Composite material layering defect detection method and equipment based on ultrasonic hysteresis response

Abstract

The invention relates to a composite material layering defect detection method and equipment based on ultrasonic hysteresis response, and the method comprises the following steps: adopting a phased array ultrasonic probe to transmit multichannel ultrasonic waves to a to-be-detected fiber reinforced composite material test piece, and receiving returned ultrasonic response signals of each ultrasonic channel; and based on the ultrasonic response signal and the excitation voltage, calculating to obtain a hysteresis nonlinear characteristic parameter of each ultrasonic channel for representing the nonlinear mechanical state of the interface, comparing the hysteresis nonlinear characteristic parameter with a preset threshold value, if the hysteresis nonlinear characteristic parameter is greater than the preset threshold value, judging that the composite material has a layering defect, and otherwise, judging that the composite material has a layering defect. Otherwise, judging that the composite material does not have the layering defect; and if the layering defect exists, determining the position of the layering defect based on the hysteresis nonlinear characteristic parameter and the corresponding ultrasonic channel position, and evaluating the size and severity of the layering defect according to the magnitude of a parameter peak value. Compared with the prior art, the method has the advantages that accurate positioning and quantitative evaluation of the layering defects in the variable-fiber-angle composite material are realized.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing technology for composite materials, and in particular to a method and equipment for detecting delamination defects in composite materials based on ultrasonic hysteresis response. Background Technology

[0002] Fiber-reinforced composites, especially those with variable fiber angles and customizable layup orientations, are widely used in load-bearing structures such as aircraft wings and wind turbine blades due to their ability to achieve both excellent mechanical properties and lightweight design. However, these materials are highly susceptible to internal damage such as delamination and fiber breakage under complex loads during manufacturing and service. Delamination is one of the most common and dangerous failure modes, significantly reducing the compressive strength and stability of the structure and seriously threatening the overall structural safety.

[0003] Currently, non-destructive testing and identification techniques for delamination defects in composite materials remain a key research focus in both industry and academia. Among these techniques, ultrasonic testing, especially pulse-echo C-scan technology, is considered a standard method due to its large detection depth and intuitive imaging. Traditional linear ultrasonic testing techniques mainly rely on changes in parameters such as the velocity, attenuation, and reflection coefficient of ultrasonic waves to identify defects. However, when applied to composite materials with variable fiber angles, these traditional methods face fundamental challenges: 1. Anisotropic interference: The propagation speed and attenuation of ultrasound in composite materials are strongly dependent on the fiber orientation. In composite materials with variable fiber angles, the changing layup angles cause complex distortions in the sound field, making it difficult to distinguish between reflected signals from delamination defects and reflected signals from normal material interfaces. This significantly reduces the signal-to-noise ratio, leading to missed or misjudged defects.

[0004] 2. Insensitive to closed delamination and micro-damage: Especially micron-level "kissing" delaminations that occur under compressive loads or during manufacturing, where the interfaces remain in contact even under static conditions. Traditional linear ultrasound responds weakly to such defects because sound waves can still partially pass through, resulting in insignificant changes in acoustic parameters and insufficient detection sensitivity.

[0005] 3. Reliance on benchmark comparison: Many linear ultrasonic methods require comparison with a defect-free "benchmark" specimen to effectively identify anomalies. However, in actual engineering structures, obtaining a completely consistent benchmark is often impractical.

[0006] To overcome the limitations of linear ultrasound, nonlinear ultrasonic testing technology has emerged and shown great potential. This technology mainly utilizes the characteristic that material or interface damage (such as microcracks and delamination) significantly enhances its mechanical nonlinearity, identifying damage by monitoring the nonlinear phenomena generated by the interaction between ultrasound waves and defects. The nonlinear parameters are extremely sensitive to microscopic changes in the structure, and theoretically, can detect early damage that traditional linear methods cannot identify.

[0007] However, most existing nonlinear ultrasonic methods focus on classical nonlinear elastic phenomena, and their models typically do not adequately consider the friction and slip mechanisms at the contact interface. For defects such as delamination, which have typical contact interface characteristics, they exhibit strong hysteresis behavior under cyclic loading. This hysteresis nonlinearity leads to an asymmetric stress-strain response in the ultrasonic waves during loading and unloading, and its nonlinear attenuation effect is much stronger than and distinct from that of classical nonlinear elasticity. Currently, there is a lack of published literature on specialized techniques and systematic research that can accurately capture and utilize this ultrasonic hysteresis response to identify delamination defects in composite materials, especially complex variable fiber angle composite materials.

