@article{WiesentStockerNonn, author = {Wiesent, Lisa and Stocker, Felix and Nonn, Aida}, title = {Investigating the influence of geometric parameters on the deformation of laser powder bed fused stents using low-fidelity thermo-mechanical analysis}, series = {Materialia}, volume = {28}, journal = {Materialia}, publisher = {Elsevier}, doi = {10.1016/j.mtla.2023.101774}, abstract = {Maintaining dimensional accuracy is a major challenge of laser powder bed fusion (L-PBF) preventing its application for more complex and filigree L-PBF structures in industrial practice. Previous studies have shown that residual stresses and distortion of benchmark L-PBF components may be predicted by sequential thermo-mechanical analyses. However, the reliability of these analyses for more complex structures must be critically questioned, as comprehensive validation and sensitivity analyses are scarce. In this paper, we present a calibrated and validated low-fidelity sequential thermo-mechanical finite element analysis (FEA) of a tubular L-PBF lattice structure, i.e., an aortic stent, where pronounced local deformation is expected. As a first step, the finite element model was extensively calibrated using experimental data to ensure reproducibility of the simulation results. Thereupon, geometric features critical to the distortion of L-PBF lattice structures and measures to compensate for the distortion, such as inversion of the distorted L-PBF structure, were investigated. It was found that the distortion of the L-PBF lattice structures can be reduced, but not completely prevented, by increasing the strut angles, increasing the strut thickness, and decreasing the transition radius in the area of merging struts. FEA-based inversion of the numerically predicted deformed structure minimized distortion, resulting in the L-PBF aortic stent approximating the intended CAD geometry even with a small strut thickness. This work shows that low-fidelity sequential thermo-mechanical FEA can be used not only for the analysis and deformation compensation of reference structures, but also for the analysis of more complex filigree structures with pronounced local deformation.}, language = {en} } @article{NonnKissPezeshkianetal., author = {Nonn, Aida and Kiss, B{\´a}lint and Pezeshkian, Weria and Tancogne-Dejean, Thomas and Cerrone, Albert R. and Kellermayer, Miklos and Bai, Yuanli and Li, Wei and Wierzbicki, Tomasz}, title = {Inferring mechanical properties of the SARS-CoV-2 virus particle with nano-indentation tests and numerical simulations}, series = {Journal of the mechanical behavior of biomedical materials}, volume = {148}, journal = {Journal of the mechanical behavior of biomedical materials}, publisher = {Elsevier}, issn = {1751-6161}, doi = {10.1016/j.jmbbm.2023.106153}, abstract = {The pandemic caused by the SARS-CoV-2 virus has claimed more than 6.5 million lives worldwide. This global challenge has led to accelerated development of highly effective vaccines tied to their ability to elicit a sustained immune response. While numerous studies have focused primarily on the spike (S) protein, less is known about the interior of the virus. Here we propose a methodology that combines several experimental and simulation techniques to elucidate the internal structure and mechanical properties of the SARS-CoV-2 virus. The mechanical response of the virus was analyzed by nanoindentation tests using a novel flat indenter and evaluated in comparison to a conventional sharp tip indentation. The elastic properties of the viral membrane were estimated by analytical solutions, molecular dynamics (MD) simulations on a membrane patch and by a 3D Finite Element (FE)-beam model of the virion's spike protein and membrane molecular structure. The FE-based inverse engineering approach provided a reasonable reproduction of the mechanical response of the virus from the sharp tip indentation and was successfully verified against the flat tip indentation results. The elastic modulus of the viral membrane was estimated in the range of 7-20 MPa. MD simulations showed that the presence of proteins significantly reduces the fracture strength of the membrane patch. However, FE simulations revealed an overall high fracture strength of the virus, with a mechanical behavior similar to the highly ductile behavior of engineering metallic materials. The failure mechanics of the membrane during sharp tip indentation includes progressive damage combined with localized collapse of the membrane due to severe bending. Furthermore, the results support the hypothesis of a close association of the long membrane proteins (M) with membrane-bound hexagonally packed ribonucleoproteins (RNPs). Beyond improved understanding of coronavirus structure, the present findings offer a knowledge base for the development of novel prevention and treatment methods that are independent of the immune system.}, language = {en} } @article{CerroneNonnHochhalteretal., author = {Cerrone, Albert R. and Nonn, Aida and Hochhalter, Jacob D. and Bomarito, Geoffrey F. and Warner, J. E. and Carter, Bruce J.}, title = {Predicting failure of the Second Sandia Fracture Challenge geometry with a real-world, time constrained, over-the-counter methodology}, series = {International Journal of Fracture}, volume = {198}, journal = {International Journal of Fracture}, number = {1-2}, doi = {10.1007/s10704-016-0086-x}, pages = {117 -- 126}, abstract = {An over-the-counter methodology to predict fracture initiation and propagation in the challenge specimen of the Second Sandia Fracture Challenge is detailed herein. This pragmatic approach mimics that of an engineer subjected to real-world time constraints and unquantified uncertainty. First, during the blind prediction phase of the challenge, flow and failure locus curves were calibrated for Ti-6Al-4V with provided tensile and shear test data for slow (0.0254 mm/s) and fast (25.4 mm/s) loading rates. Thereafter, these models were applied to a 3D finite-element mesh of the non-standardized challenge geometry with nominal dimensions to predict, among other items, crack path and specimen response. After the blind predictions were submitted to Sandia National Labs, they were improved upon by addressing anisotropic yielding, damage initiation under shear dominance, and boundary condition selection.}, language = {en} } @article{CerroneWawrzynekNonnetal., author = {Cerrone, Albert R. and Wawrzynek, Paul and Nonn, Aida and Paulino, Glaucio H. and Ingraffea, Anthony R.