Abstract

The current state of the art in determining the remaining fatigue life of a dented pipeline is to use FE- and empirical models that were created based on known, artificial dents. However, this approach does not account for the actual material state, which is influenced by a combination of damages. The objective of this research is to determine the actual current state of fatigue of a dent in a pipeline by using nonlinear ultrasound (NLU) as a material sensor to detect the gross effect of accumulated dislocations. The physical effect that is monitored by the nonlinear ultrasonic measurement is the generation of higher harmonic frequencies in the initially monochromatic ultrasonic waves propagating in the component. The degree of nonlinearity is quantified with the acoustic nonlinearity parameter, ??, which is an absolute, measurable material constant. The first step is to take baseline measurements to determine fabrication, pre-strain and material intrinsic influences in the material specimen made of X42, X52 and X60 pipeline steel. Then pre-strain is applied to simulate a dent. At different stages during the materials fatigue life, the straining of the material is interrupted to perform NLU measurements. The results are expected to show an increasing nonlinearity with increasing fatigue.

How to Cite:

Pfeifer, D. ., Kim, J. . & Jacobs, L. ., (2019) “Using nonlinear ultrasound to quantify the material state of pipeline steel specimens with mechanical defects”, Review of Progress in Quantitative Nondestructive Evaluation .