Prediction of limit states of pipelines of high pressure of hydraulic and gas systems in the commissioning phase
Dynamics, strength of machines, instruments and equipment
Аuthors*, **, ***
Komsomolsk-na-Amure State University, 27, Lenina str., Komsomolsk-on-Amur, 681013, Russia
In the manufacture and operation of pipelines of various diameter high-pressure hydro-gas systems in the air and rocket, there is the problem of forecasting safe their life. Statistical methods of calculation of durability of the effects of cyclic loading allow large scatter in the data and suggest the use of unnecessarily large reserves of strength. Therefore there is a need for research and development of criteria that take into account the mechanical properties of materials under complex stress state and defect structure of the material of construction. This is possible by using acoustic emission techniques.
Normally, before entering the hydro-gas systems in their operation under pressure 25% higher than the maximum operating this load causes an elastic-plastic deformation of the material of construction of the first cycle of loading and acoustic emission. If the capture test parameters of the acoustic emission, it is possible to establish a microstructure of the structural defects of the material.
To develop and test the proposed methodology in Komsomolsk-on-Amur complex program material longevity research has been developed State Technical University with software loading on different trajectories of mechanical low-cycle loading in flat tension conditions.
Cyclic loading of tubular samples in the chosen path was made before its destruction n and simultaneously recorded acoustic emission signals. acoustic emission signals in the analysis were divided according to the degree of danger of generating sources. Each recorded acoustic emission signal is seen as a time series, formed a kind of dynamic system, and fr om the standpoint of nonlinear dynamics of the task is to determine the dynamic system of degrees of freedom for the one-dimensional projection of its evolution in the phase space.
Using modern methods of nonlinear dynamics for the one-dimensional time series was reconstructed multidimensional attractor, the metric properties which are very similar to the evolution of the study of the dynamical system.
Knowing the general laws of change of the acoustic emission signal parameters for certain values of stresses for the structural material, it is possible to build a surface lim it Status Word for reference points for the respective kinds of stress-strain state, for all values of voltage and determine the durability of parts experiencing cyclic loads along any path loading. With the above approach, this will require setting a minimum number of time-consuming experiments.
Thus, the prediction of longevity of details of pipelines of hydro-gas systems in aircraft and rocket may carry out the initial stages of operation for the acoustic emission signal parameters with a high degree of reliability at a relatively small number of preliminary experiments.
Keywords:durability, structural materials, cyclic loading, the trajectory of loading
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