Fracture Toughness Testing of a Low Alloy Structural Steel Using Non-Standard Bend Specimens and an Exploratory Application to Determine the Reference Temperature, T0

2017 ◽  
Author(s):  
Vitor Scarabeli Barbosa ◽  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Structural Steel ◽  
Cleavage Fracture ◽  
Test Procedure ◽  
Reference Temperature ◽  
Width Ratio ◽  
Fracture Toughness Test ◽  
Fracture Toughness Testing ◽  
Loading Mode ◽  
Toughness Testing

This work addresses an experimental investigation on the cleavage fracture behavior of an ASTM A572 high strength, low alloy structural steel using standard and non-standard SE(B) specimens, including a non-standard PCVN configuration. One purpose of this study is to develop a fracture toughness test procedure applicable to bend geometries with varying specimen span over width ratio (a/W) and loaded under 3-point and 4-point flexural configuration. We provide a new set of plastic η-factors applicable to these non-standard bend geometries which serve to estimate the experimentally measured toughness values in terms of load-displacement records. Another purpose is to investigate the effects of geometry and loading mode in fracture tests using non-standard bend specimens. Fracture toughness testing conducted on various bend specimen geometries extracted from an A572 Grade 50 steel plate provides the cleavage fracture resistance data in terms of the J-integral at cleavage instability, Jc. The experimental results show a potential effect of specimen geometry and loading mode on Jc-values which can help mitigating the effects of constraint loss often observed in smaller fracture specimens. An exploratory application to determine the reference temperature, T0, derived from the Master Curve methodology also provides additional support for using non-standard bend specimens in routine fracture applications.

Fracture Toughness Testing Using Non-Standard PCVN Specimens: Experiments and Specimen Geometry Effects on T0 Reference Temperature

2018 ◽  
Author(s):  
Vitor Scarabeli Barbosa ◽  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Master Curve ◽  
High Strength ◽  
Potential Effect ◽  
Reference Temperature ◽  
Fracture Toughness Testing ◽  
Toughness Testing ◽  
Additional Support

This work addresses an experimental investigation on the cleavage fracture behavior of a high strength, low alloy structural steel using non-standard PCVN specimens. The primary purpose is to investigate the effects of increased specimen span on experimentally measured fracture toughness values and implications for the characterization of the temperature dependence of toughness based on the Master Curve methodology. Fracture toughness testing conducted on various PCVN geometries with increased specimen span extracted from an A572 Grade 50 steel plate provides the cleavage fracture resistance data in terms of the J-integral at cleavage instability, Jc. The experimental results show a potential effect of specimen span on Jc-values which can help mitigating the effects of constraint loss often observed in smaller fracture specimens. An exploratory application to determine the reference temperature, T0, derived from the Master Curve methodology also provides additional support for using non-standard bend specimens in routine fracture applications.

Standardization of SENT (or SE(T)) Fracture Toughness Measurement: Results of a Round Robin on a Draft Test Procedure

2016 ◽  
Author(s):  
Sanjay Tiku ◽  
Nick Pussegoda ◽  
Morvarid Ghovanlou ◽  
W. R. Tyson ◽  
Aaron Dinovitzer
Keyword(s):  
Fracture Toughness ◽  
Test Procedure ◽  
Potential Drop ◽  
Round Robin ◽  
Single Specimen ◽  
Test Program ◽  
Round Robin Test ◽  
Fracture Toughness Testing ◽  
Growth Measurement ◽  
Toughness Testing

Fracture toughness of steels is conventionally measured using bend specimens and provides a conservative estimate of toughness when the actual loading is in tension. There has been widespread interest in characterizing the toughness that occurs with reduced constraint to better reflect constraint conditions typical of a relatively shallow girth weld flaw. There is currently a standardized approach to measure fracture toughness in tension loaded specimens, however, it requires testing of multiple specimens to generate a resistance curve. Recent developments in fracture toughness testing and analysis of tension loaded specimens have led to publications by CANMET and Exxon Mobil Upstream Research Company toward development of a single-specimen procedure. As part of an initiative to enhance the state of the art in strain based design and assessment methods, with the intent of providing support for the standardization of appropriate weld testing methods, BMT under a Pipeline research Council International (PRCI) project has combined the two single-specimen approaches and developed a recommended practice for fracture toughness testing using single-edge-notched tension SENT (or SE(T)) samples with fixed grip loading. The procedure has been assessed by means of a round robin test program involving laboratories from around the world. Girth welds were fabricated and base metal, heat affected zone and weld center line specimens were prepared and sent to round robin participants. For the round robin program all the participants used a double clip gauge arrangement for direct CTOD measurement and electric potential drop measurement or unloading compliance method for crack growth measurement. In this paper, the results of the round robin test program including comparison of J and CTOD resistance curves will be presented and discussed.

