13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Effects of loading rate and temperature on crack arrest behavior of hull steel in stiffened plate construction Chunhuan Guo, Yanmei Song, Fengchun Jiang* and Ruitang Liu Key Laboratory of Superlight Materials & Surface Technology of Ministry of Education Harbin Engineering University, Harbin 150001, P.R. China * Corresponding author: fengchunjiang@hrbeu.edu.cn Abstract Based on the residual strength diagram of non-stiffened plate construction, a residual strength diagram of hull steel in stiffened plate construction was proposed using the linear-elastic fracture mechanic theory in this work, the effects of loading rate and temperature on the crack arrest behavior of the stiffened plate construction were discussed, the lower limit of the residual strength and the dimension of a valid arrested crack were obtained via the theoretical analysis. The results demonstrated that, whether loading rate or temperature significantly influence the lower limit of the residual strength of the hull steel in a stiffened plate construction; under the conditions of 273K and 293K, the stiffened plate construction is a stiffener critical construction when the applied loading rate K is in the order of MPa m s/ ~105 , while under the loading rate of MPa m s/ ~106 , it becomes a skin critical construction due to the decrease of the fracture toughness of the full steel, the lower limit of residual strength is reduced to one fourth of the steel yield strength under this loading condition. In this case, the stiffened shipping construction is no longer adaptable to such a high loading rate, the crack arrest design is therefore highly desirable for protecting the full plate construction. Keywords stiffened plate, residual strength, crack arrest, loading rate and temperature effect 1. Introduction In order to enhance strength and stiffness, the stiffened plate construction is always often used in the structure design of the hull. Therefore, it must be considered the effect of stiffener when analyzing the deformation and fracture behavior of hull structure. Vliege and Brock studied the crack propagation behavior and crack arrest characteristic in stiffened plate structure of the plane, and proposed the residual strength diagram of non-stiffened plate structure to analyze and predict the crack propagation characteristic of the stiffened plate structure [1, 2]. The design of crack arrest is an important aspect of ship design, while the study associated with of the crack arrest behavior of hull steel under dynamic loading is quite limited at present. The ships especially naval vessels are often subjected to impact load in their service processing. The fracture toughness of hull steel may be reduced due to the effect of high loading rate, for example, the fracture toughness (KIC) of hull steel used in this paper is MPa m ~180 (loading rate MPa m s/ ~100 ) under the temperature ~273K, while the fracture toughness decreases to MPa m ~64 under the loading rate MPa m s/ ~106 ,which is one third of static fracture toughness. Thus, it is essential to design ships in terms of crack arrest principle. Based on the linear-elastic fracture mechanic theory and residual strength diagram (when temperature is 273K, MPa m s/ ~105 and 293K, MPa m s/ ~106 ) of the hull, the present paper discusses the crack arrest behavior of the stiffened plate structure of the hull, the conclusions drawn from this work can be used as the reference for the design of crack arrest of the hull steel.
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