CN111650283B - Method for positioning residual stress peak value based on acoustic emission technology - Google Patents
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Abstract
The method for positioning the residual stress peak position based on the acoustic emission technology comprises the following steps: determining a planar quadrilateral area on a workpiece, which needs to be subjected to residual stress peak position testing; mounting an acoustic emission sensor; calibrating the acoustic emission instrument; recording background noise; carrying out an experiment; analyzing and processing the acoustic emission signal, and extracting the arrival time of the acoustic emission signal; the coordinates of the location of the residual stress peak are determined. The method has the advantages of capability of quickly positioning the position of the residual stress peak value and high positioning precision.
Description
Technical Field
The invention relates to the technical field of nondestructive testing, in particular to a method for positioning a residual stress peak value based on an acoustic emission technology.
Background
During the manufacturing process, the workpiece is affected by various process factors such as welding, casting, heat treatment, cutting, forging and the like, and forced assembly caused by inconsistent sizes can also occur during the assembly process, which can generate unnecessary residual stress in the workpiece, thereby reducing the static load strength and fatigue strength of the workpiece and accelerating the stress corrosion process of the workpiece, and also is an important factor for generating deformation and cracking of the workpiece. In addition, fatigue cracks are easily formed at the peak of the residual stress, so that the failure of the whole workpiece is caused, and the service life of the workpiece is influenced.
The current method for detecting residual stress mainly comprises the following steps: mechanical methods and physical detection methods. The mechanical method mainly comprises a small hole method, a slitting method, a grooving method and the like. The mechanical method for detecting residual stress has the working principle that the stress of a workpiece is released, and the workpiece needs to be locally separated or segmented, so that the workpiece can be damaged or destroyed to a certain extent. The physical detection method mainly includes an X-ray diffraction method, a neutron diffraction method, an ultrasonic method, and the like. The X-ray diffraction method for detecting the residual stress of the workpiece is based on elastic mechanics and X-ray diffraction crystallography theory, when the residual stress exists in a crystal material, elastic strain is inevitably corresponding to the residual stress, so that the local area of the material is deformed, and the relative position between atoms in the material is changed, so that the deformation is reflected on an X-ray diffraction map, the size and the distribution condition of the residual stress in the material can be determined by analyzing diffraction information, the X-ray diffraction method can detect the distribution state and the size of the residual stress on the surface of the workpiece, and can determine the peak value area of the residual stress on the surface, but the penetration depth of the X-ray diffraction method for metal is limited, and the surface residual stress can only be determined in a nondestructive mode, if the residual stress and the distribution of the depth layer are measured, the workpiece is damaged, and part of the residual stress is released and an additional stress field is possibly generated, so that the measurement precision is seriously influenced. The basic principle of neutron diffraction method for detecting residual stress of a workpiece is consistent with that of an X-ray method, but the penetration depth of neutrons is much larger than that of X-rays, so that the neutron diffraction method can be used for testing the residual stress of deeper layers of the workpiece. The principle of detecting the residual stress of the workpiece by an ultrasonic method is based on the acoustic elasticity theory, namely, the size of the residual stress in the workpiece is detected by utilizing the acoustic birefringence phenomenon in a stressed material. These methods are non-destructive and do not cause damage or destruction of the workpiece. However, whether the mechanical method or the physical detection method is just to obtain the residual stress at the test point, if the peak position of the residual stress in the workpiece needs to be obtained, the residual stress at a plurality of points on the workpiece needs to be tested, which greatly increases the cost of the test and causes great damage or damage to the workpiece in the case of the pinhole method.
In recent years, with the rapid development of modern industrial technologies, a new set of residual stress detection methods, such as nanoindentation, scanning electron-acoustic microscopy, raman spectroscopy, etc., has emerged. However, these detection methods are not really applied due to high equipment cost, complex conditions and imperfect test theory. The invention provides a residual stress peak value positioning method based on an acoustic emission technology, which belongs to a lossless residual stress peak value positioning method and aims to solve the problem that no better residual stress peak value positioning method exists at present to determine the residual stress peak value position in a workpiece. When the residual stress peak position locating method based on the acoustic emission technology is used for locating the residual stress peak position in the workpiece, the measured time difference is simply calculated, and the locating result can be obtained without measuring the sound velocity, so that the error generated in the sound velocity measurement is avoided, and the locating precision of the time difference locating method based on the acoustic emission technology is improved.
