bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fracture Toughness Variation With Flaw Depth in Various Specimen Geometries and Role of Constraint in Material Fracture Resistance
Authors: Hioe Y. , Kalyanam S. , Wilkowski G. , Pothana S. , Martin J. 
Published: October 2017

A series of pipe tests with circumferential surface cracks has been conducted along with fracture toughness tests using single-edge notch tension (SENT) specimens having similar crack depths and crack orientations as the surface-cracked pipes. This paper presents observation of measured fracture toughness variation due to the crack depth and discusses the effect of constraint on the material resistance to fracture.
Crack-tip-opening displacement (CTOD) measurements were obtained with the use of a dual clip-gauge mounted on both the SENT specimens and center of the surface-cracks in the pipes. CTOD was obtained at both the crack initiation and during the crack growth through the ligament. CTOD is a direct measure of the material toughness in the pipe and SENT tests. CTOD at crack initiation and during crack growth can also be related to the material J-Resistance (J-R) curve. Commonly, the material resistance is assumed to be the same for all circumferential surface-crack geometries in a surface-cracked pipe fracture mechanics analyses. However, based on experimental observations on a series of recently conducted surface-cracked pipe tests, the CTOD at the center of the surface crack at the start of ductile tearing and maximum moment changed with the depth of the surface crack. This is believed to be a constraint effect on plasticity in the ligament which depends on crack depth. The CTOD values at crack initiation were decreasing linearly with crack depth. This linear decrease in CTOD trend with flaw depth was also observed in SENT tests.
More importantly, the decrease in CTOD with surface crack depth was significant enough that the failure mode changed from being limit-load to elastic-plastic fracture even in relatively small-diameter TP304 stainless steel pipe tests. This toughness drop explains why the Net-Section-Collapse (limit-load) analysis overpredicted the maximum moment for some crack geometries, and why the deeper surface cracks tore through the pipe thickness at moments below that predicted by the NSC analysis for a through-wall crack of the same circumferential length. An “Apparent NSC Analysis” was developed in a companion paper to account for the changing toughness with crack depth [1].
Finally, this same trend in decreasing toughness with flaw depth is apparent in surface-cracked flat plates [2] and axial surface flaws in pipes [3]. The leak-before-break behavior for axial surface cracks is also not explained by numerical calculations of the crack-driving force when assuming the toughness is constant for all surface cracks and the through-wall cracks, but the change in toughness with surface flaw depth explains this behavior. Previously, axial flaw empirical limit-load solution was developed by Maxey and Kiefner [4], and is consistent with the observations from this paper.
Pressurized Creep-Fatigue Testing of Alloy 617 Using Simplified Model Test Method
Authors: Wang Yanli , Jetter Robert I. , Sham T.-L. 
Published: October 2017

The Simplified Model Test (SMT) is an alternative approach to determine cyclic life at elevated temperature and avoids parsing the damage into creep and fatigue components. The Elastic-Perfectly Plastic (EPP) combined integrated creep-fatigue damage evaluation approach incorporates the SMT data based approach for creep-fatigue damage evaluation into the EPP methodology to avoid the separate evaluation of creep and fatigue damage and to eliminate the requirement for stress classification as in current methods; thus greatly simplifying evaluation of elevated temperature cyclic service. The conceptual basis of the SMT approach is that if the effects of plasticity, creep and strain redistribution in the SMT specimen result in a stress-strain hysteresis loop that envelopes the hysteresis loop at the peak strain location in the component, then the SMT results can be used to assess the cyclic damage in the component.
The original SMT concept (Jetter, 1998) considered that the effects of sustained primary stress loading could be safely neglected because the allowable local stress and strain levels were much higher than the allowable sustained primary stress levels. This key assumption requires experimental verification. The influence of the internal pressure on SMT creep-fatigue life is demonstrated and the effect of primary load on the SMT design approach is discussed.
Acceptable Levels of Corrosion for Pressure Boundary Bolted Joints
Authors: Brown Warren , Long Stewart 
Published: October 2017

