Titanium alloy bar ultrasonic flaw detection method and system

Abstract

The invention relates to the technical field of ultrasonic flaw detection of titanium alloy bars, in particular to an ultrasonic flaw detection method and system for titanium alloy bars, and the method comprises the following steps: obtaining ultrasonic signals of all positions; obtaining a receiving duration sequence of each position; according to the difference between adjacent peak values in the ultrasonic signal of each position, the dispersion degree of all the peak values, the average level of the receiving duration sequence and the difference between the receiving duration sequence of each position and the receiving duration sequence of the adjacent position, the real defect of each position is obtained; according to the dispersion degree of the amplitude average level of all the modal components of each position, the total number of the modal components and the energy concentration degree and the bandwidth of the ultrasonic signal of each position in the frequency domain, obtaining a signal abnormal factor of each position; defect factors of all the positions are obtained, and then whether defects exist in all the positions or not is judged. By analyzing the signal characteristics of the real defects in the titanium alloy bar, the accuracy of ultrasonic flaw detection of the titanium alloy bar is improved.

Description

Technical Field

[0001] This application relates to the technical field of ultrasonic flaw detection for titanium alloy bars, and specifically relates to a method and system for ultrasonic flaw detection of titanium alloy bars. Background Art

[0002] Titanium alloy bars are widely used in aerospace, ocean engineering, petrochemical and other fields due to their low density, high specific strength, corrosion resistance and other advantages. Metallurgical defects such as segregation and inclusions are likely to occur in the smelting process of titanium alloys. During the pressure processing and heat treatment processes in the production of titanium alloy bars, due to the difference in mechanical properties between metallurgical defects and the matrix, internal cracks and hole defects are generated in the titanium alloy bars.

[0003] Ultrasonic flaw detection technology has the advantages of high detection sensitivity, non-destructive detection, fast speed, etc., and can effectively detect internal defects in titanium alloy bars. Titanium alloy products have a complex multi-phase and polycrystalline structure and grain orientation differences, resulting in differences in the structure and organization of different parts of titanium alloy products, and abnormal signals such as an increase in clutter level and attenuation of bottom wave intensity occur during ultrasonic detection. These abnormal signals may be misjudged as defect signals, which not only affects the stability of ultrasonic detection signals, but also leads to inaccurate flaw detection results of titanium alloy bars. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a method and system for ultrasonic flaw detection of titanium alloy bars, and the specific technical solutions adopted are as follows: In the first aspect, an embodiment of this application provides a method for ultrasonic flaw detection of titanium alloy bars, and the method includes the following steps: Obtain ultrasonic signals at each position of the titanium alloy bar; Obtain the reception duration sequence at each position according to the time interval between signal emission and reception in each ultrasonic signal at each position; obtain all peaks in each ultrasonic signal; obtain the anisotropy significance degree at each position according to the difference between adjacent peaks in each ultrasonic signal at each position and the dispersion degree of all peaks, and combine the average level of the reception duration sequence at each position, as well as the difference between the reception duration sequences at each position and adjacent positions, to obtain the true defectiveness at each position; Decompose each ultrasonic signal into multiple modal components; obtain the signal complexity at each position according to the dispersion degree of the average level of the amplitudes corresponding to all modal components of each ultrasonic signal at each position and the total number of modal components, and combine the dispersion degree of the energy corresponding to all high-frequency components of each ultrasonic signal at each position in the frequency domain, as well as the bandwidth difference between each high-frequency component and non-high-frequency components, to obtain the signal anomaly factor at each position; Obtain the defect factor of each position according to the true defectiveness and signal anomaly factor of each position; determine whether there is a defect at each position according to the defect factor of each position.

[0005] Preferably, the acquisition method of the reception duration sequence of each position is as follows: take the duration from transmission to reception of each signal in the ultrasonic signals corresponding to each position as the reception duration of each signal in the ultrasonic signals corresponding to each position; form a sequence by arranging the reception durations of all signals in the ultrasonic signals corresponding to each position in ascending order, and denote it as the reception duration sequence of each position.