Disclosure of Invention
In order to solve the problem that a better residual stress peak position positioning method for determining the residual stress peak position in a workpiece does not exist at present, the invention provides a residual stress peak positioning method based on an acoustic emission technology, and belongs to a lossless residual stress peak position positioning method. When the residual stress peak value positioning method based on the acoustic emission technology is used for positioning the residual stress peak value position in the workpiece, the measured time difference is simply calculated, the positioning result can be obtained without measuring the sound velocity, and the error generated in the sound velocity measurement can be avoided.
The method for positioning the residual stress peak position based on the acoustic emission technology comprises the following steps:
(1) Determining a planar quadrilateral area on the workpiece, which needs to be subjected to residual stress peak position testing: firstly, simulating the machining process of a workpiece by a finite element numerical simulation technology, acquiring the distribution state of the residual stress on the surface of the workpiece, acquiring a region where the larger residual stress is located, and preliminarily acquiring the peak position of the residual stress; secondly, determining a planar quadrilateral area including the position of the primarily obtained residual stress peak value, namely a test area; then, the surface of the test area is polished, so that the surface roughness of the workpiece is reduced, and the acoustic emission sensor can be ensured to be tightly attached to the surface of the workpiece, so that acoustic emission signals can be better collected;
(2) Installation of the acoustic emission sensor: uniformly coating a coupling agent at the four vertex positions of the plane quadrangle, and then bonding the four acoustic emission sensors at the four vertex positions of the plane quadrangle by adopting a glue bonding mode;
(3) Calibrating an acoustic emission instrument: connecting the output end of the acoustic emission sensor with the input end of a four-channel acoustic emission instrument by using a signal cable, then switching on a power supply of the acoustic emission instrument, setting relevant parameters of the acoustic emission instrument and calibrating the relevant parameters;
the related parameters of the acoustic emission instrument comprise sampling frequency, sampling number of each group, signal threshold value, pulse frequency, RMS time constant and the like.
(4) Record background noise: continuously running for 15min after the calibration of the acoustic emission instrument is finished, and acquiring and recording background noise for use in subsequent processing of test data;
(5) Carrying out an experiment: acquiring an acoustic emission signal through an acoustic emission sensor, and transmitting the detected acoustic emission signal to an acoustic emission instrument;
(6) Analyzing and processing the acoustic emission signal, and extracting the arrival time of the acoustic emission signal: firstly, processing the acoustic emission signals detected by the acoustic emission sensors through the acoustic emission instrument, removing the noise signals in the detected acoustic emission signals by using the background noise recorded in the step 4, then respectively extracting the arrival time of the acoustic emission signals received by the four acoustic emission sensors, and recording the arrival time of the acoustic emission signals received by the acoustic emission sensor 1 as t 1 And the arrival time of the acoustic emission signal received by the acoustic emission sensor 2 is recorded as t 2 And the arrival time of the acoustic emission signal received by the acoustic emission sensor 3 is recorded as t 3 And the arrival time of the acoustic emission signal received by the acoustic emission sensor 4 is recorded as t 4 ；
(7) Determining the coordinates of the residual stress peak position: the arrival time t of the acoustic emission signal received by the acoustic emission sensor 1 1 For reference, the acoustic emission instrument can measure the time difference of the acoustic emission signals received by each acoustic emission sensor by using the 1 st threshold crossing technology as follows: Δ t 2 ＝t 2 -t 1 ，Δt 3 ＝t 3 -t 1 ，Δt 4 ＝t 4 -t 1 Then utilizing time difference delta t of acoustic emission signal received by acoustic emission sensor 2 ，Δt 3 ，Δt 4 And determining the specific coordinate of the residual stress peak position on the workpiece.
Further, the method for positioning the position of the residual stress peak based on the acoustic emission technology is characterized in that: the plane quadrangle is a square; the side length of the square is 2a.
Or, the method for positioning the residual stress peak position based on the acoustic emission technology is characterized in that: the plane quadrangle is rectangular; the rectangle is 2a long and 2b wide.
