A replaceable tofd technology selection method

Abstract

The application discloses a replaceable TOFD technology selection method, and belongs to the technical field of nondestructive testing. In view of the problem that it is difficult to select a replaceable TOFD technology for blind area suppression in actual detection, a quantified standard of applicability is established, and the replaceable TOFD technology with the strongest applicability under given parameters is determined. The replaceable TOFD technology selection method can quickly determine the replaceable TOFD technology with the strongest applicability under given detection conditions, so as to suppress the blind area of TOFD detection and realize near-surface defect detection. Meanwhile, the method can be built into an ultrasonic detection device and applied to TOFD detection of various materials, and has high engineering application value and popularization prospect.

Description

TECHNICAL FIELD

[0001] The application relates to a replaceable TOFD technology selection method and belongs to the technical field of nondestructive testing. BACKGROUND

[0002] Time of Flight Diffraction (TOFD) is a nondestructive testing method for quantitatively detecting defects by using defect end point diffraction longitudinal wave time difference. The method has the advantages of high quantitative precision and high area defect detection rate and is widely used in the detection of welded structures in the fields of petrochemical industry, nuclear power and the like. However, when TOFD is used to detect near-surface defects, the defect end point diffraction wave is easily lost in the direct wave due to the width of the ultrasonic pulse, forming a near-surface detection blind area and leading to difficulty in defect depth quantification.

[0003] To solve the above problems, researchers have proposed replaceable TOFD technologies such as mode conversion wave (JIN S J, et al. Quantitative detection of shallow subsurface cracks in pipeline with time-of-flight diffraction technique [J]. NDT&E International, 2021, 118: 102397), twice-reflected longitudinal wave (CHI D Z, et al. Shallow buried defect testing method based on ultrasonic TOFD [J]. Journal of Nondestructive Evaluation, 2013, 32(2): 164-171), LS-L wave (F.W.T.Yeh, et al. An alternative ultrasonic time-of-flight diffraction (TOFD) method [J]. NDT&E International, 2018, 100: 74-83) and the like. The principle is to use other forms of defect end point diffraction / scattering wave to replace the direct diffraction wave used in conventional TOFD, so as to avoid aliasing with the direct wave by increasing the propagation path. However, the various replaceable TOFD waveforms have similar characteristics and applicable ranges, and it is difficult to select a method in actual detection, and there is a lack of quantitative applicability standards. The application proposes a replaceable TOFD technology selection method to select the most applicable replaceable TOFD technology in actual engineering detection. SUMMARY

[0004] The application provides a replaceable TOFD technology selection method. The purpose is to solve the problem that it is difficult to select a replaceable TOFD technology for blind area suppression in actual detection, establish a suitability quantization standard, and clearly determine the most suitable replaceable TOFD technology under given parameters. The minimum propagation time difference of the replaceable TOFD wave and the structural wave is used as the judgment standard for the strength of suitability, and is defined as the quantized applicability. The replaceable TOFD wave corresponding to the highest quantized applicability is selected as the most suitable method under the given parameters.

[0005] The technical scheme adopted by the application is:

[0006] A replaceable TOFD technology selection method based on a TOFD detection system composed of an ultrasonic flaw detector, a TOFD probe, an inclined organic glass wedge block and a scanning device. Under the premise of given probe center separation (PCS), workpiece thickness and defect depth range, the quantized applicability of mode conversion wave (L-S), half-cross mode conversion wave (LL-S), LS-L wave and secondary reflected longitudinal wave (LL-LL) is calculated, and a three-dimensional graph of the quantized applicability of different methods is given as the basis for selecting replaceable TOFD technology, so as to be applied to TOFD detection blind area suppression and near-surface defect quantification. The method adopts the following steps:

[0007] (a) Detection parameter range determination

[0008] For any given plate workpiece thickness h and defect depth d, select a pair of TOFD probes with a center frequency of f, and match the inclined organic glass wedge block. The probe center separation is set to 2S in detection; wherein h, d and S are any positive numbers greater than 0, and satisfy h>d;

