bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Charts for an Integrated Creep-Fatigue Damage Evaluation Approach
Authors: Barua B. , Messner M. C. , Sham T.-L.
Published: November 2022

This paper discusses the development of design charts for creep-fatigue evaluation using an integrated elastic-perfectly plastic analysis (EPP) and Simplified Model Test (SMT) approach. The creep-fatigue damage evaluation approach in current ASME Section III, Division 5 rules requires separate evaluation of creep and fatigue damages and then considers the effect of creep-fatigue interaction with a creep-fatigue interaction diagram, also known as D-diagram. The EPP+SMT approach avoids the use of D-diagram by directly comparing the strain range determined from an EPP analysis with design charts, conceptually developed directly from creep-fatigue and SMT tests, to determine the creep-fatigue damage. The EPP+SMT approach provides much simpler creep-fatigue design evaluation process compared to current methods and is also expected to reduce the over-conservatism in current methods. Generating the EPP+SMT design charts requires extrapolating high strain range, short hold time test data to low strain range and long hold times, typically experienced by structural components in high temperature nuclear service. This work investigates several extrapolation approaches in the development of methodologies for constructing EPP+SMT design charts for Alloy 617 at temperatures between 800°C and 950°C. The design charts are validated using failure data from pressurized SMT tests and by comparing the EPP+SMT method with current design methods for representative high temperature nuclear reactor components.
Finite Element Analysis of Piping System Under Blast Load Due to Accidental Explosion
Authors: Dereli Ozer , Basu Sudipta , Ozbey Mehmet , Bhattacharyya Rudraprasad
Published: November 2022

This paper presents a methodology for nonlinear dynamic finite element analysis of piping system, which mainly consists of process piping, and pipe supports subjected to accidental blast loading. As opposed to an ASME B31.3 linear elastic static code check performed on Caesar II (Category 1) or a simplified single-degree-of-freedom (SDOF) approach (Category 2), a multi-degree-of-freedom (MDOF) approach is more realistic and less conservative for blast analysis of piping systems. Thus, the piping system is modeled as a multi-degree-of-freedom (MDOF) system to capture both the local and global responses. Furthermore, an in-house scripting tool was developed to automatically convert the piping stress analysis input files (in Caesar II) to blast analysis input files (in Abaqus). The scripting tool allows blast analysis of several hundreds of piping systems to be performed within a competitive project timeline. In the blast analysis model, blast load is applied as drag load on the piping system. In this study, geometric, material, and boundary condition nonlinearities are considered. The blast analysis is performed using commercial finite element software Abaqus/Explicit. The displacements and plastic strains at different locations of the piping system are evaluated and compared against a pre-established displacement limit and a plastic strain limit. Based on the analysis results, the number of additional pipe-supports which were required by linear elastic static or SDOF analysis approaches were significantly reduced along the piping systems.
Experimental Basis for the Extension of Elastic-Perfectly Plastic Strain Limits Evaluation Procedure of ASME Section III, Division 5 Code Case N-861 to Grade 91, Alloy 800H and 2.25Cr-1Mo
Authors: Wang Yanli , Hou Peijun , Sham Ting-Leung
Published: November 2022

The Elastic-Perfectly Plastic (EPP) based design method was qualified for ASME Section III, Division 5 Class A construction using Type 304 and 316 stainless steels and Alloy 617 via Code Case N-861 for Strain Limits evaluations. Because the isochronous stress-strain curves used in the EPP Strain Limits analysis were determined from standard creep testing on specimens without any prior cyclic loading history, experimental verification and analysis are required in order to extend the EPP Strain Limits analysis to the remaining three Class A materials, Grade 91, Alloy 800H and 2.25Cr-1Mo. In this study, specialized tests were designed and performed to evaluate the effects of cyclic deformation on the subsequent creep properties of these three Class A materials in the creep regime and the results are compared with standard creep tests. It is shown that reduction factors on the isochronous stress-strain curves are needed for Grade 91 to account for its cyclic softening effect. However, prior cyclic deformation has an insignificant effect on the minimum creep rates of Alloy 800H and 2.25Cr-1Mo, hence reduction factors are not required. The experimental results and analysis in this study provide the technical basis for the extension of Code Case N-861 to these three Class A materials.
Performing Under Pressure – Design Guidance for High-Pressure, High Cycle Piping System
Authors: Chae Jaehee
Published: November 2022

Plant owners are responsible for specifying piping fluid service categories and determining the applicability of ASME B31.3 Chapter IX for high-pressure piping. However, the code only defines the design for high-pressure fluid service piping, and many designers and engineers are not fully aware of the best design practices for low-stress and high-cycle applications.

Using innovative industry approaches and harmonic response analysis, dynamic stress levels of piping are calculated, and finite element analysis (FEA) used to calculate stress from the cycle range. This includes piping system design pressure at 10,200 psig with expectations of more than 1,000,000 stress cycles in a single day.