In the step 2, the four acoustic emission sensors are arranged around the position of the residual stress peak preliminarily determined by the workpiece in a square form, the side length of the square is 2a, and a plane rectangular coordinate system is established by taking the symmetrical center of the square as an origin; in the step 3, a four-channel acoustic emission instrument and four acoustic emission sensors matched with the four-channel acoustic emission instrument are selected to be connected, and the acoustic emission sensors are numbered and respectively marked as an acoustic emission sensor 1, an acoustic emission sensor 2, an acoustic emission sensor 3 and an acoustic emission sensor 4.
When the planar quadrangle is square, the derivation process of determining the coordinates of the residual stress peak position in step 7 is as follows:
(a-x) 2 +(a+y) 2 ＝v 2 (t 1 +Δt 2 ) 2 (2)
(a-x) 2 +(a-y) 2 ＝v 2 (t 1 +Δt 3 ) 2 (3)
(a+x) 2 +(a-y) 2 ＝v 2 (t 1 +Δt 4 ) 2 (4)
subtracting the expressions (2) to (4) from the expression (1) to obtain:
adding formula (5) to formula (7) and combining formula (6) gives:
comparing formula (5) with formula (7):
comparing formula (1) with formula (5):
order to
Equation (10) is simplified to:
obtaining by solution:
and in the step 2, the four acoustic emission sensors are arranged around the position of the residual stress peak primarily determined and obtained by the workpiece in a rectangular mode, the length of the rectangle is 2a, the width of the rectangle is 2b, and a plane rectangular coordinate system is established by taking the symmetric center of the rectangle as the origin.
When the planar quadrangle is a rectangle, the derivation process of the coordinates for determining the position of the residual stress peak in step 7 is as follows:
(a-x) 2 +(b+y) 2 ＝v 2 (t 1 +Δt 2 ) 2 (2)
(a-x) 2 +(b-y) 2 ＝v 2 (t 1 +Δt 3 ) 2 (3)
(a+x) 2 +(b-y) 2 ＝v 2 (t 1 +Δt 4 ) 2 (4)
subtracting the expressions (2) to (4) from the expression (1) to obtain:
adding formula (5) to formula (7) and combining formula (6) gives:
comparing formula (5) with formula (7):
comparing formula (1) with formula (5):
order to
Equation (10) is simplified to:
obtaining by solution:
through the mathematical derivation, only the time difference delta t of each acoustic emission sensor receiving the acoustic emission signal is needed 2 ，Δt 3 ，Δt 4 And (5) substituting the formula (12) to determine the specific coordinates (x, y) of the residual stress peak position on the workpiece.
Further, the method for positioning the position of the residual stress peak based on the acoustic emission technology is characterized in that: when the plane quadrangle is a square, the specific coordinate (x, y) of the residual stress peak position on the workpiece is
Further, the method for positioning the position of the residual stress peak based on the acoustic emission technology is characterized in that: when the plane quadrangle is a rectangle, the specific coordinate (x, y) of the residual stress peak position on the workpiece is
The technical conception of the invention is as follows: the method comprises the steps of positioning the position of a residual stress peak value through an acoustic emission technology, in order to avoid errors caused by acoustic velocity measurement, acquiring the time difference of acoustic emission signals received by each acoustic emission sensor under the condition of assuming that the acoustic velocity is known, then eliminating the unknown quantity of the acoustic velocity through simple mathematical derivation, and representing the specific coordinates of the position of the residual stress peak value on a workpiece by using a mathematical formula only containing the time difference.
The invention has the following beneficial effects:
1. the residual stress peak value positioning method based on the acoustic emission technology is used for a four-channel acoustic emission instrument with a threshold crossing time difference measuring system, the residual stress peak value positioning method provided by the method is used, only the measured time difference needs to be simply calculated, the positioning result can be obtained without measuring the sound velocity, the error generated in the sound velocity measuring process is avoided, and therefore the positioning precision of the time difference positioning method based on the acoustic emission technology is improved.
2. The method for positioning the residual stress peak position based on the acoustic emission technology is simple in arrangement method of the acoustic emission sensors in the positioning process, can be adjusted according to the size of the test area, and is simple and convenient to operate.
