Experimental Study of Crack Growth in HDPE PE100 Pipes

2013 ◽  
Author(s):  
Raul Machado ◽  
Marco Gonzalez ◽  
Jeanette Gonzalez
Keyword(s):  
Experimental Study ◽  
Crack Growth ◽  
Extrusion Process ◽  
Mechanical Tests ◽  
Piping System ◽  
Type Specimens ◽  
Fracture Characterization ◽  
Elastic Plastic ◽  
Operation Conditions ◽  
Hdpe Pipes

The operation conditions of a piping system such as impact loads, cyclic loadings and discontinuities cause damages, cracking or weakening in the material. The High Density Polyethylene (HDPE) is amply used in the fabrication of pipes due to its versatility, low cost and lightweight. In this study, an experimental study of fracture mechanics of HDPE PE100 specimens obtained directly from extruded pipes is developed. The research is aimed at characterizing the pipe mechanical behaviour under operation loadings, for which elastic-plastic mechanical tests under the ASTM D-5045, E-1820, E-399 and E-813 standards and ESIS protocol are carried out. The influence of the orientation induced by the extrusion process (circumferential or longitudinal direction) on pipes fracture resistance is established. SENB type specimens (three point bending) are used for the fracture characterization and J-R Curves (J vs. Δa) for elastic-plastic analysis are generated according to ESIS protocol. The PE100 fracture characterization throughout the J vs. Δa curves indicates that in both circumferential and longitudinal directions require similar quantities of energy to generate new fracture surfaces on HDPE pipes. Indeed, the orientation of the polymer chains as a result of pipe extrusion process could be not so relevant for predicting the direction of crack growth in HDPE pipes.

Calibration of the AC Potential Dropping System (ACPD) for Determination of Crack Growth in API 5L X65 Steel under Cathodic Protection Effect

2020 ◽  
Vol 1012 ◽  
pp. 412-417
Author(s):  
Misael Souto de Oliveira ◽  
Antonio Almeida Silva ◽  
Marco Antonio dos Santos ◽  
Jorge Antonio Palma Carrasco ◽  
João Vitor de Queiroz Marques
Keyword(s):  
Crack Growth ◽  
Marine Environment ◽  
Cathodic Protection ◽  
Sea Water ◽  
Potential Drop ◽  
Mechanical Tests ◽  
Flow Density ◽  
Type Specimens ◽  
X65 Steel ◽  
Api 5L X65 Steel

In this work the calibration of an Alternative Current Potential Drop (ACPD) system was performed to monitore laboratory mechanical tests on marine environment under cathodic protection. The calibration was done on CT type specimens of API 5L X65 steel dimensioned according to ASTM E1820 standard., The crack propagation during a tensile test with displacement control in an ACPD equipment was monitored through the performs points collection by two channels: one that monitors the crack growth and another that monitors a region free of crack. Using a profile projector and graphical data processing and analysis software, the area of ​​the fracture surface of the specimen was meansured, which allowed to correlate a crack size with a corresponding value of potential drop and the calibration curve. In order to verify verify the efficacy and precision of the technique, step loading tests were performed on API 5L X65 steel test specimens, submerged in synthetic sea water under the overprotection potential of-1300mVAg/AgCl. The results of the calibration showed few dispersed errors, and the main factors of this dispersion may be related to the geometry of the specimen and with variations in current flow density, which is influenced by corners and edges and by the presence of pick-up inductive. The calibration and its effectiveness can be verified through the results of the tests in marine environment, presenting crack lengths close to the actual values, confirming the effectiveness of the ACPD technique.

scholarly journals Life-time prediction for aviation GTE compressor disk based on mixed-mode and multi-axial fracture resistance parameters

2019 ◽  
Vol 300 ◽  
pp. 11001
Author(s):  
Valery Shlyannikov ◽  
Ivan Ishtyryakov ◽  
Rustam Yarullin
Keyword(s):  
Crack Growth ◽  
Structural Integrity ◽  
Growth Models ◽  
Process Zone ◽  
Life Time ◽  
Elastic Plastic ◽  
Time Prediction ◽  
Operation Conditions ◽  
Nonlinear Stress ◽  
Compressor Disk

This study is concerned with analysis of fatigue crack growth and life-time prediction for aviation GTE compressor disk under operation conditions. For consideration were different combinations of rotational speed, temperature, surface flaw form and sizes as well as elastic-plastic titanium alloy BT3-1 properties are employed. A crack growth rate equation is derived involving the fracture process zone size and nonlinear stress intensity factor. The assessments of the structural integrity of the rotating disk are compared for elastic and elastic-plastic solutions. It is stated that the traditional elastic crack growth models overestimate the residual fatigue lifetime with respect to the nonlinear fracture mechanics approach.

Slow Crack Growth Resistance of Parent and Joint Materials From PE4710 Piping for Safety-Related Nuclear Power Plant Piping

2011 ◽  
Author(s):  
S. Kalyanam ◽  
D.-J. Shim ◽  
P. Krishnaswamy ◽  
Y. Hioe
Keyword(s):  
Crack Growth ◽  
Nuclear Power ◽  
Power Plants ◽  
Slow Crack Growth ◽  
Nuclear Industry ◽  
Pipe Material ◽  
Service Water ◽  
Hdpe Pipe ◽  
Pipe Materials ◽  
Hdpe Pipes

HDPE pipes are considered by the nuclear industry as a potential replacement option to currently employed metallic piping for service-water applications. The pipes operate under high temperatures and pressures. Hence HDPE pipes are being evaluated from perspective of design, operation, and service life requirements before routine installation in nuclear power plants. Various articles of the ASME Code Case N-755 consider the different aspects related to material performance, design, fabrication, and examination of HDPE materials. Amongst them, the material resistance (part of Article 2000) to the slow crack growth (SCG) from flaws/cracks present in HDPE pipe materials is an important concern. Experimental investigations have revealed that there is a marked difference (almost three orders less) in the time to failure when the notch/flaw is in the butt-fusion joint, as opposed to when the notch/flaw is located in the parent HDPE material. As part of ongoing studies, the material resistance to SCG was investigated earlier for unimodal materials. The current study investigated the SCG in parent and butt-fusion joint materials of bimodal HDPE (PE4710) pipe materials acquired from two different manufacturers. The various stages of the specimen deformation and failure during the creep test are characterized. Detailed photographs of the specimen side-surface were used to monitor the specimen damage accumulation and SCG. The SCG was tested using a large specimen (large creep frame) as well as using a smaller size specimen (PENT frame) and the results were compared. Further, the effect of polymer orientation or microstructure in the bimodal HDPE pipe on the SCG was studied using specimens with axial and circumferential notch orientations in the parent pipe material.

Sign in / Sign up

Export Citation Format

Share Document