bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Laser Peening for Mitigation of Primary Water Stress Corrosion Cracking in Pressurized Water Reactors
Authors: Marlette Stephen , Bovid Stan 
Published: November 2019

Abstract
For several decades pressurized water reactors have experienced Primary Water Stress Corrosion Cracking (PWSCC) within Alloy 600 components and welds. The nuclear industry has developed several methods for mitigation of PWSCC to prevent costly repairs to pressurized water reactor (PWR) components including surface stress improvement by peening. Laser shock peening (LSP) is one method to effectively place the surface of a PWSCC susceptible component into compression and significantly reduce the potential for crack initiation during future operation. The Material Reliability Program (MRP) has issued MRP-335, which provides guidelines for effective mitigation of reactor vessel heads and nozzles constructed of Alloy 600 material. In addition, ASME Code Case N-729-6 provides performance requirements for peening processes applied to reactor vessel head penetrations in order to prevent degradation and take advantage of inspection relief, which will reduce operating costs for nuclear plants.
LSP Technologies, Inc. (LSPT) has developed and utilized a proprietary LSP system called the Procudo® 200 Laser Peening System. System specifications are laser energy of 10 J, pulse width of 20 ns, and repetition rate of 20 Hz. Scalable processing intensity is provided through automated focusing optics control. For the presented work, power densities of 4 to 9.5 GW/cm2 and spot sizes of nominally 2 mm were selected. This system has been used effectively in many non-nuclear industries including aerospace, power generation, automotive, and oil and gas. The Procudo® 200 Laser Peening System will be used to process reactor vessel heads in the United States for mitigation of PWSCC. The Procudo® 200 Laser Peening System is a versatile and portable system that can be deployed in many variations.
This paper presents test results used to evaluate the effectiveness of the Procudo® 200 Laser Peening System on Alloy 600 material and welds. As a part of the qualification process, testing was performed to demonstrate compliance with industry requirements. The test results include surface stress measurements on laser peened Alloy 600, and Alloy 182 coupons using x-ray diffraction (XRD) and crack compliance (slitting) stress measurement techniques. The test results are compared to stress criteria developed based on the performance requirements documented in MRP-335 and Code Case N-729-6. Other test results include surface roughness measurements and percent of cold work induced by the peening process. The test results demonstrate the ability of the LSP process to induce the level and depth of compression required for mitigation of PWSCC and that the process does not result in adverse conditions within the material.
Analysis on Engineering Calculations for Connected Double Tubesheets
Authors: Zhu Guodong , Qian Caifu , Shou Binan , Xie Guoshan , Han Zhiyuan 
Published: November 2019

Abstract
Calculation procedures for the connected double tubesheets is based on single tubesheet in current standards. Current situation, calculation methods and calculation procedures were introduced in this paper. Some options in calculation procedure for connected double tubesheets were not specified yet in standards and make engineers confused. It was point out that deformation features and stress levels in tubesheet can be qualitatively analyzed by means of two key constrain parameters m and K. The two Parameters are helpful to analyze the differences and relations between single tubesheet and double tubesheets in engineering design. Examples were calculated with different procedure options to compare with FEA after qualitatively analysis. The reasonability of different calculation procedures was discussed based on inner and outer tubesheet respectively. The preferences of procedure options were put forward to improve and perfect specification in current standards finally.
Research on Post-Fire Metallographic Structure and Hardness of Quenched and Tempered High Strength Steel 07MnMoVR
Authors: Shao Shanshan , Jia Guodong , Cao Luowei , Deng Guide 
Published: November 2019

