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

A nonlinear ultrasonic and metal material technology, applied in the field of non-destructive testing, can solve the problems that the acoustic emission technology cannot detect the early fatigue damage of metal materials, is prone to misjudgment, and increases the dispersion, and achieves the effect of continuous online testing.

Inactive Publication Date: 2010-08-18
BEIJING UNIV OF TECH
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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

Method used

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

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Embodiment Construction

[0035] Combine below Figure 1 to Figure 5 This embodiment will be described in detail.

[0036] like image 3 As shown, the tested piece in this experimental example is an AZ31 magnesium alloy dog ​​bone plate with a thickness of 7.5mm and a length of 150mm. The density is 1770kg / m 3, the longitudinal wave velocity is 5763m / s. The yield limit is 199MPa, and the strength limit is 259MPa.

[0037] 1) According to the center frequency of the excitation sensor, the excitation signal frequency is determined to be 5MHz. In order to reduce the harmonic interference generated by the instrument and random factors, the maximum number of cycles that the specimen can accommodate in the thickness direction without overlapping with the received signal is taken as the sinusoidal pulse train signal number of cycles, such as Figure 4 (a) shown. A pair of Panametrics narrowband PZT ultrasonic probes with center frequencies of 5MHz and 10MHz are used as excitation and reception transduce...

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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...

Claims

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Application Information

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IPC IPC(8): G01N29/14
Inventor 吴斌颜丙生李佳锐何存富
Owner BEIJING UNIV OF TECH
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