Sensitivity of Plastic Response of Defective Pipeline Girth Welds to the Stress-Strain Behavior of Base and Weld Metal

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
Stijn Hertelé ◽  
Wim De Waele ◽  
Rudi Denys ◽  
Matthias Verstraete
Keyword(s):  
Tensile Stress ◽  
Yield Stress ◽  
Driving Force ◽  
Uniform Elongation ◽  
Element Model ◽  
Ultimate Tensile Stress ◽  
Weld Strength ◽  
Plastic Strains ◽  
Crack Driving Force ◽  
Strain Behavior

One of the key parameters influencing the acceptability of a pipeline girth weld defect subjected to remote plastic deformation is the strength mismatch between weld and base metal. However, no single definition exists for weld strength mismatch, as it can be defined either on the basis of yield stress, ultimate tensile stress or any intermediate flow stress. To investigate the relevance of such definitions, the authors have performed a series of analyses of curved wide plate tests, using a validated parametric finite element model. The results indicate that, whereas yield stress overmatch determines crack driving force for small plastic strains, ultimate tensile stress overmatch is the more important parameter for advanced plastic strains and determines the eventual failure mode. Further, the strain capacity and exact crack driving force curve are additionally determined by uniform elongation and crack growth resistance.

Sensitivity of Plastic Response of Defective Pipeline Girth Welds to the Stress-Strain Behavior of Base and Weld Metal

2011 ◽  
Author(s):  
Stijn Hertele´ ◽  
Wim De Waele ◽  
Rudi Denys ◽  
Matthias Verstraete
Keyword(s):  
Tensile Stress ◽  
Yield Stress ◽  
Driving Force ◽  
Uniform Elongation ◽  
Element Model ◽  
Ultimate Tensile Stress ◽  
Weld Strength ◽  
Plastic Strains ◽  
Crack Driving Force ◽  
Strain Behavior

One of the key parameters influencing the acceptability of a pipeline girth weld defect subjected to remote plastic deformation is the strength mismatch between weld and base metal. However, no single definition exists for weld strength mismatch, as it can be defined either on the basis of yield stress, ultimate tensile stress or any intermediate flow stress. To investigate the relevance of such definitions, the authors have performed a series of analyses of curved wide plate tests, using a validated parametric finite element model. The results indicate that, whereas yield stress overmatch determines crack driving force for small plastic strains, ultimate tensile stress overmatch is the more important parameter for advanced plastic strains and determines the eventual failure mode. Further, the strain capacity and exact crack driving force curve are additionally determined by uniform elongation and crack growth resistance.

scholarly journals Evaluation of a finite element model for SENT testing of welded connections

2016 ◽  
Vol 7 (1) ◽  
pp. 7
Author(s):  
M. De Visschere ◽  
Sameera Naib ◽  
Wim De Waele ◽  
Stijn Hertelé
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Driving Force ◽  
Element Model ◽  
Potential Effect ◽  
Strength Properties ◽  
Weld Strength ◽  
Force Response ◽  
Crack Driving Force ◽  
Crack Tip Constraint

The SENT test has recently gained popularity for the characterization of the ductile tearing resistance of welded connections under low crack tip constraint. In addition to this practical purpose, Soete Laboratory adopts the SENT test as a tool to investigate effects of weld strength heterogeneity on the crack driving force response of weld defects. The numerical aspect of this investigation relies on a finite element model of a SENT specimen in which the heterogeneous strength properties of the weld region are defined on the basis of an imported hardness map. This paper evaluates the model in two respects. First, crack driving force response is validated on the basis of an experimental SENT test result of a non-welded specimen. Second, the potential effect of the transfer function between hardness and constitutive properties is illustrated. It is concluded that more work is required to improve the feasibility of weld hardness data as a means to characterize effects of weld strength heterogeneity.

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].

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.

