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Research - Materials Modeling


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Materials Modeling

In what may seem an unexpected area for a fluid dynamics group, in the past decade a significant research effort in solid mechanics has grown in T-3. The point of relevance is that many of the applications of interest involve large deformations of solids that make use of numerical methods or theoretical approaches that have been developed for fluids. The description of the dynamic response of solids to high-velocity, large deformation loadings involve strains between 0 and 200, strain rates from 10-2s-1 to 107s-1, and temperatures from 300K to beyond the melting point. Nonlinear, anisotropic inelastic material response including strain-rate phenomena, thermal softening, hardening, and failure must be considered. The resulting material models must be compatible with the incremental, continuum formulations inherent to large deformation, numerical approaches and be numerically robust and computationally efficient for large-scale computational simulations.

High Strain-Rate Plasticity
The flow stress of a metal is affected strongly by the rate of deformation. Efforts are being pursued to implement plasticity models, which accurately model hardening phenomena due to strain and strain-rate, into computational analyses [Maudlin etal, 1995]. Furthermore, the effects of the anisotropic plastic deformation on problems related to metal forming, machining, and impact events have been considered. Material anisotropy is a consequence of the inherent crystalline structure of a solid. Information obtained from experiments and microstructural investigations are used to construct anisotropic yield surfaces for a number of materials. The evolution of texture, including twinning phenomena, also has been pursued.

There is considerable interest in using engineered composite materials to develop lighter structures that are strong under adverse conditions. Mechanical attributes, which can be tailored to provide high strength and stiffness, light weight, abrasion resistance, improved damage tolerance, and inexpensive fabrication requirements, have established composites as ideal materials for many structural applications. Composite models are under development for both epoxy and metal matrix composites and use a homogenization approach, which accounts for the response of the constituents and the interfaces within the composite [Addessio etal.].

Material Failure
Phenomena including shear banding and the nucleation and growth of porosity and cracks must be considered for the large deformation of materials. An engineering analysis cannot provide the resolution necessary for a detailed description of these micromechanical processes. Therefore, solutions of micromechanical events are obtained in terms of the far-field distributions of the stress state. The addition of failure phenomena to a continuum analysis also can lead to numerical complexities such as strain localization. The equations governing the dynamics of failure may become ill-posed in regions of material softening. Efforts to mitigate these numerical problems have resulted in the development of rate-dependent, overstress material models for ductile failure [Addessio etal, 1993][Addessio etal, 1993][Johnson etal, 1988] and brittle failure [Addessio etal, 1990].

Los Alamos Materials Modeling Projects
All of the filled circles are linkable projects.
All of the empty circles are navigational guides.

  • Strain-Rate Plasticity
  • Anisotropic Elasticity/Plasticity
  • Dynamic Failure
  • Polymer Modeling
    • Stochastic Approach to Modeling Rate
  • Foam Modeling
  • Composite Materials:
    • Fiber Reinforced Composites
    • High Explosive Materials
  • Shape Memory Alloys:
    Phase Change:
    1. Thermomechanical Response of Solids
    2. Homogenization and Microstructural Modeling
    * Twinning Phenomena
    * Binary Alloys
    * Grain Size in Solidification of Binary Alloys

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This is from "The Legacy and Future of CFD at LANL" (LAUR#LA-UR-1426)(365Kb pdf file)






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