Detection of silicone fluid loss in torsional vibration dampers based on tensogram analysis

The paper considers faults of silicone torsional vibration dampers used in internal combustion engines and methods for non-disassembly diagnostics of their technical condition. It is noted that silicone fluid loss is one of the most common and hazardous damper failures. When access to the damper is difficult or the damper has a non-disassemblable design, determining its operability becomes problematic. The most comprehensive information on the condition of individual components and the shafting as a whole can be obtained using torsional vibration measurements or strain-gauge measurements. To identify the most effective method for detecting faults, a series of laboratory tests was carried out on a test rig simulating the development of vibrations in a marine propulsion plant with direct power transmission from a medium-speed engine to the propeller. Tests of a faulty damper with silicone fluid loss, combined with wavelet analysis of tensograms, showed that non-periodic strain shock waves arise in the torsionally vibrating system. As an alternative to the traditional method of tensogram analysis, the use of an analytical shock-pulse function is proposed. Unlike classical wavelet analysis, this function “scans” the tensogram not over the entire possible frequency spectrum, but only at the natural frequencies. Like wavelet analysis, this method makes it possible to determine the time localization of strain shock waves in the shaft material. The main advantage of the new approach is that the shock function establishes a deterministic relationship between the measurement section of the shafting where strain-gauge measurements are performed and the source of vibrations. The paper presents an example of reconstructing the parameters of a shock pulse in a laboratorymodel damper based on the processing results of an actual tensogram. The dynamics of changes in the mean power coefficient are proposed as the main criterion for assessing the presence of shock pulses in the tensogram. The proposed approach requires further experimental studies, including tests on actual marine propulsion plants, which will be the subject of further research .