APPLICATION OF THE METHODS OF MECHANICAL RESONANCE FOR THE DETECTION OF DEFECTS IN STEELS OF STEAM PIPELINES AFTER OPERATION

摘要

We use linear and nonlinear methods of mechanical resonance to detect defects in steels after operation for~7-10~4 -2.45-10~5 h in steam pipelines of a thermoelectric plant. We determine the sound velocity, vibration decrement, its dependence on the amplitude of maximum cyclic stresses, and the dependence of the resonance frequency of a cantilevered rod specimen on the strain amplitude. It is shown that the vibration decrement of materials after operation is higher than in the as-delivered state and its dependence on the stress amplitude becomes stronger. It is found that the material after operation is characterized by the nonlinear elastic behavior, which manifests itself as a distortion of the resonance curve and in the form of dependence of the resonance frequency on the amplitude. We establish a linear dependence of the resonance frequency on the strain amplitude, which is in good agreement with a similar dependence of the vibration decrement. We confirm that the nonlinear methods are promising for the detection of defects in steam pipelines.