Effect of Plastic Deformation on Occurrence of Abnormal Fracture During DWTT

2012 ◽  
Author(s):  
Taishi Fujishiro ◽  
Takuya Hara ◽  
Shuji Aihara
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Equivalent Plastic Strain ◽  
High Strength ◽  
American Petroleum Institute ◽  
Test Method ◽  
Bending Deformation ◽  
Hammer Impact ◽  
Shear Area ◽  
The Impact

Demand for natural gas using LNG and pipelines to supply the world’s gas markets is increasing. Under the large demand for high-strength linepipe, crack arrestability is one of the most important properties. DWTT (Drop Weight Tear Test) is the major test method for evaluating crack arrestability. Generally, a DWTT shear area of 85% or higher is required as the acceptance criteria, such as those of the API (American Petroleum Institute). In high-toughness linepipe steels, the abnormal fracture frequently occurs in DWTT. Abnormal fracture is defined as a cleavage fracture on the hammer side. However, the mechanism for occurrence of the abnormal fracture during DWTT has not been fully clarified. This paper describes the effect of plastic deformation on occurrence of abnormal fracture during DWTT using various steels with different microstructures. Each DWTT was carried out at the same test temperature using 20 mm plates with approximately the same tensile strength. This paper describes the deformation during DWTT, which consists of deformation caused by hammer impact, bending compression, and bending tension. The deformation due to the impact of the hammer during DWTT on a 20 mm plate was limited, and the location affected by the hammer impact did not correspond to that where abnormal fracture occurred. Moreover, the equivalent plastic strain from bending deformation was dominant as compared with that of hammer impact regardless of the microstructure. This suggests that abnormal fracture occurred by exceeding the critical equivalent plastic strain due to the bending deformation.

Mechanical Properties of Vanadium Microalloyed High-Strength ASTM A694 Forgings

2017 ◽  
Author(s):  
K. C. Baker ◽  
R. M. Thompson ◽  
T. C. Gorrell
Keyword(s):  
Chemical Composition ◽  
Oil And Gas ◽  
Charpy Impact ◽  
High Strength ◽  
Oil And Gas Industry ◽  
Heat Treating ◽  
Manganese Steel ◽  
Material Test ◽  
Shear Area ◽  
The Impact

Recent upstream oil and gas industry experience has raised attention to substandard properties with high strength carbon steel forgings manufactured to the requirements of ASTM A694 and MSS-SP-44. As part of an internal investigation into quality of commodity pipeline flanges, three flanges certified as ASTM A694 grade F60 to F70, were purchased off-the-shelf from three different manufacturers for microstructural and mechanical property investigation. All three flanges were supplied with material test certificates indicating acceptable material properties. Tensile and Charpy impact specimens were extracted from various locations and orientations in each flange. All three flanges failed to meet yield strength requirements for the specified grade. The impact energy and shear area values were well below those reported on the material test certificates. The discrepancy between the sacrificial testing results and the material test certificates is attributed to the use of separately forged test blocks for quality testing instead of integral prolongations or a sacrificial production part, which is permitted by ASTM A694 and MSS-SP-44. Further investigation was made into the chemical composition and heat treating practices. The chemical composition can be characterized as high strength, low alloy steel (HSLA) by virtue of 0.05–0.08 wt. pct. vanadium added to a carbon-manganese steel with CE(IIW) ranging from 0.43 to 0.45. Advanced microscopy showed that the morphology of the vanadium precipitates was inadequate as a strengthener and deleterious to Charpy impact properties for the size of the flanges and the heat treatment practices applied.

Evaluation of Ductile Cracking Criterion for Grade X100 Linepipe and Relationship to Large Scale Fracture Behavior

2003 ◽  
Author(s):  
Nobuyuki Ishikawa ◽  
Shigeru Endo ◽  
Alan Glover ◽  
David Horsley ◽  
Masao Toyoda
Keyword(s):  
Plastic Strain ◽  
Ductile Fracture ◽  
Fracture Behavior ◽  
Large Scale ◽  
Notch Root ◽  
Equivalent Plastic Strain ◽  
High Strength ◽  
Fracture Initiation ◽  
Linepipe Steels ◽  
Ductile Fracture Initiation

