Fatigue Crack Growth in Thin-Wall Pipes Subjected to Bending

Subject Areas : Mechanical Engineering

MohammadMahdi  Amiri ¹ (Department of Engineering, Research Institute of Petroleum Industry)

Received: 2018-12-22 Accepted : 2019-05-10 Published : 2019-06-01

Keywords: Semi-Elliptical Crack, Thin-Wall Pipes, K (Stress Intensity Factor), Fatigue Crack Growth,

Abstract :

In this paper, a circumferential external surface flaw in a metallic round pipe under cyclic bending loading is considered. Because of very rapid changes in the geometrical parameters around the crack front region, the mesh generation of this region must be done with great care. The analysis of the fatigue crack growth is done in accordance with Paris law. The spread lane of the exterior defect is achieved from the graph of “α” vs. “relative crack depth”. The growth of fatigue crack is also analyzed (the comparative crack depth against loading runs diagram) with various initial crack “α” beneath periodic loading. Fatigue shape growth of primarily semi-elliptical peripheral surface flaws is shown. The weight of the Paris exponent (material constant) on fatigue crack propagation is presented as well. Furthermore, the “fatigue crack growth” progression of several specimens is evaluated experimentally by employing a manually-constructed experimental setup. Conclusively, the experimental results achieved by periodic bending loading tests are compared with the numerical results. Fatigue shape development of initially semi-elliptical external surface defects is illustrated. The effect of the Paris exponent (material constant) on fatigue crack propagation is shown as well. Moreover, the fatigue crack growth of several specimens is assessed experimentally using a manually-constructed experimental set up. Finally, the experimental results obtained by cyclic bending loading tests are compared.

References:

[1]    Shahani, A. R., Habibi S. E., Stress Intensity Factors in Hollow Cylinder Containing a Circumferential Semi-Elliptical Crack Subjected to Combined Loading, International Journal of Fatigue, Vol. 291, No. 1, 2007, pp. 128–140. doi: 10.1016/j.ijfatigue.2006.01.017.

[2]    Lin X. B., Smith, R. A., Fatigue Growth Prediction of Internal Surface Cracks in Pressure Vessels, International Journal od Press Vessel Technology. Vol. 120, No. 1, 1998, pp. 17–23, doi:10.1115/1.2841878.

[3]    Underwood J., Stress Intensity Factor for Internally Pressurized Thick-Walled Cylinders: Stress Analysis Growth Cracks, ASTM STP, Vol. 513, 1972, pp. 59–70.

[4]    Raju, I. S., Newman, J. C., Stress-Intensity Factor for Internal and External Surface Cracks in Cylindrical Vessels, International Journal of Press Vessel Technology., Vol. 104, No. l, 1982, pp. 293–298.

[5]    Couroneau, N., Royer, J., Simplified Model for the Fatigue Growth Analysis of Surface Cracks in Round Bars Under Mode I, International Journal of Fatigue, Vol. 20, No. 10, 2010, pp. 711–718, doi:10.1016/S0142-1123(98)00037-1.

[6]    Carpinteri, A., Brighenti R., A Three-Parameter Model for Fatigue Behavior of Circumferential Surface Flaws in Pipes, International Journal of Mechanical Science, Vol. 42, No. 7, 2000, pp. 1255–1269, doi:10.1016/S0020-7403(99)00083-1

[7]    Pook, L. P., On Fatigue Crack Paths, International Journal of Fatigue, Vol. 17, No. 1, 1995, pp. 5–13, doi:10.1016/0142-1123(95)93045-4.

[8]    Carpinteri, A., Brighenti, R., and Spagnoli, A., Part-Through Cracks in Pipes Under Cyclic Bending, Nuclear Engineering and Design., Vol. 185, No. 1, 1998, pp. 1–10, doi:10.1016/S0029-5493(98)00189-7.

[9]    Bergman, M., Stress Intensity Factors for Circumferential Surface Cracks in Pipes, Fatigue & Fracture of Engineering Materials & Structures, Vol. 18, No. 10, 1995, pp. 1155–1172. doi:10.1111/j.1460-2695. 1995.tb00845. x.

[10] Peng. D., Wallbrink, C., and Jones, R., An Assessment of Stress Intensity Factors for Surface Flaws in a Tubular Member, Engineering Fracture Mechanics, Vol. 72, No. 3, 2005, pp. 357–371. doi: 10.1016/j.engfracmech.2004.04.001.