SOME ASPECTS OF THE TIME DEPENDENT DUCTILE FRACTURE OF LINE PIPE STEELS

1980 ◽  
pp. 519-528 ◽  
Author(s):  
S. Tsuru ◽  
S.J. Garwood
Keyword(s):  
Ductile Fracture ◽  
Time Dependent ◽  
Pipe Steels ◽  
Line Pipe

Effects of Soil Cohesiveness and Depth on Dynamic Ductile Fracture Speeds

2008 ◽  
Author(s):  
D. Rudland ◽  
D.-J. Shim ◽  
G. M. Wilkowski ◽  
S. Kawaguchi ◽  
N. Hagiwara ◽  
...  
Keyword(s):  
Ductile Fracture ◽  
Large Scale ◽  
Soil Depth ◽  
Crack Arrest ◽  
Small Scale ◽  
Total Density ◽  
Pipe Material ◽  
Pipe Steels ◽  
Line Pipe ◽  
Fracture Arrest

The ductile fracture resistance of newer line pipe steels is of concern for high grade/strength steels and higher-pressure pipeline designs. Although there have been several attempts to make improved ductile fracture arrest models, the model that is still used most frequently is the Battelle Two-Curve Method (TCM). This analysis incorporates the gas-decompression behavior with the fracture toughness of the pipe material to predict the minimum Charpy energy required for crack arrest. For this analysis, the influence of the backfill is lumped into one empirically developed “soil” coefficient which is not specific to soil type, density or strength. No attempt has been made to quantify the effects of soil depth, type, total density or strength on the fracture speeds of propagating cracks in line pipe steels. In this paper, results from small-scale and large-scale burst tests with well-controlled backfill conditions are presented and analyzed to determine the effects of soil depth and cohesiveness on the fracture speeds. Combining this data with the past full-scale burst data used in generating the original backfill coefficient provides additional insight into the effects of the soil properties on the fracture speeds and the arrest of running ductile fractures in line pipe materials.

Investigation Into the Use of a Single Specimen for the Determination of Dynamic Steady State Propagation Resistance in High Toughness Line-Pipe Steels

2002 ◽  
Author(s):  
David L. Rudland ◽  
Gery Wilkowski ◽  
Yong-Yi Wang ◽  
David Horsley ◽  
Brian Rothwell ◽  
...  
Keyword(s):  
Steady State ◽  
Fracture Energy ◽  
Ductile Fracture ◽  
Opening Angle ◽  
Single Specimen ◽  
Pipe Steels ◽  
Line Pipe ◽  
Propagation Resistance ◽  
High Toughness ◽  
Dynamic Ductile Fracture

This paper summarizes efforts funded by TransCanada PipeLine Limited on improving the methodology for predicting a true measure of the dynamic steady-state fracture toughness of line-pipe steels using a single mill test specimen. In the past, ductile fracture methodologies generally involved using the Charpy V-notch test to empirically quantify the material dynamic ductile fracture propagation resistance. However, due to its geometry, the use of the Charpy test has proven to be unreliable for high-toughness materials, for materials that have rising-shelf energies, and for higher-grade steels (relative to those for which correlations were originally established). An improved methodology for characterizing the dynamic ductile fracture resistance is to utilize the energy from a full-thickness impact specimen, of which the Drop-Weight Tear Test (DWTT) specimen is the most frequently used type. It has been demonstrated that the total energy from a DWTT-type specimen includes; (1) the energy associated with initiation of the crack (including indentation energy and yielding of the specimen), (2) the energy for transient crack growth from initiation to reaching steady-state fracture, (3) steady-state fracture energy, and (4) a non-steady-state fracture energy region at the end of the test. During the steady-state fracture region it was observed that both the crack velocity and constant crack-tip-opening angle (CTOA) remained constant. This paper presents the results of an investigation aimed at identifying a single specimen that will capture only the steady-state fracture energy present in standard DWTT specimens. Detailed experiments and three-dimensional finite element analyses were used to verify various procedures for eliminating the initiation energy and the residual energy at the end of the tests. A non-instrumented modified specimen, the back-slotted, static-precracked DWTT (BS-SPC-DWTT) specimen, has been developed from the results of these analyses. Energy results from this specimen, for a variety of line-pipe steels, are presented. A correlation between these energies and the propagation energy from standard DWTT specimen is presented. This correlation will aid in the methodology for predicting axial crack arrest in line-pipe steels having higher toughness, a rising upper shelf, or a higher grade.