Abstract
Quenched and tempered high strength steel 07MnMoVR provides an excellent combination of strength and toughness potentially providing significant cost savings in petrochemical industry. Exposure to fire will subject steel to thermal conditions that may alter the material’s microstructure and properties. The extent of the fire damage and the potential reusability of the components can be evaluated by fitness-for-service (FFS) assessment after a fire event. According to API 579-1/ASME FFS-1, metallurgical investigation and mechanical testing are the chief means for the assessment of fire damage. This paper presents the details of an experimental investigation on the post-fire metallographic structure and hardness of 07MnMoVR steel. Metallographic analyses and hardness testing were performed on coupons exposed to elevated temperatures varying from 550°C to 850°C for half an hour to 8 hours and then naturally cooled in air or cooled by water.
The results show that the microstructure of as-received 07MnMoVR steel consisted of tempered sorbite and bainite. With increasing heat exposure temperature, bainite disappeared gradually. The recovery and recrystallization of ferrite began to occur after heat exposure at 650°C for 5hrs. When the heat exposure temperature exceeded 750°C, the effects of duration time and cooling rate on microstructure were both significant. A linear correlation is indicated by fitting the ultimate tensile strength and hardness. Due to the drastically degradation of impact toughness of 07MnMoVR steel after heat exposure exceeded 650°C, it is suggested that the removal and testing of material samples shall be utilized to evaluate the fire damage of components, besides replication or in-situ field metallography and hardness testing. This study can provide basis data and guidelines for the fitness-for-service assessment of 07MnMoVR steel suffered from a fire event.
HRSG-Pipeline Weld Residual-Stress Measurement to Assess Influence Over Creep-Analysis Results From Italian Code, American Standard
Authors: Grisolia Ottaviano , Scano Lorenzo , Piccini Francesco , Lo Conte Antonietta , De Agostinis Massimiliano , Fini Stefano 
Published: November 2019

Abstract
Previous study carried out residual stress characterization for the welds of the high-temperature-section (superheater / reheater) lower headers of the bottom-supported heat-recovery steam generator (HRSG). Modeling the gas-tungsten arc, manual welding process considered only weld-lay for the ASTM A 335-Grade P22 finned-tube angle joint to the cylinder. Present study aims at indirectly assessing findings of previous analysis measuring maximum residual stress on the joint’s exservice material. To achieve that a tee similar to the previous was not available: for both experimental and numerical analyses present study considers a P22 circumferential “V”-groove butt joint on HRSG pipeline section, creep-operated for the same period and temperature as the previous case. In the experimental activity X-ray diffraction method (or alternatively, hole-drilling strain gage one) applies as close as possible to the weld, being residual stress maximum at the fusion boundary. Thermal analysis for the previous case also showed it keeps nearly constant during weld cooling, relaxing most during creep: after 200,000 hours of operation, welding-process simulation predicted a maximum residual stress of 70 MPa; tee-joint creep-analysis found out a maximum equivalent stress of 91 MPa. As for the sample withdrawal, dimensions should be sufficient to avoid any interference with measurement area. The experimental procedures should comply with the European standard EN 15305 on the matter (the American standard ASTM E 837 for the alternate method). Comparison of analysis results for the two cases, confirms tendencies previously found out in creep-behavior, though different equivalent stress contributions. Comparison of predicted and observed residual stress values should allow for validation of numerical models used in both welding process and stress analysis.
Improvement of Low-Temperature Toughness in Weld Metal Made of 9Cr-1Mo-V Steel by GTAW Method
Authors: Nakano Masakatsu , Tanaka Tomohiro , Abe Masamitsu , Nakatani Mitsuyoshi , Terasaki Hidenori 
Published: November 2019

