forked from 1b-agent/fieldcraft-upstream
jyvikoandClaude Opus 5.5
bc75fd08d1
An explicit step may ask for mass scaling to a target time increment (on a set, or the whole model): elements whose stable increment is below it get the density that reaches it, with their lumped masses, frequency bound and hourglass scales; adiabatic heating keeps the physical density. The run reports the elements scaled, the added mass in all and per section with its fraction, a warning, and the added mass's kinetic energy in the energy account. Verified on a uniform bar scaled to twice its increment (added mass 3×, increment doubled, a quarter of the kinetic energy left to the physical mass). ROADMAP and parity note the hyperelastic materials and mass scaling. Co-Authored-By: Claude Opus 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo
111 lines
4.9 KiB
Rust
111 lines
4.9 KiB
Rust
//! FieldCraft's explicit dynamics solver: transient response of a model's explicit dynamic step
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//! by central-difference time integration.
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//!
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//! The method is the explicit central-difference scheme of T. Belytschko, W. K. Liu, B. Moran,
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//! K. Elkhodary, *Nonlinear Finite Elements for Continua and Structures*, 2nd ed., Wiley 2014
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//! (ch. 6, the flowchart of Box 6.1): with a diagonal (lumped) mass M,
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//! a = M⁻¹(f_ext − f_int), v^{n+½} = v^{n−½} + Δt^n a^n, u^{n+1} = u^n + Δt^{n+½} v^{n+½},
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//! so a time increment is one pass over the elements and a division per degree of freedom.
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//!
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//! - **System** ([`system`]): the model is resolved; one-point hexahedra and nodal-pressure
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//! tetrahedra with their materials, row-sum lumped masses, prescribed velocities, rigid walls,
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//! initial velocities and the constant load vector of the step.
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//! - **Elements** ([`elements`]): the uniform-strain hexahedron with Flanagan–Belytschko
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//! hourglass control (viscous or stiffness), the Bonet–Burton average nodal pressure
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//! tetrahedron, von Neumann–Richtmyer/Wilkins bulk viscosity, and the element critical time
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//! increments.
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//! - **Contact** ([`contact`]): penalty contact between element faces (pairs both ways, single
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//! surface and general contact) with Coulomb friction by a regularised return map, a bucket
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//! grid search, and the stiffness from the masses and the stable increment.
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//! - **Integration** ([`integrate`]): the time loop, kinematic constraints (rigid walls with
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//! friction), energy accounting with a balance check, history samples and field frames
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//! ([`result`]).
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//!
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//! With nonlinear geometry (the default) the elements are updated Lagrangian and the material
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//! state is integrated in rate form with an objective stress rate (Jaumann by Hughes–Winget,
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//! Green–Naghdi by Flanagan–Taylor); materials are hypoelastic or J2 plastic (bilinear,
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//! tabulated, Johnson–Cook) with Johnson–Cook damage and element erosion ([`elements`];
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//! docs/solvers/literature.md, Parts F and J). Without it the gradients stay those of the
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//! undeformed mesh (small displacements).
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//!
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//! Elements are updated on threads ([`fieldcraft_parallel`]), each owning its state, and their
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//! nodal forces are added in label order as a sequential loop adds them, with no parallel
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//! reductions, so the same model gives the same numbers bit for bit on any number of threads;
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//! sizes, increments and output are capped by [`Limits`].
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#![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
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#![forbid(unsafe_code)]
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// Small fixed-size vector kernels read as the textbook formulas with index loops.
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#![allow(clippy::needless_range_loop)]
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pub mod contact;
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pub mod discrete;
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pub mod elements;
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pub mod integrate;
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pub mod result;
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pub mod system;
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pub use elements::Failure;
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pub use integrate::solve_explicit;
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pub use result::{ContactSummary, ControllingElement, Energies, ErodedElement, ExplicitResult, Frame, History, MassScalingSummary};
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#[derive(Debug, Clone, PartialEq, thiserror::Error)]
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pub enum Error {
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#[error(transparent)]
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Model(#[from] fieldcraft_model::Error),
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#[error("invalid input: {0}")]
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Invalid(String),
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#[error("not supported yet: {0}")]
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NotSupported(String),
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/// An element kernel failed (inverted geometry, …).
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#[error("element {label}: {source}")]
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Element { label: u32, source: fieldcraft_fem::Error },
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#[error("limit reached: {0}")]
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Limit(String),
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/// The solution stopped being finite.
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#[error("the solution became unstable: {0}")]
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Unstable(String),
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/// A broken internal invariant (a bug), reported instead of a panic.
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#[error("internal error: {0}")]
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Internal(String),
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}
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pub type Result<T> = std::result::Result<T, Error>;
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impl Error {
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/// A kernel error, naming the element.
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pub fn element(label: u32, source: fieldcraft_fem::Error) -> Error {
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Error::Element { label, source }
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}
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}
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/// Caps on the size and length of a run.
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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pub struct Limits {
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/// Degrees of freedom of the mesh.
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pub max_dofs: usize,
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/// Time increments; the step's own cap applies too, whichever is lower.
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pub max_increments: u64,
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/// Numbers kept in field frames and histories together (8 bytes each).
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pub max_output_values: usize,
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/// Element faces of every contact surface together.
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pub max_contact_faces: usize,
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}
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impl Limits {
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pub const MAX_DOFS: usize = 6_000_000;
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pub const MAX_INCREMENTS: u64 = fieldcraft_model::steps::MAX_INCREMENTS;
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pub const MAX_OUTPUT_VALUES: usize = 50_000_000;
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pub const MAX_CONTACT_FACES: usize = 10_000_000;
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}
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impl Default for Limits {
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fn default() -> Limits {
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Limits {
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max_dofs: Limits::MAX_DOFS,
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max_increments: Limits::MAX_INCREMENTS,
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max_output_values: Limits::MAX_OUTPUT_VALUES,
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max_contact_faces: Limits::MAX_CONTACT_FACES,
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}
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}
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}
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