CN115586255A - Quantitative detection method for subsurface inclined cracks based on laser ultrasonic transmission surface waves - Google Patents

Quantitative detection method for subsurface inclined cracks based on laser ultrasonic transmission surface waves Download PDF

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CN115586255A
CN115586255A CN202211252023.2A CN202211252023A CN115586255A CN 115586255 A CN115586255 A CN 115586255A CN 202211252023 A CN202211252023 A CN 202211252023A CN 115586255 A CN115586255 A CN 115586255A
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laser
subsurface
ultrasonic
workpiece
crack
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卢科青
杨大兴
王传勇
王文
陈占锋
杨贺
居冰峰
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Hangzhou Dianzi University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/041—Analysing solids on the surface of the material, e.g. using Lamb, Rayleigh or shear waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/028—Material parameters
    • G01N2291/0289—Internal structure, e.g. defects, grain size, texture

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Abstract

The invention discloses a quantitative detection method for subsurface inclined cracks based on laser ultrasonic transmission surface waves, which comprises the following steps: s1, respectively placing a pulse laser probe and a laser vibration meter probe on two sides of a sub-surface inclined crack of a workpiece; s2, emitting pulse laser to irradiate the workpiece by a pulse laser probe, exciting a super surface acoustic wave on the surface of the workpiece, and measuring a transmission surface wave signal TR of the surface wave transmitted through the subsurface inclined crack by using a laser vibration meter; s3, extracting a first peak t of the transmitted surface wave signal TR R1 Time t corresponding to the second trough R2 And time t corresponding to the third trough R3 (ii) a S4, utilizing the extracted time t R1 、t R2 And t R3 And calculating to obtain the length l of the subsurface inclined crack. The method effectively improves the detection precision of the subsurface cracks with different inclination angles, particularly the detection precision of small-angle inclination.

