scholarly journals Correlation between steel initiation toughness and arrest toughness determined from small-scale mechanical testing

2019 ◽  
Vol 17 ◽  
pp. 472-478
Author(s):  
Jessica Taylor ◽  
Ali Mehmanparast ◽  
Rob Kulka ◽  
Philippa Moore
Keyword(s):  
Mechanical Testing ◽  
Small Scale ◽  
Initiation Toughness ◽  
Arrest Toughness

Correlation Between Steel Microstructural Characteristics and the Initiation and Arrest Toughness Determined From Small-Scale Mechanical Testing

2019 ◽  
Author(s):  
Jessica Taylor ◽  
Philippa Moore ◽  
Ali Mehmanparast ◽  
Rob Kulka
Keyword(s):  
Fracture Toughness ◽  
Mechanical Test ◽  
Pipeline Steel ◽  
Crack Arrest ◽  
Carbon Steels ◽  
Small Scale ◽  
Initiation Toughness ◽  
Microstructural Characteristics ◽  
Average Grain Size ◽  
Arrest Toughness

Abstract Modern high Charpy toughness steels can nonetheless show low crack arrest toughness[1]. In this paper, the relationship between initiation and arrest toughness is investigated in five different carbon steels, including S355 structural steels, X65 pipeline steel, and high strength reactor pressure vessel, RPV, steels. The results from small-scale mechanical tests, including instrumented Charpy, drop weight Pellini, fracture toughness, and tensile testing (including STRA in the through-thickness direction) were used to determine the behaviour of the different steels in terms of initiation fracture toughness and crack arrest toughness parameters. There was no correlation between the upper shelf initiation toughness and the arrest toughness when the results from the five steels were collated. The mechanical test results were then correlated to the steels’ microstructural characteristics, including parent metal microstructure, average grain size and grain aspect ratio to identify the relative roles of microstructure and texture in the fracture initiation and arrest performance of carbon steels.

Full-Scale Reeling Tests of HFI Welded Line Pipe for Offshore Reel-Laying Installation

2014 ◽  
Author(s):  
Karl Christoph Meiwes ◽  
Susanne Höhler ◽  
Marion Erdelen-Peppler ◽  
Holger Brauer
Keyword(s):  
Mechanical Testing ◽  
Mechanical Test ◽  
Strength Properties ◽  
Full Scale ◽  
Bending Test ◽  
Small Scale ◽  
Pipe Material ◽  
Deformation Capacity ◽  
Line Pipe ◽  
Tension And Compression

During reel-laying repeated plastic strains are introduced into a pipeline which may affect strength properties and deformation capacity of the line pipe material. Conventionally the effect on the material is simulated by small-scale reeling simulation tests. For these, coupons are extracted from pipes that are loaded in tension and compression and thermally aged, if required. Afterwards, specimens for mechanical testing are machined from these coupons and tested according to the corresponding standards. Today customers often demand additional full-scale reeling simulation tests to assure that the structural pipe behavior meets the strain demands as well. Realistic deformations have to be introduced into a full-size pipe, followed by aging, sampling and mechanical testing comparable to small-scale reeling. In this report the fitness for use of a four-point-bending test rig for full-scale reeling simulation tests is demonstrated. Two high-frequency-induction (HFI) welded pipes of grade X65M (OD = 323.9 mm, WT = 15.9 mm) from Salzgitter Mannesmann Line Pipe GmbH (MLP) are bent with alternate loading. To investigate the influences of thermal aging from polymer-coating process one test pipe had been heat treated beforehand, in the same manner as if being PE-coated. After the tests mechanical test samples were machined out of the plastically strained pipes. A comparison of results from mechanical testing of material exposed to small- and full-scale reeling simulation is given. The results allow an evaluation of the pipe behavior as regards reeling ability and plastic deformation capacity.

Simplified Evaluation of Brittle Crack Arrest Toughness in Heavy-thick Plate by Combined Small-scale Tests

2017 ◽  
Vol 27 (2) ◽  
pp. 210-215 ◽  
Author(s):  
Teppei Okawa ◽  
Hiroyuki Shirahata ◽  
Kiyotaka Nakashima ◽  
Kazuhisa Yanagita ◽  
Takehiro Inoue
Keyword(s):  
Thick Plate ◽  
Crack Arrest ◽  
Small Scale ◽  
Brittle Crack ◽  
Arrest Toughness

Crack Arrest Toughness of a Heat-Affected Zone Containing Local Brittle Zones

1996 ◽  
Vol 118 (4) ◽  
pp. 292-299 ◽  
Author(s):  
L. Malik ◽  
L. N. Pussegoda ◽  
B. A. Graville ◽  
W. R. Tyson
Keyword(s):  
Crack Initiation ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Weld Zone ◽  
Crack Arrest ◽  
Attractive Alternative ◽  
Initiation Toughness ◽  
Fusion Boundary ◽  
Arrest Toughness ◽  
Fast Fracture

