Jerome Solberg
Lawrence Livermore National Lab, Engineering, Department Member
- Computational Fluid Dynamics, Numerical Analysis, Computational Physics, Plasma Physics, Magnetohydrodynamics, Solid Mechanics, and 6 moreContact Mechanics, Thermal Engineering, Pulsed Power, Multiphysics Simulation, Seismic Engineering, and Nuclear Energy(Contact Mechanics, Thermal Engineering, Pulsed Power, Multiphysics Simulation, Seismic Engineering, and Nuclear Energy)edit
Abstract Scan pattern dependent (multi-track) residual stress buildup over multiple layers in the powder bed fusion process is governed by coupled thermo-mechanics. The high computational cost associated with these simulations has... more
Abstract Scan pattern dependent (multi-track) residual stress buildup over multiple layers in the powder bed fusion process is governed by coupled thermo-mechanics. The high computational cost associated with these simulations has resulted in the general adoption of approximate computational methods. The numerical or thermo-mechanical accuracy of assumptions made in these computational methods is not fully characterized. If benchmark multi-track simulations for small size multi-layer parts are available, including temperatures, strain fields and deformation results, it will be possible to scientifically develop new approximation schemes or modify existing ones to improve their accuracy. Present work develops a suggestive benchmark using full multi-track thermomechanical simulations, with comparison to various approximate methods. The target configurations are simple prismatic geometries with 30 layers and up to 120 mm3 volume, illustrating the influence of domain size on the approximate results. Anticipating the future challenges of measuring stresses and deformation in these small benchmark geometries, an experimental setup based on sheet metal forming principals is demonstrated numerically. The proposed setup will provide a methodology to experimentally validate these benchmarks.
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Fluid-structure interactions are complex, multi-physics phenomena of consequence for many fluid-flow domains. Modern multi-physics codes are becoming capable of simulating with great accuracy the interaction between fluid and structure... more
Fluid-structure interactions are complex, multi-physics phenomena of consequence for many fluid-flow domains. Modern multi-physics codes are becoming capable of simulating with great accuracy the interaction between fluid and structure dynamics. While fluid-structure interactions can occur in many forms, flow-induced vibrations are of particular interest. Such vibrations can result in the fatigue and even failure of a vibrating geometry. The prediction and minimization of flow induced vibrations are of particular importance for heat exchangers, which commonly contain bundles of tubes experiencing high-velocity crossflow. The present study simulates the fluid-structure interaction for flexibly mounted tube bundles undergoing crossflow and compares the results with experiment. The simulation code consists of a spectral-element fluid solver directly coupled with a finite-element solid mechanics solver. The fluid solver locally adapts the fluid mesh to accommodate the moving solids. In ...
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In nuclear reactors that use plate-type fuel, the fuel plates are thermally managed with coolant flowing through channels between the plates. Depending on the flow rates and sizes of the fluid channels, the hydraulic forces exerted on a... more
In nuclear reactors that use plate-type fuel, the fuel plates are thermally managed with coolant flowing through channels between the plates. Depending on the flow rates and sizes of the fluid channels, the hydraulic forces exerted on a plate can be quite large. Currently, there is a worldwide effort to convert research reactors that use highly enriched uranium (HEU) fuel, some of which are plate-type, to low-enriched uranium (LEU). Because of the proposed changes to the fuel structure and thickness, a need exists to characterize the potential for flow-induced deflection of the LEU fuel plates. In this study, as an initial step, calculations of Fluid-Structure Interaction (FSI) for a flat aluminum plate separating two parallel rectangular channels are performed using the commercial code STAR-CCM+ and the integrated multi-physics code SHARP, developed under the Nuclear Energy Advanced Modeling and Simulation program. SHARP contains the high-fidelity single physics packages Diablo and...
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... Reservoir. The reservoir extends approximately 19 km (12 miles) upstream. The dam structure is 143 m (468 ft) high with a crest length of 221 m (724 ft). ... model): 1.Westergaard added mass for fluid-structure interaction [Ref 7] ...