Recent developments in the manufacturing process of steel plate for high strength linepipe have enabled superior toughness to prevent brittle fracture of the pipe body. Techniques for non-destructive inspection have also improved, and large flaws that could lead to brittle fracture are highly unlikely in recent high strength pipelines. However, large amounts of plastic deformation can be expected in seismic or permafrost regions. Prevention of ductile fracture of the pipe body or weldment therefore becomes a key issue in defining the tensile strain limit. Ductile fracture is considered to occur by growth and coalescence of voids, and is affected by stress triaxiality and plastic straining at the cracked region. Although many studies have been carried out to evaluate ductile cracking criteria, its transferability to large-scale fracture behavior has not been thoroughly investigated. In this study, ductile cracking of high strength linepipe steels, Grade X80 and X100, was investigated. Notched round bar specimens with different notch root radii were tested to determine the precise conditions for initiation of ductile fracture. Stress and strain conditions at the notch regions were evaluated by FE analysis, and the “critical equivalent plastic strain” was defined at conditions corresponding to ductile fracture initiation in the experimental small specimen tests. Ductile crack initiation behavior was also determined for wide plate test specimens by making close observations of the notch root area. 3-D FE analysis of the wide plate tensile test showed that the equivalent plastic strain at the point of ductile fracture initiation was in close agreement with that in the notched round bas specimen. Thus, the “critical equivalent plastic strain,” determined by small notched round bar specimens, can be considered as a transferable criterion to predict large-scale fracture behavior in wide plate tests. Concepts of strain based design in terms of preventing ductile failure from a surface flaw by applying critical strain to cracking were also discussed in this paper. Results were compared to conventional grade linepipe steels and structural steels, showing that recent high strength linepipe steels have higher resistance to ductile cracking than conventional structural steels. In addition, 3-D FE analyses were used in a parametric study to determine the effects of Y/T and uniform strain on the onset of ductile cracking behaviour. The results of these analyses show the relative importance of materials properties on the resistance to ductile cracking.

scholarly journals Impact Tests of UHSS Steel Welded Joints Using the Drop - Tower Impact Drop Method

2019 ◽  
Vol 19 (3) ◽  
pp. 19-31
Author(s):  
J. Dorożyński ◽  
J. Nowacki ◽  
A. Sajek
Keyword(s):  
Impact Strength ◽  
Welded Joints ◽  
Impact Test ◽  
Gma Welding ◽  
High Strength ◽  
Test Method ◽  
Drop Tower ◽  
Current Application ◽  
Impact Tests ◽  
The Impact

AbstractThe article characterizes the impact test method using Drop-Tower Impact Test with the registration of the value of force and energy of breaking. Based on sources, the possibilities and scope of the current application of this method were determined and the current state of knowledge on the results of these tests was reviewed. In order to determine the possibility of using the method in impact tests of high strength steel joints, investigations of hybrid PTA - GMA welding conditions on impact strength of joints of MART S1300QL steel were carried out. In particular, the influence of t8/5 cooling time on the impact strength of welded joints by the Drop - Tower Impact Test method was determined. It has been shown that the use of dropping machine with computer-based registration of breaking force and energy values was possible in the case of impact strength testing of UHSS welded joints and enabled precise analysis of the energy distribution dynamics absorbed by the tested.

Non-destructive method to investigate the hardness-plastic strain relationship in cyclically deformed structural steel elements

2014 ◽  
Vol 47 (3) ◽  
pp. 181-189 ◽  
Author(s):  
Hassan Nashid ◽  
W.G. Ferguson ◽  
G.C. Clifton ◽  
M. Hodgson ◽  
M. Battley ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Hardness Test ◽  
Test Method ◽  
Braced Frames ◽  
Eccentrically Braced Frames ◽  
Inelastic Demand ◽  
High Level ◽  
Hot Rolled ◽  
Non Destructive

A non-destructive hardness testing method is being developed to determine plastic strain in steel elements that have been subjected to inelastic seismic loading. The focus of this study is on the active links of eccentrically braced frames (EBFs). The 2010/2011 Christchurch earthquake series, especially the very intense February 22 shaking, was the first earthquake worldwide to push complete EBF systems into their inelastic state, generating a moderate to high level of plastic strain in EBF active links for a range of buildings from 3 to 23 storeys in height. Plastic deformation was confined to the active links. This raised two important questions: 1) what was the extent of plastic deformation; and 2) what effect does that have to post-earthquake steel properties? To answer these questions a range of actions is being taken. A non-destructive hardness test method is being developed to determine a relationship between hardness and plastic strain inactive link beams. Active links from the earthquake affected, 23-storey Pacific Tower building in Christchurch has been hardness and material property tested to determine the changes in the steel, and cyclic testing of active links to defined levels of inelastic demand is underway. Test results to date show clear evidence that the hardness based method is able to give a good relationship between hardness measurements and plastic strain. This paper presents recent significant findings from this project. The principal of these is the discovery that hot rolled steel tested beams, all carry manufacturing induced plastic strains, in regions of the webs, of up to 5%.

