CN108918666B - Passive knocking type material damage detection device and method - Google Patents
Passive knocking type material damage detection device and method Download PDFInfo
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Abstract
The invention provides a passive knock-on material damage detection device and method, wherein the material damage detection device comprises: the detection device comprises at least one wheel body, wherein the peripheral surface of the wheel body is provided with hard knocking teeth, and the knocking teeth are configured to knock the structural surface of a material to be detected along with the rotation of the wheel body; a sensor configured to sense a response signal transmitted to the sensor by a tapped area of the structure surface; a processor configured to determine an area where structural damage exists from the signals sensed by the sensor. According to the material damage detection device provided by the invention, the knocking teeth are arranged on the wheel body, so that the whole structure of the test device can be simplified, and meanwhile, the structure surface of the material to be detected can be stably knocked, and therefore, the damage position in the material to be detected can be accurately determined according to the detected signal.
Description
Technical Field
The invention relates to detection of structural damage, in particular to a passive knocking type material damage detection device and method.
Background
With the continuous progress of science and technology and the continuous increase of transportation demands, the number of various highways, bridges and other engineering structures is also continuously increasing. However, as various degrees of damage, such as cracks, pits, debonding and aging phenomena, may be caused by process reasons, the use load or other environmental factors during the manufacturing and using processes, and the damage is accumulated to a certain extent, the normal use of the structure is affected, and the life safety and property safety of people are seriously threatened.
Therefore, in order to ensure that the engineering structure can normally operate, damage detection is required before delivery and after a period of service. For example, a bridge forming test is required to be carried out before a bridge is communicated with a vehicle to ensure that the design requirement is met, and regular conventional detection or irregular special detection is required to be carried out in the service life so as to find the damage in the bridge in time. And aviation components such as wing skins can be delivered for use only if the damage in the components is less than a specified degree, and after the components are used for a period of time, the damage detection needs to be carried out on the components again to ensure the future flight safety.
At present, various damage detection methods for engineering structures and materials exist, for example, local detection methods for detecting damage by means of X-ray, infrared ray, ultrasonic wave, radar, magnetic eddy current and the like, and although such technologies have high damage detection accuracy for local areas, dead corners cannot be detected or the detection time is too long. For the overall detection technology that the sensor is arranged on the engineering structure to measure the static displacement, speed, acceleration and other responses of the engineering structure under the external excitation and the damage in the engineering structure is inverted, the damage inversion can be carried out only by using the structural response excited by the environmental excitation when the engineering structure works, and if the external excitation is not applied properly, the damage condition can not be fully reflected by the response of the engineering structure, so that the detection precision is influenced. Therefore, how to detect the damage in the engineering structure quickly and accurately without knowing the complete characteristic information of the engineering structure in advance is an urgent problem to be solved.
Disclosure of Invention
In view of the above, the present invention provides a passive slap-type material damage detection apparatus and method to overcome or at least partially solve the above problems.
According to one aspect of the invention, a passive knock-on material damage detection device is provided, comprising: the detection device comprises at least one wheel body, wherein the peripheral surface of the wheel body is provided with hard knocking teeth, and the knocking teeth are configured to knock the structural surface of a material to be detected along with the rotation of the wheel body; a sensor configured to sense a response signal transmitted to the sensor by a tapped area of the structure surface; a processor configured to determine an area where structural damage exists from the signals sensed by the sensor.
Optionally, the entire outer circumferential surface of the wheel body is uniformly provided with a plurality of the striking teeth.
Optionally, the outer circumferential surface of the wheel body is axially divided into a plurality of rings, each ring is uniformly provided with a plurality of the knocking teeth, and the intervals between the knocking teeth on each ring are different from the intervals between the knocking teeth on the other rings.
Optionally, the outer circumferential surface of the wheel body is divided into a plurality of sections, each section is uniformly provided with a plurality of the knocking teeth, and the intervals between the knocking teeth on each section are different from the intervals between the knocking teeth on the other sections.
Optionally, the driving speed of the material damage detection device, the number of the striking teeth and/or the tooth shape of the striking teeth cooperate to generate at least one preset excitation frequency.
Optionally, the running speed of the material damage detection device, the number of the striking teeth and/or the tooth shape of the striking teeth cooperate to generate a continuous specific frequency band.
Optionally, the striking teeth and the wheel body are integrally formed.
Optionally, the striking teeth are fixedly connected to the wheel body.
Optionally, the knocking teeth are connected with each other to form a knocking tooth cover tire, and the knocking tooth cover tire is sleeved on the wheel body.
Optionally, the sensor is arranged on a shaft for driving the wheel body to rotate.
Optionally, the processor is further configured to: carrying out conversion processing on the signals sensed by the sensors to obtain signal spectrograms of all areas on the surface of the structure; intercepting a spectrogram envelope line corresponding to a preset frequency of the knocking force from the signal spectrogram; calculating a damage indicating value of each region of the structure surface, wherein the damage indicating value reflects the similarity degree of the spectrogram envelope curve of the region and the spectrogram envelope curves of other regions; the region in which the damage indication value is abruptly changed is determined as a region in which structural damage is present.
According to an aspect of the present invention, there is also provided a passive knock-on material damage detection method applied to any one of the above passive knock-on material damage detection apparatuses, the method including: hard knocking teeth arranged on the peripheral surface of the wheel body knock against the structural surface of the material to be detected along with the rotation of the wheel body; the sensor senses a response signal transmitted to the sensor by a struck area of the structure surface; the processor determines an area where structural damage exists from the signals sensed by the sensor.
