Issue 39

M. Shariati et alii, Frattura ed Integrità Strutturale, 39 (2017) 166-180; DOI: 10.3221/IGF-ESIS.39.17 176 The influence of the change in the material gradient parameter P on the value of stress intensity factor K I is considered. The values of SIF for different crack length are plotted (in Fig. 8) versus P . For P 0 the constituent material of the cylinder is pure epoxy. Fig. 8 shows that for large cracks the stress intensity factor decreases with increasing P , while for cracks which their lengths are less than half of the wall thickness of the cylinder, the SIF curves are downward for P 0.5 approximately, and for larger values of P the SIF curves are upward. [ 3 . , 3D P a =0.01 a =0.03 a =0.05 a =0.07 Figure 8 : SIF vs. P curves for different values of circumferential crack length. To study the effect of the rotational speed of cylinder on the SIF of circumferential crack, cylinders with different circumferential crack length under various rotational speed are considered. For this purpose, the stress intensity factors are calculated for different values of rotational speed of cylinders, which vary from 100 to 1900 rpm. In these analysis the value of material gradient parameter is selected to P 0.2 . The SIF vs. rotational speed of cylinder curves for different values of crack length are illustrated in Fig. 9. As expected, the stress intensity factor increases with increasing rotational speed because the radial component of body force is proportional to the square of rotational speed of cylinder. [ 530 . , 3D P a =0.09 a =0.07 a =0.05 a =0.03 a =0.01 Figure 9 : SIF vs. rotational speed of cylinder curves for different values of circumferential crack length. The longitudinal displacement and stress contours for an axisymmetric cross section of a hollow cylinder with a circumferential crack of length 0.05 m under rotational speed of 1800 rpm are illustrated in Fig. 10.