A welding procedure specification is the document describing how a weld joint should be constructed. Arc weld processes are characterized by transient thermal behavior, leading to rapid changes in material properties and dynamic interaction between weld and base material. The objective of the project is to explore how the use of an improved CWM-platform affects representative stress and strain fields in order to assess welding procedure qualification records. Forthis project, the accumulated thermal and mechanical influences from the first run to the final run are brought forward, in one and the same meshed geometrical model. Both the thermal and mechanical material model of the platform are designed to be used for modelling of the base- and weld material,promoting the simulation of the intricate combination of the thermal, elastic,and plastic strains on the plastic strain hardening and the formation of residual stress fields. The output of the simulation is mainly weld cooling times, residual stresses, and deformations. This analysis is taken further by examining how residual stresses influence crack driving force under elastic and plastic loading. In addition, the output from the simulations can be used to assess the realism of the proposed welding parameters. The main experimental welding procedure examined comes from the IIW RSDP Round Robin Phase II benchmark project, where the main aim was to benchmark residual stress simulations. This work was found to contain many applicable challenges of a CWM-analysis project.

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In packaging industries, the demand for usage of Low Density Poly Ethylene foil is of profound interest. In the past, research was carried out on finite and infinite plates with varying crack lengths but having constant crack width. In this thesis, a detailed analysis on crack initiation is carried out on finite plates by varying width of the hole. The hole shapes for stress analysis include circle, ellipse and rectangular notch. Initially, maximum stress is found out using Linear Elastic Fracture Mechanics (LEFM) theory and compared with Finite element method (FEM) results. Secondly using Elastic Plastic Fracture Mechanics theory (EPFM), critical stress and geometric function are evaluated theoretically by Modified Strip Yield Model (MSYM) and numerically by ABAQUS. Finally, a tensile test is conducted to validate the theoretical and numerical results.  By varying the width of the hole, a study on the parameters like critical stress, geometric function is presented. A conclusion is drawn that the effect of hole width should be considered when calculating fracture parameters.

A welding procedure specification is the document describing how a weld joint should be constructed. Arc weld processes are characterized by transient thermal behavior, leading to rapid changes in material properties and dynamic interaction between weld and base material. The objective of the project is to explore how the use of an improved CWM-platform affects representative stress and strain fields in order to assess welding procedure qualification records. Forthis project, the accumulated thermal and mechanical influences from the first run to the final run are brought forward, in one and the same meshed geometrical model. Both the thermal and mechanical material model of the platform are designed to be used for modelling of the base- and weld material,promoting the simulation of the intricate combination of the thermal, elastic,and plastic strains on the plastic strain hardening and the formation of residual stress fields. The output of the simulation is mainly weld cooling times, residual stresses, and deformations. This analysis is taken further by examining how residual stresses influence crack driving force under elastic and plastic loading. In addition, the output from the simulations can be used to assess the realism of the proposed welding parameters. The main experimental welding procedure examined comes from the IIW RSDP Round Robin Phase II benchmark project, where the main aim was to benchmark residual stress simulations. This work was found to contain many applicable challenges of a CWM-analysis project.