[0009] (b) Structural wave propagation time calculation

[0010] Let the longitudinal wave speed of the plate workpiece material to be measured be c L , and the transverse wave speed be c S ; under the detection parameter conditions determined in step (a), the propagation times t LW , t L and t S of the straight-through wave, the bottom reflected longitudinal wave and the bottom reflected transverse wave are calculated by using formulas (1) to (3) respectively:

[0011]

[0012]

[0013]

[0014] Where y is the eccentricity of the bottom shear wave reflection point and satisfies Fermat’s theorem, that is,

[0015]

[0016] (c) Can replace TOFD wave propagation time calculation

[0017] The horizontal distance between the midpoint of the line connecting two symmetrically arranged TOFD probes and the end point of the defect is defined as the eccentricity x. When the midpoint of the probe line is on the left side of the defect, x>0. Under the detection parameter conditions determined in step (a), the propagation time t of LS wave, LL-S wave, LS-L wave and LL-LL wave is calculated by equations (5) to (8) respectively: L-S , t LL-S , t LS-L and t LL-LL :

[0018]

[0019]

[0020]

[0021]

[0022] Where z is the distance from the bottom surface reflection shear wave point to the defect endpoint, and it satisfies Fermat's theorem, that is,

[0023]

[0024] (d) Quantitative applicability calculation of alternative TOFD technologies

[0025] Under the detection parameter conditions determined in step (a), the quantitative applicability of the LS wave, LL-S wave, LS-L wave, and LL-LL wave is calculated using equations (10) to (13) respectively;

[0026] A L-S =min(|t L-S -t LW |,|t L-S -t L |,|t L-S -t S |) (10)

[0027] A LL-S =min(|t LL-S -t LW |,|t LL-S -t L |,|t LL-S -t S |) (11)

[0028] A LS-L =min(|t LS-L -t LW |,|t LS-L -t L |,|t LS-L -t S |) (12)

[0029] A LL-LL =min(|t LL-LL -t LW |,|t LL-LL -t L |,|t LL-LL -t S |) (13)

[0030] (e) Comparison of quantitative applicability of alternative TOFD techniques

[0031] The quantitative applicability of the alternative TOFD technologies obtained in step (d) is compared using formula (14) to obtain the alternative TOFD wave with the highest quantitative applicability under any given parameter combination, thereby determining the corresponding alternative TOFD technology; wherein the given parameters include h, d, and S;

[0032]

[0033] (f) Generation of 3D images of quantitative applicability of alternative TOFD technology

[0034] Perform numerical processing based on the highest quantitative applicability obtained in step (e). If but If satisfied Then A=0; if but If satisfied but On this basis, the hdS three-dimensional coordinate system is established, and the A values ​​under different h, d and S parameter combinations are assigned to the coordinate system nodes with different colors, generating a three-dimensional diagram of the quantitative applicability of alternative TOFD technology;

[0035] (g) Application of 3D images to quantify the applicability of alternative TOFD technology

[0036] In actual detection, first determine the known h and S, as well as the range of the defect depth d; based on this, search for the node color under the corresponding parameter combination in the quantitative applicability three-dimensional diagram to determine the most suitable alternative TOFD technology; read the corresponding alternative TOFD wave arrival time, and use Equation (5), Equation (6), Equation (7), or Equation (8) to invert the defect depth d.

[0037] The beneficial effects of the present application are: the replaceable TOFD technology selection method introduces quantitative applicability to quantitatively evaluate the applicability of various replaceable TOFD technologies, which does not depend on the actual detection conditions, and can directly and quickly determine the most applicable replaceable TOFD technology, thereby inhibiting the TOFD detection blind area and near-surface defect detection. At the same time, the method can be built into an ultrasonic detection device and applied to TOFD detection of various materials, and has high engineering application value and promotion prospects. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a schematic diagram of the TOFD detection system used in the present application.

