Evaluation of Fracture Toughness Behavior of Polyethylene Pipe Materials

The main purpose of the present paper is to investigate the effect of strain rate, specimen thickness and welding on the fracture toughness. The material of the investigated pipe is a high-density polyethylene, (HDPE) which is commonly used in natural gas piping systems. The welding technique used in this study is butt fusion (BF) welding technique. The crosshead speed ranged from 5 to 500 mm/min and specimen thickness ranged from 9 to 45mm for both welded and unwelded specimens at room temperature, Ta equal 20 °C. Curved three point bend (CTPB) specimens were used to determine KQ. Furthermore, the results of fracture toughness, KQ, will be compared with the plane strain fracture toughness, JIC, for welded and unwelded specimens. The experimental results revealed that KQ increases with increasing the crosshead speed, while KQ decreases as the specimen thickness increases. The investigation reveals that the apparent fracture toughness, KQ, for HDPE pipe of unwelded specimen is greater than that of corresponding value for welded specimen. The same trend was observed for the plane strain fracture toughness, JIc. At lower crosshead speeds there is a minimum deviation in KQ between welded and unwelded specimens, while the deviation becomes larger with increasing crosshead speed.

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Evaluation of Fracture Toughness Behavior of Polyethylene Pipe Materials1

Journal of Pressure Vessel Technology ◽

10.1115/1.4029925 ◽

2015 ◽

Vol 137 (6) ◽

Cited By ~ 4

Author(s):

Tarek M. A. A. EL-Bagory ◽

Hossam E. M. Sallam ◽

Maher Y. A. Younan

Keyword(s):

Fracture Toughness ◽

Plane Strain ◽

Specimen Thickness ◽

Plane Strain Fracture Toughness ◽

Crosshead Speed ◽

Apparent Fracture Toughness ◽

Strain Fracture ◽

Piping Systems ◽

Point Bend ◽

Welding Technique

The main purpose of the present paper is to investigate the effect of crosshead speed, specimen thickness, and welding on the fracture toughness. The material of the investigated pipe is a high density polyethylene (HDPE), which is commonly used in natural gas piping systems. The welding technique used in this study is butt-fusion (BF) welding technique. The crosshead speed ranged from 5 to 500 mm/min and specimen thickness ranged from 9 to 45 mm for both welded and unwelded specimens at room temperature, Ta = 20 °C. Curved three point bend (CTPB) specimens were used to determine KQ. Furthermore, the results of fracture toughness, KQ, will be compared with the plane–strain fracture toughness, JIC, for welded and unwelded specimens. The experimental results revealed that KQ increases with increasing the crosshead speed, while KQ decreases as the specimen thickness increases. The investigation reveals that the apparent fracture toughness, KQ, for HDPE pipe of unwelded specimen is greater than that of corresponding value for welded specimen. The same trend was observed for the plane-strain fracture toughness, JIC. At lower crosshead speeds there is a minimum deviation in KQ between welded and unwelded specimens, while the deviation becomes larger with increasing crosshead speed.

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Validation of Linear Elastic Fracture Mechanics in Predicting the Fracture Toughness of Polyethylene Pipe Materials

Volume 3: Design and Analysis ◽

10.1115/pvp2015-45651 ◽

2015 ◽

Cited By ~ 1

Author(s):

Tarek M. A. A. El-Bagory ◽

Hossam E. M. Sallam ◽

Maher Y. A. Younan

Keyword(s):

Fracture Toughness ◽

Fracture Mechanics ◽

Linear Elastic Fracture Mechanics ◽

Operating Conditions ◽

Specimen Thickness ◽

Crosshead Speed ◽

Linear Elastic ◽

Piping Systems ◽

Elastic Fracture ◽

Point Bend

The main purpose of the present paper is to compare between the fracture toughness based on linear elastic fracture mechanics (GIC), and that based on nonlinear fracture mechanics (JIC). The material of the investigated pipe is a high-density polyethylene (HDPE), which is commonly used in natural gas piping systems. The welds at the pipe junction are produced by butt-fusion (BF), welding. Curved three-point bend (CTPB), fracture specimens are used. The crosshead speed ranged from 5 to 500 mm/min and specimen thickness ranged from 9 to 45mm for both welded and unwelded specimens at room temperature Ta, equal 23°C. The study reveals that the crosshead speed has a significant effect on the fracture toughness of both welded and unwelded specimens. The results of GIC for different specimen thickness and crosshead speed found previously by the authors [1] have been compared with JIC under the same operating conditions [2]. The comparison between welded and unwelded specimens revealed that in the welded specimens there is a marginal difference between fracture toughness measured using linear elastic fracture mechanics LEFM and elastic plastic fracture mechanics EPFM, for both crosshead speeds.

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Critical Stress Intensity Factor Determination for AZ61 Magnesium Alloy

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.462-463.1121 ◽

2011 ◽

Vol 462-463 ◽

pp. 1121-1126

Author(s):

M.A.M. Daud ◽

Zainuddin Sajuri ◽

Mohd Zaidi Omar ◽

Junaidi Syarif

Keyword(s):

Fracture Toughness ◽

Stress Intensity Factor ◽

Stress Intensity ◽

Magnesium Alloy ◽

Intensity Factor ◽

Plane Strain ◽

Specimen Thickness ◽

Plane Strain Fracture Toughness ◽

Az61 Magnesium Alloy ◽

Strain Fracture

A stress intensity factor K was used as a fracture parameter to determine the plane strain fracture toughness KIC of AZ61 magnesium alloy using a single edge notch bend (SENB) specimen in accordance to ASTM E399 testing method. Five different specimen thicknesses of 2 to 10 mm were used in the test. A sharp fatigue pre-crack was initiated and propagated to half of specimen width at a constant crack propagation rate of about 1 x 10-8 m/cycle before the specimen was loaded in tension until the fracture stress is reached and then rapid fracture occurred. The fracture toughness KC values obtained for different thicknesses showed that KC value decreased with increasing specimen thickness. The highest KC value obtained was 16.5 MPa√m for 2 mm thickness specimen. The value of KC became relatively constant at about 13 MPa√m when the specimen thickness exceeds 8 mm. This value was then considered as the plane strain fracture toughness KIC of AZ61 magnesium alloy. Calculation of the minimum thickness requirement for plane strain condition and the size of the shear lips of the fracture surface validate the obtained KIC value.

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