Failure Analysis of 12 Inch Pipeline Riser

2014 ◽  
Author(s):  
Frank Gareau ◽  
Alex Tatarov
Keyword(s):  
Internal Surface ◽  
Fracture Initiation ◽  
Slag Inclusion ◽  
Ground Movement ◽  
Simultaneous Action ◽  
Additional Stress ◽  
Contributing Factors ◽  
Element Analysis ◽  
Material Fracture ◽  
Corrosion Pits

A rupture and an explosion occurred on a 12.75 inch OD high pressure gas pipeline after 40 years in service. The force of the explosion broke the riser off and sent two large pieces of the riser flying into the surrounding forest. The failure occurred as a result of the simultaneous action of several contributing factors: • The weld had a non-specified profile (a step) and contained a large slag inclusion at the location of fracture initiation. • Corrosion pits were growing from the internal surface close to the weld root. • Dewpoint corrosion took place on the internal surface of the riser close to massive flanges. • The dehydrator at the compressor station was not removing the target amount of moisture. • Low temperatures contributed to the failure by decreasing material fracture toughness. • Ground movement could have created additional stress required for the failure to occur. Several of the above listed factors (pitting corrosion, ground movement, malfunctioning of the dehydrator) developed with time, which explains the delayed mode of failure. The conclusions were supported by Finite Element Analysis and Fracture Mechanics calculations.

Fracture Finite Element Analysis for Roll Forming of U Section Parts of TRIP 600 Steel

2012 ◽  
Vol 249-250 ◽  
pp. 874-880 ◽  
Author(s):  
Yan Zhi Guan ◽  
Qiang Li ◽  
Yu Yan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Damage Evolution ◽  
Fracture Initiation ◽  
Roll Forming ◽  
Element Analysis ◽  
Material Fracture ◽  
Set Up ◽  
Explicit Dynamic ◽  
The Relationship

By applying the shear damage criteria, facture occurrence for roll forming of U Section parts of TRIP 600 steel is analyzed with nonlinear finite element. In accordance with the maximum value of steel sheet of plastic strains for the fracture initiation and with the application of the element deletion technology of the ductile fracture, the calculation of the damage evolution parameters of the material fracture is successfully set up. By applying the explicit dynamic solution method, the fracture finite element analysis of TRIP600U type section roll forming is realized, and the relationship among the stress, strain, energy density as well as damage evolution and material fracture is obtained.

Preventing Girth Weld Failure in Pipelines: Measurement of Loads and Application of Assessment Methods

2020 ◽  
Author(s):  
Andy Young ◽  
Robert M. Andrews
Keyword(s):  
Transmission Lines ◽  
Oil And Gas ◽  
Large Diameter ◽  
Ground Movement ◽  
External Loading ◽  
Key Factors ◽  
Axial Loads ◽  
Contributing Factors ◽  
Increased Risk ◽  
Girth Welds

Abstract Pipeline failures from circumferential cracking at girth welds continues to affect large diameter oil and gas transmission lines, even for modern lines constructed this century. The key factors that contribute to the failure at girth welds are the dimensions of defects present, the material properties of the pipe and weldments, and the presence of loading that drives crack growth. The mechanisms of failure are well understood, but identifying and measuring the contributing factors can be a challenge. Locating girth welds that are subject to elevated loads will enable operators to focus on sections with an increased threat of failure. In this paper, we consider each of the key factors, how these are identified and defined, and the uncertainties in the measurement process. Specific attention is applied to the presence and quantification of loads and how these influence the potential for failure. This includes sources of active external loading due to ground movement, for example, or loads generated in the pipeline from the construction process. Loads can also be quantified by measuring bending strain from inline inspection inertial measurement units. A more complete picture of pipeline loading can be established by integrating a structural analysis that accounts for the direction of pipeline movement and the presence of axial loads. The relationship between assessing pipeline integrity from ground movement — typically with strainbased methods — and establishing whether the defect can survive the load is explored. The relative contribution of bending and axial loads in the failure of defects is considered. The outcome of the study will assist pipeline operators in prioritising actions that enable the quantification of the all the key parameters. The resultant analysis will provide guidance on the girth welds that have an increased risk of failure and this will enable protective actions to be defined and scheduled accordingly.

Fracture Initiation and Propagation in Fatigue Contact Loading of AA6082 Aluminium Alloy

2006 ◽  
Vol 324-325 ◽  
pp. 1091-1094
Author(s):  
Angela Benedetti ◽  
Pier Gabriele Molari ◽  
Piero Morelli
Keyword(s):  
Aluminium Alloy ◽  
Contact Area ◽  
Contact Fatigue ◽  
Fracture Initiation ◽  
Free Edge ◽  
Element Analysis ◽  
Contact Loading ◽  
Linear Finite Element ◽  
Initiation And Propagation ◽  
Microscopy Analysis

This paper presents the results of an experimental investigation on surface contact fatigue of AA6082 aluminium alloy. After testing, microscopy analysis of the specimen contact area shows plastic deformation at the centre and circumferential cracks at the very edge of the print. Major cracks develop at a certain depth under the border of the contact area and propagate beneath the surface, in the direction of both the centre of contact and the lateral free edge of the specimens. No cracks have been observed at the centre of contact, neither on the surface, nor inside the material. Tensile properties of the alloy have been measured and a non linear finite element analysis has been performed in order to calculate the field of deformation and stress in the contact zone. Finally, stress intensities are correlated with the crack initiation points and an interpretation of the propagation paths, in regard to stress distribution, is given.