[0008] Chinese patent application CN121324502A discloses an ultrasonic testing method for composite material structures. The method for detecting defects involves: arranging a first phased array and a second phased array on both sides of the test area of ​​a standard component; acquiring the second peak time after the arrival of the signal in the second phased array for each signal originating from the i-th element of the first phased array and reaching the j-th element of the second phased array; calculating the ratio of the amplitudes of the defect-free signal and the potential defect signal; forming a first defect image based on the echo data from the ultrasonic propagation path; swapping the first and second phased arrays and repeating the process to obtain a second defect image; and superimposing the first and second defect images to generate an overall image that can indicate the location of delamination defects in the test area of ​​the component with relatively bright regions. However, this method has low sensitivity to small or closed delaminations, weak resistance to fiber anisotropic interference, high risk of imaging distortion under complex layups, and in scenarios with multiple defects, noise and defect signals are easily confused. Furthermore, the detection process is complex, requires numerous ultrasonic probes, and is costly.

[0009] Therefore, inventing a layered identification method that can strip away the influence of material anisotropy, is highly sensitive to the interface contact state, and is based on the principle of ultrasonic hysteresis response has important theoretical value and engineering significance for improving the safety and reliability of variable fiber angle composite material structures. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art, such as the large distortion and interference of ultrasonic signals caused by the strong anisotropy of materials, which makes it difficult to effectively extract the echo of delamination defects; insufficient sensitivity for detecting small, closed delamination defects; and the fact that the detection results are easily affected by changes in fiber layup angle, and the need to improve the versatility and reliability. Therefore, this invention provides a method and device for detecting delamination defects in composite materials based on ultrasonic hysteresis response.

[0011] The objective of this invention can be achieved through the following technical solutions: A method for detecting delamination defects in composite materials based on ultrasonic hysteresis response, the method comprising: A phased array ultrasonic probe is used to emit multi-channel ultrasonic waves from the fiber-reinforced composite material specimen under test and to receive the ultrasonic response signals of each ultrasonic channel returned. During the emission of the ultrasonic waves, a cyclically varying excitation voltage is applied to the phased array ultrasonic probe. Based on the ultrasonic response signal and excitation voltage, the hysteresis nonlinear characteristic parameters of each ultrasonic channel used to characterize the nonlinear mechanical state of the interface are calculated and compared with a preset threshold. If the hysteresis nonlinear characteristic parameters are greater than the preset threshold, it is determined that the composite material has delamination defects; otherwise, it is determined that the composite material does not have delamination defects. If a layering defect exists, the location of the layering defect is determined based on the hysteresis nonlinear characteristic parameter that is greater than a preset threshold and its corresponding ultrasound channel location, and the size and severity of the layering defect are evaluated by the peak value of the hysteresis nonlinear characteristic parameter.

[0012] Furthermore, during the emission of ultrasonic waves, the excitation voltage undergoes a loading-unloading process, gradually increasing from a preset starting voltage value to a preset peak voltage value and then gradually decreasing back to the preset starting voltage value.

[0013] Furthermore, during the loading-unloading process, the initial voltage value is 125 V, the peak voltage value is 200 V, and the step value for gradually increasing from the initial voltage value to the peak voltage value is 25 V.

[0014] Furthermore, the calculation process of the hysteresis nonlinear characteristic parameter includes: The signal interval of the first arrival wave of the ultrasonic response signal is taken as the study time region; The integral of the square of the ultrasonic response signal amplitude over the study time region is calculated to obtain the nonlinear parameter value. Based on the rising and falling phases of the excitation voltage cyclic change, the nonlinear parameter values ​​corresponding to the same time are divided into rising phase nonlinear parameter values ​​and falling phase nonlinear parameter values. Calculate the difference between the nonlinear parameter values ​​in the rising phase and the nonlinear parameter values ​​in the falling phase corresponding to the excitation voltage values ​​that exist simultaneously in the rising and falling phases. The sum of these differences is the hysteresis nonlinear characteristic parameter.

