newton.utils.create_cable_stiffness_from_elastic_moduli#

newton.utils.create_cable_stiffness_from_elastic_moduli(youngs_modulus, radius)[source]#

Create rod/cable stiffness parameters from elastic moduli (circular cross-section).

This returns the material-like stiffness values expected by ModelBuilder.add_rod() / ModelBuilder.add_rod_graph():

  • stretch_stiffness = E * A [N]

  • bend_stiffness = E * I [N*m^2]

where: - A = pi * r^2 - I = (pi * r^4) / 4 (area moment of inertia for a solid circular rod)

Note: Newton internally converts these into per-joint effective stiffnesses by dividing by segment length. This helper intentionally does not perform any length normalization.

Parameters:

  • youngs_modulus (float) – Young’s modulus E in Pascals [N/m^2].

  • radius (float) – Rod/cable radius r in meters.

Returns:

Tuple (stretch_stiffness, bend_stiffness) = (E*A, E*I).

Return type:

tuple[float, float]