Abstract This paper discusses four different ultrasonic guided wave standards. Three of them are China’s national standards or industry standards: GB/T 31211-2014 “Nondestructive Testing Ultrasound Guided Wave Detection”, GB/T 28704-2012“Non-destructive testing—Test method for ultrasonic guided wave testing based on magnetostrictive effects”, and DL/T 1452-2015 “Thermal Power Pipeline Ultrasound Guided Wave Detection”. The another one is ASTM E2929:“Standard Practice for Guided Wave Testing of Above Ground Steel Piping with Magnetostrictive Transfusion”. Through six aspects in this article, including testing application scope, preliminary requirements, standard specimen and comparative specimen, distant amplitude curve and time gain curve, the existing difference between China and America is obvious and diversity. It is necessary to explore the underlying reasons for the connection of Chinese code and international code in the field of Non-destructive testing. During the standardization, anyone of the standard should be actually compared on the presentation of chart, and the verification and comparison of results, and lists the similarities and differences of each part based on GB31211. This paper provides reference for China to integrate with foreign standards in the field of ultrasonic guided wave detection of pressure vessel and pipelines.

Abstract CSA Standard N285.8 requires leak-before-break and fracture protection for Zr-2.5Nb pressure tubes in operating CANDU reactors. In-service deuterium uptake causes the formation of hydrides, which can result in additional variability and reduction of fracture toughness. Pressure tube fracture toughness is assessed mainly through rising pressure tube section burst tests. Given the length of the ex-service pressure tubes required for burst testing and the requirement to increase the hydrogen content of irradiated ex-service pressure tubes, only a limited number of burst tests can be performed. Using small-scale compact tension, C(T), specimens are advantageous for obtaining a statistically significant number of fracture toughness measurements while using less ex-service pressure tube material. This work focuses on the study of C(T) geometry designs in order to obtain crack growth resistance and fracture toughness closer to those deduced from burst tests. Because C(T) specimens must be machined from pressure tubes of about 100 mm in diameter and 4 mm in wall thickness, they are out-of-plane curved. As well, they undergo significant tunnelling during crack extension. These two factors can result in a violation of the ASTM standard for fracture toughness testing. The current work examined the influence of specimen curvature and tunnelled crack front on the crack growth resistance curve, or J-R curve. Finite element (FE) models using stationary and growing cracks were used in a detailed numerical investigation. To capture crack tunnelling in the FE models, a damage mechanics approach was adopted, with the critical strain to accumulate damage being a function of crack front stress triaxiality. The J-integral numerically estimated from the domain integral approach was compared to the J-integral calculated from the analytical equations in the ASTM E-1820 standard. In most cases, the difference between the numerical and the standard estimations was less than 10%, which was considered acceptable. It was found that at higher load levels of load-line-displacement, specimen curvature influenced the J-integral results. Crack tunnelling was shown to have a small influence on the estimated J-integrals, in comparison with the straight crack fronts. A modest number of experiments were carried out on unirradiated Zr-2.5Nb pressure tube material using three designs of curved C(T) specimens. It was found that the specimens of both designs that featured a width of 34 mm had more than twice the crack extension of the specimens of the 17-mm width design. The 17-mm width specimens are used mainly to assess the small-scale fracture toughness of pressure tube material. Additionally, the applied J-integral at the maximum load was about 1.4 times higher for the larger-width C(T) specimens. These C(T) specimens also produced J-R curves with greater crack extensions, which were closer to those obtained from the pressure tube section burst tests. Artificially hydrided pressure tube material was not considered in the current work, to avoid any potential source of experimental variability; however, it should be considered in future work.

Abstract This work presents an investigation of the ductile tearing properties for a girth weld made of an ASTM A106 Gr C steel using the SMAW welding process with a low hydrogen E7018 electrode thereby resulting in a weld with high strength overmatching with respect to the base material. Testing of the pipe girth welds employed side-grooved, clamped SE(T) specimens with a weld centerline notch to determine the crack growth resistance curves based upon the unloading compliance (UC) method using a single specimen technique. Recently developed compliance functions and η -factors applicable to weld centerline notched SE(T) specimens are introduced to determine crack growth resistance data from laboratory measurements of load-displacement records. While the UC procedure resulted in measured crack extensions for the tested specimens with weld centerline notch that underestimated the 9-point average crack extension, our preliminary results demonstrate the capability of the methodology in describing crack growth resistance behavior which serves as a basis for ductile tearing assessments in ECA procedures applicable to overmatched girth welds and similar structural components.

