Local Strain Accumulation in Pipeline Girth Welds

2004 ◽  
Author(s):  
William Mohr ◽  
Robin Gordon ◽  
Robert Smith
Keyword(s):  
Local Strain ◽  
Test Methods ◽  
Material Behavior ◽  
Ground Movement ◽  
Performance Criteria ◽  
Weld Strength ◽  
Management Service ◽  
Strain Behavior ◽  
Assessment Guidelines ◽  
Girth Welds

The majority of existing pipeline design codes are stress based and provide limited guidance on the design and assessment of pipelines that may experience high local strains in service. High strains can occur in service due to ground movement, bending over an unsupported span and seismic loading. In such cases pipelines should be designed based on strain capacity. The rigors of strain-based analyses pose a number of challenges, particularly related to pipeline girth welds and general material behavior. This paper presents a summary of an ongoing multi-year project co-funded by the US Minerals Management Service (MMS) and US Dept of Transportation (DOT) to develop design and assessment guidelines for pipelines that may experience high strains in service. Specific topics to be addressed by the project include: • Parent Pipe specifications (Y/T limits, stress-strain behavior, material toughness, etc.); • Welding specifications (joint design, joint geometry, weld strength mismatch, etc.); • Engineering Critical Assessment (ECA) Methods for strain based loading; • Validation test methods to verify pipeline performance (criteria for full-scale testing).

Integrity Management of Ground Movement Hazards

2016 ◽  
Author(s):  
Yong-Yi Wang ◽  
Don West ◽  
Douglas Dewar ◽  
Alex McKenzie-Johnson ◽  
Millan Sen
Keyword(s):  
Management Program ◽  
Ground Movement ◽  
Tensile Failure ◽  
Weld Strength ◽  
Factors Affecting ◽  
Ground Movements ◽  
Decision Points ◽  
Starting Point ◽  
Integrity Management ◽  
Girth Welds

Ground movements, such as landslides and subsidence/settlement, can pose serious threats to pipeline integrity. The consequence of these incidents can be severe. In the absence of systematic integrity management, preventing and predicting incidents related to ground movements can be difficult. A ground movement management program can reduce the potential of those incidents. Some basic concepts and terms relevant to the management of ground movement hazards are introduced first. A ground movement management program may involve a long segment of a pipeline that may have a threat of failure in unknown locations. Identifying such locations and understanding the potential magnitude of the ground movement is often the starting point of a management program. In other cases, management activities may start after an event is known to have occurred. A sample response process is shown to illustrate key considerations and decision points after the evidence of an event is discovered. Such a process can involve fitness-for-service (FFS) assessment when appropriate information is available. The framework and key elements of FFS assessment are explained, including safety factors on strain capacity. The use of FFS assessment is illustrated through the assessment of tensile failure mode. Assessment models are introduced, including key factors affecting the outcome of an assessment. The unique features of girth welds in vintage pipelines are highlighted because the management of such pipelines is a high priority in North America and perhaps in other parts of the worlds. Common practice and appropriate considerations in a pipeline replacement program in areas of potential ground movement are highlighted. It is advisable to replace pipes with pipes of similar strength and stiffness so the strains can be distributed as broadly as possible. The chemical composition of pipe steels and the mechanical properties of the pipes should be such that the possibility of HAZ softening and weld strength undermatching is minimized. In addition, the benefits and cost of using the workmanship flaw acceptance criteria of API 1104 or equivalent standards in making repair and cutout decisions of vintage pipelines should be evaluated against the possible use of FFS assessment procedures. FFS assessment provides a quantifiable performance target which is not available through the workmanship criteria. However, necessary inputs to perform FFS assessment may not be readily available. Ongoing work intended to address some of the gaps is briefly described.