3. The method for positioning the residual stress peak value based on the acoustic emission technology without measuring the acoustic velocity is not only suitable for positioning the peak value position of the residual stress, but also suitable for positioning the position of a crack in a workpiece or the positions of other acoustic emission sources, and has good universality.
Drawings
FIG. 1 is a schematic flow chart of a method for locating a residual stress peak position based on an acoustic emission technology.
FIG. 2 is a schematic diagram of a method and an apparatus for locating a peak position of residual stress based on an acoustic emission technique.
FIG. 3 is a schematic diagram of an acoustic emission sensor arranged in a square pattern.
FIG. 4 is a schematic view of an acoustic emission sensor arranged in a rectangular pattern.
Detailed Description
The invention is further illustrated with reference to the accompanying drawings:
the method for positioning the residual stress peak position based on the acoustic emission technology comprises the following steps:
(1) Determining a planar quadrilateral area on the workpiece, which needs to be subjected to residual stress peak position testing: firstly, simulating the machining process of a workpiece by a finite element numerical simulation technology to obtain the distribution state of the residual stress on the surface of the workpiece, obtaining a region where the larger residual stress is located, and preliminarily obtaining the peak position of the residual stress; secondly, determining a planar quadrilateral area including the position of the primarily obtained residual stress peak value, namely a test area; then, the surface of the test area is polished, so that the surface roughness of the workpiece is reduced, and the acoustic emission sensor can be ensured to be tightly attached to the surface of the workpiece, so that acoustic emission signals can be better collected;
(2) Installation of the acoustic emission sensor: uniformly coating a coupling agent at the four vertex positions of the planar quadrangle, and then bonding the four acoustic emission sensors at the four vertex positions of the planar quadrangle by adopting a glue bonding mode;
(3) Calibrating an acoustic emission instrument: connecting the output end of the acoustic emission sensor with the input end of a four-channel acoustic emission instrument by using a signal cable, then switching on a power supply of the acoustic emission instrument, setting relevant parameters of the acoustic emission instrument and calibrating the relevant parameters;
the acoustic emission instrument is calibrated, and the purpose of the acoustic emission instrument is as follows: firstly, checking whether the parameter setting of the instrument is reasonable; secondly, whether the installation (mainly the coupling condition) of the acoustic emission sensor is reliable is checked, and two modes are provided for the calibration of a common instrument: firstly, a pulse signal generated by an instrument is used for calibration; secondly, the lead-breaking signal is used for calibration, the first mode is used for checking whether the parameter setting of the instrument is reasonable, and the latter mode is used for confirming whether certain specific areas can be detected.
The related parameters of the acoustic emission instrument comprise sampling frequency, sampling number of each group, signal threshold value, pulse frequency, RMS time constant and the like.
(4) Record background noise: continuously running for 15min after the calibration of the acoustic emission instrument is finished, and acquiring and recording background noise for use in subsequent processing of test data;
(5) Carrying out an experiment: acquiring an acoustic emission signal through an acoustic emission sensor, and transmitting the detected acoustic emission signal to an acoustic emission instrument;
(6) Analyzing and processing the acoustic emission signal, and extracting the arrival time of the acoustic emission signal: firstly, processing the acoustic emission signals detected by the acoustic emission sensors through the acoustic emission instrument, removing the noise signals in the detected acoustic emission signals by using the background noise recorded in the step 4, then respectively extracting the arrival time of the acoustic emission signals received by the four acoustic emission sensors, and recording the arrival time of the acoustic emission signals received by the acoustic emission sensor 1 as t 1 And the arrival time of the acoustic emission signal received by the acoustic emission sensor 2 is recorded as t 2 When the acoustic emission sensor 3 receives the arrival of the acoustic emission signalIs marked by t 3 And the arrival time of the acoustic emission signal received by the acoustic emission sensor 4 is recorded as t 4 ；
(7) Determining the coordinates of the residual stress peak position: the arrival time t of the acoustic emission signal received by the acoustic emission sensor 1 1 For reference, the acoustic emission instrument can measure the time difference of the acoustic emission signals received by each acoustic emission sensor by using the 1 st threshold crossing technology as follows: Δ t 2 ＝t 2 -t 1 ，Δt 3 ＝t 3 -t 1 ，Δt 4 ＝t 4 -t 1 Then utilizing time difference delta t of acoustic emission signal received by acoustic emission sensor 2 ，Δt 3 ，Δt 4 And determining the specific coordinate of the residual stress peak position on the workpiece.