[0006] Preferably, the calculation formula for the anisotropy significance of each position is: ; in the formula, is the anisotropy significance of the i-th position, is the cumulative result of the differences between each peak and the next peak in the peak sequence of the i-th position, is the approximate entropy of the peak sequence of the i-th position, and exp( ) is the exponential function with the natural constant e as the base.

[0007] Preferably, the peak sequence of the i-th position refers to the sequence formed by arranging all the peaks in the ultrasonic signal of the i-th position in chronological order.

[0008] Preferably, the calculation formula for the true defectiveness of each position is: ; in the formula, is the true defectiveness of the i-th position, is the average value of all data in the reception duration sequence of the i-th position, is the cumulative result of the DTW distances between the reception duration sequence of the i-th position and the reception duration sequences of its neighboring positions, is the anisotropy significance of the ultrasonic signal of the i-th position, and norm( ) is the normalization function; among them, the neighboring positions of each position refer to the two positions closest to each position in the spiral detection trajectory.

[0009] Preferably, the acquisition method of the signal complexity of each position is: calculate the variance of the amplitude means of all modal components corresponding to the ultrasonic signals at each position of the titanium alloy bar, and take the product of the total number of all modal components corresponding to the ultrasonic signal of the i-th position and the variance as the signal complexity of the i-th position.

[0010] Preferably, the calculation formula for the signal anomaly factor of each position is: ; in the formula, is the signal anomaly factor of the i-th position, exp( ) is the exponential function with the natural constant e as the base, is the variance of the energies corresponding to all high-frequency components of the ultrasonic signal at the i-th position, is the cumulative result of the differences between each high-frequency component corresponding to the ultrasonic signal at the i-th position and the 3dB bandwidths corresponding to all the remaining non-high-frequency components, is the signal complexity at the i-th position, is a preset constant.

[0011] Preferably, the defect factor at each position is the positive fusion result of the true defectiveness and the signal anomaly factor at each position.

[0012] Preferably, the specific process of determining whether there are defects at each position is as follows: when the defect factor at a single position of the titanium alloy bar is less than the preset threshold, it is determined that there are no defects inside the titanium alloy bar at this position; otherwise, it is determined that there are defects inside the titanium alloy bar at this position.

[0013] In a second aspect, an ultrasonic flaw detection system for titanium alloy bars provided by an embodiment of the present application includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of the ultrasonic flaw detection method for titanium alloy bars described in any one of the above are implemented.

[0014] The present application has at least the following beneficial effects: 1. By analyzing the discriminative features of ultrasonic signals caused by true defects and elastic modulus anisotropy inside titanium alloy bars, the present application constructs the true defectiveness at each position, which can effectively avoid the drawbacks that abnormal signals such as abnormal ultrasonic propagation speed, increased clutter level, and attenuation of background pattern intensity caused by elastic modulus anisotropy inside titanium alloy bars are misjudged as defect signals, and improves the accuracy of ultrasonic flaw detection of titanium alloy bars.

[0015] 2. Compared with the traditional ultrasonic detection technology for titanium alloy products, the present application does not need to construct a complex energy distribution cloud map, and can quickly analyze and obtain the abnormal conditions of ultrasonic signals caused by true defects inside titanium alloy bars only relying on the characteristics of ultrasonic signals. By constructing the defect factor at each position to characterize the defect degree inside the titanium alloy bar, the true defect conditions inside each position of the titanium alloy bar can be evaluated more accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 The flowchart of the steps of an ultrasonic flaw detection method for a titanium alloy bar provided in an embodiment of the present application; Figure 2 The flowchart for obtaining the defect factors at each position provided in an embodiment of the present application. Detailed implementation manners

[0018] In order to further elaborate on the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following, in combination with the accompanying drawings and preferred embodiments, details the specific implementation manners, structures, features, and effects of an ultrasonic flaw detection method and system for a titanium alloy bar proposed according to the present application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs.

