bluuebunny/crossref_metadata_2025_split huggingface dataset:
Creep Damage Predictions Under Multiaxial Conditions for 316L Stainless Steel Samples Manufactured by Laser Powder Bed Fusion
Authors: Burridge D. J. , Davies C. M. 
Published: October 2021

Abstract
316L stainless steel, often used for high-temperature applications, can be manufactured by laser powder bed fusion (LPBF). However, the LFBF manufacturing process can lead to undesirable multiaxial residual stresses (RS), which may require relaxation by heat treatments. The high residual stresses combined with high operating temperatures will induce creep deformation and damage processes. Therefore, the creep behaviour of LPBF 316L under multiaxial stress conditions must be understood, and models are available to predict the creep deformation and damage processes.
In this work, a FE modelling methodology has been developed and validated by simulating the creep deformation and damage accumulation in notched bar tests on samples with two different notched acuities, denoted large and medium notches. Notched bar creep tests were simulated for samples built in both the horizontal and vertical orientations (i.e. parallel and perpendicular to the build direction). A new progressive creep damage modelling approach was applied, based on the creep ductility exhaustion approach, enabling the progressive deterioration of material properties as creep damage accumulates. A sensitivity study was performed to account for the significant variabilities in creep deformation rates and creep ductility in LPBF samples. It was generally found that accurate predictions of the creep deformation and failure behaviour could be obtained using a specific combination of creep strain rate and ductility bounds; however, some tests results, particularly for vertically built samples, were not predictable. This has been attributed to the deleterious effects of porosity resulting from the build process.
NuScale Pressure and Temperature Limits Methodology Using Finite Element Analysis
Authors: Xu Heqin , Remic Joe , Xu Hongqing 
Published: October 2021

Abstract
Per 10 CFR 50 Appendix G, the pressure-temperature (P-T) limit curves and minimum temperature must be established to provide adequate margins for ferritic pressure-retaining components of the reactor coolant pressure boundary; this is to protect against brittle failure during any normal operating conditions, including anticipated operational occurrences and system hydrostatic tests, to which the pressure boundary may be subjected over its service lifetime. Specifically, the American Society of Mechanical Engineers (ASME) Code Section XI Appendix G procedures must be used for P-T limit calculations considering the pressure and temperature at various operating transient conditions. However, the elastic fracture mechanics solutions in Section XI are only suitable for cylindrical reactor pressure vessel (RPV) beltline without geometric discontinuities. Hence, these solutions are not suitable for postulated flaws near the core support blocks attached to the NuScale RPV inside surface, which is part of the beltline. As a result, NuScale has used finite element analysis to calculate thermal stress and stress intensity factors for the postulated flaws. The solutions using finite-element analysis have been validated using the formulations for straight cylinders for both axial and circumferential flaws. In addition, special considerations are given to the RPV beltline nil-ductility transition temperature (RTNDT) due to neutron irradiation occurring at lower temperatures than conventional plants. This paper summarizes the methodology and finite-element models used to develop P-T limit curves for the NuScale RPV at the end of its 60-year design life.
Application of Risk-Based Design Methodology to Tuned Mass Damper
Authors: Corritore Daniele , Minagawa Keisuke , Paolacci Fabrizio 
Published: October 2021

Abstract
Suppressing earthquake damage in chemical plants has great benefits not only to a business continuity of a company but also to surrounding areas and social activities. For example, chemical plants have a lot of slender structures such as distillation columns and chimneys, which may be damaged by large earthquakes. Tuned mass dampers (TMDs) are one of the effective approaches to suppress seismic response of slender structures. The TMD consists of a mass, a spring and a damper, and it is generally installed at the top of a target structure. The damping effect depends on the mass, natural frequency, damping ratio of the TMD. In general, its natural frequency and damping ratio can be determined by the optimum tuning theory and a TMD having large mass has good performance of vibration control. However, the cost of TMD depends on the mass. In addition, since the optimum tuning theory assumes that the target structure is a simple single degree of freedom system, application of the optimum tuning theory to the TMD for a slender structure is not easy. Therefore, this study proposes a risk-based design methodology for TMDs. The proposed method considers a seismic hazard of a site where a target structure located and a damage state of the target structure. Then the mean annual frequency of exceeding the damage state can be calculated as function of the mass of the TMD.
Example Proposals of Fracture Controlled Vessels and Piping for Failure Mitigations
Authors: Kasahara Naoto , Wakai Takashi , Nakamura Izumi , Sato Takuya , Ichimiya Masakazu 
Published: October 2021

