A T-type structural defect detection method based on ultrasonic TOFD technology

Abstract

The present invention discloses a method for detecting defects in T-shaped structures based on ultrasonic TOFD technology. The method comprises the following steps: selecting the positions of an ultrasonic transmitting probe and a receiving probe on the same side of the wing and web of the T-shaped structure based on the material, thickness, and refraction angle of the probe, so that the ultrasonic longitudinal wave field excited by the transmitting probe covers the effective detection range and the ultrasonic diffraction field at the end of the defect can be received by the receiving probe; adjusting the relative positions of the transmitting and receiving probes, performing an A-scan on the object being detected, and obtaining information on the buried position of the defect in the cross section of the T-shaped structure through geometric solution based on the defect signal propagation time, probe position, and probe time delay parameters obtained from the two A-scan data; and performing a D-scan on the object being detected to obtain a D-scan image and information on the length distribution of the defect along the T-shaped structure. The present invention simplifies the detection process and saves time.

Description

Technical Field

[0001] The present invention belongs to the field of ultrasonic nondestructive testing, and relates to a T-shaped structural defect nondestructive testing method, and specifically relates to a T-shaped structural defect detection method based on ultrasonic TOFD technology. Background Art

[0002] Ultrasonic time of flight diffraction (TOFD) is a non-destructive testing method that locates and quantitatively measures defects based on the diffraction signal received at the end of the defect. It is suitable for the detection of structural defects in thick welds. This method has also been studied and applied in T-joint detection. In academic paper 1 (Yang Yuwei et al., Positioning calculation and evaluation of defect depth during TOFD detection of T-joints, Nondestructive Testing, 2021, 43(3):40-45), the establishment of a simulated isosceles triangle to adapt to the instrument's built-in depth positioning calculation program when performing TOFD detection on the wing plate side of the T-joint was discussed, and a correction calculation method for the displayed depth and actual depth was introduced. In academic paper 2 (Qi Xiangqian, Ultrasonic TOFD detection method for T-type welded joints, Nondestructive Testing, 2014, 36(9):75-77), a corresponding ultrasonic TOFD detection process was developed for T-joints whose wing plates are not restricted by structural conditions. In academic paper 3 (Wang Yong, Application of Ultrasonic TOFD Testing Technology in T-Type Welds, Jiangsu Science and Technology Information, 2016, (6): 53-54), TOFD testing was used to inspect T-type welds, and a symmetrical and asymmetrical TOFD scanning method was proposed. The above technologies are all related research conducted when the wing plate of the T-type joint can be inspected. However, in actual engineering, when the non-exposed wing plate side of the T-type structure cannot be inspected, new detection methods and methods are needed. Summary of the Invention

[0003] In order to solve the technical problem of structural defect identification and positioning when conventional ultrasonic TOFD cannot detect the wing plate of T-joint, the present invention provides a T-joint structural defect detection method based on ultrasonic TOFD technology.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A T-shaped structural defect detection method based on ultrasonic TOFD technology includes the following steps:

[0006] Step 1: Establish a coordinate system on the T-shaped structure section. The horizontal axis of the coordinate system is the straight line on the upper surface of the wing plate, and the vertical axis of the coordinate system is the axis of symmetry of the T-shaped structure.

[0007] Step 2: Based on the material, thickness and refraction angle of the T-shaped structure to be inspected, select the positions of the ultrasonic transmitting probe and receiving probe on the same side of the wing and web of the T-shaped structure so that the ultrasonic longitudinal wave sound field excited by the transmitting probe covers the effective detection range and the ultrasonic diffraction sound field at the defect end can be received by the receiving probe;

[0008] Step 3: Adjust the relative position of the transmitting probe and the receiving probe, perform A-scan on the object to be tested, and obtain A-scan signal S1; record the relative position of the probe and the structure to be tested (A1, B1) and save the A-scan signal S1;

[0009] Step 4: Adjust the relative position of the transmitting probe and the receiving probe, perform an A-scan on the object to be tested again, and obtain an A-scan signal S2; record the new relative position of the probe and the structure to be tested (A2, B2) and save the A-scan signal S2;

