Thermoelastic Crack Analysis in Functionally Graded Pipelines Conveying Natural Gas by an FEM

Abstract

Internal cracks are a serious problem in pipelines conveying unsteady pressurized fluids like natural gas. To investigate and overcome this problem, this paper is motivated to highlight and study the response of gas pipes made of functionally graded materials (FGM) instead of the traditional carbon steel material. FGM is proposed as a composite material because of its advantages of minimizing the stress variation in the pipe. Ceramic is applied because of its durability against corrosion and its surface hardness against erosion. FGM properties are radially graded and a finite element model is developed and implemented into ABAQUS package, including FORTRAN subroutines which are adapted for the present case study. Coupled plane strain thermoelastic analysis is used to investigate the stresses and the stress intensity factor (SIF) at various crack depths under the actual thermomechanical loads. Both coupled and uncoupled thermomechanical approaches are introduced and compared to reveal the necessity of the coupled analysis for accurate FGMs’ investigation. The different influences of unsteady thermal and mechanical loads on the crack propagation are discussed.

The effect of variable properties and rotation in a visco-thermoelastic orthotropic annular cylinder under the Moore–Gibson–Thompson heat conduction model

“…When equations (3) and (5) are combined together, we obtain a linear form of the heat conduction equation which is based on the generalized Moore–Gibson–Thompson (MGTE) thermoelasticity 28,38 for isotropic material. The theory of MGTE is the generalization of the theory of Lord–Shulman (LS) 10 and of type III Green–Naghdi theory of thermoelasticity (GN-III) 28,38 …”

“…The generalized heat conduction equation of Moore–Gibson–Thompson (MGTE) (modified Fourier’s law) is in the following form 28,38 …”

“…[29][30][31][32][33][34][35] The theoretical study of the thermoelastic and mechanical behavior of different structures have successfully been applied in recent years. [36][37][38][39][40][41][42][43][44][45] Due to a wide variety of microphysical processes, viscoelasticity is of great interest to various applications and can be used as an experimental test for those processes. The Boltzmann superposition theory is extended to the linear viscoelastic governing equations.…”