[0020] The following specifically describes the specific solutions of an ultrasonic flaw detection method and system for a titanium alloy bar provided by the present application with reference to the accompanying drawings.

[0021] Please refer to Figure 1 , which shows the flowchart of the steps of an ultrasonic flaw detection method for a titanium alloy bar provided in an embodiment of the present application. The method includes the following steps: Step 1: Obtain the ultrasonic signals at each position of the titanium alloy bar.

[0022] In this embodiment, relevant data in the ultrasonic flaw detection process of the titanium alloy bar is collected by the pulse detection method. Specifically: The titanium alloy bar is set to rotate along the axis of the bar at a linear speed of 10 m / min and perform horizontal movement. The ultrasonic probe of the digital ultrasonic flaw detector is used to perform spiral detection on the titanium alloy bar. The function of the ultrasonic probe is to emit and receive ultrasonic signals. The ultrasonic probe emits a high-frequency pulse every t seconds, and the corresponding ultrasonic wavelength is 1.2 mm. Each time the ultrasonic probe emits a high-frequency pulse, it corresponds to a different position of the titanium alloy bar. After each high-frequency pulse is emitted, the ultrasonic probe is used to receive the ultrasonic signals returned from each position of the titanium alloy bar (all the echo signals of each position of the titanium alloy bar in the depth direction), and the ultrasonic signals at each position of the titanium alloy bar in the spiral detection trajectory are obtained. In this embodiment, t is taken as 0.5.

[0023] The ultrasonic signals at each obtained position are used as the input of the wavelet transform algorithm for denoising, aiming to prevent the serious interference of external environmental noise on subsequent analysis. The wavelet transform algorithm is a well-known technology, and the specific process will not be elaborated here.

[0024] So far, the ultrasonic signals at each position in the titanium alloy bar can be obtained.

[0025] Step 2: Obtain the received duration sequence at each position according to the time interval between the emission and reception of each signal in the ultrasonic signals at each position; obtain all the peaks in each ultrasonic signal; obtain the anisotropy significance at each position according to the difference between adjacent peaks and the dispersion degree of all peaks in the ultrasonic signals at each position, and combine the average level of the received duration sequence at each position and the difference between the received duration sequences at each position and adjacent positions to obtain the true defectiveness at each position.

[0026] During the ultrasonic flaw detection of titanium alloy bars, the propagation of ultrasonic signals in titanium alloy bars is affected by the anisotropy of the elastic modulus of the close-packed hexagonal crystal structure, resulting in different propagation rates of ultrasonic waves in grains with different orientations, and thus different ultrasonic clutter signals and background attenuation conditions; real defects such as cracks, pores and inclusions inside the titanium alloy bars will also cause abnormal ultrasonic signals.

[0027] Specifically, real defects inside the titanium alloy bar will cause the attenuation of ultrasonic energy, thereby slowing down the propagation speed of ultrasonic signals and increasing the propagation time; the anisotropy of the elastic modulus results in differences in the wave speed of ultrasonic signals with different propagation directions, that is, when the propagation direction of ultrasonic waves is aligned with the crystal structure axis direction of titanium alloy, the propagation speed of ultrasonic signals is faster, while when the propagation direction of ultrasonic waves is perpendicular to the crystal structure axis, the wave speed is lower; the crystal orientation changes gently at adjacent positions of the titanium alloy bar, and usually has a continuous crystal orientation.

[0028] Secondly, real defects inside the titanium alloy will significantly scatter and absorb ultrasonic energy, thereby generating sharp and steep main reflection waves, while the anisotropy of the elastic modulus will generate relatively stable low-amplitude clutter; since the absorption and scattering degree of ultrasonic energy by real defect areas inside the titanium alloy bar is stronger than that of the anisotropy of the elastic modulus, the attenuation rate of ultrasonic signals caused by real defects inside the titanium alloy bar is higher, and the attenuation trend of ultrasonic signals caused by the anisotropy of the elastic modulus is more stable and slow.