This paper outlines recent work in the field of pressure boundary bolted joint integrity and the effect of corrosion on bolted joint components. It summarizes recent analysis and testing which determined the risk to joint integrity or catastrophic failure associated with corrosion of the joint components; bolts, nuts and flanges.
The paper details, at a high level, the work performed and outlines the limits to corrosion that can be applied in the field for each component as an inspection limit to trigger planned replacement or emergency shut down.
Development of Fit-for-Purpose Austenitic Stainless Steels With High Polythionic Acid Stress Corrosion Resistance
Authors: Osuki Takahiro , Seto Masahiro , Okada Hirokazu , Sagara Masayuki , Matsumoto Satoshi , Ono Toshihide 
Published: October 2017

In the process units with Polythionic Acid Stress Corrosion Cracking (PTA-SCC) such as hydrotreater or hydrocracker, the neutralization treatment like soda ash washing and/or PWHT, Post Weld Heat Treatment, are conducted for stabilized austenitic stainless steels of TP321H or TP347H to mitigate the potential of PTA-SCC. 347AP, the proprietary version of Type 347LN, is remarkable for the possibility to save the fabrication and turnaround cost by the elimination of the neutralization treatment and/or PWHT and its reliability to PTA-SCC resistance without PWHT and neutralization was proven by the long-term service experience. However it has not been investigated the difference between 347AP and TP347H for the Stress Relaxation (SR) cracking resistance of welded joint required for the long term operation at elevated temperature.
On the other hand, in atmospheric distillation units and vacuum distillation units using the crude containing high Total Acid Number (TAN), the resistances to both Naphthenic Acid Corrosion (NAC) and PTA-SCC are required by elevating the design temperature. Therefore, Fit-for-purpose austenitic stainless steels with high PTA-SCC resistance without stabilization treatment are required for the complicated environment with the variation of temperature, pressure and fluid in petroleum refinery process using the crude containing high S content.
In this study, SR cracking susceptibility of 347AP is investigated and it is found that 347AP has lower SR cracking susceptibility than TP347H without stabilization treatment.
Next, in order to improve NAC resistance compared with 347AP, the effect of Mo, Cu and W contents to NAC are investigated based on 347AP, and it is clarified that the increase of Mo content greater than 3% is the most effective to improve NAC resistance. Moreover, the conventional welding filler with the similar NAC and PTA-SCC resistances to base metal is investigated, and it is reported that ER NiCrCoMo-1 filler was recommended for the welding fabrication of Fit-for-purpose austenitic stainless steels with high PTA-SCC resistance.
Weldability Evaluation of P87 and 230W Filler Metals in Alloy 230 to Grade P91 Steel Dissimilar Metal Weld
Authors: Sarich Conner , Alexandrov Boian , Benatar Avraham , Penso Jorge , Kovacich Jerry 
Published: October 2017

The objective of this study was to perform comparative weldability evaluation of weld filler metals for an Alloy 230 / P91 steel dissimilar metal weld (DMW) that will be used in once through steam generator (OTSG) on an offshore oil platform. The weldability characteristics of filler metals EPRI P87 and Haynes 230W were evaluated using the cast pin tear test (CPTT) and a stress relaxation cracking (SRC) test in combination with metallurgical characterization using light optical and scanning electron microscopy.
Solidification cracking susceptibility rankings generated with the CPTT showed that undiluted P87 filler metal had better resistance to solidification cracking than undiluted Alloy 230W. The SRC testing preformed in the Gleeble 3800™ thermo-mechanical simulator showed that none of the tested welds failed in stress relaxation cracking mode during simulated service at 600°C under constant displacement and tensile load at 90% of the high temperature yield strength. During the SRC testing, filler metal 230W exhibited some level of stress relaxation, while no evidence of stress relaxation was found in filler metal P87.
Technical Basis for the Exemptions to Mandatory Post Weld Heat Treatment (PWHT) of SA-738 Grade B for Sec. III Div. 1 Subsection NE Application
Authors: Hayashi Takahiro , Kim Charles C. , Kumagai Kohki , Goto Mitsuhiro , Otake Shiro 
Published: October 2017