Abstract In order to elucidate the temperature dependence of hydrogen-assisted fatigue crack growth (HAFCG), the fatigue crack growth (FCG) test was performed on low-carbon steel JIS-SM490B according to ASTM E647 using compact tension (CT) specimen under 0.7 MPa (≈ 0.1 ksi) hydrogen-gas at room temperature (RT: 298 K (≈ 77 °F)) and 423 K (≈ 302 °F) at stress intensity factor range of Δ K = 30 MPa m 1/2 (≈ 27 ksi in 1/2 ). Electron backscatter diffraction (EBSD) observation was performed on the mid-thick section of CT specimen in order to investigate change in plasticity around the crack wake in gaseous hydrogen environment and how it changes due to temperature elevation. The obtained results showed the higher temperature, the lower intense of HAFCG as reported in our previous article. Plasticity around the crack wake became less in gaseous hydrogen environment, especially tested at 298 K. The propensity of the results obtained at higher temperature (423 K) can be separated into two cases: (i) intense plasticity occurs like tested in air, (ii) crack propagates straighter accompanying less plasticity like tested in gaseous hydrogen environment at 298 K. This implies macroscopic FCG rate is determined by combination of microscopic FCG rate in the case (i) and case (ii).

Abstract Fatigue crack growth thresholds ΔK th are provided by several fitness-for-service (FFS) codes. When evaluating cracked components subjected to cyclic loading, maximum stress intensity factor K max and/or minimum stress intensity factor K min are required. However, the definitions of the thresholds ΔK th under negative stress ratio R are not clearly written, except for BS (British Standards) 7910. In addition, the ΔK th are given by constant values under negative R . Fatigue crack growth rates under negative stress ratio is recommended to use maximum stress intensity factor K max by ASTM (American Society of Testing and Materials) E 647, because of the K max being close to crack driving force. Therefore, it deems that the ΔK th under negative R seems to be K max . This paper shows that the K max converted by the ΔK th are not constant values under negative R based on the survey of experimental data. The K max decreases with decreasing the stress ratio R . Therefore, the ΔK th for the FFS codes are less conservative. As experimental data under negative stress ratio R were taken by K max – K min , the definition of the threshold ΔK th is benefit to use K max – K min , instead of K max .

Abstract The current best-estimate model describing the fracture toughness of ferritic steels is the Master Curve methodology standardized in ASTM E1921. Shortly following standardization by ASTM, efforts were undertaken to incorporate this best-estimate model into the framework of the ASME Code to reduce the conservatisms resulting from use of a reference temperature based on the nil-ductility temperature ( RT NDT ) to index the plane strain fracture initiation toughness ( K Ic ). The reference temperature RT T0 , which is based on the ASTM E1921-defined T 0 value, was introduced in ASME Code Cases N-629 (replaced by Code Case N-851) and N-631 to replace RT NDT for indexing the ASME K Ic curve. Efforts are continuing within the ASME Code to implement direct use of the Master Curve model; using the T 0 reference temperature to index an elastic-plastic, K Jc fracture toughness curve. Transitioning to a direct T 0 -based fracture toughness assessment methodology requires the availability of T 0 estimates for all materials to be assessed. The historical Charpy and NDT-based regulatory approach to characterizing toughness for reactor pressure vessel (RPV) steels results in a lack of T 0 values for a large population of the US nuclear fleet. The expense of the fracture toughness testing required to estimate a valid T 0 value makes it unlikely that T 0 will ever be widely available. Since direct implementation of best-estimate, fracture toughness models in codes and regulatory actions requires an estimate of T 0 for all materials of interest it is necessary to develop an alternative means of estimating T 0 . A project has been undertaken to develop a combined model approach to estimating T 0 from data that may include limited elastic-plastic fracture toughness K Jc , Charpy, tensile, ductile initiation toughness, arrest toughness, and/or nil-ductility temperature data. Using correlations between these properties and T 0 a methodology for combining estimates of T 0 from several sources of data was developed. T 0 estimates obtained independently from the Master Curve model, the Simple T 28J correlation model, and a more complex Charpy correlation model were combined using the Mixture Probability Density Function (PDF) method to provide a single estimate for T 0 . Using this method, the individual T 0 estimates were combined using weighting factors that accounted for sample size and individual model accuracy to optimize the accuracy and precision of the combined T 0 estimate. Combining weighted estimates of T 0 from several sources of data was found to provide a more refined estimate of T 0 than could be obtained from any of the models alone.