A thermal flexibility analysis of the piping system along with a fatigue analysis for the entire piping components within the system is performed in accordance with ASME BPV code Section VIII Division 3. The fatigue stress ranges of a properly designed vibrating piping system are typically well below the ASME BPV code limit.

High-pressure, unlisted piping fitting components such as reducers, tees, elbows and flanges, are also analyzed using the FEA and ASME BPV code design procedures.

This paper discusses the design process and deviations from the base code for piping design requirements as well as special techniques to consider for high-pressure and high-cycle piping.
Analysis of Mainframe Computer Structures Using Implicit and Explicit Finite Element Analysis
Authors: Notohardjono Budy , Canfield Shawn , Khambati Suraush , Ecker Richard
Published: November 2022

This paper discusses the finite element analysis (FEA) methods used to analyze the performance of a mainframe computer’s structural frame under a standard seismic loading such as that defined by Telcordia NEBS Zone 4. Specialists in the earthquake robustness area need to consider the basic mainframe structural information such as the total mass and the center of gravity in order to properly size and install tiedowns to prevent tiedown failure which can lead to hazardous tip-over events. To ensure successful operation through a seismic event, the total deflection of the top of the mainframe is a good indicator of ensuring the mainframe computer’s continuous operation.

As the mainframe computer’s total weight and the center of gravity varies depending on the specific customer configuration, this paper will examine the two extreme end cases: the lowest mass configuration with the highest location of the center of gravity and the highest mass configuration with the highest center of mass location. From a structural perspective, the higher the initial resonance frequencies, the more rigid the structure and the smaller the upper frame deflection will be. Thus, given a mainframe structure, the finite element analysis results will provide information on the weakest direction resonance frequency, which is in the narrow, side-to-side direction, along with the mainframe rack tiedown loads and maximum top frame deflection.

Given a mainframe structure’s finite element model and standard time domain seismic acceleration input at the base of the frame structure, the explicit finite element method will provide the performance of the structure namely the first resonance frequency, the maximum stresses at the rack structure, load at the tie down locations and the maximum top frame deflection. The explicit finite element analysis model can take into account the non-linear contact regions around weld areas and between adjacent sheet metal frame components as well as material non-linearities. The result of the FEA analysis of the several mainframe configurations will be compared to the results from actual seismic earthquake mainframe tests.
Evaluation of the Fracture Behavior of Cold-Worked Elbows With Prescribed Cracks
Authors: Kalyanam Sureshkumar , Pothana Sushma , Wilkowski Gery , Hioe Yunior , Orth Fabian , Brust Frederick , Gilbert Steven
Published: November 2022

Cold-working of elbows and other fittings results in higher strength of the material and has traditionally been considered to be beneficial for piping applications. Although it is known that cold-working leads to spatiotemporal variation in the grain size and the concomitant material property and fracture toughness variations they are not routinely investigated. Hence, this paper reports the findings from elbow fracture experiments conducted at 550°F and internal pressurized conditions (2,250 psi) on TP304 cold-worked elbows. The objectives for conducting the tests were to evaluate the effects of cold-working on the applicability of existing techniques such as an “Original” Net-Section-Collapse (NSC) and recently developed “Apparent NSC” equations for pipes with different inner diameter (ID) surface crack (SC) depths and lengths. This is to determine the failure moments and the plastic reduction factor (PRF) obtained to translate these to piping system evaluations. Preliminary comparisons of the experimental findings with the maximum stress predictions existing for straight pipes and elbow fracture prediction methods developed in the International Piping Integrity Research Group (IPIRG)-2 program were revisited, along with the verification of the applicability of the American Society of Mechanical Engineers (ASME) B2 stress indices and flaw acceptance criteria.
Crack Growth Modeling and Constraint Behavior Observations in Complex Crack Geometries
Authors: Kalyanam Sureshkumar , Hill Lance , Wilkowski Gery , Brust Frederick
Published: November 2022

The area of complex cracking in piping components and its effects on the fracture behavior and leak-before-beak evaluations has been highly researched. Several researchers have conducted experiments to quantify the behavior through complex cracked piping experiments starting from the 1980s and also more recently in dissimilar metal welds (DMWs). The area has also seen several contributions on the modeling aspects to characterize the crack initiation as well as the ductile crack growth behavior. In this work, the crack growth in complex-crack geometries is revisited through a novel laboratory specimen model, developed by modifying a Single-Edge Notch Tension SEN(T) specimen that is routinely used to obtain the fracture toughness values for both crack initiation as well as crack growth/tearing behavior. Details on the cell size used in the finite element analysis (FEA), and the effects on the predictability of the experimental observations are highlighted. The effects of constraint based on the relative levels of complex-cracking (aspect ratios) are discussed. While the results are precursors to the understanding of the correlations of constraints and fracture for these complex-cracked geometries, they provide guidelines for path forward towards development of methodologies to treat these when making reliable comparisons between material fracture resistance and crack driving forces that are routinely employed in fracture-based leak-before-break assessments for piping and piping components.
Fatigue-Life Prediction and Design for Uncracked and Cracked Components: Deterministic, A- and B-Basis Probabilistic, and Reliability Target Approaches
Authors: Fong Jeffrey T. , Marcal Pedro V. , Freiman Stephen W. , Heckert N. Alan , Filliben James J.
Published: November 2022

