bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dihedral rings of patterns emerging from a Turing bifurcation
Authors: Hill Dan J , Bramburger Jason J , Lloyd David J B 
Published: February 2024

Abstract
Collective organisation of patterns into ring-like configurations has been well-studied when patterns are subject to either weak or semi-strong interactions. However, little is known numerically or analytically about their formation when the patterns are strongly interacting. We prove that approximate strongly interacting patterns can emerge in various ring-like dihedral configurations, bifurcating from quiescence near a Turing instability in generic two-component reaction-diffusion systems. The methods used are constructive and provide accurate initial conditions for numerical continuation methods to path-follow these ring-like patterns in parameter space. Our analysis is complemented by numerical investigations that illustrate our findings.
On the anisotropies of the cosmological gravitational-wave background from pulsar timing array observations
Authors: Ding Ran , Tian Chi 
Published: February 2024

Abstract
Significant evidence for a stochastic gravitational-wave background has recently been
reported by several Pulsar Timing Array observations. These studies have shown that, in addition
to astrophysical explanations based on supermassive black hole binaries (SMBHBs), cosmological
origins are considered equally important sources for these signals. To further explore these
cosmological sources, in this study, we discuss the anisotropies in the cosmological gravitational
wave background (CGWB) in a model-independent way. Taking the North American Nanohertz Observatory
for Gravitational Waves (NANOGrav) 15-year dataset as a benchmark, we estimate the angular power
spectra of the CGWB and their cross-correlations with cosmic microwave background (CMB)
fluctuations and weak gravitational lensing. We find that the NANOGrav 15-year data implies
suppressed Sachs-Wolf (SW) effects in the CGBW spectrum, leading to a marginally negative
cross-correlation with the CMB at large scales. This procedure is applicable to signals
introduced by different early universe processes and is potentially useful for identifying unique
features about anisotropies of CGWB from future space-based interferometers and
astrometric measurements.
Model independent dark matter properties from cosmic growth
Authors: Zhumabek Tilek , Denissenya Mikhail , Linder Eric V. 
Published: February 2024

Abstract
Dark matter dominates the matter budget of the universe but its nature is
unknown. Deviations from the standard model, where dark matter clusters with the same
gravitational strength as baryons, and has the same pressureless equation of state as baryons, can
be tested by cosmic growth measurements. We take a model independent approach, allowing deviations
in bins of redshift, and compute the constraints enabled by ongoing cosmic structure surveys
through redshift space distortions and peculiar velocities. These can produce constraints at the
3-14% level in four independent redshift bins over z = [0,4].
Non-thermal WIMPy baryogenesis with primordial black hole
Authors: Choi Ki-Young , Kim Jongkuk , Lkhagvadorj Erdenebulgan 
Published: February 2024

Abstract
We consider the possibility that the weakly interacting massive particles produced from
the evaporation of primordial black hole can explain both the relic density of dark matter and the
baryon asymmetry of the Universe, through their annihilation which violate B and CP-symmetry. We
find that the primordial black hole with mass less than 107g is a good candidate as an
source of TeV dark matter with the total annihilation cross section
〈σaυ〉 ≲ 10-7 GeV-2 and the B-violating scattering cross
section 〈σaυ〉 ≲ 2 × 10-9 GeV-2.
This large annihilation cross section of dark matter in this model would make it available to
search them in the indirect search for dark matter such as gamma-ray or neutrino observations.
Effect of network topologies and attacking strategies on cascading failure model with power-law load redistribution
Authors: Xie Yiran , Wang Tingyu , Yang Bo 
Published: February 2024