[0015] Furthermore, for composite materials with non-uniform thickness, the study time range is also adjusted based on the slope of the two-dimensional ultrasound imaging image, which is a two-dimensional image formed by arranging the ultrasound response signals of all ultrasound channels according to the spatial position of the corresponding channels.

[0016] Furthermore, the phased array ultrasonic probe operates at a frequency of 2.25 MHz.

[0017] Furthermore, the location of the layered defect is the spatial location of the ultrasonic channel corresponding to the calculated peak value of the hysteresis nonlinear characteristic parameter.

[0018] Furthermore, if the hysteresis nonlinear characteristic parameter is less than the threshold but does not approach 0, it is determined to be microscale local peeling caused by the edge of the pore defect, and the composite material has the probability of having pore defects.

[0019] Furthermore, the higher the peak value of the hysteresis nonlinear characteristic parameter, the greater the size and severity of the delamination defects in the composite material.

[0020] An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the composite material delamination defect detection method based on ultrasonic hysteresis response as described above.

[0021] Compared with the prior art, the beneficial effects of the present invention include: 1. This invention effectively detects various delamination defects in composite materials with variable fiber angles through special processing of ultrasonic response signals. During ultrasonic testing, a cyclically varying excitation voltage is applied to the phased array ultrasonic probe, which excites a significant hysteresis nonlinear response in the composite material. Subsequently, hysteresis nonlinear characteristic parameters, used to characterize the nonlinear mechanical state of the interface, are extracted to determine delamination defects. These hysteresis nonlinear characteristic parameters are highly sensitive to minute changes in the interface contact state, accurately capturing weak defect signals. Furthermore, the physical essence of the hysteresis characteristic parameters is the interface mechanical behavior, rather than the ultrasonic wave propagation path or sound velocity. Therefore, they are unaffected by changes in fiber angle, acoustic field distortion caused by fiber wrinkles, or interference from pore defects, significantly improving the signal-to-noise ratio, effectively removing background interference, accurately capturing defect signals, and avoiding missed detections and misjudgments.

[0022] 2. This invention can not only determine the presence or absence of delamination defects, but also achieve precise location and quantitative assessment of defects through spatial distribution analysis of hysteresis characteristic parameters, making it particularly suitable for complex variable fiber angle composite material structures.

[0023] 3. The excitation voltage of this invention undergoes a loading-unloading process, gradually increasing from a preset starting voltage value to a preset peak voltage value and then gradually decreasing back to the preset starting voltage value. By actively controlling the cyclic loading path of the excitation voltage, the hysteresis effect at the measurement interface can be artificially enhanced, making the detection process more controllable and the detection results more stable and reliable.

[0024] 4. The core of the method of this invention can be combined with existing phased array ultrasonic testing equipment. It can be realized by upgrading the software algorithm, which makes it easy to promote and apply to non-destructive testing and in-service monitoring in industrial sites. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method of the present invention; Figure 2 The images shown are B-scan and A-scan images obtained in two directions when using a 2.25 MHz phased array probe for ultrasonic transmission scanning in an embodiment of the present invention. Figure 3 This is a comparison chart of the hysteresis responses of channels 1-64 for excitation and channels 65-128 for reception under six different voltage loading variations in this embodiment of the invention. Figure 4 The images shown are B-scan and A-scan images obtained during ultrasonic transmission scanning of a laminate containing both porosity defects and delamination defects in an embodiment of the present invention. Figure 5 This is a hysteresis response diagram of each channel in two directions of the first group of a laminate containing both porosity defects and delamination defects in an embodiment of the present invention, arranged in chronological order. Figure 6 This is a hysteresis response diagram of each channel in two directions of the second group in the second group according to time sequence for a laminate containing both porosity defects and delamination defects in an embodiment of the present invention. Figure 7 This is a hysteresis response diagram of each channel in two directions in the third group according to time sequence for a laminate containing both porosity defects and delamination defects in an embodiment of the present invention. Figure 8 This is a comparison diagram of the energy of each channel at the first arrival wave in an embodiment of the present invention for a straight fiber laminate containing delamination defects and a curved fiber laminate containing delamination defects. Figure 9 This is a diagram showing the hysteresis response of each channel in two directions of the first group of the curved fiber laminate in the embodiment of the present invention, arranged in chronological order. Figure 10 This is a diagram showing the hysteresis response of each channel in two directions of the second group of the curved fiber laminate in an embodiment of the present invention, arranged in chronological order. Figure 11 This is a diagram showing the hysteresis response of each channel in two directions of the third group of the curved fiber laminate in the embodiment of the present invention, arranged in chronological order. Figure 12 This is a photograph of a sample containing various complex defects in an embodiment of the present invention; Figure 13 These are B-scan and A-scan images obtained in two directions during ultrasonic transmission scanning of a sample containing multiple complex defects in an embodiment of the present invention. Figure 14 The hysteresis response diagrams of each channel in two directions of the first group of samples containing multiple complex defects in the embodiments of the present invention are shown in the time sequence. Figure 15 The hysteresis response diagrams of each channel in two directions of the second group of the sample containing multiple complex defects in the embodiments of the present invention are arranged in time sequence. Figure 16 This is a hysteresis response diagram of each channel in two directions of the third group of samples containing multiple complex defects in an embodiment of the present invention, arranged in chronological order. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0027] Example 1 This embodiment discloses a method for detecting delamination defects in composite materials based on ultrasonic hysteresis response. The method is as follows: Figure 1 As shown, steps S1-S4 are included, and each step is described as follows: Step S1: A phased array ultrasonic probe is used to emit multi-channel ultrasonic waves to the fiber-reinforced composite material specimen under test, and the ultrasonic response signals of each ultrasonic channel returned are received.