Optionally, the processor determines the region where the structural damage exists according to the signal sensed by the sensor, including: carrying out conversion processing on the signals sensed by the sensors to obtain signal spectrograms of all areas on the surface of the structure; intercepting a spectrogram envelope line corresponding to a preset frequency of the knocking force from the signal spectrogram; calculating a damage indicating value of each region of the structure surface, wherein the damage indicating value reflects the similarity degree of the spectrogram envelope curve of the region and the spectrogram envelope curves of other regions; the region in which the damage indication value is abruptly changed is determined as a region in which structural damage is present.
The invention provides a passive knocking type material damage detection device and a passive knocking type material damage detection method. The passive material damage detection device and method provided by the invention can efficiently complete damage detection on the material to be detected, and can simplify the test process while ensuring the accuracy of the test result. In addition, the material damage detection device provided by the invention does not need to be added with an independent knocking device, so that the overall structure of the detection device can be effectively simplified, the detection precision is further improved, and the detection result is more reliable.
The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.
Drawings
Some specific embodiments of the invention will be described in detail hereinafter, by way of illustration and not limitation, with reference to the accompanying drawings. The same reference numbers in the drawings identify the same or similar elements or components. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. In the drawings:
FIG. 1 is a schematic diagram of the operational principle of a passive knock-on material damage detection apparatus according to an embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view of a bridge, a hard road surface and a detection apparatus according to an embodiment of the invention;
FIG. 3 is a schematic diagram of an equivalent trolley-axle power interaction in accordance with an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a passive knock-on material damage detection apparatus according to an embodiment of the invention;
FIG. 5 is a schematic view of a wheel according to an embodiment of the present invention;
FIGS. 6A and 6B are schematic views of a wheel according to another embodiment of the present invention;
FIG. 7 is a functional block diagram of a passive knock-on material damage detection apparatus according to an embodiment of the invention;
FIG. 8 is a schematic diagram of a simulation test of a passive knock-on material damage detection apparatus according to an embodiment of the invention;
FIG. 9 is a power density map of an acceleration signal according to an embodiment of the present invention;
10A, 10B, 10C, 10D are schematic diagrams of the MAC coefficients before the bridge damage according to an embodiment of the invention;
11A, 11B, 11C, and 11D are schematic diagrams of the MAC coefficients after the bridge is damaged according to an embodiment of the invention;
12A, 12B, 12C, 12D are diagrams of MAC coefficients after noise filtering according to B value according to an embodiment of the invention;
FIG. 13 is a power density map of an acceleration signal according to another embodiment of the present invention;
FIGS. 14A and 14B are schematic views illustrating the detection result of a bridge damage according to another embodiment of the present invention;
FIGS. 15A and 15B are schematic views illustrating the detection result of a bridge damage according to another embodiment of the present invention;
FIG. 16 is a flow chart of a passive tap material damage detection method according to an embodiment of the invention;
17A, 17B, 17C are schematic diagrams of the detection results of placing a lesion at different positions on a beam according to the preferred embodiment of the present invention;
18A, 18B are schematic diagrams of the detection results of three lesions placed on a beam according to the preferred embodiment of the present invention; and
fig. 19A, 19B, 19C, and 19D are diagrams illustrating MAC coefficients after noise filtering according to a B value according to a preferred embodiment of the present invention.
Detailed Description
Before describing embodiments of the present invention in detail, the principles of the present invention are first explained with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of the working principle of a passive knock-type material damage detection apparatus according to an embodiment of the present invention. As shown in fig. 1, a simplified model is used to assist in understanding the theoretical basis of the passive knock-type material damage detection scheme proposed by the embodiment of the present invention. Taking the material to be detected as a bridge as an example, in the model, the passive knock-type material damage detection device is modeled to have kVThe sprung mass M of stiffness, also simulates the bridge as a two-dimensional simple beam of length L modeled as a planar Bernoulli-Euler (Bernoulli-Euler) beam with bending stiffness EI and mass M per unit length. The structural damage detection device is moved through the beam at a constant speed v. For the sake of simplicity and still maintaining the essence of the problem, other practical factors, such as damping and surface roughness, are temporarily omitted here. However, as shown in the numerical simulation results below, the proposed material damage detection scheme of the present invention is still effective even when these practical factors are taken into account.
In order to sensitively obtain the dynamic response of the damaged area of the material to be detected to the detection device, the problem of interaction between the material damage detection device and the material to be detected must be solved. According to the simplified model shown in fig. 1, the kinetic equations for the detection device and the beam (i.e., the material to be detected) can be described as:
wherein k represents the spring rate k of the detection devicevAnd hard road surface rigidity kpThe series equivalent stiffness therebetween, see fig. 2; y isb(x, t) and yv(t) displacement of the detector and the beam, respectively, measured from the static equilibrium position.
The interaction force between the detection device and the beam is as follows:
f(t)δ(x-vt)＝k(yv-yb|x＝vt)-Mg-F(t) (3)
where δ represents the dickla delta function, g represents the acceleration of gravity, and the instantaneous stiffness can be expressed as:
thus, the acceleration of the detection device may be utilized.
.., detecting damage to the beam. By using the superposition method, y in the equations 1 and 2 can be obtainedvAnalytic solution of (2):
wherein,
when the material to be detected is locally damaged, the global properties of the beam do not change much, that is, when the beam is locally damaged, the bending stiffness EI and the mass per unit length m of the beam hardly change, and the beam stiffness kbChanges occur along the length of the beam. Local injury pair k near injurybHas a great influence. Thus, it can be seen that the natural angular frequency ω of the detection meansvIs very sensitive to damage.