[0010] Step 5: Read the defect signal propagation time t1 and t2 in the A-scan signals S1 and S2, and calculate the defect signal propagation time t1 and t2 according to the ultrasonic probe delay time 2t0, the T-shaped structure plate thickness H, the two probe positions (A1, B1), (A2, B2) and the T-shaped structure material longitudinal wave speed C p The following set of equations is established to solve the position coordinates (x, y) of the defect end in the T-shaped structure, thereby realizing the location of the defect in the T-shaped structure section:

[0011]

[0012]

[0013] Where A1 and A2 are the distances from the acoustic incident point of the wing probe to the web; B1 and B2 are the distances from the acoustic incident point of the web probe to the wing; H is the thickness of the wing and web; t1 is the propagation time of the first diffraction wave of the defect at probe placement position 1; t2 is the propagation time of the second diffraction wave of the defect at probe placement position 2; 2t0 is the probe delay; C P is the longitudinal wave velocity in the material being tested;

[0014] Step 6: Fix the relative position relationship between the two probes in the T-shaped structure, and perform D scanning along the length direction of the T-shaped structure. Arrange the acquired A signals in sequence to obtain a D scanning image of the T-shaped structure;

[0015] Step 7: Read the distribution information of the defect along the T-shaped structure in the D-scan image, that is, the position of the defect in the length direction of the T-shaped structure and its own length size.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The present invention does not require additional hardware auxiliary facilities and can identify internal defects in the T-shaped structure being inspected and can perform positioning measurement on them without signal and image processing;

[0018] 2. The present invention overcomes the problem of effectively detecting and locating internal defects when the T-shaped structure wing plate cannot be inspected;

[0019] 3. The present invention can effectively identify the ends of artificial defects in aluminum alloy T-shaped structures with a wing plate and a web plate thickness of 12 mm, and the positioning error does not exceed 0.5 mm;

[0020] 4. The detection process of the present invention is simple, time-saving, and widely used in the field of ultrasonic non-destructive testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of obtaining an ultrasonic TOFDA signal for the first time using the method of the present invention;

[0022] Figure 2 This is a schematic diagram of obtaining the ultrasonic A signal for the second time after adjusting the positions of probes 1 and 2 according to the method of the present invention;

[0023] Figure 3 Schematic diagram of the method of the present invention for determining the position of a defect point by solving the coordinates of the intersection of two ellipses;

[0024] Figure 4 A side view of an artificial defect specimen used for testing the method of the present invention;

[0025] Figure 5 A top view of an artificial defect specimen used for testing the method of the present invention;

[0026] Figure 6 A three-dimensional image of an artificial defect specimen used for testing the method of the present invention;

[0027] Figure 7 Schematic diagram of the cross section of an artificial defect;

[0028] Figure 8 It is a 3D scan image. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0030] The present invention provides a T-shaped structural defect detection method based on ultrasonic TOFD technology, the method comprising the following steps:

[0031] Step 1: On the T-shaped structure interface, establish a coordinate system. The horizontal axis of the coordinate system is the straight line on the upper surface of the wing plate, and the vertical axis of the coordinate system is the axisymmetric line of the T-shaped structure.

[0032] Step 2: Based on the material, thickness and refraction angle of the T-shaped structure to be inspected, select the positions of the ultrasonic transmitting probe and receiving probe on the same side of the wing and web of the T-shaped structure so that the ultrasonic longitudinal wave sound field excited by the transmitting probe covers the effective detection range and the ultrasonic diffraction sound field at the defect end can be received by the receiving probe;

[0033] Step 3: Adjust the relative position of the transmitting probe and the receiving probe, perform A-scan on the object to be tested, and obtain A-scan signal S1; record the relative position of the probe and the structure to be tested (A1, B1) and save the A-scan signal S1;

