Issue 50

P. Qiu, Frattura ed Integrità Strutturale, 50 (2019) 300-309; DOI: 10.3221/IGF-ESIS.50.25 306 2 3 1/2 max,T 2 mg 1.5( 10 ) 10 2 ( ) c S IC c P Sa K f th        (3) where ( ) c f  is a function related to the value of / c a h , and its expression is:      2 3/2 1.99 (1 ) 2.15 3.93 2.7 ( ) , 1 2 1- c c c c c c c c c a f h                (4) where the calculation formula of c a is: 1/2 0 0 max, 2 ( )arctan( 0.1135) 32.6 c c T tECMOD a h h h P      (5) where P ini, T stands for the initial crack load, m stands for the weight between the supports of the specimens, which is converted using the total mass of the specimens according to S/L ratio, g is the acceleration of gravity, 9.81 m/s 2 here, S is the span between the two supports of the specimens, 0 a stands for the depth of the notch reserved at the middle and lower parts, t is the thickness of the specimens, h is the height of the specimens, P max, T is the maximum load, c a stands for the effective crack length, 0 h stands for the thickness of the sheet steel plate at the notch, E is the elastic modulus, and CMOD c is the critical value of CMOD. Relationship between Fracture Toughness and Temperature Fig. 7a and b show the relationships of Q IC K and S IC K with temperature. It was seen from Fig. 7 that the general change trend of Q IC K and S IC K decreased with the increase of temperature. a) b) c) Figure 7 : Relationship between fracture toughness and elevated temperature. a) The change of initial fracture toughness with the maximum temperature; b) The change of instability toughness with the maximum temperature; c) The change of the ratio of initial fracture toughness to instability toughness with the maximum temperature.