Caracterizar propriedades de resistência à propagação de trinca em materiais dúcteis é um elemento central em métodos de avaliação de integridade estrutural de dutos destinados ao transporte de gás, petróleo e seus derivados que utilizam os aços ARBL. Sendo assim, o objetivo deste trabalho foi estudar as propriedades de fratura dúctil do aço API 5L X80, através da obtenção da curva de resistência à propagação estável de defeitos (curvas J-R) do material. O ensaio de tenacidade à fratura para obtenção da curva J-R foi conduzido utilizando a técnica do corpo-de-prova único (single specimen) empregando o método da flexibilidade no descarregamento (unloading compliance), segundo a norma de ensaios ASTM E1820-96. Os corpos-de-prova compactos C(T) apresentaram espessura B=15mm, largura W=2B e uma relação aproximada entre o tamanho de trinca (a) e a largura, a/W=0,6. O ensaio foi conduzido numa máquina universal de ensaios (MTS) servo-controlada e capacidade máxima de 250kN. Adicionalmente, foram conduzidos ensaios convencionais de tração (limite de escoamento – 550MPa, limite de resistência – 676MPa e alongamento total em 50mm – 27%), ensaios de impacto Charpy (energia absorvida de 220J à 0ºC – sentido longitudinal) e análises metalográficas (microestrutura refinada composta por ferrita, colônias de perlita e presença do constituinte MA). Tais caracterizações permitirão uma maior precisão na comparação da curva J-R do aço API 5L X80 em estudo com estudos futuros de tenacidade à fratura. / Assessments of crack growth resistance in ductile materials play a key role in structural integrity procedures for high strength, low alloy (HSLA) pipeline steels commonly employed in gas and petroleum trasmission systems. This work presents an investigation of the ductile tearing properties for an API 5L X80 pipeline steel using experimentally measured crack growth resistance curves (J-R curves) for the material. Testing of the X80 pipeline steel employed compact tension (C(T)) fracture specimens to determine the J-R curves based upon the unloading compliance method using a single specimen technique in accordance with the ASTM E1820 standard procedure. The C(T) specimens have thickness B=15mm, width W=2B and a ratio between crack size (a) and width, a/W=0,6. The experimental tests utilized a 250 kN MTS universal machine. Conventional tensile tests were also performed to determine the tensile properties for the tested material: yield strength of 550MPa, tensile strength of 676MPa and elongation of 27% (gage length of 50 mm). The Charpy V-notch impact tests also provided and absorbed energy of 220J at 0ºC. The metallographic analysis showed colonies of perlite and MA constituent islands in a ferrite matrix. This experimental characterization provides additional toughness and mechanical data against which the general behavior of X80 class pipeline steel can be compared.

With over 830,000 km of operating pipeline in Canada alone, their safe and continued functioning underpins much of daily life. A key type of risk associated with pipelines is third-party damage, damage caused by actions not associated with the pipelines normal operation. The question of whether the pressurized structure like pipeline or pressure vessel would undergo “unzipping” due to the third-party impact is crucial for the safety of pipelines or pressure vessels in service needs to be answered. Thus, we endeavour to develop a methodology for assessment of design solutions effectiveness to prevent a pipeline or pressure vessel failure in an abrupt explosion-like fashion due to third-party damage. Model of crack propagation determining whether the “unzipping” rupture will occur is viewed as a key element in the safety-driven design procedure providing significant effect on the safety of operation. The crack propagation modeling is achieved through the use of nonlinear fracture mechanics technique. The method of singular integral equations is used to calculate the critical stress required for the catastrophic failure of pipeline or pressure vessel damaged due to third-party interference. The model was implemented as a FORTRAN program. Testing of the developed numerical tool was performed using experimental data available in the literature, with the results showing promising agreement. / February 2016