One of the major concerns in offshore structures are the welded connections where fatigue failures are highly relevant. In many cases of offshore welded connections, the fatigue cracks initiated may grow from the weld to the base material, but also from the root of the weld. In this study, the evaluation of design S-N curves for a double-side welded connection made of S355J2 steel used in offshore applications is proposed. The characteristic fatigue curve of the double-side welded connection is obtained using statistical analyses based either in the ASTM E739 standard as well as the probabilistic fatigue model proposed by Castillo & Fernández-Canteli. This study concludes with a comparison between the experimental fatigue curves obtained and the design S-N curves proposed in design codes for offshore structures. Existing code recommendations are very conservative when comparing the design S-N curves with the proposed new characteristic S-N curves. For the joint under investigation the hot spot and nominal stress approaches yield very similar S-N results.

Alloy 800H is currently being considered as one of the near-term candidate materials for design and construction of some major high temperature components of a very high temperature reactor (VHTR). System start-ups and shut-downs as well as power transients will produce low-cycle fatigue loadings of components. The aim of this work is to study the low cycle fatigue behavior of Alloy 800H base metal and weldments at 700°C. The weldment specimens were machined from gas tungsten arc welding (GTAW) butt-welded plate such that the loading direction was oriented transverse to the welding direction. Fully reversed total-strain controlled low-cycle fatigue tests have been performed at total strain ranges of 0.6, 0.9, 1.2 and 1.5%. For all the low-cycle fatigue tests, triangular test waveforms with a constant strain rate of 10 −3 /s were applied. Low-cycle fatigue testing was conducted in accordance with ASTM Standard E606 on servo-hydraulic test machines. And also, creep-fatigue experiments were carried out at 700°C employing 0.6% total strain range and 10 −3 /s strain rate using trapezoidal waveform with tension hold time. The main focus is to characterize the low-cycle fatigue properties for Alloy 800H weldment specimens from the cyclic deformation behavior and fatigue fracture behavior. The cyclic deformation behavior was influenced by total strain range and material property. The fatigue life was decreased with increasing the total strain range for both base metal and weldment. However, the lives of weldment specimens have a longer life than that of base metal at lower total strain ranges. It was also observed that creep effects play a significant role in fatigue life reduction.

Crack-tip opening displacement (CTOD) is an important fracture mechanics parameter. Due to different definitions, existing CTOD test methods may determine different CTOD toughness for stationary and growing cracks even for a standard specimen, such as single edge notched bend (SENB) specimen. In the USA, ASTM 1820 uses the J-integral conversion method to determine CTOD, whereas in the UK, BS 7448 adopts the plastic hinge model to determine CTOD. In contrast, ISO 12135 uses the plastic hinge model to determine the initiation CTOD, but the J-conversion method to determine a CTOD-R curve. Thus, those standards may determine different CTOD values for the same material, leading to a long-time dispute. Recently, a double clip gage (DCG) method was used in the oil and gas industry to measure CTOD. As such, there are three typical CTOD test methods: plastic hinge model, J-conversion method, and DCG method. To better understand those CTOD test methods for SENB specimens, the present paper first gives a brief review of CTOD standard test methods. This includes the CTOD definitions, plastic hinge model, J-conversion method, modified plastic hinge model, and DCG method, BS 7448, ASTM E1820, and ISO 12135. Those CTOD test methods are then evaluated using available test data for various ductile steels in literature. The experimental results of CTOD at fracture initiation and crack tearing are compared, and the differences are discussed.