Abstract
Energy demand will increase due to global population growth in the future. As one of solutions for the demand, it will be necessary to operate petroleum service plants more efficiently. To improve refining efficiency, operation at higher temperatures is required of reactors used in high-pressure hydrogen service at the plants. 9Cr-1Mo-V steel has excellent creep strength compared to 2 1/4Cr-1Mo steel and 2 1/4Cr-1Mo-V steel, which have been conventionally applied to reactors, and has been already put into commercial use for boilers of thermal power plants, etc. Further application of 9Cr-1Mo-V steel is expected for reactors at petroleum refining plants. As materials applied to reactors, low-temperature toughness should be considered for weld joints in addition to creep strength. However, 9Cr-1Mo-V steel has poor low-temperature toughness compared to 2 1/4Cr-1Mo steel and 2 1/4Cr-1Mo-V steel. As for the welding methods applied to reactors, Submerged Arc Welding (SAW), Shielded Metal Arc Welding (SMAW), and Gas Tungsten Arc Welding (GTAW) can be used. The 9Cr-1Mo-V steel weld metals formed by SAW and SMAW have a high oxygen content, and their low-temperature toughness is inferior to that of the weld metal formed by GTAW. On the other hand, the GTAW weld metal has a low oxygen content and excellent low-temperature toughness. Therefore, GTAW is an effective way to improve the toughness of the weld metal. However, GTAW has low productivity compared with others, so it is necessary to apply to a narrow groove and a hot wire method to improve the productivity.
In this paper, the application of narrow gap GTAW using the hot wire method was considered for welding of 9Cr-1Mo-V steel. When using the hot wire method, productivity of GTAW increases in comparison to the conventional method, leading to increased weld pass thickness. With the increase in pass thickness, the area of coarse grains increases because of decreasing thermal effect by the subsequent pass, then the low-temperature toughness decreases. Therefore, in order to improve the low-temperature toughness by refining the grains of the GTAW weld metal, the melt-run method, arc re-melting without adding fillers, was conducted after the former weld pass metal solidified. The weld metal from the melt-run method had finer grains compared with those of the weld metal without the melt-run method, and the low-temperature toughness increased. On the other hand, the melt-run method requires two processes: welding and melt-run. Therefore, a tandem electrode GTAW machine was produced in which an electrode for welding and the other one for melt-run were placed continuously to make it possible to execute welding and a melt-run without a time lag. As a result, it is possible to manufacture reactors made of 9Cr-1Mo-V steel for petroleum refining plants with sufficient low-temperature toughness by applying a welding method with narrow gap GTAW and a melt-run method combined.
Plastic Collapse Stresses for Thick Wall Pipes With External Cracks
Authors: Hasegawa Kunio , Li Yinsheng , Lacroix Valery , Mares Vratislav 
Published: November 2019

Abstract
Bending stress at plastic collapse for a circumferentially cracked pipe is predicted by limit load equation provided by the Appendix C of the ASME Code Section XI. The equation of the Appendix C is applicable for pipes with both external and internal surface cracks. On the other hand, the authors have developed an equation taking into account the pipe mean radii at non-cracked area and at cracked ligament area. From the comparison of Appendix C equation and the new equation, the plastic collapse stress estimated by the Appendix C equation gives 20 to 30% less conservative bending capacity prediction for external cracked pipes with small Rm/t, where Rm is the pipe mean radius and t is the pipe wall thickness. This paper discusses the limitation of the use of Rm/t for the Appendix C equation.
Study on Key Process Parameters of the Local Post Weld Heat Treatment by Electric Heating for the Large Thick-Walled Pressure Vessel Cylinder Butt Weld
Authors: Ji Fang , Deng Guide , Sun Liang , Liu Cenfan , Zhao Xiaonan 
Published: November 2019

