We present a system approach to evaluating dynamic forms of interactions between elements of mechanical oscillatory systems, which can be applied as design diagrams of engineering objects used for transport or technology purposes. The approach of structural mathematical modelling was used, where a mechanical oscillatory system (with the finite number of freedom degrees) is compared to the block diagram of a dynamically equivalent automatic control system. The research object was represented by a family of mechanical oscillatory systems with the finite number of freedom degrees under the action of connected force harmonic disturbances. The main research focus was on a set of dynamic states of an engineering object, which are caused by the application of common-phase external force disturbances at various frequencies and characterised by a connection coefficient. For a family of chain mechanical oscillatory systems with two degrees of freedom, a method for interpreting a set of dynamic states in the form of oriented graphs was developed. A method for constructing a population graph of dynamic states based on the frequency response of system transfer functions was developed. Within the framework of the developed interpretation, the graphs of dynamic states can be considered as peculiar invariants that persist on sets of mechanical oscillatory system parameters. Using the methodology of structural mathematical modelling, a concept of dynamic invariants was developed, according to which the totality of dynamic invariants can be used to provide a general evaluation of the variety of dynamic states and forms of dynamic interactions between the elements of mechanical oscillatory systems. The proposed concept of dynamic invariants extends the methodology of structural mathematical modelling in relation to the problems of system analysis for ensuring the safety of engineering objects for transport and technology purposes under the conditions of connected vibrational loading.