With the current practice in steel making and welding process control, thick and large structural components fabricated from the widely used steel materials such as SA-738 Grade B have good material properties sufficient enough to meet the increasing demand of avoiding a large amount of Post Weld Heat Treatment (PWHT) applications at both shop and site. The original rule in the ASME Boiler and Pressure Vessel Code (the Code), however, allows the exemption to mandatory PWHT for SA-738 Grade B by limiting the applicable material thickness equal to or less than 1 3/4 in. (44 mm) for Section III, Division 1, Subsection NE application.
A Code Case was proposed with the purpose to increase the maximum thickness for the exemption of mandatory PWHT from 1 3/4 in. (44 mm) in the original rule to 2 3/8 in. (60 mm). In order to demonstrate the applicability of the PWHT exemption for material with increased thickness, material tests have been performed mainly for the test data required in the ASME Sec. III Div. 1 Subsection NE for three different heats of the plates. The tests performed also include additional data to those required by the Code, such as fracture toughness (KJc) test, microstructural observation, hardness test and oblique Y-groove test for SMAW process.
All the tests results for the base materials and weld joints have shown sufficient rationale to increase the exemption thickness to mandatory PWHT to 2 3/8 in. (60 mm).
Introduction of Gasket Testing Protocols in the New RCC-M® F7000 Revision Proposal
Authors: Lejeune Hubert , Boulben Cédric 
Published: October 2017

AFCEN, publisher of the French Nuclear code RCC-M® [1] (Design and Construction Rules for Mechanical Components of PWR Nuclear Islands) has launched an action for the revision of the Annex ZV and F7000 respectively concerning the design and installation of the Bolted Flange connections (BFC). This paper focuses on the gasket testing procedures defined in the proposed project for revision of F7000.
First, the general strategy of gasket testing protocols detailed in the F7000 revision project is introduced. Then the new specific gasket characterization procedures for the determination of the relevant mechanical and sealing parameters required in the calculation following the new proposed RCC-M® Annex ZV are detailed. A focus is done on the introduction of a systematic analysis procedure to determine the required force to reach the Metal-to-Metal Contact (MMC) between the compression flanges (for grooved gaskets) or between the compression flanges and the gasket limiter ring. The results of these specific test protocols on a selected set of gasket types are also presented. Finally the test protocols defined for gasket production acceptance are shortly introduced.
Study on the Rocking Vibration Induced in Three-Dimensional Seismic Isolation System
Authors: Tomita Noriaki , Fujita Satoshi 
Published: October 2017

Many earthquakes have occurred in Japan, and Japanese design seismic wave for several plants have became more severe after strong earthquakes. Especially, since vertical seismic conditions have became more severe, it is difficult to ensure the safety margin of the seismic evaluations in industrial facilities. As a way to ensure the margin of seismic evaluations, it is effective to adopt the vertical seismic isolation system. When the vertical frequency with the vertical isolation system becomes low frequency range, the rocking vibration will occur.
By using the seismic isolation system of approximately 3 [Hz] in vertical frequency, the response in vertical direction is reduced without large rocking vibration.
However, variations of a specification in seismic isolation system may occur in actual isolation device. Therefore, in this paper, the vibration characteristic including the rocking vibration is discussed, and also an analysis method is evaluated in consideration of the variation of vertical stiffness. Then, using the proposed analytical method, the tendencies of the vertical frequency variation and the rocking vibration response are confirmed. The rocking vibration occurs because of the deviation between the center of gravity and center of stiffness. Therefore, it is necessary to control the decentering between the center of gravity and rigidity. However, assuming the number of actual seismic isolation devices applying the structure, eccentricity ratio is expected to be approximately under 0.05. Therefore, the effect of eccentricity ratio on the rocking vibration is considered to be small.
Technical Basis for Characterization of Multiple Closely Separated Flaws Located in Different Planes
Authors: Blasset Sébastien , Nicak Tomas , Keim Elisabeth , Tiete Ralf , Obermeier Florian 
Published: October 2017

