CN105699486A - Method for detecting bevel surface cracking inclination angle and depth - Google Patents

Abstract

A method for detecting bevel surface cracking inclination angle and depth is provided.Surface cracking are in two forms, vertical surface cracking and bevel surface cracking, and the two forms of surface cracking are generally present in practical industrial structures.Surface cracking may be in an open state, a closed state or in a state between them, this makes ultrasonic detection more difficult and detection result reliability reduced.The invention aims to provide a detection, wherein according to bevel surface cracking characteristics of a test piece, a linear focusing ultrasonic transducer is used to perform horizontal step measurement to determine a propagation path of bevel surface cracking reflected echo, so that the transducer may measure inclination angle and depth of bevel surface cracking in the test piece more accurately.The method has the following advantages that inclination angle and depth of bevel surface cracking in the test piece is accurately measured; no destruction is caused to the test piece structure.

Description

A kind of detection method of inclination surface crack inclination angle degree and the degree of depth

Technical field

The invention belongs to field of ultrasonic nondestructive detection, be specifically related to a kind of detection method to inclination surface crack inclination angle degree and the degree of depth。

Background technology

The Non-Destructive Testing of crackle is always up the important topic of commercial Application and scientific research, particularly face crack, owing to its occurrence probability is high, the hazardness of structural safety is big, therefore, a kind of science of development, reliable method and technology, it is achieved the detection of face crack and the measurement of crack depth, be the target that is continually striving to for a long time of academia。Face crack has two kinds of forms, and one is vertical surface crackle, and another kind is inclination surface crackle, two kinds of face crack equal ubiquities in actual industrial structure。Face crack may be at opening, close or different conditions therebetween, further increases the difficulty of ultrasound examination, reduces the reliability of testing result。The purpose of Non-Destructive Testing is in that: (a) detects the existence of face crack；B () measures the degree of depth and the shape of face crack。A the work of () item is easier to, had many methods and technology it is achieved that the work of (b) item is then extremely difficult, be still in academic research the difficult problem failing to be fully solved so far。

Measurement currently for face crack shape Yu the degree of depth has some ready-made modes, and such as the metering system of surface wave or surface wave diffraction with scattering, but feasibility and accuracy yet suffer from very big problem。It is an object of the invention to for the inclination surface crack (including angle of inclination and the degree of depth) in test specimen, adopt line focus ultrasonic transducer that test specimen is carried out horizontal direction stepping measurement, determine the propagation path of inclination surface crack deflection echo, make it possible to measure more accurately angle of inclination and the degree of depth of inclination surface crack defect。

Summary of the invention

The invention aims to solve the test problems of inclination surface crack (including angle of inclination and the degree of depth) in material, it is proposed to the detection method of a kind of crack inclination angle degree of inclination surface accurately and the degree of depth。

To achieve these goals, this method have employed following scheme:

Step 1): establish the formula calculating inclination surface crack inclination angle degree and the degree of depth

Fig. 1 is the detection schematic diagram of inclination surface crack inclination angle degree and the degree of depth, the propagation path of inclination surface crack deflection echo is that inclination surface crackle the beam path returned by original route are arrived in vertical transmission, can calculate the tilt angle theta of inclination surface crackle according to equation below_f:

${\mathrm{\θ}}_f={\sin }^{-1}\left(\frac{V_S\×\mathrm{\Δ}t}{2\×\mathrm{\Δ}z}\right)---\left(0\right)$

Wherein: V_SFor the longitudinal wave velocity of detected test specimen, Δ z is the displacement of X-direction line focus ultrasonic transducer, and Δ t is the inclination surface crack deflection echo time variable quantity after transducer moves Δ z。

After trying to achieve the angle of inclination of inclination surface crackle, then inclination surface crack depth h immediately below ultrasonic transducer center:

$h=\frac{V_S\×(t_f-t_D)}{2{\mathrm{cos\θ}}_f}---\left(0\right)$

Wherein: t_fFor the inclination surface crack deflection echo time that transducer receives, t_DFor the test specimen upper surface direct reflection echo time that transducer receives。

