Magnetoacoustic emission detection method for fatigue damage of ferromagnetic metal component

Abstract

The invention relates to a magnetoacoustic emission detection method for fatigue damage of a ferromagnetic metal component. The method comprises the steps of firstly, generating an excitation magneticfield by using a sine wave voltage signal, gradually increasing a loading voltage until a bimodal envelope magnetoacoustic emission signal with an obvious tail peak is obtained, and taking a corresponding voltage peak value as a reference voltage; then, generating an excitation magnetic field by using a square wave voltage signal equal to or higher than a reference voltage, and acquiring a magnetoacoustic emission signal with a T-shaped envelope; and thirdly, calculating the average value of peak-to-peak values of the magnetoacoustic emission signal in multiple periods to serve as a characteristic parameter, and enabling the characteristic parameter to have inflection point change along with the development of the initiation and expansion of the fatigue crack, thereby identifying the initiation and expansion of the fatigue micro-crack, and giving a timely early warning for the failure of the component. According to the invention, the T-shaped envelope signals are obtained through square wave voltage excitation, the waveform of the T-shaped envelope signals is clear and easy to distinguish, on the basis that the reference voltage ensures enough magnetic field intensity, the anti-noise capacity of MAE is greatly improved, MAE fatigue monitoring engineering application is achieved, and the detection result is stable and reliable.

Description

technical field [0001] The invention belongs to the technical field of nondestructive detection of material damage, and in particular relates to a magnetoacoustic emission detection method for fatigue damage of ferromagnetic metal components. Background technique [0002] The fatigue life of metal components subjected to cyclic loading for a long time can be divided into three stages: (1) The first stage is the fatigue hardening or softening stage. In this stage, the microstructure of the material changes as a whole, and finally forms a stress-strain concentration area, resulting in Fatigue damage; (2) The second stage is the crack initiation stage, and the crack length in this stage is usually not greater than the grain size (10μm-100μm); (3) The third stage is the crack propagation stage, which is divided into stage I Stable crack growth and rapid crack growth in the second stage. The stable crack growth in the first stage refers to the expansion of the micro-crack along t...

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Problems solved by technology

Hou Binglin et al. (Hou Binglin, Zhou Jianping, Peng Xiang, et al. Application research of magnetoacoustic emission in non-destructive testing of rail properties [J]. Experimental Mechanics, 1998 (01): 99-105), using sine wave voltage signal The U74 rail steel was tested by MAE. The results show that with the increase of the number of fatigue cycles, the root mean square voltage of the MAE signal increases first and then decreases monotonously. It reaches the maximum value at about 20% of the fatigue life, and the greater the magnetic field strength Hmax The above rule is more obvious ( figure 1 ), however, it cannot distinguish the stable growth of the fatigue crack stage I from the rapid growth stage II

Similarly, the inventor of the present application uses the sine wave voltage signal to excite the Q235 steel to obtain the change of the root mean square voltage of the MAE signal with the fatigue cycle, and also draws a similar rule ( figure 2 ), and it is also impossible to distinguish between the two stages of stable growth of fatigue cracks in stage I and rapid growth in stage II

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