Response of Buried Plastic Pipelines Subject to Lateral Ground Movement

2010 ◽  
Author(s):  
Lalinda Weerasekara ◽  
Dharma Wijewickreme
Keyword(s):  
Material Behavior ◽  
Ground Movement ◽  
Pipe Material ◽  
Pipe Axis ◽  
Force Development ◽  
Strain Behavior ◽  
Ground Deformations ◽  
Nonlinear Stress ◽  
Pipe Segment ◽  
Human Losses

The performance of pipelines in areas prone to ground deformations is a major concern for utility owners since the failures of such pipeline systems could cause property damage and even human losses, in addition to business disruption. An analytical solution to determine the response of plastic pipelines subject to abrupt relative ground movement occurring perpendicular to the pipe axis is presented herein. The method accounts for the combined impacts of tension and bending in a pipe segment. Furthermore, the model considers the nonlinear stress-strain behavior of the pipe material and employs an advanced analytical model to calculate the frictional force development along the pipeline. The results obtained from this analytical approach are validated by comparing with the results obtained from a numerical model using soil-spring analysis and the actual viscoelastic material behavior for the pipe material.

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.

Fatigue Investigation of Elastomeric Structures

2010 ◽  
Vol 38 (3) ◽  
pp. 194-212 ◽  
Author(s):  
Bastian Näser ◽  
Michael Kaliske ◽  
Will V. Mars
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Material Behavior ◽  
Period Effect ◽  
Numerical Representation ◽  
Material Force ◽  
Strain Behavior ◽  
Dissipative Effects ◽  
Elastomeric Materials

Abstract Fatigue crack growth can occur in elastomeric structures whenever cyclic loading is applied. In order to design robust products, sensitivity to fatigue crack growth must be investigated and minimized. The task has two basic components: (1) to define the material behavior through measurements showing how the crack growth rate depends on conditions that drive the crack, and (2) to compute the conditions experienced by the crack. Important features relevant to the analysis of structures include time-dependent aspects of rubber’s stress-strain behavior (as recently demonstrated via the dwell period effect observed by Harbour et al.), and strain induced crystallization. For the numerical representation, classical fracture mechanical concepts are reviewed and the novel material force approach is introduced. With the material force approach at hand, even dissipative effects of elastomeric materials can be investigated. These complex properties of fatigue crack behavior are illustrated in the context of tire durability simulations as an important field of application.

Cumulative Damage Mechanics: Characterization, Modeling, and Interpretation of Progressive Failure in Ceramics and Composites

2004 ◽  
Author(s):  
Michael G. Jenkins ◽  
Paul E. Labossie`re ◽  
Jonathan A. Salem
Keyword(s):  
Damage Mechanics ◽  
Progressive Failure ◽  
Ceramic Matrix Composites ◽  
Test Methods ◽  
Cumulative Damage ◽  
Material Behavior ◽  
Matrix Composites ◽  
Damage Models ◽  
Novel Design ◽  
Nonlinear Energy

Ceramic matrix composites (CMCs) have evolved to exhibit inherent damage tolerance through nonlinear energy absorption mechanisms while retaining the desirable attributes of their monolithic structural ceramic counterparts. Mathematical (analytic and numeric) models together with experimental measurements of this damage absorption have aided in understanding the thermomechanical behavior of CMCs. This understanding has led to improved test methods, better predictive modeling of material behavior, appropriate processing methods, and finally novel design methodologies for implementing CMCs. In this paper, background on CMC damage is presented, damage measurement and damage models are discussed and finally probabilistic aspects of constituent materials that can be used to illustrate the cumulative damage behavior of CMCs are described.

Effects of Weld Strength Heterogeneity on Crack Driving Force in Stress and Strain Based Design Scenarios

2014 ◽  
Author(s):  
Stijn Hertelé ◽  
Noel O’Dowd ◽  
Matthias Verstraete ◽  
Koen Van Minnebruggen ◽  
Wim De Waele
Keyword(s):  
Driving Force ◽  
Large Scale ◽  
Limit State ◽  
Weld Strength ◽  
Force Response ◽  
Crack Driving Force ◽  
Key Factor ◽  
Weld Properties ◽  
Girth Welds ◽  
Strain Hardening Behavior

Weld strength mismatch is a key factor with respect to the assessment of a flawed girth weld. However, it is challenging to assign a single strength mismatch value to girth welds, which are generally heterogeneous in terms of constitutive behavior. The authors have recently developed a method (‘homogenization’) to account for weld strength property variations in the estimation of crack driving force response and the corresponding tensile limit state. This paper separately validates the approach for stress based and strain based assessments. Whereas homogenization is reliably applicable for stress based assessments, the strain based crack driving force response is highly sensitive to effects of actual heterogeneous weld properties. The sensitivity increases with increased weld width and decreased strain hardening behavior. For strain based design, a more accurate methodology is desirable, and large scale testing and/or advanced numerical modeling remain essential.

