On the Effects of Modeling As-Manufactured Geometry: Toward Digital Twin

Asimple, nonstandardized material test specimen,which fails along one of two different likely crack paths, is considered herein.The result of deviations in geometry on the order of tenths of amillimeter, this ambiguity in crack pathmotivates the consideration of asmanufactured component geometry in the design, assessment, and certification of structural systems.Herein, finite elementmodels of as-manufactured specimens are generated and subsequently analyzed to resolve the crack-path ambiguity. The consequence and benefit of such a "personalized" methodology is the prediction of a crack path for each specimen based on its as-manufactured geometry, rather than a distribution of possible specimen geometries or nominal geometry.The consideration of as-manufactured characteristics is central to the Digital Twin concept. Therefore, this work is also intended to motivate its development

On the Effects of Modeling As-Manufactured Geometry: Toward Digital Twin

A simple, nonstandardized material test specimen, which fails along one of two different likely crack paths, is considered herein. The result of deviations in geometry on the order of tenths of a millimeter, this ambiguity in crack path motivates the consideration of as-manufactured component geometry in the design, assessment, and certification of structural systems. Herein, finite element models of as-manufactured specimens are generated and subsequently analyzed to resolve the crack-path ambiguity. The consequence and benefit of such a “personalized” methodology is the prediction of a crack path for each specimen based on its as-manufactured geometry, rather than a distribution of possible specimen geometries or nominal geometry. The consideration of as-manufactured characteristics is central to the Digital Twin concept. Therefore, this work is also intended to motivate its development

On key technologies for realising digital twins for structural dynamics applications

The term digital twin has gained increasing popularity over the last few years. The concept, loosely based on a virtual model framework that can replicate a particular system for contexts of interest over time, will require the development and integration of several key technologies in order to be fully realised. This paper, focusing on vibration-related problems in mechanical systems, discusses these key technologies as the building blocks of a digital twin. The example of a simulation digital twin that can be used for asset management is then considered. After briefly discussing the building blocks required, the process of data-augmented modelling is selected for detailed investigation. This concept is one of the defining characteristics of the digital twin idea, and using a simple numerical example, it is shown how augmenting a model with data can be used to compensate for the inherent model discrepancy. Finally the implications of this type of data augmentation for future digital twin technology is discussed

Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

Investigation Of Multiscale Damage Initiation And Propagation Capabilities

Fracture is largely a microstructure-based phenomenon, but for experimentalists, computational mechanicians, and fleet managers operating at the macroscale, this fact might seem inexplicable, inapplicable, or even inconsequential. The latter response is what the three chapters of this dissertation address. Together, they attempt to dispel the notion that microstructural effects do not translate in any useful way to the structural scale. They also present models which are verified and validated herein to ease this disconnect. These three chapters are individual papers submitted to refereed journals for publication. The paper in the first chapter appears in Engineering Fracture Mechanics (DOI: http://dx.doi.org/10.1016/j.engfracmech.2014.03.010). It generalizes the Park-PaulinoRoesler potential-based cohesive zone model to three-dimensions, a means to model fracture even under a high degree of mode-mixity at both the macro- and micro-scales. The generalization is validated against several material tests at the macroscale: T-Peel, MMB, ECT, and BDWT. Its ability to model intergranular fracture at the microscale is also explored. The paper in the second chapter fills a void in the Digital Twin community- it presents for the first time a straight-forward use case which both clarifies and motivates this new paradigm in fleet management. Specifically, ductile fracture is modeled in a non-standardized specimen which fails along one of two likely crack paths. This crack path ambiguity, the result of grain-size deviations in specimen geometry, underpins the importance of considering as-manufactured component geometry in the design, assessment, and certification of structural systems, a cornerstone of Digital Twin. It also highlights the limitations of a continuum plasticity damage model in resolving accurately this ambiguity particularly close to the bifurcation, on the order of a few grain sizes, and motivates the need to consider crack nucleation at the microscale. The paper in the third chapter demonstrates Digital Twin at the microscale. It details the implementation, verification, and validation of a microstructure-based, Digital Twin framework which accounts for the predominant microcrack nucleation mechanism in the nickel-based superalloy LSHR. Also included is an extensive grain boundary analysis, an investigation that would otherwise be impossible to conduct to any appreciable fidelity without the as-processed, Digital Twin microstructural model

Fatigue crack initiation, slip localization and twin boundaries in a nickel-based superalloy

The study of fatigue in metals, and fatigue initiation specifically, lends itself to analysis via an emerging set of characterization and modeling tools that describe polycrystals on the meso- or microstructural length scale. These include three-dimensional characterization techniques, elastic anisotropic and visco-plastic stress models, new approaches to the statistical description of stress and strain distributions, synthetic microstructure modeling, and improved tools for manipulating the large datasets generated. A specific example of analysis in both 2D and 3D of fatigue cracks in a nickel-based superalloy is given where all the cracks are effectively coincident with coherent twin boundaries. A spectral method is used to analyze the stress state based on a fully anisotropic elastic calculation. The results indicate that, although a high resolved shear stress is associated with the locations of the observed cracks, the length of the trace of the twin boundary is more strongly correlated with crack formation.close0