Sources of Fatigue in Random-Vibration Durability of Surface Mount Interconnects

2009 ◽  
Author(s):  
Y. Zhou ◽  
M. Al-Bassyiouni ◽  
A. Dasgupta
Keyword(s):  
Accumulation Rate ◽  
Random Excitation ◽  
Additional Stress ◽  
Dynamic Mode ◽  
Dynamic Prediction ◽  
Element Analysis ◽  
Static Approximation ◽  
Quasi Static Approximation ◽  
Dynamic Movement ◽  
Resonant Modes

The transient response of a PBGA256 assembly to random excitation is explored with quasi-static and transient finite element analysis, as well as with experiments. The quasi-static approximation is based on the first modal contribution to the measured PWB response. The dynamic prediction for solder strain and resulting damage accumulation rate are found to be significantly larger than in the quasi-static approximation. The quasi-static model is clearly missing additional stress drivers such as the dynamic movement of the component relative to the PWB and higher resonant modes of PWB flexure. The dynamic mode of the component is verified in this paper with two accelerometers placed on the component and on the PWB. Investigation of the higher modes of the PWB is deferred to a future study.

Geometry Governs Mechanics of Cardiovascular Stents

2009 ◽  
Author(s):  
Graeham R. Douglas ◽  
Tho Wei Tan ◽  
Tim Bond ◽  
A. Srikantha Phani
Keyword(s):  
Arterial Wall ◽  
Mechanical Response ◽  
Neointimal Hyperplasia ◽  
Stent Migration ◽  
Contributing Factors ◽  
Poisson Effect ◽  
Element Analysis ◽  
Cardiovascular Stents ◽  
Stent Restenosis ◽  
Longitudinal Strains

Cardiovascular stents are tubular lattice structures implanted into a stenosed artery to provide adequate lumen support and promote circulation. Commonly encountered complications are stent migration, NeoIntimal Hyperplasia (NIH), and damage to the arterial wall. Central to all these problems is the mechanical response of a stent to forces operating in situ including stent-artery interaction. The influence of geometry or repetitive pattern of the stent upon its mechanical response is the subject of this study. We focus on damage to the arterial wall caused by the stent which can lead to eventual in-stent restenosis. Stent-artery compliance mismatch and longitudinal strain due to Poisson effect are hypothesized as the main contributing factors to restenosis. Finite Element Analysis (FEA) is employed to compare radial compliance and longitudinal strains of different stent geometries. Existing geometrical calculations in the literature [1] are applied to stents of different geometries to compute a non-dimensional NIH index. The main finding is that hybrid lattice stent designs exhibit negligible longitudinal strains (Poisson effect) as the stent expands/contracts during each Cardiac cycle. Wall stresses can be minimized though a careful tailoring of stent geometry.

Thermoelastic Stresses in an Axisymmetric Thick-Walled Tube Under an Arbitrary Internal Transient

2004 ◽  
Vol 126 (3) ◽  
pp. 327-332 ◽  
Author(s):  
A. E. Segall
Keyword(s):  
Thermal Loading ◽  
Series Representation ◽  
Thermoelastic Stress ◽  
Internal Surface ◽  
Stress Fields ◽  
Element Analysis ◽  
Axisymmetric Solution ◽  
Thermoelastic Stresses ◽  
Stress States ◽  
Transient Thermal

A closed-form axisymmetric solution was derived for the transient thermal-stress fields developed in thick-walled tubes subjected to an arbitrary thermal loading on the internal surface with convection to the surrounding external environment. Generalization of the temperature excitation was achieved by using a versatile polynomial composed of integral-and half-order terms. In order to avoid the difficult and potentially error prone evaluation of functions with complex arguments, Laplace transformation and a ten-term Gaver-Stehfest inversion formula were used to solve the resulting Volterra integral equation. The ensuing series representation of the temperature distribution as a function of time and radial position was then used to derive new relationships for the transient thermoelastic stress-states. Excellent agreement was seen between the derived temperature and stress relationships, existing series solutions, and a finite-element analysis when the thermophysical and thermoelastic properties were assumed to be independent of temperature. The use of a smoothed polynomial in the derived relationships allows the incorporation of empirical data not easily represented by standard functions. This in turn permits an easy analysis of the significance of the exponential boundary condition and convective coefficient in determining the magnitudes and distribution of the resulting stress states over time. Moreover, the resulting relationships are easily programmed and can be used to verify and calibrate numerical calculations.

