Experimental investigation of the instability of high density polyethylene (HDPE) tubes under axial compression and internal pressurization

• Grant number: 12/10274-8
• Support Opportunities: Regular Research Grants
• Start date: March 01, 2013
• End date: August 31, 2014
• Field of knowledge: Engineering - Mechanical Engineering - Mechanics of Solids
• Principal Investigator: Celso Pupo Pesce
• Grantee: Celso Pupo Pesce
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated researchers: Roberto Ramos Júnior

Abstract

The increasing use of flexible pipes in oil and gas exploitation has raised studies, seeking technological solutions to problems of structural stabilities in these kind of pipes. Structural stabilities and failures that can arise are important aspects regarding environmental e economics issues. The failure of a flexible pipe leads to a possible leak of fluid, which will cause devastating environmental damage and high economic costs. Among the possible failure modes caused by local instability in flexible pipes, one, called birdcaging, occurs in pressure armor when the flexible pipes are subject to compressive loads and internal pressure. This kind of structural failure is appears externally through the formation of a "bubble" in the external polymeric layer that protects the pressure armor. This layer consists, in general, of a HDPE tube extruded over the reinforced bandages that involves the pressure armors. A conjecture proposes that the elasto plastic instability of the external layer, associated with the interfacial pressure exerted on it by the pressure armor, controls the birdcaging phenomenon. The bibliographical search did not allowed to discover detailed studies concerning HDPE tubes. Hence, specific experiments will be carried out in order to study HDPE tubes instability failures, under compressive load, controlled by displacement, and internal pressurization. A flexible device which allows the use of different diameters and thickness will be developed as well as the appropriate methodology. A pressurization system ( using water) and an acquisition data system will be used to register data and connect the test machine ensuring the same time base. Complementing, the HDPE mechanical properties will be experimentally determined using the ordinary standard tests and an ultrasonic technique. These experiments are part of the doctoral research of Eng. Marcos Alves Rabelo, funded by CAPES scholarship. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

RABELO, MARCOS A.; PESCE, CELSO P.; SANTOS, CAIO C. P.; JUNIOR, ROBERTO RAMOS; FRANZINI, GUILHERME R.; NETO, ALFREDO GAY. An investigation on flexible pipes birdcaging triggering. MARINE STRUCTURES, v. 40, p. 159-182, JAN 2015. (12/10274-8)