Limit Load of Pre-Cracked Polyethylene Miter Pipe Bends Subjected to In-Plane Bending Moment

Abstract

The main purpose of the present paper is to investigate the effect of crack depth on the limit load of miter pipe bends (MPB) under in-plane bending moment. The experimental work is conducted to investigate multi miter pipe bends, with a bend angle 90°, pipe bend factor h = 0.844, standard dimension ratio SDR = 11, and three junctions under a crosshead speed 500 mm/min. The material of the investigated pipe is a high-density polyethylene (HDPE), which is used in natural gas piping systems. The welds in the miter pipe bends are produced by butt-fusion method. The crack depth varies from intrados to extrados location according to the in-plane opening/closing bending moment respectively. For each in-plane bending moment the limit load is obtained by the tangent intersection (TI) method from the load deflection curves produced by the testing machine specially designed and constructed in the laboratory. The study reveals that increasing the crack depth leads to a decrease in the stiffness and limit load of (MPB) for both inplane closing and opening bending moment. Higher values of the limit load are reached in case of opening bending moment. This behavior is true for all investigated crack depths.