The check of compliance with legislative requirements for vibration protection of operators is carried out at the stage of certification testing of new and upgrading products. At this stage, the further development is associated with high time and material costs. The article substantiates the possibility of use of a calculation and experimental method which allows to determine at the development stage the level and frequency content of potentially dangerous sources of vibration; to develop a computer model for the system «excitation source - frame - cab - antivibration seat - operator»; to make out proposals to comply with legislative requirements by means of parametric forecasting. As an example, the problem of vibration in the low frequency range of 2-14 Hz is considered. This vibration is the result of the process of rolling of track rollers on track chain that lies on the yieldable soil foundation. According to biomedical research, the resonance frequencies of critical parts of human body are in this low frequency range, which is displayed in sanitary norms. Based on the analysis of field test results, the kinematic impact of track rollers on tractor frame is represented as stationary narrow-band random processes. Mathematical model of the system is described by a set of differential equations with random input processes. The methods of statistical dynamics are used to implement the model. The simulation results are presented as a set of transfer functions. They represent the distribution of resonance frequencies of angular and heave oscillations of the separate system elements and the spectral density functions. These results allow to obtain the quantitative estimations in the form of mean-square values of the output processes. The use of this approach allows to solve the problems of vibration protection of operator at the stages of design and testing of prototypes of road-building machinery. It is achieved by tuning-out of the system «track assembly - frame - cab - antivibration seat» from resonance phenomena and by introducing some design solutions.
The asymmetric flexible rotor turbocharger supported by floating ring bearings is studied. We use the model of flexible asymmetric rotor and the nonlinear bearing forces have been calculated by using the numerical solution of the Reynolds equation for both fluid films. It is shown that at this rotor speed range the rotor performs direct nonsynchronous regular precession, which corresponds to the conical shape of the rotor motion. The rotor speed at which the shape of the rotor precession abruptly changes from conical to cylindrical has been revealed. It is established that the cylindrical shape of the precession corresponds to the unacceptable increase of bearing loads. Thus, the maximum rotational speed above which the turbocharger rotor under study shuts has been found. The implications can be applied to the turbocharger rotors supported by two bearings with floating ring bearings and console location of the compressor and turbine wheels.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.