Application of SEM-EBSD for Measurement of Plastic Strain Fields Associated With Weld Metal Hydrogen Assisted Cold Cracking

2012 ◽  
Author(s):  
I. H. Brown ◽  
W. L. Costin ◽  
F. Barbaro ◽  
R. Ghomashchi
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Weld Metal ◽  
Cold Cracking ◽  
Low Alloy Steels ◽  
Plastic Strains ◽  
Shielded Metal Arc Welding ◽  
Electron Backscattered Diffraction ◽  
Construction Time ◽  
Girth Welds

The requirement for more efficient use of materials for pipelines has lead to the application of high strength low alloy steels such as X70 and X80 in pipelines. As the strength of these alloys has increased so has the risk of hydrogen assisted cold cracking (HACC). In Australia to minimize construction time, the root runs of girth welds are produced by shielded metal arc welding using cellulosic electrodes without either pre or post heating. Well defined welding criteria have been developed and are incorporated into the weld procedures for the elimination of HACC in the heat affected zone but the risk of cracking to the weld metal is still of concern. It has been reported that plastic deformation occurs prior to the formation of hydrogen cracks in weld metal. Therefore the evaluation of plastic strains at the micro- and nano-scale and their relationship to the weld metal microstructure could be of great significance in assessing the susceptibility of welds to weld metal hydrogen assisted cold cracking (WMHACC). A method for analysing plastic strains on the micro- and nano-scales using electron backscattered diffraction (EBSD) has been developed. This technique is based on the degradation and rotation of diffraction patterns as a result of crystallographic lattice distortion resulting from plastic deformation. The analysis can be automated to produce an Image Quality (IQ) map in order to relate the spatial distribution of plastic deformation to microstructural features e.g. grains or cracks. The development and assessment of techniques using Scanning Electron Microscopy (SEM) and EBSD for the determination of local plastic strain distribution in E8010 weld metal used for the root pass of X70 pipeline girth welds is discussed.

Girth Weld Qualification for High Strain Pipeline Applications

2005 ◽  
Author(s):  
Martin W. Hukle ◽  
Agnes M. Horn ◽  
Douglas S. Hoyt ◽  
James B. LeBleu
Keyword(s):  
Plastic Strain ◽  
Weld Metal ◽  
Heat Affected Zone ◽  
High Strain ◽  
Flaw Size ◽  
Small Scale ◽  
Plastic Strains ◽  
Strain Capacity ◽  
Metal Properties ◽  
Girth Welds

Pipeline applications that are subject to global plastic strains require specific testing and qualification programs intended to verify the strain capacity of the girth welds. Such strain demands are generally beyond the limits of standard ECA applicability which normally cover demands up to 0.5% strain. Therefore, qualification of welding procedures for high strain environments require significantly more testing than weld procedures intended for stress-based designs. The plastic strain capacity of girth welds is a function of the pipe and weld metal properties, as well as the maximum flaw size allowable in the girth weld. Specific weld metal/heat affected zone properties, based on small scale testing, should be combined with full scale curved wide plate testing of girth welds that include artificial flaws.

scholarly journals Influence of Temperature and Plastic Strain on Deformation Mechanisms and Kink Band Formation in Homogenized HfNbTaTiZr

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 81
Author(s):  
Hans Chen ◽  
Theresa Hanemann ◽  
Sascha Seils ◽  
Daniel Schliephake ◽  
Aditya Srinivasan Tirunilai ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Kink Band ◽  
Deformation Mechanisms ◽  
Large Temperature ◽  
Plastic Strains ◽  
Compression Tests ◽  
Band Formation ◽  
Influence Of Temperature ◽  
Temperature Range

Due to its outstanding ductility over a large temperature range, equiatomic HfNbTaTiZr is well-suited for investigating the influence of temperature and plastic strain on deformation mechanisms in concentrated, body centered cubic solid solutions. For this purpose, compression tests in a temperature range from 77 up to 1073 K were performed and terminated at varying plastic strains for comparison of plastic deformation behavior. The microstructure and chemical homogeneity of a homogenized HfNbTaTiZr ingot were evaluated on different length scales. The compression tests reveal that test temperature significantly influences yield strength as well as work hardening behavior. Electron backscatter diffraction aids in shedding light on the acting deformation mechanisms at various temperatures and strains. It is revealed that kink band formation contributes to plastic deformation only in a certain temperature range. Additionally, the kink band misorientation angle distribution significantly differs at varying plastic strains.