A Micromechanics Approach for Assessing the Applicability of Precracked Charpy Specimens to Determine the T0 Reference Temperature

2013 ◽  
Author(s):  
Rafael G. Savioli ◽  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Pressure Vessel ◽  
Reference Temperature ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Toughness Testing ◽  
The Relationship ◽  
Resistance Data ◽  
Weibull Stress

This work describes an application of a micromechanics model for cleavage fracture to determine the reference temperature for pressure vessel steels from precracked Charpy (PCVN) specimens. A central objective is evaluate the effectiveness of the Weibull stress (σw) model to correct effects of constraint loss in PCVN specimens which serve to determine the indexing temperature T0 based on the Master Curve methodology. Fracture toughness testing conducted on an A285 Grade C pressure vessel steel provides the cleavage fracture resistance data needed to estimate T0. Very detailed non-linear finite element analyses for 3-D models of plane-sided SE(B) and PCVN specimens provide the evolution of near-tip stress field with increased macroscopic load (in terms of the J-integral) to define the relationship between σw and J from which the variation of fracture toughness across different crack configurations is predicted. For the tested material, the Weibull stress methodology yields estimates for the reference temperature, T0, from small fracture specimens which are in good agreement with the corresponding estimates derived from testing of much larger crack configurations.

scholarly journals Numerical Simulation of Fracture Toughness Testing by Prediction Model of Cleavage Fracture Toughness

2013 ◽  
Vol 99 (1) ◽  
pp. 50-59 ◽  
Author(s):  
Kazuki Shibanuma ◽  
Shuji Aihara ◽  
Motoyuki Matsubara ◽  
Hiroyuki Shirahata ◽  
Tsunehisa Handa
Keyword(s):  
Numerical Simulation ◽  
Fracture Toughness ◽  
Prediction Model ◽  
Cleavage Fracture ◽  
Fracture Toughness Testing ◽  
Toughness Testing

scholarly journals Effect of PWHT on the Fracture Toughness and Burst Test Response of Grade 91 Tube Weldments

2018 ◽  
Author(s):  
J. Siefert ◽  
J. Parker ◽  
J. Foulds
Keyword(s):  
Fracture Toughness ◽  
Charpy Impact ◽  
Fracture Toughness Test ◽  
Charpy Test ◽  
Fracture Toughness Testing ◽  
Post Test ◽  
Toughness Testing ◽  
Material Fracture ◽  
Grade 91 ◽  
Static Conditions

Requirements for post-weld heat treatment (PWHT) of steels for pressure boundary component applications have been defined in terms of exceeding a minimum Charpy impact energy in an attempt to overcome the risk of brittle cracking. This approach can be excessively conservative since it does not properly assess resistance to cracking under the relatively static conditions encountered in pressure service. It is well established that under these conditions, cracking resistance, brittle or ductile, is more properly characterized using fracture toughness (KIc/JIc) type tests. The current paper describes room temperature fracture testing conducted via Charpy testing, fracture toughness testing, and tube (burst) pressurization of Grade 91 weldments after different PWHT conditions. The results obtained highlight (a) the excessive conservatism associated with use of Charpy data for assessing burst, (b) the value of fracture toughness testing to measure the sensitivity of fracture resistance to changes in PWHT (not seen in the Charpy data), and (c) the response of tube weldments with known flaws to pressurization. The observed burst pressure results are consistent with predictions made by analysis using the fracture toughness test results. Detailed analysis, including information from post-test examination of tube weldments and a fracture mechanics-based interpretation of test data for component flaw tolerance, provide a quantitative basis for specifying repair procedures and quality assurance methods for such welds. The findings illustrate the need to utilize long-established material fracture toughness testing methods and related properties to establish rules for construction and for post-construction repair. This is particularly true for the creep strength enhanced ferritic (CSEF) steels where the elevated temperature behavior may be compromised by potentially over-tempering weldments to meet requirements based simply on the results from inexpensive but inappropriate tests such as the Charpy test.

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