}, title = {Implementation and verification of the Park-Paulino-Roesler cohesive zone model in 3D}, series = {Engineering Fracture Mechanics}, volume = {120}, journal = {Engineering Fracture Mechanics}, doi = {10.1016/j.engfracmech.2014.03.010}, pages = {26 -- 42}, abstract = {The Park-Paulino-Roesler (PPR) potential-based model is a cohesive constitutive model formulated to be consistent under a high degree of mode-mixity. Herein, the PPR's generalization to three-dimensions is detailed, its implementation in a finite element framework is discussed, and its use in single-core and high performance computing (HPC) applications is demonstrated. The PPR model is shown to be an effective constitutive model to account for crack nucleation and propagation in a variety of applications including adhesives, composites, linepipe steel, and microstructures.}, language = {en} } @article{XueKeimParedesetal., author = {Xue, Lufeng and Keim, Vincent and Paredes, Marcelo and Nonn, Aida and Wierzbicki, Tomasz}, title = {Anisotropic effects on crack propagation in pressurized line pipes under running ductile fracture scenarios}, series = {Engineering fracture mechanics}, volume = {249}, journal = {Engineering fracture mechanics}, publisher = {Elsevier}, doi = {10.1016/j.engfracmech.2021.107748}, abstract = {The current analyses present results of running ductile fracture propagation in high strength X100 line pipe steels under the influence of anisotropy. Mechanical anisotropy is commonly available in pipe products as a result of the manufacturing process, especially, those subjected to hot/cold-worked deformation. The outcomes of the present analyses show that its effect on the behavior of running ductile fracture in cracked pipes undergoing depressurization is meaningful. For instance, the Crack-Tip Opening Angle (CTOA) not only exhibits a strong dependence to the pipe's diameter size, but also to the material's anisotropy nature when compared to a hypothetical isotropic material. Moreover, laboratory scale tests such as those performed on Battelle Drop Weight Tear (BDWT) samples provide useful information about initiation of ductile crack propagation when the anisotropy features are taken into account in the material description.}, language = {en} } @inproceedings{NonnMarx, author = {Nonn, Aida and Marx, P.}, title = {Validated Multiphysics Modeling For Advanced Pipeline Integrity Management}, series = {ADIPEC, November 4-7, 2024, Abu Dhabi, UAE}, booktitle = {ADIPEC, November 4-7, 2024, Abu Dhabi, UAE}, organization = {Society of Petroleum Engineers}, doi = {10.2118/222279-MS}, abstract = {The aim of this paper is to present practical steps for utilizing a validated multiphysics approach for fracture control in CO2 pipelines within the framework of Carbon Capture Transport and Storage (CCTS). Ensuring the arrest of running ductile fracture (RDF) is a crucial safety requirement for the transportation of dense-phase CO2. However, current standards rely on outdated and restrictive methods, imposing severe limitations on pipeline material and structural design. As a result, projects that fall outside these standards face the need for extremely costly tests, often leading to delays or cancellations of CCTS initiatives. This study introduces an advanced, validated, fully-coupled fluid-structure interaction (FSI) model designed to accurately predict fracture propagation in CO2 pipelines. A key advantage of this approach is its use of robust and reproducible calibration and validation procedures combined with high-quality material characterization data. The full coupling of structural, fluid, and backfill models is essential for obtaining precise results, not only in determining arrest occurrence but also in analyzing properties such as fracture velocity history, 3D pressure distributions behind the propagating crack, wall thinning, and crack tip opening angle. The FSI model has demonstrated its value as a cost-effective tool for safety assessments, enabling the development of fracture control plans that specify minimum required material properties and fluid compositions for optimized pipeline design, both onshore and offshore. Additionally, performing virtual studies with the parameterized FSI model enables the generation of synthetic data for training and validating a machine learning surrogate model. This surrogate model can be integrated into industrial practices, facilitating the application of multiphysics modeling without the need for extensive expertise.}, language = {en} } @article{QiaoGradNonn, author = {Qiao, Yu and Grad, Marius and Nonn, Aida}, title = {Toward an Efficient and Robust Process-Structure Prediction Framework for Filigree L-PBF 316L Stainless Steel Structures}, series = {Metals}, volume = {15}, journal = {Metals}, number = {7}, publisher = {MDPI}, issn = {2075-4701}, doi = {10.3390/met15070812}, pages = {22}, abstract = {Additive manufacturing (AM), particularly laser powder bed fusion (L-PBF), provides unmatched design flexibility for creating intricate steel structures with minimal post-processing. However, adopting L-PBF for high-performance applications is difficult due to the challenge of predicting microstructure evolution. This is because the process is sensitive to many parameters and has a complex thermal history. Thin-walled geometries present an added challenge because their dimensions often approach the scale of individual grains. Thus, microstructure becomes a critical factor in the overall integrity of the component. This study focuses on applying cellular automata (CA) modeling to establish robust and efficient process-structure relationships in L-PBF of 316L stainless steel. The CA framework simulates solidification-driven grain evolution and texture development across various processing conditions. Model predictions are evaluated against experimental electron backscatter diffraction (EBSD) data, with additional quantitative comparisons based on texture and morphology metrics. The results demonstrate that CA simulations calibrated with relevant process parameters can effectively reproduce key microstructural features, including grain size distributions, aspect ratios, and texture components, observed in thin-walled L-PBF structures. This work highlights the strengths and limitations of CA-based modeling and supports its role in reliably designing and optimizing complex L-PBF components.}, language = {en} }