Step 2): test system building

In order to facilitate X-direction stepping measurement, build a set of test system carrying out horizontal stepping measurement, as shown in Figure 2。This test system specifically includes that sample (1), tank (2), transducer (3), X-axis mobile platform (4), pulse excitation/receiving instrument (5), oscillograph (6), gpib bus (7), PXI general control system (8), shift servo motor (9)。Wherein, it is mounted below transducer (3) at X-axis mobile platform (4), transducer (3) is connected with pulse excitation/receiving instrument (5), pulse excitation/receiving instrument (5) is connected with oscillograph (6), oscillograph (6) is connected with PXI general control system (8) by gpib bus (7), and PXI general control system (8) is connected with shift servo motor (9)。Being filled with water in described tank (2), sample (1) is placed on the bottom of tank (2)。

Step 3): start position data collection

Being placed in by test specimen containing inclination surface crackle below line focus ultrasonic transducer, transducer is positioned at the left side of test specimen。Pulse excitation/receiving instrument (5) is converted to reception state after sending the pulse that bandwidth is 10-50MHz, after receiving reflected signal, is transmitted by signal into oscillograph (6), and oscillographic sample frequency is f_s, f_sFor 0.5-5GHz, sampling number is N_s, N_sSpan be 10000-100000 point。After oscillographic low-pass filtering, it is stored in PXI general control system (8) by gpib bus (7)。

Step 4): X-direction stepping measurement

Transducer horizontal direction is moved a distance, delta z₀, Δ z₀Span be 0.5-1mm, to be moved complete laggard row data acquisition, sample frequency is f_s, sampling number is N_s。Transducer level is moved right after terminating Δ z by collection again₀Carrying out data acquisition, so move in circles, the span of displacement z, z is 15-100mm altogether, therefore will obtain M group voltage data, and M is by z and Δ z₀Together decide on, for 15-200 group。

Step 5): inclination surface crackle echo time matching

First echo that oscillograph receives is the direct reflection echo of test specimen upper surface, because inclination surface crackle is above test specimen bottom surface, so second echo is inclination surface crack deflection echo, and then determine the reflection echo time of upper surface and inclination surface crackle during diverse location。

Step 6): inclination surface crack inclination angle degree calculates

Longitudinal wave velocity V by transducer moving displacement Δ z in X direction, inclination surface crack deflection echo time variable quantity and test specimen_SBring formula (1) into, the angle of inclination of inclination surface crackle can be tried to achieve。

Step 7): inclination surface crack depth calculates

When transducer is positioned at a certain optional position above inclination surface crackle, the existing upper surface reflection echo of reflection echo signal has again inclination surface crack deflection echo, by upper surface and inclination surface crackle echo time t_DWith t_f, the longitudinal wave velocity V of test specimen_STilt angle theta with inclination surface crackle_fBring formula (2) into, the degree of depth of inclination surface crackle immediately below transducer center can be tried to achieve。

The invention have the advantages that 1) inclination surface crack inclination angle degree is accurate with depth survey in test specimen；2) test specimen structure is not carried out any destruction。

Accompanying drawing explanation

The detection schematic diagram of Fig. 1 inclination surface crack inclination angle degree and the degree of depth；

The horizontal stepping measurement system schematic of Fig. 2；

Fig. 3 original position time domain beamformer；

0 ° of inclination surface crack deflection echo time domain waveform stacking chart of Figure 41。

In figure: 1, sample, 2, tank, 3, transducer, 4, X-axis mobile platform, 5, pulse excitation/receiving instrument, 6, oscillograph, 7, gpib bus, 8, PXI general control system, 9, shift servo motor。

Detailed description of the invention

Below in conjunction with concrete example, present disclosure is described in further detail:

Step 1): establish inclination surface crack inclination angle degree and depth calculation formula

Working method is that transducer inspires ultrasonic signal, and coupled dose of water propagates test specimen upper surface, occurs refraction to propagate inclination surface crackle at test specimen upper surface, is returned to piezoelectric membrane by inclination surface crack deflection and is received by transducer itself。Fig. 1 is the inclination surface crack deflection echo propagation path that transducer receives with arrow black heavy line。When transducer moves Δ z along X-direction, sound wave propagation distance in water is constant, the inclination surface crack deflection echo time variable quantity that transducer receives is Δ t, and then can be propagated the distance variation delta S of inclination surface crackle by test specimen upper surface in the hope of sound wave。In Δ OAB, Δ S and Δ z is it is known that be then easy to try to achieve the angle of θ, and the tilt angle theta of inclination surface crackle_fEqual with θ, then inclination surface crack inclination angle degree:

${\mathrm{\θ}}_f={\sin }^{-1}\left(\frac{V_S\×\mathrm{\Δ}t}{2\×\mathrm{\Δ}z}\right)---\left(0\right)$