Non-destructive inspection records have to be characterized before evaluation of acceptance if they are evaluated as material or fabrication flaws. When multiple flaws are detected by volumetric examination, the question of interacting flaws arises if they are close to each other: can the conventional approach based on individual flaw be applied?
Alternative flaw characterization requirements may be applied in lieu of using current codes by considering recent fracture mechanics research. In order to relax the conservatism of current interaction criteria, specific work was performed to describe interaction rules for flaws located in different planes. The proximity criteria are valid for linear elastic or limited elastic plastic material behavior : this is generally the case in large components.
This paper presents the technical basis including validation of the proximity criteria based on a specific component with several flaws and considering 3D numerical modeling using elastic-plastic material behavior in order to check if the plastic material behavior affects the selected proximity criteria. The component is submitted to uniform (pressure) and non-uniform loading (like thermal shock).
Development of a Novel Test Method to Characterize Material Properties in Corrosive Environments for Subsea HPHT Design
Authors: Thodla Ramgopal , Holtam Colum , Saraswat Rajil 
Published: October 2017

High pressure high temperature (HPHT) design is a significant new challenge facing the subsea sector, particularly in the Gulf of Mexico. API 17TR8 provides HPHT Design Guidelines, specifically for subsea applications. Fatigue endurance (i.e. S-N) and fracture mechanics design are both permitted, depending on the criticality of the component. Both design approaches require material properties generated in corrosive environments, such as seawater with cathodic protection and/or sour production fluids. In particular, it is necessary to understand sensitivity to cyclic loading frequency (for both design approaches), crack growth rates (for fracture mechanics approach) as well as fracture toughness performance.
For many subsea components, the primary source of fatigue loading is associated with the start-up and subsequent shutdown operation of the well, with long hold periods in-between, during which static crack growth could occur. These are the two damage modes of most interest when performing a fracture mechanics based analysis.
This paper presents the preliminary results of a novel single specimen test method that was developed to provide fatigue crack growth rate and fracture toughness data in corrosive environments, in a timeframe that is compatible with subsea HPHT development projects. Test data generated on alloy 625+ in seawater with cathodic protection is presented along with a description of how the test method was developed. A crack tip strain rate based formulation was applied to the data to rationalize the effect of frequency, stress intensity factor range (ΔK) and maximum stress intensity factor (Kmax).
A Comparison Study of Piping Loads Effect on Support/Foundation for Elastic and Rigid Vertical Vessels
Authors: Diaz-Barrie May , Szeto Edward , Stefanovic Radoslav , Chahal Ranbir 
Published: October 2017

Modern petrochemical and chemical facilities consist of a significant number of pressure vessels. Adequate design of pressure vessels and their foundations have a significant impact on the safety and economics of such facilities. The design of pressure envelope components is well developed and specified in pressure vessel codes. A more less developed but significant aspect of the design of pressure vessels is the design of the vessel support and foundation. To adequately design the vessel support/foundation, engineers shall consider all the applicable loads on the vessel from attached piping and determine whether these loads could potentially entirely translate to the vessel base support/foundation. While methodology to determine these piping loads is well developed in literature and codes, there is a lack of guidance on how to determine the effect of these piping loads on the base support/foundation loading.
This paper is a continuation of the paper presented at the PVP2016 conference (63694 “Effects of Piping Loads on Vessel Supports and foundation” [1]), where the effect of piping loads on a vessel support/foundation was discussed. The paper demonstrated that when flexibility was introduced into a simple piping system, the loads transferred to the foundation/supports were reduced. This paper expands the study by evaluating piping loads from a more complex piping system attached to a tall vessel. To observe the differences, two different vessel heights and three different shell thicknesses are evaluated. The effect of piping loads (loading at the base) is calculated when the vessel and the nozzles are considered rigid and when flexibilities are introduced into the system. The more flexibility is introduced into the system, the more reduction in base loads is observed.
Effect of Hold Periods on the Corrosion Fatigue Crack Growth Rates of Austenitic Stainless Steels in LWR Coolant Environments
Authors: Platts Norman , Tice David R. , Panteli Alexandra , Cruchley Sam 
Published: October 2017