The sensitivity of the detection device to acceleration to damage can be expressed as:
wherein,
Suppose that
Relatively close to ωvDetecting acceleration ω of the devicevThe partial derivative of (d) can be expressed as:
the occurrence of damage can lead to omegavOf ω isvIs given in equation 14 as the coefficient of the corresponding frequency-dependent term.
When the material damage detection device is in a low-speed operation state, the coupling effect of the VBM system can be ignored. Thus, the model can be described with fig. 3.
The governing equation may be:
the analytical solution of the acceleration may be
Wherein,
when m is large, or the rigidity of the bridge is small:
based on equation 14, it can be obtained
On the basis of the above analysis solution, ω can be estimated by the equivalent checking means bridge dynamic interaction system shown in fig. 3vTo improve the sensitivity of the lesion detection.
Fig. 4 is a schematic structural diagram of a passive knock-on material damage detection apparatus 400 according to an embodiment of the invention, and as shown in fig. 4, the embodiment of the invention provides a passive knock-on material damage detection apparatus 400, which can detect damage to a material to be detected according to the above-described theory, where the material damage detection apparatus 400 may include at least one wheel 410 (two in this embodiment), a sensor 420, and a processor 430. Wherein, the outer circumferential surface of the wheel body 410 is provided with hard knocking teeth 411, and the knocking teeth 411 are configured to knock the structural surface of the material to be detected along with the rotation of the wheel body 410. The sensor 420 is used to sense a response signal transmitted to the sensor 420 from the knocked area of the structure surface, and the processor 430 is used to determine the area where the structure damage exists from the signal sensed by the sensor 420. The response signal transmitted to the sensor 420 may be an acceleration signal, a velocity signal, or a displacement signal, among others.
In the embodiment of the invention, the hard knocking teeth 411 arranged on the peripheral surface of the wheel body 410 can realize nondestructive detection on the surface of the material to be detected, so that a knocking device is not required to be arranged independently, the integral structure is simplified, the detection convenience, the detection efficiency and the detection precision can be effectively improved, and the detection result is more reliable.
The material damage detecting apparatus 400 shown in fig. 4 is self-balanced by providing two wheel bodies 410, and when the striking teeth 411 are provided on the outer circumferential surface of the wheel body 410, a plurality of striking teeth 411 may be uniformly provided on the entire outer circumferential surface of the wheel body 410, as shown in fig. 5. When the material damage detecting device 400 detects a material to be detected, the driving speed of the material to be detected on the surface is matched with the number of the knocking teeth 411 to generate a given excitation frequency. In practical applications, the number of the wheel bodies 410 and the intervals between the plurality of striking teeth 411 may be set according to different application scenarios, which is not limited in the present invention. Preferably, a plurality of predetermined excitation frequencies can also be generated simultaneously by providing different numbers of striking teeth in the axial direction of the same wheel body 410.
In a preferred embodiment of the present invention, the outer circumferential surface of the wheel body 410 may be divided into a plurality of rings along the axial direction, each ring is uniformly provided with a plurality of tapping teeth 411, and the intervals between the tapping teeth 411 on each ring are different from those between the tapping teeth 411 on the other rings. Fig. 6A shows a wheel body 410a according to another embodiment of the present invention, as shown in fig. 6A, the outer circumferential surface of the wheel body 410a may be divided into two rings, each of the two rings is uniformly provided with a plurality of tapping teeth 4111 and tapping teeth 4112, and the intervals of the tapping teeth 4111 are different from those of the tapping teeth 4112.
In another preferred embodiment of the present invention, the outer circumferential surface of the wheel body 410 is divided into a plurality of segments, each of the segments is uniformly provided with a plurality of tapping teeth 411, and the intervals between the tapping teeth 411 of each segment are different from the intervals between the tapping teeth 411 of the other segments. FIG. 6B shows a wheel body 410B according to another embodiment of the present invention, and as shown in FIG. 6B, the outer circumferential surface of the wheel body 410B may be divided into two segments, each of the two segments being uniformly provided with a plurality of tapping teeth 4113 and tapping teeth 4114, the spacing between the tapping teeth 4113 being different from the spacing between the tapping teeth 4114. The wheel body described in the above embodiments is only a schematic illustration of the possible implementation, and in practical applications, the number of rings along the axial direction of the outer circumferential surface of the wheel body or the number of segments of the outer circumferential surface of the wheel body may be set according to different test conditions, and the invention is not limited thereto. Based on the different arrangement modes of the wheel body 410 and the knocking teeth 411 in the above embodiments, the same wheel body can be provided with a plurality of knocking teeth 411 of different types, so as to expand the detection range of the material damage detection device 400 and improve the detection accuracy. For the conventional vibration exciter, it is difficult to generate a striking force of a constant magnitude simultaneously in a relatively wide frequency band, and based on the material damage detection device 410 provided in the above embodiment, by providing the striking teeth on the outer circumferential surface of the wheel body 410, when the wheel body 410 rotates to drive the material damage detection device 400 to run on the surface of the material to be detected, the striking teeth generate the striking force to perform damage detection on the material to be detected. The running speed of the material damage detection device 400 can be matched with the number of the knocking teeth 411 and/or the tooth shape of the knocking teeth 411 to generate a preset excitation frequency, and a plurality of preset excitation frequencies can be generated simultaneously by arranging different knocking teeth in the axial direction of the same wheel body 410, so that the test requirement of higher precision is met while the accuracy of the test result is ensured. Further, continuous frequency bands can be generated through the running speed of the material damage detection device 400, the number of the knocking teeth 411 and/or the tooth form matching of the knocking teeth 411, and the continuous frequency bands can be specifically set according to different test objects. That is to say, according to the material damage detection device 400 provided by the embodiment of the present invention, by controlling the driving speed of the material damage detection device 400 on the surface of the material to be detected, and by arranging different numbers of striking teeth 411 with different tooth shapes on the surface of the wheel body 410, not only can a plurality of discrete excitation frequencies be generated, but also a continuous frequency band can be realized, so as to meet different test requirements. The tooth form of the knocking tooth 411 may be a cylindrical gear, a bevel gear, a non-circular gear or a gear with other shapes, and may be set according to an actual test condition, which is not limited in the present invention.