The Effects of Soil Properties on the Fracture Speeds of Propagating Axial Cracks in Line Pipe Steels

2006 ◽  
Author(s):  
D. Rudland ◽  
G. Wilkowski ◽  
B. Rothwell
Keyword(s):  
Moisture Content ◽  
Ductile Fracture ◽  
Soil Type ◽  
Small Diameter ◽  
Valuable Insight ◽  
Total Density ◽  
Pipe Material ◽  
Pipe Steels ◽  
Line Pipe ◽  
Fracture Arrest

The ductile fracture resistance of newer line pipe steels is of concern for higher grade/strength steels and higher-pressure pipeline designs. Although there have been several attempts to make improved ductile fracture arrest models, the model that is still used most frequently is the Battelle Two-Curve Ductile Fracture Arrest Model, which incorporates the gas-decompression behavior with the fracture toughness of the pipe material to predict the minimum Charpy energy required for crack arrest. For this model, the effect of backfill on the propagating crack fracture speeds is lumped into one empirically based “backfill coefficient,” which does not distinguish different soil types or strengths. Some modifications to this backfill coefficient have been proposed for frozen soil as a function of moisture content, and for water backfill for offshore applications, but no attempt has been made to quantify the effects of soil type, total density or strength on the fracture speeds of propagating cracks in line pipe steels. This paper presents the results from a series of small diameter pipe burst tests that were conducted with different soil backfills. The soils’ moisture content, density, and strength were fully characterized in situ and in the laboratory. In addition, fracture speed data in both unbackfilled and backfilled conditions were recorded. The comparison of the change in fracture speed as a function of soil type, moisture and strength gives valuable insight into the effects of soil on the arrest of running ductile fractures in line pipe materials.

The Misconception of Employing CVN Toughness as Key-Measure in Ductile Crack Arrest Prediction for Modern Line-Pipe Steels

2014 ◽  
Author(s):  
Alexander Völling ◽  
Christoph Kalwa ◽  
Marion Erdelen-Peppler
Keyword(s):  
Ductile Fracture ◽  
Data Base ◽  
Model Calibration ◽  
Crack Arrest ◽  
Full Scale ◽  
Small Scale ◽  
Material Strength ◽  
Original Material ◽  
Pipe Steels ◽  
Line Pipe

Since the late 1960s’ the Battelle Two-curve (BTC) model is the standard method applied in setting up design requirements with regard to the prevention of long-running ductile fracture in pipelines. It is a straightforward tool employing Charpy-V notch (CVN) toughness as key-measure for material resistance against crack propagation. On basis of pipe dimensions, material strength, and under consideration of decompression behavior of the transferred media, it enables to set up requirements for a minimum CVN toughness level to achieve crack arrest. Overall applicability of the BTC model is based on calibration of the underlying equations to a sound data-base, including both full-scale burst test results and small-scale laboratory testing data involving typical line-pipe grades at that period, i.e. up to grade X70 steels with below 100 J upper-shelf CVN toughness. Now over the last decades, mechanical behavior of line-pipe steels was improved significantly. Responding to market demands, higher grades were designed and also toughness levels were raised as outcome of R&D efforts within the steel industry. Unfortunately, stepping outside the original material data-base from BTC model calibration, this method did forfeit its reliability. At the beginning, mispredictions were mainly related to higher grade steels and elevated operating pressures. But more recent full-scale tests did reveal discrepancies in application of the BTC model also for so-called new vintage steels, i.e. grades actually being inside the original data base for model calibration but from current production routes. With regard to applicability/reliability of BTC model based predictions for crack arrest, the origin of uncertainty has particularly been traced back to the involved material toughness measure. Nowadays, it is common sense that the CVN upper-shelf toughness value inadequately describes the resistance against running ductile fracture. More recent thoughts coherently argue towards closer involving stress-strain response and plastic deformation capacities of the material. On basis of results for grades X65, X80 and X100, the general relation between ductility and toughness is discussed. Finally, an elastic-plastic fracture mechanics related analytical approach is introduced which enables to quantify the resistance against ductile fracture propagation. The objective is to provide a reliable procedure for crack arrest prediction in line-pipe steels.