Based on a recently developed multi-scale fatigue-fracture-NDE reliability model for uncracked and cracked pipes (see Fong-Marcal-Rainsberger-Heckert-Filliben-Doctor-Finney, PVP2021-62169), we apply the same modeling technique to a comparative study of three approaches to fatigue-life prediction and design: Approach (1). Deterministic. Approach (2). Probabilistic using the A- and B-basis design allowables. Approach (3). Reliability Target using the concept of a co-reliability or an upper bound of failure probability as a tool for damage assessment and control. To illustrate the comparison of the three approaches to both uncracked and cracked components, we present numerical examples for generic components of three engineering materials at room temperatures, namely, (a) AISI 4340 steel for piping, (b) 2024-T4 aluminum for aircraft structures, and (c) BK-7 borosilicate crown glass for aircraft windows. In particular, for cracked components inspected by NDE personnel with varying probability of detection (POD) qualifications, we find both Approach (1) and Approach (2) inadequate as a guide for maintenance decision-making and compliance with the ASME Boiler and Pressure Vessel Section XI Division 2 Reliability and Integrity Management (RIM) Code. Significance and limitations of the methodology for Approach (3) based on the concepts of co-reliability and reliability target are presented and discussed. Some concluding remarks and future work are included at the end of this paper.
Case History of Hydrotreater Prefeed Heater Fire Recovery
Authors: Penso Jorge , Park Neil , Dalal Mitul , Hosack Alexandra
Published: November 2022

A prefeed heater in a hydrotreater unit experienced a fire while being prepared for shutdown during a turnaround. The prefeed hydrotreater heater was a mixed operation heater that typically operated in mixed mode with hydrogen and hydrocarbon bitumen, but at the time of the incident was operating in hydrogen only mode in order to hot hydrogen strip the hydrotreater.

The heater had been in operation since 2011 and had a design fluid temperature of 425 °C (797 °F), a tube metal temperature of 570 °C (1058 °F) and design pressure of 16,800 kPag (2437 Psig). The normal operating pressure was 15,000 kPag (2176 Psig). The radiant and convection tubes were fabricated from Type 316Nb stainless steel (UNS31640). There was a tube rupture in the radiant section that caused the fire and the subsequent failure investigation established that the temperature in the radiant section at the rupture location had reached in excess of 850 °C (1562 °F) for over a 15-minute period prior to rupturing. The following paper outlines the failure analysis and root causes which caused the incident, while detailing the recovery and construction of the heater, including the fitness-for-service methods and inspections conducted. The heater was partially rebuilt with the convection section tube material being recovered and the radiant section being rebuilt in a different metallurgy.
Developing a Test Protocol to Determine Packing Performance in a Soot Blower
Authors: Henriques Isadora R. , Meira Igor , Girão Carlos D.
Published: November 2022

Soot deposit accumulation on heat transfer tubes and surfaces in recovery boilers reduces thermal performance, compromising thus the efficiency and life of the equipment. A soot blower is employed to remove these by-products to maintain boilers within design conditions. This specialized device has a seal between its tubes to maintain fluid pressure to clean the heating pipes and inside surface. Nevertheless, sealing can be a challenge due to its large displacement amplitude, the reciprocating movement, and the sudden change of temperature and pressure. Many different solutions are available in the market that offers viable sealing methods, but there is no test method to classify them. This work proposes a soot blower test protocol to evaluate the sealing solutions available. Comparative results for the different seal types are presented.
Duplex Stainless Steel – Learning From Field Experience in Oil & Gas and Petrochemical Services
Authors: Dalal Mitul , Penso Jorge
Published: November 2022

Duplex stainless steels are a family of stainless steels. Named duplex (or austenitic-ferritic) grades because their metallurgical structure consists of two phases, austenite, and ferrite in approximately equal proportions. They are expected to provide better corrosion resistance, particularly chloride stress corrosion and chloride pitting corrosion, and higher strength than standard austenitic stainless steels such as Type 304 or 316. They are therefore used extensively in the offshore oil and gas and in the petrochemical industry in the form of piping and pressure vessels.