Further, the method for positioning the position of the residual stress peak based on the acoustic emission technology is characterized in that: the plane quadrangle is a square; the side length of the square is 2a.
Or, the method for positioning the residual stress peak position based on the acoustic emission technology is characterized in that: the plane quadrangle is a rectangle; the rectangle is 2a long and 2b wide.
Because the traditional time difference positioning method needs to give a sound velocity or actually measure the sound velocity in advance, and the measurement of the sound velocity is influenced by factors such as environmental noise and the like, a large error is brought to a positioning result 2 ，Δt 3 ，Δt 4 So that only the time difference deltat of the received signals of each acoustic emission sensor needs to be acquired 2 ，Δt 3 ，Δt 4 The specific coordinates of the location of the residual stress peak on the workpiece can be determined.
In the step 2, the four acoustic emission sensors are arranged around the position of the residual stress peak preliminarily determined by the workpiece in a square form, the side length of the square is 2a, and a plane rectangular coordinate system is established by taking the symmetrical center of the square as an origin; in the step 3, a four-channel acoustic emission instrument and four acoustic emission sensors matched with the four-channel acoustic emission instrument are selected to be connected, and the acoustic emission sensors are numbered and respectively marked as an acoustic emission sensor 1, an acoustic emission sensor 2, an acoustic emission sensor 3 and an acoustic emission sensor 4.
When the planar quadrangle is square, the derivation process of determining the coordinates of the residual stress peak position in step 7 is as follows:
(a-x) 2 +(a+y) 2 ＝v 2 (t 1 +Δt 2 ) 2 (2)
(a-x) 2 +(a-y) 2 ＝v 2 (t 1 +Δt 3 ) 2 (3)
(a+x) 2 +(a-y) 2 ＝v 2 (t 1 +Δt 4 ) 2 (4)
subtracting the expressions (2) to (4) from the expression (1) to obtain:
adding formula (5) to formula (7) and combining formula (6) gives:
comparing formula (5) with formula (7):
comparing formula (1) with formula (5):
order to
Equation (10) is simplified to:
obtaining by solution:
and in the step 2, the four acoustic emission sensors are arranged around the position of the residual stress peak primarily determined and obtained by the workpiece in a rectangular mode, the length of the rectangle is 2a, the width of the rectangle is 2b, and a plane rectangular coordinate system is established by taking the symmetric center of the rectangle as the origin.
When the planar quadrangle is a rectangle, the derivation process of the coordinates for determining the position of the residual stress peak in step 7 is as follows:
(a-x) 2 +(b+y) 2 ＝v 2 (t 1 +Δt 2 ) 2 (2)
(a-x) 2 +(b-y) 2 ＝v 2 (t 1 +Δt 3 ) 2 (3)
(a+x) 2 +(b-y) 2 ＝v 2 (t 1 +Δt 4 ) 2 (4)
subtracting the expressions (2) to (4) from the expression (1) to obtain:
adding formula (5) to formula (7) and combining formula (6) gives:
comparing formula (5) with formula (7):
comparing formula (1) with formula (5):
order to
Equation (10) is simplified to:
obtaining by solution:
through the mathematical derivation, only the time difference delta t of each acoustic emission sensor receiving the acoustic emission signal is needed 2 ，Δt 3 ，Δt 4 And (5) substituting the formula (12) to determine the specific coordinates (x, y) of the residual stress peak position on the workpiece.
Further, the method for positioning the position of the residual stress peak based on the acoustic emission technology is characterized in that: when the plane quadrangle is a square, the specific coordinate (x, y) of the residual stress peak position on the workpiece is
Further, the method for positioning the position of the residual stress peak based on the acoustic emission technology is characterized in that: when the plane quadrangle is a rectangle, the specific coordinate (x, y) of the residual stress peak position on the workpiece is
The embodiments described in this specification are merely illustrative of implementations of the inventive concept and the scope of the present invention should not be considered limited to the specific forms set forth in the embodiments but rather by the equivalents thereof as may occur to those skilled in the art upon consideration of the present inventive concept.