[0028] The phased array ultrasonic probe operates at a frequency of 2.25 MHz, achieving an optimal balance between detection sensitivity and penetration depth.

[0029] During the transmission of ultrasonic waves, a cyclically varying excitation voltage is applied to the phased array ultrasonic probe.

[0030] The excitation voltage undergoes a loading-unloading process, gradually increasing from a preset starting voltage value to a preset peak voltage value, and then gradually decreasing back to the preset starting voltage value.

[0031] Specifically, the initial voltage value, peak voltage value, and step value for gradually increasing from the initial voltage value to the peak voltage value during the loading-unloading process were obtained through experiments.

[0032] Step S2: Based on the ultrasonic response signal and excitation voltage, calculate and obtain the hysteresis nonlinear characteristic parameters of each ultrasonic channel used to characterize the nonlinear mechanical state of the interface.

[0033] The calculation process of the hysteresis nonlinear characteristic parameters includes: The signal interval of the first arrival wave of the ultrasonic response signal is taken as the research time region; The integral of the square of the ultrasonic response signal amplitude over the study time region is calculated to obtain the nonlinear parameter values. Based on the rising and falling phases of the excitation voltage cyclic change, the nonlinear parameter values ​​corresponding to the same time are divided into rising phase nonlinear parameter values ​​and falling phase nonlinear parameter values. Calculate the difference between the nonlinear parameter values ​​in the rising and falling phases corresponding to the excitation voltage values ​​that exist simultaneously in the rising and falling phases. The sum of these differences is the hysteresis nonlinear characteristic parameter.

[0034] For composite materials with non-uniform thickness, the study time range is also adjusted based on the slope of the two-dimensional ultrasonic imaging map, which is a two-dimensional image formed by arranging the ultrasonic response signals of all ultrasonic channels according to the spatial position of the corresponding channels.

[0035] Specifically, nonlinear parameter values The calculation expression is: in,[ , [This refers to the time region under study.] Let be the amplitude of the ultrasonic response signal at time t.

[0036] Taking a starting excitation voltage of 125 V, a peak value of 200 V, and a voltage rise / fall step of 25 V as an example, except for 200 V, the other voltages all have two nonlinear parameter values: a rising phase and a falling phase. During the voltage drop phase E The value is represented as During the voltage rise phase E The value is represented as The formula for calculating the hysteresis nonlinear characteristic parameter is: Where n is the number of voltage points where both rising and falling voltage phases exist simultaneously.

[0037] Step S3: Compare the calculated hysteresis nonlinear characteristic parameters of each ultrasonic channel with a preset threshold. If the hysteresis nonlinear characteristic parameter is greater than the preset threshold, it is determined that the composite material has delamination defects; otherwise, it is determined that the composite material does not have delamination defects.