Coupled multi-mechanics simulations (such as thermal-stress and fluidstructure interaction problems) are of substantial interest to engineering analysts. In addition, adaptive mesh refinement techniques present an attractive alternative... more
Coupled multi-mechanics simulations (such as thermal-stress and fluidstructure interaction problems) are of substantial interest to engineering analysts. In addition, adaptive mesh refinement techniques present an attractive alternative to current mesh generation procedures and provide quantitative error bounds that can be used for model verification. This paper discusses spatially adaptive multi-mechanics implicit simulations using the Diablo computer code. (U)
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ABSTRACT 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... more
ABSTRACT 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.
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ABSTRACT This article advocates a general procedure for the numerical investigation of pseudo-rigid bodies. The equations of motion for pseudo-rigid bodies are shown to be mathematically equivalent to those corresponding to certain... more
ABSTRACT This article advocates a general procedure for the numerical investigation of pseudo-rigid bodies. The equations of motion for pseudo-rigid bodies are shown to be mathematically equivalent to those corresponding to certain constant-strain finite element approximations for general deformable continua. A straightforward algorithmic implementation is achieved in a classical finite element framework. Also, a penalty formulation is suggested for modelling contact between pseudo-rigid bodies. Representative planar simulations using a non-linear elastic model demonstrate the predictive capacity of the pseudo-rigid theory, as well as the robustness of the proposed computational procedure. Copyright © 1999 John Wiley & Sons, Ltd.
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Research Interests: Applied Mathematics, Kinetics, Finite element method, Contact Mechanics, Finite Element, and 8 moreMulti Domain, Lagrange multipliers, Mathematical and Computer Modelling, Numerical Analysis and Computational Mathematics, Boolean Satisfiability, Lagrange Multiplier, Contact Problem, and Pressure Distribution
ABSTRACT This paper deals with the impact behavior of elastic pseudo-rigid bodies. It is shown that in the case of a spherically symmetric, linearly elastic pseudo-rigid body impacting on a rigid foundation, energy conservation... more
ABSTRACT This paper deals with the impact behavior of elastic pseudo-rigid bodies. It is shown that in the case of a spherically symmetric, linearly elastic pseudo-rigid body impacting on a rigid foundation, energy conservation necessitates the existence of multiple impact events. A comparison is made with the dynamic Hertzian theory in terms of the coefficient of restitution and the duration of impact. In addition, the chaotic nature of the long-term dynamics of this system is explored qualitatively.
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This article advocates a new methodology for the finite element solution of contact problems involving bodies that may undergo finite motions and deformations. The analysis is based on a decomposition of the two-body contact problem into... more
This article advocates a new methodology for the finite element solution of contact problems involving bodies that may undergo finite motions and deformations. The analysis is based on a decomposition of the two-body contact problem into two simultaneous sub-problems, and results naturally in geometrically unbiased discretization of the contacting surfaces. A proposed two-dimensional contact element is specifically designed to unconditionally allow for exact transmission of constant normal traction through interacting surfaces.
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A stabilized, nodally integrated linear tetrahedral is formulated and analysed. It is well known that linear tetrahedral elements perform poorly in problems with plasticity, nearly incompressible materials, and acute bending. For a... more
A stabilized, nodally integrated linear tetrahedral is formulated and analysed. It is well known that linear tetrahedral elements perform poorly in problems with plasticity, nearly incompressible materials, and acute bending. For a variety of reasons, low-order tetrahedral elements are preferable to quadratic tetrahedral elements; particularly for nonlinear problems. But the severe locking problems of tetrahedrals have forced analysts to employ hexahedral formulations for most nonlinear problems. On the other hand, automatic mesh generation is often not feasible for building many 3D hexahedral meshes. A stabilized, nodally integrated linear tetrahedral is developed and shown to perform very well in problems with plasticity, nearly incompressible materials and acute bending. The formulation is analytically and numerically shown to be stable and optimally convergent for the compressible case provided sufficient smoothness of the exact solution u ∈ C2 ∩ (H1)3. Future work may extend the formulation to the incompressible regime and relax the regularity requirements; nonetheless, the results demonstrate that the method is not susceptible to locking and performs quite well in several standard linear and nonlinear benchmarks. Published in 2006 by John Wiley & Sons, Ltd.