Laboratory tests on austenitic stainless steel in simulated light water reactor (LWR) coolant environments have been shown to give rise to significant environmental enhancements of fatigue crack growth, especially at low cycling frequencies. The impact of LWR environments on fatigue crack growth has recently been codified in ASME code Case N-809 in terms of parameters such as rise time, stress intensity factor and load ratio. However, plant performance suggests that the application of these predicted environmental effects using current assessment procedures may be unduly pessimistic. This has led to significant number of studies of waveform shape (specifically hold periods) on the corrosion fatigue crack propagation in austenitic stainless steels in LWR environments. The main emphasis of this work addresses the ability of hold periods to cause retardation of environmental crack growth rates.
There has been substantial variability in results of these studies with some authors reporting significant retardation whilst others have failed to observe retardation, or even reported additional environmental enhancement of crack growth rates for nominally similar loading waveforms. Although some of the variability may be accounted for in terms of material composition, there remains a considerable uncertainty both on the impact of holds, especially at different positions in the waveform, and the manner in which hold periods should be taken into account in plant assessments (e.g. in assessment procedures such as N-809). The current paper provides a critical review of published data on the effect of hold periods on corrosion fatigue in LWR environments as well as presenting new targeted data generation and analysis in order to rationalise the reported observations.
A Comparative Study of the Thermal-Mechanical Behavior and Fatigue Life Predictions of Different Coke Drum Support Skirt Designs
Authors: Prueter Phillip E. , Bifano Michael F. P. , Kummari Seetha Ramudu , Hantz Benjamin F. 
Published: October 2017

It is well known that coke drums are subjected to severe operating conditions that can lead to progressive plastic strain accumulation and related fatigue damage and cracking. The difficulties of performing an insightful, useful coke drum analysis are numerous. There are a variety of uncertainties and randomness in temperature and stress during the heating and quench portions of the cycle that limits the value of conventional analysis for remaining life prediction. Further complicating the issue, the progression of damage in coke drums often involves gross plasticity, permanent dilation, and variable bulging in the pressure boundary. Since the accumulation of damage in the drum is a history (or path) dependent process, a snapshot of strain or even distortion data has limited value in quantifying damage or remaining life. Additionally, ASME Code elastic-based fatigue methods, with plasticity correction factors, that have been used for coke drum assessments in the past are technically invalid when ratcheting (incremental plastic strain accumulation) is occurring. More modern fatigue methods and damage models may be required to address the permanent irreversible damage and material degradation that is produced during cycling.
To date, there are no standard methodologies developed in the refining industry for coke drum life prediction, as is evidenced by the first edition of API Technical Report 934-G [1] (published in April 2016) as well as the limited analytical work typically performed to validate coke drums during the design phase. Simplified approaches have generally been used to attempt to define trends rather than developing more fundamental analytical insight into structural response. API 934-G [1] generally attributes cracking in the bottom cones and skirts of coke drums to cyclic thermal stresses introduced during the fill and water quench portions of the operating cycle, but indicates that weld misalignment can also be a contributor to crack initiation and propagation. In this study, the thermal-mechanical behavior of multiple coke drum skirt designs, including forged, welded, and sliding configurations is investigated using elastic and elastic-plastic finite element analysis (FEA), and corresponding fatigue life predictions are discussed for each type of design. Additionally, the effect of skirt slots is quantified. Finally, a cyclic plasticity material model is employed to establish shake-down, and a modern strain-based fatigue method is implemented, including a critical-plane approach as documented in Part 14 of API 579-1/ASME FFS-1, Fitness-For-Service, (API 579) [2], Welding Research Council (WRC) Bulletin 550 [3], and Reference [4]. These results are compared to more conventional base metal and welded fatigue predictions.