Joint design, preheating, post-weld-heat treatment and operator ability are key factors for the occurrence of critical residual stresses in the welds. In particular, they may affect creep life results of the analysis: to evaluate this, their characterization requires modeling welding process, such as that carried out in the present work for ASTM A 335-Grade P22 weld. It is a weld of the two analyzed in previous work on the high-temperature-section (superheater/reheater) lower headers of the bottom-supported heat-recovery steam generator (HRSG). Present study includes modeling the only weld-lay, gas tungsten arc, manual, for the finned-tube angle joint to the cylinder. It is the same as the first of the three weld-lays for the other previously analyzed, end-plug circumferential “V”-groove butt joint. The material considered for base metal is 2¼Cr 1Mo forged, normalized, tempered with creep strain rates higher than the weld’s as it appeared from analysis of previous work. Presently, the study first compares max tangential stress evaluated by thermal analysis on the circumferential weld with the average applied normally on the joint, sustained case. Roughly, the latter one has nearly same importance as axial membrane stress on the cylinder wall for the end-plug butt joint, pressure case; it is smaller for the finned-tube angle joint. Then, study compares previous creep results obtained considering SRF = 0.9 for the finned-tube joint weld with those counting the residual-stress increase in stress analysis (different creep law’s coefficients). Finally, study compares creep results for the finned-tube joint weld obtained with and without residual-stresses (same creep power-law). The objective is to comprehend residual-stress influence over creep-redistribution and creep relaxation.

ASME B31.3 Appendix L provides the pressure and temperature ratings of forged aluminum flanges. The flanges are from NPS 1/2 to NPS 24 in three rating Classes 150, 300 and 600 with two grades of aluminum alloys: ASTM B247 3003-H112 and 6061-T6. However, B31.3 does not provide any technical information on the basis of the pressure and temperature ratings. A review of the historical development of ASME B16.5 indicated that the aluminum flanges had the same technical basis for pressure and temperature ratings as the ferrous alloy flanges in ASME B16.5. The 1960 Addenda of the 1957 Edition B16.5 included both aluminum flanges and ferrous alloy flanges. A new Code Case 2905 has been recently approved to allow B31.3 Appendix L aluminum flanges in fabricating Section VIII Division 1 pressure vessels as B16.5 flanges on the basis that both flange specifications have the same safety margin. In this paper, the technical basis of the pressure and temperature rating of aluminum flanges is revisited. Based on the same principle, the pressure ratings are extended to Class 900 and Class 1500 for the two aluminum alloys using the same analysis. Since ASTM B247 5083-H112 is another common grade of aluminum forging alloy, the pressure and temperature ratings are proposed for 5083-H112.

Mini-CT specimens are becoming a highly popular geometry for use in reactor pressure vessel (RPV) community for direct measurement of fracture toughness in the transition region using the Master Curve methodology. In the present study, Mini-CT specimens were machined from previously tested Charpy specimens of the Midland low upper-shelf Linde 80 weld in both, unirradiated and irradiated conditions. The irradiated specimens have been characterized as part of a joint ORNL-EPRI-CRIEPI collaborative program. The Linde 80 weld was selected because it has been extensively characterized in the irradiated condition by conventional specimens, and because of the need to validate application of Mini-CT specimens for low upper-shelf materials — a more likely case for some irradiated materials of older generation RPVs. It is shown that the fracture toughness reference temperatures, T o , derived from these Mini-CT specimens are in good agreement with T o values previously recorded for this material in the unirradiated and irradiated conditions. However, this study indicates that in real practice it is highly advisable to use a much larger number of specimens than the minimum number prescribed in ASTM E1921.

An irradiated low-upper-shelf Linde 80 weld metal has been tested by four laboratories as part of an inter-laboratory assessment of use of the miniature compact tension [mini-C(T)] test specimen for Master Curve fracture toughness evaluation following ASTM E1921. The preliminary results from each of the laboratories have been compiled and evaluated together to assess the validity and use of the mini-C(T) specimen for an irradiated reactor pressure vessel material which can exhibit ductile crack growth at low temperatures relative to cleavage initiation fracture toughness. The preliminary results from this mini-C(T) testing can also be compared to extensive specimen test results from larger C(T) specimens of the same irradiated material. Comparisons of the results from each of the laboratories and some inter-laboratory differences in the fracture testing are assessed. The evaluations indicate reasonable agreement between the mini-C(T) and larger specimen results, but the selection of test temperature and the number of test specimens needed to obtain reliable results are more difficult when testing a low-upper-shelf toughness material.

