13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0 100 200 300 400 500 600 700 800 failure curve of stiffener residual strength of stiffened plate residual strength of non-stiffened plate 1 a' 1 a1 b stiffener as=0.353m a0=0.130m 0=114MPa a, m , MPa (a) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0 100 200 300 400 500 600 700 800 failure curve of stiffener residual strength of stiffened plate residual strength of non-stiffened plate b rib as=0.353m a 0=0.132m 0=141MPa , MPa a, m (b) Figure3. Residual strength diagram of stiffened plate construction of the hull under loading rate MPa m s/ ~106 and temperature 273K (a) and 293K(b) The above analysis with respect to the crack behavior shows that the residual strength of stiffened plate construction has a “platform” stress 0 to which corresponding the range of cracks length s 0a ~a . At this scope, the stiffened plate construction can play a part in crack arrest. Therefore, it can be obtained that the lower limiting value of residual strength of stiffened plate construction is 0 , and the effective range of crack length for crack arrest is s 0a ~a . The stiffened plate construction of the hull analyzed in this paper shows elastic-plastic fracture with large plastic deformation under the loading rate MPa m s/ ~105 and temperature 273K and 293K. At this condition, the stiffened plate construction belongs to a stiffener critical construction (details seen in Figure 2). For example, when the loading rate is MPa m s/ ~105 , the fracture toughness of hull steel are 282 MPa m and 343MPa m under temperature 273K and 293K, respectively. While, under the loading rate MPa m s/ ~106 , the fracture toughness obviously decrease to 71MPa m and MPa m 89 , which is only quarter of the fracture toughness under quasi-static loading rate (seen Table 2). Thus, the residual strength curve of stiffened plate construction decreases largely. As a result, under the loading rate MPa m s/ ~106 , the stiffened plate construction belongs to a skin critical construction (Figure 3). The lower limiting value 0 and the range of crack length for crack arrest s 0a ~a for stiffened plate construction of the hull are listed in Table 3. Table 3 (MPa) 0 and a ~a (m) s 0 of stiffened plate construction of the hull loading rate MPa m s/ ~105 MPa m s/ ~106 temperature (K） 273 293 273 293 (MPa) 0 363 434 114 141 a ~a (m) s 0 0.225-0.279 0.248 0.130-0.353 0.132-0.353 It can be seen from Table 3 that the lower limiting value of residual strength is strongly dependent
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