Instructions:

- use your mouse to move the black nodes.
- use another mouse button (or a modifier key) to add/remove nails.
**be gentle**, the simulation may crash if you are too violent (reselect the shape if this happens).

When time is fixed, balance of momentum and the constitutive law (material response to deformation) together give a system of non-linear equations relating position and acceleration of the nodes. In other words, application of the Finite Element Method produces a second order non-linear ODE.

x_{n+1} = x_{n} + v_{n}*dt + 1/2*(1/2*a_{n} + 1/2*a_{n+1})*dt^{2}v
_{n+1} = v_{n} + (1/2*a_{n} + 1/2*a_{n+1})*dt |

The applet runs almost as fast as it can on your machine, up to a maximum of 250 frames/second. The simulation is harder to crash on a fast machine with a fast Java interpreter.

For those even more technically inclined:

The non-linear model used:

The linear model:

Damping term:

Where:

last updated: July 8, 2003

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