[0034] Step 3: Adjust the relative position of the transmitting probe and the receiving probe, perform an A-scan on the object to be tested again, and obtain an A-scan signal S2; record the new relative position of the probe and the structure to be tested (A2, B2) and save the A-scan signal S2;

[0035] Step 4: Read the defect signal propagation time t1 and t2 in the scanning signals S1 and S2, and calculate the defect signal propagation time t1 and t2 according to the ultrasonic probe delay time 2t0, the T-shaped structure plate thickness H, the two probe positions (A1, B1), (A2, B2) and the T-shaped structure material longitudinal wave speed C p The following set of equations is established to solve the position coordinates (x, y) of the defect end in the T-shaped structure, thereby quantitatively detecting the defect:

[0036]

[0037]

[0038] Where A1 and A2 are the distances from the acoustic incident point of the wing probe to the web; B1 and B2 are the distances from the acoustic incident point of the web probe to the wing; H is the thickness of the wing and web; t1 is the propagation time of the first diffraction wave of the defect at probe placement position 1; t2 is the propagation time of the second diffraction wave of the defect at probe placement position 2; 2t0 is the probe delay; C P is the longitudinal wave velocity in the material being tested.

[0039] By substituting known data into the simultaneous equations (1) and (2) to solve the binary equations about x and y, the specific values of x and y can be obtained, thereby realizing the location of the defect in the T-shaped structural section.

[0040] Step 5: Fix the relative position relationship of the two probes in the T-shaped structure, and perform D scanning along the length direction of the T-shaped structure. Arrange the acquired A signals in sequence to obtain a D scanning image of the T-shaped structure.

[0041] Step 6: Read the distribution information of the defect along the T-shaped structure in the D-scan image, that is, the position of the defect in the length direction of the T-shaped structure and its own length size.

[0042] The principle of the present invention is:

[0043] Based on the conventional ultrasonic TOFD method, the present invention changes the probe arrangement of the conventional ultrasonic TOFD method and adopts an arrangement in which the two probes are not in the same plane. In combination with the geometric characteristics of the T-shaped structure, ultrasonic probes are arranged on the same side of the wing plate and the web to obtain the detection signal of the internal defects of the T-shaped structure and locate the defects. Figure 1 As shown in the figure, when the two probes are respectively at the position of A1 from the web and B1 from the wing, the ultrasonic diffraction signal of the defect at point O is obtained, and the propagation time t1 of the defect signal is read in the instrument (including the probe delay time, the sum of the acoustic propagation time between point a1 and point O, and between point b1 and point O). The defect point may appear on a double ellipse with a1 and b1 as the foci and the distance from the two foci being the sum of a1O and b1O. Changing the probe position, when the two probes are respectively at the position of A2 from the web and B2 from the wing, the ultrasonic diffraction signal of the defect at point O is obtained, and the propagation time t2 of the defect signal is read in the instrument (including the probe delay time, the sum of the acoustic propagation time between point a2 and point O, and between point b2 and point O). The defect point may appear on a double ellipse with a2 and b2 as the foci and the distance from the two foci being the sum of a2O and b2O. By solving equations (1) and (2) simultaneously, the value of (x, y) can be solved, thereby obtaining the position of the defect in the coordinate system of the T-shaped structure section, and realizing the positioning detection and measurement of the defect.

[0044] The above technology can be used to obtain the positional information of a defect at a specific cross-section of a T-shaped structure. The defect's dimensional information along the length of the T-shaped structure can also be obtained using a D-scan method. After selecting the positions of the two probes, the two probes perform a synchronized scanning motion along the length of the T-shaped structure, acquiring A-scan signals and then scanning again at a specific scanning step length. This ultimately produces a D-scan image. The D-scan image can be used to determine the dimensional distribution of the defect along the length of the T-shaped structure.