When the wheel body 410 is manufactured, the knocking teeth 411 and the wheel body 410 may be integrally formed, or may be separately manufactured and then the knocking teeth 411 are fixedly connected to the wheel body 410. In addition, the striking teeth 411 may be connected to each other to form a striking-teeth cover tire, which is then directly fitted over the wheel body 410. Any one of the above modes can be adopted to efficiently realize the damage test of the material.
It was mentioned above that by providing the sensor 420 in the material damage detection device 400, the response signal transmitted to the sensor 420 by the knocked area of the structure surface is sensed. Generally speaking, the structural surface of the material to be detected will produce displacement, speed and acceleration under the effect of the knocking force correspondingly, and due to the interaction of the structural surface and the knocking teeth, these influences will be transmitted to the knocking teeth 411, and the magnitude of the instantaneous value thereof reflects the structural characteristics of the material to be detected at the knocking position, so that when damage occurs in the material to be detected, the displacement, speed or acceleration response transmitted from the structural surface of the material to be detected to the knocking teeth 411 at the position will be significantly different from the response without damage. The sensor 420 may be any sensor capable of sensing the response transmitted by the surface of the structure to be sensed to the strike tooth 411. For example, the sensor 420 may be any sensor capable of sensing one of the displacement, velocity, and acceleration responses transmitted to the strike tooth 411 by the surface of the structure to be detected. In order to accurately sense the response of the detected structure at the striking position of the striking tooth 411, the sensor 420 and the striking tooth 411 may be integrated or provided on a shaft for driving the wheel body 410 to rotate.
Further, when the sensor 420 senses the response signal, the processor 430 may determine the region where the structural damage exists according to the response signal sensed by the sensor 420. Preferably, when determining that there is a region of structural damage, the processor 430 may first perform transformation processing on the signal sensed by the sensor 420 to obtain a signal spectrogram of each region on the surface of the structure; intercepting a spectrogram envelope curve corresponding to the preset frequency of the knocking force from the signal spectrogram; calculating a damage indicating value of each region of the structure surface, wherein the damage indicating value reflects the similarity degree of the spectrogram envelope curve of the region and the spectrogram envelope curves of other regions; the region in which the damage indication value is abruptly changed is determined as a region in which structural damage is present. Preferably, as shown in fig. 7, the processor 430 may further include the following functional units: the device comprises a spectrogram acquisition unit 431, a spectrogram envelope intercepting unit 432, a damage indication value calculation unit 433 and a damage position determination unit 434, wherein the functional units work cooperatively to determine the structural damage area of the material to be detected according to the response signal sensed by the sensor 420.
According to the requirement of the detection precision, the surface of the structure to be detected can be divided into a plurality of portions with a certain size, and a certain time is required for the material damage detection device 400 to scan each surface portion, and the signal acquired by the sensor 420 is the sensor signal distribution in the time. Subsequently, the spectrogram-acquiring unit 431 performs transform processing on the distribution of the sensor signal over time to acquire a representation of the signal in the frequency domain or the scale domain. Such a transformation process may be performed using any of the transformation processes known in the art, for example, the transformation process may be a short-time fourier transform, a wavelet transform, or a Hilbert-Huang transform, etc. Thus, the spectrogram-acquiring unit 431 acquires a signal spectrum or a scale spectrum at each position portion of the structure surface.
A spectrum envelope extracting unit 432 extracts a spectrum envelope corresponding to the frequency of the striking force of the striking tooth from the signal spectrum. Since at least one frequency of the tapping force is close to at least one natural frequency of the structure to be detected, the spectrum envelope intercepted by spectrum envelope intercepting unit 432 should cover at least one natural frequency of the material to be detected. In the case where the tapping force has a certain frequency band, the captured envelope of the spectrogram has a frequency range corresponding to the frequency band of the tapping force. The examples given above regarding the frequency range of the truncated spectrogram envelope are merely exemplary. It will be understood by those skilled in the art that all frequency ranges are within the scope of the present invention as long as the frequency band of the intercepted spectrogram envelope corresponds to the tapping frequency of the tapping device and is suitable for use in subsequent data processing. Because only the spectrogram corresponding to the knocking frequency band is analyzed, the processing overhead required by processing the spectrograms of all the frequency bands can be reduced, and meanwhile, the detection precision is not influenced. In addition, because the frequency band of the environmental noise is generally different from the natural frequency of the detected structure, the frequency band is different from the knocking frequency of the knocking device, the influence of the environmental noise on the detection result can be obviously reduced, and the detection precision is improved.