This paper describes some applications that ended up in failures and the importance to adhere to tight fabrications fabrication controls and consider the effect of common manufacturing and fabrication deviations in the expected material performance. The first one is a shell and tube heat exchanger. On the shell side the material choice was 2205 duplex stainless steel. The shell side fluid is fed from debutanizer which feeds from upstream high pressure and low-pressure low temperature separators. Overhead stream contains H2S, NH3, HCl. The duplex was selected for this exchanger to mitigate potential dew point NH4Cl corrosion. The shell ended up leaking in less than two years after being placed in service.

The second case is a super duplex 2507 seawater filter which failed after few weeks in service. Qualified welding procedures were not properly followed during fabrication leading to impaired corrosion resistant weldments.

The third case describes one more failure of a hydrocracker reactor effluent air cooler. Tube to tubesheet and partition plates to tubesheet welds failed after ∼ 20 years in service.
Evaluation of Localized Stresses at Spherical Pressure Vessel-to-Column Support Junction Using Closed-Form Equations
Authors: Manjrekar Vivek
Published: November 2022

Spherical pressure vessels (spheres) are widely used for storing liquids and gases at high pressures. The post plates of column-supported spheres are subjected to additional loads imposed by the supporting columns. The resulting localized stresses at column-to-post plate junction are difficult to analyze using analytical methods. Numerical techniques, such as the finite element method (FEM) are generally used to analyze the local discontinuity stresses.

In this work, a finite element parametric study is performed using a wide range of sphere geometries. The stresses at various locations around the column attachment are investigated. The influence of various loadings on the local stresses is also investigated. The internal membrane forces and bending moments obtained from the finite element model are then used to establish the dimensionless curves. A step-by-step procedure and the closed-form equations are provided to calculate membrane stresses, bending stresses and the combined stresses. A table of load factors is included to estimate the maximum vertical and horizontal loads on post plate due to wind or seismic forces. Finally, a sample problem is presented to illustrate the analysis procedure. Using this easy-to-use analysis approach, the design engineers will be able to calculate the localized stresses in sphere post plates without having to utilize the finite element method.
Computational Mechanics Based Validation of Crack Growth Approaches for Fracture Specimen Predictions
Authors: Kalyanam Sureshkumar , Hill Lance , Wilkowski Gery , Brust Frederick
Published: November 2022

The last several decades have seen growth in elastic-plastic fracture mechanics and the modeling of the behavior of structural steels employed in the nuclear, oil and gas, and other construction industries. Among these are a particular class of problems that provide challenges in modeling the physical behavior of structural steels using finite element modeling (FEM) approach that are based on microstructural damage and using parameters that depict the strain and stress states in the material region ahead of an existing crack. In this work, a recently experimented and investigated pipeline steel X80 material was modeled through two different fracture specimen geometries, namely single-edge-notch-tension, SEN(T) and compact-tension, C(T) to compare and contrast the predictions from two material damage models (microstructure and continuum based). The predictions from both these damage models that predict the ductile crack growth have been compared to the experimental findings of the crack growth (obtained using a d-c Electric Potential measurement technique), the corresponding load levels, and crack opening displacements (CODs). The points of similarity between the experimental measurements and the fracture surface observations of crack growth and the predictions from the FEM approach have been discussed. The same X80 material properties and damage model parameters were employed to predict the ductile crack growth in the two different fracture specimen geometries, SEN(T) and C(T) with a subtle change of one of the parameter values. This sheds light on the predictability of the crack initiation event and the subsequent ductile crack growth until failure using these damage models. The findings provide credence to the applicability of either model (after they are carefully tuned to arrive at optimized parameters) for piping materials while providing a framework for flaw evaluation methodologies. The investigation also opens the doors for regions where mesh regularization methods and modeling approaches along with mathematical relations can be developed to form a more efficient framework for modeling specimens with diverse constraints efficiently and develop material fracture resistance curves.
Machine Learning Models of Burst Strength for Defect-Free Pipelines
Authors: Zhu Xian-Kui , Johnson William R. , Sindelar Robert , Wiersma Bruce
Published: November 2022

Burst strength of line pipes is essential to pipeline design and integrity management. The simple Barlow equation with the ultimate tensile strength (UTS) was often used to estimate burst strength of line pipes. To consider the plastic flow effect of ductile steels, Zhu and Leis (2006, IJPVP) developed an average shear stress yield criterion and obtained the Zhu-Leis solution of burst strength for defect-free pipelines in term of UTS and strain hardening exponent, n, of materials. The Zhu-Leis solution was validated by more than 100 burst tests for various pipeline steels.

The Zhu-Leis solution, when normalized by the Barlow strength, is a function of strain hardening rate, n, only, while the experimentally measured burst strength, when normalized by the Barlow strength, is a strong function of n and a weak function of UTS and pipe diameter to thickness ratio D/t. Due to difficulty of three-parameter regressions, this paper adopts the machine learning technology to develop alternative models of burst strength based on a large database of full-scale burst tests. In comparing to the regression, the machine learning method works well for both single and multiple parameters by introducing an artificial neural network (ANN), activation functions and learning algorithm for the network to learn and make predictions.