[0045] Example

[0046] This embodiment uses artificial defects of an aluminum alloy T-shaped structure as the detection object. The thickness of the web and wing plates of the aluminum alloy T-shaped structure is 12.0 mm. The detection process is as follows: the longitudinal wave refraction angle of the transmitting probe 1 and the receiving probe 2 in the aluminum alloy is 60°, the center frequency is 5 MHz, and the diameter of the piezoelectric chip is 6 mm. Adjust the positions of the ultrasonic transmitting probe 1 and the receiving probe 2 so that A1 = 18 mm and B1 = 23 mm, and read the defect signal propagation time t1; adjust the positions of the transmitting probe 1 and the receiving probe 2 so that A2 = 25 mm and B2 = 21 mm, and read the defect signal propagation time t2. Combine the following set of equations to calculate the position information of the defect end:

[0047]

[0048]

[0049] In the formula, A1=18mm; B1=23mm; A2=25mm; B2=21mm; H=12mm; t1=12.3us; t2=12.7us; 2t0=8.9us; C P =6260m / s.

[0050] It is calculated that the actual horizontal distance of defect F6 in the coordinate system is x=1.69mm, and the vertical distance is y=15.69mm. The actual horizontal distance of the positioning detection value is x=1.40mm, and the vertical distance is y=15.98mm. The positioning error is less than 0.5mm.

[0051] When the probe position is A1=18mm and B1=23mm, a D scan is performed and a D scan image is obtained, such as Figure 8 The actual length of defect F6 along the T-shaped structure is 15.0 mm, and the average value of three measurements in the D-scan image is 15.2 mm.

[0052] The A-scan, B-scan and D-scan described in this embodiment can be implemented using an ultrasonic C-scan system produced by the Physical Acoustics Corporation (PAC) of the United States.

Claims

1. A T-shaped structural defect detection method based on ultrasonic TOFD technology, characterized in that The method comprises the following steps: Step 1: Establish a coordinate system on the T-shaped structure section. The horizontal axis of the coordinate system is the straight line on the upper surface of the wing plate, and the vertical axis of the coordinate system is the axis of symmetry of the T-shaped structure. Step 2: Based on the material, thickness and refraction angle of the T-shaped structure to be inspected, select the positions of the ultrasonic transmitting probe and receiving probe on the same side of the wing and web of the T-shaped structure so that the ultrasonic longitudinal wave sound field excited by the transmitting probe covers the effective detection range and the ultrasonic diffraction sound field at the defect end can be received by the receiving probe; Step 3: Adjust the relative position of the transmitting probe and the receiving probe, perform A-scan on the object to be tested, and obtain the A-scan signal S1; record the relative position of the probe and the structure to be tested ( A 1. B 1) and save the A scan signal S1; Step 4: Adjust the relative position of the transmitting probe and the receiving probe, perform A-scan on the object to be tested again, and obtain A-scan signal S2; record the new relative position of the probe and the structure to be tested ( A 2. B 2) and save the A scan signal S2; Step 5: Read the defect signal propagation time in the A-scan signals S1 and S2 t 1. t 2. According to the delay time of the ultrasound probe 2 t 0. T-type structure plate thickness H 、Two probe positions ( A 1. B 1), ( A 2. B 2) and the longitudinal wave speed C of T-shaped structural materials p Establish a set of equations to solve the position coordinates of the defect end in the T-shaped structure ( x , y ), thereby realizing the location of defects in the T-shaped structural section, the equation group is as follows: ； ； Where, A 1. A 2 is the distance from the wing probe to the web; B 1. B 1 is the distance from the web probe to the wing plate; H is the thickness of the flange and web; t 1 is the propagation time of the diffraction wave 1 of the defect at the probe arrangement position 1; t 2 is the probe arrangement position 2 defect diffraction wave 2 propagation time; 2 t 0 is the probe delay; C p is the longitudinal wave velocity in the material being tested: Step 6: Fix the relative position relationship between the two probes in the T-shaped structure, and perform D scanning along the length direction of the T-shaped structure. Arrange the acquired A signals in sequence to obtain a D scanning image of the T-shaped structure; Step 7: Read the distribution information of the defect along the T-shaped structure in the D-scan image, that is, the position of the defect in the length direction of the T-shaped structure and its own length size.

Images