The damage indication value calculation unit 433 calculates a damage indication value at each position of the surface of the structure to be detected based on the intercepted spectrogram envelope, the damage indication value reflecting the degree of similarity between the spectrogram envelope at the position and the spectrogram envelopes at other positions.
The damage indicator may be calculated in a number of ways, and according to one embodiment of the invention, the damage indicator may be calculated by first converting the spectrogram envelope into a spectrogram vector, which may be converted by obtaining amplitudes at a plurality of frequencies in the spectrogram envelope as components of the spectrogram vector. The number of components of the spectrogram vector can be determined according to the detection accuracy, the processing performance of the system and the like. The frequencies corresponding to the components may be uniformly distributed in the frequency band of the spectrogram envelope, or may be non-uniformly distributed. However, the frequency selection pattern at each location should be the same for the structure to be detected.
After the spectrogram vector at each position is generated, the damage indication value calculation unit 433 calculates a damage indication value reflecting the degree of similarity of the spectrogram vector at the current position and the spectrogram vectors at other positions. There are a number of ways to calculate the degree of similarity between two spectrogram vectors. According to one embodiment of the invention, the damage indication value may be calculated as:
the damage indicated value reflects the damage condition of the bridge, and the smaller the damage indicated value is, the more serious the bridge is damaged.
Wherein, the acceleration data of the detecting device passing through the material to be detected can be obtained through the frequency of the knocking force, and is divided into n parts, the corresponding spectrogram of each part is calculated and recorded as a vector Yi,i＝1,2,...,n。YiAnd YjRespectively representing the spectrogram vectors of the ith and jth parts on the structure of the material to be detected; inner product operation representing a spectrogram vector.
According to another aspect of the present invention, the MAC coefficient may be further used to obtain the damage indication value, and the calculation formula of the MAC coefficient matrix is:
each element in the MAC coefficient matrix represents the degree of similarity between two spectrogram vectors, where the element on the main diagonal must be equal to 1. The size of the ith row or ith column element of the MAC coefficient matrix can reflect the size of a certain spectrogram vector YiAnd thus the spectral vector YiThe damage indication value of the corresponding position.
The damage location determination unit 434 determines the damage location in the structure to be detected based on the damage indication value at each location of the surface of the structure to be detected. For example, the damage location determination unit 434 may determine a location where a sudden drop in the damage indication value occurs as a location where damage exists. Because if the structure is not damaged, the distribution of the damage indication values in the space is smoother; if the damage indication value at a certain position has a sudden change, it means that the local impedance at the position is obviously different from that at other positions, the damage is likely to occur, and the size of the sudden change reflects the severity of the damage. For example, the value of the first row element of the MAC coefficient matrix is taken as the vertical axis element, and the corresponding structure position is taken as the horizontal axis to draw a curve, and if the structure is not damaged, the curve should be relatively smooth; if the curve drops suddenly at a certain point, it indicates that there is a lesion, and the larger the magnitude of the drop, the more severe the lesion. According to an embodiment of the present invention, a location where an absolute value of a first derivative value of the curve exceeds a predetermined threshold may be determined as a location where the damage exists.
It should be noted that, in the processor of the material damage detection apparatus of the present invention, the components therein are logically divided according to the functions to be implemented, but the present invention is not limited thereto, and the respective components in the signal processing component may be newly divided or combined as needed, for example, some components may be combined into a single component, or some components may be further decomposed into more sub-components.
FIG. 8 showsA schematic diagram of a simulation test of a passive knocking type material damage detection device according to a preferred embodiment of the present invention is shown, in this embodiment, the material damage detection device is a self-balancing trolley 1 having two wheels, and a plurality of knocking teeth are uniformly arranged on the outer circumferential surface of each wheel. The material to be measured is simulation bridge 2 that is formed by aluminum plate, within 1.45m test range, and bridge 2 is through fixing on fixed knot constructs 3 (like the rod iron) to there is certain distance from the bottom surface, so that bridge 2 can simulate the bridge structure in reality well. The damage to the bridge 2 is shown in dotted lines at 4. When the trolley 1 runs on the bridge 2, the bridge 2 can be knocked at a specific frequency through knocking teeth on the wheel body. The running speed of the trolley 1 can be set according to different detection requirements. Wherein, still be provided with sensor and treater (all show in the figure) in the self-balancing dolly, the type of sensor is acceleration sensor, and the type is LC0101, and its frequency response range is 0.5 ~ 15000Hz, resonant frequency 40 Hz. The Poisson's ratio of the beam is 69GPa, and the density is about 2700kg/m3。
The number of striking teeth is determined by the sensitivity frequency, and the formula is as follows:
where v represents the speed of travel of the vehicle, r represents the radius of the wheel, f represents the sensitivity frequency, and n represents the number of hitting teeth.
Before the beam was tested for damage, the trolley was placed in the middle of the aluminum plate to generate a sweep band, and based on the above theoretical discussion, the sensitivity frequency of 1.45m was 48Hz, while 49Hz was used as the strike frequency in the experiment, FIG. 9 shows a power density profile of the acceleration signal according to an embodiment of the invention, and in addition, the cross-sectional stiffness of the entire beam was 9.66 × 104N·m2The damage is 3.26 × 104N·m2And accounts for 33.5%.