Abstract
As a lesson learned from the Fukushima nuclear power plant accident, the industry recognized the importance of mitigating accident consequences after Beyond Design Basis Events (BDBE). We propose the concept of applying fracture control to mitigate failure consequences of nuclear components under BDBE. This paper discusses example applications of our proposed method to vessels and piping.
As an example for vessels, the fracture controlled method of a fast reactor vessel was proposed to maintain coolant under high pressure and high temperature conditions. One of the important accidents to consider is fuel criticality upon a core meltdown. This accident will cause high temperature and high pressure conditions in the vessel.
To maintain coolant to cover the fuel under above conditions, strength of the upper part of a vessel is controlled to be weaker than the lower part. When the upper parts fail, internal pressure will be released and the lower part will be protected. Coolant of fast reactors is liquid metal with a high boiling point. Therefore, there is no boiling when the pressure drops. As a result, the coolant stays within the vessel for continuous cooling after accidents. If nozzles penetrate only the upper part of a vessel, controlling strengths at the structural discontinuities can realize the proposed method.
As a piping example, the fracture controlled method of main steam piping of a BWR was proposed to avoid collapse and break under excessive earthquake. The piping is constrained by supports to the building. Strength of piping supports should be weaker than that of the piping. If piping supports break before the piping, natural frequencies of piping decrease increasing the frequency ratios. When their frequency ratios are larger than one, the seismic energy hardly transfers to the piping and the piping will not collapse or break. When the primary stresses from dead weight are not negligible, simple supports by wire are enough to protect piping against dead weight.
Numerical Investigation of Ductile Fracture in Pipelines Under Complex Loading Using a Phenomenological Damage Model
Authors: Santos Iago S. , Sarzosa Diego F. B. 
Published: October 2021

Abstract
This paper presents a numerical study on pipes ductile fracture mechanical response using a phenomenological computational damage model. The damage is controlled by an initiation criterion dependent on the stress triaxiality and the Lode angle parameter, and a post-initiation damage law to eliminate each finite element from the mesh. Experimental tests were carried out to calibrate the elastoplastic response, damage parameters and validate the FEM models. The tested geometries were round bars having smooth and notched cross-section, flat notched specimens under axial tensile loads, and fracture toughness tests in deeply cracked bending specimens SE(B) and compact tension samples C(T). The calibrated numerical procedure was applied to execute a parametric study in pipes with circumferential surface cracks subjected to tensile and internal pressure loads simultaneously. The effects of the variation of geometric parameters and the load applications on the pipes strain capacity were investigated. The influence of longitudinal misalignment between adjacent pipes was also investigated.
The Influence of Low Melting Point Elements on Hot-Cracking of 310 Austenitic Stainless Steel
Authors: Almomani Abdulla Fawzi , Alhaj Hazem , Ismail Mourad Abdel-Hamid 
Published: October 2021

Abstract
This work highlights the influence of the low melting point elements such as sulfur, phosphorus, and silicon together with the delta (δ) ferrite content on the susceptibility of austenitic stainless-steel grade 310S welding to hot cracking. Defected weld seams from a vessel component were analyzed in this work. Transverse linear cracks on both the circumferential and longitudinal welding seams, with excess bleeding, were revealed during the examination of the defected welding joints through Dye Penetrant Testing (DPT). The ferrite number (FN), i.e., a description of the ferrite content, was found to be less than 1.0 FN on the weld metal (WM) and 1.5 FN on the parent metal (PM). Hardness testing showed high values (295 HB max.) on the parent material PM while it was found within the range (211 HB max.) at the WM. The chemical composition of the WM, with the use of X-Ray Fluorescence (XRF) spectrometer, revealed 0.09% S, 0.09% P and 2.27% Si which are deemed to be in critical range against the susceptibility of 310S to solidification cracking. The microstructure of the weld material WM displayed extensive cracking at the austenite grain boundaries of the cellular dendrites, in which film-like features were observed on the crack surfaces along the interdentric interfaces. It is suggested that sulfur S and phosphorus P combine with iron to form low-melting compounds, which as a result can form low melting eutectics with impact to segregate at the austenitic grain boundaries during solidification. Hence and in line with the literature, adequate control of S and P to less than 0.002%, and Si away from 1.5–2.5% was found key in minimizing the susceptibility of 310S welding joints to hot cracking.
Application of the Williams-Wittrick Algorithm for Thin Shell Vibrations Problems
Authors: Dubyk Yaroslav , Ishchenko Oleksii 
Published: October 2021

