Engineering topics
Publications and source records attributed to Ferencz, R. M..
The review was conducted on May 9-10, 2016 at the University of Utah. Overall the review team was impressed with the work presented and found that the CCMSC had met or exceeded the Year 2 milestones. Specific details, comments and recommendations are included in this document.
Here, with the technology being developed to manufacture metallic parts using increasingly advanced additive manufacturing processes, a new era has opened up for designing novel structural materials, from designing shapes and complex geometries to controlling the microstructure (alloy composition and morphology). The material properties used within specific structural components are also designable in order to meet specific performance requirements that are not imaginable with traditional metal forming and machining (subtractive) techniques.
Selective laser melting (SLM) is an additive manufacturing process in which multiple, successive layers of metal powders are heated via laser in order to build a part. Modeling of SLM requires consideration of the complex interaction between heat transfer and solid mechanics. Here, the present work describes the authors initial efforts to validate their first generation model. In particular, the comparison of model-generated solid mechanics results, including both deformation and stresses, is presented. Additionally, results of various perturbations of the process parameters and modeling strategies are discussed.
The production of metal parts via laser powder bed fusion additive manufacturing is growing exponentially. However, the transition of this technology from production of prototypes to production of critical parts is hindered by a lack of confidence in the quality of the part. Confidence can be established via a fundamental understanding of the physics of the process. It is generally accepted that this understanding will be increasingly achieved through modeling and simulation. However, there are significant physics, computational, and materials challenges stemming from the broad range of length and time scales and temperature ranges associated with the process. In this study, we review the current state of the art and describe the challenges that need to be met to achieve the desired fundamental understanding of the physics of the process.
The review was conducted on March 31 – April 1, 2015 at the University of Utah. Overall the review team was impressed with the work presented and found that the CCMSC had met or exceeded all of their Year 1 milestones. Specific details, comments and recommendations are included in this document.
The metal laser powder bed fusion additive manufacturing process uses high power lasers to build parts layer upon layer by melting fine metal powders. Qualification of parts produced using this technology is broadly recognised as a significant challenge. Physics based process models have been identified as being foundational to qualification of additively manufactured metal parts. In the present article, a multiscale modelling strategy is described that will serve as the foundation upon which process control and part qualification can be built. This includes a model at the scale of the powder that simulates single track/single multilayer builds and provides powder bed and melt pool thermal data. A second model computationally builds a complete part and predicts manufactured properties (residual stress, dimensional accuracy) in three dimensions. Finally, modelling is tied to experiment through data mining.
Selective laser melting (SLM) is an additive manufacturing process in which multiple, successive layers of metal powders are heated via laser in order to build a part. Modeling of SLM requires consideration of both heat transfer and solid mechanics. The present work describes continuum modeling of SLM as envisioned for eventual support of part-scale modeling of this fabrication process to determine end-state information such as residual stresses and distortion. The determination of the evolving temperatures is dependent on the material, the state of the material (powder or solid), the specified heating, and the configuration. Similarly, the current configuration is dependent on the temperatures, the powder-solid state, and the constitutive models. A multi-physics numerical formulation is required to solve such problems. This article describes the problem formulation, numerical method, and constitutive parameters necessary to solve such a problem. Additionally, various verification and example problems are simulated in the parallel, multi-physics finite element code Diablo, and the results presented herein.
The Diablo code being developed at Lawrence Livermore National Laboratory (LLNL) uses implicit, Lagrangian finite element methods for the simulation of solid mechanics and multi-physics events over moderate to long time frames. A recent effort examined technologies needed to extend Diablo for use in seismic response incorporating soil-structure interaction (SSI). Our SSI study was intended to illustrate how advanced time-domain simulation approaches compare with and complement the standard frequency-domain approach for SSI.
The NEAMS project aims to develop a simulation toolkit, the "NEAMS ToolKit," which will enable predictive virtual test and experiments. The NEAMS toolkit will generate insights by exploring reactor system behavior in regimes that are too difficult, too risky, or even impossible to achieve exclusively in a laboratory setting. The objective of the NEAMS toolkit is to develop a "pellet-to-plant" simulation capability useful for predicting performance and safety for a broad range of nuclear reactor power systems.
Modeling of selective laser melting requires consideration of both heat transfer and solid mechanics. The present work describes continuum modeling of SLM as envisioned for eventually supporting part-scale modeling of this fabrication process to determine end-state information such as residual stress and distortion. The determination of the evolving temperatures is dependent on the state of the material (powder or solid), the specified heating, the value of each of the constitutive parameters, and the configuration. Similarly, the current mechanical configuration is dependent on the temperatures, the powder-solid state, and the values of the constitutive parameters. A multi-mechanics formulation is required to properly describe such problems. The current report describes the problem formulation, numerical method, and constitutive parameters necessary to solve such a problem. Additionally, various verification and example problems are presented to illustrate the Diablo implementation.
The authors briefly summarize the development of, and test experience with, an initial data interface between the structural mechanics code Diablo and the SHARP reactor simulation system data hub MOAB. That interface has been exercised both to write MOAB databases from Diablo, and then also to use such a database to read in part of a simulation definition for a subsequent Diablo execution. All enhancements are integrated into the central Diablo source repository. The SHARP software system for advanced simulation of nuclear reactors and power plant systems is sponsored by DOE's Nuclear Energy Advanced Modeling and Simulation (NEAMS) program. SHARP has been architected as a federation of single-physics simulation tools to permit flexibility in programming languages and leveraging of past and on-going investments. Solution of multi-physics problems will be coordinated by, and data passed through, a central 'hub'. SHARP's hub implementation is utilizing MOAB: a Mesh-Oriented datABase. This same data hub approach is also intended to enable multi-resolution simulations, e.g, lower-dimension plant-scale simulations can be informed by high-fidelity 3D models of particular critical components.