Paradigm Shift in Data Content and Informatics Infrastructure Required for Generalized Constitutive Modeling of Material
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nstitutive laws. Constitutive theory concerns the mathematical modeling of the physical response (output) of a material to a given stimulus (input); that input can be a generalized force or displacement. The importance of accurate constitutive relationships is illustrated in Figure 1; they form the primary link between stress (σij) and strain (ε ij) components at any point within a body. These relations may be simple (as in the case of linear elasticity) or extremely complex (as in the case of viscoplasticity), depending upon the materials composing the body and the conditions to which the body is subjected (e.g., temperature, loading, environment). Constitutive relations for a particular material are determined experimentally, and they may involve both physically (directly) measurable quantities (e.g., strain, temperature, time) and indirectly measurable internal parameters, often referred to as internal-state variables. Three types of experimentation are necessary to support the rational formulation of constitutive equations. These are (1) exploratory tests, which illuminate the salient response (e.g., time-dependence/timeindependence, sensitivity to hydrostatic stress field, material symmetry and/or anisotropy, etc.), identify fundamental deformation and damage mechanisms, and guide the mathematical structure of the model; (2) characterization tests, which provide the required database for determining the material-specific functional forms and associated parameters so as to represent a particular material over a given range of conditions; and (3) validation tests, often structural (multiaxial) in nature, which provide the prototypical response data that enable validation of a constitutive model through a comparison of structural response with predictions based on the model. Results from validation tests ideally provide feedback for subsequent developmental or refinement efforts.
Keywords: constitutive modeling, informatics, materials characterization, simulation.
Introduction The solution of a solid mechanics problem involves the establishment of a statically admissible field (one which satisfies equilibrium internally and traction boundary
conditions) and a kinematically admissible field (satisfaction of strain–displacement relations and displacement boundary conditions), and the satisfaction of material
MRS BULLETIN • VOLUME 31 • DECEMBER 2006 • www/mrs.org/bulletin
Figure 1. Schematic illustration of key aspects of mechanics problems. F is body and surface forces, U is displacement, σ is stress, and ε is strain.
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Paradigm Shift Required for Generalized Constitutive Modeling of Materials Behavior
An important aspect of such experimental programs is developing the required infrastructure for capturing, analyzing, and disseminating the potentially massive amounts of materials data within and among organizations. Consequently, the primary objective herein is to highlight the need for a paradigm shift in materials data collection, analysis, and dissemination so as to maximize the impact on both the prac
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