Tensile Strain Models for Strain-Based Design of Pipelines

2012 ◽  
Author(s):  
Yong-Yi Wang ◽  
Ming Liu ◽  
Yaxin Song ◽  
David Horsley
Keyword(s):  
Material Properties ◽  
Tensile Strain ◽  
Weld Strength ◽  
Limit States ◽  
Design Models ◽  
Strain Capacity ◽  
Strain Design ◽  
Level 3 ◽  
Tensile Strain Capacity

This paper covers the development of tensile strain design models using a multidisciplinary approach, including fundamental fracture mechanics, small-scale material characterization tests, and large-scale tests of full-size pipes. The tensile strain design models are formulated in a four-level format. The Level 1 procedure provides estimated tensile strain capacity (TSC) in a tabular format for quick initial assessment. The initiation toughness alternatively termed apparent toughness is estimated from upper shelf Charpy impact energy. The Level 2 procedure contains a set of parametric equations based on an initiation-control limit state. The tensile strain capacity can be computed from these equations with the input of a pipe’s dimensional and material property parameters. The apparent toughness is estimated from either upper shelf Charpy energy or upper shelf toughness of standard CTOD test specimens. The Level 3 procedure uses the same set of equations as in Level 2 and the toughness values are obtained from low-constraint tests. In the Level 3 procedure, two limit states based on either initiation control or ductile instability can be used. The Level 4 procedure allows the use of direct FEA calculation to develop crack driving force relations. The same limit states as those in Level 3 may be used. The Level 4 procedures should only be used by seasoned experts in special circumstances where lower level procedures are judged inappropriate. The tensile strain design models may be used for the following purposes: (1) The determination of tensile strain capacity for a given set of material properties and flaw size. (2) The determination of acceptable flaw sizes for a given set of material properties and target tensile strain capacity. (3) The selection of material properties to achieve a target strain capacity for a given flaw size. (4) The optimization of the tensile strain capacity by balancing the requirements of material parameters, such as weld strength (thus weld strength mismatch level) versus toughness. The application of the tensile strain design models is given in a companion paper.

Multi-Tier Tensile Strain Models for Strain-Based Design: Part 2 — Development and Formulation of Tensile Strain Capacity Models

2012 ◽  
Author(s):  
Ming Liu ◽  
Yong-Yi Wang ◽  
Yaxin Song ◽  
David Horsley ◽  
Steve Nanney
Keyword(s):  
Driving Force ◽  
Tensile Strain ◽  
Weld Strength ◽  
Experiment Data ◽  
Pipe Wall Thickness ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Welding Processes ◽  
Tensile Strain Capacity

This is the second paper in a three-paper series related to the development of tensile strain models. The fundamental basis of the models [1] and evaluation of the models against experiment data [2] are presented in two companion papers. This paper presents the structure and formulation of the models. The philosophy and development of the multi-tier tensile strain models are described. The tensile strain models are applicable for linepipe grades from X65 to X100 and two welding processes, i.e., mechanized GMAW and FCAW/SMAW. The tensile strain capacity (TSC) is given as a function of key material properties and weld and flaw geometric parameters, including pipe wall thickness, girth weld high-low misalignment, pipe strain hardening (Y/T ratio), weld strength mismatch, girth weld flaw size, toughness, and internal pressure. Two essential parts of the tensile strain models are the crack driving force and material’s toughness. This paper covers principally the crack driving force. The significance and determination of material’s toughness are covered in the companion papers [1,2].

Enhanced Apparent Toughness Approach to Tensile Strain Design

2010 ◽  
Author(s):  
Ming Liu ◽  
Yong-Yi Wang ◽  
Xin Long
Keyword(s):  
Design Methodology ◽  
Tensile Strain ◽  
Essential Element ◽  
Initial Growth ◽  
Resistance Curve ◽  
Strain Capacity ◽  
Strain Design ◽  
Tangent Method ◽  
Tensile Strain Capacity

Tensile strain design is an essential element of the overall strain-based design methodology. This paper focuses on the apparent toughness approach and introduces the concept of apparent CTOD resistance curve (CTODR). The determination of apparent toughness, CTODA, from the apparent CTODR is demonstrated. The prediction of tensile strain capacity (TSC) using the CTODA and the traditional tangent method is conducted. Similar results are obtained from both approaches. The value of apparent CTODR is found to be relatively insensitive to the amount of flaw growth after some limited initial growth. This insensitivity allows the determination of CTODA at the small amount of flaw growth. This feature establishes the connection between CTODA and initiation-based toughness. Further work is under way to apply these findings.