The Charpy V-notch specimen is the most commonly used specimen geometry in reactor pressure vessel irradiation surveillance programs and there is an extensive stored inventory of irradiated broken Charpy specimens. The advantage of the mini-C(T) (4mm thick C(T)) specimen technique is that multiple specimens can be machined from each half of broken irradiated Charpy specimens. Fracture toughness specimens that can be machined from broken halves of standard Charpy specimens enable the direct measurement of fracture toughness which can be used for engineering evaluation of reactor pressure vessels. Work to validate the mini-C(T) specimens has been performed mostly on unirradiated reactor pressure vessel base and weld metals . In this study, mini-C(T) specimens were tested providing fracture toughness characterization of an irradiated low upper-shelf Linde 80 weld (WF-70). This weld was utilized in the Midland beltline and has been previously well characterized at ORNL with various types and sizes of fracture toughness specimens. The mini-C(T) specimens were machined from broken previously tested Charpy V-notch size specimens which were irradiated in a material test reactor. The effect of different methods of measuring the displacement on the results is assessed. The ASTM E1921 results are compared to previous test data produced from larger fracture toughness specimens. In addition, the sensitivity of T 0 to the ASTM E1921 censoring value is discussed.

Eurofer97 is one of leading candidates of reduced activation ferritic martensitic (RAFM) steels for first wall structural materials of early demonstration fusion power plants. During fusion plant operation, high neutron irradiation damage on first wall materials can cause irradiation embrittlement and reduce the fracture toughness of RAFM steels. Therefore, it is critical to select proper testing techniques to characterize the fracture toughness of RAFM steels with high fidelity. In this manuscript, we present the feasibility study of using pre-cracked miniature multi-notch bend bar specimens (M4CVN) with a dimension of 45mm (length) × 3.3mm (width) × 1.65mm (thickness) to characterize the transition fracture toughness of Eurofer97 steel based on the ASTM E1921 Master Curve method. The testing yielded a provisional Master Curve reference temperature T oQ of −89°C of unirradiated Eurofer97 steel heat J362A in the normalized and tempered condition. The results are within the normal scatter range of Master Curve reference temperature T 0 for Eurofer97 steel, indicating suitability of applying M4CVN specimens for characterizing the transition fracture toughness of Eurofer97 steel.

A sound material constitutive equation is crucial for the residual life evaluation of pressure components operating in the creep range. In a previous work [1], the authors investigated how a secondary creep formulation encompassing both the dislocational and the diffusional range influences the assessment of damage according to API 579-1 [2] within the whole component stress range. In the present paper the work has been extended in order to include the effects of primary creep in the constitutive equation for the ASTM A335 P22 low-alloy steel used for the manufacturing of the HRSG header whose welded details were previously investigated. The creep damage was first calculated according to API 579-1 Section 10 via inelastic, time-dependent FEA and the Larson-Miller approach (LMP) with code-defined, minimum time-to-rupture data. This led to a first reckoning of the primary creep impact in terms of API 579-1 residual life for the components under evaluation. The API 579-1 time-to-rupture was then assessed with a detailed stress analysis implementing the Omega Method and its creep strain rate formulation. The obtained results were finally compared to those previously determined through the LMP procedure and the different creep correlations (secondary and primary+secondary).

Small punch test specimens are widely used for a long time as they are simple to produce and requires only a small volume of material. This fact is advantageous especially for high activity materials but also for assessment of operational damage in components materials when component integrity and strength may not be affected. In the same time, no test standard exists and several different specimen types and test procedures have been developed in different place. Thus, to unify this activity, considerable attention has been paid since 2012 to the standardization of small punch test technique within the American Society of Testing and Materials (ASTM). In 2016 a large InterLaboratory Study has been launched within the ASTM subcommittee E10.02 - Behavior and Use of Nuclear Structural Materials, involving 12 laboratories and 6 evaluated structural materials from the nuclear and non-nuclear power plant components. Paper describes the current status of ASTM standardization, results of the InterLaboratory Study, first analysis of the results with respect to some important test parameters, lessons learned and open questions remaining to be solved for the successful completion of the standardization process.