Niobium Microalloyed Line Pipe Steels: Technological Overview

2013 ◽  
Author(s):  
J. M. Gray ◽  
S. V. Subramanian
Keyword(s):  
Process Integration ◽  
Target Strength ◽  
Accelerated Cooling ◽  
Pipe Steels ◽  
Line Pipe ◽  
Steel Technology ◽  
Quantitative Understanding ◽  
Line Pipe Steel ◽  
Low Levels ◽  
Evolution Of Microstructure

A quantitative understanding of hierarchical evolution of microstructure is essential in order to design the base chemistry and optimize rolling schedules to obtain the morphological microstructure coupled with high density and dispersion of crystallographic high angle boundaries to achieve the target strength and fracture properties in higher grade line pipe steels, microalloyed with niobium. Product-process integration has been the key concept underlying the development of niobium microalloyed line pipe steel technology over the years. The development of HTP technology based on 0.1 wt % Nb and low interstitial was predicated by advances in process metallurgy to control interstitial elements to low levels (C <0.03wt% and N< 0.003wt%), sulfur to ultra-low levels (S<20ppm), as well as in product metallurgy based on advances in basic science aspects of thermo-mechanical rolling and phase transformation of pancaked austenite under accelerated cooling conditions, and toughness properties of heat affected zones in welding of niobium microalloyed line pipes. A historical perspective/technological overview of evolution of HTP for line pipe applications is the focus of this paper in order to highlight the key metallurgical concepts underlying Nb microalloying technology which have paved the way for successful development of higher grade line pipe steels over the years.

Improved Specifications Needed for Line Pipe Steels

1963 ◽  
Vol 15 (04) ◽  
pp. 370-374
Author(s):  
J.W. Squire
Keyword(s):  
Pipe Steels ◽  
Line Pipe

Influence of martensite-austenite (MA) on impact toughness of X80 line pipe steels

2016 ◽  
Vol 662 ◽  
pp. 481-491 ◽  
Author(s):  
Nazmul Huda ◽  
Abdelbaset R.H. Midawi ◽  
James Gianetto ◽  
Robert Lazor ◽  
Adrian P. Gerlich
Keyword(s):  
Impact Toughness ◽  
Pipe Steels ◽  
Line Pipe

A Pressure Reduction to Prevent a Time-Delayed Failure in a Damaged Pipeline

2020 ◽  
Author(s):  
Andrew Cosham ◽  
Brian N. Leis ◽  
Paul Roovers ◽  
Mures Zarèa ◽  
Valerie Linton
Keyword(s):  
Full Scale ◽  
The Other ◽  
Battelle Memorial Institute ◽  
Pressure Reduction ◽  
Pipe Steels ◽  
Percent Reduction ◽  
Lower Strength ◽  
Line Pipe ◽  
Delayed Failure ◽  
Strength And Toughness

Abstract A time-delayed failure due to stress-activated creep (cold-creep) is a failure that occurs under a constant load and with no growth due corrosion, fatigue or some other environmentally assisted time-dependent degradation mechanism. A time-delayed failure is prevented by reducing the pressure. ASME B31.4 and B31.8 recommend a 20 percent reduction, to 80 percent of the pressure at the time of damage or discovery. T/PM/P/11 Management Procedure for Inspection, assessment and repair of damaged (non-leaking) steel pipelines, an internal procedure used by National Grid, specifies a 15 percent reduction. The guidance in ASME B31.4 and B31.8, and in T/PM/P/11, is directly or indirectly based on the results of tests on the long term stability of defects conducted by the Battelle Memorial Institute and British Gas Corporation in the 1960s and 70s. The line pipe steels were Grades X52 or X60, and the full-size equivalent Charpy V-notch impact energy (where reported) did not exceed 35 J. The tests indicated that the threshold for a time-delayed failure was approximately 85–95% SAPF (straightaway-pressure-to-failure). The strength and toughness of line pipe steels has significantly increased over the decades due to developments in steel-making and processing. The question then is whether an empirical threshold based on tests on lower strength and lower toughness steels is applicable to higher strength and higher toughness steels. In the Tripartite Project, the Australian Pipelines and Gas Association (APGA), the European Pipeline Research Group (EPRG) and the Pipeline Research Council International (PRCI) collaborated in conducting full-scale six step-load-hold tests on higher strength and higher toughness steels. Companion papers present the other aspects of this multi-year project. An empirical threshold for a time-delayed failure is estimated using the results of the six step-load-hold tests. That estimate is also informed by the other published small and full-scale tests (on lower strength and lower toughness steels). The Ductile Flaw Growth Model is used to infer the effect of strength and toughness on the threshold for a time-delayed failure. A 15 percent pressure reduction, to 85 percent of the pressure at the time of damage (or of the maximum pressure that has occurred since the time of damage), is considered to be sufficient to prevent a time-delayed failure due to stress-activated creep in lower and higher toughness, in lower and higher strength, and in older and newer line pipe steels.

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