[0038] If the hysteresis nonlinear characteristic parameter is less than the threshold but does not approach 0, it is determined to be microscale local peeling caused by the edge of the pore defect, and the composite material has the probability of having pore defects.

[0039] Step S4: If a layering defect exists, the location of the layering defect is determined based on the hysteresis nonlinear characteristic parameter greater than a preset threshold and its corresponding ultrasound channel position, and the size and severity of the layering defect are evaluated by the peak value of the hysteresis nonlinear characteristic parameter.

[0040] The location of the layered defect is the spatial location of the ultrasonic channel corresponding to the peak value of the calculated hysteresis nonlinear characteristic parameter.

[0041] The higher the peak value of the hysteresis nonlinear characteristic parameter, the larger and more severe the delamination defects in the composite material.

[0042] Example 2 This embodiment, based on the ultrasonic hysteresis response-based composite material delamination defect detection method disclosed in Embodiment 1 above, conducts optimization experiments on detection parameters to determine the excitation voltage loop path that can most effectively excite the ultrasonic hysteresis response while also considering detection efficiency. The specific optimization process is as follows: To investigate the influence of different voltage ranges on the intensity of hysteresis nonlinear response and to balance detection effect and efficiency, multiple sets of cyclic loading scan experiments with different voltage ranges were designed and executed.

[0043] The applied excitation voltages all adopt a triangular wave cyclic pattern of "rising from the initial voltage to the peak voltage and then falling back to the initial voltage". Since hysteresis is more pronounced in the high-voltage region, the maximum voltage is set to 200V. The five specific voltage paths set in this embodiment are as follows: Group 1: 50 V → 200 V → 50 V Group 2: 75 V → 200 V → 75 V Group 3: 100 V → 200 V → 100 V Group 4: 125 V → 200 V → 125 V Group 5: 150 V → 200 V → 150 V Group 6: 175 V → 200 V → 175 V Analysis of the ultrasonic signals collected in each group of experiments revealed that excessively large voltage variations (such as in groups 1 and 2) resulted in excessively long single-detection cycles, poor efficiency, and unsatisfactory practical applications; while excessively small voltage variations (such as in groups 5 and 6) were insufficient to fully stimulate the hysteresis effect that could be accurately measured. Figure 3 The time integration region of interest is 5μs to 6μs. Figure 2 The first arrival wave signal range in the A-scan image changes with the sample thickness. The A-scan image is a one-dimensional signal acquired by a single ultrasonic channel, reflecting the response of ultrasonic waves to the interaction between the ultrasonic waves and the internal structure of the material at a fixed spatial position of the probe. The B-scan image is a two-dimensional image formed by arranging multiple A-scan signals according to their spatial positions (positions of the phased array ultrasonic probe), reflecting the ultrasonic response at different positions and depths.

[0044] about Figure 3 The actual implementation method of the data in the document is explained below. In any channel, by Figure 2 In the A-scan plot, the amplitude can be defined as A, which is a function that varies with time. The nonlinear parameter examined in this invention is the integral of the ultrasonic transmission energy near the first arriving wave, and this parameter is defined as: In the formula, This indicates the initial time point of the region under study. This indicates the end time point of the region under study. Because at any given voltage stage, there is a different... E Except for 200V, all other voltage values ​​have two phases: a rising phase and a falling phase. E For clarity, the voltage rise phase of 50V will be shown below. E The value is represented as During the 50V voltage drop phase E The value is represented as The same applies to the other voltages. The average channel asymmetry ratio is then defined. As Figure 2 The ordinate visually reflects the strength of nonlinearity, and has In the formula, n represents the number of voltage points where both rising and falling voltage phases exist simultaneously, as shown in Group 1. n= 6.

[0045] Then the 64 channels of the phased array will be positioned Connecting the points to form a line allows for comparison of the degree of nonlinearity in the detected area.

[0046] After comprehensive comparison, the cyclic path (group 4) with a starting and ending voltage of 125 V and a peak voltage of 200 V was determined to achieve the optimal detection time efficiency while ensuring sufficient strength of the hysteresis response signal, and this result can be repeated multiple times. By comparing the hysteresis phenomenon with other defect-free locations, it can be concluded that this hysteresis phenomenon is caused by delamination defects in the laminate. Therefore, this voltage path is preferred as the standard hysteresis excitation condition in all subsequent systematic tests of variable fiber angle composite materials. In subsequent experiments, to fully avoid various possible errors, it is considered that... A value above 0.005 indicates a more obvious layering defect.