Abstract
This article presents adaptation of the Wittrick-Williams algorithm to calculate the natural vibration frequencies of cylindrical shells. Initially, the “algorithm” was proposed and used to find the natural frequencies of branched piping systems (trusses) in structural mechanics problems. We expanded it for shells, where a more difficult system of main differential equations is solved, with increasing calculation effort. The Wittrick-Williams algorithm was chosen to find vibration frequencies, because it is the only one exact solution for the transcendental eigenvalue problem. The “algorithm” gives the number of natural frequencies below a trial value of frequency, therefore, using bisection method, as the simplest, it is possible to find frequencies with sufficient accuracy. It can been used, for example, in a dynamic analysis, where it is important to find accurately the lower frequencies, and to distinguish between coupled frequencies. For solution the shell must been divided into a certain number of parts; convergence graphs are given, according to which the optimal number of partitions is selected. Obtained results show good convergence with experimental and literature data for different boundary conditions. Several special cases have been considered for shells with different values of elastic boundary conditions. The method has proven to be practical and can been used for modal, harmonic and seismic analysis.
A Newly Developed Measuring Principle for Precise Measurement of Forces in Test Autoclaves
Authors: Oßwald Alexandra , Werz Martin , Weihe Stefan 
Published: October 2021

Abstract
For material testing under environmental conditions like pressure, test medium and temperature, testing machines are extended with autoclave units in which controlled ambient conditions are set. The load is applied to the specimen placed inside the autoclave from the outside via rods. Thepressure of the testing environment is sealed by the autoclave system. The challenge of this setup is the correct measurement of the specimen force due to the frictional forces on the gasket. The most current problem in this field, on which we focus our work, is the precise determination of material properties under high-pressure hydrogen atmosphere.
At the Materials Testing Institute (MPA) University of Stuttgart, a new measurement principle was developed which solves the conflicting objectives of precise force measurement and reusability of strain gauges. This is achieved by applying the strain gauges on the inside of the load rod which transfers the force onto the specimen inside the autoclave. The newly developed measuring principle was integrated into an existing testing machine. The applicability of the measuring setup was validated in experimental tests under cyclic load and with the test environment of highly pressurized hydrogen. With the help of the new test setup, it is possible to measure the actual specimen force, i.e. without the influence of the frictional force of the gasket.
Gasket Design for Alkylation Units & Other Possible Dangerous Liquid Media
Authors: Norman Dale , Navarrete Gustavo 
Published: October 2021

Abstract
The design and testing of gaskets for severe, possibly life threatening, liquid media, like hydrofluoric acid, is critical and difficult. This paper shows the relationship between basic gasket stress calculations, of applied load over the gasket sealing area, actual gasket stress test results, and dye penetrant test results. The gasket designs evaluated will be from across the industry and follow the typical design of having expanded PTFE (ePTFE) as the inner sealing element for the harsh media and a redundant flexible graphite sealing element that will seal the media as well as give an expected fire test rating.
The gaskets tested had different structural designs for sealing the media as well as providing corrosive protection for the clamping flanges. There was both supported and unsupported ePTFE sealing elements. Some designs are new, and one has been in service for years. The basic calculations typically used to determine adequate gasket stress showed that all the gaskets should seal effectively. The question is: Would they all equally help protect the flange face from corrosive damage?
The data from the actual applied gasket stress correlates nearly perfectly to the dye penetrant results but varies from expected stress distribution of the typical gasket stress calculation. The paper will cover the theoretical calculation approach, the test methodology for the actual applied gasket stress, the methods for ensuring applicable dye penetrant testing and comparing the results to each other. The results show that under equal clamping loads, the different structural designs directly impact the ability for fluid to penetrate the ePTFE section of the gaskets.
Study on Flow-Induced Vibration of Self-Regulation Check Valve During Opening
Authors: Liu Shuai , Huang Xuan , Feng ZhiPeng , Jiang XiaoZhou , Wang BiHao , Wu WanJun 
Published: October 2021

Abstract
Pump-Valve-Pipeline is an important part of the power plant. It plays a key role in the normal operation of the reactor. The vibration of the system can bring harm to itself and also lead to the safety troubles and noise of other parts. As an important over-flow component, the structure and the adjustment method of check valve is complex, which can lead to pressure fluctuation and result in oscillation problems seriously. The study is to explore the characteristics of the internal flow field and pressure fluctuation of the check valve. Especially, the characteristics of internal flow field and the abnormal fluctuations are concerned during the moving process of the valve core and valve stem. There are many researches focusing on flow vibration under fixed opening of the valve, which can not reflect the real opening process of the valve. In this paper, the abnormal fluctuation of internal flow-field for the check valve is studied. Based on the UDF dynamic grid technology, the transient motion law equation of the moving parts is established as the moving boundary of the fluid. The transient motion analysis model of the check valve is constructed to simulate the dynamic opening process of the valve. The vibration characteristics of the valve with different spring stiffness are studied, which can provide guidance for the regulation of the valve in the system.
Pilot Study on Seismic Fragility Evaluation for Degraded Austenitic Stainless Steel Piping Using the Probabilistic Fracture Mechanics Code PASCAL-SP
Authors: Azuma Kisaburo , Yamaguchi Yoshihito , Li Yinsheng 
Published: October 2021

