Method for non-linear ultrasonic online detection of early fatigue damage to metal material

Abstract

A method for the non-linear ultrasonic online detection of early fatigue damage to a metal material belongs to the field of nondestructive detection. The method comprises the following steps: determining an excitation signal parameter according to the thickness of a tested piece and inputting the parameter to an arbitrary function generator to generate a sound signal; determining a threshold value of an acoustic emission instrument according to the amplitude of a no-load noise signal; performing fatigue loading on the tested piece, continuously detecting an acoustic emission signal in real time with an acoustic emission sensor, amplifying the acoustic emission signal, inputting the acoustic emission signal into the acoustic emission instrument, and judging ring with the acoustic emission instrument when the amplitude of the acoustic emission signal exceeds the preset the threshold value of the acoustic emission instrument; detecting a non-linear ultrasonic signal at equal time interval if the acoustic emission instrument does not display the ring or the times of the continuous ring is not more than an empirical value; and stopping detection if the displayed ring times is more than the empirical value, because fatigue cracks are generated and develop. On the basis of non-linear ultrasonic nondestructive detection, the method of the invention introduces acoustic emission technique, so the method does not make incorrect judgment when detecting the early fatigue damage to the metal material and realizes continuous online detection.

Description

technical field [0001] The invention relates to a method for non-destructive detection of fatigue early damage of metal materials by using nonlinear ultrasonic and acoustic emission technology, and belongs to the field of non-destructive detection. Background technique [0002] Fracture failure of mechanical parts due to fatigue is a very common phenomenon. It is estimated that more than 70% of mechanical parts failures are caused by fatigue damage. Under the action of external loads, the fatigue life of metal parts can generally be divided into three stages: the early degradation of mechanical properties (a large number of dislocation groups and the formation of resident slip bands and microcracks), the initiation of damage and the formation of microcracks. Accumulation (nucleation and growth of microcracks and generation of macrocracks) and final fracture failure. For well-designed structural elements, the first stage generally accounts for 60% to 80% of the overall fatig...

AI Technical Summary

Problems solved by technology

However, due to the large number of fatigue cracks in the late stage of fatigue, β decreases instead, and the dispersion increases. If the nonlinear ultrasonic method is used alone to detect the early damage of fatigue, it is easy to misjudgment

As a "passive" flaw detection technology, acoustic emission technology can continuously monitor fatigue cracks through the analysis and processing of fatigue acoustic emission signals, but acoustic emission technology cannot detect the early fatigue damage of metal materials before fatigue cracks appear.

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