Abstract
The local post weld heat treatment for pressure vessel cylinder butt circumferential weld performed by resistance heating a shielded band around the entire circumference. The width of heated band must be large enough to ensure that the temperature of the weld, heat-effect zone and a portion of base metal adjacent to the weld should meet the requirement given in the standards. When the diameter of pressure vessel cylinder is enough large to allow the installation of heater and thermal insulation on the inner surface of wall, the circumferential butt weld heated simultaneously on interior and exterior surface of cylinder wall is more energy economical. However, GB/T 30583-2014 don’t provide the recommended width of heated band for the local post weld heat treatment performed by heating simultaneously on the inner and outer surface of cylindrical wall when the wall thickness is large than 50mm. So numerical simulation was carried out to study the effect of the width of heated band on the soak band temperature distribution when the local post weld heat treatment for cylinder pressure vessel with the thickness rang of 60mm∼100mm performed by heating simultaneously on interior and exterior surface in this paper. The results show that the widths of heated band should be not less than six times thickness when post weld heat treatment for cylinder pressure vessel butt welds whose thickness is 60mm∼70mm with a diameter of 2000 mm performed by heating simultaneously on interior and exterior surface and the widths of heated band should be not less than five times thickness when post weld heat treatment for cylinder pressure vessel butt welds whose thickness is 70mm∼100mm.
Study on Buckling Strength Reduction Factor for Vertical Vessel Skirts With Access Opening by Elastic-Plastic Analysis
Authors: Takahashi Takuma , Kataoka Shunji , Uno Yoshiaki , Miyashita Toshikazu 
Published: November 2019

Abstract
Access opening is a key geometric feature of vertical vessel skirts. To ensure the structural stability of skirts, buckling strength reduction caused by openings shall be numerically evaluated.
In the previous study, Buckling Strength Reduction Factor (BSRF) was introduced as a design factor representing the effects of openings. However BSRF is based on the elastic bifurcation buckling under axial compressive load. The relations between BSRF and practical design conditions, such as bending moment, material plasticity, and local deformation, are not yet evaluated.
The purpose of this paper is to develop the buckling design method for vertical vessel skirts with access opening by investigating the relation between BSRF in consideration of practical design conditions and conventional design concepts for straight cylinder. The finite element analyses of buckling strength were conducted for cylindrical shells with and without openings under bending moments. In addition, nonlinear buckling behaviors of skirts with opening were studied by elastic-plastic analyses and limit-load analyses. These studies revealed the relation between BSRF and conventional buckling design concepts. Based on these results, a new buckling design approach which includes the application BSRF was proposed. This proposed approach provides a practical guide for buckling design of vertical vessel skirts with access opening.
Probabilistic Methods: Risk Based Design and Assessment
Authors: Cathcart H. , Horne G. , Parkinson J. , Moffat A. , Joyce M. 
Published: November 2019

Abstract
Structural integrity assessments typically aim to calculate the integrity of a component under nominal or best estimate conditions. To account for potential variability and uncertainty present in the system, safety factors are often applied to assessment inputs and outputs. This approach does not allow the level of conservatism present to be quantified, often leading to over-conservatism or inadvertent non-conservatism. Probabilistic assessments explicitly calculate the probability of failure based on distributions of the input parameters and hence quantify the margin present in the assessment, leading to a greater understanding of the system.
In this study a creep-fatigue damage assessment of a transiently loaded piping component is used as a vehicle to investigate some of the challenges and benefits of probabilistic assessments. A probabilistic assessment of the component life is compared to a lower-bound deterministic calculation to identify the mismatch in margin between the two results. The potential inaccuracies introduced when reducing the computational burden of Monte Carlo simulations with response surface methodologies are explored and tested. Finally, two challenges when attempting to underwrite a very low probability of failure are tackled: the inference of the shape of a distribution’s tails from limited experimental data and the uncertainty of extreme percentiles of finite Monte Carlo samples.
Generic Proximity Rules for Multiple Radially Oriented Planar Flaws: Technical Basis of Code Case N-877 Revision 1
Authors: Dulieu Pierre , Lacroix Valéry , Hasegawa Kunio 
Published: November 2019