[0039] Figure 2 is a three-dimensional diagram of the quantitative applicability of the replaceable TOFD technology generated by the present application.

[0040] Figure 3 is a TOFD-B scan image detected using given parameters.

[0041] Figure 4 is an A-scan signal at an eccentricity x = 13.0 mm. DETAILED DESCRIPTION

[0042] The specific embodiments of the present application are further described below in combination with the drawings and technical solutions.

[0043] A replaceable TOFD technology selection method uses a TOFD detection system as shown in Figure 1 , which includes a pair of TOFD probes and an inclined organic glass wedge, and an ultrasonic detector connected to a scanning device. The specific processing steps are as follows:

[0044] (a) Taking aluminum alloy material as an example, the longitudinal wave speed c L = 6300 m / s, and the transverse wave speed c S = 3100 m / s. In combination with the actual detection needs, the half-probe center distance S, the workpiece thickness h, and the defect depth d range and the calculation interval are determined to be 10 mm≤S≤40 mm, interval 1.0 mm; 5 mm≤h≤20 mm, interval 0.5 mm; 1 mm≤d≤4 mm, interval 1.0 mm. Therefore, a h-d-S three-dimensional coordinate system is established, and there are a total of 31×31×31 nodes in the space.

[0045] (b) According to the parameters in step (a), the structure wave propagation time and the replaceable TOFD wave propagation time under the given detection parameter range are calculated. Within the above experimental parameter range, a total of 31×31×31 groups of structure wave propagation time and replaceable TOFD wave propagation time are obtained.

[0046] (c) According to the quantification applicability formula of various alternative TOFD waves, the quantification applicability is calculated, and comparison is made under the same parameter condition, to obtain the quantification applicability A of each node in the three-dimensional coordinate system. By color assignment, a three-dimensional graph of quantification applicability of alternative TOFD technology is generated, as shown in Figure 2 . Among them, black is the most applicable area of LS-L wave, gray is the most applicable area of LL-S wave, and white is the most applicable area of L-S wave, that is, the applicability of each alternative TOFD technology can be intuitively represented within the set parameter range. It should be pointed out that there is no most applicable area of LL-LL wave in this detection parameter range.

[0047] (d) The TOFD probe with a nominal frequency f = 10 MHz is used for detection to verify the effectiveness of the method. An aluminum alloy plate with a thickness h = 20 mm is selected, and a bottom surface groove with an endpoint depth d = 3 mm is processed. The PCS is set during detection, that is, 2S = 40 mm. Other detection parameters include: longitudinal wave wedge angle 60°, detection gain 80 dB, scanning step 0.5 mm, and A-scan time window starting position set to before the direct wave reaches the receiving probe. According to the above determined detection parameters, combined with Figure 2 , the most applicable alternative TOFD wave is L-S wave.

[0048] (e) To further verify the reliability of the results, the TOFD probe is used for B-scan of the defect of the aluminum alloy test block. Figure 3 The corresponding B-scan image is given, and it is obvious that the defect endpoint diffraction wave is mixed with the direct wave, and the defect endpoint diffraction / scattering waves used by other alternative TOFD technologies are also mixed with the bottom surface reflection wave to different degrees. Only L-S wave can be clearly read. The A-scan signal at x = 13.0 mm is extracted from the original image, as shown in Figure 4 . The read L-S wave propagation time t L-S = 11.43 μs, and the inverse calculation by formula (5) gives the measured depth of the defect as 3.01 mm, with a relative quantitative error of 0.3%. Obviously, the optimal alternative TOFD technology obtained by Figure 2 is the only one that can be applied to actual detection, and the quantitative accuracy meets the engineering requirements.