Description

Quantitative detection method for subsurface inclined cracks based on laser ultrasonic transmission surface waves
Technical Field
The invention relates to the technical field of ultrasonic nondestructive testing, in particular to a quantitative detection method for subsurface inclined cracks based on laser ultrasonic transmission surface waves, which relates to non-contact measurement and ultrasonic nondestructive testing.
Background
With the development of industrial modernization, various materials and devices manufactured by utilizing advanced precision/ultra-precision processing technology are widely applied to various fields of aerospace, energy and chemical engineering, transportation, weaponry, biomedicine and the like. In the manufacturing and service processes of the materials and devices, the materials and the devices are influenced by severe environments such as high temperature, high pressure, high load, corrosion and the like, and certain microcracks are easily caused under the surfaces of the materials. These cracks, which are sub-surface cracks, are about a hundred microns deep below the surface and have a size of between a few microns and tens of microns. If subsurface cracks are not identified and necessary measures are taken in a timely and effective manner, the subsurface cracks may develop further and eventually lead to fatigue failure of the device. The presence of subsurface cracks severely reduces the reliability and stability of the material device and may even lead to dangerous and damaging accidents.
The laser ultrasonic technology is a new nondestructive testing technology, and the material defects are detected by generating ultrasonic waves of various modes through laser excitation. The laser ultrasonic technology has the advantages of accuracy and reliability of conventional ultrasonic detection results, high sensitivity, low cost and the like, has the characteristics of non-contact, rich wave modes, wide frequency band and the like, shows good performance in the aspect of nondestructive detection of defects, and is increasingly concerned by numerous experts and scholars. At present, in the field of laser ultrasonic detection, a mature method is provided for detecting and positioning subsurface cracks, and a plurality of scholars are studying vertical cracks, but the quantitative detection of the length of the subsurface inclined crack defect is difficult.
In the existing research, takao Tanaka et al have set up a set of laser ultrasonic detection system based on confocal fabry-perot interference method, regard carbon steel sample with internal defect as the study object, through analyzing the transmission longitudinal wave and transmission transverse wave signal, can detect the micro defect about 0.07 with the ultrasonic wavelength ratio, have very high sensitivity and resolution ratio, but can't accomplish quantitative detection. Thevar et al developed a set of laser ultrasound systems that could be remotely detected and used to detect adhesion defects in materials with very high acoustic attenuation and subsurface defects in new foam materials, but failed to achieve quantitative detection of subsurface defects. Coony obtains an ultrasonic signal time displacement amplitude signal by using an optical scanning method in a flaw detection test to realize defect detection on materials, but the method can only realize detection on subsurface defects and cannot realize quantitative detection.
Other existing nondestructive detection methods, such as infrared thermography nondestructive detection technology, utilize infrared light as a radiation source, the surface of a workpiece has differences in heat transferred to a deep layer due to defects or discontinuous internal structures, and further causes changes in a surface temperature field, and finally, the surface and internal defects of the workpiece are detected by thermal imaging. The radiographic inspection technique needs to penetrate a metal layer of a material in order to make a film photosensitive, but is accompanied by attenuation, and a radiation source of the radiographic inspection is easily worn and must be replaced periodically, and is not easy to carry, has high radioactivity and high cost, and has limitations such as specific sizes such as depth and width of a defect which cannot be judged by a signal. The eddy current detection technology is based on the electromagnetic induction principle, the defects of the conductive material are detected by the method commonly, and the depth and the width of the defects cannot be judged due to the fact that the method has large limitation, weak penetrating power and unstable sensitivity on the detected material.
The quantitative detection of the subsurface inclined crack defects is realized by adopting laser ultrasonic nondestructive testing, the relationship between crack defect parameters and processing parameters can be established, the optimization of the processing technology is realized, and the subsurface inclined crack defects can be conveniently removed by subsequent processing. However, there are few methods available for quantitative measurement of subsurface tilt crack lengths in existing non-destructive testing methods. In order to solve the above technical problems, chinese patent discloses application numbers as follows: 202111627531.X, entitled: a subsurface crack length quantitative detection method based on laser excitation surface waves detects subsurface cracks by using laser ultrasonic reflection waves, the detection precision is good when the inclination angle is about 90 degrees, but the relative error of length detection of the subsurface cracks is remarkably increased along with the reduction of the inclination angle of the subsurface cracks, and particularly for the subsurface cracks with the inclination angle smaller than 30 degrees, the relative error of length detection of the subsurface cracks even reaches more than 30 percent.
Disclosure of Invention
The invention provides a quantitative detection method for subsurface inclined cracks based on laser ultrasonic transmission surface waves, which effectively improves the detection precision of the subsurface cracks with different inclination angles.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a subsurface inclined crack quantitative detection method based on laser ultrasonic transmission surface waves comprises the following steps:
s1, respectively placing a pulse laser probe and a laser vibration meter probe on two sides of a sub-surface inclined crack of a workpiece;
s2, emitting pulse laser to irradiate the workpiece by a pulse laser probe, exciting a super surface acoustic wave on the surface of the workpiece, and measuring a transmission surface wave signal TR of the surface wave transmitted through the subsurface inclined crack by using a laser vibration meter;
s3, extracting a first peak t of a transmission surface wave signal TR R1 Time t corresponding to the second trough R2 And time t corresponding to the third trough R3 ；
S4, utilizing the extracted time t R1 、t R2 And t R3 And calculating to obtain the length l of the subsurface inclined crack, wherein the calculation method comprises the following steps:
Figure BDA0003888446300000031
wherein v is R Is the propagation velocity, v, of the ultrasonic surface wave on the surface of the workpiece S Working for ultrasonic transverse wavePropagation velocity of the member, v P The propagation speed of the ultrasonic longitudinal wave on the workpiece is shown.
Preferably, the excitation method of the ultrasonic surface wave is laser point source excitation, specifically, pulse laser emitted by a pulse laser probe is focused into point source laser through a convex lens, and the point source laser irradiates the surface of the workpiece and excites the ultrasonic surface wave.
Preferably, the excitation method of the ultrasonic surface wave is line source excitation, and specifically, a pulse laser probe emits pulse laser, the pulse laser is focused into line source laser through a cylindrical lens, the line source laser irradiates the surface of the workpiece, and the ultrasonic surface wave is excited.
Preferably, the subsurface crack is a rectangular crack, and the linear source laser is parallel to the axial direction of the subsurface crack.
Preferably, the propagation speed of the ultrasonic surface wave, the ultrasonic transverse wave and the ultrasonic longitudinal wave on the surface of the workpiece needs to be obtained by searching an ultrasonic velocity table in advance.
The invention has the following characteristics and beneficial effects:
1. the method is simple to operate and high in measurement accuracy, length information of the subsurface inclined crack can be quickly obtained by only one measurement, and the time cost of detection is reduced. 2. The invention is non-contact measurement, can realize on-line detection in the processing process and improve the detection efficiency. 3. Compared with the existing subsurface crack length detection method, the method has the advantage that the detection precision is obviously improved when the crack inclination angle is within 60 degrees. 4. The detection speed is high, the detection accuracy is high, and due to the non-contact detection characteristic, the method can be used for in-situ measurement in the machining process or quantitative detection of the length of the subsurface inclined crack in the extreme environment such as high temperature and high pressure, can be applied to any severe scene, and has a wide application range.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram of the detection state of the quantitative detection method for the subsurface inclined crack based on the laser ultrasonic transmission surface wave in the embodiment of the invention.
Fig. 2 is a graph of transmitted surface wave ultrasonic signals detected by a laser vibrometer.
In the figure, 1-workpiece, 2-subsurface inclined crack, 3-pulse laser probe, 4-laser vibrometer.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The present invention will be described in detail with reference to the accompanying drawings.
The invention relates to a quantitative detection method for subsurface inclined cracks based on laser ultrasonic transmission surface waves, which utilizes pulse laser focused into a point source to generate ultrasonic surface waves in a workpiece, surface waves transmit through the subsurface inclined cracks to generate transmission surface wave signals, the transmission surface wave signals are received through a laser vibration meter, and then the transmission wave signals are analyzed to realize the quantitative detection of the length of the subsurface inclined cracks of the workpiece.
The specific steps are as follows, as shown in figure 1:
respectively placing a pulse laser probe 3 and a laser vibration meter probe 4 on two sides of the subsurface inclined crack 2 in the workpiece 1;
a pulse laser probe 3 emits pulse laser to irradiate the workpiece 1, the surface of the workpiece is excited to generate a super surface acoustic wave, and a transmission surface wave signal TR of the surface wave transmitted through the subsurface inclined crack is measured by a laser vibration meter 4;
extracting a first peak t of a transmitted surface wave signal TR R1 Time t corresponding to the second trough R2 And time t corresponding to the third trough R3 ；
Using the time t of extraction R1 、t R2 、t R3 Calculating to obtain the sub-surface inclinationCrack length l. The calculation formula is as follows:
Figure BDA0003888446300000051
wherein v is R For the propagation velocity, v, of the surface acoustic wave on the surface of the workpiece to be measured S Is the propagation velocity, v, of ultrasonic transverse waves in a workpiece to be measured P The propagation speed of the ultrasonic longitudinal wave on the workpiece to be measured is adopted.
The effects of the invention were verified with specific measurement experiments as follows: the length of the subsurface inclined crack of an aluminum plate is detected by the method, the detected aluminum plate is 100mm long, 50mm wide and 10mm thick, and the subsurface inclined crack is arranged below the surface of a workpiece. A pulsed laser probe 3 is placed on one side of the crack for exciting the surface waves and a laser vibrometer probe 4 is placed on the other side of the crack for receiving the transmitted surface waves, as shown in fig. 1. The arrival times of the first and second characteristic valleys of the transmitted surface wave are extracted for calculating the sub-surface tilt crack length. In order to verify that the detection precision of the method is obviously improved compared with the original method when the crack inclination angle is less than 60 degrees, the pulse laser probe 3 and the laser vibration meter probe 4 are positioned at the same side of the crack, and the length of the subsurface inclined crack is detected by using the reflected surface wave.
The results of the measurements and their relative errors for this example are shown in the following table:
Figure BDA0003888446300000061
as can be seen from the table, the detection accuracy of the embodiment of the invention for the inclined subsurface crack is higher. Particularly, when the sub-surface crack inclination angle is smaller than 60 degrees, the method is adopted to carry out quantitative detection on the length of the sub-surface inclined crack, and compared with the original detection method, the detection precision is obviously improved. The method has the advantage of greatly improving the length detection of the subsurface inclined crack.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments, including the components, without departing from the principles and spirit of the invention, and still fall within the scope of the invention.