Effects of Biaxial Loading on the Tensile Strain Capacity of Girth Welds With Weld Strength Undermatching and HAZ Softening

2020 ◽  
Author(s):  
Banglin Liu ◽  
Yong-Yi Wang ◽  
Xiaotong Chen ◽  
David Warman
Keyword(s):  
Internal Pressure ◽  
Tensile Strain ◽  
Biaxial Loading ◽  
Reduction Factor ◽  
Pressure Level ◽  
Weld Strength ◽  
Strain Capacity ◽  
Weld Region ◽  
Girth Welds ◽  
Tensile Strain Capacity

Abstract The ability to accurately estimate the tensile strain capacity (TSC) of a girth weld is critical to performing strain-based assessment (SBA). A wide range of geometry, material, and loading factors can affect the TSC of a girth weld. Among the influencing factors, an increase in the internal pressure level has been shown to have a detrimental effect on the TSC. The overall influence of internal pressure is usually quantified by a TSC reduction factor, defined as the ratio of the TSC at zero pressure to the lowest TSC typically attained at pressure factors around 0.5–0.6. Here the pressure factor is defined as the ratio of the nominal hoop stress induced by pressure to the yield strength (YS) of the pipe material. A number of numeric and experiment studies have reported a TSC reduction factor of 1.5–2.5. These studies generally focused on strain-based designed pipelines with evenmatching or overmatching welds, minimum heat affected zone (HAZ) softening, and a surface breaking flaw at the weld centerline or the fusion boundary. This paper examines the effects of pipe internal pressure on the TSC of girth welds under the premise of weld strength undermatching and HAZ softening. The interaction of biaxial loading and the local stress concentration at the girth weld region was quantified using full-pipe finite element analysis (FEA). The relationship between TSC and the internal pressure level was obtained under several combinations of weld strength mismatch and HAZ softening. Results from the FEA show that the effects of the internal pressure on the TSC are highly sensitive to the material attributes in the girth weld region. Under less favorable weld strength undermatching and HAZ softening conditions, the traditionally assumed reduction factor or 1.5–2.5 may not be applicable. Further, the location of tensile failure is found to depend on both the weld material attributes and the internal pressure. It is possible for the failure location to shift from pipe body at zero internal pressure to the girth weld at elevated internal pressure levels. The implications of the results for both girth weld qualification and integrity assessment are discussed.

Framework for Key Influences on Tensile Strain Capacity of Flawed Girth Welds

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Stijn Hertelé ◽  
Rudi Denys ◽  
Anthony Horn ◽  
Koen Van Minnebruggen ◽  
Wim De Waele
Keyword(s):  
Tensile Strain ◽  
Influence Factor ◽  
Weld Strength ◽  
Strain Capacity ◽  
Strain Behavior ◽  
Weld Geometry ◽  
Girth Welds ◽  
Tearing Resistance ◽  
Tensile Strain Capacity ◽  
Element Study

A key influence factor in the strain-based assessment of pipeline girth weld flaws is weld strength mismatch. Recent research has led to a framework for tensile strain capacity as a function of weld flow stress (FS) overmatch. This framework is built around three parameters: the strain capacity of an evenmatching weldment, the sensitivity of strain capacity to weld FS overmatch, and the strain capacity at gross section collapse (GSC). A parametric finite element study of curved wide plate (CWP) tests has been performed to identify the influence of various characteristics on each of these three parameters. This paper focuses on flaw depth, tearing resistance of the weld, stress–strain behavior of the base metal, and weld geometry. Influences of these characteristics are mostly found to be limited to one or two of the three framework parameters. A preliminary structure is proposed for equations that further develop the strain capacity framework.

Framework for Key Influences on Tensile Strain Capacity of Flawed Girth Welds

2013 ◽  
Author(s):  
Stijn Hertelé ◽  
Rudi Denys ◽  
Anthony Horn ◽  
Koen Van Minnebruggen ◽  
Wim De Waele
Keyword(s):  
Flow Stress ◽  
Tensile Strain ◽  
Influence Factor ◽  
Weld Strength ◽  
Strain Capacity ◽  
Weld Geometry ◽  
Strain Behaviour ◽  
Girth Welds ◽  
Tearing Resistance ◽  
Tensile Strain Capacity

A key influence factor in the strain-based assessment of pipeline girth weld flaws is weld strength mismatch. Recent research has led to a framework for tensile strain capacity as a function of weld flow stress overmatch. This framework is built around three parameters: the strain capacity of an evenmatching weldment, the sensitivity of strain capacity to weld flow stress overmatch and the strain capacity at gross section collapse. A parametric finite element study of curved wide plate tests has been performed to identify the influence of various characteristics on each of these three parameters. This paper focuses on flaw depth, tearing resistance of the weld, stress-strain behaviour of the base metal, and weld geometry. Influences of these characteristics are mostly found to be limited to one or two of the three framework parameters. A preliminary structure is proposed for equations that further develop the strain capacity framework.