Effect of Pipe and Weld Metal Post-Yield Characteristics on Plastic Straining Capacity of Axially Loaded Pipelines

2004 ◽  
Author(s):  
Rudi Denys ◽  
Wim De Waele ◽  
Anton Lefevre
Keyword(s):  
Mechanical Properties ◽  
Weld Metal ◽  
Large Scale ◽  
Important Variable ◽  
Plastic Strains ◽  
Deformation Characteristics ◽  
Girth Welds ◽  
Critical Regions ◽  
Large Scale Tests ◽  
Metal Post

Girth welds in pipelines subject to longitudinal plastic tensile strains are critical regions of the pipeline. As girth welds might contain flaws of some form or other, it is of paramount interest to have a thorough understanding of the deformation characteristics of girth welds in the post-yield loading range. The response of a defective weld to plastic strains depends on many variables. While toughness is an important variable, large-scale tests demonstrate that the plastic straining capacity is directly affected by the mechanical properties of the materials surrounding the defect. The purpose of this paper is to describe the effect of the interrelation between the pipe and weld metal post-yield characteristics on the straining capacity of girth welds containing a defect.

An Overview of Strain-Based Fracture Assessment of Pipelines

2018 ◽  
Author(s):  
Guiyi Wu ◽  
Longjie Wang
Keyword(s):  
Plastic Deformation ◽  
Fracture Mechanics ◽  
Test Data ◽  
Oil And Gas ◽  
Full Scale ◽  
Plastic Strains ◽  
Offshore Pipelines ◽  
Pipeline Networks ◽  
Fracture Assessment ◽  
Girth Welds

Development of remote energy requires large pipeline networks to be placed in more challenging environments such as offshore in deeper waters or on land in Arctic or near-Arctic locations. Pipeline installed and operated in such regions may be subjected to large plastic strains. Engineering critical assessments (ECA) are commonly carried out during design, installation and operation of offshore pipelines to determine acceptable flaw sizes in pipeline girth welds. A number of fracture mechanics-based procedures are available for ECA of pipeline girth welds. Most of these methods are primarily stress-based assessments and are therefore not directly applicable to cases where the displacement-/strain-controlled loading generates large amounts of plastic deformation. For such cases, strain-based fracture assessment for pipeline/girth welds should be carried out instead. However, limited guidance on strain-based assessment is available in the current codes and standards used primarily by the oil and gas industries. This paper reviews the existing strain-based fracture assessment methods, and reports the results of preliminary studies performed to compare the methods reviewed with the available full-scale pipe test data.

Plastic Deformation in Microtomed Sections

1971 ◽  
Vol 29 ◽  
pp. 458-459
Author(s):  
J. Temple Black
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Applied Stress ◽  
Elastic Strain ◽  
High Strain ◽  
Tool Material ◽  
Cutting Edge ◽  
Material Structure ◽  
Geometrical Constraints

The output of the ultramicrotomy process with its high strain levels is dependent upon the input, ie., the nature of the material being machined. Apart from the geometrical constraints offered by the rake and clearance faces of the tool, each material is free to deform in whatever manner necessary to satisfy its material structure and interatomic constraints. Noncrystalline materials appear to survive the process undamaged when observed in the TEM. As has been demonstrated however microtomed plastics do in fact suffer damage to the top and bottom surfaces of the section regardless of the sharpness of the cutting edge or the tool material. The energy required to seperate the section from the block is not easily propogated through the section because the material is amorphous in nature and has no preferred crystalline planes upon which defects can move large distances to relieve the applied stress. Thus, the cutting stresses are supported elastically in the internal or bulk and plastically in the surfaces. The elastic strain can be recovered while the plastic strain is not reversible and will remain in the section after cutting is complete.