[0029] For each position in the spiral detection trajectory, the two positions with the shortest distances to it are respectively used as the neighborhood positions of that position. The time duration from transmission to reception of each signal in the ultrasonic signals corresponding to each position is used as the reception duration of each signal in the ultrasonic signals corresponding to each position (internal defects and grain structure in the titanium alloy bar will cause ultrasonic scattering and diffraction, so multiple signals will be returned). The reception durations of all signals in the ultrasonic signals corresponding to each position are arranged in ascending order to form a sequence, denoted as the reception duration sequence of each position.

[0030] Taking the ultrasonic signals corresponding to each position in the spiral detection trajectory of the titanium alloy bar as inputs, the Automatic Multiscale-based Peak Detection (AMPD) algorithm is used to obtain all the peaks in each ultrasonic signal. The sequence formed by arranging all the peaks in each ultrasonic signal in chronological order is denoted as the peak sequence of each position.

[0031] As a preferred implementation, the anisotropy significance of each position is obtained based on the differences between adjacent peaks and the dispersion degree of all peaks in the ultrasonic signals of each position.

[0032] In this embodiment, the anisotropy significance of the ultrasonic signal at the i-th position in the titanium alloy bar is denoted as , and its specific expression is: ; in the formula, is the anisotropy significance of the i-th position, is the cumulative result of the differences between each peak and the next peak in the peak sequence of the i-th position (it should be noted that there is no peak after the last peak, so the difference of the last peak is not calculated), is the approximate entropy of the peak sequence of the i-th position, and exp( ) is the exponential function with the natural constant e as the base.

[0033] Characterizes the sharpness of the reflected wave caused by internal real defects in the ultrasonic signal and the smoothness of the ultrasonic signal attenuation. The larger the value of

[0034] , the more likely the ultrasonic signal at the i-th position is a signal generated by elastic modulus anisotropy.

[0035] In this embodiment, the true defectiveness at the $i$-th position in the titanium alloy bar is denoted as , and its specific expression is: ; where is the true defectiveness at the $i$-th position, is the average value of all data in the reception duration sequence at the $i$-th position, is the cumulative result of the DTW distance between the reception duration sequence at the $i$-th position and the reception duration sequences at its neighboring positions, is the anisotropy significance of the ultrasonic signal at the $i$-th position, and norm( ) is a normalization function that makes range between [0, 1]. In this embodiment, the sigmoid function is used for normalization.

[0036] reflects the slowness of the wave velocity of the ultrasonic signal in the titanium alloy bar; reflects the orientation difference between the $i$-th position and its adjacent positions. The larger is, the more likely it is that there is a defect at the $i$-th position. When is larger, it indicates that the wave velocity of the ultrasonic signal at the $i$-th position is slower, the difference in ultrasonic wave velocity caused by the continuous crystal orientation of adjacent positions is larger, the difference in the peaks of the ultrasonic detection signals is more significant, and the stability of the peak value change of the ultrasonic wave is worse. Then, the abnormal condition of the ultrasonic signal at this position is more likely to be caused by the true defect inside the titanium alloy bar.

[0037] Thus, the true defectiveness at each position in the spiral detection trajectory of the titanium alloy bar can be obtained through the above method.

[0038] Step 3: Decompose each ultrasonic signal into multiple modal components; according to the dispersion degree of the average amplitude level of all modal components corresponding to the ultrasonic signal at each position and the total number of modal components, obtain the signal complexity at each position, and combine the dispersion degree of the energy corresponding to all high-frequency components of the ultrasonic signal at each position in the frequency domain and the bandwidth difference between each high-frequency component and non-high-frequency components to obtain the signal anomaly factor at each position.

