ICF13B

13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Calculation of bearing loads for fractured specimens by FRASTA simulation Yuguang Cao1,*, Shihua Zhang1, Xiaoyu Sun2, Kiyoshi Tanaka3 1 Department of Engineering Mechanics, China University of Petroleum, 266580, China 2 Drilling Technology Institute of Shengli Petroleum Bureau, 257017, China 3 Department of Mechanical Systems Engineering, Toyama Prefectural University, 939-0398, Japan Abstract Based on the previously proposed simple bar hypothesis, the fracture surfaces can be assumed to be composed of independent rectangular bars. In this paper, by dividing the plastic deformation into single bars, the original lengths of these bars were deduced and then the global strains of these bars during the course of failure were calculated. According to the relationship between true stress and true strain of the material, the normal stress on the cross section of each bar was determined. Multiply the stress with the cross section area, the load acted on each single bar was obtained. Adding all loads on all bars together led to the total applied load of the specimen. Keywords Fracture surface; FRASTA; Fatigue load 1. Introduction To investigate the fractured surfaces always reveals a lot of useful information. For example, details of the processes that lead to failure can be determined from these surfaces, making it useful to investigate their morphology. In order to investigate the reasons for a material’s failure, it is necessary to know the temperature, environment and load imposed on it. Since these records are often unavailable, the reasons for failure must be deduced by analyzing fracture surfaces. Dr. Kobayashi firstly proposed fracture-surface topography analysis (FRASTA) in 1987 [1]. FRASTA considers that as the crack extends, the material immediately beneath the newly formed fracture surfaces undergoes no further inelastic deformation. Based on this understanding, the process of fracture can be rebuilt from the conjugate fractured surfaces. Using the FRASTA technique, the details of the void nucleation and growth, the coalescence of the voids and cracks, and the crack propagation process can be clarified visually [2]. However, the FRASTA application has previously focused on smaller size scales and localized behaviors [3]. A novel method [4] of measuring the CTOA and determining the J integral using FRASTA was proposed in 2006. It extended the application of FRASTA to global fracture surfaces. Software [5] was developed for researching the global fracture surfaces based on this principle. The relationship between J integral and fracture surface average profile [6] and the relationship between J integral and COD [7] were proposed respectively based on FRASTA reconstruction. The main goal of this paper is to propose a new method to calculate the specimen applied load during failure from the fracture surfaces. Based on the above researches especially the proposed simple bar hypothesis, the fracture surfaces will be divided into independent rectangular bars. The calculation of elongation, global strain, cross-section normal stress and so on of these bars will be deduced. By adding the applied force of each bar together, the total applied force of the specimen during the course of failure will be derived. 2. Method for calculating the applied loads of fractured specimens

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