ar < ContactForceN
    %% Public properties
    properties (SetAccess = public, GetAccess = public)
        % Formulation options
        load_stiff_formula   uint8 = uint8.empty;   % flag for type of loading stiffness formulation
        unload_stiff_formula uint8 = uint8.empty;   % flag for type of unloading stiffness formulation
        
        % Contact parameters
        unload_stiff double = double.empty;   % unloading stiffness coefficient
        unload_param double = double.empty;   % variable unl