A first-order hyperbolic Arbitrary Lagrangian Eulerian conservation formulation for nonlinear solid dynamics in irreversible processes

The paper introduces a computational framework that makes use of a novel Arbitrary Lagrangian Eulerian (ALE) conservation law formulation for nonlinear solid dynamics. In addition to the standard mass conservation law and the linear momentum conservation law, the framework extends its application to consider more general irreversible processes such as thermo-elasticity and thermo-visco-plasticity. This requires the incorporation of the first law of thermodynamics, expressed in terms of the entropy density, as an additional conservation law. To disassociate material particles from mesh positions, the framework introduces an additional reference configuration, extending beyond conventional material and spatial descriptions. The determination of the mesh motion involves the solution of a conservation-type momentum equation, ensuring optimal mesh movement and contributing to maintaining a high-quality mesh and improving solution accuracy, particularly in regions undergoing large plastic flows. To maintain equal convergence orders for all variables (strains/stresses, velocities/displacements and temperature/entropy), the standard deformation gradient tensor (measured from material to spatial configuration) is evaluated through a multiplicative decomposition into two auxiliary deformation gradient tensors. Both are obtained through additional first-order conservation laws. The exploitation of the hyperbolic nature of the underlying system, together with accurate wave speed bounds, ensures the stability of explicit time integrators. For spatial discretisation, a vertex-centred Godunov-type Finite Volume method is employed and suitably adapted to the formulation at hand. To guarantee stability from both the continuum and the semi-discretisation standpoints, a carefully designed numerical interface flux is presented. Lyapunov stability analysis is carried out by evaluating the time variation of the Ballistic energy of the system, aiming to ensure the positive production of numerical entropy. Finally, a variety of three dimensional benchmark problems are presented to illustrate the robustness and applicability of the framework. •Incorporation of irreversible and thermally coupled constitutive responses within a conservative ALE framework.•The introduction of a conservation law for the material motion associated with a fictitious constitutive response.•Demonstration of numerical entropy production through the use of the Ballistic free energy.•Implementation into the