Abstract
Various traffic networks play an important role in daily life and have different topological characteristics such as small-world and scale-free. The factors of traffic congestion, natural disasters and traffic accidents may induce cascading failure in which the load redistribution usually has the characteristic of power-law (that is to say, when a station is broken, the great majority of passengers would evacuate to the nearby stations, but the very few would evacuate to further). Based on them, this paper studies the load-capacity cascading failure model with power-law load redistribution using three kinds of attacking strategies (removing a single node according to the load, removing multiple nodes according to the load and removing multiple nodes randomly) for different network structures (random networks, WS small-world networks and BA scale-free networks). We confirm the robustness of our results by further performing simulations on real-world traffic networks. A quantitative description of network topologies and attacking strategies vs. the cascading failure model with power-law load redistribution is obtained by computer simulation. The results demonstrate that in contrast to removing the node according to the load, network robustness increases with the increase of the load control parameter α when randomly removing the node; when θ is small, the load tolerance parameter β is sensitive to the network robustness in random networks and WS small-world networks when removing a single node according to the load.
Characterisation of TCP precipitation sequences of superaustenitic stainless steel and correlation with electrochemical and mechanical properties
Authors: Kountouris N , Makris N , Ioannidou D , Alexandratou A , Deligiannis S , Kaldellis A , Tsakiridis P , Fourlaris G 
Published: February 2024

Abstract
This study investigates the influence of precipitation sequences formed at critical high-temperature range for various ageing time of super austenitic stainless steel 654SMO against the evolution of its corrosive resistance performance through the microstructural characterization, hardness and electrochemical corrosion testing. The specific type of stainless-steel alloy is one of the most corrosion resistant along with exceptional mechanical properties, tailor-made for pressurized and erosive systems handling chlorinated sea water, plate heat exchangers, and fuel gas cleaning applications and an excellent case study of in-depth phase transformations-electrochemical properties characterization phenomena. The microstructure evolution is characterized by scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), hardness testing and potentiodynamic polarization curves. The corresponding precipitation characteristics and sequences of secondary phases are discussed and correlated with electrochemical properties. The results demonstrate σ phase with various morphologies formed during isothermal aging and the formation of three more secondary topologically close pack (TCP) phases, such as chi phase (χ), laves phase (A2B), and Cr2N against corrosive resistance and mechanical performance, which are of primary importance for understanding electrochemical phenomena of different phases and useful for optimizing such alloys for various applications.
Fracture characterization of structural steel S690Q by using mini-CT specimens
Authors: Sánchez M , Cicero S , Arroyo B 
Published: February 2024

Abstract
Mini-CT specimens are an interesting alternative when characterising the fracture behaviour of structural materials and there are issues with regard to, for example, the amount of available material, the irradiation level (in nuclear materials) or material inhomogeneities. Furthermore, in ferritic-pearlitic steels, the characterisation of the fracture behaviour within the ductile-to-brittle transition zone (DBTZ) is of particular interest, given that the material may behave very different, in terms of fracture toughness, when operating at different but relatively close temperatures within this zone. In many occasions, the definition of the DBTZ behaviour is performed through the Master Curve (MC) methodology and, thus, by testing standardised fracture specimens (e.g., CT, SENB) and determining the material Reference Temperature (T0). The use of mini-CT specimens to define T0 has been validated in a wide range of steels used in nuclear industry, but its application to structural steels has been scarce. Thus, this work gathers the fracture characterisation results (T0) obtained in structural steel S690Q, comparing them to those obtained by using conventional standardized SENB specimens. It is shown that, for this particular structural steel, the use of miniaturized specimens provides a T0 value (-89.3°C) which is comparable to the value obtained from conventional larger specimens (-110°C).
3D crack propagation study of a railway component using XFEM method
Authors: Morgado T , Dias R , Pereira M 
Published: February 2024

Abstract
This work develops a methodology to study the crack propagation through ABAQUS simulation. This simulation study uses the service condition of the mechanical component and the complex geometry of a manufacturing defect obtained by microtomography. It was concluded that the XFEM method is an essential tool in predicting crack propagation of a railway component. Furthermore, the type of criteria used in the XFEM method allowed the analysis of the propensity of the manufacturing defect to initiate crack propagation. The C3D4 elements were essential in realising the crack propagation simulation, considering a manufacturing defect. Having the pore’s complex geometry was crucial to developing the methodology presented in this study. The static analysis results indicated that the maximum stress concentration value in the pore is in a zone that can be identified as a hot spot. In addition, the pore showed a higher concentration of Von-Mises stresses than in the static simulation performed without a pore and of the material’s ultimate strength. In conclusion, the methodology presented in this work shows that developing a more realistic simulation study is possible. For a complete structural integrity study, the mechanical design simulation studies must include some complex geometries of intrinsic manufacturing defects.
Chemical recovery of carbon fibers from composites via plasma assisted solvolysis
Authors: Marinis D , Farsari E , Alexandridou C , Amanatides E , Mataras D 
Published: February 2024