Three ANN models were developed for predicting the burst strength of defect-free pipelines. Model 1 has one input variable and one hidden layer with three neurons; Model 2 has three input variables and one hidden layer with five neurons; and Model 3 has three input variables and two hidden layers with three neurons for the first hidden layer and two neurons for the second hidden layer. Those ANN models were then validated by the full-scale test data and evaluated through comparison with the Zhu-Leis solution and the linear regression result. On this basis, the best ANN model is recommended.
Evaluation of the API 579-1/ASME FFS-1 KPECL and KCECLL Stress Intensity Factors
Authors: Altstadt Steven
Published: November 2022

The API 579-1/ASME FFS-1 2016 Fitness-For-Service stress intensity factor solution for a plate with an embedded crack, infinite length, through-wall fourth order polynomial stress distribution (KPECL) was independently investigated in this work. Finite element models of cracked plates subjected to various applied stress fields were created and used to estimate stress intensity factors (K), which were then used to calibrate the respective influence coefficient values (Gi). The comparison of the newly calculated values to the existing values shows reasonable agreement for some values and a substantial difference for others. The new influence coefficients were also compared to values published by Le Delliou and Barthelet (2007) for the parameter combinations that exactly overlap with API 579-1/ASME FFS-1 2016. Excellent agreement was found with the new values presented herein. API 579-1/ASME FFS-1 2016 also recommends that the KPECL solution can be used for a cylinder with an embedded crack, longitudinal direction, infinite length, through-wall fourth order polynomial stress distribution (KCECLL) when the ratio of the internal radius (Ri) to wall thickness (t) is greater than or equal to five. As part of this work, influence coefficient values were also calculated for Ri/t = 5 and are included in this paper. A comparison of each KPECL value to its respective KCECLL value indicates that the recommendation is a reasonable approximation. The new influence coefficient values are recommended for fitness for service assessments that involve either the KPECL scenario or the KCECLL scenario where Ri/t ≥ 5.
Improvement of the ASME B&PV Code Resolution of Nonplanar Flaws in Pressure Retaining Components
Authors: Lacroix Valéry , Dulieu Pierre , Hasegawa Kunio , Mares Vratislav
Published: November 2022

When nonplanar flaws are detected in a component they are subjected not only to fracture mode I but to fracture modes I, II and III according to the direction of the load relatively to that of the flaws. Those fracture modes are induced by the relative displacement of crack faces as they are subjected to multi-axial loading. Consequently, the Stress Intensity Factors (SIFs) KI, KII and KIII corresponding to each of those modes should be accounted for in the flaw assessment. This is done in some Fitness-for-Service Codes that make provision to calculate an effective SIF.

In the ASME B&PV Code Section XI, a simplified approach is proposed: a nonplanar flaw is resolved into two planar flaws by projection of the flaw area into the planes normal to the maximum principal stresses. This approach allows simplifying the flaw assessment procedure as it deals only with KI SIF for which a lot of tabulated or closed-form solutions exist. However, the authors of this paper demonstrated recently that this simplified resolution of nonplanar flaws is not conservative for all types of loading and flaw inclinations. Consequently, an improvement of the resolution of nonplanar flaws must be provided in ASME B&PV Code Section XI.

In that frame, this paper carries out an exhaustive assessment of the conservatism of the ASME approach and then proposes an alternative approach to deal with nonplanar flaws allowing to overcome the non-suitability of the current ASME Code.
Empirical Correction Factor to Estimate the Plastic Collapse Bending Moment of Pipes With Circumferential Surface Flaw
Authors: Lacroix Valéry , Hasegawa Kunio , Li Yinsheng , Yamaguchi Yoshihito
Published: November 2022

The structural integrity assessment of pipes with circumferential surface flaw under the plastic collapse regime consists of net section collapse analysis. In recent years various researchers showed that this analysis, which has been developed based on classic beam theory, has certain inaccuracies. As such, assessment purely based on net-section collapse and beam theory can lead to both conservative and unconservative results.

To address those inaccuracies, in this paper the authors propose a correction factor which aims to mitigate the difference between the experimental results and ASME B&PV Code Section XI equations. This correction factor is calculated using an empirical formula developed on the basis of a large experimental database of pipe collapse bending tests containing variety of diameters, thicknesses, flaw depths and flaw lengths.