[0047] Example 3 Based on Examples 1 and 2 above, this embodiment designs the following comparative experiment to verify the specificity of the method in Example 1 for identifying layered defects and its anti-interference ability in complex defect environments: A straight fiber composite laminate was selected as the experimental specimen. Two different types of defects—porosity defects and delamination defects—were introduced at different spatial locations on the specimen, while the remaining part of the specimen served as a defect-free baseline area. The location and morphology of all defects were pre-calibrated and confirmed using conventional ultrasonic C-scan.

[0048] Experimental and analytical methods: Using the optimized detection parameters from Example 2 (2.25MHz phased array probe, 125V→200V→125V voltage cycle path), a full-area scan of the above-mentioned specimen was performed. During the data processing stage, through... Figure 4 It can be found that pore defects are located near channel 13, while delamination defects are located near channel 45. This fact provides strong evidence for the accuracy of subsequent hysteresis analysis.

[0049] To obtain rigorous experimental results, three sets of comparative experiments were conducted at the same location with very short time intervals. The results are as follows: Figures 5 to 7 As shown, the hysteresis parameter values ​​measured at the defect-free and porosity defect (near channel 13) are in the same low-level range, with no significant difference between the two. However, the hysteresis parameter value at the delamination defect (near channel 45) shows a sharp and significant increase compared to the previous two regions, with an increase of several orders of magnitude.

[0050] Experimental conclusion: The comparison results strongly confirm the theoretical prediction: at the porosity defects The values ​​in all three experimental groups were significantly lower than the aforementioned cutoff value of 0.005, indicating the presence of delamination defects. The values ​​in all three groups are significantly higher than 0.005. Porosity, as a volumetric defect within the material, does not significantly alter the contact mechanics between interfaces and therefore does not induce observable ultrasonic hysteresis. Delamination, as a typical interfacial damage, directly alters the contact stiffness and frictional behavior of the interface, leading to a strong nonlinear hysteresis effect under cyclic loading.

[0051] This embodiment conclusively demonstrates that the ultrasonic hysteresis nonlinear characteristic parameters defined in this invention can clearly distinguish between interfacial damage (delamination) and bulk defects (pores). This method exhibits high specificity for delamination defects and can effectively eliminate interference from bulk defects such as pores, providing a reliable technical means for the accurate identification and classification of internal defects in composite materials.

[0052] Example 4 This embodiment, based on Embodiments 1 and 2 above, provides an example of detecting delamination defects in variable fiber angle composite laminates. The specimen used in this embodiment is a specially designed variable fiber angle composite laminate containing a curved fiber region (i.e., a fiber wrinkle region). The fiber orientation in this region varies with curves rather than being a constant straight line. This complex fiber structure introduces strong material anisotropy, causing distortion and scattering of the ultrasonic wave propagation path, thus severely interfering with the accuracy of traditional linear ultrasonic testing methods in identifying delamination defects.

[0053] Experimental methods: An artificial delamination defect of known size and location was implanted within the curved fiber region. Subsequently, the region was scanned using optimized detection parameters (2.25MHz phased array probe, 125V→200V→125V voltage cycle path), which were identical to those used in the aforementioned straight fiber experiment.

[0054] like Figure 8 As shown, in traditional methods, the location of defects is usually roughly determined by analyzing the loss of projected energy during propagation. This method is also very accurate in straight fiber laminates (it can determine that the delamination defect is near channel 32). However, in curved fiber laminates, the presence of fiber folds will also cause sound wave scattering and energy dissipation, making it impossible to accurately determine the location of the delamination defect. Therefore, the traditional method is no longer applicable.

[0055] However, in the method provided by this invention, the measured ultrasonic hysteresis nonlinear characteristic parameter values ​​remain stable at a low level in the defect-free region of the curved fiber area. ).

[0056] In the areas where delamination defects are located, despite complex fiber orientation and acoustic interference, the hysteresis parameter values ​​still exhibit significant peak values ​​different from those in the defect-free areas. This experiment consisted of three groups, as shown below. Figure 9 , Figure 10 , Figure 11 As shown. In the three sets of experiments, at the same delamination defect location. The values ​​are all higher than 0.005, thus proving that the present invention is also highly sensitive to delamination defects in curved fibers.

