Bodies

The Bodies section lists all the bodies within the simulation model. Users can review the parts of the assembly that principia MBS has extracted from Onshape and set overrides for some of their properties.

info

Each body introduces six degrees of freedom, increasing the overall size of the problem to be solved by the principia MBS engine. If you are interested in reducing simulation time and improving overall performance, try combining multiple parts into one when they behave like one body in reality (e.g. welded construction).

tip

principia MBS allows to compute the cumulative mass of multiple bodies by checking the checkbox next to a body of interest. This may be used for quick plausibility checks and for debugging of models.

caution

In case there are no material properties defined for a body in Onshape (Part studio), principia MBS sets defaults for inertia properties:

• mass = $\mathrm{1 \; kg}$
• center of gravity = $\mathrm{\begin{bmatrix} 0 & 0 & 0 \end{bmatrix}}$ (relative to body reference)
• principal moments of inertia = $\mathrm{\begin{bmatrix} 1 & 1 & 1 \end{bmatrix}\; kgm^2}$
• principal axes of inertia = $\mathrm{\begin{bmatrix} 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1\end{bmatrix}}$ (relative to body reference)