Microstructure and Mechanical Properties of the Butt Joint in High Density Polyethylene Pipe

Abstract

The microstructure and mechanical properties of the butt joint in high density polyethylene (HDPE) pipes were evaluated by preparing the joints with increasing the cooling time from 10 s to 70 s before pressure created for fusion of the pipes. Here, cold fusion flaws in HDPE butt joint were created with increasing the cooling time around 70 s caused by the close molecular contact followed by insufficient interdiffusion of chain segments back and forth across the wetted interface. The tensile failure mechanism of the welded pipes at different fusion time was projected based on the tensile test of dog-bone shaped, fully notched bar type as well as round U-notched specimens. The mechanical properties of the joints at different fusion time were correlated with the corresponding fracture surface morphology. The weld seam as well as tensile fracture surfaces were etched using strong oxidizing agents. The crystallinity of surface etched weld zone by potassium permanganate based etchant was found higher than unetched sample due to the higher susceptibility of amorphous phase of polyethylene with oxidizing agent. The U-notched tensile test of butt welded HDPE pipe and surface etching of the weldments provided clear delineation about the joint quality.

High-Density Polyethylene Pipe Butt-Fusion Joint Detection via Total Focusing Method and Spatiotemporal Singular Value Decomposition

“…High-density polyethylene (HDPE) pipes, due to good chemical properties and mechanical strength, such as corrosion resistance, toughness, long service life, etc., have been widely used in urban natural gas supply system [1][2][3]. In the process of urban gas transportation, several HDPE pipes need to be connected, and joint welding using the thermal butt-fusion technique is a common means of pipes connection [4,5]. Butt-fusion joints are the weakest link of the HDPE pipes, which determine the safety performance of the whole pipeline system.…”

Investigation of Creep Behavior of HDPE Pipe Butt Fusion Welded Joints Using a Stepped Isostress Method

“…Various methods have been proposed for evaluating the mechanical properties of welded joints. Tensile and burst tests can be utilized to evaluate the short-term mechanical properties of welded joints [10][11][12][13]. Moreover, when it comes to assessing the effect of welding defects on the long-term performance of welded joints, the creep test proves more effective than hydrostatic testing [14][15][16].…”

Exciting and Detecting Higher-Order Guided Lamb Wave Modes in High-Density Polyethylene Structures Using Ultrasonic Methods

“…Timely detection of defects prevents complicated troubleshooting. In order to maintain the safety of devices/structures, effective and economical diagnostic methods are needed [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. In the literature reviewed, most of the methods used for diagnosing defects were applied to the steel pipes.…”