Abstract
In the case of planar flaws detected in pressure components, flaw characterization plays a major role in the flaw acceptability assessment. When the detected flaws are in close proximity, proximity rules given in the Fitness-for-Service (FFS) Codes require to combine the interacting flaws into a single flaw. However, the specific combination criteria of planar flaws vary across the FFS Codes. These criteria are often based on flaw depth and distance between flaws only. However, the level of interaction depends on more parameters such as the relative position of flaws, the flaw sizes and their aspect ratio. In this context, revised and improved proximity criteria have been developed to more precisely reflect the actual interaction between planar flaws. Thanks to numerous three-dimensional XFEM analyses, a wide range of configurations has been covered, including interaction between two surface flaws, interaction between two subsurface flaws and interaction between a surface flaw and a subsurface flaw. This paper explains in detail the steps followed to derive such generic proximity rules for radially oriented planar flaws.
Research on Risk Assessment Method and System Development of Small Ammonia Refrigeration Units
Authors: Li Xiang , Wang Weihua , Jing Weike , Shi Jin , Zhuang Fakun 
Published: November 2019

Abstract
In recent years, ammonia leakage accidents occur frequently, which causes a great concern in China. Based on traditional risk analysis methods and the equipment characteristics, a risk evaluation method for small ammonia refrigeration units is proposed. The method includes a risk assessment model based on area division, a failure probability assessment method based on expert scoring system, a failure consequence assessment method based on regional population density and consequence mitigation measures, and a HAZOP risk correction method. Based on the proposed method, a risk assessment system of small ammonia refrigeration units is developed. This risk assessment method and system will provide a scientific basis to carry out the cold storage management in China.
Addressing Shell Mode Vibration in Ducts in Refinery With Computational Models and Field Data
Authors: Chakraborty Ishita , Paul Anup , Szasz Gyorgy 
Published: November 2019

Abstract
This paper describes the work performed to study the shell mode vibration of a large cross-section flue gas duct. The work involved the collection of field vibration data, as well as predictive computational models associated with finite element analysis (FEA) and computational fluid dynamics (CFD). The goal of this work was to use predictive models to ascertain whether a proposed design change would reduce the vibration levels of the duct under similar operating conditions. The vibration observed in the duct was identified as a flow induced vibration (FIV) which excited the shell modes of the duct walls.
This case study serves as an example of using predictive computational models (FEA and CFD), calibrated with vibration response data from field measurements, to represent the real world situation as closely as possible within specified budget and schedule constraints. Such calibrated models can be useful for forecasting the effectiveness of various proposed design changes.
Isochronous Stress-Strain Curves for Alloy 617
Authors: Messner M. C. , Sham T.-L. 
Published: November 2019

Abstract
Alloy 617 is a high temperature nickel based material that could have significant design advantages when compared to austenitic steels in very high temperature reactor applications. Several high temperature design methods, including Section III, Division 5 of the ASME Boiler & Pressure Vessel Code, require a model for the creep and high temperature plastic deformation of a material, quantified as a set of isochronous stress-strain curves. This paper describes the development of a model for the high temperature deformation of Alloy 617. This model is then used to generate design hot tensile and isochronous stress strain curves suitable for use in Section III, Division 5 and other high temperature design methods.
Development of Simplified Model Test Methods for Creep-Fatigue Evaluation
Authors: Wang Y. , Jetter B. , Messner M. C. , Sham T.-L. 
Published: November 2019

Abstract
The Simplified Model Test (SMT) approach is an alternative creep-fatigue evaluation method that no longer requires the use of the damage interaction diagram, or D-diagram. The reason is that the combined effects of creep and fatigue are accounted for in the test data by means of a SMT specimen that is designed to replicate or bound the stress and strain redistribution that occurs in actual components when loaded in the creep regime. However, creep-fatigue experiments on SMT key feature articles are specialized and difficult to perform by the general research community. In this paper, two innovative SMT based creep-fatigue experimental methods are developed and implemented. These newly-developed SMT test methods have resolved all the critical challenges in the SMT key feature article testing and enable the potential of further development of the SMT based creep-fatigue evaluation method into a standard testing method. Scoping test results on Alloy 617 and SS 316H using the newly developed SMT methods are summarized and discussed. The concepts of the SMT methodology for creep-fatigue evaluation are explained.