[0057] In areas without delamination defects, The result, being well below 0.005, indicates that the material anisotropy and acoustic scattering effects caused by fiber wrinkles have minimal impact on the ultrasonic hysteresis nonlinear characteristic parameters upon which this method relies. The fundamental reason is that this method probes the nonlinear mechanical response of the interface under cyclic loading, rather than relying on the straight-line propagation path of ultrasound or a constant sound velocity. Delamination defects, as interfacial damage, directly and decisively modulate this nonlinear response.

[0058] Example 5 This embodiment is based on Embodiments 1 and 2 above. In this embodiment, a sample with multiple complex defects will be tested, such as... Figure 12 As shown, the sample is a composite material with variable fiber angle and thickness, exhibiting porosity defects, delamination defects, and fiber wrinkling defects simultaneously. The coexistence of multiple defects poses a significant challenge to traditional ultrasonic testing methods. Traditional B-scan diagrams are insufficient to effectively identify delamination defects, such as… Figure 13 .

[0059] In this embodiment, the optimized detection parameters (2.25MHz phased array probe, 125V→200V→125V voltage cycle path) that are completely consistent with those in the aforementioned straight fiber experiment are used to scan the area.

[0060] It should be noted that: 1. Because the sample is a variable thickness sample, therefore for and The choice is no longer fixed, but rather combines the slope in the B-scan graph with the change of the channel position.

[0061] 2. Because the sample length is less than the phased array probe length, the area after channel 60 is actually air. Therefore, for Figures 14 to 16 The data in the middle needs to ignore the data after channel 60.

[0062] The experimental results in this embodiment show that the sample contains a delamination defect in the central region (between channels 31 and 34). The value is significantly higher than other points, and The value is the same as that produced by the known layering defects in the foregoing embodiments. The values ​​are at similar levels, indicating the presence of stratification here. However, at the positions between channels 9 and 12... The value is neither close to 0 in the defect-free region nor as large as the amplitude in the delamination defect region. Combined with the analysis of the sample preparation process, this abnormal signal can be attributed to microscale local peeling caused by the edge of the pore defect.

[0063] This result simultaneously proves the following three points: The invention defines The value parameter exhibits extremely high specificity and sensitivity to layered defects. Experimental results show that... The magnitude of the value is directly related only to the size and severity of the delamination defect, and is basically unaffected by complex factors such as porosity defects and fiber orientation changes.

[0064] In situations where traditional ultrasound B-scan cannot effectively identify layering due to the coexistence of multiple defects, this invention successfully extracts clear features of layering defects from complex background noise by extracting nonlinear hysteresis response, demonstrating its strong anti-interference and defect identification capabilities under complex actual working conditions.

[0065] This method can not only identify macroscopic stratification, but also detect weak stratification caused by stress concentration points such as pore edges, which provides a possible technical means for monitoring the early damage evolution and predicting the life of composite material structures.

[0066] In summary, this invention provides a method for identifying delamination defects in composite materials based on ultrasonic hysteresis response. Its core lies in applying a cyclic voltage load using a phased array probe to actively excite the interface and extract hysteresis nonlinear characteristic parameters specific to delamination defects. This method overcomes the limitations of traditional linear ultrasound, exhibiting extremely high sensitivity and specificity for delamination defects. It can also effectively overcome the interference of complex factors such as anisotropy and porosity in variable fiber angle composite materials, providing an innovative solution for the accurate and reliable detection of internal defects in complex components.

[0067] Example 6 Based on Embodiment 1, this embodiment provides an electronic device, including: one or more processors and a memory, wherein the memory stores one or more programs, the one or more programs including instructions for executing the aforementioned composite material delamination defect detection method based on ultrasonic hysteresis response.

[0068] At the hardware level, the electronic device includes a processor, internal bus, network interface, memory, and non-volatile memory, and may also include other hardware required for business operations. The processor reads the corresponding computer program from the non-volatile memory into memory and then runs it to implement the aforementioned method for detecting delamination defects in composite materials based on ultrasonic hysteresis response. Of course, in addition to software implementation, this invention does not exclude other implementation methods, such as logic devices or a combination of hardware and software, etc. That is to say, the execution entity of the following processing flow is not limited to individual logic units, but can also be hardware or logic devices.