And converting the signals sensed by the sensors by a processor in the trolley to finally obtain a damaged area of the bridge, and calculating a damage indicated value. Fig. 10A, 10B, 10C, and 10D show results of a plurality of tests of the MAC coefficient before the bridge 2 is damaged. Fig. 11A, 11B, 11C, and 11D show results of a plurality of tests of the MAC coefficient after the bridge 2 is damaged. As is apparent from fig. 11A to 11D, the damage was provided at a position of 0.720 m. Therefore, the method provided by the embodiment of the invention can effectively detect the damage state of the bridge and has strong repeatability.
To clearly express the above test results, the background noise can be filtered by the following filter function:
where avg and std represent the mean and standard deviation of d (i, j), respectively, and B represents the noise interference level.
Fig. 12A, 12B, 12C, and 12D are schematic diagrams illustrating MAC coefficients after noise filtering according to B values, where the detection range is 1.45m, and the corresponding B values in fig. 12A, 12B, 12C, and 12D are: b-0, B-0.5, B-1 and B-1.5. As can be seen from the analysis, the larger B, the less the interference noise.
The feasibility of the material damage detection device provided by the embodiment of the invention is verified through tests performed by the above preferred embodiment. Other peaks seen in fig. 10A to 11D may be due to the surface roughness of the material to be measured, which may cause the acceleration of the cart to change suddenly. The roughness of the bridge surface may also introduce other frequencies, amplifying the trolley frequency amplitude, depending on the rigidity of the trolley wheel and the roughness of the bridge. Similarly, when the bridge has a plurality of damages, the method provided by the embodiment of the invention can accurately measure the positions of the damages of the bridge.
In another embodiment of the invention, bridge damage detection was also performed in the range of 1.75m, and prior to detection, the trolley was also placed in the middle of the simulated bridge to generate a sweep band, resulting in a sensitivity frequency of about 44Hz, as shown in FIG. 13. The damage detection results are shown in fig. 14A and 14B, and fig. 15A and 15B, respectively, and the position of the bridge damage can be known from the size of the MAC coefficient. In order to make the test results more clear, the positions of the piers within the range of 0 to 1.2m are omitted in fig. 14A to 15B. As can be seen from fig. 14A and 14B, the position at the center of the bridge had a damage, which was consistent with the damage set at the bridge in the experiment. Further, if two lesions are provided, the treatment can also be detected based on the above method, for example, fig. 15A, 15B can also see that there are two lesions at 0.5m and 0.9 m.
Furthermore, the material damage detection device provided by the embodiment of the invention has a simple structure, can be made of a material with a light material, can be made very small and is convenient to carry. The material damage detection device provided by the embodiment of the invention has a smaller structure size, so that the corner position can be detected. To sum up, this material damage detection device can guarantee high accuracy under the portable condition of being convenient for, need not have too much requirement to the detection object position simultaneously, can detect each corner. Such as field detection, corner detection, etc.
In addition, the nondestructive detection is carried out on the surface of the structure to be detected according to the theory of the knocking damage identification method, so that the material damage detection device is not limited by the material property of the detection object. The material damage detection device provided by the embodiment of the invention does not need to arrange instruments on the front surface and the back surface of the material to be detected at the same time during detection, and can detect damage of a detection object from one side.
Based on the same inventive concept, an embodiment of the present invention further provides a passive knock-on material damage detection method, which is applied to the passive knock-on material damage detection apparatus described in the above embodiment, as shown in fig. 16, the passive knock-on material damage detection method according to the embodiment of the present invention may include:
step S1602, knocking the structural surface of the material to be detected by hard knocking teeth arranged on the peripheral surface of the wheel body along with the rotation of the wheel body;
step S1604, the sensor senses a response signal transmitted to the sensor by the knocked area of the structure surface;
in step S1606, the processor determines the region where the structural damage exists according to the signal sensed by the sensor.
In the step S1604, a sensor in the material damage detecting device provided according to the embodiment of the invention is used to sense a response signal of the knocking tooth, and the sensed signal may be any response signal at the knocking position that can reflect the transmission from the structure surface of the material to be detected to the knocking tooth. For example, the signal sensed by the sensor may be displacement, velocity, or acceleration. Preferably, the signal sensed by the sensor is an acceleration signal, so that the detection result is more accurate.
As mentioned above at step S1606, the processor may determine the region where the structural damage exists from the signal sensed by the sensor. Preferably, it may be performed by:
step S1606-1, a signal sensed by the sensor is subjected to a transform process to acquire a signal spectrum at each position of the structure surface of the material to be detected. Depending on the requirements of the detection accuracy, the structured surface of the material to be detected needs to be divided into a plurality of portions. The signal sensed at each portion is the distribution of the time required for the material damage detection device to scan the portion, and thus the distribution of the signal in the time domain may be transformed to obtain a representation of the signal in the frequency domain or scale. Such a transformation process may be performed using any of the transformation processes known in the art, for example, the transformation process may be a short-time fourier transform, a wavelet transform, or a Hilbert-Huang transform, or the like.
And S1606-2, intercepting a part corresponding to the preset frequency of the knocking force of the knocking teeth from the signal spectrogram, and acquiring an envelope curve of the intercepted spectrogram. Since at least one frequency of the tapping force is close to at least one natural frequency of the structure to be detected, the intercepted envelope of the spectrum should cover at least one natural frequency of the structure to be detected. In the case where the tapping force has a certain frequency band, the captured envelope of the spectrogram has a frequency range corresponding to the frequency band of the tapping force. The examples given above regarding the frequency range of the truncated spectrogram envelope are merely exemplary. It will be understood by those skilled in the art that all frequency ranges are within the scope of the present invention as long as the frequency band of the intercepted spectrogram envelope corresponds to the tapping frequency of the tapping device and is suitable for use in subsequent data processing.