Abstract
Seismic probabilistic risk assessment is a standard methodology to quantify the risk of earthquakes including beyond-design-basis levels. The quality of fragility analysis is one of the major factors that affect the results of seismic probabilistic risk assessments. A previous study revealed that component degradation could affect seismic fragility. In practice, inspection and maintenance programs are implemented to control an undesirable effect of the degradation such as stress corrosion cracking. However, the relation between seismic fragility of degraded component and inspection, maintenance, and mitigation models has not been thoroughly discussed so far. This study discussed the effect of inspection and maintenance on seismic fragility of austenitic stainless steel piping susceptible to stress corrosion cracking. Failure probability was calculated by using a probabilistic fracture mechanics code. The results indicated that the adverse effects of stress corrosion cracking on failure probability could be controlled at a relatively low level if inspection, maintenance, and mitigation measures were implemented properly.
Mechanical Response of an Industrial Piping System Under Strong Cyclic Loading
Authors: Karvelas C. , Chatzopoulou G. , Zervaki A. D. , Stathas N. , Strepelias E. , Palios X. , Bousias S. N. , Karamanos S. A. 
Published: October 2021

Abstract
The paper presents a combined experimental and numerical investigation of cyclic loading response of an internally pressurized steel piping system. The piping system comprises three elbows and is subjected to quasi-static end-displacement excitation. Global deformation and local strain measurements are obtained, indicating significant strain ratcheting at the critical locations of the elbows. The piping system failed under low-cycle fatigue undergoing through-thickness cracking at the flank of the most strained elbow. Post-fatigue metallographic examination of the elbows indicated that fatigue cracking initiates from the inner surface of the pipe elbow. In all elbows, several micro-cracks develop along the inner surface of elbow flanks, whereas the outer surface remained practically intact before through-thickness cracking. Finite element simulations, with a properly calibrated cyclic-plasticity model calibrated properly in terms of small-scale material tests, provide very good predictions in terms of local strain evolution at critical locations.
Investigation of the Irradiation Effect on the Dynamics of Nuclear Fuel Bundles
Authors: Elbanhawy Osama , Hassan Marwan , Mohany Atef , Kishawy Hossam 
Published: October 2021

Abstract
Fuel bundles in nuclear power plants are subjected to severe operation conditions, such as highly turbulent coolant flow, high temperatures and excessive irradiation doses. These irradiation doses affect the microstructure of the material in terms of segregation and precipitation in addition to swelling. For instance, densification occurs when material pores are removed after irradiation. In contrast, swelling occurs when gaseous pores of fission products start to fill materials used in the reactor core components. All these effects influence the mechanical properties of the material and consequentially its dynamic characteristics. The present study aims at developing a fully-coupled three dimensional numerical model that utilizes the irradiated fuel bundle material as a non-linear material rather than a linear one. The non-linearity is accounted for with the aid of a constitutive model that describes the thermal and irradiation effects on the mechanical properties. Then this constitutive model is integrated in an in-house finite element code that is capable of predicting the dynamics of non-linear material. The model is applied to a CANDU fuel bundle, in which each fuel element is discretized using 12-DOF beam elements and the endplates are discretized using plate elements. The dynamic response of the fuel bundle is investigated under turbulence excitation, which is generated by the coolant flow inside the pressure tube. Moreover, the fuel-to-fuel and fuel-to-pressure tube contact is also included using the single point contact method (SPC). The dynamic response of the fuel bundle along with the associated impact forces and work rates are investigated over a range of flow velocities that are typical to those in an actual CANDU power plant. A summary of the results is presented in this paper.
Experimental Characterization of the Ageing Behaviour of Anaerobic Threadlockers
Authors: Croccolo Dario , De Agostinis Massimiliano , Fini Stefano , Olmi Giorgio , Paiardini Luca , Robusto Francesco 
Published: October 2021

Abstract
Threadlockers are widely used in threaded connections in order to prevent the preload loss (e.g., due to self-loosening). Threadlockers are commercially available in different formulations, such as liquid (to be applied just before tightening) or semi-solid (pre-applied on the screw). Previous research focused on both the frictional behaviour at tightening of the joint with applied threadlocker, and on the breakaway torque of the joint after complete polimerization of the threadlocker. Nonetheless, threadlocker-enhanced joints are often operated at variable levels of temperature and humidity. A literature survey reveals lack of data about the residual strength of threadlocker-enhanced joints after operation at temperature/humidity levels different by the reference ambient levels. The present research tackles the aforementioned issue, by means of an experimental campaign carried out on a liquid medium-strength anaerobic adhesive applied to metric, 8.8 grade, Zinc-coated screws. Upon complete polimerization of the adhesive, the joints have been aged in an environmental chamber at four different combinations of temperature (RT – 90°C) and humidity (20%–90%) for one week. The joints have then been unlocked, sampling the breakaway torque. Statistical analysis of the data has been carried out to determine the significance of each parameter on the breakaway torque of the aged joint.