Wherein: V_SFor the longitudinal wave velocity of detected test specimen, Δ z is the displacement of X-direction line focus ultrasonic transducer, and Δ t is the inclination surface crack deflection echo time variable quantity after moving horizontally Δ z。

Sound wave propagation distance from test specimen upper surface to inclination surface crackle:

$L_{OC}=\frac{V_S\×(t_f-t_D)}{2}---\left(0\right)$

The angle of inclination of known inclination surface crackle, in Δ OCD, according to the cosine law, inclination surface crack depth immediately below ultrasonic transducer center:

$h=\frac{V_S\×(t_f-t_D)}{2{\mathrm{cos\θ}}_f}---\left(0\right)$

Wherein: t_fFor the inclination surface crack deflection echo time that transducer receives, t_DFor the test specimen upper surface direct reflection echo time that transducer receives。

Step 2): test system building

In order to facilitate X-direction stepping measurement, build a set of test system carrying out horizontal stepping measurement, as shown in Figure 2。This test system specifically includes that sample (1), tank (2), transducer (3), X-axis mobile platform (4), pulse excitation/receiving instrument (5), oscillograph (6), gpib bus (7), PXI general control system (8), shift servo motor (9)。Wherein, at X-axis mobile platform (4) transducer installed below (3), transducer (3) is connected with pulse excitation/receiving instrument (5), pulse excitation/receiving instrument (5) is connected with oscillograph (6), oscillograph (6) is connected with PXI general control system (8) by gpib bus (7), and PXI general control system (8) is connected with shift servo motor (9)。

Step 3): start position data collection

Being placed in below line focus ultrasonic transducer by the Steel material test specimen containing inclination surface crack defect, in test specimen, inclination surface crack inclination angle degree is 10 °, and transducer is positioned at the left side of test specimen。Pulse excitation/receiving instrument (5) is converted to reception state after sending the pulse that bandwidth is 10-50MHz, after receiving reflected signal, is transmitted by signal into oscillograph (6), and oscillographic sample frequency is f_s, f_sFor 5GHz, sampling number is N_s=10000。After oscillographic low-pass filtering, being stored in PXI general control system (8) by gpib bus (7), original position time domain waveform is as shown in Figure 3。

Step 4): X-direction stepping measurement

By a transducer mobile distance, delta z in the horizontal direction₀=1mm, to be moved complete after carry out voltage data collection, gather, after terminating, transducer moved in the horizontal direction Δ z again₀=1mm carries out data acquisition, sample frequency f_s=5GHz, sampling number N_s=10000, so move in circles, move 20mm altogether, therefore will obtain 21 groups of voltage datas。

Step 5): inclination surface crackle echo time matching

Find out the position of transducer when upper surface echo is about to separate with inclination surface crackle echo, draw the reflection echo time domain waveform stacking chart behind this position, in Fig. 4 shown in solid black lines, black dotted lines is inclination surface crackle echo fitting a straight line, because being horizontally oriented movement, so upper surface echo time point is identical。Therefrom selecting the reflection echo signal that continuous six groups of inclination surface crackle echo amplitudes are bigger, table 1 is the time of test specimen upper surface and inclination surface crack deflection echo in these six groups of signals。

The direct reflection echo of table 1 test specimen upper surface and inclination surface crack deflection echo time

Step 6): inclination surface crack inclination angle degree calculates

Move horizontally the inclination surface crack deflection echo time variation delta t after Δ z=1mm:

Δ t=t_f(i+1)-t_f(i)(1) wherein i is transducer moving displacement, takes 4 to 8 successively。

Bring the inclination surface crack deflection echo time variation delta t of acquirement into formula (1) and the angle of inclination of inclination surface crackle can be obtained。Wherein firm longitudinal wave velocity V_S=5900m/s, calculates and obtains 5 inclination surface crack inclination angle degree θ_f, respectively 9.95 °, 9.85 °, 9.78 °, 9.47 °, 10.3 °, then do average, can obtain inclination surface crack inclination angle degree more accurately is θ_f=9.88 °, testing inspection result matches with actual。

Step 7): inclination surface crack depth calculates

When transducer is positioned at diverse location, upper surface and inclination surface crack deflection echo time bring formula (2) into, can try to achieve under diverse location the degree of depth h of inclination surface crackle immediately below transducer center, as shown in table 2:

Inclination surface crack depth immediately below table 2 transducer center

The invention have the advantages that 1) inclination surface crack inclination angle degree is accurate with depth survey in test specimen；2) test specimen structure is not carried out any destruction。

Claims (1)

1. the detection method of an inclination surface crack inclination angle degree and the degree of depth, it is characterised in that: the implementing procedure of the method is as follows,

Step 1): establish the formula calculating inclination surface crack inclination angle degree and the degree of depth

In the detection signal of inclination surface crack inclination angle degree and the degree of depth, the propagation path of inclination surface crack deflection echo is that inclination surface crackle the beam path returned by original route are arrived in vertical transmission, can calculate the tilt angle theta of inclination surface crackle according to equation below_f:

${\mathrm{\θ}}_f={\sin }^{-1}\left(\frac{V_S\×\mathrm{\Δ}t}{2\×\mathrm{\Δ}z}\right)---\left(1\right)$

Wherein: V_SFor the longitudinal wave velocity of detected test specimen, Δ z is the displacement of X-direction line focus ultrasonic transducer, and Δ t is the inclination surface crack deflection echo time variable quantity after transducer moves Δ z；

After trying to achieve the angle of inclination of inclination surface crackle, then inclination surface crack depth h immediately below ultrasonic transducer center:

$h=\frac{V_S\×(t_f-t_D)}{2{\mathrm{cos\θ}}_f}---\left(2\right)$

Wherein: t_fFor the inclination surface crack deflection echo time that transducer receives, t_DFor the test specimen upper surface direct reflection echo time that transducer receives；

Step 2): test system building

In order to facilitate X-direction stepping measurement, having built a set of test system carrying out horizontal stepping measurement, this test system specifically includes that sample (1), tank (2), transducer (3), X-axis mobile platform (4), pulse excitation/receiving instrument (5), oscillograph (6), gpib bus (7), PXI general control system (8), shift servo motor (9)；Wherein, it is mounted below transducer (3) at X-axis mobile platform (4), transducer (3) is connected with pulse excitation/receiving instrument (5), pulse excitation/receiving instrument (5) is connected with oscillograph (6), oscillograph (6) is connected with PXI general control system (8) by gpib bus (7), and PXI general control system (8) is connected with shift servo motor (9)；Being filled with water in described tank (2), sample (1) is placed on the bottom of tank (2)；

Step 3): start position data collection

Being placed in by test specimen containing inclination surface crackle below line focus ultrasonic transducer, transducer is positioned at the left side of test specimen；Pulse excitation/receiving instrument (5) is converted to reception state after sending the pulse that bandwidth is 10-50MHz, after receiving reflected signal, is transmitted by signal into oscillograph (6), and oscillographic sample frequency is f_s, f_sFor 0.5-5GHz, sampling number is N_s, N_sSpan be 10000-100000 point；After oscillographic low-pass filtering, it is stored in PXI general control system (8) by gpib bus (7)；

Step 4): X-direction stepping measurement

Transducer horizontal direction is moved a distance, delta z₀, Δ z₀Span be 0.5-1mm, to be moved complete laggard row data acquisition, sample frequency is f_s, sampling number is N_s；Transducer level is moved right after terminating Δ z by collection again₀Carrying out data acquisition, so move in circles, the span of displacement z, z is 15-100mm altogether, therefore will obtain M group voltage data, and M is by z and Δ z₀Together decide on, for 15-200 group；

Step 5): inclination surface crackle echo time matching

First echo that oscillograph receives is the direct reflection echo of test specimen upper surface, because inclination surface crackle is above test specimen bottom surface, so second echo is inclination surface crack deflection echo, and then determine the reflection echo time of upper surface and inclination surface crackle during diverse location；

Step 6): inclination surface crack inclination angle degree calculates

Longitudinal wave velocity V by transducer moving displacement Δ z in X direction, inclination surface crack deflection echo time variable quantity and test specimen_SBring formula (1) into, the angle of inclination of inclination surface crackle can be tried to achieve；

Step 7): inclination surface crack depth calculates

When transducer is positioned at a certain optional position above inclination surface crackle, the existing upper surface reflection echo of reflection echo signal has again inclination surface crack deflection echo, by upper surface and inclination surface crackle echo time t_DWith t_f, the longitudinal wave velocity V of test specimen_STilt angle theta with inclination surface crackle_fBring formula (2) into, the degree of depth of inclination surface crackle immediately below transducer center can be tried to achieve。