (FE) method is demonstrated in Section 3. Subsequently, Section 4 shows the comparisons of
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