Pipe Elbows Under Strong Cyclic Loading

Abstract

Motivated by the response of industrial piping under seismic loading conditions, the present study examines the behavior of steel process piping elbows, subjected to strong cyclic loading conditions. A set of experiments is conducted on elbow specimens subjected to constant amplitude in-plane cyclic bending, resulting into failure in the low-cycle-fatigue range. The experimental results are used to develop a low-cycle-fatigue curve within the strain-based fatigue design framework. The experimental work is supported by finite element analyses, which account for geometrical and material nonlinearities. Using advanced plasticity models to describe the behavior of elbow material, the analysis focuses on localized deformations at the critical positions where cracking occurs. Finally, the relevant provisions of design codes (ASME B31.3 and EN 13480) for elbow design are discussed and assessed, with respect to the experimental and numerical findings.

CFRP Reinforcement and Repair of Steel Pipe Elbows Subjected to Severe Cyclic Loading

“…Fracture of the non-reinforced specimens occurred at the crown area due to excessive cyclic strain in the hoop direction, which is in accordance with previous publications [11], [12]. Upon completion of each test on reinforced elbows, a cutting machine was used to cut the pipe elbows transversely at several locations in order to inspect the cracked area of the steel pipe.…”

“…Takakashi et al [10] performed in plane-bending low-cycle fatigue tests on pipe elbows specimens with local wall thinning, due to metal loss from erosion corrosion. More recently, the low-cycle fatigue of pipe elbows, subjected to severe cyclic loading, has been investigated experimentally and numerically by Varelis et al [11], [12]. The recent paper by Karamanos [13] offers an overview of pipe elbow mechanical behavior under severe loading conditions.…”

Simulation of Cyclic Loading on Pipe Elbows Using Advanced Plane-Stress Elastoplasticity Models1

“…al [14] and demonstrated that ratcheting occurs mainly in the hoop direction, while the ratcheting rate grows proportionally with the increase of the applied cyclic-bending amplitude or the internal pressure. Vishnuvardhan et al [15] and Varelis et al [16] [17] reported additional experimental results concerning the cyclic response of pipe elbows. In these studies, low-cycle fatigue failure was due to the development of through-thickness cracking, followed by a pipe cross-section ovalization at the bend.…”

“…In these studies, low-cycle fatigue failure was due to the development of through-thickness cracking, followed by a pipe cross-section ovalization at the bend. In addition, Varelis et al [16] [17] compared the experimental results with design code provisions, highlighting the conservativeness of current design tools in predicting the number of cycles to failure.…”

Ratcheting behavior of pressurized corroded straight pipe subjected to cyclic bending

“…Thus, it was essential to critically evaluate the widely used and recently developed constitutive models against their simulation capability of component responses for determining the state-of-the-art constitutive modeling features and future model development needs. Ratcheting strains of pressurized piping components such as elbow pipe and straight pipe with or without local wall thinning under cyclic loading, have been also studied by experiments and finite element analysis after 2013 [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36].…”