[0039] During the ultrasonic flaw detection of the titanium alloy bar, the difference in acoustic impedance in the internal composition segregation area (such as hard α defects) of the titanium alloy bar will cause the transmission loss of acoustic energy, and the difference in acoustic impedance between the true defect inside the product and the matrix tissue is relatively large, which will cause strong reflection of ultrasonic waves at the defect, not only generating high-amplitude reflected echoes, but also the scattering and diffraction of ultrasonic waves at the internal defects of the titanium alloy creating more reflection paths, and further exacerbating the distribution complexity of the ultrasonic signal on different frequency components.

[0040] ​Specifically, the actual defects inside the titanium alloy will result in a relatively complex energy distribution of all frequency components in the ultrasonic echo signal. Moreover, there are a large number of high-frequency components in the ultrasonic signal generated by the actual defects. These high-frequency components exhibit higher energy concentration and wider frequency spectrum characteristics in the frequency domain. Additionally, the increase in the ultrasonic scattering and diffraction paths will further exacerbate the complexity of the signal distribution of the ultrasonic signal, that is, the more obvious the differences between the modal components after the decomposition of the ultrasonic signal of the titanium alloy bar, and the stronger the discreteness of the energy distribution in each modal component.

[0041] Based on the above analysis, the present application constructs a signal anomaly factor to characterize the degree of abnormality of the ultrasonic signal caused by the internal defects of the titanium alloy bar. Taking the ultrasonic signal corresponding to each position in the spiral detection trajectory of the titanium alloy bar as the input, the frequency-domain representation of the ultrasonic signal at each position and each modal component corresponding to the ultrasonic signal are obtained by using the FFT (Fast Fourier Transform) and the EMD (Empirical Mode Decomposition) algorithm respectively. The frequencies of all frequency components in the frequency-domain representation of the ultrasonic signal are sorted in descending order, and the first p frequency components are selected and denoted as the high-frequency components of the ultrasonic signal (in this embodiment, p is taken as 10). Calculate the 3dB bandwidth of all frequency components corresponding to the ultrasonic signal at each position in the frequency domain.

[0042] Taking the mean value of all amplitudes corresponding to each modal component obtained after the decomposition of the ultrasonic signal as the amplitude mean value of each modal component. The greater the difference in the amplitude mean values between the modal components, the stronger the discreteness of the energy distribution of the ultrasonic signal on all modal components.

[0043] Calculate the variance of the amplitude mean values of all modal components corresponding to the ultrasonic signal at the i-th position of the titanium alloy bar, and take the product of the total number of all modal components corresponding to the ultrasonic signal at the i-th position and the variance as the signal complexity at the i-th position. The signal complexity characterizes the degree of signal complexity caused by the actual defects inside the titanium alloy.

[0044] As a preferred implementation manner, according to the signal complexity at each position, and in combination with the discreteness of the energies corresponding to all high-frequency components in the frequency domain of the ultrasonic signal at each position, and the bandwidth difference between the high-frequency components and the non-high-frequency components, the signal anomaly factor at each position is obtained to characterize the abnormal condition of the ultrasonic signal caused by the actual defects inside the titanium alloy bar and the complexity of the signal distribution.

[0045] In this embodiment, the signal anomaly factor at the i-th position in the titanium alloy bar is denoted as , and its specific expression is: ; in the formula, is the signal anomaly factor at the i-th position, and exp( ) is the exponential function with the natural constant e as the base. is the variance of the energies corresponding to all high-frequency components of the ultrasonic signal at the i-th position. is the cumulative result of the differences between each high-frequency component corresponding to the ultrasonic signal at the i-th position and the 3dB bandwidths corresponding to all the other non-high-frequency components. is the signal complexity at the i-th position. is a preset constant used to prevent the denominator from being zero. In this embodiment, it is taken as 0.01. and respectively reflect the energy concentration of high-frequency components and the bandwidth condition caused by internal defects in the titanium alloy bar. When the internal real defect of the titanium alloy bar is more serious, the energy concentration of the high-frequency components of the ultrasonic signal is stronger, that is, the index is smaller, the spectral bandwidth of the high-frequency components is larger, that is, the index is larger. At the same time, the component complexity of the ultrasonic signal is higher, the total number of modal components is larger, and the energy distribution of the frequency components corresponding to each modal component is more uneven, that is, the index becomes larger.