Caracterizar propriedades de resistência à propagação de trinca em materiais dúcteis é um elemento central em métodos de avaliação de integridade estrutural de dutos destinados ao transporte de gás, petróleo e seus derivados que utilizam os aços ARBL. Sendo assim, o objetivo deste trabalho foi estudar as propriedades de fratura dúctil do aço API 5L X80, através da obtenção da curva de resistência à propagação estável de defeitos (curvas J-R) do material. O ensaio de tenacidade à fratura para obtenção da curva J-R foi conduzido utilizando a técnica do corpo-de-prova único (single specimen) empregando o método da flexibilidade no descarregamento (unloading compliance), segundo a norma de ensaios ASTM E1820-96. Os corpos-de-prova compactos C(T) apresentaram espessura B=15mm, largura W=2B e uma relação aproximada entre o tamanho de trinca (a) e a largura, a/W=0,6. O ensaio foi conduzido numa máquina universal de ensaios (MTS) servo-controlada e capacidade máxima de 250kN. Adicionalmente, foram conduzidos ensaios convencionais de tração (limite de escoamento – 550MPa, limite de resistência – 676MPa e alongamento total em 50mm – 27%), ensaios de impacto Charpy (energia absorvida de 220J à 0ºC – sentido longitudinal) e análises metalográficas (microestrutura refinada composta por ferrita, colônias de perlita e presença do constituinte MA). Tais caracterizações permitirão uma maior precisão na comparação da curva J-R do aço API 5L X80 em estudo com estudos futuros de tenacidade à fratura. / Assessments of crack growth resistance in ductile materials play a key role in structural integrity procedures for high strength, low alloy (HSLA) pipeline steels commonly employed in gas and petroleum trasmission systems. This work presents an investigation of the ductile tearing properties for an API 5L X80 pipeline steel using experimentally measured crack growth resistance curves (J-R curves) for the material. Testing of the X80 pipeline steel employed compact tension (C(T)) fracture specimens to determine the J-R curves based upon the unloading compliance method using a single specimen technique in accordance with the ASTM E1820 standard procedure. The C(T) specimens have thickness B=15mm, width W=2B and a ratio between crack size (a) and width, a/W=0,6. The experimental tests utilized a 250 kN MTS universal machine. Conventional tensile tests were also performed to determine the tensile properties for the tested material: yield strength of 550MPa, tensile strength of 676MPa and elongation of 27% (gage length of 50 mm). The Charpy V-notch impact tests also provided and absorbed energy of 220J at 0ºC. The metallographic analysis showed colonies of perlite and MA constituent islands in a ferrite matrix. This experimental characterization provides additional toughness and mechanical data against which the general behavior of X80 class pipeline steel can be compared.

[pt] Compreender como analisar trincas é essencial para a indústria petroquímica evitar qualquer incidente de uma forma econômica. Normas de Integridade Estrutural fornecem procedimentos conservadores para avaliar componentes trincados como tubulações e vasos de pressão. Portanto, previsões de cargas criticas foram calculadas assumindo uma placa com trinca passante seguindo procedimentos dos níveis 2 e 3 da API 579. Para comparação, testes experimentais foram realizados para avaliar o conservatismo da norma em falha por rasgamento dúctil. Além disso, a tenacidade à fratura foi medida por meio do JIc e curva J-R. A técnica usada durante o processo de fratura foi o método de flexibilidade elástica com descarregamento e carregamentos sequenciais. Adicionalmente, efeito de geometria e tipo de carregamento, os quais possuem grande influência nas medições de tenacidade, também foram avaliados usando conceitos da mecânica da fratura elastoplástica. O material utilizado nesse trabalho foi o API 5L X80, que é um aço de Alta Resistencia e Baixa Liga (ARBL) bifásico desenvolvido para tubulações aplicáveis em aguas profundas. Os ensaios experimentais de medição de tenacidade usando corpos de prova SE(B), que possuem média-alta restrição plástica, foram testados seguindo procedimentos da ASTM E1820-17. Já os experimentos usando corpos de prova SE(T), que possuem baixa restrição plástica, foram realizados considerando procedimentos da literatura. / [en] Understanding how to analyze cracks is essential for the petrochemical industry to avoid accidents or incidents in a safe and economical way. Structural Integrity standards provide conservative procedures to assess the actual strength of cracked components like pipes and pressure vessels. Therefore, critical loads predictions were computed on a plate with a through-wall crack following level 2 and 3 of the fitness-for-service guide API 579. For comparison, experimental tests were performed to evaluate the standard conservatism on a ductile tearing type of failure. Furthermore, the fracture toughness of the steel was measured through standard JIc tests and material s resistance curves (J-R curve). The technique used during the fracturing process was the elastic compliance method with unloading/reloading sequences. Additionally, the effects of the specimen s geometry and the type of loading, which can significantly change the value of its toughness, were also analyzed using concepts of elastoplastic fracture mechanics. The material used in this work was the API 5L X80, which is a High Strength Low Alloy (HSLA) dual-phase steel developed for deepwater pipelines. The fracture toughness measurement tests using SE(B) specimens, which have a medium-to-high plastic constraint, followed the ASTM E1820-17 procedures. The experiments with SE(T) specimens, which present a low plastic restriction, considered literature procedures.