Hyperelastic Muscle Simulation

2007 ◽  
Vol 345-346 ◽  
pp. 1241-1244 ◽  
Author(s):  
Mohd. Zahid Ansari ◽  
Sang Kyo Lee ◽  
Chong Du Cho
Keyword(s):  
Skeletal Muscle ◽  
Silicone Rubber ◽  
Soft Tissues ◽  
Material Model ◽  
Incompressible Material ◽  
Material Behavior ◽  
Rubber Tube ◽  
Stress Strain ◽  
Element Analysis ◽  
Strain Behavior

Biological soft tissues like muscles and cartilages are anisotropic, inhomogeneous, and nearly incompressible. The incompressible material behavior may lead to some difficulties in numerical simulation, such as volumetric locking and solution divergence. Mixed u-P formulations can be used to overcome incompressible material problems. The hyperelastic materials can be used to describe the biological skeletal muscle behavior. In this study, experiments are conducted to obtain the stress-strain behavior of a solid silicone rubber tube. It is used to emulate the skeletal muscle tensile behavior. The stress-strain behavior of silicone is compared with that of muscles. A commercial finite element analysis package ABAQUS is used to simulate the stress-strain behavior of silicone rubber. Results show that mixed u-P formulations with hyperelastic material model can be used to successfully simulate the muscle material behavior. Such an analysis can be used to simulate and analyze other soft tissues that show similar behavior.

Management of Ground Movement Hazards: An Overview of a JIP

2020 ◽  
Author(s):  
Yong-Yi Wang ◽  
Don West ◽  
Doug Dewar ◽  
Alex Mckenzie-Johnson ◽  
Steve Rapp
Keyword(s):  
Best Practice ◽  
Major Elements ◽  
Ground Movement ◽  
Management Approach ◽  
Hazard Management ◽  
Ground Movements ◽  
Strain Design ◽  
Hazard Avoidance ◽  
Actual Field ◽  
Girth Welds

Abstract Ground movements such as landslides, subsidence, and settlement can pose serious threats to the integrity of pipelines. The consequences of a ground movement event can vary greatly. Certain types of ground movements are slow-moving and can be monitored and mitigated before a catastrophic failure. Other forms of ground movements can be difficult to predict. The most effective approach could be hazard avoidance, proactive means to reduce strain demand on pipelines, and/or building sufficiently robust pipeline segments that have a high tolerance to the strain demand. This paper provides an overview of a Joint Industry Project (JIP) aimed at developing a best-practice document on managing ground movement hazards. The hazards being focused on are landslides and ground settlement, including mine subsidence. This document attempts to address nearly all major elements necessary for the management of such hazards. The most unique feature of the JIP is that the scope included the hazard management approach often practiced by geotechnical engineers and the fitness-for-service assessment of pipelines often performed by pipeline integrity engineers. The document developed in the JIP provides a technical background of various existing and emerging technologies. The recommendations were developed based on a solid fundamental understanding of these technologies and a wide array of actual field experiences. In addition to the various elements involved in the management of ground movement hazards, the JIP addresses some common misconceptions about the adequacy of codes and standards, including: • The adequacy of design requirements in ASME B31.4 and B31.8 with respect to ground movement hazards, • The adequacy of linepipe standards such as API 5L and welding standards such as API 1104 for producing strain-resistant pipelines, • The proper interpretation of the longitudinal strain design limit of 2% strain in ASME B31.4 and B31.8, and • The effectiveness of hydrostatic testing in “weeding out” low strain tolerance girth welds.

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