Abstract
In this work plasma assisted solvolysis using nitric acid is proposed for chemical recovery of carbon fibers from carbon fiber-reinforced epoxy resin composites (CFRCs). Complete decomposition of the epoxy matrix could be achieved, regardless the composites’ geometry. The efficiency of the process was examined in terms of a) process duration, b) resin decomposition rate and c) materials properties. SEM and EDX data showed that the recovered fiber surfaces are almost free of epoxy resin residuals and their tensile strength was comparable to that of typical virgin carbon fiber. The process decomposition efficiency is very high without requiring additional organic solvents or high temperature / pressure, stressing the potential of this method for viable recycling of CFRCs.
Improved Damage Mapping with Hyperbola Approach for Guided Waves Based Structural Health Monitoring Using Fiber Bragg Grating sensors
Authors: Soman Rohan , Peters Kara , Wandowski Tomasz , Ostachowicz Wieslaw 
Published: February 2024

Abstract
Ultrasonic guided waves (GW) are commonly used in aerospace, civil, and mechanical industries for inspecting the health of a structure non-destructively. Traditionally the piezoelectric based actuators and sensors have been used for the actuation and sensing of GW. But the use of fiber Bragg grating sensors (FBG) is on the increase due to the unique opportunities offered by these sensors. There are several techniques that are used for damage mapping. The most commonly used in reflection based assessment domain are the ellipse based and hyperbola based approaches. Hyperbola approach is based on the time difference of arrival (TDOA). The time difference in the arrival time for two sensors with a common actuator is used for obtaining the hyperbola. The superposition of these hyperbolas for all possible actuator and sensor pairs may be used for damage localization. In this paper a new improved hyperbola approach for damage mapping is proposed by combining it with the ellipse based approach. In order to limit the number of computations a binary variable is introduced to check if the pixel fulfils the hyperbola and ellipse conditions. So only the regions of the structure which fulfil both conditions are mapped. This limits the number of hyperbolas which are identified as possible damage and improves the damage localization. The methodology is employed on a simple aluminium plate with acoustically FBG sensors. The performance of the new approach is compared with existing methods. The results indicate that indeed the improved hyperbola approach improves the localization. Also the computational load is reduced allowing more real time damage mapping.
A vibration-based Machine Learning type Structural Health Monitoring methodology for populations of composite aerostructures under uncertainty
Authors: Saramantas I E , Spiliotopoulos P E , Fera F T , Bourdalos D M , Sakellariou J S , Fassois S D , Ofir Y , Kressel I , Tur M , Spandonidis C 
Published: February 2024

Abstract
A robust to uncertainty Machine Learning (ML) based Structural Health Monitoring methodology for populations of composite aerostructures is postulated. The methodology is founded upon a number of unsupervised ML algorithms for damage detection and a supervised counterpart for damage characterization. Damage detection is specifically based on two types of Healthy Subspace representations: A Multiple Model (MM) and a varying radii Hyper-Sphere (HS) type. Both are built upon response-only vibration acceleration and/or strain signals at properly selected sensor locations. Based on them, Multiple Input Single Output (MISO) Transmittance Function AutoRegressive with eXogenous (TF-ARX) excitation data driven models representing the partial structural dynamics are obtained. Decision making is then based on the model parameter vector that may be transformed and reduced via Principal Component Analysis (PCA). Damage detection is achieved via multi-level information fusion using acceleration and/or strain sensors. Damage characterization, referring to damage type, location, and level determination, is achieved via a hierarchical cosine similarity based algorithm. The methodology is successfully assessed via hundreds of experiments using a population of small-scale composite coupons for the detection and characterization of Delamination and Impact damage under material/manufacturing, temperature, excitation, and experimental uncertainty.
A Novel, Non-Contact NDT Scanner Case Study: Thickness Measurement, Debonding and Defects Detection in Metallic and Composite Parts
Authors: Volker Arno , Stamoulis Konstantinos P , Schoemaker Christiaan , Apostolidis Asteris , Tongeren Donald van , Poppe Robert , Bekkema Bart , Martina Quincy 
Published: February 2024

