Extension

Table of Contents

• Problem description
• Seaching for available models
• Outline

Note

Before diving into the following tutorials we recommend reading the Contributing guide.

NEML2 models can be easily extended or adapted to model the material behavior of your interest.

Problem description

This set of tutorials define a custom equation to model the conventional projectile motion problem:

$$\begin{array}{}\text{(1)}& \dot{\mathit{x}}& =\mathit{v},\text{(2)}& \dot{\mathit{v}}& =\mathit{a}=\mathit{g}-\mu \mathit{v},\end{array}$$

where $\mathit{x}$ and $\mathit{v}$ are the position and velocity of the projectile, respectively. $\mathit{g}$ is the gravitational acceleration, and $\mu$ is the dynamic viscosity. The projectile's trajectory can be numerically integrated using the backward-Euler method:

$$\begin{array}{}\text{(3)}& \mathbf{r}=\left\{\begin{array}{c}{r}_x\\ r_v\end{array}\right\}& =\left\{\begin{array}{c}\mathit{x}-{\mathit{x}}_n-(t-t_n)\dot{\mathit{x}}\\ \mathit{v}-{\mathit{v}}_n-(t-t_n)\dot{\mathit{v}}\end{array}\right\},\text{(4)}& \left\{\begin{array}{c}\mathit{x}\\ \mathit{v}\end{array}\right\}& =\underset{\mathit{x},\mathit{v}}{\mathrm{root}}\left(\mathbf{r}\right),\end{array}$$

subject to appropriate initial conditions ${\mathit{x}}_0$ and ${\mathit{v}}_0$

Seaching for available models

Among these equations:

• $\text{(1)}$ and $\text{(3)}$ can be defined using VecBackwardEulerTimeIntegration.
• $\text{(2)}$ is not available in NEML2, and is the focus of this set of tutorials. We will name it ProjectileAcceleration.
• $\text{(4)}$ is the ImplicitUpdate.

Outline

Each tutorial builds on top of the previous tutorials, introduces and explains one small piece in model development. It is therefore recommended to follow these tutorials in order.

• Connection to input files
• Argument declaration
• The forward operator
• Model composition
• Model visualization

The final model is then used in another set of tutorials on parameter calibration and inference.