Journal of Stress Analysis Vol. 4, No. 1, Spring - Summer 2019 Numerical and Experimental Analysis of the Efects of Crack on Vibration Characteristics of GFRP-stifened Pipes M.H. Velayatparvardeh, A. Shooshtari * Department of Mechanical Engineering, Faculty of Engineering, Bu-Ali Sina University, Hamedan, Iran. Article info Article history: Received 28 May 2019 Received in revised form 10 September 2019 Accepted 17 September 2019 Keywords: Composite pipe GFRP pipe Love theory Vibration Natural frequencies Mode shapes FRF: (Frequency Response Func- tion) Abstract In this paper, the vibration characteristics of GFRP-stifened pipes, in intact and cracked conditions are investigated. The results have diferent applica- tions, which the most important ones are optimized designs of such pipes and diagnosis of the damage in them. Therefore, by Love theory, governing equa- tions of motion for the GFRP-stifened pipes were obtained. Having obtained characteristic equation, the natural frequencies of the problem were calculated for intact case. Then by modeling a sample of these pipes in the ANSYS soft- ware and using Modal analysis, natural frequencies and related mode shapes due to fnite element method were calculated in cracked and intact condi- tions. Then by using the experimental modal analysis method, the natural frequencies of a sample, which was built similar to these pipes, were obtained in cracked and intact conditions. The results of the analytical method, fnite element method, and the experimental modal analysis were compared and it was shown that the results have a good compatibility. The same process was performed on carbon fber composites. Nomenclature u, v, z Displacement of plate in x, y and z direction u 0 ,v 0 ,w 0 Displacement of middle plate in x, y and z direction G xy ,G yz ,G xz Shear deformation modules E xx ,E yy ,E zz Elasticities modules A ij ,B ij ,D ij ¯ A IJ , ¯ B IJ , ¯ D IJ ˆ A IJ , ˆ B IJ , ˆ D IJ Coefcients of stifness matrix σ α ,σ β ,σ αβ σ βα ,σ αz ,σ βz (α,β,z) Stresses of plate Coordinate axes on top of plate ε 0α ,ε 0β ,γ 0αβ γ 0βα ,γ 0αz ,γ 0βz Strains of mid-plate ϑ xy ,ϑ yx ,ϑ yz ϑ zx ,ϑ yz ,ϑ zy Poisson ratios K α ,K β K αβ ,K βα Curvatures of the plate ε α ,ε β ,γ αβ γ βα ,γ αz ,γ βz Strains of the plate N α ,N β ,N αβ N βα ,Q α ,Q β Internal forces of the plate M α ,M β ,M αβ M βα ,P α ,P β Internal moments on the plate T Kinetic energy of plate q α ,q β ,q z Forces on cylindrical shell I i Inertia momentum of plate ρ (K) K th layer density * Corresponding author: A. Shooshtari (Associate Professor) E-mail address: shooshta@basu.ac.ir http://dx.doi.org/10.22084/jrstan.2019.18794.1091 ISSN: 2588-2597 99