In this work, the authors took a systematic approach to identify the most influencing factors on such a correction factor and showed that by applying this correction factor to the current solution of ASME B&PV Code Section XI, the resulting solution becomes more accurate. This corrected approach also is in line with ASME B&PV Code Section XI Appendix C practice for axial flaw in pipes, where a semi-empirical correction factor has been considered as well.
Thermoelastic Analysis of Cylindrical Panels by Hyperbolic Heat Conduction
Authors: Pourasghar Aminallah , Brigham John
Published: November 2022

A three-dimensional approach is presented to analyze the thermoelastic behavior of a cylindrical panel subjected to transient heat conduction. First, the hyperbolic heat conduction equations are solved to obtain the temperature (and heat flux) in the spatial and temporal domain using the differential quadrature method (DQM) and Newton-Raphson method, respectively. The obtained temperature distribution is then applied in the three-dimensional thermoelastic equations of the cylindrical panel to obtain displacements and stresses at each time step by solving an eigenvalue problem. Numerical test cases showed that the proposed approach can estimate the temperature and deflection accurately. Although, the accuracy is dependent on the time increment and number of sampling grid points in the spatial and temporal domain of DQM.
Fatigue Damage Estimation From Pseudo-Random Load Sequence Generated for Metals and Fiber Reinforced Composites
Authors: Prakash Raghu V. , Patil Anurag Jeevan
Published: November 2022

Composite materials are widely used in many applications in view of tailor suiting of properties that include stiffness, toughness, and strength. Fatigue loading of components made of composites is inevitable. The theory to predict fatigue damage and fatigue life is well established for metals, while such a clear definition is not available for composites. The damage in composite can be due to matrix cracking, delamination, fiber fracture, matrix crazing, etc. The problem is complex when one considers pseudo-random load sequences like an aircraft spectrum.

This study evaluates the damage under a typical European Standard spectrum for Fighter Aircraft Loading STAndard for Fatigue and Fracture (FALSTAFF) as well as its programmed version. The phenomenological model proposed by Broutman and Sahu and empirical models proposed by Palmgren-Miner; Bond and Farrow; and Hashin-Rotem are used for calculating damage and fatigue life. Constant life diagrams are used for calculating the number of cycles to failure. The Range-Damage-Exceedance curve is employed to omit cycles from the FALSTAFF load sequence. It is observed that the Programmed FALSTAFF load sequence derived for metals is applicable for composites as both the full FALSTAFF spectrum and programmed version provide similar damage estimates. An increase in reference stress resulted in a decrease in fatigue life. Hashin-Rotem model is used to study sequence effect from the Programmed version of FALSTAFF. It is estimated that fatigue life under low-high load sequence is more as compared to high-low load sequence.
Study on Test and Evaluation Methods of Assembly Valve on High Pressure Hydrogen Storage Cylinder for HFCV
Authors: Gu Chunlin , Li Jun , Zhu Ming , Zhao Baodi , Li Jiepu , Li Xiang
Published: November 2022

In this paper, a comparative study is made on the test items and evaluation criteria stipulated in the relevant regulations and standards of hydrogen storage system valves and temperature-driven pressure relief devices (TPRD) for hydrogen fuel cell vehicle (HFCV). The similarities and differences are listed and analyzed. Based on the study and according to the characteristics of the assembly valve for HFCV (hereinafter referred to as the assembly valve), some suggestions on the test items, test methods and evaluation criteria settings for the assembly valve are discussed and the test strategy for assembly valve is proposed.
Piping Vibration Mitigation Comparison Using Snubbers and Struts
Authors: Saunders Kenneth L. , Onorato Michael
Published: November 2022

One of the typical characteristics of high temperature piping systems is that they are more flexible. This is due primarily to expansion stress limits which cause the piping designer to add additional elbows and to minimize axial or lateral stops. The resulting higher flexibility and lower frequency piping system is vulnerable to vibration loading which may result in excessive displacements, and hence, excessive stresses. Two options for reducing vibration displacements are adding snubbers or adding struts to the piping system. Both snubbers and struts will act as rigid components when subjected to vibration loading. The snubber has the advantage over the strut of being able to displace in all directions when the piping system is heated, thus allowing the expansion stresses to be minimized. Also, snubbers that are better suited for mitigating operational vibrations also have the advantage of being effective in all three orthogonal directions. The strut has the advantage over the snubber in that the installation cost is less. Two identical piping systems were both experiencing high vibration loading requiring the addition of vibration mitigation supports. One piping system was remediated with snubbers, and the other was remediated with struts. The resulting cost differences and the vibration response of these two piping systems will be discussed. Additionally, the challenges of making these two approaches most effective will be discussed.
Reheat Cracking of Low Alloy Steel During Fabrication and in Service in Oil and Gas Facilities
Authors: Dalal Mitul , Penso Jorge
Published: November 2022

Reheat Cracking is usually associated with the heat affected zone of restrained welded joints during either post weld heat treatment or elevated temperature service. Cracking is associated with the formation of fine intragranular precipitates. This precipitation strengthens the grain interiors and transfers the strain necessary for the relief of residual welding and system stresses to the grain boundaries. The overall effect is a reduction in creep ductility leading to intergranular failure in creep resistant steels. This mode of cracking poses a considerable practical problem particularly because the microstructural and compositional factors affecting its occurrence have not been clearly defined.

In this paper a literature review, case histories descriptions and research in progress are summarized.