Formulation of Equivalent Plastic Strain Accumulated in Rotating Bending Process of Metal Tubes for Severe Plastic Deformation

2014 ◽  
Vol 887-888 ◽  
pp. 907-911
Author(s):  
Zi Cheng Zhang ◽  
Kenichi Manabe ◽  
Tsuyoshi Furushima ◽  
Kazuo Tada
Keyword(s):  
Plastic Deformation ◽  
Stress Distribution ◽  
Plastic Strain ◽  
Severe Plastic Deformation ◽  
Significant Influence ◽  
Equivalent Plastic Strain ◽  
Stress And Strain ◽  
Bending Process ◽  
Rotating Bending ◽  
And Control

The newly proposed rotating bending process of metal tubes is a novel kind of Severe Plastic Deformation (SPD) process, which is expected to refine and control the microstructure of metallic tubular materials. The stress distribution and accumulated equivalent plastic strain of deformation part have a significant influence on the microstructure refinement and control of metal tubes during the rotating bending process. The present study focused on the analysis of stress and strain of deformation part during rotating bending process of metal tubes. The model of the deforming metal tubes was proposed. The formulas for determining the stress and accumulated equivalent plastic strain were successfully achieved by analyzing the deformation of metal tubes during rotating bending process.

Biaxial Tensile Test of High Strength Steel Sheet for Large Plastic Strain Range

2012 ◽  
Vol 504-506 ◽  
pp. 59-64 ◽  
Author(s):  
Tomoyuki Hakoyama ◽  
Toshihiko Kuwabara
Keyword(s):  
Plastic Strain ◽  
High Strength Steel ◽  
Deformation Behavior ◽  
Equivalent Plastic Strain ◽  
Strain Range ◽  
High Strength ◽  
Test Material ◽  
Strain Rates ◽  
Stress Space ◽  
Plastic Strain Range

Deformation behavior of high strength steel with a tensile strength of 590 MPa under biaxial tension was investigated for a work equivalent plastic strain range of 0.002 0.16. The test material was bent and laser welded to fabricate a tubular specimen with an inner diameter of 44.6mm and wall thickness of 1.2 mm. Using a servo-controlled tension-internal pressure testing machine, many linear stress paths in the first quadrant of stress space were applied to the tubular specimens. Moreover, biaxial tensile tests using a cruciform specimen were performed to precisely measure the deformation behavior of the test material for a small strain range following initial yielding. True stress-true plastic strain curves, contours of plastic work in stress space and the directions of plastic strain rates were measured and compared with those calculated using selected yield functions. The plastic deformation behavior up to an equivalent plastic strain of 0.16 was successfully measured. The Yld2000-2d yield function most closely predicts the general work contour trends and the directions of plastic strain rates of the test material.

An experimental and numerical investigation on impact spot welding of metallic plates using gas mixture detonation technique

2020 ◽  
pp. 146442072098232
Author(s):  
Sedigheh Hosseinzadeh ◽  
Hashem Babaei ◽  
Tohid Mirzababaie Mostofi
Keyword(s):  
Numerical Simulation ◽  
Shear Stress ◽  
Plastic Strain ◽  
Spot Welding ◽  
Equivalent Plastic Strain ◽  
Welding Process ◽  
Gas Mixture ◽  
The Impact ◽  
Base Plates ◽  
Metallic Plates

In this paper, the impact spot welding of metallic plates was investigated both experimentally and numerically using a single-stage gas mixture detonation apparatus. The impact spot welding process was carried out on aluminum alloy and steel materials using rigid steel projectiles. In this process, the mixture of oxygen and acetylene was detonated in a combustion chamber to launch the projectile. The masses of flat- and spherical-nosed projectiles were 270 and 230 g, respectively. The impact velocity was measured in all experiments. The cross-sections of the weld spots were inspired by a scanning electron microscope to assess the quality of welding. For several experiments, wavy interfaces were observed showing there is a good bonding. For numerical simulation of the process, Abaqus/Explicit software was used and the deformation and failure mechanisms of impact spot-welded specimens were further investigated. The Johnson–Cook thermoplasticity model along with its failure model was utilized to predict the behavior of metallic materials. The numerical simulation results were in good agreement with those obtained from experiments in terms of the deformation mode and failure pattern. The propagation of the wave on the surface of the flyer plate was further studied. The results showed that the stress waves start from the center and propagate to the corners of the plate. To numerically evaluate the welding quality, two parameters of the shear stress at the collision point as well as the equivalent plastic strain for the flyer and target plates were obtained in the numerical simulation. The numerical results showed opposite directions of shear stress for flyer and base plates at the contact point, which can be used as proof for good bonding. Besides, the magnitudes of the equivalent plastic strain for both flyer and base plates were higher than those reported values in the open literature that confirms successful welding.