The effect of heat treatment on mechanical properties of 42CrMo4 steel

2020 ◽  
Vol 1 (98) ◽  
pp. 5-10
Author(s):  
A. Çalık ◽  
O. Dokuzlar ◽  
N. Uçar
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Tensile Stress ◽  
Yield Stress ◽  
Impact Energy ◽  
Ultimate Tensile Stress ◽  
Tempering Temperature ◽  
Heat Treated ◽  
Quenching Process ◽  
42Crmo4 Steel

Purpose: In this study, the effect of heat treatment on the microstructure and mechanical properties of 42CrMo4 steel were investigated. Design/methodology/approach: The samples were annealed at 860°C for 120 min. followed by oil quenching and then tempered at temperatures between 480 and 570°C for 120 min. The microstructure of untreated 42CrMo4 steel mainly consists of pearlite and ferrite whereas the microstructure was found to be as a martensitic structure with a quenching process. Findings: The results showed that there is an increase in yield stress, ultimate tensile stress, hardness and impact energy, while elongation decreases at the end of the quenching process. Conversely, yield stress, ultimate tensile stress and hardness decrease slightly with the increasing of tempering temperature, while elongation and impact energy increase. Research limitations/implications: Other types of steels can be heat treated in a wider temperature range and the results can be compared. Practical implications: It is a highly effective method for improving the mechanical properties of heat treatment materials. Originality/value: A relationship between the mechanical properties and the microstructure of materials can be developed. The heat treatment is an effective method for this process.

A STUDY OF MICROSTRUCTURE AND TENSILE PROPERTIES OF PROTON BEAM IRRADIATED Al–Mg–Si ALLOY

2011 ◽  
Vol 25 (12) ◽  
pp. 1645-1652
Author(s):  
I. M. GHAURI ◽  
NAVEED AFZAL ◽  
YASIR IDREES
Keyword(s):  
Tensile Stress ◽  
Tensile Properties ◽  
Yield Stress ◽  
Exposure Time ◽  
Tensile Deformation ◽  
Irradiation Time ◽  
Testing Machine ◽  
Xrd Analysis ◽  
Ultimate Tensile Stress ◽  
Mev Protons

In the present paper, the microstructure and tensile properties of Al – Mg – Si alloy irradiated with 2 MeV protons for 5, 10, 20, and 40 mins at 300 K are investigated. The microstructure of irradiated specimens, observed using metallurgical microscope, shows that aspirates are emitted out from the surface of irradiated specimens, which take the form of clusters and/or precipitates with increase of exposure time. The tensile behavior of irradiated specimens was investigated using universal testing machine and compared with that of unirradiated one. The yield stress, ultimate tensile stress and % elongations remain unchanged after 5 and 10 mins of irradiation. However with an increase of irradiation time up to 20 mins, an increase in yield stress, ultimate tensile stress and decrease in % elongation was observed. With further increase of exposure time to 40 mins, the increase in yield stress and decrease in plasticity became more prominent. The results of stress relaxation tests performed during the tensile deformation have also been presented. The XRD analysis reveals that the microstructural changes controlling the tensile properties in irradiated samples appear to be physical rather than chemical.

Weld Strength Mismatch in Strain Based Flaw Assessment: Which Definition to Use?

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Stijn Hertelé ◽  
Wim De Waele ◽  
Rudi Denys ◽  
Matthias Verstraete ◽  
Koen Van Minnebruggen ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Driving Force ◽  
Experimental Validation ◽  
Weld Strength ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Strength Based ◽  
Key Factor ◽  
Girth Welds

Weld strength mismatch is a key factor in the strain based assessment of flawed girth welds under tension. A strength overmatching weld shields potential flaws within the weld itself from remotely applied deformations and consequently reduces crack driving force. Although this effect has been recognized for decades, different weld strength overmatch definitions exist, and it is not yet fully established which of those is most relevant to a strain based flaw assessment. In an effort to clarify this unsolved question, the authors have performed a large series of parametric finite element analyses of curved wide plate tests. This paper provides an experimental validation of the model and subsequently discusses representative results. It is found that crack driving force is influenced by the shape of the pipe metals' stress–strain curves, which influences the representativeness of two common mismatch definitions (based on yield strength and on ultimate tensile strength). Effects of strength mismatch on strain capacity of a flawed girth weld are best described on the basis of a flow stress, defined as the average of yield and ultimate tensile strength. Based on the observations, a framework for a new strain capacity equation is proposed.