The case histories include one overhead fluid catalytic cracking reactor overhead line during fabrication post weld heat treatment) and three high temperature high pressure steam piping after long and short term in service.

Research in progress includes the developing a testing procedure and the quantification of local strain level leading to stress relief cracking (SRC) during post weld heat treatment (PWHT) of welds in creep resistant steels. The testing approach involved implementation of a digital image correlation (DIC) technique with Gleeble-based SRC test.
Safety Advantages of Full-Containment Storage Tanks and the Cost-Effective Implementation for Refrigerated LPG Storage Systems
Authors: Fayez Amin A. , Morris Samuel N. , Alsubaikhy Hani A. , Refai Ali J.
Published: November 2022

Saudi Aramco has been a major player in the LPG (Propane and Butane) market since the 1960s and the company continues to be the source of benchmark pricing in the industry. A variety of refrigerated storage tank concepts have been developed to support international export of LPG products. Currently the industry has shifted to the use of safer full containment tank systems which have the capability to contain liquid and vapor release. Economic implementation of new tank systems has the potential of improving safety at company facilities. The benefit of the full containment storage tank is attractive given that the industry is focused on safety and environmental protection. However, the implementation of this technology is challenging due to the cost. Establishing selection criteria is important for economic implementation of any tank type. The paper explores the key design aspects of each type of tank arrangement based on risk assessment, project requirements and economic factors. The paper provides a case study of a current Saudi Aramco project being planned for new installation of LPG storage tanks at a size of one million barrels for both propane and butane services. The risk assessment examined the compliance, business interruption, environmental impact and other factors related to tank containment failures. The risk assessment and technoeconomic study demonstrates that the double steel full containment design is preferred over the prestressed concrete outer container with steel inner container. The double wall steel full containment tank system has been successfully deployed in facilities at sites around the world including at Marcus Hook, PA in the United Sates and Salalah in Oman. Single containment storage tank is not recommended for large scale of LPG storage or when tank is situated with other nearby facilities. Moreover, single containment type requires more plot area due to external diking requirements compared with double wall and full containment storage designs. Optimization of tank type selection may result in reduction of 6 to 8 months in project schedule and savings to the project of up to 70% of the storage tank installation cost. A risk assessment on different storage tanks designs reveals that the double steel wall full containment design is optimal from a cost and schedule prospective.
Slope Out Welding Development for Thick Section Electron Beam Welding for Pressure Vessel Applications
Authors: Dutilleul Thomas , Widdison Robert , Crossley John , Kyffin William , Albert Marc , Gandy David
Published: November 2022

As part of a Department of Energy (DOE) funded programme assessing advanced manufacturing techniques for SMR applications, the Nuclear AMRC and EPRI have been developing Electron Beam Welding (EBW) parameters and procedures based upon SA508 Grade 3 Class 1 base material.

For linear EB welds, the start and stop regions can be managed by using sacrificial run on/off blocks. However, for circumferential welds, such as joining shell to flange components, the use of sacrificial material is not possible. As such an effective method of closing the keyhole must be developed to ensure that weld defects are not entrained. This process is termed ‘slope out’ welding.

This paper presents results from the steady state welding in the 80–90 mm material thickness range, showing that weld properties meet specification requirements. Subsequently the paper describes the steps in developing an effective slope out welding procedure for circumferential welds. Weld quality was assured by Phased Array Ultrasonic Testing (PAUT) in conjunction with weld sectioning. All welds were assessed against ASME V requirements.

The results presented in this study clearly indicate that defect free and repeatable electron beam welds, including the slope out region, can be produced on thick section pressure vessel steel.
Fracture Mechanical Analyses of a Welding Seam of a Thick-Walled Transport Package
Authors: Gleim Tobias , Neumann Martin , Linnemann Konrad , Komann Steffen , Wille Frank
Published: November 2022

Transport packages shall satisfy various safety criteria regarding mechanical, thermal and radiation phenomena. Typical requirements focusing mechanical aspects are usually drop tests in accordance with IAEA regulations [1]. The drop tests are usually carried out experimentally and, as an additional measure, finite element analyses (FEA) are performed. A specific part of the investigations presented is the evaluation of the welding seam connecting cask shell and cask bottom. Experimental results and FEA are presented and compared. The evaluation of the welding seam performed includes a variety of aspects. In addition to the experimental and analytical stresses determined, different standards are used to investigate a possible crack initiation. Several destructive and non-destructive tests are performed for quality assurance in the manufacturing process as well as for different input parameters. The necessary monitoring and non-destructive measurement methods to define the boundary conditions of the standards are introduced. Taking into account all required parameters, the welding seam is examined and evaluated using the failure assessment diagrams (FAD) of the respective standards. It can be shown under the given boundary conditions that considering the experimental data, the welding seam is in the context of crack initiation below the enveloping curve in the acceptable region. More critical drop tests to be conducted are proposed and need to be investigated in future work.
Recent Developments of Advanced Calculation Concepts for the Fatigue Assessment of Power Plant Components
Authors: Schopf Tim , Weihe Stefan , Rudolph Jürgen
Published: November 2022

