Applied model of assessment of intensity of the stressed deformed state of pipelines by evaluation ofmagnetic anisotropy of coercive forces. Part 1

Abstract

The problem of applied diagnostics, statistically rigorous by the proposed model analogue, running stressed-deformed state of the main (trunk) shell is studied by the method of magnetic coercimetria. The relationship between the parameters of the loop of magnetic hysteresis is stochastically related with structural and mechanical state of the material of the pipeline wall and with the rest of equal conditions allows to effectively detect the zone of concentration of local stresses on the stage of their forming and development (propagation) on the basis of quantitative comparative analysis of their value with calculated equivalent mechanical stresses in principal (main) planes for particular pipe material considering that the operational stresses shouldn’t be larger than 30–50 %of the yield limit. The hypothesis H0 about the possibility of description of the measurement data of the stressed mechanical state by the magnetic-static method of coercimetria is made taking into account the peculiarities of disturbances caused by the operation of electric chains of the measuring apparatus during its metrological calibration. This hypothesis confirms that the arcsine function is a law of distribution probability density of the measured values of the coefficient of magnetic anisotropy as a response of the mechanical state of the pipe shell, that the parameter Q equals 0.95 on the confidence level and substantiates the evaluation of frequency of the influencing equivalent stresses in the whole range of loads applied to the shell by the inside normalized variable pressure. On the basis of corresponding scaling and renormalization of investigative values of the coefficient of magnetic anisotropy, the technique of determination of the level of mechanical stresses in the object of diagnostics is developed and the statistically rigorous compatibility in the certain range of influence of internal pressure in the pipeline is demonstrated using the results of preliminary metrological calibration of coercimeters obtained for different pipe steels.