[0046] Step Four: Obtain the defect factor at each position according to the real defectiveness and the signal anomaly factor at each position; judge whether there are defects at each position according to the defect factor at each position.

[0047] When the ultrasonic signals at each position in the titanium alloy bar are more likely to be caused by real defects rather than elastic modulus anisotropy, and the degree of ultrasonic signal anomaly is greater, it indicates that the real defects inside the titanium alloy bar are more obvious and have a more serious impact on the quality of the titanium alloy bar.

[0048] As a preferred embodiment, obtain the defect factor at each position according to the real defectiveness and the signal anomaly factor at each position, which is used to characterize the internal defect condition at each position of the titanium alloy bar. Among them, the acquisition process of the defect factor at each position is as Figure 2 shown.

[0049] In this embodiment, the normalized result of the product of the signal anomaly factor and the real defectiveness at the i-th position is used as the defect factor at the i-th position.

[0050] In another embodiment, the normalized result of the sum of the signal anomaly factor and the real defectiveness at the i-th position is used as the defect factor at the i-th position.

[0051] When the defect factor at the $i$-th position is larger, it indicates that the ultrasonic signal at this position is more likely to be caused by real defects inside the titanium alloy bar rather than elastic modulus anisotropy, and the abnormal condition of the ultrasonic signal caused by defects inside the titanium alloy bar is more obvious. Then, the real defect inside the titanium alloy bar at the $i$-th position is more serious.

[0052] Furthermore, when the defect factor at a single position of the titanium alloy bar is less than the preset threshold, it is determined that there are no defects inside the titanium alloy bar at this position; otherwise, it is determined that there are defects inside the titanium alloy bar at this position. In this embodiment, the preset threshold is taken as 0.6, and the implementer can set the value of the preset threshold according to the actual situation.

[0053] Judge the presence of defects at all positions of the titanium alloy bar. When the total number of positions with defects in the titanium alloy bar is greater than or equal to the preset proportion of the total number of all positions, it is determined that the quality of the titanium alloy bar is unqualified, and then an unqualified mark is sprayed on the surface of the titanium alloy bar through the marking unit; otherwise, it is determined that the quality of the titanium alloy bar is qualified. In this embodiment, the value of the preset proportion is taken as 1 / 3, and the implementer can set the value of the preset proportion according to the actual situation.

[0054] Thus, a method for ultrasonic flaw detection of titanium alloy bars can be realized.

[0055] Based on the same inventive concept as the above method, the embodiment of the present application also provides a system for ultrasonic flaw detection of titanium alloy bars, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it realizes the steps of any one of the above methods for ultrasonic flaw detection of titanium alloy bars.

[0056] It should be noted that: the above sequence of the embodiments of the present application is only for description and does not represent the superiority or inferiority of the embodiments. And the above describes specific embodiments of this specification. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0057] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between each embodiment can be referred to each other. The key point of each embodiment is to illustrate the differences from other embodiments.

[0058] The above are only the preferred embodiments of the present application and are not used to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principle of the present application shall be included in the protection scope of the present application.

Claims

1. An ultrasonic flaw detection method for titanium alloy bars, characterized in that, The method includes the following steps: Obtain ultrasonic signals at various positions of the titanium alloy bar; Obtain the reception duration sequence at each position according to the time intervals between signal transmission and reception in the ultrasonic signals at each position; obtain all the peaks in each ultrasonic signal; obtain the anisotropy significance at each position according to the differences between adjacent peaks and the dispersion degree of all the peaks in the ultrasonic signals at each position, and combine the average level of the reception duration sequence at each position and the differences between the reception duration sequences at each position and adjacent positions to obtain the true defectiveness at each position; Decompose each ultrasonic signal into multiple modal components; obtain the signal complexity at each position according to the dispersion degree of the average levels of the amplitudes of all the modal components corresponding to the ultrasonic signals at each position and the total number of modal components, and combine the dispersion degree of the energies corresponding to all the high-frequency components in the frequency domain of the ultrasonic signals at each position and the bandwidth difference between the high-frequency components and non-high-frequency components to obtain the signal anomaly factor at each position; Obtain the defect factor at each position according to the true defectiveness and the signal anomaly factor at each position; judge whether there are defects at each position according to the defect factor at each position.