Effect of Shield Gas Composition on Cold Cracking Susceptibility of YS 600 MPa Flux Cored Arc Weld Metal

2015 ◽  
Vol 53 (7) ◽  
pp. 480-487 ◽  
Author(s):  
Namhyun Kang ◽  
Guo Xian ◽  
Myungjin Lee ◽  
Junghoon Lee
Keyword(s):  
Weld Metal ◽  
Cold Cracking ◽  
Gas Composition

UNIFLUX VCM 125

Alloy Digest ◽  
1978 ◽  
Vol 27 (1) ◽  
Keyword(s):  
Carbon Dioxide ◽  
Fracture Toughness ◽  
Weld Metal ◽  
Heat Treating ◽  
Carbon Steels ◽  
Low Alloy Steels ◽  
Electrode Wire ◽  
Molybdenum Steel ◽  
Alloy Steels ◽  
Welding Electrode

Abstract UNIFLUX VCM 125 is a continuous flux-cored welding electrode (wire) that is used to deposit 1 1/4% chromium-1/2% molybdenum steel for which it was developed. Welding is protected by a shielding atmosphere of 100% carbon dioxide. This electrode also may be used to weld other low-alloy steels and carbon steels; however, the weld metal may differ somewhat from 1 1/4% chromium-1/2% molybdenum because of weld-metal dilution. When Uniflux VCM 125 is used to weld 1 1/4% chromium-1/2% molybdenum steel, it provides 95,000 psi tensile strength at 70 F and 24 foot-pounds Charpy V-notch impact at 40 F. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as heat treating, machining, and joining. Filing Code: SA-340. Producer or source: Unicore Inc., United Nuclear Corporation.

Deformation and Heat Treatment of Cold Drawn Gold

2007 ◽  
Vol 550 ◽  
pp. 289-294
Author(s):  
Suk Hoon Kang ◽  
Jae Hyung Cho ◽  
Joon Sub Hwang ◽  
Jong Soo Cho ◽  
Yong Jin Park ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Plastic Deformation ◽  
Mechanical Stability ◽  
Ion Beam ◽  
Quantitative Measure ◽  
Electron Backscattered Diffraction ◽  
Conducting Path ◽  
Deformation And Heat Treatment ◽  
Gold Wires

Cold drawn gold wires are widely applied in electronic packaging process to interconnect micro-electronic components. They basically provides a conducting path for electronic signal transfer, and experience thermo-mechanical loads in use. The mechanical stability of drawn gold wires is a matter of practical concern in the reliable functioning of electronic devices. It is known that mechanical properties of materials are deeply related to the microstructure. With appropriate control of deformation and heat processes, the mechanical properties of final products, such as tensile strength and elongation can be improved. Severe plastic deformation by torsion usually contributes to grain refinement and increment of strength. In this study, microstructure variations with torsion strain followed by drawing and heat treatment were investigated. Analyses by focused ion beam (FIB) and electron backscattered diffraction (EBSD) were carried out to characterize the effect of deformation and heat treatment on the drawn gold wires. Pattern quality of EBSD measurements was used as a quantitative measure for plastic deformation.

Development of Distortion Modeling Methods for Large Welded Structures

2010 ◽  
Author(s):  
Y. P. Yang ◽  
H. Castner ◽  
N. Kapustka
Keyword(s):  
Thermal Analysis ◽  
Plastic Strain ◽  
Computation Time ◽  
Thermomechanical Analysis ◽  
Global Model ◽  
Temperature History ◽  
Plastic Strains ◽  
Local Models ◽  
Welded Structures ◽  
Modeling Methods

Two distortion modeling methods, mapping plastic strain and lump-pass modeling, were developed and validated for predicting distortion on large welded structures to reduce the computation time. The mapping plastic-strain method requires two kinds of models, local models and a global model. The local models are analyzed to predict plastic strains and the global model is analyzed by mapping the plastic strains to predict distortions. The lump-pass modeling method includes two kinds of analyses: a thermal analysis and a thermomechanical analysis. The thermal analysis is conducted to predict temperature history. The thermomechanical analysis is performed to predict distortion by inputting the predicted temperature history.

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