Claims (5)

1. A subsurface inclined crack quantitative detection method based on laser ultrasonic transmission surface waves is characterized by comprising the following steps:
s1, respectively placing a pulse laser probe and a laser vibration meter probe on two sides of a sub-surface inclined crack of a workpiece;
s2, emitting pulse laser to irradiate the workpiece by a pulse laser probe, exciting a super surface acoustic wave on the surface of the workpiece, and measuring a transmission surface wave signal TR of the surface wave transmitted through the subsurface inclined crack by using a laser vibration meter;
s3, extracting a first peak t of a transmission surface wave signal TR R1 Time t corresponding to the second trough R2 And time t corresponding to the third trough R3 ；
S4, utilizing the extracted time t R1 、t R2 And t R3 And calculating to obtain the length l of the subsurface inclined crack, wherein the calculation method comprises the following steps:
Figure FDA0003888446290000011
wherein v is R Is the propagation velocity, v, of the surface acoustic wave on the workpiece surface S Is the propagation velocity, v, of ultrasonic transverse waves in the workpiece P The propagation speed of the ultrasonic longitudinal wave on the workpiece is shown.
2. The quantitative detection method for the subsurface inclined crack based on the laser ultrasonic transmission surface wave as claimed in claim 1, wherein the excitation method of the ultrasonic surface wave is laser point source excitation, specifically, a pulse laser probe emits pulse laser, which is focused into point source laser through a convex lens, and the point source laser irradiates the surface of the workpiece and excites the super surface acoustic wave.
3. The method for quantitatively detecting the inclined subsurface crack based on the laser ultrasonic transmission surface wave as claimed in claim 1, wherein the excitation method of the ultrasonic surface wave is line source excitation, specifically, a pulse laser probe emits pulse laser, the pulse laser is focused into line source laser through a cylindrical lens, and the line source laser irradiates the surface of a workpiece and excites the ultrasonic surface wave.
4. The quantitative detection method for the subsurface inclined crack based on the laser ultrasonic transmission surface wave as claimed in claim 1, characterized in that the subsurface crack is a rectangular crack, and the line source laser is parallel to the axial direction of the subsurface crack.
5. The quantitative detection method for the subsurface inclined crack based on the laser ultrasonic transmission surface wave as claimed in claim 1, characterized in that the propagation speed of the ultrasonic surface wave, the ultrasonic transverse wave and the ultrasonic longitudinal wave on the surface of the workpiece needs to be obtained by searching an ultrasonic velocity table in advance.
CN202211252023.2A 2022-10-13 2022-10-13 Quantitative detection method for subsurface inclined cracks based on laser ultrasonic transmission surface waves Pending CN115586255A (en)

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