2. The ultrasonic flaw detection method for a titanium alloy bar as described in claim 1, wherein The method for obtaining the reception duration sequence at each position is as follows: take the duration from signal transmission to reception of each signal in the ultrasonic signal corresponding to each position as the reception duration of each signal in the ultrasonic signal corresponding to each position; form a sequence by arranging the reception durations of all the signals in the ultrasonic signal corresponding to each position in ascending order, and denote it as the reception duration sequence at each position.

3. The ultrasonic flaw detection method for a titanium alloy bar as described in claim 1, characterized in that, The calculation formula for the anisotropy significance at each position is as follows: ; where is the anisotropy significance at the i-th position, is the cumulative result of the differences between each peak and the next peak in the peak sequence at the i-th position, is the approximate entropy of the peak sequence at the i-th position, and exp( ) is the exponential function with the natural constant e as the base.

4. The ultrasonic flaw detection method for a titanium alloy bar as described in claim 3, characterized in that, The peak sequence at the i-th position refers to the sequence formed by arranging all the peaks in the ultrasonic signal at the i-th position in chronological order.

5. The ultrasonic flaw detection method for a titanium alloy bar as claimed in claim 1, characterized in that The calculation formula for the true defectiveness of each position is as follows: ; In the formula, is the true defectiveness of the i-th position, is the average value of all data in the reception duration sequence of the i-th position, is the cumulative result of the DTW distance between the reception duration sequence of the i-th position and the reception duration sequences of its neighboring positions, is the anisotropy significance of the ultrasonic signal at the i-th position, and norm( ) is the normalization function; where the neighboring positions of each position refer to the two positions closest to each position in the spiral detection trajectory.

6. The ultrasonic flaw detection method for a titanium alloy bar as described in claim 1, characterized in that, The method for obtaining the signal complexity at each position is as follows: calculate the variance of the amplitude means of all the modal components corresponding to the ultrasonic signals at various positions of the titanium alloy bar, and take the product of the total number of all the modal components corresponding to the ultrasonic signal at the i-th position and the variance as the signal complexity at the i-th position.

7. The ultrasonic flaw detection method for a titanium alloy bar as described in claim 1, characterized in that, The calculation formula for the signal anomaly factor at each position is as follows: ; where is the signal anomaly factor at the i-th position, exp( ) is the exponential function with the natural constant e as the base, is the variance of the energies corresponding to all high-frequency components of the ultrasonic signal at the i-th position, is the cumulative result of the differences between the 3dB bandwidths corresponding to each high-frequency component of the ultrasonic signal at the i-th position and the remaining all non-high-frequency components, is the signal complexity at the i-th position, is a preset constant.

8. A method for ultrasonic flaw detection of a titanium alloy bar according to claim 1, characterized in that, The defect factor at each position is the positive fusion result of the true defectiveness and the signal anomaly factor at each position.

9. A method for ultrasonic flaw detection of a titanium alloy bar according to claim 1, characterized in that, The specific process of judging whether there are defects at each position is as follows: when the defect factor at a single position of the titanium alloy bar is less than the preset threshold, it is judged that there is no defect inside the titanium alloy bar at this position; otherwise, it is judged that there is a defect inside the titanium alloy bar at this position.

10. An ultrasonic flaw detection system for titanium alloy bars, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the ultrasonic flaw detection method for a titanium alloy bar according to any one of claims 1-9.

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