The Fatigue lifetime assessment of pressurized components e.g. in nuclear power plants (NPPs) is an essential part of the aging management (AM) ensuring safe and reliable long term operation (LTO). The practically applied calculation procedures of different international codes and standards are widely affected by the basic principles formulated in the criteria document [1]. Those criteria are still fundamental for the fatigue assessment of pressure vessel and power plant components and there is good reason to target at improvements in the consideration of the major factors of influence on the fatigue lifetime while keeping the well-proven methodological framework. This paves the way to related future design code amendment proposals. In practice, there are often large discrepancies between calculated fatigue life and practical experience from power plant operation, where the operating experience reveals much higher fatigue lifetimes as their predictions based on laboratory tests and conservative consideration of major influencing factors (plastification by Ke-factors, Environmentally Assisted Fatigue (EAF) by FEN-factors) in the calculation approach. In the framework of a cooperative research program (see e.g. [2], [3] and [4]) including various subprojects Framatome GmbH, Erlangen, and the Materials Testing Institute MPA Stuttgart have been developing improvements to the fatigue lifetime assessment methods in the framework of the well established engineering approach [1]. These improvements are consolidated by the results of experiments on specimens of ferritic and austenitic stainless steels and austenitic stainless steel welds as well as component tests are performed under laboratory and operating conditions to improve fatigue assessment. The following aspects are going to be pointed out

- Consideration of hold time and environmental (EAF) effects including the threshold and fatigue limit behavior

- Relevance of multiaxial non-proportionality effects for typical power plant operational loading histories

- Consideration of the cyclic elastic-plastic deformation behavior

- Integration of the fatigue damage parameter approach into the calculation concept (particularly modified fatigue damage parameter of Haibach and Lehrke PHL,mod and fatigue damage parameter PJ)

- Low-Cycle (LCF), High-Cycle (HCF) and Very High-Cycle (VHCF) fatigue behavior, interaction and related damage accumulation effects including the transient fatigue limit.

The paper gives an overview of the state of the calculation concept.
Residual Stress Modeling and Advanced Diffraction Measurements of 347H Steel Weldments
Authors: Yang Yi , Han Dong , Gao Yanfei , Zhang Wei , Bunn Jeffrey R. , Payzant E. Andrew , Penso Jorge , Feng Zhili
Published: November 2022

The 347H stainless steel is a primary high-temperature material for many energy and power generation industries. Stress relief cracking (SRC) has been a particular concern in welding of this material. The residual stress induced by welding and its evolution during post-welding heat treatment (PWHT) and subsequent operating and service conditions is one of the primary factors contributing to SRC. The lifetime of welded structure components is also controlled by the precipitation kinetics that accompanies PWHT, stress relaxation process, and long-term aging and complex synergistic factors. Various theories have been proposed in the past to explain SRC. However, a widely accepted approach to predicting the entire damage evolution and the resulting performance reduction is still lacking. This study is to demonstrate a reliable solution for two critical issues that affect the predictions. First, the residual stress distribution obtained from both simulation and neutron diffraction is compared, which increases the accuracy of mechanical analysis simulation model and therefore builds a solid basis for the lifetime prediction model. Second, the generation, evolution, and annihilation of precipitates are monitored by the synchrotron diffraction experiment. Preliminary results demonstrate the critical importance of precipitation kinetics on the residual stress distribution/redistribution during heat treatments.
Fracture Toughness Testing of 316L Steel Manufactured by Laser Powder Bed Fusion
Authors: Tan Ee E. , Sorce Fabian S. , Davies Catrin M.
Published: November 2022

Laser Powder Bed Fusion (LPBF) is a relatively new manufacturing technique that offers many benefits. However, the utilization of selective laser melting (SLM) manufactured components depends on the assurance of their integrity during operation. Samples manufactured through LPBF are prone to defects. Therefore, it is important to determine the fracture toughness of the materials. In this work, fracture toughness tests on single edge notched bend (SENB) samples have been performed and the results are presented. The samples have been manufactured in 3 orthogonal directions enabling the influence of defect orientation relative to the build direction on toughness to be determined. The crack growth has been monitored using both elastic compliance and the potential drop (PD) technique, and the crack tip strain fields have been imaged using digital image correlation techniques. It has been found that the toughness of samples with the crack plane parallel to the build layers (vertical) is greater than that of samples with the crack plane normal to the build layers (horizontal), contrary to expectations based on previous research. This behavior is likely to be a result of changes in porosity ahead of the crack tip due to inadvertent cooling effects during the build process, resulting in fewer build defects ahead of the crack tip in the “vertical” samples.