METHOD FOR DETEction of STRESSed STATE IN annular welded joints of PIPELINES

摘要

A method for determination of stressed state in annular welded joints of pipelines is in the fact that with rotation laid on magnetoelastic transducer output signal change is determined and a calibration coefficient is set at the sample, this is made of the same material as the pipe under investigation. At that with nondestructive method the averaged by the area of ​​contact of the sensor difference of main stresses is measured, and the expected averaged by contact area difference of main stresses is determined through the components of the tensor of native plastic deformations. By means of functional deviation of the measured average value of the difference of main stresses from the expected average value is minimized, with determination of the parameters of the component of the tensor of native plastic deformations. After that are circular and axial stresses at arbitrary point of the pipeline are found. The value of the component of total strain tensor is determined as the sum of the elastic deformation tensor component and the component of the conventional plastic deformation field tensor. Integral representations of stress tensor components are fixed through the unknown components of conventional plastic deformation field tensor with construction of functional, minimization of which provides the least discrepancy between the experimentally determined and same theoretically calculated characteristics of stress fields. By solving the inverse problem of the shell theory with their native stresses the values of the component of the tensor of field of conventional plastic deformations are found, by those the components of the tensor of residual stresses in arbitrary point of the circular welded joint of the pipeline with different thicknesses are determined, including the ones that can not be obtained experimentally. After that the circular and axial stresses at arbitrary point of the pipeline are found, by those conclusion on its volumetric stressed state is made, with account of the different thicknesses of welded joint and asymmetry of the distribution of residual deformations with respect to the cross section of the weld seam.