scholarly journals Energy Absorbing Properties Analysis of Layers Structure of Titanium Alloy Ti6Al4V during Dynamic Impact Loading Tests

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7209
Author(s):  
Dominik Głowacki ◽  
Wojciech Moćko ◽  
Michał Marczak ◽  
Anna Głowacka ◽  
Cezary Kraśkiewicz
Keyword(s):  
Plastic Deformation ◽  
Titanium Alloy ◽  
Impact Loading ◽  
Equivalent Plastic Strain ◽  
Stress Triaxiality ◽  
Absorbed Energy ◽  
Dynamic Impact ◽  
Titanium Alloy Ti6al4v ◽  
The Impact ◽  
Dynamic Impact Loading

This paper presents the testing methodology of specimens made of layers of titanium alloy Ti6Al4V in dynamic impact loading conditions. Tests were carried out using a drop-weight impact tower. The test methodology allowed us to record parameters as displacement or force. Based on recorded data, force and absorbed energy curves during plastic deformation and sheet perforation were created. The characteristics of the fractures were also analyzed. The impact test simulation was carried out in the ABAQUS/Explicit environment. Results for one, two, and three layers of titanium alloy were compared. The increase in force required to initialize the damage and the absorbed energy during plastic deformation can be observed with an increase in the number of layers. The increase in absorbed energy is close to linear. In the simulation process, parameters such as Huber–Mises–Hencky stress value, equivalent plastic strain, temperature increase, and stress triaxiality were analyzed.

Plastic Deformation of Electrodeposited Nanocrystalline Ni-W Alloys at High Temperatures

2007 ◽  
Vol 561-565 ◽  
pp. 1295-1298
Author(s):  
Hitoshi Yokoyama ◽  
Tohru Yamasaki ◽  
Takeyuki Kikuchi ◽  
Takeshi Fukami
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Plastic Strain ◽  
Tensile Stress ◽  
Initial Period ◽  
Shear Bands ◽  
High Strength ◽  
Tensile Test Specimen ◽  
Average Grain Size ◽  
Static Tensile

High-strength nanocrystalline Ni-W alloys containing 16.9 at. % W with average grain size of about 6 nm in diameter has been obtained by electrodeposition. At room temperature, the nominal tensile strength of the alloy was attained to about 1600 MPa, while the plastic strain before fracture was a very low value of 0.05 %. In this case, highly localized shear bands were observed near the fractured surface of the tensile test specimen. When the samples were annealed at 300 °C under a static tensile stress of 327 MPa, the plastic strain was largely increased at the initial period of annealing and then tended to saturate, i.e., 0.54 % for 2 h, respectively. Grain size of the Ni-W alloys was almost saturated to 10 ~ 15 nm after annealing at 300°C for 2 h. It may be expected that the high tensile stress during grain growth might be effective to obtain the large uniform plastic deformation of nanocrystalline Ni-W alloys.

Ductile Cracking Evaluation of X80/X100 High Strength Linepipes

2004 ◽  
Author(s):  
Teruki Sadasue ◽  
Satoshi Igi ◽  
Takahiro Kubo ◽  
Nobuyuki Ishikawa ◽  
Shigeru Endo ◽  
...  
Keyword(s):  
Plastic Strain ◽  
Equivalent Plastic Strain ◽  
Base Material ◽  
Prediction Method ◽  
High Strength ◽  
Critical Conditions ◽  
Opening Displacement ◽  
Cracking Behavior ◽  
Surface Flaws ◽  
Notch Tip

The ductile cracking behavior of girth weld joints, in X80 and X100 grade linepipe, was investigated using single edge notched (SENT) specimens, notched round bar (NRB) specimens and wide plate (WP) specimens. FE analyses were carried out to evaluate critical conditions for ductile cracking at the notch tip. The effect of Y/T ratio of base material on ductile cracking for welded joints was also studied. Ductile cracking from the notch tip in WP specimens can be estimated by using the critical equivalent plastic strain, which can be obtained from SENT or NRB specimens. In addition, a simplified prediction method for ductile cracking by using effective opening displacement was proposed and its validity demonstrated by comparison to the equivalent plastic strain at the notch tip. With respect to the influence of material properties on ductile cracking behavior, deformability of joint to ductile cracking was enhanced by reduction of Y/T ratio of base material. Based on the experimental results and FE analyses, pipe design to prevent ductile cracking from surface flaws under large deformation was discussed.

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