And S1606-3, calculating a damage indication value at each position of the surface of the structure to be detected according to the intercepted spectrogram envelope line, wherein the damage indication value reflects the similarity degree of the spectrogram envelope line at the position and spectrogram envelope lines at other positions. There are a number of ways to calculate the damage indicator value.
According to a preferred embodiment of the invention, the damage indication value may be calculated by:
step S1, the spectrogram envelope is converted into a spectrogram vector, which may be converted by acquiring amplitudes at a plurality of frequencies in the spectrogram envelope as components of the spectrogram vector. The number of components of the spectrogram vector can be determined according to the detection accuracy, the processing performance of the system and the like. The frequencies corresponding to the components may be uniformly distributed in the frequency band of the spectrogram envelope, or may be non-uniformly distributed. However, the frequency selection pattern at each location should be the same for the structure to be detected.
In step S2, after the spectrogram vector at each position is generated, a damage indication value that reflects the degree of similarity between the spectrogram vector at the current position and the spectrogram vectors at other positions is calculated. There are a number of ways to calculate the degree of similarity between two spectrogram vectors. According to one embodiment of the invention, the damage indication value may be calculated as:
wherein, the acceleration data of the detecting device passing through the material to be detected can be obtained through the frequency of the knocking force, and is divided into n parts, the corresponding spectrogram of each part is calculated and recorded as a vector Yi,i＝1,2,...,n。YiAnd YjRespectively representing the spectrogram vectors of the ith and jth parts on the structure of the material to be detected; inner product operation representing a spectrogram vector.
According to another aspect of the present invention, the MAC coefficient may be further used to obtain the damage indication value, and the calculation formula of the MAC coefficient matrix is:
each element in the MAC coefficient matrix represents the degree of similarity between two spectrogram vectors, where the element on the main diagonal must be equal to 1. The size of the ith row or ith column element of the MAC coefficient matrix can reflect the size of a certain spectrogram vector YiAnd thus the spectral vector YiThe damage indication value of the corresponding position.
Step S1606-4, after calculating the damage indication value for each position of the structure surface of the material to be detected, determines a damage position in the structure to be detected based on the damage indication value at each position of the structure surface. For example, a position where the damage indication value suddenly decreases may be determined as a position where damage is present. For example, the value of the first row element of the MAC coefficient matrix is taken as the vertical axis element, and the corresponding structure position is taken as the horizontal axis to draw a curve, and if the structure is not damaged, the curve should be relatively smooth; if the curve drops suddenly at a certain point, it indicates that there is a lesion, and the larger the magnitude of the drop, the more severe the lesion. According to an embodiment of the invention, a location where the absolute value of the first derivative value of the curve exceeds a predetermined threshold may be determined as a location where a lesion is present.
As previously described, the damage is actually equivalent to a change in section stiffness. Therefore, different section rigidity value tests can be adopted to detect the feasibility of the damage detection scheme. Based on the passive knock-on material damage detection method provided above, the preferred embodiment of the present invention further detects a bridge based on the material damage detection apparatus shown in fig. 7. In this embodiment, the material damage detection device still employs a double-wheel self-balancing trolley, and the material to be detected is a bridge. In practical application, a plurality of damages can be arranged at the bridge. Table 1 shows the original interface stiffness, the damaged section stiffness, the total section stiffness, and the damaged section stiffness as a percentage of the total section stiffness of the beam corresponding to each damaged item.
TABLE 1
| Item of |
1 | 2 | 3 |
| Original section stiffness/N.m of beam2 | 60174.35 | 60174.35 | 60174.35 |
| Damaged interfacial stiffness/N.m2 | 4795.16 | 12456.46 | 32382.56 |
| Total section stiffness | 64969.51 | 72630.80 | 96554.60 |
| Percentage of | 7.38 | 17.15 | 33.54 |
For items 1 and 2, the damage location was 0.6m from the car starting location, as shown in fig. 17A, 17B, respectively, while item 3 found damage at 0.7m from the starting location, as shown in fig. 17C. Fig. 18A and 18B show the results of two detections of three lesions placed on a bridge. As can be seen from fig. 18A and 18B, the first peak indicates the 1 st lesion, and the remaining two peaks indicate the 2 nd lesion, and the test results are consistent with the parameters set before the experiment was performed. It can be seen by analysis that the greater the percentage of total cross-sectional stiffness, the more pronounced the peaks in the graph. Therefore, even if different damages are placed at different positions of the bridge, the position of the damage on the bridge can still be accurately obtained by the material damage detection method provided by the embodiment of the invention.
Based on the detection theory presented above, the background noise can be filtered by the following filter function:
the degree of disturbance of the background noise reflected by B is mainly caused by the roughness of the road surface and the rigidity of the tires of the vehicle under test. The larger B, the less disturbing noise. The filtering function can be used to evaluate the bridge condition because the value of B is related to the level of defects other than noise. Small lesions can interfere with large lesions and therefore can be distinguished by B. Fig. 19A, 19B, 19C, and 19D respectively show schematic diagrams of MAC coefficients after noise filtering according to B values according to an embodiment of the present invention, where the corresponding B values in fig. 19A, 19B, 19C, and 19D are: b-0, B-0.5, B-1 and B-1.5. When bridge condition evaluation is performed, it is very important to test and classify damage of the bridge. Different degrees of damage can be reflected by the value of B.