Serrated Flow in an 11Cr Ferritic/Martensitic Steel

2014 ◽  
Vol 894 ◽  
pp. 125-128 ◽  
Author(s):  
Zhi Qiang Xu ◽  
Yin Zhong Shen ◽  
Bo Ji ◽  
Sheng Zhi Li ◽  
Ai Dang Shan
Keyword(s):  
Tensile Stress ◽  
Strain Rate ◽  
Yield Stress ◽  
Room Temperature ◽  
Martensitic Steel ◽  
Flow Behavior ◽  
Tensile Tests ◽  
Ultimate Tensile Stress ◽  
Strain Rates ◽  
Serrated Flow

Serrated flow behavior of an 11Cr ferritic/martensitic steel was investigated through tensile tests at initial strain rates of 2×10-510-3 s-1 at temperatures ranging from room temperature to 973 K. Serrated flow occurred at three temperature regions of room temperature, 573 K and 773973 K when tensile tests were conducted at a strain rate of 2×10-4 s-1. Serrations are also observed in the steel during tension at temperatures of 573 K and 773973 K at a strain rate of 2×10-5 s-1. With increasing tensile temperature, the yield stress and ultimate tensile stress of the steel were gradually decreased and quickly dropped at temperatures higher than 773 K, while the elongation of the steel was decreased to a minimum at 600 K, and then dramatically increased at temperatures higher than 600 K.

scholarly journals A critical review of the influence of hydrogen on the mechanical properties of medium-strength steels

2013 ◽  
Vol 31 (3-6) ◽  
pp. 85-103 ◽  
Author(s):  
Qian Liu ◽  
Andrej Atrens
Keyword(s):  
Tensile Stress ◽  
Yield Stress ◽  
Stress Ratio ◽  
Ultimate Tensile Stress ◽  
Fatigue Properties ◽  
Lower Yield ◽  
Good Resistance ◽  
Microstructural Characteristics ◽  
Lower Yield Stress ◽  
Medium Strength

AbstractAs medium-strength steels are promising candidates for the hydrogen economy, it is important to understand their interaction with hydrogen. However, there are only a limited number of investigations on the behavior of medium-strength steels in hydrogen. The existing literature indicates that the influences of hydrogen on the tensile properties of medium-strength steels are mainly the following: (i) the steel can be hardened by hydrogen, as demonstrated by an increase in the yield stress or ultimate tensile stress; (ii) some steels can be embrittled by hydrogen, as revealed by lower yield stress or ultimate tensile stress; (iii) in most cases, these steels may experience hydrogen embrittlement (HE), as indicated by a reduction in ductility. The degree of HE mainly depends on the test conditions and the steel. The embrittlement can lead to catastrophic brittle fracture in service. The influence of hydrogen on the fatigue properties of medium-strength steels is dependent on many factors such as the stress ratio, temperature, yield stress of the steel, and test frequency. Generally, the hydrogen influence on fatigue limit is small, whereas hydrogen can accelerate the fatigue crack growth rate, leading to a shorter fatigue life. Inclusions are an important factor influencing the properties of medium-strength steels in the presence of hydrogen. However, it is not possible to predict the influence of hydrogen for any particular steel that has not been experimentally evaluated or to predict service performance. It is not known why similar steels can have different behavior, ranging from good resistance to significant embrittlement. A better understanding of the microstructural characteristics is needed.

Weld Strength Mismatch in Strain Based Flaw Assessment: Which Definition to Use?

2012 ◽  
Author(s):  
Stijn Hertelé ◽  
Wim De Waele ◽  
Rudi Denys ◽  
Matthias Verstraete ◽  
Koen Van Minnebruggen ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Driving Force ◽  
Experimental Validation ◽  
Weld Strength ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Strength Based ◽  
Key Factor ◽  
Girth Welds

Weld strength mismatch is a key factor in the strain based assessment of flawed girth welds under tension. A strength overmatching weld shields potential flaws within the weld itself from remotely applied deformations and consequently reduces crack driving force. Although this effect has been recognized for decades, different weld strength overmatch definitions exist and it is not yet fully established which of those is most relevant to a strain based flaw assessment. In an effort to clarify this unsolved question, the authors have performed a large series of parametric finite element analyses of curved wide plate tests. This paper provides an experimental validation of the model and subsequently discusses representative results. It is found that crack driving force is influenced by the shape of the pipe metals’ stress-strain curves, which influences the representativeness of two common mismatch definitions (based on yield strength and on ultimate tensile strength). It can be concluded from further observations that effects of strength mismatch on strain capacity of a flawed girth weld are best described on the basis of a flow stress, defined as the average of yield and ultimate tensile strength. Based on the observations, a framework for a new strain capacity equation is proposed.

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