Issue 30

Yu.G. Matvienko, Frattura ed Integrità Strutturale, 30 (2014) 311-316; DOI: 10.3221/IGF-ESIS.30.38 313 2 2 2 2 1 Y p I I I I p r K D A K r                      (3) Here, some parameters are denoted as follows                              zz zz xx xx I T T T T D 2 cos 16 2 cos 8 2 5 cos 3 2 cos 2         (4)       1 2 cos 4 3 cos 1 21 2          I A (5) Plastic zone sizes can be estimated by the following equations   U WU V V r p 2 4 2 1      ,   U WU V V r p 2 4 2 2      (6) As a result, the plastic crack zone is determined as follows     2 1 2 , p p r positive r r       (7) It should be noted that the value of 1 p r is positive in the wide range of coefficients U , V , W . At the same time, the value of 2 p r has a negative sign. The effect of constraint on the crack tip plastic zone The calculation results of the angular size distribution of the plastic zone around the crack tip in CT specimen with various relations between specimen thickness B and specimen width W are presented in Fig. 2. Figure 2 : The angular distribution of crack tip plastic zone sizes for the middle plane in the CT specimen. The stress intensity factor K I is assumed to be constant independently on specimen thickness and equal to 66 MPa  m 1/2 . Corresponding values of the T -stress components are presented in Tab. 1. Sizes of the plastic zone around the crack tip with provision for the spatial stress state (3D Analysis) are surrounded by sizes of the zones corresponding to two limit