Abstract
The main purpose of the present paper is to investigate the effect of crack depth on the plastic load (collapse load) of miter pipe bends (MPB) under in-plane bending moment. The experimental work is conducted to investigate multimiter pipe bends, with a bend angle 90 deg, pipe bend factor h = 0.844, standard dimension ratio (SDR) = 11, and number of welding junctions m = 3 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 (NG) 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 plastic 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. 5 The study reveals that increasing the crack depth leads to a decrease in the stiffness and plastic load of MPB for both in-plane closing and opening bending moment. Higher values of the plastic load are reached in case of opening bending moment. This behavior is true for all investigated crack depths. A circumferential external crack has an obvious effect on the behavior of load-deflection curve. The linear elastic region in both mode of loading decreases with increasing crack depth.