This work is a further continuation of the investigations presented before at the previous conference. The basic attention is turned to improvement of the accuracy of the measurements of the oscillation changing, to development of a specified mathematical model of the oscillating process. The idea of the method is to cause oscillations in the ring at the frequency of its own mechanical resonance and at the multiple harmonics. The amplitude of the ring oscillations is measured in the gap by means of sensors according to two coordinates simultaneously. The frequency, phase and amplitude of the oscillations depend on the mechanical properties of the ring's material and its geometry. Micro-cracks, the areas with stresses, hardening defects, local overheating, loss of elasticity and other defects cause deviations of frequency, phase and amplitude from the standard. One of the special features of the proposed method is registration of the frequency response of the piston ring oscillations simultaneously in two planes-radial (the plane of the ring) and in the direction of axis. It allows to discover the defects (microcracks, thermal inhomogeneity, etc.) of the ring independently on their orientation along the assumed axes. This is a kind of non-destructive methods.

-A method of technical diagnostics of ship diesel engine -generator installation -is proposed. Spectral-power diagnostic parameters of the synchronous generator voltage and currents are used. The electric machine in this case is the multipurpose sensor of diagnostic parameters. A judgment on the quality of the operational processes in diesel engine cylinders and its technical condition is possible on the basis of these parameters. This method is applicable to piston compressor installations with electric drive. On the basis of such parameters as rotating torque, angular speed and angular acceleration it is possible to estimate the quality of the operating process in the cylinders of a diesel engine, the condition of its cylinder-piston group and the crank gear mechanism. The investigation was realized on the basis of a diesel-generator with linear load. The generator operation was considered for the case of constant RL load. Together with the above mentioned, the condition of bearings of synchronous machines, uniformity of the air gap, windings of the electric machine were estimated during the experiments as well. The frequency spectrum of the stator current of the generator was researched and analyzed. In this case the synchronous machine is becoming a rather exact multipurpose diagnostic sensor. The signal of nonuniformity in the operation process of diesel engine cylinders and its technical condition is the increasing of the amplitudes of typical frequencies.

The paper contains new results of the investigations announced by the authors in 2017, 2019 in the materials of "The 16 th , 18 th International Scientific Conference Engineering for Rural Development". The work is devoted to determination of the current condition of one of the most loaded elements of the cylinder-piston group of the vessel diesel engines -the piston ring. A new experimental board with a strengthened construction has been built. The piston ring with a gap is placed in a vertical position, it is fixed at a single point symmetrically to the gap. Its both half-segments form a fork. The board has an increased number of magnetoelectric sensors for a simultaneous registration of oscillations of the both segments along the radial and axial surfaces -X and Y. The oscillations of the ring are investigated in a regime of free and forced oscillations. In the regime of free oscillations, the ring experiences a single impact of a ball with a particular mass, length of its pendant on the angle of the shift. In the regime of forced oscillations, the ring is excited with the undamped oscillations on the frequency of own mechanical resonance and on the even harmonics. The frequency of the oscillations, phase and amplitude depend on the mechanical properties of the ring material and its geometry. The basic frequency of the forced oscillations for the first harmonic is determined experimentally and differs from the theoretical frequency obtained with mathematical modelling for 12-15 %. Mechanical oscillations of the ring have larger difference from the theoretical on the higher harmonics with frequency 2f 1 , 3f 1 . At the first stage of the diagnostics the parameters of the left and right segments are compared with each other. A ring without defects has similar parameters of the segments. The second stage of the diagnostics is the comparison of the obtained results with reference values that are average results of measurements of some serviceable rings without defects.