A Quantitative Approach to Tensile Strain Capacity of Pipelines

2006 ◽  
Author(s):  
Yong-Yi Wang ◽  
Ming Liu ◽  
David Horsley ◽  
Joe Zhou
Keyword(s):  
Quantitative Determination ◽  
Tensile Strain ◽  
Limit State ◽  
Ultimate Limit State ◽  
Strain Capacity ◽  
Closed Form Solutions ◽  
Number Of Factors ◽  
Girth Welds ◽  
Tensile Strain Capacity

Tensile strain rupture is an ultimate limit state. A limit state is stated in generic terms of “load” and “resistance” or alternatively termed “demand” and “capacity.” The “demand” of tensile rupture limit state is mostly related to displacement-controlled loading, such as that induced by frost heave, landslide, and seismic activities. The “capacity” is most often controlled by girth weld tensile strain limits, as girth welds tend to be the weakest link in pipelines experiencing high tensile strains. The tensile strain limits of girth welds are affected by a large number of factors: tensile and toughness properties of the pipe and weld, weld geometry, stress state, defect size and location. Consequently, closed-form solutions for tensile strain limits of girth welds do not yet exist in codes and standards. PRCI and TransCanada have funded a number of projects in recent years to develop fracture-mechanics-based procedures aimed at quantitative determination of girth weld tensile strain limits. The results of these projects, along with the reviews and examination of available experiment data by the authors, have culminated in a set of recommended procedures that enable the quantitative determination of the tensile strain capacity of pipelines. The required input parameters, formulae for the computation of tensile strain limits, limits of applicability, and suggested methods of applications are specified in the proposed procedures. This paper covers the technical basis of the procedures. Particular emphasis is placed on the validation of these procedures. The limitations of the procedures and future directions of improvements are suggested. It is believed that these procedures may lay the initial groundwork towards the eventual code implementation of a comprehensive set of tools for quantitative strain-based design of pipelines.

A Case Study of Predicting Tensile Strain Capacity of In-Service Pipelines

2020 ◽  
Author(s):  
Junfang Lu ◽  
Ali Fathi ◽  
Nader Yoosef-Ghodsi ◽  
Debra Tetteh-Wayoe ◽  
Mike Hill
Keyword(s):  
Material Properties ◽  
Tensile Strain ◽  
Large Diameter ◽  
Ground Movement ◽  
Capacity Assessment ◽  
Pipe Material ◽  
Strain Capacity ◽  
Welding Processes ◽  
Tensile Strain Capacity

Abstract Strain-based design (SBD) method has evolved over the years for use in the construction of large-diameter, high pressure gas and liquid transmission pipelines. It has not been widely materialized for major construction projects because of the technical complexity which requires multidisciplinary expertise including, but not limited to, pipeline material properties, welding processes, mechanical testing, field construction, and weld inspection. The industry has been showing more interest in using this methodology for strain capacity assessment of in-service stress-based pipelines, especially those that are subjected to ground movement. The strain capacity assessment of the stress-based pipelines is essential to ensure structural integrity and operational safety of the pipeline. This has become more apparent due to recent incidents in pipeline industry caused by geotechnical hazards. This paper provides a case study of assessing the tensile strain capacity (TSC) of existing modern linepipes manufactured through thermomechanical controlled process (TMCP). The TSC was predicted using two main methodologies in the public domain: the CSA Z662-11 Annex C approach and the PRCI-CRES TSC model. Actual pipeline information and construction data are used to perform TSC assessment when possible. This includes pipe material properties, welding procedures qualified on the project pipe, and test weld properties. The predicted TSC and the estimated strain demand will allow for effective remediation decisions. This work helps to enhance pipeline strain management systems in response to the geotechnical and hydrotechnical issues and therefore fills the gaps in present day’s pipeline threat management programs in addition to crack, corrosion and mechanical damage threats. Through such a program, prevention, monitoring and mitigation strategies can be deployed to existing stress-based pipelines, especially in areas where pipeline strain is identified as a potential risk.

Multi-Tier Tensile Strain Models for Strain-Based Design: Part 1 — Fundamental Basis

2012 ◽  
Author(s):  
Yong-Yi Wang ◽  
Ming Liu ◽  
Fan Zhang ◽  
David Horsley ◽  
Steve Nanney
Keyword(s):  
Physical Process ◽  
Tensile Strain ◽  
Limit State ◽  
General Concept ◽  
Tensile Failure ◽  
Experiment Data ◽  
Limit States ◽  
Strain Design ◽  
Associated Representation ◽  
Tensile Strain Capacity

This is the first paper in a three-paper series on the tensile strain design of pipelines. The formulation of the multi-tier models [1] and evaluation of the models against experiment data [2] are presented in two companion papers. This paper starts with an introduction of general concept of strain-based design. The central part of the paper is then devoted to the tensile strain capacity, including (1) physical process of tensile strain failure, (2) limit states of tensile strain failure and associated toughness representation, and (3) fundamental basis of tensile strain models. The most significant part of the fundamental basis, the limit state of tensile failure and associated representation of the material’s toughness, is given the greatest amount of attention.

Estimation of Tensile Strain Capacity of Vintage Girth Welds

2021 ◽  
Author(s):  
Banglin Liu ◽  
Bo Wang ◽  
Yong-Yi Wang ◽  
Otto Jan Huising
Keyword(s):  
Tensile Strain ◽  
Strain Capacity ◽  
Girth Welds ◽  
Tensile Strain Capacity
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