Issue 39

M. Shariati et alii, Frattura ed Integrità Strutturale, 39 (2017) 166-180; DOI: 10.3221/IGF-ESIS.39.17 179 [ 7LPH PLFURVHFRQG . , 3D P 3 3 3 3 3 Figure 14 : Plots of SIF vs. time for circumferential crack embedded in an epoxy/glass cylinder under impulsive tension. C ONCLUSIONS n this study, equations of motion in cylindrical coordinate system were solved using the XFE and Newmark’s methods in functionally graded materials. The stress intensity factors for penny-shaped and circumferential cracks in the epoxy/glass circular cylinders under static and dynamic loading conditions were computed using the interaction integral method. Finally, the following results were obtained from this research: 1- Increasing the crack radius increases the stress intensity factor. 2- Wave arrival time to the crack tip decreases with increasing crack radius. 3- For hollow cylinders with large circumferential crack sizes ( o i a R R / 0.5 ! ), the stress intensity factor decreases with increasing the material gradient parameter P (increasing glass inclusion). 4- For hollow cylinders with circumferential 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. 5- Increasing the rotational speed of the cylinder increases the stress intensity factor. 6- The SIF increases with increasing the inner radius of hollow cylinder. However, for small crack sizes, the effect of inner radius on SIF value is small. 7. For epoxy/glass hollow cylinders with circumferential cracks under impulsive tension, increasing the material gradient parameter P decreases the maximum SIF value so long as P 1 while for P 1 ! the maximum SIF value increases with increasing P . In addition, the speed of stress wave decreases with increasing P . R EFERENCES [1] Walters, M.C., Paulino, G.H.; Robert, H.D.Jr. , Computation of mixed-mode stress intensity factors for cracks in three-dimensional functionally graded solids, J. Eng. Mech., 132(1) (2006) 1-15. Doi: 10.1061/(ASCE)0733-9399(2006)132:1(1). [2] Moulick, S.K., Sahu, Y.K., Stress intensity factor for internal cracks in thick walled pressure vessels using weight function technique, National conference on innovative paradigms in engineering & technology (NCIPET), Proceedings published by International Journal of Computer Applications (IJCA), 10 (2012) 6-12. [3] Meshii, T., Watanabe, K., Closed form stress intensity factor of an arbitrarily located inner-surface circumferential crack in an edge-restraint cylinder under linear radial temperature distribution, Eng. Frac. Mech., 60(5) (1998) 519- 527 DOI: 10.1016/S0013-7944(98)00046-0. I