Finite Element Analysis for the Tube Sinking Process of the Micro Ti-0.2Pd Tube

2013 ◽  
Vol 465-466 ◽  
pp. 693-698 ◽  
Author(s):  
Seok Kwan Hong ◽  
Jeong Jin Kang ◽  
Jong Deok Kim ◽  
Heung Kyu Kim ◽  
Sang Yong Lee ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Flow Stress ◽  
Internal Surface ◽  
External Diameter ◽  
Stress Equation ◽  
Element Analysis ◽  
Simulation Error ◽  
Simulation Results ◽  
Flow Stress Equation

In this study, the tube sinking process for manufacturing the micro Ti-0.2Pd tube (2.4 mm external diameter, 0.4 mm thickness) was simulated by finite element analysis. The external diameter of the initial tube was 5.0 mm. In order to simulate the tube sinking process, the flow stress equation was deducted from the result of the tensile test and friction coefficient was indirectly obtained through the parameter studies. The simulation results showed the simulation error according to the change of diameter predicted to be less than 2%. The defect of the internal surface by stress was found through the experiment result.

Development of a Profile Matching Criteria to Model Dents in Pipelines Using Finite Element Analysis

2017 ◽  
Author(s):  
Janine Woo ◽  
Muntaseer Kainat ◽  
Samer Adeeb
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Additional Stress ◽  
Element Analysis ◽  
Fea Model ◽  
Profile Matching ◽  
Industry Standards ◽  
Stress Risers ◽  
Matching Criteria ◽  
Key Indicators

Current industry standards cite depth and interaction with additional stress risers as the key indicators of pipeline integrity concerns in regards to dents. There have been significant efforts towards the improvement of these benchmarks in recent years. Several dent assessment methods are presented in literature, including research focused on the use of finite element analysis (FEA). The accurate assessment of dents using FEA is heavily reliant on how close the shape produced by the FEA model aligns with the shape of the actual dent. The research presented in this paper has been conducted to evaluate the sensitivity of the stresses and strains to the dent profile shape. Information regarding the existence, shape, and size of dents is typically provided by in-line inspection (ILI) tools. An FEA model is then built in commercially available software, ABAQUS, to create a dent profile that closely resembles the profile given by the ILI. The study in this paper assesses the effect of different indenter sizes on the stresses and strains within the dent and provides a recommendation to quantify the error between the ILI and FEA profiles. The process of matching a dent profile using FEA is compared to an existing analytical method to calculate strain, the equations proposed in ASME B31.8. The FEA results were found to be more conservative than the strains calculated using ASME B31.8.

Integrity Assessment of Mechanical Components Subjected to Mixed Mode Cracking

2016 ◽  
Author(s):  
Lingfu Zeng ◽  
Chouping Luo ◽  
Lennart G. Jansson
Keyword(s):  
Mixed Mode ◽  
Nuclear Power ◽  
Fracture Initiation ◽  
Mode I ◽  
Multiple Cracks ◽  
Straight Pipe ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Failure Assessment ◽  
Metal Weld

This paper addresses a mixed mode driven cracking and its integrity assessment for applications in aging nuclear power piping. Following our earlier discussion on the use of mode-I based criteria in the current R6-method-based practice of integrity assessment, case studies conducted using finite element analysis are conducted and examined: (1) A plate with a single and multiple central crack(s) under tension; (2) A full-scale laboratory test of a straight pipe with an obliquely inserted crack in a dissimilar metal weld. Our results confirm the following earlier observations: For cases when mixed mode loading conditions are significant, (i) the fracture initiation predicted by using J-integral based mixed mode cracking criteria can approximately be achieved by an “effective stress intensity factor” based approach; (ii) it is not conservative to use a purely mode-I based criterion for the evaluation of the fracture failure assessment for typical problems of mixed mode driven cracking; (iii) The effect of multiple cracks can be significant and an assessment by only examining one crack, which is a common practice today, may not be fully conservative.

scholarly journals Prediction of machining deformation and reasonable design of gear blank for split straight bevel gear

2021 ◽  
Author(s):  
Bin Wang ◽  
Chenxiao Yan ◽  
Peiyao Feng ◽  
Shuaipu Wang ◽  
Shuo Chen ◽  
...  
Keyword(s):  
Calculation Model ◽  
Bevel Gear ◽  
Geometric Parameters ◽  
Machining Process ◽  
Additional Stress ◽  
Element Analysis ◽  
Bending Deformation ◽  
Straight Bevel Gear ◽  
Machining Deformation ◽  
The Moment

Abstract The deformation of gear blank is serious in the machining process of the split straight bevel gear,considering the material and the design of gear blank, the relationship between the change of additional stress and bending deformation of gear blank is studied, and the calculation model of the internal additional stress and additional torque during the gear cutting is established.According to the moment-area method, the calculation formula of the bending deformation of gear blank is derived, and combined with the time-varying stiffness, the mathematical model of the gear blank deformation is obtained. The theoretical calculation, finite element analysis and experimental results are highly consistent.Based on the above research, the internal relationships between the machining deformation and the geometric parameters such as the thickness, diameter and gear module of the split gear blank is analyzed, and the reasonable design of the geometric parameters of the split gear blank and the reasonable dividing law of the gear blank are explored.

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