Claims (5)
1. The method for positioning the residual stress peak value based on the acoustic emission technology is characterized by comprising the following steps: the method comprises the following steps:
(1) Determining a planar quadrilateral area on the workpiece, which needs to be subjected to residual stress peak position testing: firstly, simulating the machining process of a workpiece by a finite element numerical simulation technology to obtain the distribution state of the residual stress on the surface of the workpiece, obtaining a region where the larger residual stress is located, and preliminarily obtaining the peak position of the residual stress; secondly, determining a planar quadrilateral area including the position of the primarily obtained residual stress peak value, namely a test area; then, the surface of the test area is polished, so that the surface roughness of the workpiece is reduced, and the acoustic emission sensor can be ensured to be tightly attached to the surface of the workpiece, so that acoustic emission signals can be better collected;
(2) Installation of the acoustic emission sensor: uniformly coating a coupling agent at the four vertex positions of the planar quadrangle, and then bonding the four acoustic emission sensors at the four vertex positions of the planar quadrangle by adopting a glue bonding mode;
(3) Calibrating an acoustic emission instrument: connecting the output end of the acoustic emission sensor with the input end of a four-channel acoustic emission instrument by using a signal cable, then switching on a power supply of the acoustic emission instrument, setting relevant parameters of the acoustic emission instrument and calibrating the relevant parameters;
(4) Record background noise: continuously running for 15min after the calibration of the acoustic emission instrument is finished, and acquiring and recording background noise for use in subsequent processing of test data;
(5) Carrying out an experiment: acquiring an acoustic emission signal through an acoustic emission sensor, and transmitting the detected acoustic emission signal to an acoustic emission instrument;
(6) Analyzing and processing the acoustic emission signal, and extracting the arrival time of the acoustic emission signal: firstly, the acoustic emission signals detected by the acoustic emission sensor are processed by the acoustic emission instrumentAnd eliminating the noise signals in the detected acoustic emission signals by using the background noise recorded in the step 4, then respectively extracting the arrival time of the acoustic emission signals received by the four acoustic emission sensors, and recording the arrival time of the acoustic emission signals received by the acoustic emission sensor 1 as t 1 And the arrival time of the acoustic emission signal received by the acoustic emission sensor 2 is recorded as t 2 And the arrival time of the acoustic emission signal received by the acoustic emission sensor 3 is recorded as t 3 And the arrival time of the acoustic emission signal received by the acoustic emission sensor 4 is recorded as t 4 ；
(7) Determining the coordinates of the residual stress peak position: the arrival time t of the acoustic emission signal received by the acoustic emission sensor 1 1 For reference, the acoustic emission instrument can measure the time difference of the acoustic emission signals received by each acoustic emission sensor by using the 1 st threshold crossing technology as follows: Δ t 2 ＝t 2 -t 1 ，Δt 3 ＝t 3 -t 1 ，Δt 4 ＝t 4 -t 1 Then utilizing time difference delta t of acoustic emission signal received by acoustic emission sensor 2 ，Δt 3 ，Δt 4 And determining the specific coordinate of the residual stress peak position on the workpiece.
2. The method of locating the position of a peak of residual stress based on acoustic emission technology as claimed in claim 1, wherein: the plane quadrangle is a square; the side length of the square is 2a.
3. The method of locating the position of a peak of residual stress based on acoustic emission technology as claimed in claim 1, wherein: the plane quadrangle is a rectangle; the rectangle is 2a long and 2b wide.
4. The method of locating the position of a peak of residual stress based on acoustic emission technology as claimed in claim 1, wherein: when the plane quadrangle is a square, the specific coordinate (x, y) of the residual stress peak position on the workpiece is
5. The method of locating the position of a peak of residual stress based on acoustic emission technology as claimed in claim 1, wherein: when the plane quadrangle is a rectangle, the specific coordinate (x, y) of the residual stress peak position on the workpiece is
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| CN109182727A (en) * | 2018-09-10 | 2019-01-11 | 上海海事大学 | A kind of Vibration Aging Process parameter determination system and method based on acoustic emission |
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