Fracture surface features of polyethylene pipe samples

Abstract

Slow crack growth behavior of medium‐density polyethylene pipe samples has been investigated by applying standard and nonstandard fracture mechanics test methods. Slow crack growth rate varied by several orders of magnitude among the PE2306 materials from different manufacturers. Slow crack generated surfaces exhibit fibrous textures of varying degrees of coarseness when examined under the scanning electron microscope. When the measured fiber heights, δ/2, of these samples were plotted against the applied stress intensity factor, KI, they showed a simple power law relationship (of exponent 2). Assuming that the pulled‐out fibers transmit almost uniform tensile stresses across the crazed zone at the crack front, the Dugdale‐Barenblatt model was introduced to predict the fiber height. Although the model needs further modification, it provides a general power law relationship between the fiber height and the applied stress intensity factor.

Environmental stress cracking of chemically aged HDPE-100 gas pipe under impact fracture mode

“…Therefore, these figures illustrate representative fracture surfaces for AR and aged specimens in DW, AA and HA. Globally, each picture shows a notch strip, a fine razor cut trace, an initiation crack jump followed by one or more striations and a final arret line [10,13]. The inclined dashed arrows ( 1) and ( 2) point to the limits of two main crack jumps in all pictures (Figs.…”

“…Qualitative and even quantitative information can be extracted and may provide valuable information to formulate reasonable interpretations. Although some published work is devoted to the subject of Charpy tests on PE, there remains very little, if any, that relates to the effects of ESC caused by acidic media on HDPE-100 intended for Natural Gas transmission [8,10,13,14]. Figs.…”

“…However, a careful review of the specialized literature relevant to ESC of HDPE pipe does not show any experimental work using arc-shaped specimens chemically aged and tested under impact mode. PE pipe arc-shaped specimens have been mentioned in published studies dealing with standardization and mechanical aspects faraway from chemical ageing effects [13][14][15][16][17]. For instance, it is proposed for SCG a quantitative relationship between the fibrillar texture and corresponding applied load [13].…”

“…PE pipe arc-shaped specimens have been mentioned in published studies dealing with standardization and mechanical aspects faraway from chemical ageing effects [13][14][15][16][17]. For instance, it is proposed for SCG a quantitative relationship between the fibrillar texture and corresponding applied load [13]. Likewise, few approaches are developed for radial impact plane strain fracture toughness parameters based on GIC which is characterized by the elastic critical strain energy release rate or J1C which is characterized by the elasto-plastic J-integral.…”

Transition of neck appearance in polyethylene and effect of the associated strain rate on the damage generation

“…Such a brittle fracture behavior is very different from those reported in Refs. in which whitening occurs at the notch tip before crack growth commences. It should be noted that specimens in the latter studies were always subjected to a constant load at a lower temperature (80°C or below).…”