[0069] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0070] Computer-readable media include both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for detecting delamination defects in composite materials based on ultrasonic hysteresis response, characterized in that, The method includes: A phased array ultrasonic probe is used to emit multi-channel ultrasonic waves from the fiber-reinforced composite material specimen under test and to receive the ultrasonic response signals of each ultrasonic channel returned. During the emission of the ultrasonic waves, a cyclically varying excitation voltage is applied to the phased array ultrasonic probe. Based on the ultrasonic response signal and excitation voltage, the hysteresis nonlinear characteristic parameters of each ultrasonic channel used to characterize the nonlinear mechanical state of the interface are calculated and compared with a preset threshold. If the hysteresis nonlinear characteristic parameters are greater than the preset threshold, it is determined that the composite material has delamination defects; otherwise, it is determined that the composite material does not have delamination defects. If a layering defect exists, the location of the layering defect is determined based on the hysteresis nonlinear characteristic parameter that is greater than a preset threshold and its corresponding ultrasound channel location, and the size and severity of the layering defect are evaluated by the peak value of the hysteresis nonlinear characteristic parameter.

2. The method for detecting delamination defects in composite materials based on ultrasonic hysteresis response according to claim 1, characterized in that, During the emission of ultrasonic waves, the excitation voltage undergoes a loading-unloading process, gradually increasing from a preset starting voltage value to a preset peak voltage value and then gradually decreasing back to the preset starting voltage value.

3. The method for detecting delamination defects in composite materials based on ultrasonic hysteresis response according to claim 2, characterized in that, During the loading-unloading process, the initial voltage value is 125 V, the peak voltage value is 200 V, and the step value for gradually increasing the voltage value from the initial voltage value to the peak voltage value is 25 V.

4. The method for detecting delamination defects in composite materials based on ultrasonic hysteresis response according to claim 1, characterized in that, The calculation process of the hysteresis nonlinear characteristic parameters includes: The signal interval of the first arrival wave of the ultrasonic response signal is taken as the study time region; The integral of the square of the ultrasonic response signal amplitude over the study time region is calculated to obtain the nonlinear parameter value. Based on the rising and falling phases of the excitation voltage cyclic change, the nonlinear parameter values ​​corresponding to the same time are divided into rising phase nonlinear parameter values ​​and falling phase nonlinear parameter values. Calculate the difference between the nonlinear parameter values ​​in the rising phase and the nonlinear parameter values ​​in the falling phase corresponding to the excitation voltage values ​​that exist simultaneously in the rising and falling phases. The sum of these differences is the hysteresis nonlinear characteristic parameter.

5. The method for detecting delamination defects in composite materials based on ultrasonic hysteresis response according to claim 4, characterized in that, For composite materials with non-uniform thickness, the study time range is further adjusted based on the slope of the two-dimensional ultrasound imaging image, which is a two-dimensional image formed by arranging the ultrasound response signals of all ultrasound channels according to the spatial position of the corresponding channels.

6. The method for detecting delamination defects in composite materials based on ultrasonic hysteresis response according to claim 1, characterized in that, The phased array ultrasonic probe operates at a frequency of 2.25 MHz.

7. The method for detecting delamination defects in composite materials based on ultrasonic hysteresis response according to claim 1, characterized in that, The location of the layered defect is the spatial location of the ultrasonic channel corresponding to the calculated peak value of the hysteresis nonlinear characteristic parameter.

8. The method for detecting delamination defects in composite materials based on ultrasonic hysteresis response according to claim 1, characterized in that, If the hysteresis nonlinear characteristic parameter is less than the threshold but does not approach 0, it is determined to be microscale local peeling caused by the edge of the pore defect, and the composite material has the probability of having pore defects.

9. The method for detecting delamination defects in composite materials based on ultrasonic hysteresis response according to claim 1, characterized in that, The higher the peak value of the hysteresis nonlinear characteristic parameter, the greater the size and severity of the delamination defect in the composite material.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the composite material delamination defect detection method based on ultrasonic hysteresis response as described in any one of claims 1-9.

Images