Abstract
The NDT methods currently used in aviation MRO are predominantly labour-intensive and time-consuming processes performed by human operators throughout the lifespan of an aircraft. These techniques are time-consuming, require perpetual training and are highly dependent on the operator’s skills. Thus, there is a growing need for more efficient, automated, and accurate NDT tools that will be able to provide faster and less labour-intensive assessments. This study presents a novel, non-contact, automated NDT scanning system under development, which aims to reduce the inspection time significantly. The proposed technique uses a non-contact, Lamb wave-based approach. A further essential step during the process is to use an automated positioning system. Thickness mapping and defect detection in metal and composite structures have been performed. A local thickness map in the order of 1 mm has been obtained through a fast-scanning process with comparable resolution to conventional inspection techniques. Overall, it is currently concluded that the proposed NDT scanner is a promising tool that potentially can reduce the inspection time while also having the potential to automate the damage assessment resulting in more efficient MRO inspection processes.
A probabilistic fatigue model based on nonlinear Kohout-Věchet function: Application to 42CrMo4+QT steel
Authors: Marques J M E , Papuga J , Růžička M , Benasciutti D 
Published: February 2024

Abstract
This paper presents a fatigue model designed to provide probabilistic-stress-life (P-S-N) curves at any probability level. Grounded in the Weibull probabilistic model’s framework, the model describes two scenarios: P-Case A, which considers deviations in stress, and P-Case B, centered on deviations in cycles to failure from the median S-N curve. A significant aspect of the proposed model is the incorporation of the Kohout-Věchet function as the representative median S-N curve, allowing for the Kohout-Vechet P-S-N curves across any probability level. To demonstrate the model’s practical relevance, an experimental example focused on specimens made from 42CrMo4+QT steel and subjected to push-pull loading is explored. Not only do the results show the robustness of the model but they also emphasize the role of the characteristic P-S-N curves, especially at lower probability level, in assuring the safety of engineering components.
Structured Method to Reconfigure the Fatigue of Mechanical Products such as HKS in a Refrigerator
Authors: Woo Seong-woo , O’Neal Dennis L. , Hassen Yimer Mohammed , Mebrahtu Gezae 
Published: February 2024

Abstract
To determine the fatigue lifetime of a system such as a car, refrigerator, etc., parametric Accelerated Life Testing (ALT) can be used as an arranged way to find out its reliability and failure mechanisms a when it is subjected to continual loads The process includes: (1) parametric ALT used to establish the BX life, (2) load evaluation for designing an accelerated life test(s), (3) a tailored representative of ALTs with design adjustments, and (4) an appraisal of whether system gets to the goal for the BX lifetime. A generalized life-stress failure approach with an accelerated factor, and sample size formulation are proposed. An organized reliability approach, such as parametric ALT, can help the designer to find product defects having an effect on reliability as computed by the improvement in life, LB, and the decreasing in failure rate, λ in the design stage. As a consequence, manufacturers can stop recalls from failures of their products when introduced into the marketplace. A hinge kit system (HKS) in a domestic refrigerator that needed to be redesigned was provided as an example. After a tailored set of parameter ALTs, the HKS with design changes were expected to realize the life aim – B1 life ten years.
Buckling Prediction of MWCNT-reinforced Laminated Composite Structures under Hygro-Thermo-Mechanical Conditions
Authors: Georgantzinos Stelios K. , Antoniou Panagiotis A. , Stamoulis Konstantinos P. , Spitas Christos 
Published: February 2024

