Experimental study on high temperature creep of P91 steel characterized by cumulative effects of nonlinear ultrasonic parameters

Hu, Bin; China Special Equipment Inspection and Research Center (CSEI); China

Bin, H.; China Special Equipment Inspection and Research Center (CSEI); China

ID: ECNDT-0494-2018
Session: Nonlinear Ultrasonics 2
Room: G2
Date: 2018-06-12
Time: 14:10 - 14:30

Aiming at the existing problems of nonlinear ultrasonic evaluation method for metal high temperature creep, which the fundamental and two harmonic amplitude with changing excitation frequency, and the inability to separate out different frequency harmonic caused by pulse excitation bandwidth, reference to the expression of the damage factor of Lamb wave stress wave and the ratio of high frequency energy to low frequency energy are used as the definition of nonlinear parameters, a method for characterizing metal creep at high temperature using the cumulative effects of nonlinear parameters in a certain frequency band is proposed. Firstly, according to the characteristics of nonlinear energy transfer from low frequency to high frequency, nonlinear parameters of the ratio of high frequency energy to low frequency energy at certain excitation frequency are obtained, Secondly, the nonlinear parameters of a certain frequency range are integrated on the basis of considering the variation of fundamental energy and harmonic energy with frequency, and the cumulative nonlinear response is obtained. The method was applied to detect the heat affected zone of P91 steel base metal and welding seam, and compared with the existing nonlinear ultrasonic testing method and conventional ultrasonic inspection method. The results show that the cumulative nonlinear parameters increase with the increase of creep time. This method can effectively distinguish the different creep states of the same material. It overcomes the shortcomings of other nonlinear ultrasonic testing methods, and can be used as an effective method for detecting the relative degree of creep degree of P91 steel welds.