// Constructor specifying material properties.
HuntCrossleyForce::ContactParameters::ContactParameters
   (double stiffness, double dissipation, double staticFriction, 
    double dynamicFriction, double viscousFriction)
{
    constructProperties();
    set_stiffness(stiffness);
    set_dissipation(dissipation);
    set_static_friction(staticFriction);
    set_dynamic_friction(dynamicFriction);
    set_viscous_friction(viscousFriction);
}
void HuntCrossleyForce::ContactParameters::setDissipation(double dissipation)
{
    set_dissipation(dissipation);
}
void ElasticFoundationForce::ContactParameters::setDissipation(double dissipation)
{
    set_dissipation(dissipation);
}