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| Plasticity (physics) | |
|---|---|
| Name | Plasticity (physics) |
| Field | Materials science; Solid mechanics |
Plasticity (physics) is the branch of Materials science and Solid mechanics that studies permanent, non-recoverable deformation in solids under applied loads. It bridges concepts from Metallurgy, Materials engineering, Continuum mechanics, and Applied physics to describe how crystalline and amorphous solids yield, flow, and harden. Plasticity underpins technologies ranging from Civil engineering structures and Aerospace engineering components to microfabrication in Semiconductor industry and shaping in Automotive industry.
Plastic deformation occurs when stress exceeds a material-specific threshold, producing irreversible changes in shape and internal structure. Historical development involved contributions from figures and institutions such as Augustin-Jean Fresnel, Isaac Newton (foundations of mechanics), Lord Kelvin (elasticity advances), the Royal Society, and research centers like Massachusetts Institute of Technology and Imperial College London. Modern plasticity integrates empirical laws from Metallurgy with continuum theories from Navier–Stokes analogues in solids and with thermodynamic frameworks advanced at laboratories including Los Alamos National Laboratory and Lawrence Berkeley National Laboratory.
Key quantities include stress, strain, yield point, hardening, and flow rules. The stress tensor and strain tensor formulations derive from Cauchy and Green frameworks, while yield phenomena reference thresholds associated with concepts from Tresca and Coulomb traditions. Elastic–plastic separation uses ideas from Hooke's law for linear elasticity and energy principles developed by Lagrange and Hamilton. Rate dependence links to viscoplastic theories connected to research at Max Planck Society and National Institute of Standards and Technology. Temperature effects on yield and ductility invoke studies associated with Gustav Tammann and the International Union of Pure and Applied Chemistry standards.
Constitutive models relate stress and strain via mathematical laws such as von Mises, Tresca, Drucker–Prager, and Mohr–Coulomb criteria. The von Mises criterion has roots in work by Richard von Mises and was extended in plasticity theory alongside formulations by Henry Moseley-era mechanics. Hardening models include isotropic, kinematic, and combined rules developed in laboratories like École Polytechnique and under programs affiliated with National Aeronautics and Space Administration. Advanced constitutive formulations incorporate anisotropy using approaches from Kristian Birkeland-inspired texture analysis and crystal plasticity models influenced by research at California Institute of Technology and ETH Zurich.
At the microscale, plasticity arises from dislocation motion, twinning, grain boundary sliding, and phase transformations. The dislocation theory owes much to pioneers like G. I. Taylor, Emanuel C. Stiefel-era crystallography, and Alan Cottrell, while twinning research connects to work by Fritz Haber-era metallurgy groups. Grain boundary mechanisms were elaborated in studies at Johns Hopkins University and Carnegie Institution for Science. In amorphous metals and polymers, shear transformation zones and free volume concepts were developed in collaborations involving IBM research labs and Bell Labs.
Standard tests include tensile, compression, shear, and fatigue experiments standardized by bodies like ASTM International and ISO. Techniques to observe microstructural evolution use transmission electron microscopy linked to Ernest Ruska innovations, scanning electron microscopy associated with Max Knoll, and X-ray diffraction methods pioneered at facilities such as European Synchrotron Radiation Facility and Brookhaven National Laboratory. Nanoindentation, digital image correlation, and acoustic emission monitoring have provenance in university labs including Stanford University and University of Cambridge and are complemented by in situ tests at Argonne National Laboratory beamlines.
Plasticity informs design codes in Eurocode and American Institute of Steel Construction specifications for structural members, crashworthiness algorithms in National Highway Traffic Safety Administration programs, and forming limits in sheet metal processing used by Toyota and Volkswagen Group. It affects lifetime predictions in Nuclear Regulatory Commission assessments for reactor components and reliability in Intel microfabrication. Understanding strain localization underpins mitigation strategies developed in projects by United States Department of Energy and standards from International Electrotechnical Commission.
Numerical simulation employs finite element methods from software ecosystems originating at Delft University of Technology and Rutherford Appleton Laboratory, boundary element methods, and crystal plasticity finite element frameworks developed at institutions like National Institute for Materials Science and École Normale Supérieure. Constitutive integration algorithms exploit return mapping schemes associated with work from Ray W. Clough-era computational mechanics, and multiscale approaches couple molecular dynamics models from Los Alamos National Laboratory with continuum solvers used at Sandia National Laboratories. High-performance computing implementations leverage resources at Oak Ridge National Laboratory and parallel libraries influenced by Lawrence Livermore National Laboratory collaborations.