Abstract
This study presents a detailed buckling analysis of laminated composites reinforced by multi-walled carbon nanotube (MWCNT) inclusions using a multiscale computational framework. It combines multiple analytical and computational techniques to assess the performance of these composites under varying hygro-thermo-mechanical conditions. The model incorporates nanoscopic MWCNT characteristics, estimates orthotropic constants, and investigates the impact of various factors on the critical buckling load of MWCNT-based laminates. Comparison with existing data validates our approach, marking the first usage of the multiscale finite element method for predicting the buckling behaviour of MWCNT-reinforced laminates. This research offers valuable design insights for various industries including aerospace and automotive.
Tensile properties of 3D printed INCONEL 718 cellular specimens
Authors: Monkova K , Pantazopoulos G A , Monka P P , Toulfatzis A I , Lengyelova K , Papadopoulou S 
Published: February 2024

Abstract
The aim of the presented research by the authors was to compare the behaviour of four types of cellular structures under quasi-static tensile stress, while two samples were formed by mono-structures Gyroid 10 % and Diamond 10 %, and the other two types were bi-structures, which were created by combining two single structures (Gyroid 5 % + Gyroid 5 %) and (Gyroid 5 % + Diamond 5 %). The samples were made of Inconel 718 by Direct Metal Laser Sintering technology on an EOS EOSINT M270 machine, and they were heat treated according to AMS 5664 procedure. Tensile tests were performed on an Instron 8802 servo-hydraulic testing machine with a maximum capacity of 250 kN at ambient temperature. The results showed that the maximum load corresponded to the diamond (D) cellular structure (approximately 48 kN), while the minimum load was observed for the gyroid-gyroid (GG) structure (approximately 32 kN).
Fatigue performance of hierarchically porous titanium scaffolds produced by additive manufacturing and its possible improvement by gas nitriding
Authors: Slámečka K , Kashimbetova A , Tkachenko S , Gejdoš P , Pokluda J , Montufar E B , Čelko L 
Published: February 2024

Abstract
This contribution focuses on the nitriding of hierarchically porous titanium scaffolds to enhance their fatigue behaviour. Firstly, recent experimental findings that demonstrate the benefits of intra-filament porosity in improving fatigue resistance are discussed, providing details on crack growth shielding micromechanisms. Subsequently, the study explores the application of titanium scaffolds nitriding as a promising technique to prolong fatigue crack initiation. The scaffolds, prepared using the direct ink writing method with intra-filament porosity of ~ 6% and inter-filament porosity of ~ 68%, underwent gas nitriding at 1100 °C for 2 h. This process resulted in the formation of a consistent 42 μm thick nitriding case across the entire structure. Preliminary experiments showed a minimal decrease in fatigue strength within the low cycle fatigue region, attributed to the fracturing of a thick brittle compound zone under high applied loading. These results suggest that nitriding has the potential to improve fatigue performance after process optimization.
Experimental and statistical investigation on flexural properties of FDM fabricated PLA specimens applying response surface methodology
Authors: Fountas Nikolaos A. , Papantoniou Ioannis , Kechagias John D. , Manolakos Dimitrios E. , Vaxevanidis Nikolaos M. 
Published: February 2024

Abstract
Additive manufacturing (AM) is a modern technology currently adopted by manufacturing industries to benefit from its low-cost applications, versatility and fabrication of complex parts. Fused deposition modeling (FDM) is distinguished among the different AM technologies due to its fast, yet accurate operations. However the properties of fabricated components are strongly depended by FDM-related parameter settings. This work examines the effect of FDM-related parameters namely flow rate, printing speed and printing temperature on the response of flexural strength. Experiments according to L9 orthogonal array and a custom response surface experimental design were performed to obtain the results necessary for further examination and analysis corresponding to parameter effects on flexural strength and statistical outputs. Experiments were designed as per the ASTM D790 standard whilst failure modes of experimental samples were observed for correlating the independent printing parameters with the response of flexural strength. The full quadratic regression model generated for predicting results concerning flexural strength was found adequate for explaining the variation of FDM-related parameters on flexural strength response.