No abstract

Purpose: To build a factor model of vibrodynamic loading influence on pipeline reliability based on the results of laboratory tests carried out taking into account the amplitude-frequency characteristics of the vibration process of the operating pipeline, obtained during full-scale tests at the railway station. On the basis of the factor model to determine the most significant factors affecting the reliability of pipelines under the action of vibrodynamic loading and to propose ways to improve their reliability. Methods: The plan of fractional factor experiment of 25-2 type was used to carry out laboratory tests of pipeline reliability under the influence of stresses of familiar constant cycle. The experiments were carried out on a test bench with a pulsating cylinder of type PC with a maximum load of 200 kN. Voltages were applied to the pipeline under test from control panels of static (from soil) and dynamic (from rolling stock) loads. Impulse shape was sinusoidal, the closest to natural one, cycle frequency — 300 c/min. The regression equation coefficients were calculated on a computer using the multiple linear correlation program. The significance of the regression coefficients was assessed by Student's test. Fisher's test was used to check the adequacy of the model to the experimental data. Adequacy of the regression equation to the physics of the phenomenon was tested using Student's test. Results: Tests of the pipeline with application of fractional factor experiment of 25-2 type allowed to build a factor model of the process under study in the form of polynomial of the first degree. It has been established that the main factors influencing pipeline reliability under vibrodynamic loading are train load, vibration amplitude of the pipeline and the depth of its embedding. The vibration frequency of the pipeline has no significant influence on the pipeline reliability. However, from the regression equation it follows that the pipeline vibration frequency depends on its diameter. Practical significance: The equation of linear regression is obtained, which is transformed by switching from coded values of factors to natural values, which can be used for practical purposes to determine the intensity of failures and the duration of operation of pipelines between failures.

The present paper presents the rolling stock vibrodynamic impact model on railway pipelines, obtained on the basis of experimental studies conducted under field conditions at a railway station. The experimental research program provided for the determination of the effect of vibration-dynamic effects of rolling stock on the working condition of pipes and butt joints by conducting vibration-measuring work on the investigated section of the railway pipeline during the passage of various series of locomotives. The proposed modeling method makes it possible to obtain a correlation function of the oscillatory process of a railway pipeline, on the basis of which a spectral density is constructed to identify the amplitude-frequency range at which a stable resonance region occurs, leading to the destruction of the pipeline.