2.25Cr-1Mo-0.25V steel, which is a high strength low alloy (HSLA) steel, has been widely used for structural material of hydrogenation reactor due to its excellent combination of mechanical properties and resistance to hydrogen embrittlement (HE). However, it still suffers serious hydrogen damage during the aggressive service environment. When sufficient hydrogen concentrates in the reactor steel, the ductility and strength of the steel will be greatly decreased. Such a phenomenon of reduction of toughness is known as HE, and it can significantly weaken the safety and reliability of equipment. Therefore, the aim of this investigation is to focus on the effect of hydrogen on fracture toughness behavior of 2.25Cr-1Mo-0.25V steel. The fracture mechanics specimens in geometry of single edge notch bending were used. The immersion charging method was used to pre-charge hydrogen inside the specimens. Moreover, the fracture toughness of specimens with and without hydrogen pre-charging were measured following the ASTM E1820 standard. Finally, the fracture morphology was observed by scanning electron microscopy (SEM) to identify the HE mechanisms. The results of the present investigation showed that the pre-charged hydrogen resulted in significant reduction of fracture toughness of 2.25Cr-1Mo-0.25V steel, indicating a reduced crack growth resistance of specimens in the presence of hydrogen. Furthermore, the uncharged specimens failed in a ductile manner, whereas the fracture of pre-charged specimens is a mixed ductile and brittle fracture mode. It was believed that the hydrogen-induced decohesion (HEDE) mechanism contributed to the HE in hydrogen pre-charged specimens.

The use of miniature compact tension (mini-CT) specimens for fracture mechanics was experimentally demonstrated to allow the characterization of ferritic steels in the transition regime. In particular, the master curve transition temperature T 0 can confidently be determined according to the ASTM E1921 standard using mini-CT specimens. This means that specimen size effect is well taken into account if loss of constraint is limited by restricting the test temperature range to remain below the allowed maximum loading level. In the upper shelf ductile regime, where stable crack growth occurs, a number of challenges should be overcome to use such a geometry to derive the crack resistance curve, or J R -curve, transferrable to a structure. Indeed, despite a large scatter, the experimental data on several materials suggest a size effect that underestimates the crack resistance when reducing specimen size. The crack resistance behavior of several reactor pressure vessel materials was investigated with square-sized ligament compact tension specimens of various size ranging from 1 inch-thickness (B = 25 mm) to the smallest thickness (B = 4.2 mm) of the mini-CT. The main objective of this paper is to estimate the crack resistance behavior of RPV steels that would be obtained with a standard 1T-CT specimen by using mini-CT with the appropriate specimen size correction. After a series of scaling attempts that were not successful, based on a simple dimensional analysis, a simple analytical formulation based on specimen thickness and ligament is suggested to account for specimen size effect for the CT geometry. Reasonable agreement could generally be found on a number of RPV materials between crack resistance measured with mini-CT and standard 1T-CT specimens.

This work presents recent improvements in the micromechanical failure criterion based on the Weibull stress ( σ w ) concept for prediction of cleavage fracture in ferritic steels. The model is applied in SE(B) specimens extracted from an ASTM A533 pressure vessel steel having different levels of stress triaxiality at the crack tip. Nonlinear 3D finite element models with dimensions matching the tested specimens were built to provide the necessary crack tip stresses at the fracture process zone for calculation of the σ w -J evolution from wich the variation of characteristic toughness values ( J 0 ) between different cracked geometries can be estimated. Application of this methodology for the material used at this study is able to predict J 0 for SE(B) specimens with very shallow crack size ratio a / W = 0.05, short crack a / W = 0.2 and deep crack a / W = 0.4. The reported fracture toughness values for specimens having very shallow crack size ratio is an additional contribution of this study.