The awareness of the presence of local brittle zones (LBZs) in the heat-affected zone (HAZ) of welds has led to the requirements for minimum initiation (CTOD) toughness for the HAZ for critical applications (API RP 2Z, CSA S473). Such an approach, however, is expensive to implement and limits the number of potential steel suppliers. A fracture control philosophy that is proposed to be an attractive alternative for heat-affected zones containing LBZs is the prevention of crack propagation rather than of crack initiation. Such an approach would be viable if it could be demonstrated that cracks initiated in the LBZs will be arrested without causing catastrophic failure, notwithstanding the low initiation (CTOD) toughness resulting from the presence of LBZs. Unstable propagation of a crack initiating from an LBZ requires the rupture of tougher microstructural regions surrounding the LBZ in HAZ, and therefore the CTOD value reflecting the presence of LBZ is unlikely to provide a true indication of the potential for fast fracture along the heat-affected zone. Base metal specifications (CSA S473) usually ensure that small unstable cracks propagating from the weld zone into the base metal would be arrested. Past work has also shown that unstable crack initiation resulting from interaction of surface semi-elliptical cracks parallel to the fusion boundary with the local brittle zones can get arrested once the crack has popped through the depth of the LBZ. However, the potential for arrest when a through-thickness HAZ crack runs parallel to the fusion boundary, and thus parallel to the LBZs, has not been examined previously. To investigate the likelihood of fast fracture within the HAZ, a test program has been carried out that involved performing compact plane strain (ASTM E1221) and plane stress crack arrest tests on a heataffected zone that contained LBZs, and thus exhibited unacceptable low CTOD toughness for resistance to brittle fracture initiation. The results indicated that in contrast to the initiation toughness (CTOD toughness), the crack arrest toughness was little influenced by the presence of local brittle zones. Instead, the superior toughness of the larger proportion of finer-grain HAZ surrounding the LBZ present along the crack path has a greater influence on the crack arrest toughness. It further seems that there may be potential to estimate the HAZ crack arrest toughness from more conventional smaller-scale laboratory tests, such as conventional or precracked instrumented Charpy impact tests.

ITER baffle module small-scale mock-ups: First Wall thermo-mechanical testing results

1998 ◽  
Vol 39-40 ◽  
pp. 559-567 ◽  
Author(s):  
Y. Severi ◽  
P. Chappuis ◽  
L. Giancarli ◽  
G. Le Marois ◽  
Y. Poitevin ◽  
...  
Keyword(s):  
Mechanical Testing ◽  
Small Scale ◽  
First Wall

Prediction of Initiation Toughness Under Small Scale Yielding (SSY) and J0.2BL vs. Q Fracture Locus Using Local Approach Methodologies in 304SS

2012 ◽  
Author(s):  
A. Wasylyk ◽  
A. H. Sherry ◽  
J. K. Sharples
Keyword(s):  
Fracture Toughness ◽  
Small Scale ◽  
Initiation Toughness ◽  
Single Edge ◽  
Small Scale Yielding ◽  
Local Approach ◽  
Three Point Bending ◽  
Fracture Locus ◽  
Scale Yielding ◽  
Cracked Specimens

Structural integrity assessments of structures containing defects require valid fracture toughness properties as defined in national and international test standards. However, for some materials and component geometries, the development of valid toughness values — particularly for ductile fracture — is difficult since sufficiently large specimens cannot be machined. As a consequence, the validity of fracture toughness properties is limited by the development of plasticity ahead of the crack tip and the deviation of crack tip conditions at failure from small scale yielding. This paper described the use of local approach models, calibrated against invalid test data, to define initiation toughness in 304 stainless steel pipe material. Three fracture toughness geometries were tested, shallow cracked single edge cracked specimens tested under three point bending, deep cracked single edge cracked specimens tested under three point bending, and deep cracked single edge cracked specimen tested under tension. Initiation toughness and J-Resistance curves were defined for each specimen using the multi-specimen technique. All initiation toughness values measured were above the specimen validity limits. The fracture conditions at initiation were analysed using three local approach models: the Generalised Rice & Tracey, High Constraint Rice & Tracey and the Work of Fracture. The adequacy of local approaches to define the fracture conditions under large strains in 304 stainless steels was demonstrated. A modified boundary layer analysis combined with the local approach models was used to predict the “valid” initiation toughness under small scale yielding condition in this material by defining a J-Q fracture locus. The analytically derived fracture locus was compared to the J-Q values obtained experimentally and shown to be consistent.

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