The embodiment of the invention provides a passive knocking type material damage detection device and a passive knocking type material damage detection method. In the embodiment of the invention, the running speed of the material damage detection device on the surface of the material to be detected and the number of teeth of the wheel body are matched with each other to generate a given excitation frequency, and different numbers of knocking teeth with different tooth shapes are arranged in the axial direction of the same wheel body, so that not only can a plurality of discrete excitation frequencies be generated, but also a continuous frequency band can be realized, which is difficult to realize by a vibration exciter under the common condition. The passive material damage detection device and method provided by the embodiment of the invention can efficiently complete damage detection on the material to be detected, not only can ensure the accuracy of the test result and simplify the test process, but also can effectively simplify the overall structure of the detection device without additionally adding a knocking device, further improve the detection precision and ensure that the detection result is more reliable.
Furthermore, the passive knock-type material damage detection device provided by the embodiment of the invention belongs to a miniature material damage detection device which is small in size and convenient to carry, is high in test precision and is not limited by the direction of a detected object.
Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.
Claims (13)
1. A passive knock-on material damage detection device, comprising:
the detection device comprises at least one wheel body, wherein the peripheral surface of the wheel body is provided with hard knocking teeth, and the knocking teeth are configured to knock the structural surface of a material to be detected along with the rotation of the wheel body;
a sensor configured to sense a response signal transmitted to the sensor by a tapped area of the structure surface;
a processor configured to determine from the signals sensed by the sensor that an area of structural damage exists;
wherein the number of striking teeth is determined by the following formula:
where v represents the travel speed of the material damage detection device, r represents the radius of the wheel body, f represents the sensitivity frequency, and n represents the number of striking teeth.
2. The passive knock-on material damage detection device according to claim 1, wherein the entire outer circumferential surface of the wheel body is uniformly provided with the plurality of knock teeth.
3. The passive knocking type material damage detecting device according to claim 1, wherein the outer peripheral surface of the wheel body is axially divided into a plurality of rings, each ring is uniformly provided with a plurality of the knocking teeth, and the interval between the knocking teeth on each ring is different from the interval between the knocking teeth on the other rings.
4. The passive knock-on material damage detection device according to claim 1, wherein the peripheral surface of the wheel body is divided into a plurality of segments, each of the segments is uniformly provided with a plurality of the knock-on teeth, and the interval between the knock-on teeth on each of the segments is different from the interval between the knock-on teeth on the other segments.
5. A passive slamming material damage detection device according to any of claims 1-4, wherein the traveling speed of the material damage detection device, the number of the slapping teeth and/or the tooth shape of the slapping teeth cooperate to generate at least one preset excitation frequency.
6. A passive percussive material damage detection device according to any of claims 1-4, characterised in that the travel speed of the material damage detection device, the number of the percussive teeth and/or the tooth shape of the percussive teeth cooperate to produce a continuous frequency band.
7. A passive percussive material damage detection device as claimed in any of claims 1 to 4, wherein the percussive teeth and the wheel body are integrally formed.
8. A passive percussive material damage detection device as claimed in any one of claims 1 to 4, wherein the percussive teeth are fixedly attached to the wheel body.
9. The passive percussive material damage detection device according to any one of claims 1-4, wherein the percussive teeth are interconnected to form a percussive tooth cover, which is sleeved over the wheel body.
10. A passive percussive material damage detection device as claimed in any of claims 1 to 4, wherein the sensor is integrated into the percussive tooth or is provided on a shaft for driving rotation of the wheel.
11. The passive percussive material damage detection device as set forth in any of claims 1-4, wherein the processor is further configured to:
carrying out conversion processing on the signals sensed by the sensors to obtain signal spectrograms of all areas on the surface of the structure;
intercepting a spectrogram envelope line corresponding to a preset frequency of the knocking force from the signal spectrogram;
calculating a damage indicating value of each region of the structure surface, wherein the damage indicating value reflects the similarity degree of the spectrogram envelope curve of the region and the spectrogram envelope curves of other regions;
the region in which the damage indication value is abruptly changed is determined as a region in which structural damage is present.
12. A passive knock-on material damage detection method applied to the passive knock-on material damage detection apparatus of any one of claims 1 to 11, the method comprising:
hard knocking teeth arranged on the peripheral surface of the wheel body knock against the structural surface of the material to be detected along with the rotation of the wheel body;
the sensor senses a response signal transmitted to the sensor by a struck area of the structure surface;
the processor determines an area where structural damage exists according to the signals sensed by the sensors;
wherein the number of striking teeth is determined by the following formula:
where v represents the travel speed of the material damage detection device, r represents the radius of the wheel body, f represents the sensitivity frequency, and n represents the number of striking teeth.
13. The method of passive plexor material damage detection according to claim 12, wherein the processor determines from the signals sensed by the sensors that areas of structural damage exist, including:
carrying out conversion processing on the signals sensed by the sensors to obtain signal spectrograms of all areas on the surface of the structure;
intercepting a spectrogram envelope line corresponding to a preset frequency of the knocking force from the signal spectrogram;
calculating a damage indicating value of each region of the structure surface, wherein the damage indicating value reflects the similarity degree of the spectrogram envelope curve of the region and the spectrogram envelope curves of other regions;
the region in which the damage indication value is abruptly changed is determined as a region in which structural damage is present.
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