DefaultUniversalToughness is DefaultMateToughness:
    .doc: """
    Defines one toughness model for each constrained degree of freedom for a Universal.
    Two rotational degrees of freedom are left unconstrained -
    rotation around normal and cross, therefore we define toughness for around main,
    the constrained rotational direction.
    """
    along_main is Physics.Interactions.Toughness.DefaultToughness
    along_normal is Physics.Interactions.Toughness.DefaultToughness
    along_cross is Physics.Interactions.Toughness.DefaultToughness
    around_main is Physics.Interactions.Toughness.DefaultToughness