[0049] The description presented in the above exemplary embodiments is only used to illustrate the technical solutions of the present application and is not intended to be exhaustive or to limit the present application to the precise forms described. Obviously, many changes and variations are possible for those skilled in the art based on the above teachings. The exemplary embodiments are selected and described in order to explain the specific principles of the present application and its practical application, so that other skilled persons in the art can easily understand, implement and utilize various exemplary embodiments of the present application and various selected forms and modifications thereof. The scope of protection of the present application is intended to be defined by the appended claims and their equivalents.

Claims

1. A method for selecting an alternative TOFD technology, characterized in that: The TOFD inspection system, which consists of an ultrasonic flaw detector, a TOFD probe, a tilted plexiglass wedge, and a scanning device, uses the following steps: (a) Determination of detection parameter range For any given flat workpiece thickness h and defect depth d to be inspected, a pair of TOFD probes with a center frequency of f is selected and matched with tilted organic glass wedges. The probe center distance during inspection is set to 2S. Where h, d, and S are all positive numbers greater than 0, and h>d is satisfied. (b) Calculation of structural wave propagation time Assume that the longitudinal wave speed of the flat workpiece material to be measured is c L , the shear wave speed is c S Under the detection parameter conditions determined in step (a), use equations (1) to (3) to calculate the propagation time t of the direct wave, the bottom surface reflected longitudinal wave, and the bottom surface reflected shear wave respectively. LW , t L and t S : (1) ； (2) ； (3) ； Where y is the eccentricity of the bottom shear wave reflection point and satisfies Fermat’s theorem, that is, (4) ； (c) Can replace TOFD wave propagation time calculation The horizontal distance between the midpoint of the line connecting two symmetrically arranged TOFD probes and the end point of the defect is defined as the eccentricity x. When the midpoint of the probe line is on the left side of the defect, x>0. Under the detection parameter conditions determined in step (a), the propagation time t of LS wave, LL-S wave, LS-L wave and LL-LL wave are calculated by equations (5) to (8) respectively: L-S , t LL-S , t LS-L and t LL-LL : (5) ； (6) ； (7) ； (8) ； Where z is the distance from the bottom surface reflection shear wave point to the defect endpoint, and it satisfies Fermat's theorem, that is, (9) ； (d) Quantitative applicability calculation of alternative TOFD technologies Under the detection parameter conditions determined in step (a), the quantitative applicability of the LS wave, LL-S wave, LS-L wave, and LL-LL wave is calculated using equations (10) to (13) respectively; (10) ； (11) ； (12) ； (13) ； Where A L-S 、A LL-S 、A LS-L and A LL-LL They represent the quantization applicability of LS wave, LL-S wave, LS-L wave and LL-LL wave respectively; (e) Comparison of quantitative applicability of alternative TOFD techniques The quantitative applicability of the alternative TOFD technologies obtained in step (d) is compared using formula (14) to obtain the alternative TOFD wave with the highest quantitative applicability under any given parameter combination, thereby determining the corresponding alternative TOFD technology; wherein the given parameters include h, d, and S; (14) ； Where, Indicates A L-S 、A LL-S 、A LS-L and A LL-LL The maximum value among , i.e. the highest quantitative applicability; (f) Generating 3D images of the quantitative applicability of alternative TOFD techniques Perform numerical processing based on the highest quantitative applicability obtained in step (e). If , then the quantitative applicability A for a given h, d and S parameter combination is defined as If satisfied ,but If satisfied ,but If satisfied ,but On this basis, the hdS three-dimensional coordinate system is established, and the A values ​​under different h, d and S parameter combinations are assigned to the coordinate system nodes with different colors, generating a three-dimensional diagram of the quantitative applicability of alternative TOFD technologies. (g) Application of 3D images to quantify the applicability of alternative TOFD technology In actual detection, first determine the known h and S, as well as the range of the defect depth d; based on this, search for the node color under the corresponding parameter combination in the quantitative applicability three-dimensional diagram to determine the most suitable alternative TOFD technology; read the corresponding alternative TOFD wave arrival time, and use Equation (5), Equation (6), Equation (7), or Equation (8) to invert the defect depth d.

Images